Glossary

Three-Dimensional High Efficiency Video Coding

3D-HEVC is an advanced video compression standard for stereoscopic and multi-view video content, enabling efficient transmission of 3D video over mobile networks. It extends HEVC with specialized coding tools for depth maps and multiple viewpoints, reducing bandwidth requirements while maintaining high visual quality for immersive media services.

3D Gaussian Splatting

3D Gaussian Splatting (3DGS) is a real-time radiance field rendering technique using 3D Gaussians. Studied in 3GPP Rel-19 under TS 26.956 for immersive media and extended reality services.

Three Degrees of Freedom

3DOF refers to a basic level of spatial audio and visual immersion in media services, typically supporting head rotation (yaw, pitch, roll) without positional tracking. It enables initial immersive experiences like 360-degree video and basic VR applications within 3GPP media delivery frameworks, providing a foundation for more advanced XR services.

3G Packet Switched Multimedia Terminal

A terminal that uses IETF SIP/SDP standards adapted by 3GPP to deliver multimedia telephony over packet-switched networks. It enables voice, video, and messaging services over IP-based 3G and later networks.

3G-324M Terminal

A terminal based on ITU-T H.324 recommendation, adapted by 3GPP for circuit-switched video telephony over 3G networks. It enables real-time video calls and multimedia services on legacy CS networks.

3GPP File Format

3GP is a multimedia container format standardized by 3GPP for storing and delivering audio, video, and timed text over mobile networks. It is based on the ISO Base Media File Format (ISOBMFF) and is optimized for efficient transmission and playback on resource-constrained mobile devices. The format supports various codecs including H.263, H.264, AMR, and AAC, enabling multimedia services in 3GPP systems.

3GPP Dynamic Adaptive Streaming over HTTP

3GP-DASH is a standardized HTTP-based adaptive bitrate streaming protocol for delivering media over 3GPP networks. It enables seamless video playback by dynamically adjusting the quality of media segments based on network conditions and device capabilities. This is crucial for delivering high-quality video services like VoD and live streaming on mobile devices.

Third Party Call Control

A service capability that allows a third-party application server to establish, manage, and terminate multimedia sessions between two or more endpoints. It enables network operators and service providers to offer value-added services like click-to-dial, conferencing, and call transfer without requiring endpoint intelligence.

Three-Party Communication

3PTY enables a mobile user to establish a three-party call by adding a third party to an existing two-party call, creating a multi-party communication session. This service is essential for business conferencing, family calls, and collaborative discussions, providing flexible communication capabilities within cellular networks.

5G Enhanced Positioning Area

A subset of the 5G positioning service area equipped with additional infrastructure or specific positioning technologies to deliver enhanced positioning accuracy and performance beyond baseline 5G positioning capabilities.

5G Positioning Service Area

A service area where positioning services rely solely on infrastructure and technologies assumed to be present wherever 5G is available, such as GNSS, sensors, and standard cellular measurements.

5G Proximity Services Direct Communication

A 5G ProSe function enabling direct user-plane communication between two or more nearby 5G ProSe-enabled UEs using NR technology, without traversing any network node. It provides device-to-device connectivity for public safety, commercial, and industrial use cases.

5G Proximity Services Direct Discovery

A 5G ProSe-enabled UE procedure to discover other ProSe-enabled UEs in its vicinity using direct NR radio transmissions, enabling device-to-device (D2D) communication without traversing the core network.

5G Proximity Services Remote User Equipment

A 5G ProSe-enabled UE that communicates with a Data Network indirectly through one or more 5G ProSe Intermediate UE-to-Network Relays and a 5G ProSe UE-to-Network Relay, enabling coverage extension and group communication.

5G Proximity Services User Equipment-to-Network Relay

A 5G ProSe-enabled UE that provides connectivity to the network for 5G ProSe Remote UEs, acting as a relay between remote devices and the 5G core network to extend coverage and enable group communication.

5G Proximity Services User Equipment-to-User Equipment Relay

A function employed by a 5G ProSe-enabled UE to support communications between two 5G ProSe end UEs, enabling direct device-to-device relay for coverage extension and group communication.

5G Proximity Services-enabled User Equipment

A UE that supports 5G ProSe requirements and associated procedures, enabling direct device-to-device communication and discovery via the 5G network.

5G Wireless Sensing

A 5GS feature that uses NR radio frequency signals to gather information about the environment and objects, such as shape, size, orientation, speed, location, and motion.

5G Broadband Residential Gateway

A 5G residential gateway that provides fixed wireless access (FWA) to homes and small offices using 5G NR. It acts as a bridge between the 5G network and local Wi-Fi/Ethernet, enabling high-speed broadband without fiber or cable. This supports 5G's fixed-mobile convergence and expands service reach.

5G Residential Gateway

A customer premises equipment (CPE) device that connects residential or small office networks to 5G networks, replacing traditional fixed broadband access. It provides local network connectivity (Wi-Fi, Ethernet) while using 5G as the backhaul, enabling flexible broadband deployment without physical cables. This supports Fixed Wireless Access (FWA) services and convergence between mobile and fixed networks.

5G Virtual Network

5G-VN is a 3GPP service enabling enterprises to create isolated, customizable virtual networks over public 5G infrastructure. It provides dedicated connectivity with specific QoS, security policies, and network functions for private use cases like factories, campuses, or IoT deployments. This matters because it allows enterprises to leverage carrier-grade 5G without building their own physical networks.

5G Automotive Association

5GAA is an industry association, not a 3GPP technical specification. It drives the development and deployment of connected vehicle solutions using 5G, C-V2X, and related technologies. Its work influences 3GPP standardization by defining use cases and requirements for automotive communications.

5G Media Streaming

5GMS is a 3GPP framework for delivering media streaming services over 5G networks. It defines standardized interfaces and functions for content preparation, delivery, and consumption, enabling efficient, high-quality media experiences. It matters because it provides a consistent, carrier-grade media delivery platform that leverages 5G's low latency and high bandwidth.

5G Media Streaming Architecture

5GMSA is a standardized architecture for delivering media streaming services over 5G networks. It defines functional entities and interfaces to enable efficient, scalable, and quality-adaptive streaming of audio and video content. This architecture is crucial for supporting high-quality media experiences like 4K/8K video, AR/VR, and live broadcasting in a 5G ecosystem.

5G Multicast-Broadcast Services

5MBS is a 3GPP service enabling efficient delivery of the same content to multiple users simultaneously, using 5G network resources. It optimizes bandwidth usage for applications like live video, public safety alerts, and software updates, supporting both multicast (group-based) and broadcast (area-based) delivery. This is crucial for scalable, high-quality media distribution and IoT communications in 5G.

Six Degrees of Freedom

6DOF refers to the ability to track movement and orientation in three-dimensional space with six independent variables: three for position (X, Y, Z) and three for rotation (roll, pitch, yaw). In 3GPP, it's crucial for immersive media services like extended reality (XR), enabling realistic user interaction and spatial audio/video rendering in 5G networks.

6G Artificial Intelligence Service

A service provided by the 6G network where AI functionalities such as model training, management, or inference are made available to subscribers or authorized applications on UEs or application servers.

6G Computing Service

A 6G service that leverages computing resources in the Service Hosting Environment, offered to subscribers via UE or third parties. It enables on-demand compute offload and edge processing within the 6G system.

Application layer - Analytical Data Repository Function

The A-ADRF is an application-layer function in 3GPP that provides a standardized repository for storing and managing analytical data. It enables data sharing and consumption for network analytics, AI/ML model training, and service optimization across the 5G system and beyond. Its introduction supports the growing need for data-driven automation and intelligence in mobile networks.

Application - Digital Asset Container Management

A-DACM defines a framework for managing digital assets within application containers in 3GPP networks. It enables secure, lifecycle-aware handling of digital assets such as tokens, credentials, and data objects, supporting emerging service paradigms in Rel-19.

Assisted - Galileo and Additional Navigation Satellite Systems

A-GANSS is a 3GPP standard for providing mobile devices with assistance data to improve positioning performance using Galileo and other global navigation satellite systems (GNSS) beyond GPS. It enables faster, more accurate, and energy-efficient location fixes by delivering satellite ephemeris, almanac, and timing data over the cellular network. This is critical for location-based services, emergency caller location (E911/E112), and applications requiring precise positioning.

Assisted Global Navigation Satellite Systems

A-GNSS is a network-assisted positioning technology that enhances the speed and accuracy of location fixes for mobile devices. It provides satellite assistance data (e.g., ephemeris, almanac) over cellular networks to reduce Time to First Fix (TTFF) and improve sensitivity in challenging environments like urban canyons or indoors. This service is critical for emergency calls (E911/E112), location-based services, and regulatory compliance.

Assisted Global Positioning System

A-GPS is a network-assisted positioning technology that enhances GPS performance in mobile devices by providing assistance data from the network. It significantly reduces Time to First Fix (TTFF), improves location accuracy, and extends battery life by offloading complex calculations. This enables reliable location-based services in challenging environments like urban canyons or indoors.

Application to Person

A2P (Application to Person) refers to machine-initiated communications directed to human users, typically for service notifications, alerts, or interactive messaging. It enables applications, services, or network functions to send messages, calls, or data sessions to end-user devices. This is crucial for automated services, IoT notifications, and enterprise communications in 5G networks.

Application-to-Everything communication

A2X communication supports advanced applications like platooning and extended sensors by leveraging PC5 sidelink for direct vehicle-to-everything interactions. It enables low-latency, high-reliability exchanges among vehicles and infrastructure.

Aircraft-to-Everything Policy

A2XP is a policy framework for managing communication services for aircraft, including Air-to-Ground (A2G) and Air-to-Air (A2A) scenarios. It defines how network policies are applied to ensure secure, reliable, and QoS-appropriate connectivity for aircraft systems and passengers. This is critical for enabling advanced aviation services like real-time telemetry, passenger connectivity, and operational communications within 5G networks.

Advanced Audio Coding

Advanced Audio Coding (AAC) is a standardized, lossy audio compression codec defined by 3GPP for high-quality digital audio services. It provides superior sound quality at lower bitrates compared to older codecs like MP3, enabling efficient delivery of music, speech, and multimedia content over mobile networks. AAC is a foundational technology for streaming services, broadcast, and multimedia messaging in 3GPP systems.

Advanced Audio Coding – Enhanced Low Delay

AAC-ELD is a low-latency audio codec standardized by 3GPP for real-time communication services. It combines the high compression efficiency of AAC-LD with spectral band replication (SBR) to deliver CD-quality audio with minimal delay, making it essential for voice and video calls, gaming, and live streaming over mobile networks.

Advanced Audio Coding-Low Complexity

AAC-LC is a standardized, low-complexity audio object type within the MPEG-4 Advanced Audio Coding (AAC) family, specified by 3GPP for mobile multimedia services. It provides high-quality audio compression with efficient computational requirements, making it suitable for resource-constrained mobile devices and networks. Its inclusion enables high-fidelity audio streaming and download services like music and video over cellular networks.

Advanced Audio Coding – Low Delay

AAC-LD is a low-delay audio codec standardized by 3GPP for real-time communication services. It provides high-quality stereo audio with an algorithmic delay of only 20 ms, enabling natural, interactive conversations. It is crucial for VoLTE, ViLTE, and other latency-sensitive multimedia services in mobile networks.

Advanced Audio Coding Long Term Predictor Object Type

AAC-LTP is a specific object type (profile) within the Advanced Audio Coding (AAC) family standardized by 3GPP for mobile communications. It incorporates a Long Term Predictor (LTP) tool to enhance the compression efficiency and audio quality for speech and general audio signals, particularly in error-prone wireless environments. It matters as it provides a high-quality, bandwidth-efficient audio codec option for services like voice calls, streaming, and multimedia messaging in 3GPP networks.

Application Based Charging

Application Based Charging (ABC) is a 3GPP charging mechanism that enables operators to apply specific charging policies based on the application being used, rather than just network resource consumption. It allows for differentiated billing for services like streaming, gaming, or social media, enabling new business models and service plans. This granular charging capability is crucial for monetizing diverse data services in modern mobile networks.

Adaptive Bit Rate

ABR is a streaming media delivery technique where the source content is encoded at multiple bit rates and segmented into small chunks. The client player dynamically selects the appropriate bit rate segment based on real-time network conditions and device capabilities. This ensures smooth playback with minimal buffering by adapting video quality to available bandwidth.

Application Client

The Application Client (AC) is a logical entity residing on a User Equipment (UE) or an external device that executes a specific application service. It interfaces with the 3GPP network to utilize network capabilities and deliver services to the end-user. Its role is central to enabling value-added services beyond basic connectivity.

Access Leg

The call control leg between the UE and the SCC AS in IMS Centralized Services and Voice Call Continuity architectures. It represents the access-specific portion of a session, enabling service continuity across CS and PS domains.

Application specific Congestion control for Data Communication

ACDC is a network-based congestion control mechanism that allows operators to manage access attempts for specific applications during network congestion. It prevents non-priority applications from overloading the network by applying selective barring, ensuring critical services remain accessible. This is crucial for maintaining service quality and network stability during peak loads or emergencies.

Algebraic Code-Excited Linear Prediction

ACELP is a speech coding algorithm used in 3GPP standards for efficient voice compression. It provides high-quality speech at low bit rates by modeling the vocal tract and using algebraic codebooks for excitation signals. This technology is crucial for optimizing bandwidth usage in mobile voice services.

Ambisonics Channel Number

ACN is a standardized channel ordering scheme for Ambisonics audio formats within 3GPP. It defines a specific sequence for transmitting spherical harmonic components, enabling consistent decoding and rendering of immersive spatial audio across different devices and networks. This ensures interoperability for services like VR, AR, and 360-degree video.

Anonymous Communications Rejection

ACR is a supplementary service in 3GPP networks that allows a user to automatically reject incoming calls or sessions from parties who have hidden their calling line identity (CLI). It protects user privacy by preventing unwanted contact from anonymous or withheld numbers, ensuring the called party can control who can reach them.

Application Context Transfer

ACT is a 3GPP service enabling seamless transfer of application session context between user devices and network functions. It maintains service continuity when users switch devices or access networks by preserving application state, session data, and user preferences. This is crucial for uninterrupted user experience in multi-device and mobility scenarios.

Active Communication

A state in which a UE has an established connection, such as a CS connection or one or more activated PDP contexts for PS. It indicates that the UE is actively engaged in communication services.

Application Data Analytics Enablement

ADAE is a 3GPP service capability enabling application layer data analytics by exposing network data and events to authorized Application Functions (AFs). It standardizes how applications can request and receive analytics for service optimization and new use cases, bridging the gap between network intelligence and application logic.

Application Data Analytics Enablement Client

The Application Data Analytics Enablement Client (ADAEC) is a functional entity introduced in 3GPP Release 18 that resides in the User Equipment (UE). Its primary role is to facilitate the collection, processing, and reporting of application-layer data and analytics to the network's Application Data Analytics Enablement Server (ADAES). This enables network operators and application providers to gain insights into application performance, user experience, and service quality, supporting data-driven optimization and new service capabilities.

Application Data Analytics Enablement Services

ADAES is a 3GPP framework enabling network exposure of analytics for applications. It allows Application Functions (AFs) to request and receive data analytics from the network, facilitating smarter application behavior and optimization. This service is crucial for leveraging network intelligence to enhance user experience and enable new service capabilities.

Adaptive Codebook

The adaptive codebook is a key component of speech codecs like AMR that stores excitation vectors adapted per subframe from the long-term filter state. It enables efficient pitch prediction and high-quality speech synthesis at low bit rates.

Adaptive Postfilter

The adaptive postfilter is a signal processing component in speech codecs that enhances the perceptual quality of reconstructed speech. It is applied after the short-term synthesis filter and typically consists of a formant postfilter and a tilt compensation filter.

Application Detection and Control

ADC is a network function that identifies specific applications or traffic types and applies policy-based controls. It enables operators to manage network resources, implement charging policies, and ensure quality of service for different applications. This is crucial for traffic optimization, service differentiation, and monetization in mobile networks.

Add-on Charge

An add-on charge is an additional charge applied on top of the current tariff, which can be metered in non-monetary units (e.g., meter pulse) or monetary units (e.g., currency). It enables flexible charging for supplementary services or events.

Abbreviated Dialling Numbers

ADN is a telecommunication service feature that allows users to store frequently dialed phone numbers with shorter, memorable codes. It simplifies dialing by replacing long numbers with short numeric sequences, improving user convenience and reducing dialing errors in mobile networks.

Associated Delivery Procedures

Associated Delivery Procedures (ADP) are a set of standardized mechanisms in 3GPP networks for the reliable and coordinated delivery of multimedia content, such as multimedia messages, to user equipment. It ensures content is delivered in a managed way, often in association with other network events or user interactions, and is crucial for services like MMS. Its standardization enables interoperability and consistent service behavior across different network implementations.

Adaptive Differential Pulse Coded Modulation

ADPCM is a speech coding algorithm used in 3GPP networks for efficient voice transmission. It compresses voice signals by encoding differences between consecutive samples rather than absolute values, adapting quantization steps based on signal characteristics. This provides good voice quality at lower bit rates, conserving network bandwidth while maintaining acceptable speech intelligibility.

Associated Delivery Procedure Description

ADPD is a structured description used in 3GPP's Multimedia Broadcast/Multicast Service (MBMS) to define the delivery procedure for associated content. It specifies how auxiliary data, like subtitles or metadata, is synchronized and delivered alongside primary media streams. This ensures a cohesive and enriched user experience for broadcast and multicast services.

Application Data Unit

ADU is a fundamental data encapsulation unit for multimedia applications in 3GPP networks, representing a complete, independently decodable piece of application-layer data. It serves as the basic payload container for streaming and download services, enabling efficient content delivery and synchronization between application and transport layers. Its standardized structure is crucial for ensuring interoperability and predictable behavior across diverse network conditions and device capabilities.

Advanced Emergency Alert

AEA is a 3GPP standardized system for delivering critical public warnings to mobile devices during emergencies. It enables authorities to broadcast geographically targeted alerts with multimedia content, ensuring rapid and reliable dissemination of life-saving information to affected populations.

Advanced Emergency Alert Table

AEAT is a structured data table defined in 3GPP for broadcasting enhanced emergency alerts to mobile devices. It enables rich multimedia alerts with precise geographic targeting, supporting public warning systems like ETWS and CMAS. This standardized format ensures interoperability across networks and devices during critical situations.

Acoustical Echo Cancellation

AEC is a signal processing technique that removes echo caused by acoustic coupling between a loudspeaker and microphone in communication devices. It is essential for ensuring clear voice quality in telephony and voice-over-IP services by preventing users from hearing their own delayed speech, which significantly improves the user experience and call intelligibility.

API Exposing Function

The API Exposing Function (AEF) is a network function that securely exposes 3GPP network capabilities and services to authorized third-party Application Providers. It acts as a gateway, translating between external API requests and internal network protocols. This enables innovation by allowing external applications to leverage network features like QoS, location, and authentication.

Application Entity Invocation

AEI is a CAMEL (Customised Applications for Mobile network Enhanced Logic) service capability enabling the dynamic invocation of external application logic during a call or session. It allows network operators to integrate custom services, such as prepaid charging or intelligent routing, by triggering an external Application Entity (AE) based on specific detection points in the call state model.

Application Function / Application Server

AF/AS is a network function that provides application-specific services and interacts with the 5G core network to influence traffic routing and policy decisions. It enables third-party applications to integrate with network capabilities like QoS control and network exposure. This allows for optimized application performance and new service-aware network features.

Affinity Group

A set of service locations intended to be deployed together and not with members of other affinity groups. It guides edge application server discovery and placement in 5G media streaming and edge computing.

Adaptive Multi-Rate Full Rate Speech

AFS is a speech codec mode within the Adaptive Multi-Rate (AMR) family, operating at the full rate channel (22.8 kbit/s) in GSM/EDGE networks. It dynamically adjusts its bit rate and error protection based on radio conditions to optimize voice quality and network capacity. This adaptation is crucial for maintaining consistent call quality under varying signal strengths and interference levels.

Adaptive multirate Halfrate Speech

AHS is a speech codec mode that dynamically switches between half-rate and full-rate channel coding to optimize voice capacity and quality. It enables more efficient use of radio resources by adapting to network conditions, allowing operators to serve more voice users within the same spectrum. This technology was crucial for GSM network optimization before the widespread adoption of 3G/4G voice services.

Artificial Intelligence Agent

An automated intelligent entity that pursues a specific goal on behalf of another entity by interacting with its environment, reasoning, learning, and executing tasks. It is central to 3GPP's vision of autonomous network operations and AI-driven services.

Artificial Intelligence / Machine Learning Model

A set of parameters, including model data and associated metadata, required by an AI/ML inference engine to execute a task. It is the fundamental artifact that enables AI-driven features across RAN, core, and services in 3GPP networks.

Application Information Table

The Application Information Table (AIT) is a standardized data structure defined by 3GPP for managing and delivering application-related information over broadcast networks. It provides a mechanism for signaling application metadata, enabling receivers to discover, launch, and interact with applications associated with broadcast content. This is crucial for enabling interactive and enhanced broadcast services, such as those used in public warning systems, mobile TV, and automotive infotainment.

Asynchronous JavaScript and XML

AJAX is a web development technique enabling asynchronous data exchange between client browsers and servers without full page reloads. In 3GPP, it's standardized for creating responsive web applications in mobile networks, improving user experience by reducing latency and network overhead.

Application Layer

AL refers to the Application Layer in the 3GPP service architecture, which hosts end-user services and applications. It is a conceptual layer above the core network where value-added services like multimedia streaming, messaging, and IoT applications reside and interact with the underlying transport capabilities. Its definition ensures standardized service enablers and interfaces for consistent application behavior across networks.

Application Layer Forward Error Correction

AL-FEC is a 3GPP standardized error correction mechanism applied at the application layer to protect media delivery over unreliable networks. It enables robust multimedia streaming by reconstructing lost packets without retransmissions, crucial for real-time services like MBMS and streaming. This technology significantly improves quality of experience in challenging network conditions.

Application Layer - Service Data Unit

The Application Layer - Service Data Unit (AL-SDU) is the data unit exchanged between the application layer and the underlying transport layer in IMS-based multimedia services. It represents the complete application data payload before segmentation or after reassembly, ensuring proper service delivery and quality of experience for multimedia applications like voice and video over IP.

Asynchronous Layered Coding

Asynchronous Layered Coding is a reliable multicast transport protocol for multimedia broadcast/multicast services (MBMS). It enables efficient content delivery to multiple users simultaneously by using layered coding and asynchronous transmission techniques. This is crucial for scalable broadcast services like mobile TV and software updates.

Alert Service Centre

A service element in GSM/UMTS/EPS/5GS networks that notifies a Service Centre when a previously unreachable mobile station or user equipment has recovered operation, enabling retry of failed short message deliveries.

Adaptive Multi-Rate

AMR is a speech codec family standardized by 3GPP for GSM, UMTS, and LTE networks. It dynamically adapts bit rate based on channel conditions to optimize voice quality and network capacity. This is crucial for efficient spectrum usage and robust voice services across mobile generations.

Adaptive Multi-Rate Narrowband

AMR-NB is a speech codec standard for narrowband voice services in 3GPP networks, operating at 8 kHz sampling with bit rates from 4.75 to 12.2 kbps. It dynamically adapts speech coding rates based on channel conditions to maintain voice quality while optimizing bandwidth usage. This codec became fundamental for GSM, UMTS, and LTE voice services, providing robust performance across varying network conditions.

Adaptive Multi-Rate Noise Suppressor

AMR-NS is a noise suppression algorithm integrated into the Adaptive Multi-Rate (AMR) speech codec to improve voice quality in noisy environments. It processes the speech signal to reduce background noise, enhancing intelligibility and listener comfort during mobile calls. This is crucial for maintaining acceptable voice service quality across diverse and challenging acoustic conditions encountered in mobile networks.

Adaptive Multi-Rate Wideband Speech Codec

AMR-WB is a wideband speech codec standardized by 3GPP that provides superior voice quality compared to narrowband codecs. It operates at sampling rates of 16 kHz, covering frequencies from 50 Hz to 7 kHz, delivering more natural and intelligible speech. This codec is essential for high-quality voice services in mobile networks and is widely used in VoLTE, VoNR, and other voice-over-IP applications.

Access Network Bitrate Recommendation Query

A mechanism in IMS-based media services where the UE queries the access network for recommended bitrates. It enables adaptive media streaming by allowing the UE to request bitrate recommendations based on current network conditions, optimizing quality of experience.

anti-sparseness processing

An adaptive post-processing procedure applied to the fixed codebook vector in speech codecs to reduce perceptual artifacts caused by sparse codebook vectors. It improves the quality of synthesized speech in 3GPP codecs like AMR and EVS.

Advice Of Charge

Advice Of Charge (AOC) is a 3GPP service that provides real-time charging information to users during a communication session. It enables users to monitor usage costs before, during, and after calls or data sessions, promoting transparency and control over expenses. This is crucial for both prepaid and postpaid subscribers to avoid bill shock and manage budgets effectively.

Advice of Charge Service

A combination of basic and supplementary services with charging parameters, defining a customized service for providing real-time charging information to users. It enables subscribers to be informed of incurred charges before or during service usage.

Advice Of Charge - Charging

AOC-C is a 3GPP charging service that provides real-time charging information to users during voice calls and data sessions. It enables operators to offer transparent billing by notifying users of accumulated charges, helping prevent bill shock and improving customer satisfaction through predictable cost management.

Advice Of Charge - During the communication

AOC-D is a 3GPP service that provides real-time charging information to a user during an active communication session, such as a voice call or data session. It enables users to monitor accrued charges in real-time, enhancing transparency and control over service usage. This is crucial for prepaid and postpaid billing models, helping to prevent bill shock and manage spending.

Advice Of Charge - at the End of the communication

AOC-E is a 3GPP charging service that provides users with detailed cost information after communication sessions complete. It enables accurate post-session billing by collecting charging data from network elements and presenting it to subscribers. This service enhances billing transparency and helps users manage their communication expenses effectively.

Advice Of Charge - Information

AOC-I is a 3GPP charging service that provides real-time charging information to users during active sessions. It enables subscribers to monitor their usage costs for voice calls, data sessions, and messaging services before charges are applied. This transparency helps users manage their spending and avoid bill shock.

Advice Of Charge at communication Set-up time

AOC-S is a 3GPP charging service that provides users with cost information at call or session establishment. It enables subscribers to receive estimated charging details before accepting communication charges, supporting transparent billing and cost control. This service is particularly valuable for roaming scenarios and premium services where users need upfront cost awareness.

Add-On Charging Information

AOCRG is a 3GPP charging mechanism that enables operators to apply additional, context-specific charges beyond basic service fees. It allows dynamic pricing based on service usage patterns, content type, or network conditions. This flexible charging model supports complex business models and personalized service offerings.

Application Originated Mobile Terminated

AOMT enables applications to initiate communication sessions to mobile devices without requiring the device to first establish a connection. It allows network-initiated service delivery to UE in power-saving states, supporting IoT and push-based services. This is crucial for enabling efficient, network-triggered communications in 5G systems.

Acoustic Overload Point

AOP is a key audio performance metric defined in 3GPP for voice and audio services. It specifies the maximum sound pressure level a device's microphone can handle before distortion occurs, ensuring consistent audio quality across different user equipment. This parameter is crucial for maintaining reliable voice communication quality in mobile networks.

API Publishing Function

The API Publishing Function (APF) is a 3GPP network function that securely exposes standardized northbound APIs to authorized third-party Application Functions (AFs). It acts as a controlled gateway, enabling service exposure and network capability consumption for vertical industries and enterprise applications within 5G and beyond.

Application Data

Information or data specific to an application other than the MMS User Agent or VASP, transported without alteration by MMS. It can be of any content type and format, enabling rich multimedia messaging.

Address Presentation Restriction Indicator

APRI is a signaling parameter used in the IP Multimedia Subsystem (IMS) to control the visibility of a caller's address information (e.g., SIP URI, TEL URI) to the called party. It enables privacy services by allowing the network or the originating user to restrict whether the calling party's address is presented, withheld, or presented only with authorization. This is a fundamental privacy mechanism in IMS-based telephony and multimedia services.

Average Peak Signal-to-Noise Ratio

APSNR is a video quality metric standardized by 3GPP for evaluating the perceptual quality of encoded video streams. It provides an objective, quantitative measure of video fidelity by averaging the PSNR values across video frames or sequences. This metric is crucial for network operators and service providers to assess video delivery performance and ensure Quality of Experience (QoE) for multimedia services.

Augmented Reality

A service that overlays digital information (graphics, sound, haptics) onto the user's real-world view in real-time. In 3GPP, it is a key use case driving requirements for high data rates, ultra-low latency, and precise positioning. It enables applications from interactive navigation to immersive gaming and remote assistance.

Application Server

A network element that hosts and executes value-added service logic, such as voice/video calling, messaging, or location-based services. It interfaces with the core network to provide services to users, enabling operators to offer differentiated applications beyond basic connectivity.

Application Server Incoming Leg Control Model

AS-ILCM is a control model in the CAMEL architecture where the Application Server (AS) controls the incoming leg of a call. It enables service logic to manage how incoming calls are processed, allowing for intelligent call routing, screening, and service triggering based on subscriber profiles and network conditions.

Application Server Outgoing Leg Control Model

A service control model in the IP Multimedia Subsystem (IMS) where the Application Server (AS) controls the outgoing leg of a session. It enables advanced services like call forwarding, number translation, and call screening by allowing the AS to modify or reroute the session request.

Application Satellite Coverage Availability Information

ASCAI is a 3GPP service enabling terrestrial networks to query and receive real-time satellite coverage availability information for specific geographic areas. It allows applications to make intelligent decisions about service delivery, such as routing traffic via satellite when terrestrial coverage is poor or unavailable. This enhances service continuity and reliability, particularly in remote or underserved regions.

Advanced Speech Call Items

ASCI is a 3GPP feature set for advanced group and priority voice services in GSM/UMTS networks. It includes Voice Group Call Service (VGCS), Voice Broadcast Service (VBS), and enhanced Multi-Level Precedence and Preemption (eMLPP). These services enable mission-critical communications for public safety, transportation, and industrial applications.

Application Service Element

ASE is a standardized component within the 3GPP CAMEL architecture that provides intelligent network services for mobile subscribers. It enables network operators to offer value-added services like prepaid billing, VPNs, and location-based services by interacting with the core network during call/session processing. Its standardized interface allows consistent service deployment across multi-vendor networks.

Active Speech Level

ASL is a standardized metric for measuring the average power level of active speech segments in audio signals. It is crucial for ensuring consistent speech quality and loudness in telecommunications, particularly for voice over NR (VoNR) and voice over LTE (VoLTE) services.

Application Service Provider

An entity that provides application services to users over 3GPP networks, enabling third-party service integration and value-added offerings. It plays a crucial role in the service delivery ecosystem by hosting applications, managing service logic, and interfacing with network capabilities through standardized APIs.

Automatic Speech Recognition

Automatic Speech Recognition (ASR) is a network service that converts spoken language into text. It enables voice-controlled services, automated call handling, and accessibility features within 3GPP networks. This technology is fundamental for interactive voice response systems and voice-based user interfaces.

Air-To-Ground

A communication service providing broadband connectivity from ground-based networks to aircraft in flight. It enables in-flight connectivity (IFC) for passengers and operational data links for airlines, using dedicated spectrum and adapted ground stations. It transforms aircraft into connected nodes within the mobile network.

Automatic Train Operation

Automatic Train Operation (ATO) is a 3GPP service enabling driverless train operation over 5G networks. It provides precise train positioning, real-time control, and safety-critical communications for autonomous rail systems. This technology is essential for improving railway efficiency, safety, and capacity in future transportation networks.

Air Traffic Service

ATS is a 3GPP service enabling cellular networks to support air traffic management communications. It provides reliable, secure connectivity for aircraft, ground stations, and air traffic controllers. This is crucial for modernizing aviation communications and supporting future air mobility.

Access Traffic Steering, Switching, and Splitting

ATSSS is a 3GPP framework enabling simultaneous use of multiple access networks (3GPP and non-3GPP) for a single PDU session. It intelligently steers, switches, and splits traffic across available paths to optimize performance, reliability, and user experience. This is crucial for 5G multi-access convergence and service continuity.

Access Traffic Steering, Switching and Splitting - Low-Layer

ATSSS-LL is a 3GPP feature enabling intelligent, low-layer (L2/L3) multi-access traffic management for a PDU Session. It allows dynamic steering, switching, and splitting of user data flows across 3GPP (e.g., 5G NR) and non-3GPP (e.g., Wi-Fi) access networks based on real-time link conditions and policies. This enhances user experience by improving throughput, reliability, and seamless mobility.

Attachment (to CTS-FP)

The procedure by which a Cordless Telephony System Mobile Station attaches to a specific CTS Fixed Part, enabling calls via that fixed part after proper initialization.

AMR-TFO Version Number

ATVN is a parameter that identifies the version of the AMR Tandem Free Operation (TFO) protocol used between transcoders in a mobile network. It ensures compatibility between different network elements during voice calls, allowing proper negotiation of TFO capabilities to maintain voice quality while avoiding unnecessary transcoding.

Asynchronous Time Warping

Asynchronous Time Warping (ATW) is a 3GPP media synchronization technique for Extended Reality (XR) applications. It compensates for motion-to-photon latency by warping rendered frames based on updated head/device pose data, reducing perceived latency and improving visual quality. This is critical for immersive XR experiences where low latency directly impacts user comfort and realism.

Automatic Commencement Mode

A mode in which the initiation of a private call does not require any action on the part of the receiving MCPTT user. It enables immediate call setup without the callee needing to accept, commonly used in push-to-talk services.

Advanced Video Coding

A video compression standard, also known as H.264 or MPEG-4 Part 10, standardized by 3GPP for efficient video transmission over mobile networks. It enables high-quality video services like mobile TV, video calling, and streaming by reducing bandwidth requirements while maintaining visual fidelity.

Audio-Video Profile with Feedback

AVPF is a Real-time Transport Protocol (RTP) profile that enhances multimedia communication by adding feedback mechanisms for audio and video streams. It enables receivers to send quality reports back to senders, allowing for adaptive bitrate adjustment, error recovery, and improved Quality of Experience (QoS) in real-time applications like VoLTE, ViLTE, and conferencing.

B party

The user receiving a call (unless the call is forwarded). In telecommunications, the B party is the called party, as opposed to the A party (calling party). This term is used in 3GPP specifications for call-related services.

B Subscriber (Called Party)

The B subscriber is the mobile subscriber originally called by the A subscriber in a 3GPP circuit-switched or IP multimedia telephony scenario. The term distinguishes the called party from the calling party in service descriptions, charging, routing, and supplementary service logic.

Back-to-Back User Agent

A SIP-based network element that acts as both a User Agent Client (UAC) and User Agent Server (UAS) to mediate between two SIP sessions. It terminates and reoriginates SIP signaling, enabling service logic execution, protocol interworking, and session control without requiring end-to-end transparency. This architecture is fundamental for implementing advanced telephony services in IMS and VoIP networks.

Barring of All Incoming Calls

BAIC is a supplementary service that allows a mobile subscriber to bar all incoming calls. It provides users with control over their call reception, enabling them to avoid disturbances and manage privacy. This service is essential for user-centric telecommunication features.

Barring of All Outgoing Calls

BAOC is a supplementary service in 3GPP networks that allows a subscriber to bar all outgoing calls from their mobile device. It is a user-controlled service that prevents the initiation of voice calls, providing a tool for managing call permissions and costs. This service is a fundamental part of the GSM/UMTS/LTE supplementary service framework for call control.

Base Avatar Repository

The Base Avatar Repository (BAR) is a network function introduced in 3GPP Release 14 to store and manage digital avatars for users. It enables consistent avatar representation across different services and applications, supporting immersive communication experiences like AR/VR. It is a foundational component for avatar-based services in 5G and beyond.

Broadcast Auxiliary Service

A service enabling broadcast content providers to use 5G networks for backhaul and contribution links. It provides reliable, high-quality transport for live audio/video feeds from remote locations to broadcast studios, replacing traditional satellite and microwave links with cellular connectivity.

Baseline capabilities

The minimum set of capabilities a service-less terminal (UE) must have to operate within a network, including cell search, synchronization, registration with authentication, and capability negotiation. It ensures basic connectivity without any specific service.

Basic service

A bearer or teleservice that forms the fundamental telecommunication service offering, excluding supplementary services. In SIP-based networks, it is identified via the Session Description Protocol (SDP).

Basic telecommunication service

A common reference term encompassing both bearer services and teleservices, representing the fundamental telecommunication services offered to users. Defined in 3GPP specifications 21.905 and 22.105.

Bearer Capability 1

BC1 is a parameter in call control signaling that indicates the preferred bearer service for a circuit-switched connection. It is used during call setup to specify the type of bearer (e.g., speech, data) the user equipment requests, ensuring the network allocates appropriate resources. This parameter is crucial for service differentiation and backward compatibility in GSM and UMTS networks.

Binary Coded Signalling

BCS is a phase of facsimile (fax) transmission defined by ITU-T T.30, enabling digital signalling for call control and capabilities negotiation. In 3GPP, it is adapted for circuit-switched fax services over mobile networks, ensuring reliable fax communication by managing the establishment, negotiation, and teardown of fax calls.

Barred Dialling Number

Barred Dialling Number (BDN) is a subscriber-level service feature in 3GPP networks that restricts outgoing calls to specific phone numbers. It is managed via the USIM application and enforced by the mobile device, providing a user-controlled or network-provisioned mechanism to prevent unauthorized or costly calls. This feature is crucial for controlling service usage and preventing fraud.

Background Data Transfer

Background Data Transfer (BDT) is a 5G service enabling efficient, scheduled data transmission for non-time-critical applications. It optimizes network resource utilization by allowing operators to manage when and how background traffic occurs, reducing congestion during peak hours. This is essential for IoT devices, software updates, and other applications where immediate delivery isn't required.

Bearer capability

A transmission function that the user equipment requests from the network, defining the characteristics of a bearer service such as data rate, delay, and reliability. It is a fundamental concept in 3GPP bearer management and QoS negotiation.

Bad Frame Handling

Bad Frame Handling (BFH) is a 3GPP mechanism for managing corrupted or lost speech frames in voice services. It ensures voice call continuity and intelligibility by concealing or reconstructing damaged frames, crucial for maintaining Quality of Service (QoS) under poor radio conditions.

Binary Format for Scenes

BIFS is a binary scene description format standardized by 3GPP for representing multimedia presentations in mobile environments. It enables efficient transmission and rendering of rich media content including 2D/3D graphics, audio, and video with interactive capabilities. It matters because it provides a compact, bandwidth-efficient alternative to text-based formats for delivering complex multimedia services over mobile networks.

Billing

The functions whereby charging data are transformed into bills requiring payment. It encompasses the processes of generating invoices, handling pre-paid deductions, and delivering charges to users.

Broadcast-Multicast Service Centre

The BM-SC is the core network entity responsible for managing and delivering Multimedia Broadcast Multicast Service (MBMS) content. It handles service announcement, session scheduling, security, and content synchronization across the network. This enables efficient one-to-many data distribution for applications like mobile TV, software updates, and emergency alerts.

Based Media File Format

BMFF is a file format standard for storing and delivering multimedia content in 3GPP systems. It provides a structured container for audio, video, and timed text, enabling efficient streaming and progressive download. Its importance lies in enabling high-quality media services over mobile networks with proper synchronization and metadata support.

LTE-based 5G Broadcast over Geosynchronous Satellite

BOG stands for LTE-based 5G Broadcast over Geosynchronous Satellite. It enables broadcast/multicast services via satellite using LTE technology, extending 5G broadcast coverage to remote areas.

Barring of Outgoing International Calls

BOIC is a supplementary service in GSM/UMTS/LTE/5G networks that allows subscribers or operators to prevent the placement of outgoing international calls. It provides a mechanism for controlling call costs, enforcing service plans, and preventing fraud by restricting dialing to foreign destinations.

Barring of Outgoing InterZonal Calls

BOIZC is a supplementary service that allows network operators to restrict subscribers from making outgoing calls to destinations outside their designated geographical zone. It enables zone-based call control for billing, regulatory compliance, and service management purposes within mobile networks.

Bitstream Partition

Bitstream Partition (BP) is a 3GPP mechanism for dividing media content into multiple independent partitions that can be delivered separately over the network. It enables flexible media delivery by allowing different partitions to be transmitted via different paths or with different QoS characteristics, supporting applications like multi-stream video and adaptive bitrate streaming.

Body Proximity Sensing

Body Proximity Sensing (BPS) is a 3GPP feature enabling a UE to detect its proximity to the human body. It allows the UE to adjust its radio frequency (RF) transmission power to comply with regulatory Specific Absorption Rate (SAR) limits, ensuring user safety while maintaining connectivity. This is crucial for wearable devices and smartphones to manage RF exposure without degrading network performance.

Bad Quality Call

BQC is a key performance indicator (KPI) that measures the percentage of calls terminated due to poor quality. It helps operators identify network issues affecting user experience by tracking calls that fail quality thresholds. This metric is crucial for maintaining service quality and optimizing network performance.

Broadcast Remote Identification

BRID is a 3GPP service enabling Uncrewed Aerial Systems (UAS) to broadcast identification and location information for safety and regulatory compliance. It allows authorized entities to remotely identify drones in flight, supporting airspace management and security. This is crucial for integrating drones into national airspace systems.

Binaural Room Impulse Response

BRIR is a spatial audio representation that captures how sound propagates from a source to both ears in a specific acoustic environment. It models head-related transfer functions (HRTF) and room reflections to create immersive 3D audio experiences. This technology enables realistic audio rendering for extended reality (XR) applications in 5G networks.

Broadcast (communication configuration)

A service attribute value denoting unidirectional distribution of information to all users simultaneously. It is a fundamental communication paradigm in 3GPP networks, enabling efficient one-to-many delivery for services like emergency alerts, television, and software updates.

Broadcast call

A term used synonymously with 'voice broadcast call', referring to a unidirectional voice communication to multiple recipients. It is defined in 3GPP specifications for voice group call services, enabling efficient one-to-many voice delivery.

Broadcast MBS session

An MBS session to deliver the broadcast communication service, characterized by the content to send and the geographical area where to distribute it. It enables efficient point-to-multipoint transmission of broadcast content over 5G networks.

Basic Service Group

A logical grouping of basic telecommunication services defined in 3GPP standards for service management and charging purposes. It enables operators to categorize and manage fundamental communication capabilities like voice calls, SMS, and data sessions as cohesive service packages for billing and policy control.

Basic Safety Message

The Basic Safety Message (BSM) is a standardized V2X message format defined by 3GPP for direct vehicle-to-vehicle and vehicle-to-infrastructure communication. It provides essential real-time vehicle state information, including position, speed, heading, and acceleration, enabling critical safety applications like collision avoidance and hazard warnings. BSM is a foundational element for Cellular-V2X (C-V2X) services, supporting both LTE-V2X (PC5) and NR-V2X sidelink communication modes.

Broadcast Service User

The Broadcast Service User (BSU) is a logical entity representing a user or device that consumes broadcast/multicast services in 3GPP networks. It is a key concept in the Multimedia Broadcast Multicast Service (MBMS) architecture, defining the endpoint for content delivery. This abstraction is crucial for service management, charging, and quality of service enforcement for broadcast traffic.

Business Trunking

Business Trunking (BT) is a 3GPP standardized service that enables enterprises to replace traditional PBX systems with cloud-based telephony over mobile networks. It provides enterprise-grade voice, video, and messaging services to mobile users, integrating seamlessly with corporate directories and call features. This matters as it allows businesses to unify fixed and mobile communications, reduce infrastructure costs, and offer flexible work arrangements.

Background Data Transfer Answer

BTA is a Diameter application command defined in 3GPP for the Sd interface. It is the answer message from the Traffic Detection Function (TDF) to the Policy and Charging Rules Function (PCRF) in response to a Background Data Transfer Request (BTR). It is used to acknowledge and confirm the application of policies for background data transfer detection and control.

Background Data Transfer Request

BTR is a 3GPP mechanism enabling background data transfers for non-real-time applications like software updates and content synchronization. It allows the network to schedule data delivery during periods of low congestion, optimizing resource utilization and improving user experience by minimizing foreground service disruption.

Beyond Visual Line of Sight

BVLOS (Beyond Visual Line of Sight) is a service enabling unmanned aerial vehicles (UAVs) or drones to operate outside the pilot's direct visual observation, using 3GPP networks for command, control, and communication. It is crucial for commercial drone applications like delivery, inspection, and surveillance, requiring reliable, secure, and wide-area connectivity. This service leverages 5G's low latency, high reliability, and network slicing to support autonomous and remote UAV operations.

BandWidth Extension

BandWidth Extension (BWE) is a 3GPP feature introduced in Release 18 to enhance audio quality in voice and multimedia services by extending the audio bandwidth beyond traditional narrowband limits. It enables higher fidelity audio transmission, improving user experience for calls, conferencing, and streaming. BWE is specified in 3GPP TS 26.253 as part of the Enhanced Voice Services (EVS) codec framework.

C subscriber

The final recipient of a forwarded call in mobile networks. When a B subscriber forwards calls, the C subscriber is the destination, which can be a fixed or mobile line.

Control and Command

C2 (Control and Command) is a 3GPP service enabling remote control and management of unmanned aerial vehicles (UAVs) and other automated systems over 5G networks. It provides reliable, low-latency communication for mission-critical operations, ensuring safe and efficient UAV integration into national airspace. This is crucial for applications like drone delivery, surveillance, and infrastructure inspection.

Common Active Codec Set

CACS is a 3GPP-defined mechanism for managing and negotiating the set of speech codecs available for use during a call between networks. It enables efficient codec selection by allowing networks to exchange their supported codec lists and agree on a common subset, ensuring interoperability and optimal voice quality across different operator domains.

Complex Activity Detection

Complex Activity Detection (CAD) is a 3GPP service capability that enables the network to detect and recognize complex user activities and behaviors through analysis of network signaling and user equipment data. It provides context-aware services by identifying patterns in user interactions, device usage, and mobility behaviors, enabling personalized network optimizations and value-added services.

Content-Aware Encoding

CAE is a 3GPP Rel-19 media delivery technique that adapts encoding based on content semantics to optimize quality and bandwidth. It enables more efficient streaming and immersive media experiences over 5G networks.

Closed Access Group

A Closed Access Group (CAG) is a 5G feature enabling restricted network access for authorized users, such as enterprise employees, within a specific location like a campus or factory. It ensures only subscribed UEs can connect to designated CAG cells, providing secure, private connectivity. This supports enterprise and industrial use cases requiring controlled, isolated network environments.

Call

A call is the execution of actions to establish, maintain, and release a communication between two or more parties based on a required service. It encompasses both the signaling and the actual communication, characterized by bearer and service-level attributes.

Call Related

Call Related refers to any Location Services (LCS) operation associated with an established call in the CS domain or a session via an active PDP context in the PS domain. It is used to classify location requests that are tied to an ongoing communication.

Called-party pre-emption

Termination of a call to a particular user when a higher priority call is directed towards that specific user. It is decided by the Mobile Station and, for point-to-point calls, is performed by Call Waiting with automatic acceptance of the waiting call.

Calling service subscriber

Service subscriber which originates the VGCS call. This term identifies the user who initiates a Voice Group Call Service (VGCS) call, distinguishing them from other participants in the group call.

Calling subscriber

Service subscriber or dispatcher which originates the VGCS call (Rel-4), later redefined as the service subscriber which invokes the eMLPP service (Rel-5 onwards). This term identifies the originator of a call in the context of priority services.

Calling user (Broadcast Call Control entity)

The Broadcast Call Control (BCC) entity in a Mobile Station that initiates or has initiated a broadcast call. It is a key identifier in GSM/UMTS broadcast call services, distinguishing the originator of a group call from other participants.

Cooperative Awareness Message

A periodic broadcast message used in Vehicle-to-Everything (V2X) communication to share a vehicle's dynamic state (position, speed, heading) and basic attributes with nearby road users. It enables cooperative awareness for collision avoidance and traffic efficiency applications in 3GPP-based Cellular-V2X (C-V2X).

Customised Applications for Mobile network Enhanced Logic

CAMEL is a 3GPP standard for intelligent network (IN) services in GSM, UMTS, and LTE. It enables real-time, operator-defined services like prepaid charging, number translation, and call control for roaming subscribers. It is crucial for deploying custom, value-added services across multi-vendor networks.

Customized Alerting Tone content provider

A service provider that supplies a set of Alerting Tones for use as Customized Alerting Tones (CAT) for subscribers of the CAT service. A 3GPP operator may itself act as a CAT content provider.

Communication Barring

Communication Barring (CB) is a network service that allows users or operators to restrict specific types of communication attempts, such as outgoing or incoming calls and SMS. It provides selective control over communication sessions based on subscriber preferences or network policies, enhancing privacy and resource management.

Channel-Based Audio

Channel-Based Audio (CBA) is a 3GPP standardized audio format for immersive, multi-channel sound delivery over mobile networks. It enables high-quality spatial audio experiences by encoding audio as discrete channels (e.g., 5.1, 7.1) rather than object-based metadata. This matters for delivering cinema-grade, broadcast, and live event audio to mobile devices, enhancing media consumption.

Cell Broadcast Channel

CBCH is a point-to-multipoint unidirectional channel in GSM/UMTS networks for broadcasting short messages to all mobile devices in a specific geographical area, known as a cell. It enables mass alerting services like public warnings, traffic information, and location-based advertising without network congestion.

Cell Broadcast Entity

The Cell Broadcast Entity (CBE) is a network element responsible for originating and managing Cell Broadcast Service (CBS) messages. It interfaces with the Cell Broadcast Center (CBC) to deliver public warning messages, location-based services, and commercial information to all mobile devices in specific geographical areas. This capability is critical for emergency alert systems and mass notification services.

Cell Broadcast Message Identifier

CBMI is a unique identifier used to distinguish individual Cell Broadcast Service (CBS) messages within a 3GPP network. It enables the network to manage, schedule, and deliver broadcast messages, such as public warnings or commercial alerts, to all UEs in a specific geographical area. This identifier is crucial for ensuring reliable, non-interfering mass message delivery.

CBR Packet transmission

CBR Packet transmission is a service feature defined in 3GPP TS 26.937 for the Multimedia Broadcast/Multicast Service (MBMS). It enables the transmission of Constant Bit Rate (CBR) media packets over MBMS bearers, ensuring predictable data delivery for streaming applications. This is crucial for providing reliable broadcast and multicast services like mobile TV.

Cell Broadcast Service

A point-to-multipoint service that broadcasts short messages to all mobile devices in a specific geographical area (cell). It's used for public warning systems, location-based alerts, and emergency notifications without network congestion. This enables simultaneous delivery to thousands of devices.

Composite Capability / Preference Profiles

CC/PP is a framework for describing device capabilities and user preferences using RDF. It enables content adaptation and service personalization in mobile networks by allowing servers to understand client characteristics. This is crucial for delivering optimized multimedia content across diverse devices and network conditions.

Critical Communications Application

A standardized application framework enabling mission-critical voice, video, and data services over 3GPP networks. It provides the functional architecture and interfaces for critical communications, supporting professional mobile radio (PMR) capabilities like TETRA replacement. This enables public safety and industrial organizations to leverage commercial LTE/5G networks for reliable, secure critical communications.

Completion of Communications to Busy Subscriber

CCBS is a supplementary service that allows a calling party to request automatic completion of a call when a previously busy called subscriber becomes available. It eliminates the need for repeated manual redialing, improving user convenience and network efficiency by managing call completion requests within the network infrastructure.

Call Continuity Control Function

The Call Continuity Control Function (CCCF) is a network element introduced in 3GPP Release 7 to manage the handover of voice calls between Circuit-Switched (CS) and IP Multimedia Subsystem (IMS) domains. It ensures seamless call continuity for services like Voice Call Continuity (VCC), enabling users to switch between cellular and Wi-Fi networks without dropping the call. This function is critical for delivering consistent voice service quality in converged networks.

Conference Call Device

A Conference Call Device (CCD) is a functional entity defined in 3GPP for managing multiparty conference calls within the IP Multimedia Subsystem (IMS). It provides the control logic and media handling capabilities required to establish, maintain, and terminate multimedia conferences involving multiple participants. Its standardization ensures consistent and interoperable conferencing services across different network operators and user equipment.

Completion of Communications on Not Logged In

CCNL is a 3GPP service that allows a user to receive and complete incoming communications (like calls or messages) even when their device is not logged into the IMS network. It ensures service continuity by temporarily registering the user for the duration of the incoming session, addressing scenarios where the user is in a power-saving state or has deregistered.

Completion of Communication sessions on No Reply

CCNR is a supplementary service that allows a calling party to request completion of a communication session when the called party is busy or doesn't answer. It enables automatic call setup when the called party becomes available, improving communication efficiency and user experience in mobile networks.

Converged Charging System

The Converged Charging System (CCS) is a 3GPP standardized online charging system that unifies charging for all network services. It enables real-time charging control, policy enforcement, and balance management across voice, data, messaging, and IMS services. This centralization is crucial for modern, flexible service offerings and revenue assurance.

Call Completion Service Set-up

CCSS is a 3GPP service feature enabling enhanced call completion mechanisms for circuit-switched calls, primarily Call Waiting (CW) and Completion of Communications to Busy Subscriber (CCBS). It allows a calling party to be notified when a busy called party becomes available or to be alerted of an incoming second call while engaged. This improves user experience and network efficiency by reducing missed connections.

Communication Deflection

A supplementary service that allows a called party to redirect an incoming communication (e.g., a call) to another destination, such as voicemail or another number, based on criteria like busy condition or no reply. It is a foundational feature for call management in circuit-switched and IMS networks.

Communication DIVersion

A suite of supplementary services allowing a user to divert incoming communication sessions (calls, messages) based on configurable rules. It enables flexible call handling, improving user availability and network efficiency by redirecting sessions to alternative destinations like voicemail or other numbers.

Communication Diversion Session Identifier Uniform Resource Identifier

A URI created and inserted by a diverting Application Server (AS) to identify a communication diversion session. It ensures that the diverted session is routed through the same AS, enabling consistent service handling.

Content Delivery Network / Content Distribution Network

A distributed network of servers that delivers web content and media to users based on geographic proximity. It reduces latency, offloads traffic from origin servers, and improves quality of experience for bandwidth-intensive services like video streaming and software downloads.

Charging Data Record

A structured data record generated by network functions to capture resource usage for billing and accounting. It is the fundamental unit for offline charging, detailing service consumption, duration, data volume, and subscriber identity to enable accurate invoicing.

Content Distribution Service

A 3GPP service framework for efficient content delivery over mobile networks. It enables optimized distribution of multimedia content like video, audio, and applications to users by leveraging caching, content adaptation, and network-aware delivery mechanisms. This reduces network congestion and improves user experience.

Chargeable DURation

CDUR is a charging parameter in 3GPP networks that represents the duration of a chargeable event, such as a voice call or data session. It is a fundamental unit for billing calculations, enabling operators to apply time-based tariffs. Its accurate measurement is critical for generating correct call detail records (CDRs) and ensuring fair billing.

Code Excited Linear Prediction

CELP is a speech coding algorithm standardized by 3GPP for voice services in mobile networks. It provides high-quality, low-bitrate speech compression by modeling the human vocal tract and using a codebook of excitation signals. This technology is fundamental for efficient voice transmission over digital cellular systems like UMTS and LTE.

Common Encryption

CENC is a standardized encryption and key management scheme for protecting media content in 3GPP systems. It enables secure delivery of multimedia services like MBMS and streaming by providing a common framework for content protection across different delivery methods. This ensures content providers can securely distribute media while maintaining interoperability.

Conversion Facility

The Conversion Facility enables interworking between Teletext (Ttx) and Telex (Tx) services in 3GPP networks. It translates protocols and formats to allow legacy text communication services to function within modern mobile networks. This ensures backward compatibility and service continuity for specialized text-based applications.

Call Forwarding on mobile subscriber Busy

CFB is a supplementary service that redirects incoming calls to another number when the called mobile subscriber is busy. It ensures callers can reach an alternative destination instead of receiving a busy signal, improving communication efficiency and user experience in mobile networks.

Communication session Forwarding on No Logged-in

CFNL is a supplementary service that forwards incoming communication sessions when a user's device is not logged into the network. It ensures session continuity by redirecting calls to alternative destinations, preventing missed communications when devices are offline or out of coverage. This service is crucial for maintaining reliable communication availability in mobile networks.

Communication Forwarding No Reply

A supplementary service that automatically redirects an incoming voice or multimedia call to a pre-defined alternative number if the called party does not answer. It is a fundamental call management feature for improving call completion and user availability in mobile networks.

Call Forwarding on No Reply

A supplementary service that automatically redirects an incoming call to a pre-configured number when the called party does not answer within a defined time period. It ensures call completion and improves user experience by preventing missed connections. This service is part of the 3GPP's standardized call forwarding feature set.

Communication Forwarding Unconditional

CFU is a supplementary service that automatically forwards all incoming communication sessions (calls) to a predetermined number without ringing the original destination. It ensures users never miss important communications by redirecting sessions to an alternative device or voicemail system when unavailable.

Communication Forwarding User Determined Busy

CFUDB is a supplementary service that allows a user to redirect incoming calls to another number when the user is busy. It provides personalized call management by enabling users to define specific forwarding destinations based on their availability status. This service enhances user control over communication flow and network resource utilization.

Charge Generation Point

The Charge Generation Point is a network function responsible for creating charging records for network usage and services. It collects charging information from various network elements and formats it for billing systems. This enables accurate service monetization and revenue assurance for operators.

Coarse Grain Scalability

CGS is a video coding scalability feature enabling efficient adaptation of video streams to varying network conditions and device capabilities. It allows a base layer to be enhanced with additional quality layers, supporting flexible bitrate and resolution adjustments. This is crucial for delivering consistent video quality in mobile networks with fluctuating bandwidth.

Charge Unit

A base element for the charging process, expressed in monetary or non-monetary units. It quantifies the amount of resource consumption or service usage that is converted into a charge by the charging system.

Chargeable Event

An activity that uses telecommunications network infrastructure or services and that the network operator wants to charge for. It can be a call, data session, SMS, mobility procedure, or inter-network signalling, and forms the basis for charging records and tariffs.

Coverage and Handoff Enhancements using Multimedia error robustness

CHEM is a 3GPP feature introduced in Release 16 that improves coverage and handoff for multimedia services by leveraging error robustness techniques. It enhances the reliability and continuity of real-time multimedia applications in challenging radio conditions.

Constrained High Profile

A 3GPP audio codec profile designed for high-quality speech transmission in bandwidth-constrained environments. It optimizes bitrate efficiency while maintaining superior voice quality, particularly important for mobile networks with limited capacity. CHP enables robust voice services across diverse network conditions and device capabilities.

Common Informative Binaural Renderer

CIBR is a standardized binaural renderer for immersive audio services like Extended Reality (XR) and 3GPP Audio. It processes spatial audio objects and scene descriptions to generate binaural signals for headphones, enabling consistent, high-quality 3D audio experiences across devices and networks.

Coding-Independent Code Points

Coding-Independent Code Points (CICP) are standardized identifiers for audio and video codecs and their configurations, defined in 3GPP. They enable unambiguous signaling of media capabilities and preferences between endpoints in multimedia services, independent of the underlying transport or session protocol. This ensures interoperability and efficient media negotiation in IMS and other communication systems.

Cell-ID Positioning Method

CID is a network-based positioning method that identifies a mobile device's location based on the serving cell's geographic coverage area. It provides the simplest form of location determination in cellular networks by associating the device with its current cell's known coordinates and coverage radius. While less precise than advanced methods, it requires no device modifications and serves as a fallback when other positioning techniques are unavailable.

Centimeter Level Augmentation Service

CLAS is a 3GPP positioning service that delivers centimeter-level accuracy to user equipment by combining GNSS measurements with network-provided correction data. It enables high-precision location services for applications like autonomous vehicles, industrial automation, and augmented reality. The service operates by transmitting differential correction information through the cellular network to compensate for GNSS errors.

Calling Line Identification Presentation

CLIP is a supplementary service in 3GPP networks that displays the calling party's phone number to the called party before answering. It enables call screening, enhances user experience, and supports services like call-back and call blocking. This feature is fundamental for telephony services, providing transparency and control over incoming calls.

Calling Line Identification Restriction

A supplementary service that allows a calling party to prevent their phone number from being displayed to the called party. It provides privacy protection by restricting the transmission of the calling line identity (CLI) in the signaling messages during call setup, enabling users to control when their number is revealed.

Connectionless Network Service

CLNS is a packet-switched network service that transmits data without establishing a dedicated end-to-end connection. It enables efficient, on-demand data transfer for applications with sporadic traffic, such as early mobile data services. This service is foundational for supporting IP-based communication in GSM and UMTS networks.

Closed-Loop Pitch Analysis (Adaptive Codebook Search)

A speech codec technique that estimates the pitch lag by minimizing error through analysis-by-synthesis, forming the adaptive codebook search in AMR and AMR-WB codecs. It is fundamental to efficient speech compression in 3GPP voice services.

ControLling mUltiple streams for tElepresence

CLUE is an IETF working group and protocol framework for controlling multiple media streams in telepresence systems. It enables dynamic selection and configuration of audio/video streams based on participant layout and preferences.

Common Media Application Format

CMAF is a standardized media format for adaptive bitrate streaming, enabling efficient delivery of audio and video content over networks. It reduces storage and delivery costs by allowing a single set of media segments to be used across multiple streaming protocols and devices. This is crucial for scalable, high-quality media services in 3GPP networks.

Commercial Mobile Alert Service

CMAS is a 3GPP standardized public warning system that delivers emergency alerts (e.g., extreme weather, AMBER alerts) to mobile users via cellular broadcast. It enables authorities to send geographically targeted, multilingual alerts to all compatible devices in a threat area, ensuring rapid public safety communication without network congestion.

Convergent Multi-Media Conference

CMMC is a 3GPP service enabling multimedia conferencing sessions over IMS networks. It integrates voice, video, and data streams into a single, managed conference, supporting various user terminals and network types. This service is crucial for delivering rich, interactive group communication experiences in mobile and fixed networks.

Coded Multisource Media Format

CMMF is a 3GPP Rel-19 media format for coded multisource media, enabling efficient delivery and synchronization of content captured from multiple sources. It supports immersive and multiview services in 5G media streaming.

CAMEL Modified Number

A CAMEL (Customised Applications for Mobile networks Enhanced Logic) service that modifies the destination number of a call during call setup. It enables intelligent network-based number translation for services like number portability, VPN routing, and freephone services by intercepting and altering dialed numbers before call routing.

Codec Mode Request

Codec Mode Request (CMR) is a signaling mechanism used in voice services over 3GPP networks to dynamically request a change in the speech codec mode. It is essential for Adaptive Multi-Rate (AMR), AMR-Wideband (AMR-WB), and Enhanced Voice Services (EVS) codecs, enabling optimal voice quality adaptation to varying radio conditions by balancing bitrate and error resilience.

Codec Mode Request / Codec Mode Command

CMR/CMC is a signaling mechanism in 3GPP voice services, primarily for Adaptive Multi-Rate (AMR) and AMR-Wideband codecs. It allows the receiving end of a voice call to request a specific codec mode from the transmitting end, optimizing speech quality and bandwidth usage based on network conditions. This dynamic adaptation is crucial for maintaining consistent voice quality in mobile networks.

Comfort Noise Addition

Comfort Noise Addition (CNA) is a technique introduced in 3GPP Release 18 to improve audio quality during discontinuous transmission (DTX) in voice services. It generates and inserts artificial background noise during silent periods to prevent the perception of 'dead air,' enhancing user comfort and call naturalness. This is particularly important for modern codecs and network conditions where complete silence can be disconcerting.

Calling Name Presentation

CNAP is a supplementary service that displays the name of the calling party to the called subscriber before answering. It enhances user experience by providing caller identification beyond just the phone number, helping users decide whether to answer calls. The service operates within the Intelligent Network (IN) architecture of 3GPP networks.

Civil Navigation

CNAV is a 3GPP service providing civil navigation capabilities, primarily for satellite-based positioning systems like GPS and Galileo, integrated into mobile networks. It enables devices to receive and process navigation data for location services, supporting applications such as emergency calls, mapping, and asset tracking. This integration is crucial for delivering accurate positioning in cellular devices.

Calling Name Database

The Calling Name Database (CNDB) is a network element that stores and provides calling name information for subscribers. It enables the display of the caller's name on the recipient's device during voice calls, enhancing user experience and call identification. This service is crucial for operator-branded calling name presentation services.

Comfort Noise Generation

A technique used in voice communication systems to generate artificial background noise during silent periods in a conversation. It prevents the perception of complete silence, which can be disconcerting to listeners, and maintains a natural-sounding audio experience. This is crucial for user comfort and perceived call quality in digital telephony.

Completion of Communications on No Reply

CNR is a supplementary service that automatically completes a call when the called party doesn't answer within a specified time. It redirects the call to voicemail or another destination, improving call completion rates and user experience by handling unanswered calls efficiently.

Coder/Decoder

A CODEC (Coder/Decoder) is a hardware or software algorithm that compresses and decompresses digital media streams, primarily audio and video. It enables efficient transmission and storage by reducing data size while maintaining acceptable quality. In 3GPP networks, CODECs are essential for voice calls, video calls, and multimedia services over bandwidth-constrained radio interfaces.

Codec Configuration

Defines the operational parameters of a speech codec, such as AMR, including the Active Codec Set, the OM flag, and DTX settings. It ensures that both ends of a call use compatible codec modes and features for optimal voice quality and efficiency.

Codec mode

A specific operating mode of a speech codec, such as AMR or AMR-WB, that corresponds to a particular bitrate. For AMR, there are eight codec modes (excluding SID), each with a different bitrate, allowing adaptation to radio conditions.

Connected Line Identity

COLI (Connected Line Identity) is a supplementary service that provides the identity of the party to which a call is actually connected, which may differ from the originally dialed number. It is crucial for accurate billing, fraud prevention, and lawful interception by ensuring the network correctly identifies the final connection point of a call.

Collaborative Session

A logical set of IMS sessions across multiple UEs sharing one IMS subscription, anchored in the SCC AS and presented as a single session to the remote party. It enables media sharing and session continuity across devices.

Collaborative Session Control

The set of control operations on a Collaborative Session that only the Controller UE is authorized to perform, such as releasing the session, invoking supplementary services, and authorizing media control requests from other UEs.

Connected Line identification Presentation

COLP is a supplementary service in 3GPP networks that allows the called party to present their own phone number to the calling party. It is the counterpart to CLIP (Calling Line Identification Presentation) and is crucial for providing transparency and trust in telecommunication services by verifying the identity of the connected line.

Connected Line identification Restriction

COLR is a supplementary service that allows the called party to restrict the presentation of their phone number (MSISDN) to the calling party. It ensures privacy by preventing the caller from seeing the connected line's identity, which is crucial for personal and business confidentiality in telecommunications.

Combinational call

A service where a circuit-switched speech call is enriched by an IMS session, with both services originated in one UE and terminated in another. It enables simultaneous CS and IMS services, such as adding video or data to a voice call.

Combinational Service

A service that combines a Circuit Switched (CS) call with one or more IP Multimedia Subsystem (IMS) components, established between the same participants. It enables enriched voice communication by adding real-time multimedia to a traditional voice call.

Commercial Mobile Alert System

A Public Warning System that delivers Warning Notifications from authorized providers to mobile users. It defines three alert classes: Presidential, Imminent Threat, and Child Abduction Emergency, ensuring timely dissemination of critical information.

Communication Information

Information collected and registered by the MCID service, used for lawful interception and fraud detection in 3GPP networks.

CONference calling

CON is a supplementary service in 3GPP networks enabling multiple participants to join a single voice call. It allows a user to establish a conference call by inviting other parties, supporting both ad-hoc and pre-arranged conferences. This service enhances communication efficiency for business and personal use by facilitating group discussions over cellular networks.

CONFerence calling

CONF is a supplementary service enabling multiple participants to engage in simultaneous voice or multimedia communication sessions. It allows users to establish, manage, and participate in conference calls, supporting both ad-hoc and scheduled conferences. This service is fundamental for business communications, collaboration, and group discussions within 3GPP networks.

Conference

An IP multimedia session with two or more participants, managed by a conference focus. It enables multi-party communication services such as telepresence, multimedia games, and group calls in IMS.

Conference Focus

The entity in an IMS conference responsible for hosting, managing, and manipulating the media and policy. It implements conference policy and ensures orderly multi-party communication.

Connectionless service

A service that transfers information among users without end-to-end call establishment. It enables packet-based communication where each data unit is routed independently, essential for IP-based services in 3GPP networks.

Connection-Oriented Network Service

CONS is a circuit-switched network service defined in 3GPP for establishing dedicated, reliable connections between endpoints. It provides guaranteed bandwidth, low latency, and sequential data delivery, making it essential for traditional voice calls and real-time applications. While largely superseded by packet-switched services in modern networks, it formed the foundation for early mobile telephony services.

Content Cache Server

An entity that caches partial or entire source content for distribution to end users, typically deployed at the network edge to accelerate content delivery and reduce backhaul traffic.

Content Source Server

An entity that stores source content and provides an interface for other entities to fetch content. It is a key component in content delivery and caching architectures within 3GPP networks.

Continuous media

Media with an inherent notion of time, such as speech, audio, video, timed text, and timed graphics. It is a foundational concept for real-time streaming and conversational services in 3GPP.

Controllee User Equipment

A UE that supports media flows for a Collaborative Session and may request IUT Media Control Related Procedures but is subordinate to the Controller UE for authorization of these procedures.

Controller capable User Equipment

A UE that is capable of becoming a controller UE, meaning it has the necessary capabilities to control a Collaborative Session in IMS.

Controller User Equipment

The UE that controls a Collaborative Session and whose service profile determines the services on the remote leg. It may also support media flows and request IUT Media Control Related Procedures.

Conversational Service

A conversational service is a real-time, bi-directional communication service that enables end-to-end information transfer between users without store-and-forward. It is one of the four QoS traffic classes defined by 3GPP, supporting voice and video telephony.

Cooperating User Equipments

A group of UEs with associated subscriptions that allow them to cooperate when in proximity, in coordination with the network, to improve energy efficiency and user experience.

Cross-Origin Resource Sharing

CORS is a security mechanism that allows web applications running in one origin to access resources from a different origin. In 3GPP, it enables secure cross-origin API calls for network exposure functions, allowing third-party applications to safely interact with network capabilities while maintaining security boundaries.

Chinese Public Alert System

CPAS is a public warning system mandated in China to disseminate emergency alerts to mobile users. It is standardized in 3GPP to ensure timely and widespread delivery of alerts during disasters.

Coding Picture Buffer

The Coding Picture Buffer (CPB) is a decoder-side buffer model used in video codecs to manage the timing and buffering of compressed video data during transmission. It ensures smooth video playback by compensating for variable network delays and bitrate fluctuations, preventing underflow or overflow. This is critical for maintaining Quality of Experience (QoS) in streaming services over mobile networks.

Content Provider Charging Function

The CPCF is a network function responsible for charging for content-based services, enabling operators to bill for third-party content. It interfaces with content providers and the operator's charging system to generate accurate usage records. This supports business models like premium content, advertising, and sponsored data.

Call Progress message

A signaling message used in 3GPP networks to convey the status of a call setup or modification procedure between network entities. It provides standardized information about call progress events, such as alerting, connect, or disconnect, enabling reliable call control and user feedback.

Call Party Handling

CPH is a set of procedures and capabilities within the CAMEL (Customized Applications for Mobile network Enhanced Logic) service framework for managing the participants in a mobile call. It enables network operators to provide advanced call control services, such as call waiting, call hold, and multi-party conferencing, by allowing dynamic manipulation of call legs. This is crucial for delivering sophisticated, value-added telephony services beyond basic voice connectivity.

Common Presence and Instant Messaging

CPIM is a 3GPP service enabler standardizing presence and instant messaging (IM) for IP Multimedia Subsystem (IMS) networks. It defines protocols and procedures for user availability, status publication, and real-time text communication. This enables interoperable, carrier-grade messaging services across different operators and devices.

Call Processing Language

CPL is a standardized scripting language defined by 3GPP for describing and controlling telephony services in IP-based networks. It enables service providers to create customized call handling behaviors without requiring complex programming. This language provides a standardized way to implement services like call forwarding, screening, and time-based routing.

Collective Perception Message

CPM is a standardized message format for Vehicle-to-Everything (V2X) communication, enabling vehicles and infrastructure to share detailed, real-time sensor-derived perception data about their surroundings. It is crucial for enhancing situational awareness beyond the line-of-sight, supporting advanced cooperative, connected, and automated mobility (CCAM) applications.

Conversational Quality

CQ (Conversational Quality) is a standardized 3GPP metric for evaluating the quality of voice and video calls in real-time communication services. It provides objective measurement of user-perceived quality during conversational services, enabling operators to monitor and optimize network performance for voice and video calls. This metric is crucial for maintaining service quality and ensuring user satisfaction in mobile networks.

Charging Tariff Information

CRGT is a standardized data structure in 3GPP networks that carries detailed tariff information for charging events. It is used by the Online Charging System (OCS) to determine the cost of a service in real-time, enabling accurate and flexible billing for network usage. This is essential for prepaid services, policy control, and monetizing diverse network offerings.

Call Related Mobile Number Portability

CRMNP is a 3GPP service enabling subscribers to retain their mobile phone numbers when switching network operators. It ensures call routing to the correct network after porting, supporting regulatory mandates for consumer choice and competition. This is a foundational feature for modern, competitive telecommunications markets.

Call Request with Number

A supplementary service that allows a user to request a call to a specific number without dialing it directly. It enables network-initiated call setup based on stored or provided numbers, supporting features like abbreviated dialing and call-back services. This service enhances user convenience and enables advanced telephony applications.

Create, Retrieve, Update, Delete and Notify

CRUDN is a standardized set of data management operations defined in 3GPP for the Service Enabler Architecture Layer (SEAL). It provides a common API framework for creating, reading, updating, deleting, and subscribing to notifications for network data objects. This enables consistent data management across different vertical applications and network functions.

Capability Set 1

Capability Set 1 (CS1) is the initial standardized set of capabilities for the IP Multimedia Subsystem (IMS) defined in 3GPP Release 8. It establishes the foundational service architecture for delivering multimedia services over packet-switched networks, enabling standardized voice, video, and messaging services across different operator networks and devices.

Capability Set 2

Capability Set 2 (CS2) is a standardized set of enhanced telephony and multimedia service capabilities for the IP Multimedia Subsystem (IMS). It builds upon earlier capability sets to provide richer, more flexible communication services over packet-switched networks, enabling advanced call control and supplementary services.

Communication Service Customer

The Communication Service Customer (CSC) is a 3GPP management concept representing the entity that purchases, consumes, and manages communication services from a network operator or service provider. It is a key actor in service management and network slicing frameworks, enabling customer-centric service provisioning, monitoring, and assurance. This concept is fundamental for business-to-business (B2B) models and network-as-a-service offerings.

Common Supported Codec Set

CSCS is a standardized list of audio and video codecs that a network operator supports for multimedia services. It enables efficient codec negotiation between networks and devices, ensuring interoperability and optimal media quality. This is crucial for consistent user experience in voice and video calls across different operators and regions.

Circuit Switched Data

Circuit Switched Data (CSD) is a 2G/3G service enabling data transmission over dedicated circuit-switched connections, primarily for low-speed applications like fax and early internet access. It established the foundation for mobile data services by providing reliable, connection-oriented data transfer with guaranteed bandwidth. While largely superseded by packet-switched technologies, CSD was crucial for early mobile data adoption and remains relevant for some legacy and specialized applications.

Camel Service Environment

CSE is the standardized execution environment for CAMEL (Customised Applications for Mobile network Enhanced Logic) services in GSM and UMTS networks. It enables the deployment of operator-specific, intelligent network (IN) services like prepaid billing, VPN, and location-based services across home and visited networks, ensuring consistent service logic execution.

Closed Subscriber Group

A Closed Subscriber Group (CSG) is a set of subscribers authorized to access one or more CSG cells, typically deployed as femtocells or small cells in private locations. It enables network operators to offer restricted access to specific users, creating private or semi-private cellular coverage areas. This is crucial for enterprise deployments, residential coverage enhancement, and controlled access scenarios.

Circuit Switched IMS Combinational Service

CSICS enables simultaneous use of circuit-switched voice calls and IMS-based multimedia services over a single radio connection. It allows operators to offer enhanced services like video sharing during voice calls while maintaining backward compatibility with legacy networks. This technology bridges the gap between traditional circuit-switched networks and emerging IP Multimedia Subsystem services.

Combinational Service ICS capable User Equipment

A user equipment that supports Combinational Service, enabling simultaneous circuit-switched and IP-based services over a single access connection. It is a key enabler for the evolution from traditional CS-only networks to IMS-based multimedia telephony.

Call Segment Identifier

CSID is a unique identifier for a segment within a call or session, enabling granular control and charging in IMS/CS networks. It allows network functions to differentiate and apply policies to specific parts of a communication, such as a forwarded leg or a conference participant.

Communications Service Provider

Communications Service Provider (CSP) is a 3GPP-defined entity that offers communication services to end-users, including mobile network operators, fixed-line providers, and converged operators. It represents the business entity responsible for service delivery, customer relationships, and network operations within the 3GPP ecosystem. This concept is fundamental for service management, charging, security, and regulatory compliance across 3GPP networks.

Call Transfer supplementary service

CT is a supplementary service in 3GPP networks that enables a user to transfer an established call to a third party. It allows the transferring party to either retrieve the call or complete the transfer, facilitating call management and collaboration. This service is fundamental for professional telephony features in mobile networks.

Cellular Text telephone Modem

CTM is a 3GPP service enabling real-time text communication for users with hearing or speech disabilities over cellular networks. It provides an alternative to voice calls by transmitting text characters as they are typed, ensuring conversational flow. This service is crucial for accessibility, bridging communication gaps in mobile telephony.

Cordless Telephony System

CTS is a 3GPP standardized cordless telephony service enabling mobile devices to connect to residential or enterprise base stations for local voice and data services. It provides seamless mobility between cellular networks and local cordless coverage, offering cost-effective local calling and improved indoor coverage. This technology bridges cellular and fixed-line telephony concepts.

Cellular Text Telephone Modem Mobile Equipment

CTS-ME enables text telephony services for hearing- and speech-impaired users over cellular networks. It provides real-time text communication by integrating a text telephone modem into mobile devices, ensuring accessibility compliance and bridging communication gaps for users with disabilities.

Closed User Group

A Closed User Group (CUG) is a telecommunications service feature that allows a defined group of subscribers to communicate exclusively among themselves, while restricting or controlling communication with users outside the group. It is used to create private communication networks within the public mobile network, enabling secure and controlled access for corporate, government, or specialized user communities.

Closed User Group Index

A parameter used by the originating user to select a particular Closed User Group (CUG) when originating a communication. It allows users to specify which CUG they want to use for a call.

Closed User Group Manager

The CUG Manager is the administrative authority representing the interests of all members of a Closed User Group (CUG) in 3GPP networks. It manages group membership, enforces access restrictions, and controls which subscribers can communicate within the closed group, as defined in 3GPP TS 24.454 and TS 24.654.

Current Location

In 3GPP location services (LCS), the Current Location is the location estimate and its associated timestamp, produced after a successful location attempt. It represents the most recent known position of a target User Equipment (UE) and is fundamental to location-based services and emergency call handling.

Customized Alerting Tone

An indication customized by the called or calling party, played to the calling party during call establishment or an established call session. It can be music, voice, advertisement, or video, replacing the standard ringback tone.

Customized Alerting Tone Service

An operator-specific supplementary service that lets subscribers replace the standard ringback tone heard by callers with personalized audio, video, or multimedia content during call setup.

Customized Ringing Signal

An operator-specific service that replaces the standard incoming communication indication with personalized content such as pictures, music, video, or voice, customized by either the calling or called party.

Coordination of Video Orientation

CVO is a 3GPP service that synchronizes video orientation between transmitting and receiving devices during video calls. It ensures proper display orientation regardless of device rotation, preventing upside-down or sideways video. This enhances user experience by maintaining consistent video presentation across different device orientations.

Coded Video Sequence

Coded Video Sequence (CVS) is a fundamental video coding structure defined by 3GPP for the carriage of video content over mobile networks. It represents a contiguous sequence of coded video pictures that can be independently decoded, forming a complete video presentation or a significant segment thereof. Its standardized definition ensures reliable video delivery and interoperability across devices and networks, which is critical for mobile video streaming and broadcast services.

Dialled Services CAMEL Subscription Information

D-CSI is a CAMEL subscription parameter that enables the Home Location Register (HLR) to inform the Visited Mobile Switching Center (VMSC) about the need to invoke CAMEL services for specific dialled numbers. It is crucial for implementing intelligent network features like prepaid billing, call screening, and number translation for mobile-originated calls based on the destination number dialled by the subscriber.

Distribution Automation

Distribution Automation (DA) is a 3GPP service enabling automated monitoring, control, and protection of electrical power distribution networks using cellular communication. It supports critical smart grid applications like fault detection, isolation, and restoration (FDIR), and remote control of switches and reclosers. This enhances grid reliability, efficiency, and enables integration of distributed energy resources.

Declarative Application Environment

DAE is a 3GPP framework enabling network exposure and application interaction through declarative APIs. It allows applications to specify desired network behaviors and outcomes rather than imperative commands, simplifying application development and network integration. This approach enhances service agility and reduces complexity in managing network resources.

DASH Aware Network Element

A network element that is aware of Dynamic Adaptive Streaming over HTTP (DASH) operations to optimize media delivery. It monitors DASH client behavior and network conditions to improve Quality of Experience (QoE) by enabling network-assisted streaming optimizations. This is crucial for efficient video delivery in mobile networks.

Dynamic Adaptive Streaming over HTTP

DASH is an adaptive bitrate streaming standard for delivering media over HTTP. It enables clients to dynamically select the best quality video segment based on network conditions and device capabilities, ensuring smooth playback. This is crucial for efficient video delivery in mobile and broadband networks.

DASH Industry Forum

DASH-IF is an industry consortium that develops and promotes the MPEG-DASH standard for adaptive bitrate streaming over HTTP. It provides guidelines, test vectors, and reference software to ensure interoperability and efficient delivery of multimedia content in 3GPP networks, crucial for mobile video services.

Data Application Ancillary

A functional component that provides send and/or receive data access to UMTS services via the User Equipment (UE). It enables applications to exchange data over the UMTS network.

Digital Audio Workstation

DAW is a standardized interface for professional audio production systems to integrate with 3GPP networks. It enables high-quality audio streaming, synchronization, and collaborative workflows over mobile networks, supporting music production, broadcasting, and live events.

Direct Communication Accept

DCA is a signaling procedure in 3GPP networks that enables direct device-to-device (D2D) communication. It allows a receiving UE to accept or reject a request for direct communication from another UE, establishing a peer-to-peer link without routing through the network core. This is fundamental for Proximity Services (ProSe) and public safety communications.

Data Channel Application Repository

A repository and management framework for applications that utilize 5G Data Channels. It enables the discovery, deployment, and lifecycle management of applications that leverage the enhanced communication capabilities of 5G networks, such as low-latency and high-reliability data streams.

Dynamic Content Delivery

DCD is a 3GPP service enabling efficient, adaptive delivery of multimedia content over mobile networks. It optimizes bandwidth usage and user experience by dynamically adjusting content quality based on network conditions and device capabilities. This is crucial for scalable media streaming and reducing network congestion.

Data Channel Multimedia Telephony Service over IMS

DCMTSI is a 3GPP standardized service enabling real-time multimedia telephony over IMS using WebRTC data channels. It supports voice, video, and data sharing within a single session, enhancing conversational services. This is crucial for web-based and app-based communication, bridging IMS and modern web technologies.

Degradation Category Rating

The Degradation Category Rating (DCR) method is a standardized subjective quality assessment technique used in 3GPP to evaluate the perceptual quality of speech and audio codecs under various network degradation conditions. It provides a structured framework for human listeners to rate the quality of processed speech signals compared to a reference, specifically focusing on the impact of degradations like packet loss, jitter, and compression artifacts. This method is crucial for standardizing codec performance evaluation, enabling objective comparisons between different voice over IP (VoIP) and telecommunication technologies.

Device Description Framework

DDF is a standardized framework for describing device capabilities and characteristics in 3GPP networks. It enables network services to adapt content and functionality based on device properties, ensuring optimal user experience across diverse mobile devices. This framework is crucial for content adaptation, service personalization, and efficient resource utilization in heterogeneous device environments.

Digital Entertainment Content Ecosystem

DECE is a standardized ecosystem for managing and distributing digital entertainment content across multiple devices and platforms. It enables secure content delivery, rights management, and interoperability between different service providers and device manufacturers. This matters because it creates a unified framework for digital media consumption in 3GPP networks.

Decoder homing frame

A decoder homing frame is a specific frame used in AMR-WB speech codecs to synchronise the decoder state. There are nine such frames, one for each AMR-WB codec mode, and they ensure correct decoding after consecutive encoder homing frames.

MMS Delivery Report

Feedback information sent by an MMS Relay/Server to the originator of a multimedia message about the delivery status of that message. It confirms whether the MM was delivered, expired, rejected, or deferred.

Demand service

A telecommunication service where the communication path is established almost immediately upon a user request via user-network signalling. It is a foundational service category in 3GPP and ITU-T frameworks, distinguishing on-demand connections from pre-established or permanent ones.

Decentralized Environmental Notification Message

A standardized V2X message used in 3GPP-based Cellular-V2X (C-V2X) to broadcast time-sensitive safety and traffic event information directly between vehicles and roadside infrastructure. It enables decentralized, low-latency awareness of hazards like accidents, roadworks, or adverse weather without relying on network infrastructure.

Destination B (Busy Called Party in Completion of Calls to Busy Subscriber)

Destination B is the called party addressed in the original call set-up who is busy when first called by subscriber A. It is the logical role that anchors the CCBS supplementary service, with MSC B, VLR B and HLR B being the network elements serving that party.

Destination Service Subscriber (VGCS Called Party)

The destination service subscriber is the service subscriber to which a Voice Group Call Service (VGCS) call is directed. It identifies the called party role in GERAN group-call procedures defined in TS 42.068 and TS 42.069.

Destination User (GPRS Called Party)

The destination user is the entity to which calls to the General Packet Radio Service (GPRS) are directed. Defined in the 3GPP vocabulary of TS 21.905 and used in the GPRS service description of TS 22.060.

Delivery Function

The Delivery Function is a network element responsible for managing and delivering content, services, or messages to user equipment. It acts as an intermediary between service providers and mobile networks, ensuring reliable, efficient delivery with appropriate quality of service. Its role is crucial for enabling value-added services like multimedia messaging, content distribution, and application-to-person communications.

Delivery Function 3

DF3 is a standardized delivery function defined in 3GPP TS 43.033 for Short Message Service (SMS) delivery in GSM/UMTS networks. It handles the routing and delivery of SMS messages between the Short Message Service Center (SMSC) and the Mobile Station (MS). Its standardized definition ensures reliable, interoperable SMS delivery across different network implementations.

Differential Global Navigation Satellite System

DGANSS is a 3GPP positioning service that provides differential corrections to GNSS receivers via cellular networks. It enhances location accuracy by compensating for atmospheric and satellite orbit errors, enabling precise positioning for emergency services, navigation, and location-based applications.

Differential Global Navigation Satellite System

DGNSS is a positioning enhancement service that improves GNSS accuracy by transmitting correction data over cellular networks. It addresses atmospheric errors and satellite clock/ephemeris inaccuracies to provide centimeter-to-meter level precision for location-based services, emergency calls, and navigation applications.

Differential Global Positioning System

DGPS is a positioning enhancement technique that improves GPS accuracy by using reference stations to calculate and broadcast correction data to mobile devices. It reduces errors from atmospheric delays, satellite clock inaccuracies, and ephemeris data, enabling location-based services with meter-level precision in 3GPP networks.

Disregard Incoming Call

DIC is a supplementary service in GSM/UMTS/LTE that allows a served user to temporarily reject all incoming calls. When activated, the network prevents call setup attempts to the user, presenting a busy tone or redirecting to voicemail. It provides users with a simple 'do not disturb' function managed via USSD codes or network settings.

Digital Representation

A digital representation is mobile metaverse media that presents a virtual or physical object, potentially reflecting its current state. It enables immersive, interactive experiences in the mobile metaverse, such as avatars or virtual objects.

Digital Twin

A digital twin is a real-time representation of physical assets in a digital world. It enables monitoring, simulation, and control of physical entities through 5G connectivity, supporting use cases in manufacturing, smart cities, and healthcare.

Dynamic and Interactive Multimedia Scene

A 3GPP service enabling synchronized, interactive multimedia presentations across multiple devices. It defines 'scenes' composed of media components and scene commands, allowing for rich, coordinated user experiences like multi-screen sports broadcasts or interactive educational content.

Disaster Condition

A Disaster Condition is a state declared by a government due to a natural or man-made disaster, enabling special network procedures to mitigate service interruptions. It allows users to access services via alternative networks and ensures continued connectivity during emergencies.

Disaster Roaming

A special roaming service that enables subscribers to use visited networks during a disaster condition when their home network is unavailable, ensuring emergency communication continuity.

Discrete media

Media that does not contain an element of time, such as images and text, as opposed to continuous media like audio and video. It is a fundamental concept in multimedia messaging and streaming services.

Dispatcher

A special user role in group communication systems that automatically receives all voice broadcast calls to a specific group ID and can initiate such calls, typically used in dispatch services for public safety and utilities.

Distribution Service

A service that provides unidirectional information flow from a single point in the network to multiple other locations. It underpins broadcast and multicast delivery in 3GPP networks, enabling efficient one-to-many content distribution.

Downlink Time Difference Of Arrival

A network-based positioning method where a UE measures the time difference of arrival of signals from multiple synchronized gNBs. The UE reports these Reference Signal Time Difference (RSTD) measurements to the network, which calculates the UE's location via multilateration. It is a key technique for 5G NR positioning.

Downloadable Sounds

A 3GPP service enabling the download of audio files (like ringtones, alert tones) over-the-air to a user's mobile device. It standardizes the format, delivery, and management of these sound files, enriching the personalization and user experience.

Degradation Mean Opinion Score

A perceptual video quality metric that predicts the subjective quality a user would experience when video quality degrades, such as during network congestion or handover. It is derived from the Mean Opinion Score (MOS) scale and is crucial for network operators to monitor and optimize video streaming Quality of Experience (QoE) in mobile networks.

Declarative Object

A Declarative Object is a data structure defined in 3GPP specifications, particularly for USIM applications, that describes a service or feature in a declarative manner. It allows for the dynamic configuration and provisioning of services on the UICC without requiring low-level procedural programming.

Device-Originated Device-Terminated Triggered

A 3GPP Rel-19 service pattern where a device initiates communication that triggers a response terminating at another device, enabling efficient device-to-device interactions in 5G-Advanced networks.

Donor Network

The subscription network from which a mobile number is ported during number portability. It may or may not be the original number range owner, and it relinquishes the number to the recipient network.

Downlink Exchanges

Downlink exchanges refer to the transmission of data from servers and networks to the terminal (user equipment). This term is used in the context of specific services like messaging and data transfer.

Decoded Picture Buffer

A buffer in video codecs that stores decoded reference frames for use in inter-picture prediction. It is a fundamental component of video compression standards like H.264/AVC and H.265/HEVC, enabling efficient temporal prediction and ensuring correct video playback order and quality.

Device Playback Capabilities

A set of parameters describing a user device's audio and video playback characteristics, such as supported codecs, resolutions, and bitrates. Used in media adaptation and service negotiation to ensure multimedia content is delivered in a format the device can properly render, optimizing user experience and network efficiency.

Direct Services Provisioning Function

The Direct Services Provisioning Function (DPF) is a network function that enables the direct provisioning of services to a User Equipment (UE) without requiring the UE to be attached to the 3GPP network for control-plane signaling. It is a key enabler for IoT and MTC services, allowing efficient, network-triggered wake-up and data delivery to devices in power-saving states.

Digital Rights Management

A system of technologies and standards for securely distributing, controlling access to, and protecting the copyright of digital media content (e.g., music, video) delivered over mobile networks. It enforces usage rules defined by content providers.

Discovery Service

A service defined within the Location Services (LCS) architecture that enables an authorized client (LCS Client) to discover which Location Servers (e.g., GMLC, LMF) are available in a network or across networks. It provides addressing and capability information, facilitating interoperable and efficient positioning service requests.

Distant Supported Codec Set

A set of codecs supported by a remote terminal in a communication session. It enables efficient codec negotiation between endpoints, ensuring compatible and optimal media encoding/decoding for services like voice and video calls across networks.

Digital Speech Interpolation

Digital Speech Interpolation (DSI) is a voice compression technique that increases the capacity of transmission channels by exploiting silent periods in human speech. It dynamically allocates bandwidth only during active speech segments, allowing multiple conversations to share a single channel. This technology is crucial for efficiently utilizing expensive transmission resources in telecommunication networks.

Digital Storage Media – Command and Control

DSM-CC is a protocol suite standardized by 3GPP for controlling and managing multimedia content delivery over networks. It enables interactive services, video on demand, and data broadcasting by providing session management, resource control, and user-to-network signaling. Its importance lies in supporting rich media applications in mobile and broadcast environments.

Distributed Speech Recognition

A service architecture where speech recognition processing is split between the mobile device (front-end) and a network server (back-end). The device extracts and compresses speech features, which are transmitted over the network for final recognition. This enables robust, network-based voice control and dictation services even in limited bandwidth conditions.

Data Termination

Data Termination (DT) is a network capability or functional entity that provides the termination point for a packet data connection, handling the final routing and delivery of user data to its intended application or service endpoint within the network or to an external network.

Domain Transfer Function

The Domain Transfer Function (DTF) is a functional entity defined in 3GPP for Voice Call Continuity (VCC). It acts as an anchor point within the IMS core, routing calls and facilitating seamless handover of voice sessions between Circuit-Switched (CS) and IP Multimedia Subsystem (IMS) domains.

Digital Terrestrial Multimedia Broadcast

A broadcast service in 3GPP standards for delivering multimedia content over terrestrial radio networks. It enables efficient, high-quality video and audio streaming to mobile and fixed devices, leveraging cellular infrastructure for wide-area coverage and spectrum efficiency.

Dual Tone Multiple Frequency

A signaling method using pairs of audio frequencies to represent digits and symbols, enabling in-band control for telephony services. It allows users to interact with automated systems, navigate menus, and authenticate services during voice calls, essential for interactive voice response (IVR) and legacy telephony features.

Deflected To Number

A call forwarding feature that redirects an incoming call to a different number specified by the called party. It allows users to manage call routing dynamically, enhancing flexibility and ensuring calls reach them at alternative locations, commonly used in business and personal telephony services.

Data Transport Service

Data Transport Service (DTS) is a foundational 3GPP service concept encompassing the reliable, efficient, and QoS-aware carriage of user data and signaling across the network. It underpins all IP-based communication services, from IMS voice to internet access. Its specifications define the architectural framework and policy control for data flow handling.

Digital TeleVision

DTV refers to the delivery of digital television services over 3GPP networks, primarily via Multimedia Broadcast Multicast Service (MBMS) and evolved MBMS (eMBMS). It enables efficient broadcast of live and on-demand video content to mobile devices, supporting features like high-definition video and closed captioning. This service is crucial for mobile TV and public safety communications.

DTV Closed Caption

DTVCC is the closed captioning system specified for Digital TeleVision services in 3GPP networks. It provides text overlays for dialogue and audio descriptions to make video content accessible to hearing-impaired viewers. The specification ensures standardized encoding, transport, and synchronization of caption data within the DTV broadcast stream.

Digital Video Broadcasting

A set of international open standards for digital television and data broadcasting. It defines transmission systems for terrestrial, satellite, cable, and mobile delivery, enabling efficient delivery of multimedia content. In 3GPP, it's integrated to support broadcast/multicast services.

Distributed Virtual Environment

A 3GPP Rel-19 concept for networked virtual environments distributed across multiple devices and edge servers, enabling immersive multi-user experiences with low latency and high consistency.

Enhanced Cell-ID

A network-based positioning method in LTE and 5G NR that enhances basic Cell-ID by incorporating additional radio measurements. It estimates a UE's location using the serving cell identity combined with timing advance, signal strength, and/or angle-of-arrival data, providing better accuracy than Cell-ID alone.

Emergency – Call Session Control Function

A core network function within the IMS that handles emergency session establishment and routing. It is responsible for determining the appropriate Public Safety Answering Point (PSAP) based on the user's location and service requirements, ensuring emergency calls are correctly processed even when normal services are unavailable.

Evolved Multimedia Broadcast Multicast Service

A point-to-multipoint service in LTE and 5G networks that efficiently delivers the same content (e.g., live TV, software updates) to multiple users simultaneously. It optimizes network resources by broadcasting over a common carrier instead of individual unicast streams.

Enhanced Observed Time Difference

A network-based positioning method for determining the geographic location of a mobile device. It calculates location by measuring the time difference of arrival of signals from multiple base stations. This technology is crucial for location-based services and emergency caller location.

Enhanced Observed Time Difference Assistance Data Message

A broadcast message that provides RTD and BTS coordinates to mobile stations for E-OTD positioning. It enables location calculation without GPS, supporting emergency and commercial location services.

Emergency SUPL Location Platform

A specialized location platform in 3GPP networks that supports emergency services by providing accurate positioning information for emergency calls. It integrates with SUPL to enable location-based services for public safety, ensuring rapid response in critical situations.

Emergency Session Transfer Number for DRVCC

A specific telephone number used in the IMS to route a session transfer request for an emergency call during Dual Radio Voice Call Continuity (DRVCC). It uniquely identifies the Emergency Access Transfer Control Function (E-ATCF) responsible for anchoring the emergency IMS session, enabling its transfer between packet-switched and circuit-switched access networks when a UE has dual radio capability.

Emergency Call Session Transfer Number – Single Radio

A dedicated telephone number used to transfer an emergency call session from a circuit-switched (CS) to a packet-switched (PS) domain for a UE with single radio capability. It enables continuity of emergency services during handovers between different access technologies, such as from LTE (PS) to 2G/3G (CS).

End-to-End

E2E refers to the complete path of a service or communication from the source user equipment to the destination endpoint, traversing all network domains. It is a fundamental architectural principle ensuring service continuity and performance guarantees across heterogeneous networks. This concept is critical for defining service level agreements and enabling complex services like network slicing.

Early Media

Media such as ringback tones, announcements, or IVR prompts sent before a communication session is fully established. Defined in 3GPP IMS supplementary service specifications 24.428, 24.528, and 24.628.

Enterprise Application Server

Enterprise Application Server (EAS) is a network function that hosts and executes enterprise-specific applications within a 5G system. It enables enterprises to deploy custom services close to their users, leveraging network capabilities like low latency and high bandwidth. This supports vertical industries and private network deployments.

Edge Application Server Discovery Function

The Edge Application Server Discovery Function (EASDF) is a 5G core network function that assists User Equipment in discovering and selecting optimal Edge Application Servers. It provides DNS-based resolution tailored for edge computing, enabling low-latency access to applications deployed at the network edge.

Emergency Access Transfer Function

A core network function that manages the transfer of emergency sessions, such as calls to emergency services (e.g., 911, 112), between different access networks or core network domains. It ensures emergency call continuity and reliability during handovers.

Elementary Basic Service Group

A concept from GSM/UMTS circuit-switched services representing a group of related telecommunication services (like voice, fax, data) that share common subscription and charging characteristics. It is a fundamental unit for service provisioning and billing in legacy networks.

European Broadcasting Union Timed Text

EBU-TT is a standardized XML-based format for representing subtitles and captions, referenced by 3GPP for delivery over mobile broadcast (eMBMS) and unicast streams. It provides precise timing, styling, and positioning of text, enabling professional, accessible subtitling for TV and video content delivered via 3GPP networks.

Emergency Call

An emergency call from a vehicle that automatically or manually transmits a Minimum Set of Data (MSD) to emergency services. It enables faster and more informed responses to road accidents.

eCall In-band Modem

A modem pair that transmits the eCall Minimum Set of Data (MSD) over the voice channel of an emergency call. It ensures reliable data transfer from the vehicle to the PSAP without additional data channels.

eCall Only Mode

A UE configuration that restricts the device to only perform eCall over IMS and limited test/reconfiguration calls. It prevents normal network signaling to avoid interference and ensure eCall availability.

Event Charging Function

The Event Charging Function (ECF) is a core component of the 3GPP Online Charging System (OCS). It processes charging events in real-time, interacting with network elements to authorize service usage based on user account balance. It enables prepaid services, spending limit controls, and immediate deduction of charges, forming the backbone of real-time revenue management.

Edge and Cloud Interworking

ECI is a framework for integrating edge computing platforms with central cloud infrastructures to enable low-latency, high-bandwidth applications. It defines the architecture and procedures for seamless service deployment and user plane routing between the edge and cloud.

Enhanced Circuit Switched Data

A GSM evolution technology that improved data rates over traditional circuit-switched connections. It enhanced the original Circuit Switched Data (CSD) service by using multiple time slots and advanced coding schemes, serving as a precursor to packet-switched GPRS/EDGE.

Edge Computing Service Provider

An entity that provides edge computing capabilities and services within the 3GPP framework. It enables low-latency applications by hosting applications closer to the user, which is critical for services like AR/VR, industrial IoT, and real-time analytics.

Explicit Communication Transfer

Explicit Communication Transfer (ECT) is a supplementary service in 3GPP networks that allows a user to explicitly transfer an ongoing communication (e.g., a voice call) to a third party. It provides a controlled and signaled method for call diversion, distinct from call waiting or conference calling. ECT is used for features like 'Call Transfer' or 'Consultation Hold and Transfer'.

Explicit Communication Transfer Session Identifier Uniform Resource Identifier

A Public Service Identity (PSI) created by an ECT Application Server that resolves to the AS itself, used to identify and manage Explicit Communication Transfer sessions within the IMS network.

Error Concealment Unit

The Error Concealment Unit (ECU) is a functional component in 3GPP networks that handles the mitigation of errors in transmitted media, such as voice or video. It is crucial for maintaining perceived quality of service (QoS) by intelligently masking or correcting errors introduced during transmission over unreliable channels, thereby enhancing user experience.

Edge Computing

A concept enabling operator and 3rd party services to be hosted close to the UE's access point of attachment, reducing end-to-end latency and transport network load. It is essential for low-latency and high-bandwidth applications in 5G.

Edge Application

EDGEAPP refers to edge applications in 3GPP, enabling services to be hosted at the network edge for low latency and high efficiency. It is part of 5G edge computing architecture, supporting URLLC and enhanced user experience.

Edge Data Network

A distributed computing architecture in 5G that deploys application servers and cloud resources at the network edge, close to the user. It enables ultra-low latency, high bandwidth, and localized data processing for services like AR/VR, industrial IoT, and real-time video analytics. It is a key enabler of mobile edge computing (MEC).

Event Detection Point

Event Detection Point (EDP) is a concept within the CAMEL (Customized Applications for Mobile network Enhanced Logic) and IMS (IP Multimedia Subsystem) service frameworks. It represents a specific point in a call or session state where a service control function can be notified or can request instructions, enabling intelligent, network-controlled services like prepaid billing and VPNs.

Event Detection Point - Notification

Event Detection Point - Notification (EDP-N) is a type of EDP where the service switching function notifies the service control function of an event but does not request instructions. The call processing continues uninterrupted, allowing for monitoring, charging, or logging without affecting call flow.

Event Detection Point - Request

Event Detection Point - Request (EDP-R) is a type of EDP where the service switching function notifies the service control function of an event and explicitly requests instructions. Call processing is suspended until a response is received, enabling real-time control over call routing, charging, and service execution.

Enhanced Dialled Services

Enhanced Dialled Services (EDS) is a 3GPP feature that provides advanced call handling and supplementary services beyond basic dialing. It enables network operators to offer richer telephony services, such as call forwarding with specific conditions, enhanced caller identification, and specialized call routing. This matters as it improves user experience and allows for more sophisticated, value-added telephony services within the core network.

Edge Enabler Client

The Edge Enabler Client (EEC) is a functional entity within a UE or application server that interacts with the Edge Enabler Server (EES) to access Edge Computing services. It discovers edge applications, provisions necessary information, and facilitates communication with applications hosted at the network edge.

Extended Emergency Number List Validity

A feature extending the validity period of the emergency number list stored on the UE. It ensures the UE can access emergency services even when it cannot contact the network to refresh the list, enhancing reliability in critical situations.

Edge Enablement Server

The Edge Enablement Server (EES) is a functional entity in 3GPP's Edge Computing architecture that provides service registration, discovery, and connectivity management for Edge Applications (EAs) and Edge Application Clients (EACs). It acts as a central broker, enabling applications to discover and utilize low-latency, high-bandwidth services offered by Edge Application Servers (EASs) deployed at the network edge. This is crucial for enabling use cases like AR/VR, industrial automation, and real-time video analytics.

Earth Exploration-Satellite Service

Earth Exploration-Satellite Service (EESS) is a radiocommunication service defined by the ITU-R for satellites that collect data about the Earth's environment, including weather, climate, oceanography, and land surface. In 3GPP, it refers to the use of terrestrial IMT (e.g., 5G NR) spectrum by satellite systems performing EESS functions, focusing on coexistence studies and regulatory aspects. It enables direct satellite-to-ground data transmission for environmental monitoring.

Earthquake Early Warning

Earthquake Early Warning (EEW) is a 3GPP standardized service that delivers rapid alerts to mobile devices upon detection of seismic activity. It leverages the cellular network's broadcast capabilities to provide critical seconds of warning, enabling public safety actions like taking cover. This service is vital for disaster preparedness and reducing earthquake-related casualties.

Edge Fading Amplitude Panning

Edge Fading Amplitude Panning (EFAP) is a 3GPP media processing function for immersive audio services, introduced in Release 18. It dynamically adjusts the audio signal levels between different speakers or audio objects to create a fading effect, enhancing spatial audio realism. It is a key component for delivering high-quality immersive media experiences like 360-degree video and extended reality (XR).

Effective priority

The priority decision determined by the transmission control server based on multiple input parameters, such as transmission priority, participant type, and call type, used in mission-critical push-to-talk (MCPTT) and related services.

Enhanced Full Rate speech codec

The Enhanced Full Rate (EFR) is a speech codec standard for GSM networks, providing significantly improved voice quality compared to the original Full Rate (FR) codec. It operates at 12.2 kbps and uses an Algebraic Code Excited Linear Prediction (ACELP) algorithm to deliver near-wireline quality audio. EFR was a major milestone in mobile voice services, enhancing user experience and becoming a benchmark for quality.

European Geostationary Navigation Overlay Service

A satellite-based augmentation system (SBAS) that improves the accuracy, integrity, and availability of GPS signals over Europe. It provides corrected positioning data for safety-critical applications like aviation.

Edge Hosting Environment

EHE is a standardized framework in 3GPP for deploying and managing applications at the network edge, close to users. It enables low-latency services, edge computing, and network exposure by providing a consistent environment for application hosting across operator networks, crucial for AR/VR, IoT, and industry 4.0.

Event Information Table

A data table used in Multimedia Broadcast/Multicast Service (MBMS) and evolved Multimedia Broadcast Multicast Service (eMBMS) to provide scheduling information for broadcast events. It lists the timing, duration, and identifiers for upcoming broadcast sessions, enabling efficient reception by User Equipment.

Echo Loss

Echo Loss (EL) is a key performance metric in 3GPP for voice quality, specifically measuring the attenuation of acoustic echo in a communication path. It is critical for ensuring clear, echo-free voice calls in mobile networks by quantifying the effectiveness of echo cancellation systems. Defined in the Ear Reference Point (ERP) context, it directly impacts user experience and service quality.

Electronic Message Association

EMA was an early 3GPP service framework for multimedia messaging, defining protocols for sending and receiving messages containing text, images, audio, and video. It provided a standardized alternative to proprietary MMS systems, enabling interoperability between different operators and handsets.

Encrypted Media Extensions

Encrypted Media Extensions (EME) is a 3GPP-defined framework for enabling the secure delivery and playback of encrypted media content, such as DRM-protected video, over mobile networks. It provides a standardized interface between web browsers and Content Decryption Modules (CDMs), ensuring content protection across diverse devices and platforms.

Extensible MultiModal Annotation markup language

EMMA is an XML-based markup language standardized by W3C and referenced by 3GPP for representing user input interpretations in multimodal systems. It allows applications to process inputs from various modalities like voice, keyboard, and pen in a unified format.

Enhanced Messaging Service

A standardized messaging service within 3GPP networks that extends beyond basic SMS. It enables the exchange of rich content like pictures, audio, video, and formatted text between users and applications, forming the basis for modern MMS. It is a core enabler for person-to-person and application-to-person multimedia communication.

Encoder Homing Frame (Speech Codec Test Signal)

An encoder homing frame is a precisely defined 160-sample test signal used in speech codec testing. It consists of 160 identical 13-bit samples with value 0008 hex, enabling deterministic codec verification.

End-User

An entity, typically a person, associated with one or more subscriptions through identities like IMSI, MSISDN, IMPI, or IMPU. It represents the ultimate consumer of 3GPP services and is characterized by an End-User Identity.

Edge Notification Server

The Edge Notification Server (ENS) is a network function introduced in 5G-Advanced to provide a generic notification delivery service. It enables applications to request and receive asynchronous notifications about events (e.g., location, connectivity status) for a group of UEs, optimizing communication by reducing the need for constant polling.

E.164 telephone NUmber Mapping

ENUM is a system that maps international telephone numbers (E.164) to Internet resources like URIs (e.g., SIP addresses) using the Domain Name System (DNS). It enables the interconnection and convergence of traditional telephony (PSTN) with IP-based communication services like VoIP and IMS.

Emergency Operations Center

A central coordination point for managing public safety communications during emergencies. It enables authorities to receive, process, and dispatch critical information, ensuring effective response coordination across different agencies and networks.

Electro-Optical Transfer Function

A mathematical function that defines the relationship between the electrical signal values in a video system and the corresponding optical luminance output on a display. It is fundamental for ensuring accurate color and brightness reproduction in multimedia services, particularly for High Dynamic Range (HDR) video.

EPC-level Proximity Services Discovery

A ProSe Discovery procedure where the Evolved Packet Core determines the proximity of two ProSe-enabled UEs and informs them. It enables network-controlled discovery for proximity-based services.

Electronic Program Guide

An Electronic Program Guide is a multimedia service that provides users with an interactive, menu-driven interface to browse, search, and schedule upcoming broadcast and on-demand content. It displays program metadata such as titles, descriptions, schedules, and ratings. In 3GPP, it is standardized for delivery over MBMS, enabling efficient broadcast of guide data to many users.

Echo Return Loss

ERL is a metric that measures the attenuation of echo signals in voice communication systems, quantifying how much the echo is reduced between the receive and transmit paths. It is critical for voice quality assessment, ensuring clear conversations by minimizing disruptive echoes. High ERL values indicate better echo cancellation performance.

Echo Return Loss Enhancement

ERLE is a key performance metric in 3GPP voice quality testing that quantifies the effectiveness of an acoustic echo canceller (AEC). It measures the reduction in echo level achieved by the AEC system, directly impacting the perceived clarity and quality of voice calls in mobile networks. High ERLE values are critical for ensuring natural, echo-free conversations, especially in hands-free and speakerphone scenarios.

Enterprise Systems

Refers to the collection of network functions, architectures, and service enablers designed to provide customized, secure, and isolated communication services for enterprise customers within public mobile networks. It enables features like private networks, network slicing for enterprises, and enhanced API exposure.

Event State Compositor

A functional entity within the IP Multimedia Subsystem (IMS) that manages and composes event state information for presence and other event-based services. It aggregates information from multiple sources to create a coherent, composite view of a user's state (like availability or mood) for watchers. This is crucial for enabling rich presence, messaging, and group communication services in IMS.

Electronic Service Guide

The Electronic Service Guide (ESG) is a structured data service that provides users with information about available broadcast and multicast services, such as mobile TV. It enables service discovery, content navigation, and program scheduling, acting as an electronic program guide for mobile networks.

Emergency Service Query Key

A temporary identifier used to correlate an emergency call with location and subscriber data in the IP Multimedia Subsystem (IMS). It is crucial for routing emergency calls to the correct Public Safety Answering Point (PSAP) and providing dispatchers with accurate caller location information, which is vital for timely emergency response.

Emergency Service Routing Key

A key used in North American emergency call systems (E911) to route wireless calls to the appropriate Public Safety Answering Point (PSAP). It identifies the cell site and sector from which the call originated, enabling initial, coarse routing before precise location is determined.

Emergency Service Routing Number

A globally unique number used to route emergency calls to the appropriate Public Safety Answering Point (PSAP). It is a critical component of IP Multimedia Subsystem (IMS) emergency services, ensuring that emergency calls are correctly identified and directed based on the caller's location, even when the caller's identity or subscription is unknown or invalid.

Essential User Equipment Requirement (Conditional)

A 3GPP requirement that must be implemented in a UE under certain service conditions, such as supporting a specific codec when a particular service (e.g., speech) is offered.

European Telecommunications Numbering Space

A harmonized numbering range (+388) defined for pan-European telecommunications services. It provides a single, recognizable number format for services operating across multiple European countries, distinct from national numbering plans.

Earthquake and Tsunami Warning System

ETWS is a 3GPP public warning system that delivers earthquake and tsunami alerts to mobile users in affected areas. It enables rapid, area-specific dissemination of emergency notifications via cellular networks.

European Union Alert

EU-Alert is a Public Warning System (PWS) that delivers warning notifications to mobile users in the European Union. It uses the same access stratum mechanisms as CMAS to broadcast emergency alerts efficiently across LTE and 5G networks.

Essential Video Coding

A video compression standard developed by MPEG and adopted by 3GPP for efficient media delivery over mobile networks. It provides significantly better compression than its predecessor, HEVC, enabling higher quality video streaming at lower bitrates, which is critical for bandwidth-constrained scenarios.

Enhanced Validity Period Format

A format for specifying message validity periods in SMS, offering finer granularity and extended range compared to the original Validity Period Format (VPF). It enables more precise control over message delivery timing and storage in the network, improving SMS service reliability and user experience.

Enhanced Voice Services

A 3GPP standardized codec suite for high-quality, robust, and bandwidth-efficient voice services, including super-wideband and fullband audio. It provides superior voice quality, especially in challenging radio conditions, and is a key component for VoLTE, VoNR, and other IMS-based voice services.

Enhanced Voice Services Adaptive Multi-Rate Wideband Interoperable Mode

The EVS AMR-WB IO mode is a codec mode within Enhanced Voice Services that ensures bitstream interoperability with the legacy AMR-WB codec. It includes 9 codec modes and a SID frame, enabling seamless interworking between EVS and AMR-WB networks.

Enhanced Voice Services Primary Mode

The EVS Primary mode is the native operating mode of the EVS codec, offering 11 bit-rates for fixed/multi-rate and variable bit-rate operation, plus a SID bit-rate. It supports narrowband to fullband audio but is not interoperable with AMR-WB.

EVS Codec Mode Request

A control mechanism used during an EVS-encoded voice call to dynamically request a change in the transmitting endpoint's codec configuration (e.g., bitrate, bandwidth, mode). This enables real-time adaptation to changing network conditions (like congestion) or to optimize for power consumption, maintaining the best possible voice quality.

Enhanced Voice Services Silence Insertion Descriptor

A specific Silence Insertion Descriptor (SID) used within the Enhanced Voice Services (EVS) codec for discontinuous transmission (DTX). It provides a compact, efficient representation of silence and background noise during speech pauses, crucial for maintaining high audio quality while conserving bandwidth in voice calls.

Exclusive Access

A mode of network access where only defined Licensed Shared Access (LSA) subscribers can connect to exclusive access cells. It enables closed subscriber groups for LSA spectrum, ensuring that only authorized users utilize the shared frequencies.

Exchangeable Image File Format

A standard format for storing metadata (like camera settings, GPS location, date/time) within image files, notably JPEGs. In 3GPP, it's referenced for multimedia messaging (MMS) and media file handling, ensuring interoperability for image information exchange across devices and networks.

Flexible Alerting

Flexible Alerting (FA) is a supplementary service that allows a single incoming call to alert multiple terminals or user identities simultaneously or sequentially. It is crucial for business and group communication, ensuring calls reach available members, enhancing connectivity and operational efficiency.

Facial Action Coding System

FACS is a standardized system for describing facial movements, adopted in 3GPP for advanced emotion recognition and affective computing services. It enables precise coding of facial expressions for immersive and interactive applications.

Fallback

Fallback is a service selection mechanism where, if two services (e.g., multimedia and speech) are proposed but only one is available or desired, the available service is selected and the other is discarded. It ensures service continuity by prioritizing availability over preference.

Flow Based bearer Charging

A charging mechanism in 3GPP packet core networks where billing is based on individual IP data flows or service data flows rather than the entire bearer. It enables granular, service-aware charging by correlating usage with specific applications, content, or QoS levels.

Furnish Charging Information

Furnish Charging Information (FCI) is a Diameter-based protocol operation used in the 3GPP Online Charging System (OCS). It is a specific command within the Ro reference point where the OCS provides authorized charging information, such as granted service units (time, volume, money) and associated rating data, to the network element (e.g., CTF) requesting quota for a subscriber's service session.

Feature Compression for Machines

FCM is a 3GPP Release 19 feature that enables efficient compression of machine learning features for transmission between network functions, reducing bandwidth and latency for AI/ML-based services in 5G and beyond.

File Distribution

File Distribution is a service capability within 3GPP architectures, notably for Proximity Services (ProSe) and V2X, that enables the efficient broadcast or multicast of files to a group of user equipments or vehicles. It supports use cases like software updates, multimedia content distribution, and cooperative perception in vehicular networks.

Fixed Dialling Number

A subscriber service allowing only calls to a pre-defined list of numbers, restricting outgoing calls. It is used for parental control, corporate phone management, and cost control by preventing unauthorized or premium-rate calls. Managed via the USIM and enforced by the mobile equipment.

FLUTE File Delivery Table

The FDT is a structured metadata table used in the FLUTE (File Delivery over Unidirectional Transport) protocol to describe files being delivered in a broadcast or multicast session. It provides essential information like file location, size, and content encoding, enabling efficient and reliable file delivery over 3GPP MBMS and eMBMS networks. It is critical for services like software updates, media distribution, and public warning systems.

Far End Camera Control

A protocol and capability within the Multimedia Telephony Service for IMS (MTSI) that allows a remote participant in a video call to control the orientation (pan, tilt, zoom) of the far-end user's camera. It enhances video conferencing by enabling dynamic view adjustment without local user intervention.

Feedback Frame

A downlink transmission interval in 3GPP speech codec specifications containing feedback data, spanning 140 ms or 1120 samples at 8 kHz sampling rate. It is critical for adaptive multi-rate codec operation and error resilience in circuit-switched and packet-switched voice services.

Follow Me function node

A network function defined in 3GPP Release 4 for supporting the Follow Me service, which allows a user to have a single, location-independent number. It manages call routing and service logic to forward communications to the user's current location, enabling personal mobility.

Full High Definition

A video resolution standard of 1920x1080 pixels, standardized by 3GPP for multimedia services. It defines quality requirements for video streaming, broadcasting, and conversational services over mobile networks, ensuring a consistent high-quality user experience.

First-to-answer call

An MCPTT group call that is established when the first among multiple potential target recipients manually answers. Automatic answer is prohibited, ensuring deliberate user participation before the call is set up.

Fixed codebook

A non-adaptive set of excitation vectors used by speech synthesis filters in codecs such as AMR and AMR-WB. In AMR-WB it is realised as an algebraic codebook, enabling efficient speech coding.

Fused Location Service

FLS is a 3GPP Release 19 service that combines multiple positioning methods and sensor data to provide highly accurate and reliable location information for 5G and beyond networks.

Framework for Live Uplink Streaming

The Framework for Live Uplink Streaming (FLUS) is a 3GPP service enabler that standardizes the uplink of live media (audio/video) from a user's device to a network application or content provider. It provides mechanisms for session establishment, media ingestion, quality control, and network assistance. FLUS is essential for enabling professional-grade live streaming applications, such as social media live broadcasting, live news reporting, and real-time event coverage over mobile networks.

FLUS session

A logical association between a FLUS source and a FLUS sink within which media content can be sent from the source to the sink. It underpins flexible media handling in 3GPP media services.

File Delivery over Unidirectional Transport

File Delivery over Unidirectional Transport (FLUTE) is a protocol for efficiently delivering files and data to a large number of receivers over unidirectional, broadcast, or multicast networks. It is a cornerstone of 3GPP Multimedia Broadcast/Multicast Service (MBMS) and evolved MBMS (eMBMS). FLUTE enables reliable, scalable content distribution like software updates, emergency alerts, and live video streaming to massive audiences without overloading unicast networks.

Fixed Mobile Convergence

Fixed Mobile Convergence (FMC) is a service framework that integrates fixed (e.g., broadband) and mobile networks to provide seamless user experiences. It enables consistent services across different access technologies, improving convenience and network efficiency.

Flexible Mobile Service Steering

A network capability that dynamically steers user traffic to the most appropriate access network (e.g., 3GPP, non-3GPP like Wi-Fi) based on policies, conditions, and service requirements. It optimizes user experience and network resource utilization across heterogeneous networks.

First Order Ambisonics

A spatial audio format standardized by 3GPP for immersive media services like VR and 360° video. It represents a sound field using four audio channels (W, X, Y, Z), enabling a full-sphere, rotationally invariant listening experience. This is key for realistic audio in augmented and virtual reality applications.

Forwarded Multimedia Message

A Multimedia Message originally sent to an intended recipient that is subsequently forwarded to additional recipients, with delivery and read-reply reports potentially referencing the forwarded copy.

Forwarding MMS User Agent

An MMS User Agent that acts as the intended recipient of a Multimedia Message and requests its forwarding to other recipients without needing to first download the message content.

Field of View

Field of View (FOV) defines the extent of the observable environment that can be captured by a camera or sensor, measured as an angular width. In 3GPP, it is a critical parameter for immersive media services like augmented reality (AR), virtual reality (VR), and multi-view video, impacting bandwidth and quality requirements.

Fixed Part Subscriber Identity Module

A GSM Phase 2+ SIM card with additional data for CTS (Cordless Telephony System) operation, inserted into the CTS Fixed Part Equipment (CTS-FPE). It enables licensed-band cordless telephony by authenticating the fixed base station.

Frame Quality Indication (AMR-WBIF1)

A parameter in the AMR-WB (Adaptive Multi-Rate Wideband) speech codec that indicates the quality or validity of a received speech frame. It is used by the receiving end to assess frame integrity and guide error concealment strategies, ensuring robust voice quality over error-prone radio channels.

Full Rate

Full Rate (FR) is a speech codec mode defined in GSM that provides the standard voice channel bit rate of 13 kbps. It represents the original and most widely used speech coding standard for GSM voice calls, offering a balance between voice quality and spectral efficiency. FR is fundamental to the basic telephony service in 2G networks.

Future Railway Mobile Communication System

The 3GPP-standardized successor to GSM-R, providing mission-critical voice and data services for railway operations. It leverages 4G/5G technologies to enable advanced applications like automated train control, video surveillance, and real-time data exchange, ensuring safety and efficiency.

Fixed Satellite Service

FSS refers to satellite communication services that provide connectivity between fixed points on Earth, such as ground stations and user terminals, using geostationary or non-geostationary satellites. In 3GPP, it enables the integration of satellite networks with 5G systems to extend coverage to remote areas, support backhaul, and enhance resilience, forming part of non-terrestrial networks (NTN).

Fine Time Assistance

A positioning method where a location server provides precise timing information related to cellular base stations to a User Equipment (UE) to enhance the accuracy of its own position calculation. It is a network-assisted technology that improves the performance of Observed Time Difference of Arrival (OTDOA) positioning in LTE and 5G NR.

Forwarded To Number

A parameter used in call forwarding supplementary services within GSM/UMTS networks. It stores the telephone number to which a call is redirected when a forwarding condition (like busy or no reply) is met. It is a fundamental component for implementing flexible call handling and user mobility.

Forwarded-To NetWork

A network identifier parameter used in call forwarding services, particularly for Optimal Routing (OR) and Camel. It specifies the network (e.g., a PLMN) to which a call is forwarded, rather than a specific subscriber number. This aids in efficient inter-network routing and service triggering.

Full Interactive Connectivity Establishment

Full ICE refers to the complete implementation of the Interactive Connectivity Establishment (ICE) protocol as specified in IETF RFC 5245 (later RFC 8445). It is used in 3GPP networks to enable NAT traversal for real-time communications.

Fixed Wireless Access

A service that uses cellular network radio technology (like 4G LTE or 5G NR) to provide broadband internet access to fixed locations, such as homes and businesses. It serves as an alternative to wired connections like fiber or DSL, enabling rapid deployment of high-speed internet.

Geometry-based Point Cloud Compression

A compression standard for 3D point cloud data, developed by 3GPP for immersive media and XR applications. It efficiently encodes geometric and attribute information of point clouds, enabling high-quality streaming and storage while reducing bandwidth requirements for services like AR/VR and autonomous driving.

Generic Access - Circuit Switched Resources

A component of the Generic Access Network (GAN) / UMA standard that enables a mobile device to access traditional GSM circuit-switched services (like voice and SMS) over an unlicensed wireless IP network (e.g., Wi-Fi). It extends cellular coverage indoors.

Generic Access - Packet Switched Resources

A component of the Generic Access Network (GAN) that enables a mobile device to access GPRS/UMTS packet-switched data services over an unlicensed wireless IP network (e.g., Wi-Fi). It integrates Wi-Fi data access with the mobile core for authentication and billing.

Universal Geographical Area Description

A standardized format for describing geographical areas in 3GPP networks. It enables location-based services by providing a common language to define regions, zones, or points for network applications and user equipment.

GPS Aided Geo Augmented Navigation

A satellite-based augmentation system (SBAS) that improves the accuracy, integrity, and availability of GPS signals for aviation and other precision applications. It provides corrected positioning data to enhance navigation safety.

Galileo and Additional Navigation Satellite Systems

Galileo and Additional Navigation Satellite Systems (GANSS) is a 3GPP feature that enables User Equipment (UE) to utilize multiple Global Navigation Satellite Systems (GNSS) beyond the primary GPS system for location-based services. It supports Galileo, GLONASS, BeiDou, and QZSS, providing improved accuracy, availability, and reliability for positioning, especially in challenging urban or indoor environments. This is critical for emergency services (E911), navigation, and various IoT applications.

Ground Based Detect and Avoid for an Area

GBDAAA (Ground Based Detect and Avoid for an Area) is a Rel-19 3GPP enabler that allows ground-based sensing to detect non-cooperative intruders and provide avoidance information to aerial UEs. It supports safe beyond-visual-line-of-sight drone operations by integrating terrestrial detection with cellular connectivity.

General Bearer Services

A foundational concept in early GSM/UMTS defining the basic types of data transport connections (bearers) the network provides to users. It categorizes services based on fundamental characteristics like connection mode and bit rate. This matters as it established the core service model for circuit-switched and packet-switched data in 2G/3G networks.

Group Call Attributes

Group Call Attributes (GCA) are a set of parameters defined for the Voice Group Call Service (VGCS) and Voice Broadcast Service (VBS) in GSM. They characterize a group call, including its identity, priority, ciphering mode, and talker arbitration rules. These attributes are essential for setting up and managing group communication for professional users like public safety and taxi fleets.

GPRS Charging Identifier

The GPRS Charging Identifier (GCID) is a unique identifier assigned to each Packet Data Protocol (PDP) context or data session in GPRS, UMTS, and EPS networks. It is used by charging systems to correlate charging data records (CDRs) generated by different network nodes for the same user session, ensuring accurate billing.

AS Group Communication Service Enabler Application Server

An Application Server (AS) that enables group communication services like Mission Critical Push-to-Talk (MCPTT) over LTE/5G. It manages group calls, membership, and floor control, providing efficient one-to-many communication for public safety and commercial use cases.

Gradual Decoding Refresh

Gradual Decoding Refresh (GDR) is a video coding technique used in 3GPP's Enhanced Voice Services (EVS) codec and video codecs to enable seamless switching between different media streams or recovery from packet loss without requiring a full keyframe (Instantaneous Decoding Refresh - IDR). It allows a decoder to gradually refresh its picture buffer using a series of specially coded frames, reducing the bitrate spike and latency associated with sending a complete intra-coded frame. This is crucial for maintaining high-quality, low-latency video and voice services over unreliable networks like mobile cellular systems.

Geographical routing

Geographical routing converts a PDU's geographical area definition into an equivalent radio coverage map, enabling broadcast messages to be delivered only to the intended area. It is essential for cell broadcast and public warning services.

Graphics Interchange Format

A standardized image format for multimedia services in 3GPP networks, enabling efficient transmission and display of graphics and simple animations. It is defined to ensure interoperability for visual content in messaging and multimedia applications.

Group and List Management Server

The GLMS is a network element in the IP Multimedia Subsystem (IMS) that manages group definitions and user lists for services like instant messaging and presence. It enables users to create, modify, and store contact groups and authorization lists, which are essential for controlling service access and information sharing. This server is a foundational component for enabling rich, group-based communication services within the IMS framework.

Group Management Client

A functional entity within a UE that manages group-related services and configurations. It handles group membership, policy reception, and service authorization for group communications, enabling efficient group-based operations in 3GPP networks.

Group Message Delivery

A service capability that enables efficient delivery of messages to a group of users or devices. It optimizes network resources by using group addressing and delivery mechanisms, supporting applications like IoT, public alerts, and mission-critical communications.

Global Multimedia Mobility

A 3GPP service concept focused on enabling seamless multimedia session continuity and mobility across heterogeneous networks. It allows users to maintain active multimedia sessions (e.g., voice, video) while moving between different access technologies, such as from LTE to Wi-Fi, ensuring quality of service and user experience without interruption.

Group Management Server

A core network function for managing group communication services, such as Mission Critical Push-to-Talk (MCPTT). It handles group membership, configuration, and service authorization, enabling efficient group-based communication for public safety and professional users.

Group Of Blocks

GOB is a structural unit in video coding, specifically in the ITU-T H.263 and related codecs, representing a group of macroblocks within a video frame. In 3GPP, it's relevant for specifying multimedia telephony service interoperability and video codec requirements for conversational services.

Good speech frame

A good traffic frame that is not an accepted SID frame. Used in speech codec handling to distinguish valid speech frames from silence descriptor frames.

Group Of Pictures

GOP is a fundamental sequence structure in video compression (e.g., MPEG, H.26x), consisting of an I-frame followed by P- and B-frames. It defines the pattern of intra- and inter-frame coding, balancing compression efficiency, random access, and error resilience, crucial for 3GPP multimedia streaming and broadcast services.

Generic Push Layer

The Generic Push Layer (GPL) is a standardized service layer defined by 3GPP to enable the reliable and secure delivery of push notifications and messages to mobile devices. It provides a common framework for push-based services, abstracting underlying network details and ensuring interoperability across different operators and service providers.

General Packet Radio Service Mobile Station

A Mobile Station capable of GPRS services, enabling packet-switched data transmission in GSM networks. It is a key enabler for mobile internet and always-on connectivity.

GPRS CAMEL Subscription Information

A CAMEL subscription data set for GPRS networks, enabling intelligent network services like prepaid charging and location-based services for packet-switched data. It allows the network to apply service logic controlled by an external SCP during a GPRS session.

Global Positioning System Assistance Data Message

A broadcast message containing GPS differential corrections that enables mobile stations to calculate more accurate location estimates. It is part of assisted GPS (A-GPS) in GERAN.

Graphics Processing Unit

A specialized hardware processor designed for parallel computation, crucial for rendering graphics and accelerating multimedia services in 3GPP networks. In 3GPP context, it enables advanced services like cloud gaming, extended reality (XR), and immersive media by offloading complex rendering tasks from the device to the network edge or cloud.

Group

A set of members allowed to participate in the group call service, defined by rules that identify a collection of members implicitly or explicitly. It enables efficient one-to-many communication and management of users for group-based services.

Group call

The relationship between members of a group for transferring data, enabling one-to-many communication. It establishes an active group and allows multiple group calls within a group.

Group Call Area

A predefined geographic area composed of one or more cells used to distribute a Voice Broadcast Service (VBS) group call. It defines the coverage zone where all group members can receive the call.

Group Call Initiator

A member or authorized third party who initiates a group call. Multiple members can be authorized to initiate calls for the same group.

Group Call Member

A service subscriber or dispatcher actively participating in an ongoing voice group call. It defines the eligibility and role of users within mission-critical push-to-talk and group communication services.

Group Call Participant

A member of a group who is actively participating in a particular group call at a given time. It is synonymous with group call member but used in different specifications.

Group Call Server

A logical entity in 3GPP networks that provides group call services to members, enabling one-to-many communication. It manages group membership, call setup, and media distribution for push-to-talk and broadcast services.

Group Call Service

A point-to-multipoint service where a single data unit from one source is received by multiple destination participants, forming a one-in, many-out communication model. It enables efficient group communication in cellular networks.

Group Communication

Group Communication enables one-to-many or many-to-many communication among members of a defined group, forming the foundation for mission-critical push-to-talk, video, and data services in 3GPP networks.

Group Controller

The Group Controller is the member or third party responsible for creating and managing a group, including controlling membership and group policies in 3GPP group communication services.

Group Document

A Group Document is a structured data record within the Group Management Server (GMS) that defines a group's membership, policies, and configuration for mission-critical services.

Group Members

Service subscribers entitled to belong to a particular group classified by a certain group identification (group ID). They are the authorized participants in group communication services such as VGCS and VBS.

GSM Enhanced Full Rate Speech Codec

A speech coding standard defined in 3GPP TS 26.093 that provides significantly improved voice quality over the original GSM Full Rate (FR) codec. It uses advanced Algebraic Code Excited Linear Prediction (ACELP) algorithms to deliver near-wireline quality audio within the same GSM traffic channel bitrate.

Global System for Mobile Communications – Rail(way)

A specialized GSM-based mobile communication system designed for railway operations. It provides mission-critical voice and data services for train control, dispatching, and trackside maintenance, ensuring safety and operational efficiency in rail environments.

Global Text Telephony

Global Text Telephony (GTT) is a 3GPP feature enabling real-time text conversation within any 3GPP conversational service, such as voice calls. It provides an accessible communication method, crucial for users with hearing or speech impairments, by integrating text seamlessly into the conversational multimedia telephony framework.

Global Text Telephony Feature Environment

The Global Text Telephony Feature Environment (GTTFE) defines the specific network components, functions, and interfaces required to implement the GTT service. It provides a standardized architectural framework ensuring consistent deployment and interoperability of real-time text capabilities across 3GPP networks.

Global Virtual Network Service

A service framework enabling seamless global roaming and service continuity across 3GPP and non-3GPP access networks. It provides a unified service experience for users by abstracting network complexities, ensuring consistent service delivery regardless of location or access technology.

Home Edge Enabler Server

The Home Edge Enabler Server (H-EES) is a network function introduced in 3GPP Release 18 to manage and orchestrate edge computing applications and services for roaming users. It resides in the user's Home Public Land Mobile Network (HPLMN) and coordinates with the Visited Edge Enabler Server (V-EES) in the visited network to enable consistent edge service delivery. This is crucial for low-latency applications like AR/VR and industrial IoT, ensuring service continuity and optimal performance regardless of user location.

Home-Gateway Mobile Location Centre

The Home-Gateway Mobile Location Centre (H-GMLC) is a core network entity that acts as the primary gateway in a user's home network for location-based service requests. It receives location requests from external Location Service Clients (LCS clients), authenticates and authorizes them, and then forwards the requests to the appropriate network (home or visited) to obtain the user's position. It is fundamental for emergency services, lawful interception, and commercial location-based applications.

High-Accuracy GNSS

High-Accuracy GNSS (HA) is a 3GPP service providing precise positioning using techniques like Real-Time Kinematic (RTK) and Precise Point Positioning (PPP). It delivers centimeter-level accuracy, enabling critical applications such as autonomous driving, drone navigation, and industrial IoT. This service is essential for location-based services requiring precision beyond standard GNSS.

Hangover period

The hangover period is a set of frames appended to the end of a speech burst during which the voice activity detection (VAD) flag is set to 0 but the transmit type remains SPEECH_GOOD. It provides the speech encoder with additional samples to accurately derive comfort noise parameters.

Hypermedia As The Engine Of Application State

A constraint of the REST architectural style where a client interacts with a network application entirely through hypermedia (links) provided dynamically by the server. In 3GPP, it guides the design of service-based interfaces (e.g., Nnrf, Namf) in the 5G Core, enabling loose coupling and discoverability between network functions.

Hear Carry Over

HCO is a feature enabling a user to alternately receive speech and transmit text, primarily for accessibility services like text telephony. It allows seamless switching between listening and typing, facilitating real-time communication for users with hearing or speech impairments. This ensures inclusive communication services in mobile networks.

High Definition

High Definition (HD) refers to a set of stringent Quality of Service (QoS) requirements for media delivery, particularly video and audio, within 3GPP networks. It ensures a superior user experience characterized by high resolution, frame rate, and low latency for multimedia services. This concept is crucial for enabling premium services like mobile TV, video conferencing, and ultra-high-definition streaming.

High Dynamic Range

HDR is a video technology standard that expands the contrast ratio and color gamut beyond standard dynamic range (SDR). It provides greater detail in highlights and shadows and more vibrant colors, significantly enhancing the visual quality of multimedia services over mobile networks. This is crucial for delivering premium video experiences like 4K/8K streaming and immersive media.

High-definition television

HDTV refers to television services with significantly higher resolution than standard definition (SD), typically 720p or 1080i/p. In 3GPP, it encompasses the delivery of high-definition video content over mobile networks, leveraging efficient codecs and adaptive streaming. It is a foundational service for mobile TV and video-on-demand, driving data consumption and network capabilities.

High Definition Video Conference

HDVC is a 3GPP service enabling high-definition video conferencing over mobile networks. It specifies requirements for real-time, bidirectional HD video and audio communication with low latency and high reliability. This technology is essential for professional mobile collaboration, telemedicine, and enterprise communications, leveraging the capabilities of IMS and 5G.

Home Environment

The Home Environment is the administrative domain of a user's service provider, managing their subscription, service profiles, and authentication. It is a foundational concept for service personalization, roaming, and security, enabling consistent user experiences across different visited networks.

Home Environment Value Added Service Provider

A Value Added Service Provider that has an agreement with the Home Environment to provide services to users in a managed, transparent way. It enables multiple providers to offer services through the home network.

Hosted Enterprise Services

HES is a 3GPP framework enabling mobile network operators to host and provide enterprise-centric communication services over their infrastructure. It allows enterprises to offer customized voice, messaging, and data services to their employees using the operator's core network capabilities.

High Efficiency Video Coding

HEVC (H.265) is a video compression standard that doubles the data compression ratio compared to its predecessor AVC (H.264). It enables the delivery of high-quality video, including 4K and 8K content, over bandwidth-constrained mobile networks. This is crucial for efficient video streaming services in 3GPP systems.

Higher Frame Rates

Higher Frame Rates (HFR) refer to video content with frame rates significantly above the conventional 24-30 fps, such as 60, 100, or 120 frames per second, standardized by 3GPP for enhanced media services. HFR provides smoother motion, reduced blur, and improved visual quality, particularly for fast-action sports, gaming, and virtual reality applications delivered over mobile networks.

Hand-held Speakerphone

Hand-held Speakerphone (HHS), also known as hand-held hands-free, is a voice communication mode where a user holds the device but uses its built-in loudspeaker and microphone for audio, rather than holding it to the ear. It is a standardized service feature in 3GPP that defines the acoustic and signal processing requirements for this mode. This enables clear, full-duplex conversation without a headset, important for convenience and safe in-car use.

Hybrid Log Gamma

A high dynamic range (HDR) video standard supported in 3GPP for media delivery over mobile networks. It combines a perceptual quantizer (PQ) curve for high luminance with a gamma curve for standard dynamic range compatibility, enabling richer contrast and color for video services like streaming and broadcasting.

HTTP Live Streaming

HTTP Live Streaming (HLS) is an adaptive bitrate streaming communications protocol developed by Apple and later standardized for multimedia delivery over IP networks. It works by breaking a stream into a sequence of small HTTP-based file downloads, allowing seamless quality adaptation based on network conditions. It is a dominant protocol for video delivery on the internet and in mobile networks.

Head Mounted Display

A Head Mounted Display (HMD) is a wearable device that presents visual media, often for Virtual Reality (VR) or Augmented Reality (AR). In 3GPP, specifications address HMD-specific requirements for media delivery, power efficiency, and low-lency streaming over mobile networks. This enables high-quality immersive experiences on wireless devices.

Hazardously Misleading Information

Information that is inaccurate or deceptive and could lead to harmful actions or decisions, posing risks to safety, security, or public trust. In telecommunications, HMI is a critical concern for services like public warning systems, emergency communications, and location-based services. Managing HMI is essential to ensure reliable and trustworthy network services.

Higher Order Ambisonics

Higher Order Ambisonics (HOA) is an advanced spatial audio format for immersive media, capturing and reproducing a full 360-degree sound field. Standardized by 3GPP for services like VR and AR, it enables realistic, object-based audio experiences over mobile networks.

Higher-Order Ambisonics (2nd order)

HOA2 is a specific implementation of Higher Order Ambisonics using 2nd order spherical harmonics, offering improved spatial audio accuracy over 1st order. It provides a better balance between audio quality and data rate for immersive services like VR streaming over 5G networks.

Communication session Hold

A supplementary service that allows a participant in a call (voice or multimedia) to temporarily suspend the media transmission and reception, placing the remote party on hold. The signaling connection remains active, allowing the held party to hear optional hold tone/music and for the session to be retrieved later. It is a fundamental telephony feature standardized for IMS and CS networks.

Hosting Service Centralization and Continuity Application Server

The SCC AS that manages the dialog with the remote party for a Collaborative Session. It anchors the session and coordinates media flows across multiple devices in IMS.

Half Rate

GSM Half Rate (HR) is a speech codec and channel mode that halves the bit rate needed for a voice call compared to Full Rate, effectively doubling network capacity. It uses a vocoder operating at approximately 5.6 kbps to provide acceptable voice quality with higher spectral efficiency, a crucial feature for early GSM network expansion.

Head-Related Room Impulse Response

A data model for spatial audio rendering in Extended Reality (XR) and immersive media services. It combines Head-Related Transfer Functions (HRTF) with room acoustics to simulate how sound arrives at a listener's ears from a specific point in a virtual space, enabling realistic 3D audio experiences over 5G networks.

Head-Related Transfer Function

HRTF is a mathematical function that describes how sound from a point in space is filtered by the shape of a listener's head, ears, and torso before reaching the eardrum. In 3GPP, it is standardized for creating immersive, spatial audio experiences, such as 3D audio and binaural rendering, in multimedia services like enhanced voice services and virtual reality.

High Speed Circuit Switched Data

A circuit-switched data service for GSM networks that increases data rates by allowing a mobile station to use multiple time slots simultaneously within a TDMA frame. It was an early enhancement to provide higher-speed data before the advent of packet-switched GPRS and EDGE.

HTTP Streaming and Download

A 3GPP service enabler standardizing the delivery of multimedia content over HTTP. It defines protocols for adaptive bitrate streaming and progressive download, ensuring efficient media delivery over mobile networks. This is foundational for services like mobile TV and video-on-demand.

HyperText Markup Language

The standard markup language for creating web pages and web applications, referenced within 3GPP specifications. It defines the structure and presentation of content delivered over mobile networks, enabling the rich multimedia user experience of the mobile internet.

Hyper-Text Mark-up Language 5

HTML5 is the fifth major revision of the HTML standard used for structuring and presenting content on the web. In 3GPP, it enables advanced web-based services and applications on mobile devices and within 5G service frameworks.

Heads-Up Display

Heads-Up Display (HUD) refers to a service or application scenario where information is projected into a user's field of view, typically in vehicles. 3GPP studies its requirements to enable low-latency, high-reliability wireless connectivity for such augmented reality services.

Interworking Wireless Local Area Network

I-WLAN refers to the 3GPP standardized architecture and procedures for interworking between 3GPP cellular networks (like GSM, UMTS, LTE) and Wireless Local Area Networks (WLANs, e.g., Wi-Fi). It enables seamless access to 3GPP packet-switched services and core network features via WLAN access, including authentication, authorization, charging, and service continuity. This was a foundational step towards non-3GPP access integration.

Incoming Access (Closed User Group Supplementary Service)

A Closed User Group (CUG) Supplementary Service feature in GSM/UMTS that permits or restricts a subscriber's ability to receive incoming calls. It works in conjunction with other CUG features to define a private calling network, allowing an operator to control whether members can receive calls from users outside their designated group.

Immediate Active Codec Set

A set of speech codecs that a mobile network can immediately use for a voice call without requiring further negotiation or capability exchange. It enables faster call setup and efficient fallback for services like Circuit-Switched FallBack (CSFB) in LTE and 5G.

Inter-Channel BandWidth Extension

A codec enhancement feature introduced in 3GPP Release 18 for the EVS codec. It artificially extends the audio bandwidth of narrowband or wideband speech signals to provide a fuller, more natural sound quality, improving the perceived audio experience in voice services.

Incoming Calls Barred (within the CUG)

A supplementary service that allows a subscriber within a Closed User Group (CUG) to bar incoming calls from outside the group. It enforces group privacy and controlled communication, ensuring only authorized internal calls are received.

Interactivity Connectivity Establishment

A framework defined by 3GPP for establishing interactive media sessions, such as voice and video calls, across diverse network environments. It is based on and extends the IETF's Interactive Connectivity Establishment (ICE) methodology to ensure robust NAT and firewall traversal for IP-based real-time communications.

In-Call Modification

A service capability that allows active communication sessions (like voice or video calls) to be modified without dropping the call. It enables users or the network to change session parameters, such as adding a video stream, changing codec, or adding another participant to create a conference.

Internet Content Provider

An entity that provides content, applications, or services over the Internet, such as streaming video, web services, or cloud applications. In 3GPP, ICPs are key stakeholders whose traffic patterns influence network design and service requirements, particularly for 5G and beyond.

IMS Centralized Services User Equipment

A User Equipment (UE) that supports IMS Centralized Services (ICS) in addition to standard IMS functionality. It enables access to IMS services via both circuit-switched and packet-switched networks, providing service continuity and a consistent user experience.

IMS Communication Service Identifier

The ICSI is a unique identifier used within the IMS to distinguish between different IMS Communication Services (ICS), such as Voice over LTE (VoLTE), Video over LTE (ViLTE), or Rich Communication Services (RCS). It is included in SIP signaling to allow the network and UE to unambiguously identify the service being invoked and apply the correct service logic and policies.

Identity Web Services Framework

A web services framework, profiled from the Liberty Alliance Project, that defines standardized protocols for discovering, invoking, and managing identity-related web services in a secure and privacy-respecting manner. It enables services to interact with user identity data.

Inter-destination Multimedia Synchronization

A service enabler that ensures synchronized playback of multimedia content across multiple devices or destinations. It is crucial for delivering consistent, high-quality experiences in group communications, social TV, and multi-screen applications.

Instantaneous Decoding Refresh

A feature in video coding, particularly H.264/AVC and H.265/HEVC, that defines a type of video frame (IDR picture). It resets the decoder's state, ensuring all following frames can be decoded without reference to any frame before the IDR, which is crucial for random access, channel switching, and error recovery in streaming.

Integrated Digital Television (receiver)

A digital television receiver that integrates a 3GPP broadband modem, enabling it to receive TV services via mobile broadband networks (e.g., LTE, 5G NR) in addition to, or instead of, traditional broadcast channels. It supports converged media delivery, such as 3GPP MBMS/FeMBMS for broadcast and unicast for on-demand content.

International Emergency Preference Scheme

A network service that provides priority treatment for emergency communications. It ensures that calls and messages from authorized emergency personnel or users in disaster scenarios receive higher precedence over regular traffic, maintaining critical connectivity during network congestion.

Initial Filter Criteria

A set of service point triggers stored in the HSS and used by the S-CSCF in the IMS. They define the conditions under which a SIP message for a user should be forwarded to specific Application Servers (AS) to invoke services.

Internet Facsimile Protocol

A 3GPP-defined protocol adaptation for transmitting Group 3 fax (G3F) over IP networks within the IP Multimedia Subsystem (IMS). It enables legacy fax machine compatibility with modern all-IP networks by encapsulating T.30 fax signaling and T.4/T.6 image data within RTP packets.

Internet Facsimile Transfer

IFT is a 3GPP service enabling the transmission of fax documents over IP-based networks, specifically the IMS. It defines protocols and procedures to adapt traditional Group 3 fax for real-time transport over modern packet-switched networks, supporting both voice-band data and T.38 packetization.

Intelligent Gap Filling

Intelligent Gap Filling is a 3GPP feature for streaming services that dynamically generates and inserts media to fill playback gaps caused by network impairments like rebuffering. It enhances Quality of Experience by maintaining media continuity and reducing perceived interruptions during streaming.

Internet Hosted Octet Stream Service

A 3GPP service enabling transparent, IP-based data streaming between a mobile user and an internet host. It provides a standardized bearer service for octet-aligned data transport over the packet-switched core network, forming a fundamental data connectivity service.

Interaural Intensity Difference

A stereo audio parameter representing the level difference between left and right channels. It is crucial for spatial audio rendering and immersive sound experiences in multimedia services, enabling the perception of sound direction and width.

Inter-Channel Level Difference

Inter-Channel Level Difference (ILD) is an audio parameter in 3GPP's immersive media specifications that defines the relative level difference between audio channels. It is crucial for creating realistic spatial audio and immersive soundscapes in services like 360-degree video and extended reality (XR).

IP Multimedia

A framework for delivering multimedia services (voice, video, messaging) over IP networks within the 3GPP system. It enables rich communication services like VoLTE and RCS, decoupling service logic from the underlying access technology.

Instant Message Origination

IM origination refers to the origination of an Instant Message by an IMS UE. It is a key concept in IMS-based messaging services, defining the starting point of an instant message session from the user's device. This term is used in specifications for messaging and is essential for understanding how instant messaging is handled in 3GPP networks.

Instant Message Termination

IM termination describes the delivery of an Instant Message to an IMS UE. It is the final leg of an OMA/3GPP messaging service where the network delivers a message to the intended recipient device.

IP Multimedia Basic Call State Model

The IP Multimedia Basic Call State Model (IM-BCSM) is a finite state machine model used in the IP Multimedia Subsystem (IMS) to describe the states and transitions of a multimedia session. It provides a standardized framework for call control and service logic execution, enabling consistent handling of SIP-based sessions. IM-BCSM is essential for implementing features like call forwarding, barring, and other supplementary services in IMS networks.

IP Multimedia CAMEL Subscription Information

IM-CSI is a CAMEL subscription profile element that enables the network to apply CAMEL-based service control to IP Multimedia Subsystem (IMS) sessions. It allows operators to offer intelligent, prepaid, and value-added services for IMS multimedia calls and sessions, bridging legacy CAMEL capabilities with the IMS architecture.

Intersection Movement Assist

Intersection Movement Assist (IMA) is a V2X (Vehicle-to-Everything) safety service designed to warn drivers of potential collisions at intersections. It uses direct communication between vehicles (V2V) and/or communication with roadside infrastructure (V2I) to exchange real-time kinematic data (position, speed, heading). The service calculates collision risks and provides alerts to drivers, helping to prevent crossing-path accidents common in intersections with limited visibility.

Integrated Mobile Broadcast

Integrated Mobile Broadcast (IMB) is a 3GPP technology for delivering broadcast content (like TV or radio) over UMTS terrestrial radio access networks. It efficiently uses cellular spectrum to multicast media to many users simultaneously, integrating broadcast services into the existing mobile network infrastructure. It enables operators to offer broadcast services without a separate dedicated broadcast network.

IMS Media Coding

IMS Media Coding (IMC) refers to the codecs and media processing standards used within the IP Multimedia Subsystem for voice, video, and other multimedia sessions. It ensures interoperability and quality for media streams over IMS networks, covering speech and video codecs, transcoding, and media adaptation. IMC is crucial for consistent multimedia experience across diverse devices and networks.

Instant Message Disposition Notification

Instant Message Disposition Notification (IMDN) is a 3GPP-specified mechanism that provides delivery and read status reports for IP-based instant messages, similar to delivery and read receipts in OTT messaging apps. It is part of the IP Multimedia Subsystem (IMS) messaging framework, enabling senders to receive notifications about the fate of their sent messages. This enhances the user experience for IMS-based messaging services like Rich Communication Services (RCS).

Immediate Location Request

An immediate location request is a location service request that requires a single, immediate location response. It is used when the location of a UE is needed urgently without delay.

IMS Centralized Services

ICS is the provision of communication services where services and service control are based on IMS mechanisms and enablers, supporting diverse access networks (CS and IP, wireless and wireline) and service continuity between them.

IP Multimedia Subsystem Messaging Services

A family of IMS-based services enabling users to send and receive messages over the IP Multimedia Subsystem, covering immediate, session-based, and deferred delivery messaging modes.

IP Multimedia Subsystem Multimedia Telephony Service

An IMS service providing real-time bidirectional conversational multimedia communication (speech, video, text, data) between users, including supplementary services and regulatory features.

IP Multimedia Subsystem Video Telephony

IMS-VT is a standardized service enabling real-time, high-quality video calls over LTE and 5G networks via the IP Multimedia Subsystem. It ensures interoperability between devices and networks, replacing legacy circuit-switched video telephony with an all-IP solution. This is crucial for delivering consistent, carrier-grade video communication experiences.

Internet Media Subtitles and Captions

IMSC is a 3GPP standardized format for delivering timed text subtitles and captions in multimedia services over IP networks. It is based on W3C TTML and ensures precise synchronization, styling, and layout of text with audio-visual content. This enables accessibility and multilingual support for streaming video and broadcast services.

Intelligent Network

A standardized architecture that separates service logic from switching functions, enabling rapid creation and deployment of advanced telecommunication services like freephone, prepaid, and VPN. It decouples service control from call control, allowing operators to innovate without modifying core network switches.

in-band announcement

An in-band announcement is a network-originated message delivered to a user over the same bearer used for the active communication session. It enables supplementary services like call waiting or advice of charge without requiring a separate signaling channel.

INcoming Call

INC refers to the network event and associated procedures for handling an incoming call to a mobile subscriber. It is a fundamental telephony concept in 3GPP specifications, governing call setup, routing, and subscriber notification. Its standardized definition ensures consistent call handling across different network implementations and generations.

Initial Location

The location estimate and timestamp captured at the start of an originating emergency call. It enables emergency services to be dispatched to the caller's position at call setup.

Initiating Subscriber

The mobile subscriber who modifies the Follow Me data of a remote party, typically in the context of supplementary services. This term is specific to Follow Me service implementations in 3GPP.

Instant Message

A near-real-time message exchanged between users, defined by OMA SIMPLE IM and 3GPP TS 24.247. It enables text-based conversational services over IMS and is also used to designate a CPM Message.

Intelligent Communication Assistant

A virtual AI-powered assistant residing in the operator network that interacts with users via voice, video, text, or gestures over IMS. It personalizes communication services using user and network data and can leverage 6G AI and computing services.

Interactive service

An interactive service is an MBMS or PSS service that lets users interact with content by changing what is presented or by sending information back to the provider via a unicast channel. It enables participation, voting, and on-demand content control.

Interconnection

Interconnection in 3GPP refers to the means of communication between Mission Critical (MC) systems, allowing users of one MC system to communicate with users of other MC systems. It is essential for enabling seamless mission-critical services across different networks and jurisdictions.

Interconnection group

An MC service group configured to allow inclusion of MC service group members who are MC service users from partner MC system(s). It enables cross-system mission-critical communication.

Interworking between Mission Critical Systems and LMR Systems

A means of communication between mission critical systems and LMR systems, allowing MC users to communicate with LMR users. It enables interoperability between 3GPP MC services and legacy land mobile radio networks.

Interworking Group

A group composed of members from both the MC system and the LMR system, defined in either system. It enables group communication across the interworking boundary between mission critical and legacy radio systems.

Invalid Silence Insertion Descriptor frame

A SID frame that is accepted but has errors, used to indicate comfort noise should start or continue without updating parameters. It ensures robust DTX operation in speech codecs.

Inverse filter

A filter that removes short-term correlation from speech signals, modeling the inverse frequency response of the vocal tract. It is fundamental in speech coding for linear prediction analysis.

Isolated E-UTRAN Operations for Public Safety

IOPS is a 3GPP feature enabling LTE (E-UTRAN) base stations (eNBs) to operate independently from the core network during emergencies or network failures. It provides critical local communication for public safety personnel when the wider network is unavailable, ensuring mission-critical connectivity.

Isolated Operation for Public Safety Mission Critical System

The IOPS MC system comprises the application functions and enabling capabilities required to support mission critical services when operating in IOPS mode. It ensures MC users retain critical communications even when backhaul connectivity to the core network is lost.

Isolated Operation for Public Safety Mode of Operation

IOPS mode of operation enables a level of communication for mission critical users when the backhaul connection to the core network is lost. It allows local networks to continue serving users autonomously, ensuring critical services remain available during isolation.

IP Multimedia Application

An application that handles one or more media types (speech, audio, video, data) in a synchronized way from the user's perspective. It may involve multiple media streams, parties, and connections within an IP multimedia session.

IP Multimedia Service

The user experience provided by one or more IP multimedia applications. It represents the service-level view of multimedia communication, built on IMS and GPRS, enabling operators to offer rich, synchronized multimedia services.

IP Multimedia Session

A set of multimedia senders and receivers with data streams flowing between them, supported by the IP Multimedia CN Subsystem and enabled by IP connectivity bearers. It allows users to invoke concurrent multimedia sessions.

IP Service

A service using an IP bearer provided by an IP service provider. Data traffic is routed according to IP addresses of sender and receiver(s).

IP Service Provider

A service provider that provides IP services. This may or may not be a network operator; for example, the operator of an IMS would be an IP service provider.

Internet Protocol Service Subscriber

A subscriber to an IP service provider that uses IP services. This term defines the end-user entity in 3GPP specifications that consumes IP-based services delivered over mobile networks.

Internet Protocol Multicast

A network service for efficient one-to-many or many-to-many distribution of IP data streams, such as live video or software updates, to a group of interested receivers. It optimizes bandwidth usage by having the network replicate packets only at branch points, unlike unicast or broadcast. It is supported within 3GPP networks for multimedia broadcast/multicast services.

IP Short Message Gateway

A network function that enables interworking between legacy circuit-switched Short Message Service (SMS) and IP-based messaging, primarily for delivery to devices connected via IP networks like IMS or WLAN. It acts as a protocol translator, allowing SMS to be sent and received over IP access without requiring a circuit-switched radio connection. This was crucial for the transition to all-IP networks.

Idle Period Downlink - Observed Time Difference Of Arrival

A specific application of the IPDL technique to enhance the OTDOA positioning method in UMTS networks. It is a network-assisted location service where the network creates downlink idle periods to enable accurate UE measurements of neighbor cell signals for calculating the UE's geographical position.

In-Progress Emergency Group

In-Progress Emergency Group (IPEG) is a 3GPP service feature that enables the establishment of a temporary communication group during an emergency situation, such as mission-critical push-to-talk. It allows an authorized user (e.g., incident commander) to dynamically add or remove participants to a group call that is already in progress.

In-Progress Emergency Private Call

A critical service in MCPTT (Mission Critical Push To Talk) for handling emergency private calls that are already in progress. It ensures emergency communication sessions are prioritized and managed correctly within the network, maintaining call continuity and control during critical incidents.

In-Progress Imminent Peril Group

A service state in MCPTT for an active group call session initiated under imminent peril conditions. It manages emergency communications for a predefined group, ensuring prioritized network resources and coordinated alerting for life-threatening situations.

Internet Protocol Television

IPTV is a system for delivering television services over a managed IP network, such as a 3GPP IMS. It enables broadcast TV, video on demand, and interactive services, transforming mobile networks into multimedia platforms. It matters for enabling carrier-grade, QoS-managed video delivery to mobile and fixed users.

Intra Random Access Picture

An Intra Random Access Picture (IRAP) is a video coding concept in 3GPP's Dynamic Adaptive Streaming over HTTP (DASH) and related media delivery standards. It is a coded picture that allows random access into a video stream, enabling features like seeking, switching between different representations (bitrates), and error recovery.

Integrated Receiver-Decoder

A functional component in a 3GPP Media Streaming architecture that receives, decrypts, and decodes protected media streams. It is a key client-side entity in the 3GPP Dynamic Adaptive Streaming over HTTP (DASH) ecosystem for secure and efficient content delivery.

Information Service

A broad category of services in 3GPP that provide information delivery to users, such as weather, news, or location-based content. It encompasses architectural elements, management functions, and charging mechanisms defined across numerous specifications to support diverse content provisioning.

Immersive Audio for Split Rendering Scenarios

ISAR is a 3GPP media codec and delivery framework for immersive audio experiences in Extended Reality (XR) applications using split rendering. It enables high-quality, low-latency spatial audio streaming where audio rendering is split between the device and network.

Initialization Segment Description

A metadata structure used in multimedia streaming, particularly for Dynamic Adaptive Streaming over HTTP (DASH). It describes the initialization segment of a media presentation, which contains information needed to start decoding the media stream. This is crucial for ensuring clients can correctly parse and begin playback of adaptive bitrate content.

Interworking Selection Function

The ISF is a logical function within the IP Multimedia Subsystem (IMS) that determines the appropriate interworking method for a communication session. It selects between SIP-I and SIP-T protocols based on network capabilities and session requirements, ensuring seamless interoperability between IMS and legacy circuit-switched networks.

International Organization for Standards, Base Media File Format

ISOBMFF is an ISO standard that defines a structured container format for storing and streaming multimedia content, such as video and audio. In 3GPP, it is adapted for services like DASH and MBMS, enabling efficient adaptive bitrate streaming and broadcast delivery across mobile networks.

Internet Service Provider

An ISP is an entity that provides access to the internet and related services, such as web hosting or email. In 3GPP, ISPs interact with mobile network operators to deliver data services, influencing QoS, billing, and interconnection policies for mobile broadband.

Inter-System Routing Policies

ISRP is a set of ANDSF (Access Network Discovery and Selection Function) policies that guide a UE on how to route IP traffic flows across multiple available access networks (e.g., 3GPP and non-3GPP like Wi-Fi). It enables intelligent, simultaneous multi-access connectivity based on operator rules and user preferences.

Immediate Service Termination

Immediate Service Termination is a network capability that allows for the instant and forced termination of a subscriber's services, typically for administrative, security, or billing reasons. It is a critical operational tool for network operators to manage service access and enforce policies without delay.

Information Transfer Capability

Information Transfer Capability (ITC) is a fundamental concept in 3GPP that classifies the nature of a bearer service, such as speech, data, or video. It defines the essential characteristics for service negotiation and bearer setup between the network and the user equipment. This classification is crucial for ensuring the correct QoS and network resource allocation for diverse applications.

International Telecommunication Charge Card

The International Telecommunication Charge Card (ITCC) is a service enabling users to charge communication services to a pre-paid or post-paid card account, often for international roaming or premium services. It is managed via protocols between the serving network and a dedicated charging server. This facilitates flexible billing and payment for services across different operator domains.

Intelligent Transport Systems

A comprehensive framework for vehicular communications (V2X) enabling safety, traffic efficiency, and infotainment services. It defines communication between vehicles (V2V), with infrastructure (V2I), with pedestrians (V2P), and with networks (V2N), utilizing both direct PC5 and cellular Uu interfaces.

IMS User Agent

The IMS User Agent (IUA) is a functional entity within a User Equipment (UE) or terminal that acts as the client endpoint for IMS-based services. It handles SIP registration, session establishment, and service logic for multimedia telephony, messaging, and other IP-based services in the IMS core.

Immersive Voice and Audio Services

A 3GPP-standardized media codec and service framework for delivering immersive, multi-channel spatial audio experiences over mobile networks. It enables realistic soundscapes for voice calls, music, and extended reality (XR) applications by supporting audio objects and channels. IVAS is key for next-generation communication services like augmented reality telephony.

Interactive Voice Response

A telephony technology that allows a computer system to interact with callers through voice prompts and dual-tone multi-frequency (DTMF) tone input. It automates call handling, information retrieval, and call routing without human intervention. IVR is a foundational component for customer service lines, automated banking, and network-based supplementary services.

Interworking Mobile Terminated Location Request

A location service procedure for determining the position of a mobile device connected via an Interworking Wireless Local Area Network (I-WLAN). It is a network-initiated request, meaning the location request originates from an external client or application server, not the user equipment itself. This enables location-based services for I-WLAN users, extending cellular LCS capabilities to WLAN access.

Java 2 Platform, Micro Edition

J2ME is a Java platform designed for resource-constrained devices like early feature phones and embedded systems. It provided a standardized environment for developing and deploying portable applications (MIDlets) and services on mobile devices, enabling downloadable games, utilities, and early mobile data services before the smartphone era.

Java 2 Platform, Standard Edition

J2SE is the core Java platform for desktop and server environments. In 3GPP, it is referenced within the Open Service Access (OSA) framework, where application servers hosting network service applications (SCFs) are typically built using J2SE/J2EE. It provides the robust runtime for OSA gateway components that expose network capabilities to enterprise applications.

Java Application Descriptor

A standardized descriptor for Java applications in mobile networks, introduced in 3GPP Release 5. It defines the structure and metadata for Java-based applications (MIDlets) to enable secure deployment and execution on mobile devices. This facilitates a platform for downloadable services and applications.

Java Application Manager

A component on the mobile device that manages the lifecycle of Java applications (MIDlets). Introduced in 3GPP Release 5, it handles installation, execution, updating, and removal of Java apps based on descriptors (JAD). It ensures security and resource compatibility.

Jitter Buffer Management

Techniques and algorithms to manage jitter buffers in real-time communication services like Voice over IP (VoIP) and video streaming. Introduced in 3GPP Release 8, it handles packet delay variation to ensure smooth playout and quality of experience.

Joint Collaborative Team on Video Coding

The Joint Collaborative Team on Video Coding (JCT-VC) was a partnership between ITU-T VCEG and ISO/IEC MPEG that developed the High Efficiency Video Coding (HEVC/H.265) standard. 3GPP adopted HEVC for enhanced video services, specifying its use and profiles in specifications like TS 26.906 and TS 26.955 to enable efficient high-resolution video delivery over mobile networks.

JPEG File Interchange Format

JFIF is a standard file format for storing JPEG-encoded still images. In 3GPP, it is specified as a mandatory format for Multimedia Messaging Service (MMS) and other multimedia applications to ensure interoperability when exchanging JPEG images between different devices and networks.

Joint Scalable Video Model

JSVM is a reference software model for the Scalable Video Coding (SVC) extension of the H.264/AVC standard. In 3GPP, it provides a standardized implementation for testing and developing scalable video services, enabling efficient adaptation to varying network conditions and device capabilities.

Java Telephony Application Programming Interface

A standardized Java API for developing telephony applications in 3GPP networks. It provides a platform-independent interface for call control, enabling services like call forwarding, conferencing, and interactive voice response systems. Its importance lies in fostering a rich ecosystem of value-added services.

Joint Video Exploratory Group

A collaborative group between 3GPP and ITU-T that explored and developed the Versatile Video Coding (VVC/H.266) standard. It was crucial for defining the next-generation video codec to enable ultra-high-definition video services over 5G networks, significantly improving compression efficiency over its predecessor, HEVC.

Java™ Virtual Machine

A runtime environment that executes Java bytecode, enabling platform-independent application deployment. In 3GPP, it's specified for Mobile Station (UE) environments to allow secure, downloadable service logic and applications, forming the basis for technologies like MIDP and SIM Toolkit.

Korean Public Alert System

A 3GPP-defined warning system for delivering public safety alerts to mobile users in South Korea. It utilizes Cell Broadcast Service (CBS) to broadcast geographically targeted emergency messages, such as natural disaster warnings, to all compatible handsets in affected cells.

Local Active Codec Set

A UE-specific list of speech codecs that are currently available and configured for use in a circuit-switched voice call. It is managed by the network and sent to the UE to control which codecs can be selected during call setup, enabling dynamic codec negotiation and adaptation.

Local Area Data Network

A 5G service that provides connectivity to a specific data network only when the UE is located within a defined geographical area. It enables efficient, localized data services like factory automation or campus networks, reducing signaling and resource usage outside the service area.

Location Application Function

A network function in the 5G Service-Based Architecture that provides location services to external applications. It acts as an interface for applications to request the location of UEs, supporting emergency services, lawful intercept, and commercial location-based services.

Last Known Location

The most recent location estimate and its timestamp for a target UE, stored in the LCS Server. It is used for location-based services when a fresh location fix is not available or not required.

Location Based Services

A suite of services and network capabilities that utilize the geographic position of a User Equipment (UE) to provide value-added applications. These include emergency services (E911), navigation, location-based advertising, fleet tracking, and geofencing. LBS leverages cellular network positioning methods and/or satellite GNSS to determine UE location.

Location Client Authorization Function

A network function within the Location Services (LCS) architecture that authorizes requests from external or internal clients to obtain the location of a mobile device. It verifies the client's identity and checks if it has permission to locate a specific target subscriber, enforcing privacy and security policies.

Location Client Control Function

The LCCF is a core network function within the 3GPP Location Services (LCS) architecture. It acts as the primary interface and controller for external location-based service applications (LCS Clients), managing their requests to locate a mobile device (UE).

Location Client Co-ordinate Transformation Function

The LCCTF is a network function within the 3GPP LCS architecture that converts geographic coordinates between different reference systems. It ensures location data reported to external clients is in a usable and requested format, such as transforming from a local ellipsoid to a common system like WGS-84.

Location Client Function

A functional entity within a User Equipment (UE) or external client that requests location services from the network. It initiates positioning requests, receives location estimates, and may interact with applications requiring geographical data.

Low Complexity Low Delay

LCLD refers to a set of 3GPP features and codec enhancements designed to support services with stringent low-latency and low-complexity requirements, such as immersive communication and extended reality. It optimizes audio and video processing to reduce end-to-end delay and computational overhead.

Local Call Local Switch

A feature enabling direct switching of user plane traffic between two UEs connected to the same base station or access point, bypassing the core network. It reduces latency, core network load, and backhaul usage for local communication, crucial for services like proximity services (ProSe) and local voice/data offload.

Location Services

Location Services (LCS) is the standardized 3GPP architecture and set of protocols for determining the geographical position of a mobile device (UE). It supports numerous positioning methods (e.g., A-GNSS, OTDOA, E-CID) and provides location information to authorized clients like emergency services, network operators, and value-added applications.

Location Services Client Subscription Profile

A collection of subscription attributes for Location Services (LCS) parameters agreed between an LCS client and the service provider. It defines the terms under which location information can be accessed, ensuring privacy and authorized use.

Location Services Feature

The LCS Feature is the capability of a PLMN to support Location Services, enabling client/server interactions to determine the geographic location of target UEs. It is fundamental for emergency calling, lawful interception, and location-based applications.

Location Services User Plane

Location Services User Plane (LCS-UP) is a 3GPP architectural concept and functional framework introduced for 5G. It defines the user plane path and procedures for transporting positioning-related measurement data and assistance data between the UE, the network (RAN, LMF), and external clients. It enables high-accuracy, low-latency positioning services by leveraging the data plane.

LCS Client

The LCS Client is a logical functional entity that requests location services from the network. It is a key component of the 3GPP Location Services (LCS) architecture, enabling applications like emergency services, fleet tracking, and location-based billing.

LCS Server

The LCS Server is the core network entity that processes location service requests from LCS Clients. It orchestrates positioning, enforces privacy, and returns location estimates, acting as the central control point for 3GPP Location Services.

Layered Coding Transport

Layered Coding Transport is a 3GPP media delivery mechanism for streaming services that uses layered video coding (e.g., SVC) combined with FLUTE/ALC file delivery. It enables efficient adaptive streaming and reliable multicast/broadcast distribution.

Location Client Zone Transformation Function

A network function within the Location Services (LCS) architecture that transforms a client's geographical zone request into a corresponding network area. It is essential for providing location-based services like emergency calls, fleet management, and zone-based billing by mapping service logic to physical network topology.

Local DAA Ground Station

LDGS is a 3GPP Rel-19 entity that serves as a local ground station for Direct Access to Application (DAA) services, enabling direct communication between user equipment and application servers via satellite or local access. It supports low-latency, localized service delivery.

Location Deferred Request

Location Deferred Request is a capability within the Location Services (LCS) architecture that allows a client to request the location of a target UE to be determined and delivered at a later, specified time. It enables location-based applications that do not require immediate real-time positioning, such as periodic tracking or geofencing alerts.

Location Information Answer

A standardized response message within the 3GPP Location Services (LCS) framework. It is sent by a location server (e.g., GMLC) to a requesting client (e.g., LCS Client) to deliver the requested location information of a target user equipment (UE). It is a core component for enabling emergency services, lawful intercept, and commercial location-based applications.

Location IMS – Interworking Function

A network function that enables location services for IMS emergency calls. It acts as a mediator between the IP Multimedia Subsystem (IMS) core and the underlying cellular network's location system (GMLC), translating between IMS signaling (SIP) and location-specific protocols (MLP) to provide the caller's location to the emergency services network.

Local IP Access

LIPA enables a User Equipment (UE) to access a local IP network, such as a home or enterprise network, directly via a femtocell or Home NodeB/eNodeB, without routing traffic through the mobile operator's core network. This reduces backhaul load and improves performance for local services like printers or media servers. It is a key feature for enterprise and residential small cell deployments.

Location Information Request

A Location Information Request (LIR) is a procedure or message used by an entity (like an application server or network node) to query the network for the geographic or civic location of a User Equipment (UE). It is a fundamental mechanism enabling location-based services (LBS) like navigation, emergency services (E911), and asset tracking. The request triggers network-based, UE-assisted, or hybrid positioning methods.

Location Information Relay Function

The LIRF is a network function that relays location-related information between a User Equipment (UE) and a location server, such as a Gateway Mobile Location Centre (GMLC). It acts as an intermediary, facilitating location-based services like emergency calls, navigation, and asset tracking by ensuring location data is accurately and securely transmitted.

Location Information Server

The Location Information Server (LIS) is a network entity that provides location information of User Equipment (UE) to authorized applications. It is a key component for location-based services (LBS) and emergency services, determining device position using network-based, terminal-based, or hybrid methods and delivering it via standardized interfaces like OMA MLP.

Listening service subscriber

A service subscriber who is listening to an ongoing voice group call in a GSM/EDGE network. This role is part of the Voice Group Call Service (VGCS) defined for public safety and professional users.

Location Management Client

A client function introduced in 3GPP Release 17 for location services, typically residing in a UE or AF. It interacts with the network's location management system to request and receive location information for the UE or a target device, enabling advanced location-based applications and services.

Land Mobile Radio

A professional mobile radio communication service used by public safety organizations, utilities, and industries for mission-critical voice and data. In 3GPP, it refers to the integration and evolution of these traditional systems with broadband cellular networks like LTE and 5G, enabling advanced critical communications.

Land Mobile Radio system

The collection of applications, services, and enabling capabilities required to provide Land Mobile Radio (LMR) service for a mission critical organization. It is a conceptual term used in 3GPP specifications for interworking between LMR and 3GPP mission critical services.

Land Mobile Radio user

A user of an LMR service who has a device capable of participating in legacy Land Mobile Radio services. This term is used in 3GPP specifications for interworking between LMR systems and 3GPP mission critical services.

Location Measurement Unit

A network element or device that provides radio measurements to support location-based services (LCS). It measures timing, signal strength, or angle-of-arrival of signals from mobile devices or base stations to enable positioning techniques like Observed Time Difference of Arrival (OTDOA) and Enhanced Cell ID.

Last Number Dialled

A telephony service feature that allows a user to redial the most recently called telephone number, typically by pressing a single key or using a short code. It provides convenience and speeds up the process of reattempting a call.

Local Co-ordinates

Local Co-ordinates are coordinates relative to a local Cartesian system with a reference point origin, used in 5GS for location services. They enable precise positioning in indoor or local environments where WGS84 may be insufficient.

Local Service

Services provided by the current roamed-to network that are not Home Environment (HE) services. The same service can be provided as a local service to inbound roamers and as an HE service to home subscribers.

Located User Equipment

A Sidelink Reference UE whose location is known or obtainable via Uu-based positioning. It serves as an anchor to determine the position of a Target UE through Sidelink Positioning in 5G networks.

Location

The current position, velocity, and direction of an MCX UE, plus other attributes like geographic area labels. It enables location-aware mission-critical services and is fundamental to emergency response coordination.

Location (Based) Application

A software application that processes or utilizes location information, which can be input by a user or detected by the network or UE. Examples include navigation and location-based services.

Location Agnostic Service Experience

A service experience where user interaction and information have little or no relation to the user's physical location. The service provides content about a distant or non-existent location, independent of where the user actually is.

Location Dependent Service

A service provided by a teleoperator or third party that is available (pull) or activated (push) when the user arrives in a certain area. It does not require advance subscription, but push activation must be confirmed by the user.

Location Estimate

The geographic location of a UE or ME, expressed in latitude and longitude, possibly including velocity. It is a fundamental output of 3GPP location services (LCS) used for emergency calls, lawful interception, and location-based applications.

Location Independent Service

A service provided by a teleoperator or third party that is available anywhere in the network coverage and is activated by user request or another service. It requires a subscription in advance and can be any type of service, such as MMS, SWDL, or LBS.

Location Information

Location Information indicates the geographic position of a served subscriber or Mobile Station, independent of MS status, and may include an age indicator showing how recent the data is. It underpins emergency calling, lawful interception, and location-based services in 3GPP networks.

Location Related Service Experience

A service experience where user interaction and information are relevant to the user's physical location. The service adapts content and interaction based on where the user accesses it, enabling location-aware applications.

Location Server

A Location Server is a physical or logical entity (e.g., E-SMLC, SUPL SLP, or LMF) that manages positioning for a target device by collecting measurements and providing assistance data. It computes or verifies the final location estimate, forming the core of 3GPP location services.

Loopback routeing

Loopback routeing is a method of routing a SIP request back to the visited network for local breakout in the roaming architecture for voice over IMS with local breakout. It enables optimized routing for VoLTE roaming.

Linear Prediction

A fundamental digital signal processing technique used extensively in speech and audio codecs to model the spectral envelope of a signal. It predicts a sample's value as a linear combination of its past samples, allowing for efficient compression by transmitting only prediction coefficients and an error signal. It is the core of many voice codecs, including AMR and EVS.

Linear Predictive analysis window

A window of speech samples used in the Adaptive Multi-Rate (AMR) codec to compute short-term filter coefficients for linear predictive coding, with a fixed length of 240 samples.

Linear Prediction Coefficients

Linear Prediction (LP) coefficients, also known as Linear Predictive Coding (LPC) coefficients, are the short-term filter coefficients used in speech codecs to model the spectral envelope of speech. They are fundamental to efficient speech compression in 3GPP codecs like AMR, AMR-WB, and EVS.

Low Power and High Accuracy Positioning

A 3GPP feature introduced in Release 18 to enable energy-efficient, precise location services for IoT and consumer devices. It optimizes positioning procedures to minimize device power consumption while achieving high-accuracy location fixes, often using GNSS and cellular measurements. This supports use cases like asset tracking, emergency services, and augmented reality.

Location Retrieval Function

The Location Retrieval Function (LRF) is a core network element in the IP Multimedia Subsystem (IMS). It provides location information of User Equipment (UE) to authorized entities, primarily for emergency services (E911/E112), by interacting with access network location functions and subscriber databases.

Last Routing Option

A call routing mechanism in IP Multimedia Subsystem (IMS) that defines the final routing attempt for a session when all other routing logic has been exhausted. It acts as a safety net to handle unresolved or failed call setup scenarios, often directing the call to an announcement server or a default destination.

Localised Service Area Only Access

LSA only access restricts a UE to camp only on cells belonging to the Localised Service Areas (LSAs) to which the user has subscribed. Outside subscribed LSA coverage, the UE may camp on other cells but only limited services apply.

Localised Service Area Priority

LSA Priority is the priority assigned to a subscriber's LSAs, used to select the current LSA when multiple valid LSAs overlap. It ensures deterministic selection of the applicable LSA when a user is subscribed to several LSAs covering the same area.

Location System Assistance Data Function

A network function that provides assistance data to User Equipment (UE) to improve the speed, accuracy, and efficiency of satellite-based positioning methods like GPS. It delivers orbital and timing information for satellites, reducing the time and power required for the UE to acquire a position fix.

Location System Billing Function

The Location System Billing Function (LSBF) is a network element responsible for generating billing records for location-based services. It interfaces with the Location System Control Function (LSCF) and the core network's billing system. Its primary role is to ensure accurate charging for services like emergency calls, lawful interception location requests, and commercial location services.

Location System Control Function

The Location System Control Function (LSCF) is the central control entity in the 3GPP Location Services (LCS) architecture. It coordinates the entire process of locating a mobile device, from receiving a location request to selecting the positioning method and delivering the result. It acts as the brain of the LCS system, interfacing with the core network, radio access network, and external clients.

Local Supported Codec Set

A list of speech and multimedia codecs that a User Equipment (UE) or network entity supports for communication sessions. It is used during session negotiation (e.g., in SIP or SDP) to establish a common set of codecs for a call or data session, ensuring interoperability and optimal media quality.

Location System Operations Function

A functional entity defined in early 3GPP specifications that provides the core capabilities for positioning services. It manages location requests, retrieves positioning measurements, calculates the UE's location, and delivers the result to the requesting client or application.

Location Subscriber Privacy Function

A network function that enforces privacy rules for location-based services. It acts as a policy decision point, checking if a location request (e.g., from an external application) is authorized according to the subscriber's privacy profile, protecting user location data.

Location Subscriber Translation Function

LSTF is a network function within the Location Services (LCS) architecture that translates subscriber identifiers (like MSISDN) into network routing addresses (like IP addresses or SS7 signaling addresses). It enables location-based services to correctly route requests to the appropriate mobile device or network node, essential for emergency calls, lawful interception, and commercial location applications.

Listener SideTone Rating

LSTR is a subjective audio quality metric used to evaluate the side-tone performance in telephony terminals. Side-tone is the deliberate leakage of a speaker's own voice back into their earpiece, and LSTR measures how natural and comfortable this sounds to the listener, impacting perceived call quality and user experience.

Motion to Sound

M2S is a 3GPP service enabling the conversion of motion sensor data into audio signals for accessibility applications. It allows users, particularly those with visual impairments, to perceive motion or gestures through sound. This enhances accessibility in multimedia and user interface interactions.

Multi-Access PDU Session

A Multi-Access PDU Session is a PDU Session that provides connectivity using one access network at a time or simultaneously one 3GPP and one non-3GPP access. It enables session continuity and aggregation across heterogeneous access networks, key for 5G converged networking.

MBMS-Aware Application

An application that is specifically designed to utilize and interact with the Multimedia Broadcast Multicast Service (MBMS) capabilities of a 3GPP network. It leverages broadcast/multicast delivery for efficient content distribution to multiple users.

Multicast Adaptive Bit Rate

MABR is a Rel-19 3GPP feature that enables adaptive bit rate streaming over multicast in 5G networks. It allows dynamic adjustment of media quality based on network conditions, improving user experience for live and linear content.

Maximum number of Codecs Modes in the Active Codec Set

MACS defines the maximum number of codec modes that can be simultaneously active in a multimedia session, such as a video call. It is a key parameter for managing session complexity and ensuring network resources are not overwhelmed by excessive simultaneous encoding options. This control is crucial for maintaining service quality and efficient bandwidth utilization.

MPEG-H Audio Metadata information

MAE refers to the metadata information associated with MPEG-H Audio, an advanced audio codec system standardized for immersive and interactive audio experiences. This metadata enables features like object-based audio, dynamic adaptation to different playback systems, and personalized audio rendering. It is a key enabler for next-generation audio services in 5G broadcast and media delivery.

Mobile Additional Function

A standardized supplementary service in 3GPP networks that provides additional telephony features beyond basic call handling. It enables operators to offer enhanced services like call forwarding, barring, and identification, improving user experience and service differentiation.

Mobile Access Hunting supplementary service

A supplementary telephony service that allows an incoming call to a busy or unanswered subscriber to sequentially hunt through a predefined list of alternative destinations. It enhances call completion rates by automatically trying additional numbers, such as other devices or voicemail.

Media Aware Network Element

A network element that optimizes multimedia delivery by being aware of the encoded media content and network conditions. It enables intelligent adaptation of media streams, such as video, to improve quality of experience (QoE) and network efficiency.

Manual Commencement Mode

A mode for MCPTT private calls where the receiving user must manually accept or reject the call setup before communication begins. It ensures callee consent and is essential for mission-critical push-to-talk services.

Multi Access PDN Connectivity

A 3GPP feature allowing a User Equipment (UE) to maintain simultaneous Packet Data Network (PDN) connections over multiple 3GPP and non-3GPP access networks (like LTE and Wi-Fi). It enables the UE to be connected to the same PDN (e.g., the Internet or an IMS service) via different access types concurrently, supporting seamless access network selection and traffic steering.

Metadata-Assisted Spatial Audio

A 3GPP codec enhancement for immersive audio experiences. It uses metadata to describe spatial audio scenes, enabling efficient compression and high-quality rendering on devices with varying speaker configurations. This is crucial for applications like extended reality (XR) and advanced media streaming.

MASA with 1 TC (mono-MASA)

A specific profile of the MASA standard where the core audio is a single, mono transport channel (TC). The spatial audio scene is entirely described by the accompanying metadata, which instructs the renderer on how to spatialize the mono signal. This is the most bandwidth-efficient MASA profile.

MASA with 2 TC (stereo-MASA)

A MASA profile where the core audio comprises two transport channels (typically forming a stereo pair). The metadata provides additional spatial information that enhances or repositions elements beyond the basic left-right stereo image, enabling more accurate and immersive soundscapes than conventional stereo.

Maximum possible AIUR

Maximum possible AIUR is the highest achievable Air Interface User Rate that multiple full-rate traffic channels (TCH/F) can provide in a GSM/GPRS system. It defines the upper bound of user data throughput over the radio interface for a given channel configuration.

Mobile Broadband

The primary service category for high-speed internet access provided by cellular networks like 4G LTE and 5G. It enables applications such as web browsing, video streaming, and cloud services on mobile devices, forming the foundation of consumer and business data connectivity.

Multimedia Broadcast Multicast Service

A 3GPP service enabling efficient one-to-many delivery of multimedia content (e.g., TV, software updates) to multiple users simultaneously. It optimizes radio and network resources by using broadcast/multicast bearers instead of individual unicast streams, crucial for mass content distribution.

Multimedia Broadcast Multicast Service activated services

A set of services comprising those in MBMS multicast mode that the UE has joined and those in MBMS broadcast mode that the UE is interested in receiving. It defines the services a UE is actively engaged with.

Multimedia Broadcast Multicast Service Bearer

An EPS service that delivers identical IP datagrams to multiple receivers within a designated area. It enables efficient point-to-multipoint content distribution, such as mobile TV and live streaming, by sharing network resources across many users.

Multimedia Broadcast Multicast Service Bearer Service

A network service that delivers a single multicast data stream to one or more users, associated with a specific QoS profile. It is a fundamental building block for MBMS, allowing multiple bearer services to support a single MBMS service.

Multimedia Broadcast Multicast Service Delivery Method

A mechanism used by an MBMS user service to deliver content, utilizing MBMS bearers and associated procedures. It defines how content is transported, such as download or streaming, and is essential for efficient multicast distribution.

Multimedia Broadcast Multicast Service Download Delivery Method

A 3GPP-defined method for delivering discrete objects, such as files, to multiple users simultaneously using MBMS download sessions. It enables efficient point-to-multipoint file distribution over cellular networks.

Multimedia Broadcast Multicast Service Download Session

A logical session that defines the time, protocols, and protocol state for downloading content files via MBMS. It configures both sender and receiver for efficient point-to-multipoint file delivery.

Multimedia Broadcast Multicast Service Notification

A mechanism that informs UEs about a forthcoming or ongoing MBMS data transfer, or about changes in the provision of MBMS services. It enables UEs to prepare for reception and manage service continuity.

Multimedia Broadcast Multicast Service Selected Services

A subset of MBMS activated services in broadcast mode for which the UE uses RRC procedures to inform UTRAN that the service has been selected by upper layers. It enables the network to know which services a UE is interested in receiving.

Multimedia Broadcast Multicast Service Service Announcement

Mechanism to allow users to be informed about the MBMS user services available. It enables discovery of broadcast/multicast content and is essential for user equipment to find and access MBMS services.

Multimedia Broadcast Multicast Service Service Area

The area in which a specific MBMS session is made available. It defines the geographic scope of broadcast/multicast services and is described by a list of MBMS Service Area IDs, each representing a group of cells.

Multimedia Broadcast Multicast Service Streaming Delivery Method

Delivery of continuous media (e.g. real-time video) by means of a MBMS streaming session. It enables efficient broadcast of live audio/video content to multiple users simultaneously.

Multimedia Broadcast Multicast Service Streaming Session

A set of time, protocol, and protocol state parameters that define the sender and receiver configuration for streaming content over MBMS. It ensures synchronized and efficient delivery of live or on-demand media to multiple users.

Multimedia Broadcast Multicast Service Subchannel

A logical channel within an MBMS bearer that uses additional parameters (e.g., UDP port) to distinguish sub-streams for group communication, such as floor control in group calls. It enables multiple logical channels over a single MBMS bearer.

Multimedia Broadcast Multicast Service User Service Discovery and Announcement

Mechanisms for UEs to discover available MBMS user services and for service providers to announce them. Discovery allows UEs to obtain a list of services and their details, while announcement enables providers to make that information available.

Multimedia Broadcast/Multicast Service User Service Initiation

UE mechanisms to set up reception of MBMS User Service data, occurring after service discovery. It establishes the bearer, session, and delivery parameters needed before content can be received.

Multimedia Broadcast/Multicast Service User Services

Services that may use more than one MBMS bearer service and more than one broadcast/multicast session. They represent the application-level service consumed by users, distinct from the underlying transport bearers.

Mobile Broadcast/Multicast Network Operator

A business and operational role defined for entities that provide broadcast or multicast services over a mobile network. The MBNO manages the service offering, content acquisition, and potentially the BM-SC, but may rely on another operator's radio access and core network.

Multicast/Broadcast Service

Multicast/Broadcast Service (MBS) is a 3GPP system for efficiently delivering the same content to multiple users simultaneously over a cellular network. It optimizes radio and network resources by using point-to-multipoint transmission, enabling applications like live TV, public warnings, and software updates.

Multicast/Broadcast Service Session

An MBS session is a multicast or broadcast service session defined in 3GPP TS 23.247, enabling efficient point-to-multipoint delivery of content such as live video, software updates, and group communications over 5G networks.

Multicast/Broadcast Service Transport Function

A 5G network function that delivers multicast and broadcast traffic efficiently to multiple UEs. It optimizes network resource usage by enabling point-to-multipoint data distribution, crucial for services like live video streaming and public safety alerts.

Mission Critical

A suite of standardized communication services designed for public safety, emergency response, and industrial applications. It provides reliable, low-latency group communications (push-to-talk), real-time video, and data services with high availability and security, often leveraging network prioritization.

Malicious Call Identification

A supplementary service in circuit-switched telephony networks that allows a subscriber to request the network to identify and log the originating number of a malicious, nuisance, or threatening call. It is a privacy and security feature that aids in tracing harassing callers.

Mission Critical MBMS subchannel Control Protocol

A protocol defined for Mission Critical Push-to-Talk (MCPTT) services using MBMS. It manages the control of MBMS subchannels dedicated to group communications, enabling efficient one-to-many voice and data distribution for public safety and critical users.

Mission Critical Push To Talk

A standardized service for instant group voice communication over 3GPP networks, designed for public safety and mission-critical users. It provides fast call setup, high-priority access, and floor control for efficient, reliable communication in emergency situations.

Multipoint Communication Unit

A network entity that manages multipoint communication sessions, such as conference calls, by mixing and distributing media streams. Introduced in Rel-4, it enables group communication in IMS and mission-critical services, ensuring efficient resource usage and seamless user experience.

Mission Critical Video

A 3GPP service providing real-time video communication for mission-critical scenarios, such as public safety and emergency response. Introduced in Rel-14, it ensures reliable, low-latency video streaming with prioritization over cellular networks, enhancing situational awareness and coordination.

Mission Critical Video client

An MCVideo client is an instance of an MC service client that provides the client application function for the MCVideo service. It enables mission-critical video communications over LTE and 5G networks.

Mission Critical Video User Equipment

An MCVideo UE is a user equipment device capable of participating in Mission Critical Video services, supporting the necessary protocols and codecs for secure, prioritized video communication.

Mission Critical Video User

An MCVideo user is an authorized individual who can access Mission Critical Video services through an MCVideo UE, typically a first responder or critical infrastructure operator.

Mission Critical X

MCX (Mission Critical X) is a 3GPP framework for standardized mission-critical services over 3GPP networks, where X can be Push-to-Talk (MC-PTT), Video (MC-Video), or Data (MC-Data). It enables reliable, low-latency, and secure group communications essential for public safety and professional users, leveraging the quality of service and mobility of cellular networks.

MCData Emergency Alert

MDEA is a mission-critical service enabling authorized agencies to broadcast urgent alerts to a targeted group of MCData users. It is part of 3GPP's MCX framework, ensuring reliable, prioritized delivery of emergency information for public safety and disaster response.

Multimedia Distribution Service

MDS is an early 3GPP service concept for broadcasting multimedia content like audio and video to mobile users. It represents a foundational framework for mobile TV and content delivery, exploring network architectures and bearer services to efficiently distribute popular content to large audiences, a precursor to later technologies like MBMS and eMBMS.

MCPTT Emergency Alert

A critical feature within Mission Critical Push-To-Talk (MCPTT) service that allows an authorized user to initiate a high-priority, network-wide alert during an emergency. It ensures rapid and reliable dissemination of emergency information to all relevant personnel.

Multi-Access Edge Computing

A network architecture that provides cloud computing capabilities and an IT service environment at the edge of the mobile network, close to users. It enables ultra-low latency, high bandwidth, and real-time access to radio network information for applications.

Media Flow

A media flow is one or more packet flows carrying a single media instance (e.g., audio or video) in an IP multimedia session. It is used in IMS and 5GS to describe media transport from the application function perspective.

Media Resource

A Media Resource is an IMS network entity that processes media streams under the control of an OMR (Optimal Media Routeing) entity. It can be a TrGW, BGW, MRF, or an internal function, enabling flexible media handling in IMS.

Media session

A media session is a subset of a FLUS session that defines the timeframe for establishing, transmitting, and terminating media content between a FLUS source and sink. It enables controlled delivery of media streams within the broader FLUS framework.

Media stream

A media stream is the actual content sent from a FLUS source to a FLUS sink within a media session. It represents a single flow of media data, such as audio or video, and is a key component of the FLUS architecture for live uplink streaming.

MCPTT Emergency Group

A predefined group of users designated for emergency communications within the MCPTT service. It enables rapid, prioritized group calls for first responders and public safety personnel during critical incidents, ensuring reliable and immediate coordination.

MCPTT Emergency Group Call

A specific type of emergency call service within MCPTT that is directed to a pre-defined MCPTT Emergency Group (MEG). It provides the highest priority, ensuring immediate setup, pre-emptive resource allocation, and reliable group communication for life-critical situations.

Multi-access Edge Platform

The Multi-access Edge Platform (MEP) is a standardized execution environment at the network edge, defined by ETSI. In 3GPP, it enables hosting and management of applications close to the user. It provides a critical framework for low-latency services like AR/VR, IoT, and network analytics by integrating with 5G core functions.

MCPTT Emergency Private Call

MCPTT Emergency Private Call (MEPC) is a critical feature within the Mission Critical Push-To-Talk (MCPTT) service. It enables an authorized user to initiate a private, one-to-one voice call with a dispatcher or another designated user during an emergency, overriding lower-priority communications for immediate, secure assistance.

MCPTT Emergency Private Priority

MEPP is a priority mechanism within the Mission Critical Push-to-Talk (MCPTT) service, enabling emergency calls to preempt ongoing communications and secure private channels. It ensures reliable, high-priority communication for first responders and critical personnel during emergencies, directly impacting mission success and safety.

Messaging Service

An interactive service offering user-to-user communication via storage units with store-and-forward, mailbox, and message handling functions. It encompasses services like SMS, MMS, and unified messaging.

Mobile Execution Environment Classmark

A MExE Classmark defines a category of MExE UE with a minimum set of processing, memory, display, and interactive capabilities. It ensures that MExE applications or applets are compatible with a specific class of device.

Mobile Execution Environment Executable

A MExE executable is an applet, application, or content that conforms to the MExE specification and can execute on any MExE device that meets the appropriate classmark. It represents the actual code or content delivered to the UE.

Mobile Execution Environment Server

A MExE server is a node that supports MExE services in the MExE service environment. It provides applications and content to MExE UEs, manages their execution, and ensures compatibility with device classmarks.

Mobile Station Application Execution Environment Service

A service enhanced or made possible by MExE technology, which allows mobile stations to execute applications in a standardized environment. It enables operators to deliver value-added services through a secure, interoperable application execution framework.

Mobile Station Application Execution Environment Service Environment

The collection of network nodes and entities that support MExE services, including traditional 3GPP nodes, IN nodes, operator-specific nodes, and external service provider nodes. It enables flexible deployment and direct UE-to-UE interaction for MExE services.

Mobile Station Application Execution Environment Service Provider

An organization that delivers MExE services to subscribers, typically the PLMN operator but possibly a delegated entity. It is responsible for the provisioning and management of MExE services.

Mobile Execution Environment Subscriber

The owner of a subscription who has an agreement with a MExE service provider for MExE services. This term defines the end-user relationship in the MExE service framework, excluding access via non-3GPP networks.

Messaging Framework Adaptor Function

A 5G core network function introduced in Release 17 that provides a standardized framework for message delivery and exposure to third-party application providers. It enables efficient, secure, and policy-controlled messaging services like SMS, MMS, and conversational messaging over 5G networks, supporting new business models and service enablers.

Medium Grain Scalability

A video coding scalability technique defined in the SVC (Scalable Video Coding) extension of H.264/AVC. It allows a video stream to be decoded at different quality levels by selectively discarding groups of transform coefficients, providing a balance between flexibility and coding efficiency.

MPEG-H Audio Stream

A standardized bitstream format for immersive and interactive audio, based on the MPEG-H 3D Audio standard. It enables advanced audio experiences like object-based audio, personalized mixes, and dynamic adaptation to different playback systems, enhancing multimedia broadcasting and streaming services.

Multimedia and Hypermedia Information Coding Expert Group

A standard for interactive multimedia applications, originally developed for digital TV services. It defines a format for creating and presenting interactive content, such as electronic program guides and teletext, on set-top boxes and other receivers. It was a precursor to modern web technologies in the broadcast domain.

Message Handling System

MHS is a store-and-forward messaging service framework defined in early 3GPP releases, based on the ITU-T X.400 standards. It provides a standardized architecture for electronic mail and message interchange between users and applications, forming a foundational messaging infrastructure for telecom services.

Musical Instrument Digital Interface

A standardized protocol for transmitting musical performance and control data (note on/off, pitch, tempo) over digital networks. In 3GPP, it is adapted for streaming interactive, low-bandwidth musical content to mobile devices.

MCPTT Imminent peril Group

A predefined group within Mission Critical Push-To-Talk (MCPTT) services designated for emergency communications during imminent threat scenarios. It enables rapid, prioritized group calling for first responders and personnel in life-threatening situations, ensuring reliable and immediate coordination.

MCPTT Imminent peril Group Call

A specific type of group call established within an MCPTT Imminent peril Group (MIG). It is the actual communication session initiated when an imminent peril condition is active, providing the highest priority media path for emergency voice communication among group members.

Migration

A means for an MC Service user to obtain MC service directly from a partner MC system. It enables users to access mission-critical services when roaming or when their home system is unavailable.

More Instant Messaging Interoperability

A 3GPP framework enabling interoperability between different instant messaging services. It defines standardized protocols and interfaces to allow users on disparate platforms to exchange messages, addressing the fragmentation of the messaging ecosystem.

Mission Critical Applications

Generic communication applications with mission critical characteristics, including push-to-talk voice (MCPTT), real-time video (MCVideo), and real-time data (MCData). They provide critical communications over cellular networks.

Multi-Level Precedence and Pre-emption

A service feature that provides prioritized call handling and resource pre-emption in circuit-switched networks. It assigns precedence levels to calls, allowing high-priority calls (e.g., emergency, military) to seize resources from or queue ahead of lower-priority calls, ensuring critical communications get through during congestion.

Multimedia Call

Multimedia Call (MMC) refers to a communication service that integrates multiple media types, such as voice, video, and real-time text, within a single call session. It is a key concept in IMS (IP Multimedia Subsystem) and enables rich, interactive user experiences beyond traditional voice calls. MMC is fundamental to services like video telephony and enriched calling.

Multi-stream Multiparty Conferencing Media Handling

Multi-stream Multiparty Conferencing Media Handling (MMCMH) is an IMS Media Server capability defined for 5G that enables advanced conferencing services. It allows a Media Resource Function (MRF) to process multiple independent media streams (e.g., per-participant audio/video) for large-scale, interactive conferences. This supports features like selective forwarding and immersive spatial audio, enhancing the quality and flexibility of group communications.

Mobile Metaverse Enablement Client

A client-side entity enabling immersive metaverse experiences over 3GPP networks. It manages high-bandwidth, low-latency XR sessions and coordinates with network functions for QoS and edge computing. It is crucial for delivering next-generation extended reality services.

Massive Multiplayer Online

A service category in 3GPP for supporting massive-scale, interactive online gaming and applications over mobile networks. It defines network requirements for low latency, high reliability, and massive connectivity to enable real-time, synchronized experiences for thousands of concurrent users.

Multimedia Messaging Service

A standardized messaging service that enables the sending and receiving of multimedia messages containing text, images, video, and audio between mobile devices. It operates over cellular networks, using a store-and-forward mechanism via dedicated servers, and was a precursor to modern IP-based messaging.

Multimedia Messaging Service Relay/Server

The MMS Relay/Server is a core network entity in the Multimedia Messaging Service (MMS) that handles message transfer, storage, and MMS-specific operations. It acts as the central hub for multimedia messaging, enabling store-and-forward delivery and interworking with external networks.

Multimedia Messaging Service User Agent

An MMS User Agent is an application on a user device that performs MMS-specific operations on behalf of the user or another application. It interacts with the MMS Relay/Server to send, receive, and manage multimedia messages.

Multimedia Messaging Service Environment

The complete set of network elements, interfaces, and protocols that collectively enable the Multimedia Messaging Service (MMS). It encompasses the MMSC, associated databases, interworking functions, and the connections to external networks and value-added service platforms.

Multimedia Messaging Service Network Architecture

MMSNA is the standardized 3GPP framework defining the network architecture for Multimedia Messaging Service (MMS). It specifies functional entities, interfaces, and message flows to enable the exchange of rich multimedia content between users. This architecture is crucial for ensuring interoperability and consistent service delivery across different operator networks.

Multimedia Messaging Service Originator

MMSO is a functional role within the MMS architecture representing the entity (typically a user's device or application) that creates and submits a multimedia message for delivery. It initiates the MMS transaction by interacting with the MMS Relay/Server. This role is fundamental to the point-to-point and application-to-person messaging models.

Multimedia Messaging Service Recipient

The Multimedia Messaging Service Recipient (MMSR) is the user equipment or application that receives and processes Multimedia Messaging Service (MMS) messages. It is a key functional entity in the MMS architecture, enabling the delivery of rich media content such as images, audio, and video to end-users. Its role is critical for the success of MMS as a commercial service.

Multimedia Messaging Relay/Server

The Multimedia Messaging Relay/Server (MMSR/S) is a combined network element that performs both relay and server functions for the Multimedia Messaging Service (MMS). It handles the routing, storage, and interworking of multimedia messages between different networks and user agents. This integrated entity was part of the early MMS architecture.

Maritime Mobile Satellite Service

Maritime Mobile Satellite Service (MMSS) refers to satellite communication services that provide connectivity to ships and other vessels at sea. In 3GPP, it involves the integration of satellite access with terrestrial mobile networks to enable seamless maritime coverage. This is crucial for safety, operational communications, and passenger connectivity in maritime environments.

Multimedia Telephony

The 3GPP standardized service for real-time multimedia communication over IP networks, including high-quality voice, video, and text. It is the evolution of traditional circuit-switched telephony into a rich, IP-based multimedia experience, forming the basis for services like VoLTE and ViLTE.

Multi-stream Multiparty Video Conferencing

A 3GPP service enabling high-quality, multi-party video conferences where each participant can receive multiple independent video streams. It allows for dynamic layout control and selective viewing, enhancing the user experience for business and social conferencing over mobile networks.

Mobile Number Portability Signalling Relay Function

A network function that enables Mobile Number Portability (MNP) by routing signaling messages to the correct network after a subscriber has ported their number. It intercepts queries (like SRI) and uses a Number Portability database to determine the current serving network, ensuring calls and messages reach the ported subscriber.

Mobile Number Portability/Signalling Relay Function

A network function that enables mobile number portability (MNP) by intercepting and relaying signaling messages. It queries number portability databases to determine the correct recipient network for a call or session, ensuring seamless routing even when a subscriber has changed operators while keeping their number.

Mobile Number Portability Function

A 5G network function that provides mobile number portability services within the 5G Service-Based Architecture (SBA). It enables other network functions to query the current serving network for a ported MSISDN, supporting number portability for voice, SMS, and other services in a cloud-native environment.

MWI Notifier User Agent

A functional entity within the IP Multimedia Subsystem (IMS) that acts as a client for the Message Waiting Indication (MWI) service. It resides in the User Equipment (UE) and is responsible for subscribing to MWI event notifications from the network and handling the received indications, such as notifying the user of new voicemails. The MNUA enables a standardized, network-based voicemail notification service for IMS users.

Mobile Originated Location Request

MO-LR is a location service (LCS) feature that allows a mobile device to request its own geographical position or the position of another target device from the network. It enables user-initiated location applications like navigation, friend-finder services, and location-based information requests.

Mobile Originated Short Message Service

MO-SMS is the process where a mobile device initiates and sends a short text message to the network. It is a fundamental cellular service enabling person-to-person messaging, with standardized procedures across 3GPP generations from GSM to 5G.

Mobile Originated Application Terminated

MOAT is a 3GPP service capability where a mobile device initiates a request that leads to an application-terminated event, such as triggering a download or activating a remote service. It enables efficient device-triggered interactions in IoT and M2M scenarios.