Generic Access - Packet Switched Resources

Description

Generic Access - Packet Switched Resources (GA-PSR) is the counterpart to GA-CSR within the 3GPP Generic Access Network (GAN) architecture, responsible for delivering packet-switched data services. It allows a User Equipment (UE) to establish a data session and access services like internet browsing, email, and IMS over a secure IP connection via an unlicensed radio technology like Wi-Fi, while being fully managed by the mobile operator's core network.

Functionally, GA-PSR operates in conjunction with GA-CSR on the UE and the Generic Access Network Controller (GANC). The UE's GA layer encapsulates all GPRS signaling (GMM/SM) and user data packets into IPsec-secured packets for transport over the broadband IP link. At the GANC, the GA-PSR function terminates this secure tunnel. It then forwards the GPRS signaling to the Serving GPRS Support Node (SGSN) over the standard Gb or lu-ps interface. For the user plane, the GA-PSR function relays data packets between the UE's IPsec tunnel and the GTP-U tunnel established between the GANC (acting as a BSS/NodeB proxy) and the SGSN/GGSN.

This architecture ensures that all packet data protocols (PDP) contexts are managed centrally by the SGSN. The operator maintains control over authentication (via SIM credentials), charging, and policy enforcement (e.g., APN filtering) even for traffic traversing Wi-Fi. GA-PSR supports mobility procedures, allowing a data session to be suspended on Wi-Fi and resumed on cellular, or in some implementations, handed over seamlessly. It provides a unified data service experience, bridging the gap between cellular data and untrusted WLAN access.

Purpose & Motivation

GA-PSR was developed to extend the benefits of GAN/UMA beyond voice to packet data services. While I-WLAN provided a method for Wi-Fi data access, it often required a separate authentication and billing stream. GA-PSR aimed for deeper integration, allowing operators to offer a completely seamless data service where the access network (cellular or Wi-Fi) was abstracted from the user and the service platform.

It solved the problem of fragmented user experience and complex billing for dual-mode device users. Without GA-PSR, using Wi-Fi for data might mean launching a separate connection manager and losing access to operator-specific services or being billed separately. GA-PSR enabled the operator to treat Wi-Fi access as another radio access technology under its direct control, allowing for consistent service policies, unified billing records, and access to subscriber-specific services like operator portals or IMS.

The creation of GA-PSR was motivated by the desire for true Fixed-Mobile Convergence (FMC) for all services. It allowed Mobile Network Operators to leverage dense Wi-Fi deployments to offload data traffic from congested macro cellular networks while retaining visibility and control over the subscriber's data session. This was a strategic tool for competing with pure-play internet service providers and managing the explosive growth of mobile data demand cost-effectively.

Key Features

• Enables GPRS/UMTS packet data services over unlicensed IP access networks
• Integrates Wi-Fi data sessions into the operator's core packet network (SGSN/GGSN)
• Uses IPsec for secure tunneling of all GPRS signaling and user plane data
• Supports standard PDP context activation, modification, and deactivation procedures
• Allows for operator-controlled authentication, charging, and policy enforcement
• Facilitates data session continuity mechanisms between Wi-Fi and cellular access

Evolution Across Releases

Defining Specifications