3GPP Glossary

4G-Globally Unique Temporary Identifier

A temporary identifier assigned to a UE in 5G networks that originally registered via 4G E-UTRAN. It enables the 5G core network to uniquely identify and manage UEs that have performed inter-RAT mobility from 4G, maintaining continuity while protecting the user's permanent subscription identifier from exposure over the air interface.

5G Globally Unique Temporary Identifier

A temporary identifier assigned to a UE in 5G networks to protect the user's permanent subscription identity (SUPI). It is used for network access procedures, paging, and service requests, enabling efficient mobility and security by avoiding frequent transmission of the SUPI over the air interface.

5G S-Temporary Mobile Subscription Identifier

A temporary identifier assigned to a UE in the 5G system to protect the user's permanent subscription identity (SUPI) during initial network access and paging. It is used for radio resource control procedures and is a key element for privacy and efficient signaling.

5G Temporary Mobile Subscription Identifier

The 5G-TMSI is a temporary identifier assigned by the AMF to a UE for privacy and efficient signaling. It uniquely identifies the UE within a specific AMF set and is used to protect the permanent subscription identifier (SUPI) from exposure over the air interface.

AKMA Temporary UE IDentifier

A-TID is a temporary identifier assigned to a UE for AKMA (Authentication and Key Management for Applications) services. It enables application functions to securely request authentication and keying material from the network without exposing the UE's permanent identity. This is crucial for secure application-level authentication in 5G networks.

Application Identifier

AID is a standardized identifier used in UICC/SIM cards to uniquely identify applications, particularly for USIM and other telecom services. It enables multiple applications to coexist on a single smart card by providing a hierarchical addressing scheme. This is crucial for secure application management and interoperability across different mobile operators and service providers.

Application Level Subscriber Identity

ALSI is a subscriber identifier used at the application layer to uniquely identify users across different services and applications. It enables service providers to manage user identities independently from network-level identifiers, facilitating personalized services and authentication in value-added applications.

Application Layer User ID

ALUID is an application-layer identifier for 3GPP Proximity Services (ProSe) that enables user and application identification without revealing the user's permanent cellular identity. It provides privacy-preserving discovery and communication between nearby devices, supporting public safety and commercial proximity-based services.

Access Network Identity

ANID is a standardized identifier for a specific access network within 3GPP and non-3GPP systems. It enables the network to uniquely identify the point of attachment for a UE, which is crucial for mobility management, policy enforcement, and service continuity. Its standardized format ensures interoperability across different access technologies.

Address Of Record

AOR is a SIP URI that serves as a permanent, public identifier for a user in IMS networks. It uniquely identifies a subscriber for registration, routing, and service invocation purposes. This identifier is essential for session establishment and service delivery in 3GPP's IP Multimedia Subsystem architecture.

Access Point Name Network Identifier

The APN-NI is the network identifier portion of an Access Point Name (APN), a critical label used in 3GPP networks to determine the packet data network (PDN) gateway and external network a user equipment (UE) connects to. It is essential for routing user data traffic to the correct destination, such as the internet, an IMS network, or a private corporate network. Without proper APN-NI configuration, a UE cannot establish a data session or access network services.

Access Point Name Operator Identifier

The APN-OI is a component of the Access Point Name (APN) used in 3GPP networks to uniquely identify the operator's domain. It is crucial for routing user data traffic to the correct Packet Data Network Gateway (PGW) and for supporting inter-operator roaming scenarios. It ensures that data sessions are correctly anchored within the appropriate operator's network infrastructure.

Access Request Identifier

The Access Request Identifier (ARI) is a unique identifier assigned to a mobile station during the packet access procedure in GPRS/EDGE networks. It distinguishes the mobile's access request from others contending for the same resources on the PRACH, enabling the network to address the correct device during the uplink resource assignment phase. This mechanism is fundamental for managing contention resolution and establishing temporary identities for data transfer.

Access Transfer Update - Session Transfer Identifier

ATU-STI is a unique identifier used during IMS service continuity procedures to track and manage the transfer of multimedia sessions between different access networks. It ensures that session transfer requests are correctly associated with ongoing sessions, preventing misrouting and maintaining service continuity during handovers between 3GPP and non-3GPP networks.

Application Unique IDentity

AUID is a globally unique identifier for applications in 3GPP networks, standardized to enable secure application discovery, registration, and service invocation. It provides a standardized addressing mechanism for applications interacting with network functions, crucial for service layer interoperability and application portability across different operator environments.

Binding Identification Number

The Binding Identification Number (BID) is a unique identifier used in 3GPP networks to associate a user's IP address with a specific Packet Data Protocol (PDP) context or PDN connection. It is crucial for enabling IP flow mobility and seamless handovers between different access technologies, such as 3GPP and non-3GPP networks. Its primary role is to support multi-access connectivity and service continuity.

Basic Service Set Identifier

A unique 48-bit identifier for a Wi-Fi Basic Service Set (BSS), equivalent to a MAC address of an access point. In 3GPP standards, it's used for WLAN interworking to identify specific access points for network selection, mobility, and policy enforcement. This enables seamless integration between cellular and Wi-Fi networks.

BSS GPRS Protocol Virtual Connection Identifier

BVCI is a unique identifier used within the Gb interface between a Base Station Subsystem (BSS) and a Serving GPRS Support Node (SGSN) in 2G/3G networks. It identifies a virtual connection for GPRS data traffic, enabling multiplexing of multiple Packet Data Protocol (PDP) contexts over a single physical link. Its role is crucial for efficient resource management and routing of mobile packet data.

Cell Identifier

The Cell Identifier (C-ID) is a unique numerical label assigned to each cell within a 3GPP network, enabling precise identification and location of radio resources. It is fundamental for cell selection, handover procedures, and network management, ensuring mobile devices can correctly connect to and communicate with specific base stations.

Correlation Mobile Station International Subscriber Directory Number

C-MSISDN is a temporary MSISDN assigned to a User Equipment (UE) during a Voice Call Continuity (VCC) session to enable seamless handover between Circuit-Switched (CS) and IP Multimedia Subsystem (IMS) domains. It serves as a correlation identifier that allows the network to associate the CS-leg and IMS-leg of a single call, ensuring call continuity and proper routing during domain transfers.

Cell Radio Network Temporary Identifier

A temporary, unique identifier assigned by the gNB/eNB to a User Equipment (UE) for the duration of its connection within a specific cell. It is crucial for scheduling, resource allocation, and addressing the UE over the air interface, enabling efficient and secure radio resource management in the RAN.

Common Tunnel Endpoint Identifier

A shared tunnel identifier used in 3GPP networks to multiplex multiple traffic flows over a single GTP tunnel. It enables efficient resource utilization by allowing different bearers or services to share the same tunnel endpoint, reducing signaling overhead and simplifying tunnel management in packet core networks.

Cell Broadcast Message Identifier

CBMID is a unique identifier for Cell Broadcast (CB) messages in 3GPP networks. It allows the network and UE to distinguish between different broadcast messages, such as public warnings or location-based info. This is crucial for targeted message delivery and UE filtering.

Common Control Radio Network Temporary Identifier

CC-RNTI is a UE-specific identifier used in LTE and 5G NR for scheduling common control channel messages like paging and system information changes. It enables efficient, targeted delivery of critical broadcast information to specific UEs without requiring dedicated resources, optimizing network signaling and UE power consumption.

Capability/Configuration1 Identifier

CCI is a unique identifier used in 3GPP networks to represent specific UE capabilities or configurations. It enables efficient signaling by allowing networks to reference predefined capability sets rather than transmitting detailed capability lists. This reduces signaling overhead and speeds up connection establishment procedures.

Character Group Identifier

The CG-ID is a code used in 3GPP networks to identify a specific character group for Cell Broadcast Service (CBS). It enables the network to target broadcast messages to specific geographical areas or user groups, supporting public warning systems and location-based information dissemination.

Cell Global Identifier

The Cell Global Identifier (CGI) is a globally unique identifier for a cell in a mobile network, formed by combining the Mobile Country Code (MCC), Mobile Network Code (MNC), Location Area Code (LAC), and Cell Identity (CI). It is essential for network management, mobility procedures, location-based services, and lawful interception, enabling precise cell-level identification and routing across the entire network.

Cancellation Indication Radio Network Temporary Identifier

CI-RNTI is a UE-specific identifier used in 5G NR to indicate uplink transmission cancellation. It enables dynamic resource management by allowing the gNB to signal a UE to cancel scheduled uplink transmissions, improving resource utilization and reducing interference in dynamic TDD and multi-TRP scenarios.

Call Identifier Code / Circuit Identifier Code

CIC is a unique identifier used in circuit-switched networks to distinguish individual calls or physical circuits. It enables precise call routing, billing correlation, and network resource management across different network elements and interfaces.

Configured Scheduling Radio Network Temporary Identifier

CS-RNTI is a UE-specific identifier used in 5G NR for configured grant (CG) uplink transmissions. It enables semi-persistent scheduling without continuous DCI signaling, reducing control overhead and latency for periodic traffic patterns. This is crucial for URLLC and industrial IoT applications requiring deterministic low-latency communication.

Closed Subscriber Group Identity

CSG-ID is a unique identifier assigned to a Closed Subscriber Group (CSG) cell, which restricts access to a specific group of subscribers. It enables operators to create private or semi-private network cells, such as home NodeBs or enterprise femtocells, providing controlled access and differentiated services. This mechanism is crucial for implementing access control in hybrid access modes and supporting specialized deployment scenarios.

Closed Subscriber Group Identity

A unique identifier for a Closed Subscriber Group (CSG), which defines a set of subscribers permitted to access a specific cell, typically a Home NodeB (HNB) or Home eNodeB (HeNB). It enables operator-controlled restricted access, allowing only authorized users to connect to a femtocell or small cell, enhancing network security and resource management for private or enterprise deployments.

Cordless Telephony System Mobile Subscriber Identity

CTSMSI is a temporary subscriber identifier used in the 3GPP Cordless Telephony System (CTS) architecture. It uniquely identifies a CTS mobile station enrolled on a specific Cordless Telephony System Fixed Part (CTS-FP) during active sessions, enabling mobility management and secure communication within the CTS domain.

Drift Radio Network Temporary Identifier

A temporary identifier assigned by a Drift Radio Network Controller (DRNC) to a User Equipment (UE) during an inter-RNC soft handover in UTRAN. It uniquely identifies the UE's connection on the Iur interface between the Serving RNC (SRNC) and the DRNC, enabling efficient signaling and data forwarding.

Data Link Connection Identifier

A numerical label that uniquely identifies a specific Data Link Connection (DLC) within a data link layer protocol. It is used for multiplexing multiple logical connections over a single physical channel or interface. It is essential for routing frames to the correct higher-layer entity or service access point.

Data Link Discriminator

A parameter used in certain 3GPP core network signaling protocols to distinguish between different data link connections or signaling associations, particularly in the context of the Base Station System Application Part (BSSAP). It helps in routing messages to the correct procedural instance or context within a network node.

Data Network Identifier

A numerical code used in early 3GPP systems to uniquely identify a packet data network (PDN) that a UE can connect to, such as the internet or an operator service. It was part of the Access Point Name (APN) construct for network selection and routing.

Data Network Name

The Data Network Name identifies an external packet data network that a UE connects to, such as the internet or an IMS service. It is the 5G System (5GS) and Evolved Packet System (EPS) equivalent of the APN, used for session management, policy control, and charging.

MCData Payload Cipher Key Identifier

DPCK-ID is an identifier used in 3GPP Mission Critical Data (MCData) services to uniquely reference a specific MCData Payload Cipher Key (DPCK). It allows communicating endpoints to correctly identify which cryptographic key should be used to decrypt an incoming encrypted data payload.

MCData Payload Protection Key Identifier

An identifier used to uniquely reference a specific MCData Payload Protection Key (DPKK) within Mission Critical Data services. It enables efficient key management, retrieval, and synchronization between communicating endpoints, ensuring the correct key is used for payload encryption and decryption.

MCData Payload Protection Key Identifier

A unique identifier associated with a specific MCData Payload Protection Key (DPPK). It allows communicating MCData clients to identify which cryptographic key should be used to decrypt and verify a received protected payload.

E-DCH Radio Network Temporary Identifier

A temporary identifier assigned by the Node B to a UE for the purpose of addressing and identifying that UE on the Enhanced Dedicated Channel (E-DCH) in UMTS/HSPA. It is used on shared control channels like E-AGCH and E-RGCH to direct commands to a specific UE.

E-UTRAN Absolute Radio Frequency Channel Number

EARFCN is a unique numerical identifier that specifies the center frequency of a radio channel in LTE and 5G NR networks. It provides a standardized method to reference and manage frequency bands globally, ensuring interoperability between network equipment and user devices. This is crucial for network planning, deployment, and device configuration.

Edge Application Server Identification

A unique identifier for an Edge Application Server (EAS) in 3GPP edge computing. It enables the network and applications to discover, locate, and route traffic to the correct edge compute instance, which is critical for low-latency services like AR/VR and industrial automation.

EPS Bearer Identity

A unique numerical identifier assigned to each EPS bearer in LTE and 5G networks. It is used by network nodes to manage and differentiate traffic flows for a single UE, ensuring proper QoS handling and packet routing throughout the bearer's lifecycle.

E-UTRAN Cell Global Identification

ECGI is a globally unique identifier for an LTE cell, consisting of a PLMN ID and a Cell Identity. It is essential for network management, mobility procedures, and location-based services, enabling precise cell-level identification across the entire network.

Edge Enabler Client Identification

A unique identifier for an Edge Enabler Client (EEC) in 3GPP Edge Computing. It allows the network to uniquely identify and manage a client's edge application session, enabling service continuity, policy enforcement, and secure access to edge computing resources.

Edge Enabler Server Identification

Edge Enabler Server Identification (EESID) is a unique identifier for an Edge Enablement Server (EES) instance within a 3GPP edge computing system. It is used by network functions and clients to unambiguously refer to and route requests to a specific EES, especially in deployments with multiple EESs for scalability, redundancy, or different service domains. This identifier is crucial for service discovery and session management procedures.

Equivalent Home Public Land Mobile Network

EHPLMN is a list of network identifiers (PLMN IDs) considered equivalent to a user's Home PLMN (HPLMN) for network selection and roaming. It allows seamless service access across partner networks without being treated as roaming, improving user experience and enabling home-like services in visited networks.

EPC ProSe User ID

A unique identifier assigned to a user for Proximity Services (ProSe) in the Evolved Packet Core (EPC). It is used to discover and communicate directly with nearby ProSe-enabled devices without routing traffic through the network core, enabling device-to-device services.

Electronic Serial Number

The Electronic Serial Number (ESN) is a unique identifier assigned to mobile equipment, historically used for device authentication and registration in cellular networks. It serves as a hardware-based identity, crucial for network access control and preventing unauthorized device usage.

Fully Qualified Session Endpoint Identifier

A globally unique identifier for a session endpoint in the 5G Core network, combining a Session Endpoint Identifier (SEID) with the node's IP address. It enables precise routing and management of sessions across distributed network functions, essential for service-based architecture and network slicing.

Fully Qualified Tunnel Endpoint Identifier

A data structure used in GTP tunnels to uniquely identify a tunnel endpoint by combining a Tunnel Endpoint Identifier (TEID) with the endpoint's IP address. It is fundamental for routing user data packets between network nodes in 3GPP mobile networks, including 4G EPC and 5G interworking.

Flow Identifier

A unique identifier used to distinguish individual IP flows or service data flows within a 3GPP network. It is essential for applying specific QoS policies, charging rules, and traffic management to different data streams, enabling fine-grained control over user plane traffic.

Fixed Network Cable Residential Gateway Globally Unique AMF Identifier

FN-CRG is a globally unique identifier for the Access and Mobility Management Function (AMF) serving a Cable Residential Gateway in a 5G fixed network. It uniquely identifies the AMF instance managing the FN-CRG's control plane. This matters for precise routing of control signaling and mobility management in large-scale, multi-vendor 5G fixed networks.

Fixed Part Beacon Identity

A unique identifier for Fixed Parts (base stations) in cellular systems, used for network discovery and synchronization. It allows mobile devices to identify and select appropriate fixed infrastructure, supporting seamless mobility and network management.

Forbidden Public Land Mobile Network

The Forbidden Public Land Mobile Network (FPLMN) list is a stored record in a User Equipment's (UE) SIM/USIM. It contains the Mobile Country Code (MCC) and Mobile Network Code (MNC) combinations of networks the UE is temporarily forbidden from automatically selecting or registering onto, typically due to a previous failed registration attempt.

Fully Qualified Domain Name

A Fully Qualified Domain Name (FQDN) is the complete, unambiguous domain name for a host or network node, specifying its exact location in the Domain Name System (DNS) hierarchy. In 3GPP, FQDNs are extensively used in URIs to identify network functions (NFs), endpoints, servers (e.g., for PCC, IMS, NRF), and for DNS-based service discovery, forming the foundation for IP-based signaling and service delivery.

Group Configured Scheduling Radio Network Temporary Identifier

A radio network identifier used in 5G NR for group-based configured scheduling, primarily for IoT and MTC. It enables efficient resource allocation for multiple UEs sharing the same semi-persistent scheduling configuration, reducing signaling overhead and power consumption for periodic small data transmissions.

GERAN Radio Network Temporary Identity

A temporary identifier assigned by the network to a mobile station (MS) for communication over the GERAN radio interface. It uniquely identifies the MS on shared radio channels (like PACCH) for efficient addressing during data transfer, paging, and resource assignment in GPRS/EDGE networks.

Geographical Area Identifier

A unique identifier assigned to a defined geographical area within a 3GPP network. It is used to reference specific zones for location-based services, policy enforcement, and network management without transmitting full geographical coordinates.

Global Cable Identifier

The Global Cable Identifier (GCI) is a unique identifier used within 3GPP specifications to unambiguously identify a cable network access point or a cable modem. It plays a role in fixed-mobile convergence, enabling authentication and service provisioning for devices connecting via cable broadband networks.

Global Call Reference

Global Call Reference (GCR) is a unique identifier assigned to a call or session across multiple network domains and administrative boundaries. It enables end-to-end correlation of charging records, fault management, and lawful interception data for a specific communication instance, which is critical for inter-operator and inter-network scenarios.

Group Identifier (level 1)

GID1 is a file identifier stored on a USIM/UICC card, defined in the EF(GID1) elementary file. It is used by the network to identify a group or category of subscribers, often for applying specific network services, access controls, or commercial offerings to an entire user group.

Group Identifier (level 2)

GID2 is a secondary group identifier stored on a USIM/UICC card in the EF(GID2) file. It provides an additional, operator-defined grouping criterion beyond GID1, allowing for more granular subscriber categorization, hierarchical group structures, or separate classification schemes within the network.

Group ID for Network Selection

An identifier introduced in 5G to represent a group of networks (e.g., a roaming consortium) for prioritized network selection and access control. It enables devices to select a preferred network from a group, enhancing roaming user experience and network resource management.

Global Line Identifier

A globally unique identifier for a fixed network access line, standardized in 3GPP for 5G convergence. It unambiguously identifies a physical line (e.g., DSL, fiber) connecting a customer premises to the network, enabling integrated authentication, policy, and management across fixed and mobile domains.

Generic Number

Generic Number (GN) is a flexible addressing parameter used in 3GPP signaling, particularly in CAMEL and IMS. It represents various types of numbers (e.g., MSISDN, service numbers) in a generic format, enabling the transport of diverse addressing information across network interfaces for service logic execution and routing.

GSM PLMN Area

GSM PLMN Area (GPA) is a geographical area identifier used within GSM networks to define a specific region served by a Public Land Mobile Network. It is a network planning and operational concept for area-based services and subscriber management.

Generic Public Subscription Identifier

A globally unique, public identifier for a 3GPP subscription, such as an MSISDN or an External Identifier, used to address a user across different network domains and in communication with external application servers. It is a key identifier in 5GC for service exposure and edge computing.

Globally Routable User agent URI

A globally routable URI that uniquely identifies a specific User Agent (UA) instance, such as a SIP phone or soft client. It enables direct, secure, and efficient end-to-end communication for IMS-based services like VoLTE and VoNR, bypassing the need for complex routing through multiple proxies.

GSM Service Identity Module

The GSM Service Identity Module (GSIM) is a conceptual module or identifier used in early 3GPP specifications, particularly for GPRS, to represent the subscription and service profile for packet data services. It conceptually separated the service identity from the physical SIM card, outlining the data needed for packet network access.

Global Title

An address used in SS7 signaling to route messages between network nodes when the final destination's point code is unknown. It is a key identifier for entities like HLRs, SMSCs, and SCPs, enabling global roaming and service delivery in mobile networks.

Globally Unique AMF Identifier

The Globally Unique AMF Identifier (GUAMI) is a critical identifier in 5G networks that uniquely identifies an Access and Mobility Management Function (AMF) instance globally. It is used during registration, handover, and paging procedures to route signaling messages to the correct AMF, enabling efficient mobility management and network scalability.

Globally Unique MME Identifier

A globally unique identifier for a Mobility Management Entity (MME) in EPS and 5GS. It combines the PLMN identity with an MME Group ID and an MME Code to uniquely pinpoint an MME worldwide, enabling correct routing of signaling messages for mobility management and session establishment.

Globally Unique Temporary UE Identity

The Globally Unique Temporary UE Identity (GUTI) is a temporary identifier assigned to a User Equipment (UE) by the network to protect the user's permanent subscription identity (SUPI/IMSI). It is used for most signaling procedures in EPS and 5GS, enhancing privacy and efficiency by avoiding frequent transmission of the permanent ID over the air interface.

HS-DSCH Radio Network Temporary Identifier

The HS-DSCH Radio Network Temporary Identifier (H-RNTI) is a UE-specific identifier used in UMTS/HSPA networks to address a user on the High-Speed Downlink Shared Channel (HS-DSCH). It is assigned by the Node B and used for scheduling and data transmission on the shared downlink channel. This identifier is crucial for efficient resource allocation and multiplexing in HSPA systems.

Homogeneous Extended Service Set Identifier

HESSID is a unique identifier for a Wireless Local Area Network (WLAN) that facilitates seamless integration and interworking with 3GPP cellular networks. It is used in Access Network Discovery and Selection Function (ANDSF) policies and WLAN network selection to identify trusted or preferred WLAN access points for offloading.

Hyper Frame Number

The Hyper Frame Number (HFN) is a counter used in 3GPP protocols to extend the range of sequence numbers, particularly for ciphering and integrity protection. It works in conjunction with shorter Sequence Numbers (SN) to form a longer COUNT parameter, ensuring cryptographic synchronization and preventing replay attacks over long periods in mobile communications.

Huffman Initialization ID

HI-ID is an identifier used in the 3GPP Short Message Service (SMS) protocol to indicate the Huffman table used for character encoding. It ensures the correct decoding of compressed text in SMS messages, particularly for languages with large character sets.

Home Network Prefix

A Home Network Prefix (HNP) is a network prefix assigned to a mobile node in IP-based mobility protocols like DSMIPv6. It serves as the mobile node's stable, topologically correct home address, allowing it to maintain ongoing sessions while moving across different access networks. It is a fundamental concept for network-based mobility management.

Home Public Land Mobile Network

The mobile network where a subscriber's permanent subscription data is held. It is the subscriber's 'home' network, crucial for authentication, billing, and service provisioning. It enables roaming by distinguishing the home network from visited networks (VPLMN).

Home Public Land Mobile Network of the B subscriber

The HPLMN of the called party (B-party) in a communication session. It is used in call routing, billing, and service logic (e.g., CAMEL) to identify the home network of the recipient, which may influence how the call is processed and charged.

Home Public Land Mobile Network of the C subscriber

The HPLMN of a third party (C-subscriber) involved in a communication service, such as in a call forwarding or conference scenario. It identifies the home network of a party other than the primary caller (A) or callee (B), used for specialized routing and service control.

Hosting Party Subscription Identity Module

The Hosting Party Subscription Identity Module is a logical entity defined for Machine-to-Machine (M2M) communications. It represents the subscription of a hosting party, which is an entity that provides connectivity or services for M2M Devices. It enables separate billing and management for the service enabler versus the end-user device.

Human Readable Network Name

A text string displayed on a User Equipment (UE) to identify the serving Public Land Mobile Network (PLMN) or a Non-Public Network (NPN). It provides a user-friendly network name (e.g., 'Company 5G Private Network') instead of or in addition to the numeric Mobile Country Code (MCC) and Mobile Network Code (MNC).

Inactive RNTI

The I-RNTI is a temporary Radio Network Temporary Identifier used in 5G NR to uniquely identify a User Equipment (UE) in the RRC_INACTIVE state. It enables efficient paging and quick resumption of the connection without full re-establishment, reducing signaling overhead and power consumption for infrequent data transmissions.

IMS Application Reference Identifier

A globally unique identifier for an IMS application, enabling network and UE to identify and manage specific services like voice, video, or messaging. It is crucial for service discovery, policy control, and ensuring consistent user experience across different devices and networks.

Integrated Circuit Card Identification

A unique serial number permanently embedded in a SIM (Subscriber Identity Module) or UICC (Universal Integrated Circuit Card). It identifies the physical hardware of the card itself and is essential for inventory management, card personalization, and network provisioning processes.

IM CN subsystem Charging Identifier

A unique identifier used within the IP Multimedia Subsystem (IMS) charging architecture to correlate charging data records (CDRs) generated by different network functions during a single service session. It ensures all usage events for a session can be accurately assembled for billing.

Identity / Identifier

A fundamental concept in 3GPP networks representing a unique name or label for a network entity, user, or resource. It is crucial for addressing, routing, authentication, and managing subscriber data across the entire system.

International Fixed Part Equipment Identity

A unique identifier for Fixed Part (FP) equipment in a DECT (Digital Enhanced Cordless Telecommunications) system that is part of a 3GPP IMS-based Fixed Mobile Convergence (FMC) solution. It is used for equipment registration, authentication, and management within the network.

International Mobile Station Equipment Identities

A globally unique 15-digit number that permanently identifies a mobile device (phone, tablet, modem). It is used by networks for device identification, validation, and security functions like blacklisting stolen equipment.

International Mobile Equipment Identity Software Version

A 16-digit extension of the IMEI that includes a two-digit software version number. It identifies the specific software/firmware version installed on the mobile device, aiding in device management and software update tracking.

Type Allocation Code part of an IMEI

The initial 8-digit segment of an IMEI or IMEI-SV that identifies the device's model and manufacturer. It is a globally unique code allocated to a device model batch, used for device type recognition and regulatory approval.

International Mobile Equipment Identity Type Allocation Code

The IMEI/TAC is the initial eight-digit segment of the full IMEI, uniquely identifying the model and manufacturer of a mobile device. It is crucial for device type approval, network access control, and regulatory compliance, enabling operators to manage device populations and implement security policies.

International Mobile station Equipment Identity and Software Version number

The IMEISV is a 16-digit identifier combining the device's unique IMEI with a two-digit Software Version Number (SVN). It provides precise identification of both the hardware model and the specific software/firmware revision installed, essential for advanced device management, security patches, and feature enablement.

International Mobile Group Identity

The IMGI is a unique identifier used primarily in GSM and UMTS networks to address a specific group of Mobile Stations (MS) for group-based services like Voice Group Call Service (VGCS) and Voice Broadcast Service (VBS). It enables efficient one-to-many communication for public safety and professional mobile radio applications.

IP Multimedia CN subsystem Private Identity

A permanent, globally unique private identifier for a user within the IMS (IP Multimedia Subsystem). It is used for authentication and registration, stored in the HSS and ISIM application, and is not shared publicly. It is fundamental for secure access to IMS services.

IP Multimedia Public User Identity

A public SIP URI or TEL URI used to address a user for multimedia communications within the IMS, such as making a voice or video call. One user can have multiple IMPUs for different services or contexts, and they are registered and associated with the private IMPI for service authorization.

IP Multimedia Routeing Number

A temporary E.164 number assigned to enable routing of IP Multimedia Subsystem (IMS) sessions to a roaming user when the visited network lacks IMS-level roaming interfaces. It acts as a bridging identifier to facilitate session continuity and service delivery.

International Mobile Subscriber Identity

The IMSI is a globally unique permanent identifier assigned to a subscriber in a mobile network, stored on the SIM/USIM. It is used by the network to identify and authenticate the subscriber, retrieve their profile from the HSS, and establish mobility and session management contexts. It is fundamental to all cellular network operations.

International Mobile User Identity

The International Mobile User Identity (IMUI) was a unique identifier for a mobile user, defined in early 3GPP releases. It was part of the user identification framework but was superseded by more permanent and standardized identifiers like the IMSI as the GSM/UMTS systems evolved.

International Mobile User Number

The International Mobile User Number (IMUN) is a dialable number format defined by 3GPP, based on the E.164 international numbering plan. It is used to uniquely identify a mobile user for the purpose of establishing multimedia communication sessions, such as video calls, within IMS-based networks.

IMS Network-Independent Public User Identity

INIPUI is a public user identity in the IP Multimedia Subsystem (IMS) that is independent of the underlying access network. It allows users to be identified consistently across different network types, such as LTE, Wi-Fi, or fixed broadband, enabling seamless multimedia services like voice and video over IP. This identity supports mobility and service continuity in IMS-based communications.

Interruption RNTI

INT-RNTI is a Radio Network Temporary Identifier used in 5G NR to signal uplink transmission interruptions. It identifies UEs that need to pause uplink transmissions for measurements or interference mitigation. This is crucial for network efficiency and coexistence in shared spectrum.

Inter Operator Identification

IOI is a globally unique identifier used in 3GPP networks to distinguish between different service providers or network operators involved in a communication session. It is essential for routing, billing, and service differentiation in inter-operator scenarios, such as roaming and interconnect agreements.

ITS Application Identifier

A unique identifier for Intelligent Transport Systems (ITS) applications, standardized by 3GPP. It enables network and devices to recognize and manage specific V2X services, ensuring proper routing, security, and QoS for critical vehicular communications like collision warnings.

Individual TETRA Subscriber Identity

A unique identifier for a subscriber (user or device) in a TETRA (Terrestrial Trunked Radio) network. It is the core identity used for authentication, mobility management, and call routing within TETRA systems, which are critical for professional and public safety mobile communications.

International Mobile Subscriber Station Identity

The IUEI is a unique identifier for a mobile subscriber station, standardized in early 3GPP releases. It serves as a key identifier for subscriber equipment in international mobile networks, facilitating roaming and subscriber management. Its introduction in R99 provided a foundational identity element for UMTS networks.

International USIM Identifier

The IUI is a unique identifier for the USIM (Universal Subscriber Identity Module) in mobile networks, introduced in 3GPP Rel-4. It distinguishes individual USIM applications on UICC cards, enabling secure subscriber authentication and service management. Its persistence across releases underscores its role in identity and security frameworks.

Location Area Identity

A unique identifier for a Location Area (LA) within a Public Land Mobile Network (PLMN). It is used in mobility management to track and page UEs, consisting of a Mobile Country Code (MCC), Mobile Network Code (MNC), and Location Area Code (LAC).

LCR TDD Absolute Radio Frequency Channel Number

A unique numerical identifier used to specify the exact carrier frequency for Low Chip Rate (LCR) Time Division Duplex (TDD) operations in UTRA. It provides a standardized method for frequency planning and channel assignment, ensuring unambiguous communication between network elements.

Linked Bearer Identity

An identifier that links a dedicated bearer to its associated default bearer within the same PDN connection. It establishes a hierarchical relationship where the default bearer provides the control plane anchor and the linked dedicated bearer carries additional traffic flows with specific QoS.

Logical Channel Identifier

LCID is a unique identifier used in 3GPP protocols to distinguish between different logical channels within a radio bearer. It enables multiplexing and demultiplexing of data streams, ensuring correct routing and prioritization of traffic between the user equipment and network.

Local Home Network Identifier

An identifier used in LTE and 5G NR to distinguish a specific Local Home Network, such as a residential, enterprise, or neutral host network. It is used by the RAN for access control, mobility management, and to apply network-specific policies for UEs connected via Home eNodeBs or gNBs.

Local Home Network Identifier

An identifier for a local home network, used in 3GPP specifications to differentiate and manage access for devices within a specific local network domain. It is crucial for enabling localized services and access control, particularly in residential or enterprise small cell deployments.

LMA Address

LMA Address (LMAA) is the IP address of the Local Mobility Anchor (LMA) function, used as the tunnel endpoint in Proxy Mobile IPv6 (PMIPv6) signaling and data forwarding. It is the destination address for Proxy Binding Update messages from the MAG and the source for tunneled user plane traffic destined for the UE.

Local Mobile Station Identity

A temporary identifier assigned to a mobile station (UE) by a Visitor Location Register (VLR) for local management within its service area. It is used to uniquely address the subscriber for signaling and service handling, reducing the need to transmit the permanent IMSI over the air interface for improved security and efficiency.

Local Public Land Mobile Network

LPLMN is a network identifier representing a user's home or primary network operator within a specific geographical area. It is crucial for subscriber identification, roaming agreements, and network selection procedures, ensuring users can connect to their home network when available.

Location Routing Number

A unique number used in North American telecommunications to route calls to a specific geographic location or ported number. It enables number portability by separating the dialed number from the actual routing address, ensuring calls reach the correct service provider's network.

Localised Service Area Identity

A unique identifier for a Localised Service Area (LSA), a defined geographical zone within a PLMN where specific services or policies are applied. It enables network operators to offer differentiated services, such as special tariffs or access restrictions, based on a user's precise location within the network.

MBMS Radio Network Temporary Identifier

A temporary identifier used in the LTE radio interface to address User Equipment (UE) for Multimedia Broadcast Multicast Service (MBMS) transmissions. It enables efficient group scheduling and control signaling for broadcast/multicast traffic over a specific MBSFN area.

M-Temporary Mobile Subscriber Identity

A temporary subscriber identifier used in the EPS mobility management (EMM) procedures between the UE and the MME. It provides user identity privacy on the radio interface by concealing the permanent IMSI and is used for paging and service requests.

Frequency Selection Area Identity

MBS, as Frequency Selection Area Identity, is an identifier used in 5G networks to manage frequency selection areas for broadcast and multicast services. It helps the network efficiently allocate and manage radio resources for delivering content to multiple users simultaneously, optimizing spectrum usage.

Mission Critical User Identity

A unique identifier for users and devices within 3GPP Mission Critical (MC) services, such as MCPTT, MCVideo, and MCData. It enables secure, prioritized communication for public safety and critical industry users, ensuring proper authentication, authorization, and service continuity across networks.

Mobile Country Code

The Mobile Country Code (MCC) is a three-digit numerical code that uniquely identifies the home country of a mobile network subscriber. It is the first part of the International Mobile Subscriber Identity (IMSI) and is fundamental for international roaming, network selection, and subscriber identification in global mobile networks.

MBS Control Channel RNTI

A Radio Network Temporary Identifier (RNTI) introduced in 5G NR for the specific purpose of scrambling and identifying PDCCH transmissions that carry scheduling assignments for the Multicast Control Channel (MCCH). It enables UEs to efficiently monitor and decode the downlink control information required to receive MBS control messages.

Mobile Equipment Identity

A globally unique identifier for a mobile device (UE), distinct from the user's SIM card. It is used by the network for equipment identification, tracking, and security functions like blacklisting stolen devices.

Mobile Equipment IDentity

A globally unique identifier for mobile equipment, primarily used in 3GPP2 (CDMA) systems but also defined for interworking with 3GPP networks. It serves a similar purpose to the IMEI but with a different format and historical origin.

Mobile Global Title

A unique address used in the SS7/SIGTRAN-based core network to identify and route signaling messages to mobile network entities, such as HLRs, MSCs, or SGSNs. It is crucial for enabling reliable, network-wide signaling and subscriber management in 2G, 3G, and early 4G networks.

Mobile Network Code

A 2- or 3-digit code that uniquely identifies a mobile network operator within a country. It is a core component of the International Mobile Subscriber Identity (IMSI), enabling subscriber identification, roaming, and network routing. Its standardization is fundamental for global interoperability.

Mobile Station Class Mark

A legacy identifier used in GSM and early 3GPP releases to classify a mobile station's capabilities, such as its power class and supported frequency bands. It was transmitted by the MS to the network to enable appropriate service provisioning and radio resource management.

Mobile Station Identifier

MSID is a generic term for any identifier used to uniquely distinguish a Mobile Station (UE) within a mobile network. It serves as an umbrella concept for specific identifiers like IMSI, TMSI, and IMEI, which are used for different purposes such as subscription, temporary tracking, and device recognition.

Mobile Station Identification Number

The MSIN is the core, nationally significant part of the International Mobile Subscriber Identity (IMSI). It uniquely identifies a subscriber within a specific mobile network operator's domain and is used by the operator's HLR/HSS to locate the subscriber's profile and service data.

Mobile Station International Subscriber Directory Number

The MSISDN is the public telephone number used to call a mobile subscriber. It is a globally unique E.164 number stored in the HLR/HSS and is fundamental for routing calls and SMS in circuit-switched and IMS networks.

Mobile Subscriber Roaming Number

A temporary E.164 number assigned to a roaming mobile subscriber. It enables the Public Land Mobile Network (PLMN) to route incoming calls to the visited network's Mobile Switching Center (MSC) serving the subscriber, ensuring call delivery while roaming.

Mobile User Identifier

A generic term for any identifier that uniquely distinguishes a mobile user or subscriber within a network. It is an umbrella concept encompassing various specific identifiers like IMSI, TMSI, and MSISDN used across different network domains and protocols for routing, security, and management.

Network Access Identifier

The Network Access Identifier (NAI) is a standardized user identity format used in network access authentication, particularly in roaming scenarios. It follows the structure 'user@realm', where the 'realm' part identifies the user's home network domain. The NAI is fundamental to protocols like EAP, RADIUS, and Diameter, enabling unambiguous identification of users and proper routing of authentication requests to their home network.

Network (PLMN) Colour Code

A 3-bit identifier used to differentiate between Public Land Mobile Networks (PLMNs) sharing the same Location Area Code (LAC) or Routing Area Code (RAC). It is crucial for network selection, cell reselection, and handover procedures, especially in border areas or with network sharing agreements.

NR Cell Global Identifier

A globally unique identifier for a 5G NR cell, combining the PLMN ID and the NR Cell Identity (NCI). It enables unambiguous cell identification across networks for mobility management, location services, and network analytics.

National Destination Code

A numeric prefix used in international telephone numbering plans to identify a specific country or geographic region. It is a critical component of the E.164 numbering plan, enabling global call routing and subscriber identification across different national networks.

Network Element Identifier

A Network Element Identifier (NEID) is a unique label used within 3GPP security and management frameworks to distinctly identify a specific network element, such as a base station, core network node, or management system. It is crucial for secure communication, auditing, and fault management in multi-vendor networks.

Network Identifier

The mandatory part of an Access Point Name (APN) that identifies the external packet data network (PDN) or service a UE wants to connect to, such as the internet or an IMS network. It is a domain name label (e.g., 'internet', 'ims') used by the network to select the correct Packet Data Network Gateway (PGW) and establish the appropriate data session.

Network Identifier

NID is a unique identifier used in conjunction with a PLMN ID to form a full identifier for a Stand-alone Non-Public Network (SNPN). It allows private 5G networks to be uniquely identified and selected by devices, enabling operation independent of public mobile network operators.

National Mobile Station Identifier

A unique identifier assigned to a mobile station (MS) for national use within a specific country's network. It serves as a key for subscriber identification and routing in national contexts, distinct from international identifiers like the IMSI. It is crucial for national regulatory and operational purposes.

Numbering Plan Identifier

A code used in telecommunications to identify the specific numbering plan (e.g., E.164, E.212) associated with a dialed or subscriber number. It is crucial for proper call routing and subscriber identification across different network types and international boundaries.

Number range holder network of the B subscriber

Identifies the mobile network that holds the numbering range (MSISDN block) for the called party (B-subscriber). It is used in call routing and billing, particularly for ported numbers, to distinguish the original service provider from the current serving network.

NR Absolute Radio Frequency Channel Number

NR-ARFCN is a unique numerical identifier used in 5G NR to specify the center frequency of a radio channel. It provides a standardized way to reference and manage frequency bands across different NR deployments and equipment. This identifier is essential for frequency planning, band support indication, and ensuring interoperability between user equipment and networks.

Network Resource Identifier

A part of the Temporary Mobile Subscriber Identity (TMSI) used in GSM, UMTS, and LTE systems to route signaling messages to the correct core network node (MSC or SGSN) within a pool area. It enables efficient subscriber mobility management and load balancing across multiple core network elements.

Network Service Virtual Connection Identifier

A unique identifier for a Network Service Virtual Connection (NS-VC) on the Iur-g interface. It distinguishes individual logical connections used to transport synchronization information between a BSC and a BSS Network Synchronization Server, enabling proper routing and management.

Network Service Virtual Link Identifier

The NS-VLI is a unique identifier for a Network Service Virtual Link (NS-VL) within the 3GPP management framework. It is used to distinguish and manage logical communication paths between network functions, enabling automated service provisioning and lifecycle management. This identifier is crucial for network slicing and service orchestration.

Network layer Service Access Point Identifier

A numerical identifier that uniquely labels a specific Network Service Access Point (NSAP) within a mobile station and the network. It is used to distinguish between multiple simultaneous packet data protocol (PDP) contexts, enabling independent management of different data sessions and their associated QoS profiles.

Network Service Entity Identifier

A unique identifier for a Network Service Entity (NSE) within the GPRS network, specifically used in the Gb interface between the BSS and the SGSN. It is crucial for managing and routing data traffic across the packet-switched core network, enabling the SGSN to distinguish between different BSS entities and their associated services.

National User Identifier / USIM Identifier

The National User Identifier (NUI) is a unique identifier stored on a USIM card, used primarily for legal interception and national security purposes within a specific country. It allows national authorities to uniquely identify a subscriber independently of the international IMSI. Its existence is critical for complying with regional regulatory requirements for user identification.

Operator Identifier

A unique identifier for a mobile network operator, forming part of the Access Point Name (APN). It is used in the Packet Data Network (PDN) connectivity process to route user data traffic to the correct operator's network and services.

Organisation Identifier

A globally unique identifier assigned to an organization, such as a standards body (e.g., ITU-T, 3GPP) or a vendor. It is used within management protocols and information models to unambiguously identify the defining authority for managed objects, attributes, and other entities.

Operation and Maintenance Centre Identity

The Operation and Maintenance Centre Identity (OMC-ID) is a unique identifier assigned to an OMC within the Evolved Packet System (EPS). It is used in management and signalling procedures, particularly for tracing activities, to unambiguously identify the management system that initiated a specific operation or trace.

Open Mobile Naming Authority

The Open Mobile Naming Authority (OMNA) is a 3GPP-managed registry for assigning unique identifiers used within mobile network protocols and services. It ensures global uniqueness for parameters like Service Access Point Identifiers (SAPIs), Protocol Identifiers, and other enumerated values critical for interoperability. OMNA prevents conflicts and enables standardized communication between network elements and services from different vendors.

Operator Controlled PLMN (Selector List)

The Operator Controlled PLMN Selector List (OPLMN) is a list of preferred Public Land Mobile Networks stored on a UE's SIM/USIM. It is provided by the home operator to guide network selection, especially when roaming, prioritizing partner networks. This ensures reliable service and can control roaming costs.

Organizational Unique Identifier

A globally unique identifier assigned to an organization by the IEEE Registration Authority. In 3GPP, it is used within the context of Edge Computing to identify application clients and servers, enabling service discovery and secure communication between entities.

Paging Radio Network Temporary Identifier

A temporary identifier used by the network to page UEs in idle or inactive mode. It is broadcast on the PDCCH to indicate a paging message is present on the PDSCH, enabling efficient battery saving and network-initiated reachability.

Push Temporary Identifier

A temporary identifier used in the Push-to-talk over Cellular (PoC) service to uniquely and anonymously identify a PoC client during a session. It provides user privacy by avoiding the transmission of permanent identities like the MSISDN over the air interface.

Packet-Temporary Mobile Subscriber Identity

A temporary identity assigned by the SGSN to a UE in the GPRS/UMTS packet-switched domain. It protects the user's permanent IMSI from frequent transmission over the air interface, enhancing security and privacy, and is used for core network signaling procedures like routing area updates.

PhoneBook IDentifier

A unique identifier used in USIM applications to reference phonebook entries stored on the UICC. It enables efficient management and access to contact information, linking entries across different phonebook applications or services.

ProSe Discovery UE ID

A unique identifier assigned to a User Equipment (UE) for Proximity Services (ProSe) Direct Discovery, enabling one UE to discover other UEs in its vicinity without cellular network infrastructure. It is a critical component for enabling device-to-device (D2D) communication and public safety services. The PDUID ensures privacy and manages the lifecycle of discovery announcements and monitoring.

Permanent Equipment Identifier

A globally unique, permanent identifier for a 3GPP User Equipment (UE). It is used for device identification, registration, and security procedures, distinct from the subscriber's identity. It is crucial for device authentication, fraud prevention, and regulatory requirements like lawful interception.

Public Land Mobile Network

A network operated by an administration or a recognized operating agency (ROA) to provide land mobile telecommunications services to the public. It is uniquely identified by a Mobile Country Code (MCC) and Mobile Network Code (MNC), forming the basis for subscriber roaming and network selection.

Power Saving Radio Network Temporary Identifier

A UE-specific RNTI introduced in 5G NR to enable power saving. It is used by the gNB to schedule and transmit power saving signals and commands to a UE in RRC_CONNECTED state, allowing the UE to enter micro-sleeps and reduce power consumption without losing connectivity.

Provider Service Identifier

A unique identifier for a V2X service provider, enabling secure and authorized service access in vehicle-to-everything communications. It is crucial for service discovery, authentication, and ensuring that only authorized vehicles or devices can access specific V2X applications and data.

PUnctuator ID

PU-ID is an identifier for a PUnctuator, a network element used in early 3GPP specifications for text-based services like SMS. It uniquely identifies the punctuator within the network for message handling and routing purposes.

Public User Identity

A globally routable identifier used in the IP Multimedia Subsystem (IMS) to address a user for multimedia communications, such as SIP URI or TEL URI. It is the external address used by others to initiate sessions (e.g., calls, messages) toward a subscriber.

Preconfigured Uplink Resource Radio Network Temporary Identifier

PUR-RNTI is a unique identifier used in 3GPP networks to address UEs configured with Preconfigured Uplink Resources (PUR). It enables efficient downlink signaling, such as acknowledgments or scheduling commands, in response to PUR-based transmissions, reducing overhead and improving IoT communication efficiency.

Removable User Identity Module

A smart card defined by the 3GPP2 standards body for CDMA2000 networks, functionally similar to the SIM card in GSM/UMTS. It securely stores subscriber identity (IMSI), authentication keys, and applications, enabling user mobility between devices. While a 3GPP2 term, it is referenced in 3GPP specs for interworking and multimode device considerations.

Random Access Radio Network Temporary Identifier

RA-RNTI is a temporary identifier used in the LTE and NR Random Access procedure. It is calculated by the UE based on the time-frequency resource of its Random Access Preamble transmission. The network uses the same RA-RNTI to address the UE in the initial response message, enabling contention resolution in the uplink.

Routing Area Identity

A location area identifier used in 2G (GPRS) and 3G (UMTS) packet-switched core networks. It uniquely identifies a Routing Area (RA) within a PLMN and is used for mobility management, specifically for paging and tracking mobile devices in idle or ready states for packet data services.

Relative Distinguished Name

A component of an X.500 Distinguished Name (DN) that uniquely identifies an entry within its immediate parent context in a hierarchical directory, such as a Management Object (MO) in 3GPP network management. It is a key-value pair used for structuring and addressing managed resources.

Radio Network Temporary Identifier

A temporary identifier assigned by the Radio Access Network (RAN) to a User Equipment (UE) for communication over the air interface. It is crucial for addressing and distinguishing users in the cell, managing scheduling, and ensuring secure and efficient data transmission in LTE and 5G NR.

RP SME-Address

An address field within the Relay Protocol (RP) used in SMS over IMS. It carries the address of the Short Message Entity (SME), which is typically the originating or destination MSISDN (phone number) for an SMS. It is essential for identifying the sender and recipient in the SMS delivery path.

Restricted ProSe Application User ID

A privacy-preserving identifier used in ProSe (Proximity Services) for direct device-to-device communication. It allows a user's application to be identified for service authorization and discovery without revealing the user's permanent subscription identity, enhancing privacy in proximity-based services.

Registered SNPN

RSNPN is a network identifier for a Standalone Non-Public Network (SNPN) where a UE is successfully registered. It enables secure and isolated private network access, crucial for enterprise and industrial IoT deployments requiring dedicated 5G infrastructure.

Regional Subscription Zone Identity

RSZI is a code identifying a geographical area where a subscriber is permitted to use services, enabling regional subscription control. It allows operators to restrict service usage to specific zones, supporting tariffing and regulatory compliance. This is crucial for managing roaming and location-based service offerings.

Secondary Enhanced Radio Network Temporary Identifier

A secondary temporary identifier used in UMTS/HSPA to distinguish a specific UE's Enhanced Uplink resources during a communication session. It is used alongside the primary E-RNTI for scenarios like serving cell change or specific MAC-e/es protocol operations, providing robust identification and control.

Serving Radio Network Temporary Identifier

A temporary identifier assigned by the RNC to a UE in UTRAN for the duration of a connection. It uniquely identifies the UE within the serving RNC's context, enabling efficient radio resource management and signaling. It is crucial for maintaining the RRC connection state and directing messages to the correct UE.

SAE Temporary Mobile Subscriber Identity

A temporary identifier assigned by the MME to a UE in the EPS. It is used to protect the user's permanent identity (IMSI) during signaling procedures like paging and service requests, enhancing privacy and reducing signaling overhead on the radio interface.

Service Area Identifier

A unique identifier for a Service Area, which is a group of cells within a Location Area. It is used in UMTS and LTE networks for location-based services, paging optimization, and mobility management. The SAI enables efficient subscriber tracking and service delivery.

Service Access Point Identifier

A numerical identifier used in data link layers (like LAPDm in GSM) to distinguish between different logical channels or services multiplexed over a single physical connection. It identifies the specific higher-layer protocol entity (e.g., Call Control, SMS) for which the frame is destined.

Single Cell Notification RNTI

A Radio Network Temporary Identifier used in LTE to notify UEs about changes to the Single Cell Multicast Control Channel (SC-MCCH). It alerts multicast-subscribed devices to check for updated service information, enabling efficient power saving by avoiding constant monitoring.

Single Cell Radio Network Temporary Identifier

A UE-specific identifier used for scheduling and control signaling within a single LTE cell. It enables efficient resource allocation for user equipment, particularly for small data transmissions or specific procedures like random access, without requiring a full C-RNTI.

Session Endpoint Identifier

A unique identifier used in the Packet Forwarding Control Protocol (PFCP) between control plane and user plane functions in the 5G Core. It identifies a specific PFCP session, which corresponds to a user's PDU Session or a specific traffic forwarding context, enabling association of control messages with the correct user plane state.

Short File Identifier

A 2-byte identifier used within a UICC or Smart Card to uniquely reference an Elementary File (EF). It provides an efficient, compact addressing mechanism for applications like USIM to access stored data (e.g., phonebook, network settings).

System Information Radio Network Temporary Identifier

A specific RNTI used in LTE and NR to scramble and identify the PDCCH transmissions that schedule the System Information Blocks (SIBs). It ensures that all UEs in a cell can correctly receive and decode the essential broadcast system information required for initial access and cell operation.

SIP Uniform Resource Identifier

A SIP-URI is a standardized address format, based on the generic URI syntax, used to identify a communication resource within a SIP-based network, such as the IMS. It uniquely identifies a user, service, or application for the purpose of initiating multimedia sessions like voice or video calls.

Sidelink Configured Scheduling Radio Network Temporary Identifier

A unique identifier used in NR sidelink for configured grant transmissions, enabling semi-persistent scheduling of sidelink resources without dynamic grants. It allows efficient periodic transmission patterns for predictable traffic like V2X safety messages while reducing control signaling overhead.

Sidelink Positioning Reference Signal Configured Scheduling Radio Network Temporary Identifier

A unique identifier assigned to a UE for receiving configured scheduling grants for Sidelink Positioning Reference Signal (SL-PRS) transmissions. It enables efficient, scheduled resource allocation for positioning signals in sidelink communications, crucial for V2X and device-to-device positioning.

Sidelink Radio Network Temporary Identifier

A temporary identifier assigned by the network to a UE for sidelink communication. It is used for scheduling and addressing in the physical layer, enabling direct device-to-device data transmission without routing through the base station.

Sidelink V2X Radio Network Temporary Identifier

SL-V-RNTI is a temporary identifier assigned by the network to a UE for scheduling and controlling sidelink V2X transmissions. It is used in downlink control information to indicate resources for sidelink communication, enabling efficient resource allocation for vehicle-to-everything services.

Serving Network Identifier

The Serving Network Identifier (SN) is a critical network identifier used in 3GPP systems to uniquely identify the serving network a User Equipment (UE) is attached to. It is essential for security procedures, mobility management, and service continuity, ensuring the network can correctly route signaling and user data.

Shared Network Area Code

An identifier used in UMTS to uniquely define a shared network area within a PLMN. It enables operators to share network infrastructure while maintaining separate core networks and subscriber management. This is crucial for network sharing agreements and efficient resource utilization.

Serving Network Name

A network identifier used in 5G systems to uniquely name the serving network. It is a key parameter in authentication and security procedures, derived from the Public Land Mobile Network (PLMN) ID and potentially a Network Identifier (NID) for non-public networks.

SCCP Network Resource Identifier

SNRI is a unique identifier used within the SCCP (Signalling Connection Control Part) layer to distinguish different network resources, such as specific applications or subsystems. It is crucial for routing signalling messages correctly in legacy circuit-switched and early packet-switched core networks, ensuring reliable service delivery.

Service Provider Identification

A unique identifier used in 3GPP systems to distinguish the entity that provides a service to an end-user, such as an MNO, MVNO, or service aggregator. It is crucial for service differentiation, billing, policy enforcement, and roaming agreements. The SPI allows networks to apply specific rules based on the service provider, not just the subscriber.

Secure Real-time Transport Protocol Master Key Identifier

The SRTP Master Key Identifier is a unique label used to associate encrypted SRTP media packets with their specific SRTP Master Key. It enables efficient key management and rollover during a session, allowing receivers to select the correct key for decryption without explicit out-of-band signaling for each packet.

Service Set Identifier

A unique identifier that names a wireless local area network (WLAN). It is broadcast by Wi-Fi access points to allow client devices to discover and select a network. In 3GPP, it is crucial for interworking with non-3GPP access networks like Wi-Fi, enabling seamless authentication and mobility.

Sub-System Number

SSN is a numeric identifier used in SS7/SIGTRAN signaling to uniquely identify a specific application or function within a network node. It is a key field in the Signaling Connection Control Part (SCCP) and is essential for routing messages to the correct internal subsystem, such as the HLR, MSC, or SMSC.

Subscription Permanent Identifier

Subscription Permanent Identifier (SUPI) is a globally unique, permanent identifier for a 3GPP subscription in 5G systems. It serves as the fundamental subscription identity, used for authentication and subscription management, and is typically concealed in transit for privacy using the SUCI.

ID Space Vehicle Identification

SV (ID Space Vehicle Identification) is a unique identifier for satellites in satellite-based positioning systems like GPS, GLONASS, Galileo, and BeiDou, integrated into 3GPP standards. It is used by User Equipment (UE) to measure and report signals from specific satellites for location services. This identifier is fundamental for Assisted GNSS (A-GNSS) and other positioning methods in mobile networks.

SVN Medium Access Control label

A label used within the Satellite Virtual Network (SVN) architecture to identify and manage Medium Access Control (MAC) layer resources or contexts for satellite connections. It assists in routing and session management for UEs accessing the network via satellite.

Terminating User Equipment

T-UE refers to the User Equipment (UE) that is the recipient or terminating endpoint of a communication session, such as a called party in a voice call or the destination for data. It is a key concept in session management and routing, distinguishing the receiving device from the originating UE (O-UE). This identification is essential for establishing and managing connections in the network.

Terminating User Equipment

T-UE refers to the User Equipment that is the destination or terminating point of a communication session, such as the called party in a voice call or the receiver in a data session. It is a key concept in 3GPP signaling and session management, distinguishing it from the Originating UE (O-UE). This distinction is vital for routing, service delivery, and applying subscriber-specific policies.

Tracking Area Identifier

A unique identifier for a Tracking Area (TA) in 3GPP networks, used for UE location management and paging. It enables efficient mobility by grouping cells, reducing signaling overhead during idle mode mobility. It is fundamental for network attach, registration, and handover procedures.

Terminal End-point Identifier

A unique identifier used in the 3GPP TS 52.021 specification for the Terminal Adaptation Function (TAF). It distinguishes individual end-points within the terminal, enabling proper data routing and management between the mobile terminal and the network's interworking functions.

Tunnel End Point Identifier

A critical identifier used in GPRS, EPS, and 5GS to uniquely label GTP tunnels between network nodes. It enables the routing of user data and control messages through the core network by identifying the tunnel endpoints at the GTP layer, ensuring packets are delivered to the correct session and processing entity.

Tunnel Endpoint Identifier, control plane

A specific type of TEID used exclusively within the GTP-Control (GTP-C) protocol. It identifies the endpoints of signaling tunnels between control plane network functions (like MME, SGW, PGW in 4G), enabling the reliable exchange of session management and mobility signaling messages.

Tunnel Endpoint Identifier, user plane

A unique identifier for user plane GTP tunnels between network nodes (e.g., SGW and eNB/PGW). It enables multiplexing of multiple user data flows within a single transport layer connection, ensuring correct packet routing and session management in the core network.

Telephone Uniform Resource Locator

A URI scheme for identifying telephone numbers, standardized as 'tel:' in 3GPP. It provides a uniform way to encode and address telephone numbers within network protocols and services, enabling consistent call routing and service invocation across different systems.

Terminal Identification

Terminal Identification (TID) is a standardized identifier for a user terminal or mobile station, as defined in CCITT Recommendation F.200. In 3GPP systems, it is used within protocols like GTP to uniquely identify a terminal's context for mobility management and data session handling, particularly for inter-system operations.

Temporary Logical Link Identifier

A temporary identifier used in GSM and GPRS networks to uniquely address a Mobile Station (MS) at the logical link control (LLC) layer. It is assigned by the network during GPRS attach or routing area update procedures and is used for all data transfer and signaling between the MS and the Serving GPRS Support Node (SGSN). It ensures efficient multiplexing of data flows over the radio interface.

T8 Long Term Transaction Reference ID

A unique identifier used within the T8 reference point to correlate and manage long-duration transactions or sessions between the Service Capability Exposure Function (SCEF) and external Application Servers (AS) for IoT services. It provides a stable reference for monitoring events, device triggers, or non-IP data delivery sessions that may persist for extended periods, such as days or weeks.

Temporary Multicast Group Identifier

The Temporary Multicast Group Identifier (TMGI) is a unique identifier used in 3GPP networks to identify a specific Multimedia Broadcast Multicast Service (MBMS) session. It enables user equipment to discover, join, and receive multicast/broadcast content, such as live TV or software updates, over cellular networks.

Temporary Mobile Subscriber Identifier

A temporary, randomly assigned identifier that replaces the permanent International Mobile Subscriber Identity (IMSI) for identifying a UE on the radio interface. It enhances subscriber privacy and security by preventing tracking and eavesdropping.

Type Of Number

TON is a parameter in telecommunication signaling that categorizes the format of a dialed or called number, such as international, national, or subscriber number. It is crucial for proper call routing and number analysis in circuit-switched and IP Multimedia Subsystem (IMS) networks, ensuring calls reach the correct destination.

Transmit Power Control Radio Network Temporary Identifier

A specific RNTI used in LTE to address and identify UEs for the purpose of transmitting Transmit Power Control commands via the PDCCH. It enables network-directed power control for uplink transmissions, helping to manage interference and optimize UE battery life in shared channel scenarios.

Transport Session Identifier

A unique identifier for a transport session, such as a Multimedia Broadcast/Multicast Service (MBMS) bearer, within a 3GPP network. It is crucial for the network to correctly route and manage data flows for point-to-multipoint services, ensuring content reaches the intended group of users efficiently.

UTRAN Radio Network Temporary Identifier

A temporary identifier assigned by the UTRAN to uniquely identify a User Equipment (UE) within the radio access network context, specifically for communication between the UE and the Radio Network Controller (RNC). It is crucial for signaling during active connections, including handovers and cell updates.

UTRAN Cell Identifier

A unique identifier for a cell within a UTRAN (UMTS Terrestrial Radio Access Network). It is crucial for cell management, handover procedures, and network planning, allowing the network to distinguish between different radio cells for operational and maintenance purposes.

Uniform Resource Name

A Uniform Resource Name (URN) is a persistent, location-independent identifier used within 3GPP systems to uniquely name resources like services, users, or network elements. It follows the IETF RFC 2141 syntax (urn:namespace:identifier) and is crucial for service discovery, addressing, and routing in IMS and other IP-based services. It provides a stable identity even if the resource's location or access method changes.

Universally Unique IDentifier

A UUID is a standardized 128-bit identifier used within 3GPP systems to uniquely name resources, services, or entities without requiring centralized coordination. It is crucial for network slicing, service-based architectures, and IoT, enabling unambiguous identification across distributed systems and administrative domains.

VCC Domain Transfer Number

A telephone number or identifier used within the Voice Call Continuity (VCC) framework to facilitate the transfer of an active voice call between the circuit-switched (CS) domain and the IP Multimedia Subsystem (IMS) domain. It acts as a routing anchor for the network during the domain transfer procedure.

Vehicle Identity Number

A globally unique, standardized 17-character identifier for individual motor vehicles, defined by ISO 3779. In 3GPP contexts, it's used for vehicle identification in telematics and V2X services, enabling secure and unambiguous vehicle recognition for network-based applications.

WLAN Link Layer ID

WLLID is a unique identifier for a WLAN link layer connection, standardized in 3GPP for integrated network scenarios. It enables the network to distinguish and manage individual WLAN links, particularly for traffic steering and aggregation with cellular networks. This matters for seamless mobility and efficient resource utilization in converged 3GPP-WLAN networks.

WLAN Specific Identifier

A unique identifier used within 3GPP systems to manage and authenticate a user's subscription for access to Wireless Local Area Networks (WLANs). It is crucial for enabling secure, seamless interworking between cellular and Wi-Fi networks, supporting features like authentication and service continuity.

XCAP Unique Identifier

A unique identifier used within the XCAP protocol to address specific XML documents or nodes stored on an XCAP server. It enables clients to manage service-specific configuration data, such as presence authorization rules or communication service settings, in a standardized and interoperable manner.

Zone Code

A geographical identifier used in 3GPP networks to define a specific zone for location-based services and network management. It enables the network to apply policies, routing, or services based on a user's zone, supporting features like location-aware charging and emergency services.