3GPP Glossary

3rd Generation Mobile Switching Centre

The 3G-MSC is the central switching node for circuit-switched voice and data services in 3G UMTS networks. It manages call control, mobility management, and interconnection with other networks like PSTN. It was crucial for transitioning from 2G to 3G services, supporting higher data rates and new multimedia capabilities.

3rd Generation Serving GPRS Support Node

The 3G-SGSN is a core network element in 3GPP UMTS networks responsible for managing packet data sessions for mobile devices. It handles mobility management, session management, and user authentication for 3G packet-switched services, acting as the primary interface between the Radio Access Network and the core packet network. It was essential for enabling high-speed mobile internet and data services in 3G networks.

5G Core Network

The 5G Core network is the central brain of 5G systems, built on a cloud-native, service-based architecture. It provides enhanced mobile broadband, ultra-reliable low-latency communication, and massive machine-type communication. Its design enables network slicing, edge computing, and flexible service delivery.

5G Core Network

The 5G Core Network (5GCN) is the central brain of 5G systems, defined from 3GPP Release 15 onward. It provides the control and user plane functions for connectivity, mobility, and policy management. Its cloud-native, service-based architecture is crucial for enabling enhanced mobile broadband, ultra-reliable low-latency communications, and massive IoT.

5G System

The 5G System (5GS) is the complete 3GPP-defined architecture for 5G networks, encompassing the 5G Core Network (5GC) and the Next Generation Radio Access Network (NG-RAN). It provides a service-based, cloud-native framework enabling enhanced mobile broadband, massive IoT, and ultra-reliable low-latency communications. Its introduction marked a fundamental shift from previous generations by decoupling hardware and software and leveraging network virtualization.

Access Signalling Gateway

The Access Signalling Gateway (A-SGW) is a core network element introduced in 3GPP Release 4. It acts as a signalling relay and interworking function between the Radio Access Network (RAN) and the core network, specifically for circuit-switched (CS) services. Its primary role is to facilitate the transport of signalling messages, such as those for call control and mobility management, over IP-based transport networks, enabling a more flexible and efficient network architecture.

Access Domain Selection

Access Domain Selection (ADS) is a 3GPP mechanism that enables the network to select the most appropriate access domain (circuit-switched or packet-switched) for voice and messaging services. It ensures optimal service delivery based on UE capabilities, network conditions, and service requirements. ADS is fundamental for enabling Voice over LTE (VoLTE) and ensuring backward compatibility with legacy networks.

Access Gateway Control Function

The Access Gateway Control Function (AGCF) is a core network element in the IP Multimedia Subsystem (IMS) that provides control and interworking functions for legacy non-IMS access networks, such as PSTN/ISDN and analog lines. It enables the migration of traditional telephony services to the all-IP IMS architecture by acting as a gateway controller, translating between legacy signaling protocols (e.g., H.248) and IMS-specific SIP signaling. This is crucial for service continuity and the phased evolution of networks towards unified IP-based communication.

Access Gateway Function

The Access Gateway Function (AGF) is a 5G core network component that provides fixed network access. It interconnects customer premises equipment (CPE) over fixed broadband to the 5G core, enabling converged fixed-mobile services. This is crucial for delivering 5G services over non-3GPP access technologies.

Access Gateway

The Access Gateway (AGW) is a functional entity in 3GPP networks that provides connectivity and session management for user equipment. It acts as a gateway between the access network and the core network, handling data forwarding, policy enforcement, and mobility management. Its role is crucial for enabling efficient data routing and service delivery across different access technologies.

All-IP Network

AIPN is a 3GPP architectural framework where all network services—voice, data, and signaling—are delivered over IP-based transport. It replaces legacy circuit-switched networks with a unified packet-switched infrastructure, enabling cost efficiency, service convergence, and support for multimedia applications. This transition is fundamental to modern mobile broadband evolution.

Access and Mobility Management

AM is a core network function responsible for managing user equipment access to the network and handling mobility procedures. It authenticates users, authorizes network access, and manages location tracking and handovers between cells. This function is essential for maintaining seamless connectivity as users move through the network.

Access and Mobility Management Function

The AMF is a core network function in 5G that handles registration, connection, reachability, and mobility management for user equipment. It acts as the primary termination point for NAS signaling and is decoupled from session management, enabling flexible network architectures.

Access Network Discovery and Selection

ANDS is a 3GPP mechanism enabling devices to discover and select appropriate access networks based on operator policies and user preferences. It provides intelligent network selection beyond simple signal strength, supporting multi-access connectivity scenarios. This is crucial for seamless service continuity and efficient network resource utilization in 5G and beyond networks.

Access Point Name

The Access Point Name (APN) is a network identifier used by a mobile device to connect to a specific packet data network (PDN), such as the internet or a private corporate network. It determines the gateway (GGSN/PGW) and the IP address allocation method, enabling differentiated services and billing. APNs are fundamental for routing user traffic and applying policy control.

Access Transfer Control Function

The Access Transfer Control Function (ATCF) is a 3GPP network element that manages seamless access transfer during voice call continuity between different access networks. It serves as an anchor point in the IMS network, enabling smooth handovers between circuit-switched and packet-switched domains while maintaining call quality and session continuity.

Access Transfer Gateway

The Access Transfer Gateway (ATGW) is a user plane function in 3GPP networks that facilitates seamless service continuity during access network changes. It anchors user plane traffic, enabling efficient handovers between 3GPP and non-3GPP access technologies (like Wi-Fi) without interrupting active sessions. This is crucial for delivering consistent multimedia services like IMS-based voice and video across heterogeneous networks.

Bearer Level Application-Level Gateway

A network function that performs deep packet inspection and application-aware policy enforcement at the bearer level. It enables service providers to implement sophisticated charging, traffic optimization, and QoS policies based on application-layer information within the IP Multimedia Subsystem (IMS).

Backbone Bearer

A logical transport connection between network elements in the 3GPP architecture that carries user data and control signaling. It provides reliable, QoS-aware transport for traffic between core network nodes, enabling efficient data routing and network scalability across different domains and interfaces.

Bearer Binding and Event Reporting Function

BBERF is a logical function in the Evolved Packet Core (EPC) that binds service data flows to bearers and reports events to the Policy and Charging Rules Function (PCRF). It enables dynamic QoS control and policy enforcement in non-3GPP access networks, ensuring consistent service quality across heterogeneous networks.

Backward Call Indicators

BCI is a set of information elements in 3GPP signaling protocols that convey call-related parameters from the terminating side back to the originating side during call setup. It enables proper call handling, service continuity, and interworking between different network generations by providing critical information about the called party's capabilities and network conditions.

Bearer Control Mode

Bearer Control Mode (BCM) is a network-controlled mechanism for establishing and managing Packet Data Protocol (PDP) contexts or Packet Data Network (PDN) connections in 3GPP systems. It determines whether the UE or the network initiates bearer resource modification procedures, centralizing QoS control for optimized resource allocation and policy enforcement.

Basic Call State Model

The Basic Call State Model (BCSM) is a finite state machine model defined by 3GPP that describes the processing stages of a call or session in the core network. It is fundamental to the Intelligent Network (IN) architecture, enabling service logic execution at specific detection points. This model allows for the creation of supplementary services like call forwarding, prepaid billing, and number translation by providing a standardized view of call processing events.

Bearer Control Unit

The Bearer Control Unit is a functional entity in the 3GPP architecture responsible for managing and controlling bearer resources between the core network and external packet data networks. It handles bearer establishment, modification, and teardown procedures, ensuring proper QoS and policy enforcement for user data flows. This component is crucial for maintaining service quality and efficient resource utilization in mobile networks.

Border Gateway

The Border Gateway (BG) is a functional entity in GPRS/UMTS networks that provides interworking and security between a GPRS backbone and external packet data networks (PDNs). It acts as a gateway, handling IP routing, address translation, and firewall functions to enable secure mobile data services.

Breakout Gateway Control Function

The BGCF is a call session control function in the IMS that selects the appropriate network for routing SIP sessions to the PSTN or CS domain. It determines whether breakout should occur in the same network or a different one, and selects the MGCF or another BGCF accordingly. This is critical for interworking between IMS and legacy telephony networks.

Border Gateway Function

The Border Gateway Function (BGF) is a session border controller within the IP Multimedia Subsystem (IMS) that manages media traffic at network boundaries. It provides policy enforcement, NAT traversal, and security functions for multimedia sessions, ensuring quality of service and network protection. BGF is essential for interconnecting different operator networks and enabling secure, reliable multimedia services.

Bearer Independent Core Network

BICN is a 3GPP architectural concept that decouples the core network from specific underlying transport technologies, enabling a unified core to support multiple access networks like GSM, UMTS, and LTE. It allows for more flexible and efficient network evolution by separating control and user plane functions. This matters because it simplifies network management, reduces costs, and facilitates the transition to all-IP networks.

Broadcast Multicast Interworking Function

The Broadcast Multicast Interworking Function (BM-IWF) is a core network element that enables efficient delivery of broadcast and multicast services in UMTS networks. It acts as an interface between the broadcast/multicast service center (BM-SC) and the UMTS Terrestrial Radio Access Network (UTRAN), facilitating content distribution to multiple users simultaneously. This component is essential for optimizing network resources when delivering the same content to many subscribers, such as mobile TV or software updates.

Broadcast Message Gateway

The Broadcast Message Gateway (BMG) is a 5G core network function introduced in 3GPP Release 18. It facilitates the delivery of broadcast and multicast messages, such as public warnings or group communications, to a large number of User Equipments (UEs) efficiently. It acts as a gateway between application servers and the 5G network, enabling scalable, network-controlled distribution of information.

Broadband Network Gateway

The Broadband Network Gateway (BNG) is a network element that aggregates subscriber traffic from broadband access networks and provides IP connectivity to the core network. It serves as the gateway between access networks (like DSL, fiber, or cable) and the service provider's IP/MPLS core, handling subscriber management, policy enforcement, and quality of service. BNG is crucial for enabling scalable broadband services with differentiated service levels and secure subscriber access.

Broadband Policy Control Function

The Broadband Policy Control Function (BPCF) is a policy control entity in 3GPP networks that enables the application of 3GPP policy and charging control (PCC) rules to non-3GPP access networks, such as fixed broadband. It acts as a policy proxy, translating between 3GPP and non-3GPP policy domains, allowing for unified QoS and charging control across heterogeneous access technologies. This is crucial for converged network operators offering services over both mobile and fixed networks.

Broadband Remote Access Server

The Broadband Remote Access Server (BRAS), also known as a Broadband Network Gateway (BNG), is a network element that aggregates subscriber sessions from broadband access networks. It functions as the gateway between the access network and the core IP network, providing authentication, authorization, accounting (AAA), IP address management, and policy enforcement. It is critical for managing subscriber traffic, enforcing Quality of Service (QoS), and enabling service differentiation in fixed and converged broadband networks.

Composition Capable Network

A network architecture that enables dynamic composition of network functions and services from multiple providers. It allows operators to create customized network slices by combining resources and capabilities across administrative domains, supporting flexible service delivery and resource optimization in multi-vendor environments.

Charging Function

The Charging Function (CHF) is a core network component in 5G systems responsible for generating and managing charging data records (CDRs) for network usage. It enables operators to implement flexible, converged charging models for voice, data, and network slice services. Its separation from session management is crucial for supporting diverse 5G business models and real-time charging.

Connectivity session Location and repository Function

The CLF is a network function in the IP Multimedia Subsystem (IMS) that stores and provides location information for user equipment during connectivity sessions. It enables efficient session routing and service delivery by maintaining real-time knowledge of user connectivity points across different access networks.

Core Network

The Core Network (CN) is the central, non-radio part of a 3GPP mobile network, responsible for authentication, session management, mobility, and interconnection with external networks like the internet. It provides the intelligence and control functions, enabling user services and ensuring secure, reliable connectivity across different access technologies.

Control Plane

The Control Plane (CP) is the network layer responsible for signaling, session management, mobility, and policy control. It handles the establishment, maintenance, and teardown of connections, separating signaling from user data traffic. This functional split is fundamental to modern mobile network architecture for scalability and efficient resource management.

Charging Rules Function

The Charging Rules Function (CRF) is a core network element responsible for authorizing and providing charging rules to the Policy and Charging Enforcement Function (PCEP). It determines how user sessions should be charged based on subscriber profiles, service usage, and network policies, enabling flexible and dynamic charging models in 3GPP networks.

Circuit Switched

Circuit Switched (CS) is a traditional telecommunication method that establishes a dedicated physical circuit for the entire duration of a call. It is the foundation for legacy voice and data services in 2G and 3G networks, providing guaranteed bandwidth and low latency. Its significance lies in enabling reliable, real-time communication services like speech, fax, and data calls before the widespread adoption of packet-switched technologies.

Circuit Switched Gateway

The Circuit Switched Gateway is a network element that provides interworking between the 3GPP circuit-switched domain and external circuit-switched networks. It enables voice and legacy circuit-switched services to continue operating while networks transition to packet-switched architectures. This gateway is essential for maintaining backward compatibility and service continuity during network evolution.

Circuit Switched domain - Interconnection Border Control Function

The CS-IBCF is a functional entity within the IP Multimedia Subsystem (IMS) that provides the border control function for interconnection between the IMS network and external circuit-switched (CS) networks, such as legacy PSTN/PLMN. It handles protocol interworking, topology hiding, and security at the CS domain boundary, enabling seamless voice and other CS-domain service interworking with IMS. It is crucial for ensuring secure, controlled, and efficient interconnection between IMS-based networks and traditional telephony networks.

Circuit Switched Media Gateway

The CS-MGW is a network element that performs media conversion and transcoding between circuit-switched (CS) networks (like PSTN/ISDN) and packet-switched (PS) networks (like IP in 3GPP). It enables voice and circuit-switched data services over IP transport, facilitating network convergence and efficient resource utilization.

CS Adaptation Function

The CS Adaptation Function (CSAF) is a functional entity introduced in 3GPP Release 7 to enable the delivery of Circuit-Switched (CS) domain services over IP-based transport networks, specifically for the IP Multimedia Subsystem (IMS). It acts as a critical bridge, adapting traditional CS signaling and bearer traffic for transport over the packet-switched (PS) domain, facilitating the evolution towards all-IP networks while maintaining backward compatibility with legacy CS services like voice calls.

Call Session Control Function

The CSCF is a core IMS (IP Multimedia Subsystem) node responsible for SIP session control, user authentication, and routing. It manages multimedia service delivery, enabling voice, video, and messaging over IP. Its roles include Proxy, Serving, and Interrogating functions for efficient session handling.

Circuit Switched Public Data Network

A public data network using circuit-switched technology for dedicated connection paths between endpoints. It provides reliable, constant-bit-rate data transmission for applications requiring guaranteed bandwidth and low latency, serving as a foundational network architecture before packet-switched dominance.

Circuit Switched Routing Number

A temporary identifier assigned to a mobile subscriber during circuit-switched fallback (CSFB) procedures when operating in LTE/EPC networks. It enables routing of circuit-switched voice calls through legacy 2G/3G networks while the user equipment remains camped on LTE for data services, maintaining backward compatibility during network transition periods.

Connection Termination Point

A Connection Termination Point (CTP) is a logical endpoint within the UMTS Core Network that represents the termination of a transport connection used for Operation and Maintenance (O&M) traffic. It is a fundamental concept in the Transport Network Layer (TNL) for managing the flow of control and management data between network elements, enabling reliable O&M communication.

Downlink Attach

D-ATT is a procedure in GSM/UMTS networks where the network initiates a connection to a mobile device in the downlink direction. It is a core mechanism for enabling mobile-terminated services like voice calls and SMS delivery. This process is fundamental for network-initiated communication and subscriber reachability.

Data Channel Server Control Function

A control plane function within the 5G Core Network's Data Channel Server architecture. It is responsible for managing and controlling the establishment, modification, and release of data channels for application-specific communication, particularly supporting advanced services like XR and interactive media.

Downlink Data Delivery

Downlink Data Delivery (DDD) is a 3GPP mechanism that enables efficient delivery of downlink data to User Equipment (UE) in power-saving states, particularly when the UE is in RRC_INACTIVE or RRC_IDLE states. It optimizes network resource usage by reducing signaling overhead and latency for downlink traffic, which is crucial for applications with intermittent data transfers. This mechanism is especially important for IoT devices and applications requiring energy efficiency while maintaining reachability.

Downlink Data Delivery Status

DDDS is a 5G Core Network mechanism that provides notification about the delivery status of downlink data when buffering occurs at the UPF. It enables efficient power saving for UEs by allowing them to enter idle mode while the network buffers data and notifies them when delivery is needed. This is crucial for optimizing UE battery life and network resource utilization.

Downlink Data Notification

Downlink Data Notification (DDN) is a signaling message used by the Serving Gateway (SGW) to inform the MME/SGSN that downlink data has arrived for a UE in ECM-IDLE or PMM-IDLE state. It triggers the network-initiated service request procedure to re-establish user plane bearers and page the UE. This mechanism is fundamental for enabling efficient power saving in UEs while ensuring timely data delivery.

Delivery Function 2

DF2 is a functional entity in the 3GPP Short Message Service (SMS) architecture, specifically defined for SMS over GSM networks. It acts as an intermediary that receives and forwards SMS messages between the Short Message Service Centre (SM-SC) and the Mobile Switching Centre (MSC). Its primary role is to ensure reliable message delivery and interworking within legacy GSM SMS systems.

Delivery Function 2 for GPRS

DF2P is a core network function in GPRS that handles the delivery of mobile-terminated point-to-point (MT-PP) short messages. It interfaces with the Short Message Service Center (SMSC) to ensure reliable message delivery to mobile stations, even when they are temporarily unreachable, by managing delivery attempts and status reporting.

Delivery Function 3 for GPRS

DF3P is a GPRS network function responsible for delivering short messages to mobile devices via the packet-switched domain. It enables SMS delivery over GPRS connections, providing an alternative to circuit-switched SMS delivery. This function is crucial for maintaining SMS service continuity as networks evolve toward packet-based architectures.

Destination Local Exchange

A core network element in circuit-switched (CS) telephony that routes calls to their final destination within a local network area. It is a key component in traditional GSM/UMTS call routing, handling the final leg of a call's path to the subscriber.

Delegated Mobile Network Prefix

A network prefix delegated by a mobile network operator to another entity, such as a vehicle or IoT gateway, allowing it to act as a mobile router. It enables local IP address assignment and network mobility for connected devices without requiring individual subscriptions, supporting scenarios like vehicular networks and localized IoT deployments.

Data Network Authentication, Authorization and Accounting

A functional entity within the 5G Core Network that provides Authentication, Authorization, and Accounting services specifically for a user's connection to an external Data Network (DN). It enables the DN operator to control and track access independently from the 3GPP network operator's AAA functions.

Data Network Access Identifier

An identifier for a user plane access point to a specific Data Network (DN) or a localized service within it. It is used by applications and the 5G Core to optimize traffic routing, enabling low-latency edge computing and efficient service delivery by steering user traffic to the optimal network exit point.

Directory Name Service

DNS is a hierarchical, distributed naming system used within 3GPP networks to translate human-readable domain names into IP addresses and other resource records. It is fundamental for service discovery, network element location, and routing of signaling and user plane traffic across the evolved packet core and between operators.

Donor Public Land Mobile Network

A Public Land Mobile Network (PLMN) that provides core network services and resources to a local network, such as a Home NodeB or small cell, in scenarios like network sharing or femtocell deployments. It enables the local network to operate by leveraging the donor's infrastructure for connectivity and management.

Designated Router

A logical router function within the 5G Core Network's Edge Computing (MEC) architecture. It is responsible for efficient routing of traffic between User Equipment (UE) and local application servers hosted at the network edge.

Diameter Routing Agent

A Diameter Routing Agent (DRA) is a network element that provides routing and proxy functions for Diameter signaling messages in the Evolved Packet Core (EPC) and 5G Core (5GC). It is crucial for scalable and efficient policy, charging, and authentication signaling, enabling network operators to manage complex multi-vendor and roaming scenarios by centralizing routing logic and reducing point-to-point connections.

Data call Routeing Mechanism

A core network mechanism in GSM and UMTS that determines the optimal routing path for a mobile-originated data call (like a circuit-switched data or fax call). It involves interactions between the MSC, HLR, and VLR to select the appropriate interworking function.

Domain Specific Access Restriction

A network-controlled mechanism that restricts a User Equipment's (UE) access to specific services or domains, such as IMS or emergency services, while allowing others. It enables operators to manage network congestion, enforce policies, and ensure critical service availability by selectively barring non-essential access.

Data Switching Exchange

A network element that facilitates data switching and routing between different networks or services. It acts as an exchange point for data traffic, enabling efficient interconnection and management of data flows in telecommunications systems.

Domain Selection Function

A function that selects the appropriate domain (e.g., circuit-switched or packet-switched) for a communication session. It determines whether a service should be delivered over CS or PS networks based on policies, subscriber preferences, and network capabilities.

DSL Gateway

The DSL Gateway (DSL-GW) is a network element that acts as an interface between Digital Subscriber Line (DSL) access networks and the mobile core network, specifically the GPRS core. It enables the integration of fixed DSL broadband access with mobile packet-switched services, facilitating fixed-mobile convergence. It routes user data traffic and handles policy enforcement for subscribers accessing via DSL.

Direct Tunnel Indication

Direct Tunnel Indication (DTI) is a parameter used in the GTP-C protocol to signal the capability and request for establishing a direct user plane tunnel between the Serving Gateway (SGW) and the Packet Data Network Gateway (PGW), bypassing the SGW for user data transfer. This optimizes the data path in the Evolved Packet Core (EPC).

Enhanced Gateway GPRS Support Node

An enhanced version of the GGSN, a core network node in 2G/3G packet-switched networks. It acts as the gateway between the GPRS/UMTS network and external packet data networks like the internet. It manages IP address allocation, routing, and policy enforcement for mobile data sessions.

Enhanced Home Location Register

An enhanced version of the HLR, a central database in 2G/3G mobile networks. It stores and manages permanent subscriber data including identity, service profiles, authentication information, and current location. It is essential for user authentication, call routing, and service provisioning.

Enhanced Serving Mobile Location Centre

A core network entity responsible for determining the geographic location of a UE (User Equipment) in LTE and 5G networks. It manages positioning procedures, calculates location estimates using various methods (e.g., OTDOA, A-GNSS), and delivers this data to authorized clients like emergency services or commercial applications. Its role is critical for regulatory mandates like E911 and for enabling location-based services.

Enhanced Firewall Traversal Function

A network function that facilitates secure and efficient traversal of firewall and NAT boundaries for IP-based communication services. It enables services like IMS voice and video to work reliably across different network domains.

Evolved Packet Core Network

The Evolved Packet Core (EPC) is the core network architecture defined for 4G LTE systems. It is a fully IP-based, flat architecture designed to provide high-speed packet-switched data and voice services. The EPC handles key functions like user authentication, session management, mobility anchoring, and interconnection with external networks, forming the central nervous system for LTE connectivity.

Evolved Packet Data Gateway

The Evolved Packet Data Gateway is a core network element that provides secure IP connectivity between a UE and the EPC over untrusted non-3GPP access networks, such as Wi-Fi. It acts as a termination point for IPsec tunnels, enabling seamless mobility and service continuity between 3GPP and non-3GPP access. This is crucial for offloading traffic and providing ubiquitous connectivity.

Evolved Packet System

The Evolved Packet System (EPS) is the 3GPP standardized architecture for 4G LTE networks, encompassing the radio access (E-UTRAN) and the packet core (EPC). It provides all-IP connectivity for high-speed mobile broadband, supporting voice, data, and messaging over a simplified, flat architecture. It is the foundation for LTE services.

Extended TFT Support Network

A network capability that allows a User Equipment (UE) to establish multiple Packet Data Protocol (PDP) contexts or Packet Data Unit (PDU) Sessions associated with a single IP address, each with its own Traffic Flow Template (TFT). It enables sophisticated QoS management and service differentiation for applications running on the same device, such as simultaneous voice, video, and data streams.

Extended Traffic Flow Template Support User Equipment

A UE capability indicating support for an extended set of packet filters in the Traffic Flow Template (TFT). It allows for more complex and granular traffic flow management for IP flows, enabling advanced QoS and policy enforcement in the EPS and 5GS.

Functional Entity

A Functional Entity (FE) is a conceptual building block within 3GPP network architecture, representing a discrete set of functions. It is a logical abstraction used to define capabilities and interfaces without mandating a specific physical implementation. FEs are combined to form network elements and are fundamental to the design, specification, and interoperability of 3GPP systems.

Forward Explicit Congestion Notification

A congestion control mechanism used in Frame Relay networks, standardized by 3GPP for the Gb interface between the BSS and SGSN in 2G/GSM and GPRS networks. It is a bit in the Frame Relay header set by a congested network node to notify the receiving end of congestion in the forward direction.

Firewall Traversal Tunnel to IP network of IMS

A standardized mechanism to securely traverse firewalls and NATs for IMS signaling and media. It enables reliable IMS service delivery across diverse network boundaries, ensuring connectivity for SIP-based services like VoLTE and VoNR in managed and unmanaged IP networks.

Gateway Mobile Switching Centre

A core network element in legacy GSM and UMTS systems that acts as a gateway between the mobile network and external circuit-switched networks, such as PSTN. It handles call routing, mobility management, and interworking functions, enabling voice and SMS services across different network domains.

Generic Access Network Controller

The Generic Access Network Controller (GANC) is a core network element that enables mobile devices to access 3GPP services over unlicensed radio technologies, such as Wi-Fi. It acts as a secure gateway, translating protocols between the access network and the core, facilitating seamless handovers and service continuity. This technology was crucial for early Fixed-Mobile Convergence (FMC) and Wi-Fi calling solutions.

Generic IP access

A standardized mechanism in the IP Multimedia Subsystem (IMS) that allows user equipment to obtain IP connectivity for IMS services via any IP-capable access network, such as WLAN or fixed broadband. It decouples IMS service delivery from the underlying 3GPP packet-switched domain.

Gateway Location Register

The Gateway Location Register (GLR) is a functional node in GSM and UMTS core networks that acts as a temporary visitor location register for roaming subscribers. It is deployed at the border of a network to optimize inter-network signaling by handling mobility management and call routing for inbound roamers locally, without contacting their home HLR for every transaction. This reduces signaling load on international links and improves service setup times.

Gateway Mobile Location Center

A core network node in 3GPP systems that provides location-based services by managing positioning requests. It acts as an interface between external location service clients (LCS clients) and the mobile network, retrieving and delivering the geographic position of user equipment (UE) for applications like emergency calls, navigation, and asset tracking.

Gateway Mobile Services Switching Centre

A core network switch in circuit-switched (CS) mobile networks that acts as the gateway between the mobile network and external fixed or mobile networks (like PSTN). It routes incoming calls to the correct MSC by querying the HLR for subscriber location.

Gateway Mobile Services Switching Centre for the Answering party

The GMSC located in the IPLMN (Interrogating PLMN) of the called party (Answering party) for a Mobile Number Portability (MNP) call. It performs the initial routing interrogation and may also act as the VMSCA if the subscriber is in its own network.

Gateway MSC of the B subscriber

The Gateway MSC (GMSC) that handles the call setup for the terminating (B) subscriber in a mobile network. It is responsible for interrogating the HLR to obtain routing information for the called party and is a critical node for completing mobile-terminated calls.

Gateway MSC in HPLMNC

The Gateway MSC located within the Home Public Land Mobile Network Country (HPLMNC) of a subscriber. It is a specific instance of a GMSCB, emphasizing its geographical and logical placement within the subscriber's home country network for call termination.

GPRS Roaming eXchange

A private, secure IP backbone network interconnecting GPRS/UMTS packet core networks of different mobile operators globally. It enables seamless data roaming by transporting GTP-C and GTP-U traffic between the home and visited networks, ensuring subscribers can access mobile data services while abroad.

GPRS Support Node

A core network node in 2G/3G/4G GPRS and UMTS networks that handles packet data traffic. It refers to either the Serving GPRS Support Node (SGSN) or the Gateway GPRS Support Node (GGSN). These nodes are fundamental for enabling mobile internet and IP-based services.

General Switched Telephone Network

The traditional, circuit-switched public telephone network (PSTN) that provides plain old telephone service (POTS). In 3GPP contexts, it represents the legacy telephony network with which mobile networks must interwork to provide voice call continuity and supplementary services.

GateWay Core Network

A network sharing architecture where multiple Public Land Mobile Networks (PLMNs) share a common core network, including key nodes like the MSC and SGSN. It enables operators to reduce deployment and operational costs while maintaining separate radio access networks and subscriber identities.

Home Application Function

The Application Function located in a user's home network. It interacts with the home policy framework (PCRF/PCF) to request policy and charging control for subscriber services. It is a key element for enabling operator-controlled application services like IMS.

Home Call Session Control Function

The H-CSCF is a core IMS network element that serves as the home network's primary point of contact for SIP signaling. It handles session control, service triggering, and interacts with application servers. It is fundamental for establishing and managing multimedia sessions in the IMS architecture.

Home Diameter Routing Agent

The H-DRA is a Diameter routing node within the home network. It routes Diameter signaling messages (e.g., for authentication, policy, charging) between network functions based on subscriber identity and realm. It is essential for scalable and efficient Diameter-based core network signaling.

Home Policy and Charging Enforcement Function

The Home Policy and Charging Enforcement Function (H-PCEF) is the Policy and Charging Enforcement Function located within a subscriber's Home Public Land Mobile Network (HPLMN). It is a key component of the Policy and Charging Control (PCC) architecture that enforces quality of service (QoS) and charging rules for a subscriber's data sessions, particularly when they are roaming. It applies policies defined by the home operator, ensuring consistent service experience and billing.

Home Policy Control Function

The Home Policy Control Function (H-PCF) is a 5G core network function that manages policy and charging control for roaming subscribers. It resides in the home network (HPLMN) and provides policy decisions to the visited network's PCF, ensuring consistent service quality and charging. It is essential for enabling seamless roaming and enforcing home operator policies across network boundaries.

Home Policy and Charging Rules Function

The Home Policy and Charging Rules Function (H-PCRF) is a 4G/LTE core network element that determines policy and charging rules for roaming subscribers. Located in the home network, it communicates with the visited PCRF to enforce QoS, gating, and charging policies. It is fundamental for enabling policy control in inter-operator roaming environments.

Home Session Management Function

A Session Management Function located in a user's Home Public Land Mobile Network (HPLMN). It is responsible for managing PDU Sessions for roaming UEs when Local Breakout (LBO) is not used, ensuring home network control over session policies, charging, and interaction with the home data network.

Home Unified Data Repository

A Unified Data Repository (UDR) function located in a user's Home Public Land Mobile Network (HPLMN). It stores and manages subscription, policy, and application data that is considered 'home' data, such as user profiles, service-specific settings, and structured data for exposure.

Home Gateway Mobile Location Centre

The Home Gateway Mobile Location Centre (HGMLC) is a core network node responsible for location services in a subscriber's home network. It acts as the primary interface for external location-based service applications, handling authorization, privacy, and routing of location requests. Its role is critical for enabling lawful intercept, emergency services, and commercial location-based applications.

Home Location Register

A central database in 2G (GSM) and 3G (UMTS) circuit-switched networks that stores permanent subscriber data and location information. It is a critical component for mobility management, authentication, and call routing, enabling subscribers to roam while maintaining service.

Home Location Register of the B subscriber

The HLRB is the Home Location Register (HLR) that stores subscription data and location information for the 'B subscriber' in a call. This is a key network entity in GSM/UMTS circuit-switched networks for routing calls and managing services. It is essential for subscriber authentication, call delivery, and supplementary service provisioning.

Home Location Register of the C subscriber

The HLRC is the Home Location Register (HLR) that manages subscription data for the 'C subscriber' in a call forwarding or multi-party call scenario. It is a logical entity defined for specific supplementary services where a third party's subscription data is required. It enables advanced call handling features like Call Transfer and Multi-Party calls.

Home Network

The Home Network is the mobile network operator's core infrastructure where a subscriber's permanent subscription data is maintained. It is responsible for authentication, authorization, and billing for its subscribers, regardless of their location. It is a fundamental concept for roaming and service delivery.

Home Node B Gateway

The Home Node B Gateway is a network element that aggregates and secures connectivity from many Home Node Bs (femtocells) over the public internet. It presents a standard Iu interface to the core network, hiding the femtocell deployment's complexity. It handles security, mobility, and concentration of traffic.

Home Routed with Session Breakout in VPLMN

A 5G roaming architecture where the user plane connection is anchored in the home network (HPLMN) but can be locally broken out in the visited network (VPLMN) for specific data services. This optimizes routing for low-latency applications and local content access while maintaining home network control for the core session.

HRPD Serving Gateway

A core network gateway defined for interworking between 3GPP (E-UTRAN/UTRAN/GERAN) and 3GPP2 CDMA2000 HRPD (High Rate Packet Data) networks. It acts as the mobility anchor and user plane gateway for terminals moving between these heterogeneous radio technologies.

HRPD Serving Gateway

The HSGW is a core network gateway in 3GPP EPS for interworking with 3GPP2 CDMA2000 HRPD networks. It acts as an anchor point for mobility and provides connectivity between the eHRPD access network and the Packet Data Network Gateway (PGW).

Home Subscriber Server

The HSS is the central master database for user and subscription information in 3GPP networks. It stores user profiles, performs authentication and authorization, and manages service provisioning and mobility. It is a critical component for network access, security, and enabling services like voice over LTE (VoLTE).

Interconnection-Border Gateway Function

A functional entity within the IP Multimedia Subsystem (IMS) that acts as a border gateway for interconnection between different operator networks or between an IMS network and other IP networks. It controls media flows, provides network address/port translation (NAPT), and enforces security and QoS policies at the network border.

Interrogating-Call Session Control Function

A central query routing node within the IP Multimedia Subsystem (IMS). Its primary role is to identify the correct Serving-CSCF (S-CSCF) for a subscriber during registration and to route incoming session requests (like calls) to that S-CSCF. It acts as the first contact point within a home network for sessions originating from external networks.

Interrogating Call Session Control Function

The I-CSCF is a key functional element within the IMS (IP Multimedia Subsystem) core network. It acts as the initial point of contact for SIP requests entering a home network from other networks, performing network hiding and selecting the appropriate S-CSCF to serve the user. Its role is critical for routing, security, and subscriber management in IMS-based services.

Incoming - Media Gateway Control Function

The I-MGCF is a functional component within the IP Multimedia Subsystem (IMS) that handles incoming call sessions from circuit-switched networks, like PSTN or legacy PLMN. It performs protocol interworking and controls a Media Gateway for media conversion. This enables seamless voice and multimedia communication between traditional and IP-based networks.

Intermediate Session Management Function

The I-SMF is a Session Management Function introduced in 5G Core to enable local breakout and efficient data routing for a UE, particularly in mobility scenarios involving non-3GPP access or edge computing. It acts as an intermediate SMF instance, separate from the anchor SMF (A-SMF), to manage the user plane path locally. This architecture is crucial for supporting low-latency services and optimizing traffic flow in complex network deployments.

Intermediate User Plane Function

The I-UPF is a User Plane Function deployed locally in a 5G network to provide a breakout point for user data traffic, reducing latency and core network load. It is controlled by an Intermediate SMF (I-SMF) and forms part of a multi-hop UPF architecture alongside an Anchor UPF. Its primary role is to route traffic efficiently for edge computing, local network access, and optimized mobility paths.

Interconnection Border Control Functions

The Interconnection Border Control Function (IBCF) is a core network element within the IP Multimedia Subsystem (IMS) that acts as a secure gateway for SIP-based signaling between different operator networks or between an IMS network and non-IMS networks. It provides topology hiding, protocol interworking, and security functions for inter-domain communication.

Incoming Call Gateway

The Incoming Call Gateway (ICGW) is a functional entity in the 3GPP network architecture responsible for handling and routing incoming calls to mobile subscribers. It acts as a gateway between external networks (like PSTN or other PLMNs) and the mobile core network, ensuring call setup and delivery. Its role is crucial for inter-network connectivity and the completion of mobile-terminated calls.

Integrated Digital Network

A foundational network architecture that integrates digital transmission and switching to provide end-to-end digital connectivity for voice and data services. It represents the evolution from analog and hybrid networks to fully digital systems, forming the basis for modern telecommunications.

Intra Domain NAS Node Selector

A functional entity in the core network that selects the appropriate NAS node (e.g., MME, AMF) for a UE within a single network domain. It optimizes routing and load balancing during initial attachment and mobility procedures, enhancing network efficiency and reliability.

Initial Detection Point

A functional entity within the CAMEL (Customised Applications for Mobile network Enhanced Logic) service architecture. It is the first point in the call/state model where a CAMEL service can be invoked, enabling network operators to deploy intelligent, customised services like prepaid charging or call screening.

Incoming Leg Control Model

The Incoming Leg Control Model (ILCM) is a call control model defined in 3GPP for managing the signaling and media handling of the incoming leg of a call or session in the IP Multimedia Subsystem (IMS). It is fundamental to the architecture of IMS-based telephony services.

IP Multimedia Core Network Subsystem

The IP Multimedia Core Network Subsystem (IMS) is a standardized architectural framework for delivering IP multimedia services over mobile and fixed networks. It enables voice, video, messaging, and other multimedia applications using SIP-based signaling, decoupling services from access networks. IMS is fundamental for enabling VoLTE, VoWiFi, RCS, and convergence between telecom and internet services.

Intermediate GSN

An Intermediate GSN (IM-GSN) is a GPRS Support Node that acts as an intermediary for user plane traffic between a GGSN and an SGSN in a roaming scenario. It enables optimized routing and inter-operator charging for GPRS/UMTS packet data services when a user is outside their home network.

IP Multimedia Media Gateway Function

The IM-MGW is a media gateway within the IMS that performs media translation and processing between different network types and codecs. It enables interworking between packet-switched IMS networks and circuit-switched networks (like PSTN/PLMN), and handles media functions like transcoding, echo cancellation, and conferencing for multimedia sessions.

Intermediate Mobile Switching Centre

An Intermediate MSC is a Mobile Switching Centre that relays call control signaling and user traffic between a Gateway MSC (GMSC) and a visited MSC (VMSC) during mobile-terminated call setup. It is used in scenarios where the GMSC cannot route the call directly to the VMSC, often due to network architecture or routing policies. Its role is crucial for ensuring successful call delivery in complex or legacy network interconnections.

IP Multimedia Service Switching Function

The IM-SSF is a core network function that enables the execution of legacy CAMEL (Customized Applications for Mobile network Enhanced Logic) services for subscribers using the IP Multimedia Subsystem (IMS). It acts as a gateway, translating between IMS session control protocols (SIP) and the CAMEL Application Part (CAP) used in circuit-switched and packet-switched domains. This allows operators to reuse existing CAMEL-based intelligent network services, like prepaid or parental control, for IMS-based VoIP and multimedia sessions.

IP Multimedia Core Network

The IP Multimedia Core Network (IMCN) is the architectural framework defined by 3GPP for delivering IP-based multimedia services over mobile networks. It enables services like voice over IP (VoIP), video calling, and instant messaging by providing the core network functions for session control, media handling, and subscriber management. Its introduction marked the shift from circuit-switched to packet-switched multimedia services in mobile networks.

IP Multimedia Subsystem

A standardized architectural framework defined by 3GPP for delivering IP-based multimedia services (voice, video, messaging) over mobile and fixed networks. It provides service control, authentication, and charging functions independent of the underlying access technology.

IMS Access Media Gateway

A media plane function within the IMS architecture that provides media processing, anchoring, and interworking capabilities. It handles media streams for services like voice and video, enabling transcoding, lawful interception, and connectivity to legacy networks under the control of an IMS Media Gateway Control Function.

IMS Application Level Gateway

A network function that facilitates SIP and SDP protocol interworking between IPv4 and IPv6 networks within the IMS. It resolves NAT traversal issues for SIP-based multimedia sessions, ensuring seamless communication across different IP address domains.

IMS Gateway Function

A charging gateway function within the IMS that collects charging information from IMS network elements, performs correlation and formatting, and forwards it to the offline charging system. It is a key component for generating billing records for IMS-based services.

IP Multimedia Subsystem Media Gateway Function

A media gateway that provides conversion between packet-switched IMS media streams (e.g., over RTP/IP) and circuit-switched media formats (e.g., TDM voice). It enables interworking between IMS networks and legacy PSTN/PLMN networks under the control of a Media Gateway Control Function.

Interrogating Network Entity

The INE is a functional entity in CAMEL (Customised Applications for Mobile network Enhanced Logic) that resides in the visited network. It interrogates the subscriber's home network to fetch CAMEL service information, enabling the execution of operator-specific intelligent network services like prepaid charging or call screening while the user is roaming.

IP-Connectivity Access Network

A conceptual network that provides IP connectivity between a User Equipment (UE) and an external IP network, such as the internet or an IMS. It is the foundation for enabling all IP-based services in 3GPP systems, including voice, video, and data. The concept is crucial for policy and charging control (PCC) to manage service quality and billing.

IP Adaptation Function

A functional entity defined in early 3GPP releases for the 3GPP IP Multimedia Subsystem (IMS). It acts as an adaptation layer between circuit-switched control signaling (like ISUP) and the IP-based Session Initiation Protocol (SIP), enabling interworking with legacy telephony networks.

IP Connectivity Access Network

IP Connectivity Access Network (IPCAN) is a conceptual framework in 3GPP that defines the network entities and functions providing IP connectivity between a User Equipment (UE) and an external IP network. It is crucial for establishing and managing the bearer path for IP-based services, enabling QoS control, charging, and policy enforcement across different access technologies.

IP Data Termination

IP Data Termination (IPDT) is a functional element within the 3GPP packet-switched core network that serves as the termination point for IP-based user data traffic. It is responsible for managing the data path, including routing, forwarding, and potentially applying policy and charging rules for user sessions. Its introduction in Release 5 was pivotal for enabling efficient, standardized IP data services over 3G networks.

Interrogating Public Land Mobile Network

The PLMN that contains the Gateway MSC for Short Message Service (GMSC) or the interrogating call session control function (I-CSCF). It is the network that receives an incoming call or message from another network and queries the HLR/HSS to locate the subscriber and route the communication onward.

Integrated Services Digital Network

A set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over traditional telephone circuits. In 3GPP, ISDN is referenced for legacy interworking, as early mobile systems (GSM) were designed to connect to ISDN networks. It matters for understanding the evolution from circuit-switched to packet-switched core networks.

Interworking Media Gateway Function

The Interworking Media Gateway Function is a network element that facilitates media conversion and transport between circuit-switched (CS) networks (like legacy 2G/3G voice) and packet-switched (PS) IP networks (like IMS). It handles voice and video media transcoding, bearer control, and payload processing, enabling seamless service interworking.

Interworking MSC

The Interworking MSC is a functional entity that provides signaling interworking between a 3GPP Circuit Switched core network and an external IP-based network, such as an IMS or a SIP-based trunking network. It translates between ISUP/BICC and SIP protocols to enable call control across domain boundaries.

InterWorking Function

A generic network function that facilitates communication and service interworking between different network domains or technologies. It acts as a protocol translator, gateway, or adapter, enabling seamless operation across heterogeneous systems like 3GPP, fixed networks, or legacy signaling systems. Its role is critical for network convergence and backward compatibility.

InterWorking Mobile Switching Center

A specialized Mobile Switching Center (MSC) that facilitates interworking between different network technologies, such as GSM and CDMA or PSTN. It handles protocol conversion and signaling mediation to enable seamless call routing and service continuity across heterogeneous networks.

Local PDN Gateway

A network function that provides local IP breakout and gateway functionality for user plane traffic, typically deployed close to the radio access network. It enables low-latency services, offloads traffic from the core network, and supports features like Local IP Access (LIPA) and Selected IP Traffic Offload (SIPTO). It is a key enabler for edge computing and 5G scenarios.

Local Network Exposure Function

A localized instance of the Network Exposure Function (NEF) deployed at the network edge. It provides a secure API-based interface for authorized third-party applications to access network capabilities and information (like QoS, location) with low latency. It is a key component for enabling edge application innovation and network-as-a-service.

L2TP Access Concentrator

A network function that terminates L2TP tunnels from user equipment and aggregates their traffic for forwarding into a packet data network (PDN). It acts as the L2TP Network Server's (LNS) counterpart, enabling secure, tunneled access for mobile users, particularly in legacy and interworking scenarios.

Local Gateway

A network function that offloads user plane traffic locally at the network edge, closer to the user. It reduces latency and core network load by handling traffic directly between the Radio Access Network (RAN) and the internet or local services, bypassing the central core network.

Local Mobility Anchor

The Local Mobility Anchor (LMA) is a core network function in the Evolved Packet Core (EPC) defined for Proxy Mobile IPv6 (PMIPv6)-based architectures. It acts as the topological anchor point for a UE's IP address(es), managing mobility within a trusted non-3GPP access network (like Wi-Fi). It routes traffic to the current point of attachment and maintains binding caches.

Location Management Function

A core network function in 5G responsible for managing and coordinating positioning procedures to determine a UE's location. It calculates location estimates, manages positioning sessions, and provides location services to authorized consumers like the GMLC or AF. It is central to 5G's precise location capabilities.

Location Management Server

A core network function defined for the Location Services (LCS) architecture, responsible for managing and providing location-related data and services. It acts as a central repository and processor for subscriber location information, privacy settings, and service authorization, enabling various location-based applications.

L2TP Network Server

A network element that terminates L2TP tunnels from an L2TP Access Concentrator (LAC). It provides the interface between a 3GPP packet core network and an external IP network (e.g., the Internet or a corporate intranet) for user data traffic in early 3GPP architectures.

Multiple Association Control Function

A core network function in the IP Multimedia Subsystem (IMS) that manages multiple simultaneous service associations for a single user. It coordinates SIP sessions, registrations, and subscriptions, enabling complex services like call waiting, call forwarding, and multimedia conferencing.

Mobility Access Gateway

A network entity defined in the Evolved Packet Core (EPC) that manages mobility for non-3GPP access networks, such as Wi-Fi. It acts as a gateway, enabling seamless handovers and secure connectivity between 3GPP and non-3GPP systems, supporting trusted and untrusted access.

MAP Application Terminating Function

A core network function in legacy GSM/UMTS networks that terminates the Mobile Application Part (MAP) protocol. It handles signaling for mobility management and subscriber services, acting as a gateway or endpoint for MAP-based communication between network elements like HLRs and VLRs.

Multicast/Broadcast Session Management Function

A 5G core network function introduced for 5G Multicast-Broadcast Services (5G MBS). It manages the establishment, modification, and release of multicast/broadcast sessions, handling user plane resources and coordinating with other network functions for efficient group data delivery.

Multicast/Broadcast User Plane Function

A 5G Core Network function that handles the user plane for multicast and broadcast services. It efficiently distributes the same content to multiple users, reducing network load and improving spectral efficiency for applications like live video and software updates.

MBMS Gateway

A core network gateway function for MBMS services. It acts as the IP multicast distribution point, forwarding MBMS user data from the BM-SC to the relevant base stations (eNBs/Node Bs) and handling session control signaling towards the RAN.

Multicast/Broadcast Service Function

The Multicast/Broadcast Service Function (MBSF) is a 5G core network function that manages multicast and broadcast service delivery. It handles session establishment, policy control, and data distribution for efficient group communication, enabling applications like live streaming and public safety alerts.

Multi-Connection Mode

An operational mode defined in 3GPP for user equipment to maintain multiple simultaneous connections to different access networks, such as 3GPP and non-3GPP (e.g., Wi-Fi). It enables seamless mobility and traffic aggregation across heterogeneous technologies. MCM is essential for achieving always-best-connected services and enhanced data throughput.

MBMS (Download & Streaming) Delivery Function

The MDF is a core network function in the evolved Multimedia Broadcast Multicast Service (eMBMS) architecture. It is responsible for the delivery, session management, and synchronization of broadcast/multicast content (file download or streaming) from content providers to the radio access network.

Media Gateway

A network element that converts media streams between different transmission formats and protocols, such as between circuit-switched voice (PSTN, 2G/3G CS) and packet-switched voice (VoIP in IMS/4G/5G). It is a key component for interworking legacy and next-generation networks.

Media Gateway Controller

The Media Gateway Controller (MGC) is a core network element in 3GPP's circuit-switched domain. It controls one or more Media Gateways (MGWs) using the H.248/MEGACO protocol, handling call control and signaling for media conversion between circuit-switched and packet-switched networks. It is central to enabling voice services in early 3GPP releases.

Media Gateway Control Function

The Media Gateway Control Function (MGCF) is a critical IMS network element that handles protocol conversion between SIP-based IMS signaling and legacy circuit-switched signaling (e.g., ISUP, BICC). It controls the IMS-Media Gateway (IMS-MGW) for media interworking, enabling voice and video calls between IMS and traditional telephony networks.

Media Gateway Function

A core network function that converts media streams between circuit-switched (e.g., PSTN) and packet-switched (e.g., IP) networks. It is essential for voice and video call interoperability, enabling legacy telephony services to work with modern IP-based networks like IMS and 5G.

Media Gateway

A network element that converts media streams between different transmission formats and protocols, such as between circuit-switched (TDM) and packet-switched (IP) networks. It is essential for enabling voice and multimedia communication across legacy and modern networks, ensuring interoperability and service continuity.

Mobile Location Center

A core network element in 2G, 3G, and 4G mobile networks responsible for providing location-based services (LCS). It calculates the geographical position of mobile devices, manages location requests, and enforces privacy settings for subscribers.

NPC MME Network Product Class

A classification within the 3GPP standards for Mobility Management Entities (MMEs) based on their product capabilities and capacity. It defines performance benchmarks and feature sets, allowing network operators to consistently evaluate and procure MME network functions that meet specific network scale and service requirements.

MME serving the RN

A specific functional role of a Mobility Management Entity (MME) in LTE networks that provides control plane services to a Relay Node (RN). The MME-RN handles the unique authentication, mobility, and session management procedures required for the relay node itself, which acts as a base station for user equipment while being wirelessly connected to the donor eNB.

Multiprotocol Label Switching Architecture

A high-performance packet-forwarding technology that directs data from one network node to the next based on short path labels rather than long network addresses. In 3GPP, it is used as a transport technology within the core network backbone to provide efficient, traffic-engineered, and QoS-aware connectivity between network elements like SGWs, PGWs, and MMEs.

Multimedia Resource Function

A core network element in the IP Multimedia Subsystem (IMS) that provides media-related services such as audio/video mixing, transcoding, tone generation, and playout for multimedia sessions. It is split into a controlling MRFC and a processing MRFP, enabling advanced conferencing and media manipulation.

Multimedia Resource Function Controller

The MRFC is a core network element in the IMS that controls the MRFP to process and manage multimedia resources like conferencing, announcements, and transcoding. It acts as the signaling brain, interpreting SIP commands to orchestrate media plane functions, enabling rich multimedia services.

Multimedia Resource Function Processor

The MRFP is the media plane component of the IMS Media Resource Function (MRF) that physically processes multimedia streams under the control of the MRFC. It handles real-time functions like audio/video mixing, transcoding, tone generation/detection, and media playback, forming the execution engine for multimedia services.

Mobile Services Switching Centre

A second-generation (2G) core network switch that handles circuit-switched voice calls and mobility management in GSM networks. It connects to the Radio Access Network via the A interface and manages call routing, handovers, and subscriber services. It is a foundational element of traditional mobile telephony.

Mobile Switching Centre Server

The control plane element in the 3GPP All-IP network architecture, separating call control and switching functions. It handles signaling for circuit-switched services, working with a Media Gateway (MGW) for bearer transport. This enables more flexible, scalable network evolution.

Mobile Service Transport

MST is a protocol framework defined in 3GPP for transporting mobile service-specific signalling and data over IP-based networks. It provides a standardized mechanism for service layer communication between network elements, such as between an Application Server (AS) and a Service Capability Server (SCS). Its importance lies in enabling reliable, interoperable transport for services like IMS and CAMEL in evolving all-IP core networks.

Message Signalling Unit

MSU is a fundamental data unit in SS7 (Signalling System No. 7) and its adaptations for mobile networks (like MAP). It carries signalling information between network nodes for call control, mobility management, and supplementary services. In 3GPP contexts, it's crucial for legacy circuit-switched signalling and its interworking with IP-based systems.

Machine Type Communications - InterWorking Function

The MTC-IWF is a core network function that acts as a secure gateway between external MTC Servers and the 3GPP network. It authorizes service requests, translates protocols, and forwards device trigger messages to the HSS/HLR, enabling secure machine-to-machine communication.

Modify UE context Request

A Diameter-based command used within the Policy and Charging Control (PCC) architecture to request modifications to a User Equipment's (UE) session context. It enables dynamic policy updates, such as changes to QoS parameters or charging rules, without requiring a full session re-establishment.

Non-3GPP Message Gateway

A 5G Core Network function that routes and processes signaling messages between the core and external non-3GPP application servers or networks. It acts as a secure gateway for SMS, MMS, and other messaging services over non-3GPP accesses.

Non-3GPP access InterWorking Function

The N3IWF is a core network function that enables secure, seamless integration of non-3GPP access networks (like Wi-Fi) into the 5G Core. It acts as a trusted gateway, terminating IPsec tunnels from untrusted non-3GPP access points and relaying traffic to the 5G Core over the N2 and N3 interfaces. This is crucial for providing unified 5G services across heterogeneous access technologies.

Network Access Provider

The entity that owns and operates the physical and logical radio access network (RAN) infrastructure through which a user connects. It provides the wireless connectivity but may be separate from the service provider. This distinction is key for MVNO models, roaming, and network sharing agreements.

Network Address and Port Translation

NAPT is a network function that translates both IP addresses and port numbers, allowing multiple private IPv4 devices to share a single public IPv4 address. It is essential for conserving scarce public IPv4 addresses and enabling large-scale network address translation within 3GPP networks, particularly for user plane traffic.

NAPT and Protocol Translation

NAPT-PT combines Network Address and Port Translation with protocol translation between IPv4 and IPv6. It enables communication between IPv4-only and IPv6-only networks or applications, acting as a crucial transition mechanism during the migration from IPv4 to IPv6.

Network Address and Port Translation IPv4 to IPv4

NAPT44 is a specific type of Network Address and Port Translation where both the internal (private) and external (public) address families are IPv4. It is the standard, large-scale NAT function used to map many private IPv4 addresses to a shared pool of public IPv4 addresses, forming the basis of Carrier-Grade NAT.

Network Address and Port Translation IPv6 to IPv4

NAPT64 is a transition mechanism enabling IPv6-only clients to communicate with IPv4-only servers by translating IPv6 addresses and ports to IPv4. It is essential for IPv6 migration, allowing operators to deploy IPv6 networks while maintaining backward compatibility with legacy IPv4 internet services.

Network Address Translation

A method of remapping IP address spaces, used in 3GPP networks to conserve public IPv4 addresses and provide privacy. It translates private IP addresses used within the mobile network to public addresses for communication with the internet. NAT is essential for enabling massive-scale connectivity in mobile networks where public IPv4 addresses are scarce.

NAT Traversal

A set of techniques and protocols that allow network applications, especially VPNs and real-time communication, to function correctly through Network Address Translation (NAT) devices. In 3GPP, it ensures services like IMS-based VoLTE/VoNR and enterprise VPNs work seamlessly across mobile networks employing NAT. It is critical for maintaining end-to-end connectivity and service quality.

Network Address Translation IPv4 to IPv4

NAT44 is a core network function that translates private IPv4 addresses to public IPv4 addresses, enabling multiple devices within a private network to share a single public IP. It conserves the scarce public IPv4 address space and provides a basic layer of security by hiding internal network topology.

Network Address Translation IPv6 to IPv4

NAT64 is a translation technology that allows IPv6-only clients to communicate with IPv4-only servers on the Internet. It is a key transition mechanism in 3GPP networks for enabling IPv6 deployment while maintaining backward compatibility with the vast legacy IPv4 Internet.

Non-EPS Alert Flag

A flag used in the 4G Evolved Packet System (EPS) to indicate that a user, currently not reachable in the EPS, may be reachable via a non-EPS service (like 2G/3G Circuit-Switched networks). It triggers the network to attempt delivery of waiting messages or calls via alternative access networks.

Network Exposure Function

The Network Exposure Function (NEF) is a 5G core network function that securely exposes network capabilities and events to authorized third-party applications and service providers. It acts as a controlled gateway, enabling new service creation, innovation, and network monetization by translating between external API requests and internal 3GPP protocols.

Network Function

A functional building block within a 3GPP network, with well-defined external interfaces and functional behavior. It can be implemented as a dedicated hardware appliance, a software instance on dedicated hardware, or a virtualized function (VNF/CNF) in a cloud environment. NFs interact via service-based interfaces to deliver end-to-end telecommunications services.

Network Functions Virtualization

A network architecture paradigm that decouples network functions (like firewalls, load balancers, or EPC/5GC nodes) from proprietary hardware appliances. These functions are implemented as software instances—Virtual Network Functions (VNFs)—running on commercial off-the-shelf (COTS) servers in a cloud environment. This enables agility, scalability, and cost reduction.

Non-GPRS Alert Flag

The Non-GPRS Alert Flag (NGAF) is an information element used in the GSM/UMTS circuit-switched core network to indicate that a mobile subscriber has an active packet-switched (GPRS) session. It enables coordination between circuit-switched and packet-switched domains for services like simultaneous voice and data.

Next Generation Core Network

NGC refers to the 5G Core Network (5GC), a cloud-native, service-based architecture that provides connectivity, mobility management, and session management for 5G devices. It is a key enabler for network slicing, edge computing, and diverse 5G service requirements.

Next Generation Corporate Network / Next Generation Core Network

NGCN initially referred to Next Generation Corporate Network, a concept for enterprise connectivity. From Release 15 onwards, it was repurposed within 3GPP documentation to stand for Next Generation Core Network, aligning with the standardized 5G Core (5GC) architecture.

Next Generation Networks

NGN is a broad architectural concept for migrating telecom networks from circuit-switched to packet-switched (IP-based) infrastructure. In 3GPP, it refers to the evolution of the core network to support multimedia services over IP, encompassing the IP Multimedia Subsystem (IMS) and later the Evolved Packet Core (EPC). It enables convergence of fixed and mobile services.

Network Mode of Operation

Defines the operational configuration of a mobile network's core, particularly regarding the coexistence and interworking of Circuit-Switched (CS) and Packet-Switched (PS) domains. It determines how voice services are delivered (e.g., CS Fallback, VoLTE) and impacts device behavior and network architecture.

NAS Node Selection Function

NNSF is a function in the core network that selects the appropriate NAS (Non-Access Stratum) node for a UE. It ensures efficient NAS signaling routing, optimizing resource use and session management in mobile networks.

Network Operator Tunneling Exchange

A functional entity or reference point facilitating secure tunneling and data exchange between network operators, particularly for services like SMS, MMS, or location-based services. It enables inter-operator service delivery while abstracting underlying network details.

Number Portability Database Dip Indicator

A parameter used in SIP signaling within the IP Multimedia Subsystem (IMS). It indicates whether a query to a Number Portability Database (NPDB) has been performed to determine the current network of a ported telephone number. This ensures correct routing and billing for calls to numbers that have been transferred between operators.

Number Portability Location Register

A core network database that stores routing information for mobile numbers that have been ported between operators. It enables call routing to the correct network when a subscriber has changed service providers but kept their phone number, a key regulatory requirement.

New Radio connected to 5G Core Network

NR/5GC refers to the end-to-end 5G system architecture where the New Radio (NR) access network is connected to the 5G Core (5GC) network. This is the standard, native deployment for 5G, enabling all advanced 5G services like network slicing, edge computing, and service-based architecture. It represents a clean break from previous 4G core dependencies.

No Reply Call Timer

The No Reply Call Timer (NRCT) is a timer used in circuit-switched mobile networks to manage call setup when the called party does not answer. It determines how long the network will wait for an answer before releasing the call attempt and potentially redirecting it to voice mail or an announcement.

Network Requested PDP Context Activation

A procedure in GPRS and UMTS networks where the network core (GGSN) initiates the establishment of a data session (PDP context) towards a mobile device. This enables the network to push data to the device or trigger it to establish an always-on IP connection, which is essential for services like push email, instant messaging, and mobile-terminated data sessions.

Network Requested Support Network

Network Requested Support Network (NRSN) is a core network concept where a network requests support from another network, such as for roaming or inter-operator services. It involves signaling between networks to facilitate services like authentication, billing, or resource sharing, defined in specifications like TS 23.060 and TS 29.060.

Network Request Support UE

NRSU is a UE capability indicating support for the Network Requested Bearer Control procedure, allowing the network to initiate the establishment or modification of Packet Data Protocol (PDP) contexts or Packet Data Unit (PDU) sessions. This capability is essential for network-initiated Quality of Service (QoS) management and efficient resource allocation for services like IMS voice.

Network Service Entity

A functional entity within the Base Station System (BSS) that provides network services, particularly for signaling transport. It acts as an endpoint for signaling links, such as those used by the Base Station System Application Part (BSSAP), facilitating communication between the BSS and the core network. It is essential for reliable control plane connectivity.

NAS Signalling Low Priority Indication

A NAS-level indication set by the UE to signal that a NAS signalling request is of low priority. It is used during congestion control in the network, allowing the MME to prioritize high-priority signalling requests (like emergency calls) over non-essential ones, thereby improving network resilience and service availability for critical procedures.

Network Status Request

A signaling procedure used to request the status of a network entity or service. It is a fundamental mechanism for network elements to query the operational state or availability of other elements, supporting network management and service continuity.

Network Sub System

The core circuit-switched network domain in GSM, responsible for call control, mobility management, and subscriber data. It comprises key nodes like the MSC, VLR, HLR, and EIR that work together to enable voice calls, SMS, and basic mobility services.

Non-Seamless WLAN Offload Function

A 5G core network function that manages the policy-based routing of user plane traffic to a WLAN access network without providing session continuity. It determines which traffic flows can be offloaded based on operator policies and access network conditions.

National User Part

A variant of the SS7 Signaling System User Part (UP) protocol defined for use within a single country's telecommunications network. It handles national-specific call control and circuit-related signaling between exchanges, adapting the international standard to local regulatory and network routing requirements.

Originating IP Multimedia Basic Call State Model

A finite state machine model used in the IMS to define and control the sequence of events for an originating IP multimedia session, such as a SIP-based call or video session. It provides the framework for CAMEL service logic to interact with and influence the call processing, enabling advanced, network-controlled services.

Originating IP Multimedia CAMEL Subscription Information

Subscriber data stored in the HSS that instructs the S-CSCF on when and how to invoke CAMEL-based service logic for sessions originating from that user. It contains the address of the service control node (gsmSCF) and a trigger profile specifying which Detection Points in the O-IM-BCSM are active.

Outgoing - Media Gateway Control Function

A functional role of the MGCF when it is controlling a Media Gateway (MGW) for a call leg that is exiting the IMS network towards a circuit-switched network, such as the PSTN or legacy PLMN. It performs protocol interworking between SIP (IMS) and ISUP/BICC (CS network).

Originating Mobile Switching Centre

The Mobile Switching Centre (MSC) that handles the call control and switching functions for a mobile-originated call. It is the first MSC in the call path, responsible for setting up the connection from the calling subscriber towards the destination, whether that is another mobile, a fixed line, or a service node.

Overload Control Information

Overload Control Information (OCI) is a signaling mechanism used in IMS and 5G core networks to prevent server overload. It allows a network function (NF) to signal its load level to other NFs, enabling them to throttle or redirect requests. This is critical for maintaining network stability and service availability during traffic surges or failure scenarios.

Outgoing Leg Control Model

A control model used in the CAMEL (Customised Applications for Mobile network Enhanced Logic) architecture to manage the outgoing leg of a call or session. It defines the interaction between the gsmSCF (CAMEL service control function) and the MSC/GMSC for controlling call setup and routing.

Originating Local Exchange

A functional entity in the 3GPP IMS (IP Multimedia Subsystem) architecture, specifically within the IMS Centralized Services (ICS) framework. It acts as the MSC (Mobile Switching Centre) enhanced for ICS that handles the circuit-switched leg of a call for a UE using IMS for service control.

Originating Line Information

Originating Line Information (OLI) is a parameter used in call signaling within the IP Multimedia Subsystem (IMS). It identifies the type of line or service from which a call originates (e.g., payphone, cellular, ISDN). This information is crucial for billing, routing decisions, and applying specific service logic based on the call origin.

Proxy Call Session Control Function

The Proxy Call Session Control Function (P-CSCF) is the first point of contact for a User Equipment (UE) within the IMS (IP Multimedia Subsystem). It acts as a SIP proxy, forwarding SIP messages between the UE and the IMS core, and enforces network policies. It is critical for establishing, managing, and terminating multimedia sessions like VoLTE and VoNR.

Packet Data Network Gateway

The P-GW is a core network node in 3GPP EPS that serves as the interface between the mobile network and external packet data networks (PDNs), like the internet. It performs key functions including IP address allocation, policy enforcement, charging, and packet filtering, acting as the anchor point for user mobility.

PDN Address Allocation

PDN Address Allocation (PAA) is a parameter in 3GPP protocols that specifies the IP address assigned to a UE for a Packet Data Network (PDN) connection, such as IPv4, IPv6, or both. It is carried in signaling messages between the network and UE during PDN connectivity establishment, enabling IP address management and session routing. PAA ensures proper address configuration for user data traffic over cellular networks.

Packet Assembler/Disassembler

A network function, historically in GPRS support nodes, that formats user data packets into the appropriate protocol data units for transmission over the radio network and vice versa. It handles adaptation between different network layer protocols and the specific framing requirements of the air interface.

Personal Broadcast Service Function

A core network function within the 3GPP architecture responsible for managing and controlling Personal Broadcast Service (PBS) sessions. It handles service logic, group management, broadcaster authorization, and interaction with the BM-SC for content delivery, acting as the central control entity for the PBS feature.

Policy and Charging Enforcement Function

A core network function within the Policy and Charging Control (PCC) architecture that enforces dynamic policy decisions (e.g., gating, bandwidth limits) and applies charging rules for user data sessions. It is typically co-located with the gateway (e.g., PGW, GGSN, P-GW, UPF) and is the ultimate point of policy enforcement in the user plane.

Packet-switched Core Network Node

A generic 3GPP term encompassing all core network nodes responsible for packet-switched data services, including SGSN, GGSN, S-GW, P-GW, and TDF. It provides a unified reference for policy, charging, and management functions across different network generations (2G/3G/4G).

Policy and Charging Rules Function

The PCRF is the brain of the Policy and Charging Control (PCC) architecture in 3GPP networks. It makes real-time policy decisions for service data flows based on subscriber profiles, network conditions, and service information. It determines QoS parameters and charging rules, which it provisions to the PCEF (e.g., PGW) for enforcement. This enables dynamic, service-aware network control and monetization.

Proxy Call Session Control Function

The PCSCF is the first point of contact for a User Equipment (UE) in the IP Multimedia Subsystem (IMS). It acts as a Session Initiation Protocol (SIP) proxy, handling session control, security, and policy enforcement for IMS-based services like VoLTE and VoNR. It is critical for establishing and managing multimedia sessions over the packet-switched domain.

Packet Data Gateway

A core network gateway function in 3GPP systems that provides secure, IP-based connectivity between User Equipment (UE) and external Packet Data Networks (PDNs), such as the internet or corporate intranets. It is a key component for enabling mobile broadband and IP-based services.

Packet Data Network

A Packet Data Network (PDN) is any external IP-based network (like the internet or an enterprise intranet) that a mobile user's device connects to through the mobile operator's core network. It represents the destination network for user data traffic and is a fundamental concept for data service provisioning in 3GPP systems. The core network provides the connectivity and gateway functions to access these PDNs.

Packet Data Network Gateway

The Packet Data Network Gateway (PDN-GW or PGW) is the core network node in the 4G Evolved Packet System (EPS) that serves as the anchor point for a UE's session to an external Packet Data Network (PDN). It performs IP address allocation, policy enforcement, charging, packet filtering, and lawful interception. It is the primary gateway between the LTE/EPC network and external IP networks like the internet.

Packet Data Protocol

PDP defines the protocol used for packet data transmission in 2G/3G/4G networks, enabling IP connectivity for mobile devices. It establishes a logical context between the User Equipment and the Gateway GPRS Support Node (GGSN) to manage IP address allocation, QoS, and routing. This is foundational for mobile internet services.

Packet Detection Rule

A Packet Detection Rule (PDR) is a fundamental policy construct in the 5G User Plane Function (UPF) and 4G/5G Traffic Detection Function (TDF). It defines a set of matching criteria (e.g., IP header fields) and associated actions (e.g., forwarding, buffering, charging) to identify and process user plane packets. PDRs enable dynamic, fine-grained traffic steering and policy enforcement.

Packet Data Subsystem

The Packet Data Subsystem (PDS) is a core network architecture component defined for IP Multimedia Subsystem (IMS) services. It provides the framework for packet-switched data services, including session control, policy enforcement, and user plane handling. It is crucial for enabling multimedia services over LTE and 5G networks.

Policy Enforcement Function

PEF is a network function that enforces policy decisions for user sessions, such as QoS, charging, and access control. It ensures that network resources are allocated according to operator policies, enabling dynamic service management and efficient resource utilization in mobile networks.

Policy Enforcement Point

A functional entity within the Policy and Charging Control (PCC) architecture that enforces policy decisions. It resides in the gateway (e.g., P-GW, TDF) and applies gating, QoS, and charging rules to user data flows. It is the execution point that translates policy rules into network actions.

Packet Flow Context

A logical context in the SGSN and GGSN that manages the state and parameters for a specific packet data flow of a user. It is essential for applying correct QoS, charging, and routing policies to individual data streams within a PDP context, enabling differentiated service handling.

Packet Flow Management

Packet Flow Management (PFM) is a set of procedures and protocols in GSM/EDGE and GPRS core networks for establishing, modifying, and releasing packet data contexts and associated data transfer resources (Packet Flows) between a Mobile Station and the network. It is fundamental for managing the user plane bearers for packet-switched services.

Packet Flow Timer

A Packet Flow Timer (PFT) is a network-controlled timer used in GPRS/EDGE systems to manage the state and resources of a Temporary Block Flow (TBF) or a Packet Flow Context. It governs the release of radio and network resources after a period of inactivity to optimize efficiency.

PDN Gateway

The PDN Gateway is a critical core network element in the Evolved Packet System (EPS). It serves as the anchor point for a UE's session to external Packet Data Networks (like the internet or IMS). The PGW performs key functions including IP address allocation, policy enforcement, charging, and packet filtering, acting as the primary gateway between the LTE/5G network and the outside world.

PDN Gateway Control plane function

The control plane component of the PDN Gateway in the 5G Core network. It handles session management, policy enforcement, and charging control for user data sessions. It is a key element in the Control and User Plane Separation (CUPS) architecture.

PDN Gateway User plane function

The user plane component of the PDN Gateway in the 5G Core network. It performs packet forwarding, inspection, buffering, and QoS enforcement for user data traffic. It is the data forwarding anchor point in the CUPS architecture, enabling flexible and distributed deployment.

Packet Handler Function

A functional entity within the 3GPP Generic User Profile (GUP) architecture. It is responsible for handling and managing packet data aspects of a user's profile, facilitating access to and distribution of user-specific packet data service information across network elements.

Point In Association

A reference point or logical association within the core network, often used in CAMEL or service layer contexts. It defines specific interaction points for service logic execution, enabling customized call control and service delivery in mobile networks.

Port Management Information Container

A data structure used within the 5G Core Network to convey port management information, such as port status and configuration, between network functions. It is primarily used in the interaction between the Session Management Function (SMF) and the User Plane Function (UPF) for managing N4 session contexts.

Paging and Notification Control Functional Entity

A core network functional entity in UMTS responsible for initiating and controlling paging procedures to locate User Equipment (UE) in idle or connected mode. It manages the distribution of paging requests to the correct Radio Network Controllers (RNCs) within a specific area.

Paging Policy Differentiation

PPD (Paging Policy Differentiation) is a 5G feature that allows the network to apply different paging strategies based on service type, UE status, or network conditions. It optimizes paging signaling load and improves success probability by tailoring parameters like retransmission schemes and paging area size, enhancing efficiency for diverse 5G use cases.

Provide Roaming Number

A temporary MSISDN assigned by the VLR to enable call routing to a roaming subscriber. It is a key mechanism in GSM/UMTS networks for establishing mobile-terminated calls when the subscriber is outside their home network, ensuring seamless connectivity.

Packet Switched Public Data Network

A public network that provides packet-switched data communication services to subscribers. In 3GPP contexts, it often refers to external networks like the Internet or corporate intranets that a mobile user's device connects to via the mobile operator's core network (e.g., via GGSN or PGW).

Permanent Virtual Circuit

A Permanent Virtual Circuit (PVC) is a pre-configured, permanent logical communication path established in a packet-switched network, such as one based on Frame Relay or ATM. It provides a constant connection between two network endpoints, emulating the characteristics of a dedicated leased line but over shared network infrastructure. PVCs are used in legacy 3GPP core networks for stable, predictable connectivity between network nodes like SGSNs and GGSNs.

Previous Visitor Location Register

The Previous VLR (PVLR) is a network parameter used during mobility procedures, such as location updates or inter-MSC handovers, to identify the subscriber's previous serving VLR. It is crucial for correctly routing signaling messages and retrieving subscriber data from the HLR, ensuring seamless mobility and call delivery.

Requesting Gateway Mobile Location Centre

A core network entity in the LTE/5G location services (LCS) architecture that acts as the client's entry point. It receives location requests from external Location Based Service (LBS) applications, authenticates and authorizes them, and forwards the request to the appropriate network node (H-GMLC or visited network) to obtain the target UE's position.

Roaming Signalling Gateway

A network function in the IP Multimedia Subsystem (IMS) that acts as a signaling gateway for roaming subscribers. It facilitates the interconnection between different operators' networks by performing protocol translation, typically between SIP over IP and legacy SS7-based signaling, enabling IMS services for roaming users.

Reverse Call Setup Direction

A mechanism in circuit-switched networks where the call setup direction is reversed, allowing the called party to initiate the establishment of the call path. It optimizes routing and resource allocation, particularly in international or inter-operator scenarios, improving efficiency and reducing setup delays.

Routing Determination Function

A network function that determines the optimal routing path for sessions or messages based on subscriber data, service policies, and network conditions. It is used in CAMEL, IMS, and other 3GPP systems to enable intelligent routing decisions for voice, messaging, and data services.

Routing Functional Entity

Routing Functional Entity (RFE) is a logical function within the 3GPP Core Network, primarily in GSM and UMTS, responsible for determining the next routing hop for signaling messages. It resides in network nodes like the MSC, SGSN, or GGSN to enable efficient and reliable message delivery across the network interfaces. It is fundamental for mobility management and call/session control.

Remote Transcoder Operation

A network architecture where speech codec transcoding functions are moved from the mobile switching center (MSC) to a dedicated node or further toward the network edge. This optimizes voice traffic handling, reduces transmission costs, and improves voice quality by minimizing tandem coding operations in legacy and VoIP networks.

Shared Core

S-CORE is a 3GPP architectural concept enabling multiple mobile network operators (MNOs) or network slices to share a common core network infrastructure. It reduces deployment and operational costs while maintaining logical separation and independent service provisioning for each sharing entity.

Serving Call Session Control Function

The S-CSCF is the central node of the IMS core, responsible for session control and service delivery. It authenticates users, processes SIP signaling, enforces policy, and interacts with application servers to enable multimedia services like VoLTE and VoNR.

Serving Gateway

The Serving Gateway (S-GW) is a critical core network node in 3GPP EPS (4G) and early 5G NSA architectures. It acts as the mobility anchor point for the user plane during inter-eNodeB handovers and as the local anchor for inter-3GPP mobility (e.g., 2G/3G/4G). It routes and forwards user data packets, manages bearers, and performs lawful interception.

Split/Combine Function

The Split/Combine Function is a network element in the IP Multimedia Subsystem (IMS) that manages the splitting and combining of media flows for multi-device and multi-access scenarios. It enables a single IMS session to be distributed across multiple user devices or access networks, supporting services like call continuity and simultaneous ringing.

S8 Home Routing

S8 Home Routing is an architectural model for 5G roaming where the User Plane connection (S8-U) is routed directly from the Visited PLMN's UPF to the Home PLMN's UPF, while control signaling (S8-C) traverses the home network. It enables home-routed traffic for service consistency and policy enforcement.

Single Association Control Function

A functional entity within the CAMEL (Customized Applications for Mobile network Enhanced Logic) service architecture that controls a single association or dialog between a gsmSCF (service control function) and a gsmSSF (service switching function). It manages the state and execution of one CAMEL service interaction, ensuring proper invocation, event handling, and termination of the service logic.

System Architecture Evolution

The core network architecture for LTE and beyond, defining the Evolved Packet Core (EPC). It provides an all-IP, flat architecture for high-speed data, enabling efficient mobility and service delivery. It is foundational for 4G networks and evolved into the 5G Core.

Single-Connection Mode

An operational mode for a UE where it maintains a single, simultaneous Packet Data Network (PDN) connection or association to a single network (3GPP or non-3GPP). It is a fundamental connectivity state defined for network-based mobility management, contrasting with multi-connection scenarios.

Service Communication Proxy

A core network function that provides a centralized, secure, and scalable proxy for service-based interface (SBI) communications between network functions (NFs) in 5G. It enables discovery, load balancing, and security, simplifying service mesh management and enhancing network reliability.

Serving Call Session Control Function

The SCSCF is a central node in the IMS (IP Multimedia Subsystem) core network. It handles session control, user authentication, and service triggering for multimedia services like VoLTE and VoNR. It is critical for enabling rich communication services over IP networks.

Secondary DN Authentication and Authorization over EPC

A mechanism enabling a secondary Data Network (DN) to perform its own authentication and authorization of a UE connected via the Evolved Packet Core (EPC). It allows service providers to enforce independent security policies beyond the 3GPP network's access authentication, crucial for secure enterprise and IoT access.

Signalling Gateway Function

The Signalling Gateway Function (SGF) is a network function that facilitates interworking between IP-based signalling protocols (like SIP) and legacy circuit-switched signalling protocols (like SS7). It is crucial for enabling seamless communication and service continuity between 4G/5G networks and older 2G/3G networks, ensuring backward compatibility and efficient network evolution.

Serving GPRS Support Node

The Serving GPRS Support Node (SGSN) is a core network element in 2G/3G mobile networks responsible for packet-switched data services. It manages mobility, session management, and user authentication for GPRS and UMTS subscribers, routing data packets between the mobile station and external networks.

Signalling Gateway

The Signalling Gateway (SGW) is a network element that facilitates interworking between different signalling transport technologies, typically converting legacy SS7 signalling over TDM links to IP-based SIGTRAN protocols. It enables core network entities to communicate using modern IP transport while supporting legacy interfaces.

Serving Gateway Control plane function

The SGW-C is the control plane component of the Serving Gateway (SGW) in a 5G and evolved 4G architecture. It handles session management, mobility anchoring, and policy enforcement for user data sessions, separating control logic from packet forwarding to enable network flexibility and scalability.

Serving Gateway User plane function

The SGW-U is the user plane component of the Serving Gateway, responsible for the actual forwarding, routing, and QoS enforcement of user data packets. It is controlled by the SGW-C via the PFCP protocol, enabling flexible, distributed deployment of packet processing resources at the network edge.

Serving Gateway / Packet Data Network Gateway

The SGW and PGW are key nodes in the Evolved Packet Core (EPC) for 4G LTE networks. The SGW routes and forwards user data packets, acting as the mobility anchor during handovers. The PGW provides connectivity to external packet data networks, enforces policy, and performs IP address allocation.

Selected IP Traffic Offload

SIPTO is a network optimization feature that allows an operator to offload certain types of IP traffic (typically internet-bound) from the mobile core network at a network node closer to the user, such as at a local gateway. This reduces latency, improves user experience, and alleviates congestion on the core network and backhaul links.

Shared Inter Working Function

A network function in early 3GPP releases (Rel-4/5) that provided shared interworking between the circuit-switched (CS) core network and external networks, like PSTN. It enabled efficient resource sharing for functions like signaling and media conversion, reducing deployment costs for operators transitioning to packet-switched architectures.

Signalling Link Code

The Signalling Link Code (SLC) is a numeric identifier used in SS7 and SIGTRAN-based signalling networks to uniquely distinguish between multiple parallel signalling links connecting the same two signalling points (SPs). It is essential for link management, load sharing, and failure recovery within a linkset.

Subscription Location Function

A core network function in IMS and 5G that locates the appropriate HSS or UDM for a given subscriber. It is essential for routing queries to the correct user data repository in multi-vendor or geographically distributed networks, enabling scalable subscriber management.

Session Management Congestion Control

Session Management Congestion Control is a set of network mechanisms designed to prevent, detect, and mitigate congestion specifically in the control plane procedures related to PDU session management. It protects the Session Management Function (SMF) and related signaling interfaces from overload during high traffic or attack scenarios.

Short Message Service - Center

The central network node in SMS architecture, responsible for storing, forwarding, and routing short messages. It ensures reliable delivery by managing message queues, interacting with HLR for subscriber location, and handling delivery reports. Critical for SMS operation across mobile generations.

Short Message Service Gateway MSC

The SMS-GMSC is a Gateway MSC that acts as the entry point for Mobile-Terminated Short Messages (MT-SM) from an external Short Message Service Centre (SMSC) into the GSM/UMTS core network. It queries the HLR to retrieve the recipient's current routing information and forwards the SMS accordingly.

Short Message Service Interworking MSC

The SMS-IWMSC is an Interworking MSC that acts as the exit point for Mobile-Originated Short Messages (MO-SM) from the GSM/UMTS core network to an external Short Message Service Centre (SMSC). It receives messages from the serving MSC and delivers them to the appropriate SMSC.

Short Message Service - Service Centre

The SMS-SC is the central network element responsible for storing, forwarding, and routing Short Message Service (SMS) messages. It acts as the hub for all SMS traffic, interfacing with other core network nodes to deliver messages. Its role is critical for reliability, enabling store-and-forward functionality and value-added services.

Support of Optimal Routing

SOR is a CAMEL (Customized Applications for Mobile network Enhanced Logic) feature that enables optimal routing of mobile-terminated calls. It allows the network to query the HLR for routing information even when the subscriber is roaming, avoiding costly and inefficient tromboning routes. This reduces call setup time and minimizes international transit costs.

Service-based Policy Decision Function

A 5G core network function that provides a service-based interface for making policy decisions related to network slicing. It acts as a central policy authority within a network slice instance, translating slice-specific service requirements into actionable network policies.

Signal Processing Network Equipment

A network function defined within the Media Resource Function (MRF) of the IP Multimedia Subsystem (IMS). It is responsible for processing media streams, providing capabilities such as audio/video transcoding, mixing, and analysis to enable advanced telecommunication services like conferencing and announcements.

Switched PVC

SPVC (Switched PVC) is a core network technology in 3GPP that enables dynamic switching of Permanent Virtual Circuits in packet-switched networks, such as GPRS and EPS. It optimizes resource utilization by establishing on-demand connections between network nodes, reducing static configuration overhead and improving scalability for data services.

Send Routeing Information

A core network procedure used to retrieve routing information for a mobile subscriber, such as the current serving MSC or SGSN address. It is essential for call delivery, SMS routing, and location-based services, ensuring network entities can locate and communicate with a subscriber's device.

Session and Service Continuity Mode Selection Policy

A policy in the 5G Core (5GC) that determines the appropriate Session and Service Continuity (SSC) mode for a PDU Session. The policy is applied by the SMF, considering subscription data, network policies, and UE capabilities. It ensures the PDU Session's IP anchor point continuity meets the service requirements, balancing mobility and session stability.

Service Switching Function

A core network function, originally from Intelligent Network (IN) architecture, that detects service triggers and interacts with the Service Control Function (SCF). In 3GPP systems, it is integrated into the MSC or GMSC to enable value-added circuit-switched services like prepaid, freephone, and VPN. It acts as the gateway between the call processing and the service logic.

Signalling Transport Network

The Signalling Transport Network (STN) is a logical or physical network infrastructure dedicated to carrying signalling traffic between network elements. It ensures reliable, secure, and efficient delivery of control plane messages, which is critical for call setup, mobility management, and session control. The STN underpins the robustness and scalability of the entire mobile core network.

Switched Virtual Circuit

Switched Virtual Circuit (SVC) is a circuit-switched connection established dynamically on demand for the duration of a communication session, used in legacy 2G/3G GSM and UMTS networks for voice and circuit-switched data services. It sets up a dedicated path through the network with guaranteed bandwidth. This contrasts with permanent virtual circuits and is a foundational concept for traditional mobile telephony.

Satellite Virtual Network

A logical network abstraction that enables satellite access networks to integrate with 3GPP core networks, allowing User Equipment (UE) to access services via satellite links. It provides mobility and session management, extending terrestrial cellular coverage to remote areas.

Terminating Basic Call State Model

A standardized model within the CAMEL protocol defining the states and events for a terminating call (incoming to a subscriber). It enables the GMSC to trigger service logic (e.g., call forwarding) at specific points during call setup.

Terminating CAMEL Subscription Information

A set of subscriber data stored in the HLR that defines CAMEL service logic for terminating calls (incoming). It is sent to the GMSC to instruct it on which services to invoke and where to find the service control platform.

Trunking Media Gateway Function

A Media Gateway Function (MGF) specialized for handling high-capacity trunking interfaces, typically between circuit-switched networks (like PSTN) and packet-switched networks (like IMS). It performs media conversion (e.g., TDM to IP) and processing for bulk traffic, such as inter-carrier connections or access to legacy networks.

Terminating MSC

The Mobile Switching Center (MSC) that handles the terminating (incoming) leg of a circuit-switched voice call to a mobile subscriber. It is responsible for routing the call from the gateway MSC, performing subscriber interrogation (like HLR query), and establishing the connection to the subscriber's current serving MSC or radio network.

Transport Signalling Gateway

A network function in the 3GPP IMS architecture that performs signalling protocol conversion, primarily between IP-based SIGTRAN (e.g., SCTP/IP) and legacy circuit-switched signalling (e.g., SS7 over TDM). It enables interworking between modern IP networks and traditional telephony systems.

Terminal Adaptation Function

The Terminal Adaptation Function (TAF) is a functional entity in legacy 3GPP circuit-switched core networks, specifically for GSM and early UMTS. It adapts data terminal equipment (DTE), like a computer, to a mobile termination (MT) device, such as a phone or modem. The TAF handles protocol conversion and rate adaptation, enabling non-voice services like fax and circuit-switched data calls over the mobile network.

Traffic Detection Function

A network function that performs application detection, gating, and redirection for traffic. It is a key component for policy and charging control (PCC), enabling operators to identify application traffic and apply appropriate policies.

Traffic Detection Function Control plane function

The control plane component of the TDF, responsible for managing application detection rules and policies. It interfaces with the PCRF/PCF, separating control logic from user plane packet processing for scalability and flexibility.

Traffic Detection Function User plane function

A user plane function within the 5G core network responsible for inspecting and detecting application traffic flows. It enables policy enforcement, charging, and traffic steering based on deep packet inspection, supporting advanced service-aware network operations.

TransFer Allowed

A parameter or indicator within mobility management procedures that signals whether the transfer of a subscriber's context or session to a new network node is permitted. It is crucial for managing handovers, session continuity, and subscriber data management during network transitions.

TFO Enable

TFOE is a control parameter used in the 3GPP core network to enable or disable Tandem Free Operation (TFO). It is crucial for managing the transcoding of speech codecs in the call path to improve voice quality and reduce bandwidth usage by avoiding unnecessary tandem transcoding operations.

Transfer Prohibited

TFP is a signaling message used in the SS7/SIGTRAN-based core network, specifically within the SCCP layer. It indicates that a signaling point cannot forward messages for a specific destination, triggering rerouting and is critical for maintaining signaling network reliability and congestion control.

Traffic Flow Template

A set of packet filters used in the Packet Data Protocol (PDP) context of GPRS, UMTS, and EPS to classify downlink user plane packets and associate them with specific bearers for appropriate QoS treatment. It enables service-aware traffic management and policy enforcement.

Topology Hiding Inter-network Gateway

A Session Initiation Protocol (SIP) application-level gateway deployed at network borders to conceal internal network topology from external IP Multimedia Subsystem (IMS) networks. It modifies SIP message headers to hide sensitive routing information, enhancing network security and operator confidentiality.

Translation Information Flag for Camel Subscription Information

TIF-CSI is a CAMEL service indicator flag used in GSM/UMTS networks to signal whether translation information for a called party number is required for Intelligent Network (IN) service triggering. It ensures accurate service logic execution by indicating if number portability or other translation data is needed before invoking CAMEL services.

Trunking Media Gateway

A network element that performs media conversion and processing between circuit-switched (CS) trunking networks (like PSTN/ISDN) and packet-switched (PS) IP networks (like IMS). It is essential for enabling voice and multimedia services across legacy and modern networks, handling transcoding, echo cancellation, and bearer control.

Trusted Non-3GPP Access Network

A non-3GPP access network (e.g., Wi-Fi, fixed broadband) that has a trusted, secure connection to the 5G Core network. The 5G Core treats it similarly to a 3GPP RAN, enabling seamless authentication and service continuity. This allows operators to integrate and manage heterogeneous access technologies under a unified core.

Trusted non-3GPP Access Peers

Network functions or entities within a trusted non-3GPP access network that directly interface with the 5G Core. They act as the peer endpoints for control plane (N2) and user plane (N3) connections, facilitating the integration of Wi-Fi and fixed networks. TNAPs enable the 5GC to manage these accesses as native entities.

Trusted Non-3GPP Gateway Function

A 5G Core Network function that provides secure, trusted access for User Equipment (UE) connecting via non-3GPP access networks, such as Wi-Fi. It acts as a gateway, authenticating the UE and establishing IPsec tunnels to ensure secure data transmission into the 5G Core. This enables seamless service continuity and unified policy control across 3GPP and non-3GPP access.

Transit Network Selection

A mechanism for selecting a transit network for routing calls between different operators or networks. It is crucial for inter-operator connectivity, cost optimization, and ensuring call completion across administrative boundaries by allowing the selection of specific carriers or routes.

Traffic Plane Function

The Traffic Plane Function (TPF) is a network element responsible for enforcing policy and charging rules on user data traffic in real-time. It interfaces with the Policy and Charging Rules Function (PCRF) to apply gating, filtering, prioritization, and charging actions, enabling advanced service control and monetization.

Transit and Roaming Function

A core network function defined for IP Multimedia Subsystem (IMS) networks, primarily responsible for routing SIP signaling messages between different operator networks. It handles the transit of SIP traffic for roaming users and inter-operator interconnection, performing topology hiding, security screening, and policy enforcement at network borders.

Trusted WLAN Access Gateway

The Trusted WLAN Access Gateway (TWAG) is a core network gateway function within a Trusted WLAN Access Network (TWAN). It provides IP connectivity and mobility management for User Equipment (UE) accessing the 3GPP Evolved Packet Core (EPC) via a trusted, non-3GPP WLAN. It acts as the termination point for the S2a interface based on the GTP or PMIPv6 protocol.

Trusted WLAN Access Network

The Trusted WLAN Access Network (TWAN) is a 3GPP-defined architectural concept representing an operator-controlled WLAN that is securely integrated with the mobile core network. It comprises functional nodes like the TWAG and TWAP, enabling seamless access to 3GPP services with full authentication, policy, and mobility support.

Trusted WLAN AAA Proxy

The Trusted WLAN AAA Proxy (TWAP) is a control plane function within a Trusted WLAN Access Network (TWAN). It proxies AAA signaling between the WLAN and the 3GPP AAA infrastructure, facilitating SIM-based authentication, authorization, and session management for UEs accessing the core network via trusted WLAN.

Trusted WLAN Interworking Function

The TWIF is a 5G core network function that enables secure, seamless interworking between 3GPP 5G systems and trusted, non-3GPP access networks like WLAN. It acts as a security gateway and protocol translator, allowing UEs to access 5G core services over Wi-Fi with the same authentication and policy control as cellular access.

Unified Data Management

The core network function in the 5G Service-Based Architecture (SBA) that manages subscriber data, identities, and authentication credentials. It is the central repository for user profiles, generating authentication vectors and providing subscription data to other network functions like the AMF and SMF.

Unified Data Repository

A centralized data storage function in the 5G Core (5GC) that consolidates subscriber and policy data. It provides a single, unified repository for structured data like subscription, policy, and application data, enabling efficient data management and access for network functions. This supports service agility, network slicing, and streamlined operations.

Unstructured Data Storage Function

A 5G Core network function that provides storage for unstructured data, such as session context or temporary state information. It offers a simple, generic storage service accessible via APIs, allowing other Network Functions to offload state management. This supports stateless design, scalability, and efficient service continuity.

Update Location Request

ULR is a Diameter command used in the 5G core network (5GC) between the Access and Mobility Management Function (AMF) and the Unified Data Management (UDM). It is sent to register a UE's current location, retrieve subscription data, and authenticate the user, forming the basis of mobility and session management.

UMTS Mobile Services Switching Centre

The core network switching node in a 3G UMTS circuit-switched domain, responsible for call control, mobility management, and switching of circuit-switched voice and data services. It is the functional evolution of the GSM MSC, adapted for the UMTS radio access network.

User Plane Interworking Unit

The UP-IWU is a functional entity that facilitates interworking between different generations of mobile core networks, specifically between a 5G Core (5GC) and an Evolved Packet Core (EPC). It translates user plane protocols and handles data forwarding when a UE is served by a 5G RAN but anchored in a 4G core, or vice-versa, enabling smooth migration and coexistence.

User Plane Entity

A logical network function defined in early LTE system architecture studies (SAE) responsible for processing and forwarding user data traffic. It represented the user plane gateway in the Evolved Packet Core (EPC), handling packet routing, forwarding, and QoS enforcement for mobile broadband services.

User Plane Function

The core network function in the 5G System (5GS) responsible for packet routing and forwarding, packet inspection, QoS handling, and traffic usage reporting. It is the central anchor point for the user data plane, connecting the (R)AN to external data networks and enabling key 5G features like network slicing and edge computing.

User Plane Gateway

A functional entity introduced in 3GPP Release 14 for 5G networks, responsible for user plane traffic forwarding and processing. It plays a crucial role in network slicing and edge computing by enabling flexible user plane function deployment. It separates the user plane from the control plane, enhancing scalability and service delivery.

User Profile Server Function

A network function that stores and manages user-centric data (subscription, preferences, policies) for service delivery. It acts as a unified data repository, enabling personalized services and policy enforcement across IMS, 5G, and other service domains.

User Reachability Request Parameter for SGSN

URPP-SGSN is a specific parameter used in the GTP-C (GPRS Tunnelling Protocol - Control plane) signaling between a Serving GPRS Support Node (SGSN) and a Gateway GPRS Support Node (GGSN) or Packet Data Network Gateway (PGW) in 2G/3G/4G networks. It indicates the SGSN's request for the GGSN/PGW to provide notifications about the UE's reachability status (e.g., when it becomes reachable after being unreachable), enabling efficient downlink data delivery and paging optimization.

UE Reachability Request Parameter for AMF

A parameter used by the SMF to request the AMF to perform UE reachability procedures in 5G. It triggers the AMF to page the UE or check its connection status, enabling efficient downlink data delivery when the UE is in idle or inactive state.

User Reachability Request Parameter for MME

A parameter in 4G EPC used by the SGW to request the MME to perform UE reachability procedures. It triggers paging to locate an idle UE when downlink data arrives, initiating the network-triggered service request procedure to re-establish bearers.

UE Reachability Request Parameter for SGSN

A parameter used by the SGSN to request the MME to perform a UE reachability procedure. It is a key element in the interworking between 2G/3G GPRS and 4G EPC networks, enabling efficient paging and mobility management across different radio access technologies.

Visited AF

An Application Function located in a visited network (VPLMN) when a user is roaming. It interfaces with the visited network's Policy and Charging Rules Function (V-PCRF) to apply dynamic policy control for the subscriber's services. It enables localized service delivery and policy enforcement in roaming scenarios.

Visited Charging Function

A Charging Function (CHF) located in the Visited Public Land Mobile Network (VPLMN). It enables real-time charging for roaming subscribers by interfacing with the home network's CHF. This is critical for accurate billing and policy control in roaming scenarios.

Visited Diameter Routing Agent

A Diameter Routing Agent (DRA) located in the visited network. It routes Diameter signaling messages between network elements in roaming scenarios, ensuring proper message delivery between visited and home networks. It is essential for policy, authentication, and charging signaling.

Visited Policy and Charging Enforcement Function

A Policy and Charging Enforcement Function (PCEF) located within the Visited Public Land Mobile Network (VPLMN). It enforces policy and charging rules for a roaming subscriber, interfacing with the home network's PCRF to apply the correct Quality of Service (QoS) and charging policies while the user is outside their home network.

Visited Policy Control Function

A Policy Control Function located in the Visited Public Land Mobile Network (VPLMN) for a roaming User Equipment (UE) in the 5G System. It acts as the primary policy decision point in the visited network, interfacing with the Home PCF to enforce the home operator's policies on access and mobility, session management, and network slice selection.

Visited Policy and Charging Rules Function

A Policy and Charging Rules Function (PCRF) located within the Visited Public Land Mobile Network (VPLMN). It acts as a proxy or co-operative decision point, interfacing with the Home PCRF to provide policy and charging rules for the V-PCEF to enforce on a roaming subscriber's traffic.

Visited Session Management Function

A Session Management Function deployed in a Visited Public Land Mobile Network (VPLMN) that provides session management services for a roaming user. It is a key component in the 5G roaming architecture, enabling local breakout and ensuring efficient data routing without always requiring traffic to be tunneled back to the home network.

Visited Unified Data Repository

A Unified Data Repository function deployed within a Visited Public Land Mobile Network (VPLMN). It stores subscription and policy data relevant for roaming users, allowing the visited network to make local decisions without constant querying of the home network, improving efficiency and latency.

Visited Gateway Mobile Location Centre

VGMLC is a GMLC located in the visited network when a roaming subscriber requires location services. It acts as an intermediary to protect subscriber privacy and enforce local regulations, ensuring secure and compliant location information retrieval across network boundaries.

Voice over IP Gateway

VGW is a network gateway that interconnects circuit-switched voice networks (like PSTN or legacy mobile) with IP-based networks (like IMS or internet). It converts voice traffic between TDM and IP formats, enabling seamless voice call continuity and service interoperability across different network domains.

Visitor Location Register

A core network database that stores subscriber data for mobile users currently roaming in the service area of a specific Mobile Switching Center (MSC). It enables call routing, authentication, and service provisioning for visiting subscribers by temporarily caching data from their home HLR.

Visitor Location Register for the A-subscriber

The specific VLR that is currently serving the calling party (A-subscriber) in a mobile-originated communication. It is a functional designation used within call control and charging procedures to identify the network node handling the originating user's context.

Visitor Location Register for the B-subscriber

The specific VLR that is currently serving the called party (B-subscriber) in a mobile-terminated communication. It is a functional designation used in call routing, termination services, and charging to identify the network node handling the receiving user's context.

Visited Mobile Switching Center

The Mobile Switching Center (MSC) in the cellular network a subscriber is currently roaming in. It handles call control, switching, and mobility management for visiting subscribers, enabling seamless roaming between different operator networks.

Visited Mobile Switching Center of the A-subscriber

Specifically denotes the Visited MSC that is currently serving the calling party (A-subscriber) in a mobile-originated call. It is used in call routing and charging procedures to identify the network element handling the call originator's side, especially in complex scenarios like call forwarding.

Visited MSC of the B subscriber

The Visited MSC of the B subscriber is the Mobile Switching Center (MSC) serving the called party (B-subscriber) in a circuit-switched call. It is a key functional entity in GSM/UMTS networks for routing calls to roaming subscribers and managing call setup, handling, and supplementary services.

VoIP Positioning Centre

The VoIP Positioning Centre (VPC) is a network function defined for emergency call services in IMS-based networks. It is responsible for obtaining, validating, and providing the location of a VoIP caller to the appropriate emergency services network, ensuring accurate routing and dispatch of first responders.

Mobile Terminating in VMSC

VT (Mobile Terminating in VMSC) is a call model and routing concept in circuit-switched mobile networks where a call to a mobile subscriber is terminated at the Visited Mobile Switching Center (VMSC) serving the subscriber's current location. It is a fundamental mechanism for call delivery in GSM/UMTS networks, enabling efficient routing and charging for inbound calls to roaming subscribers by leveraging the visited network's infrastructure.

Wireline Access Gateway Function

The W-AGF is a 5G core network function that provides fixed wireline access to the 5G system. It acts as a gateway, converting protocols from fixed networks (like DSL, PON) into 5G core protocols, enabling wireline devices to be managed as 5G devices. This is crucial for Fixed Wireless Access (FWA) and converged 5G networks.

WLAN - APN

W-APN is an Access Point Name specifically used for routing user data traffic between a mobile device connected via a Wireless Local Area Network (WLAN) and a Packet Data Network (PDN). It identifies the gateway and service (e.g., IMS, internet) for WLAN access, enabling seamless data services over Wi-Fi.

Wireless Access Gateway

The Wireless Access Gateway (WAG) is a core network element that provides secure, controlled interworking between 3GPP mobile networks and non-3GPP IP access networks, such as WLANs. It acts as a gateway for authentication, authorization, and IP traffic routing, enabling seamless service continuity and secure data offload. Its role is critical for early mobile-WLAN integration and converged network access.