WLAN Specific Identifier

Description

The WLAN Specific Identifier (WSID) is a subscription identifier defined within the 3GPP framework to facilitate interworking between 3GPP cellular networks and non-3GPP access networks, specifically WLANs. It is stored within the Universal Subscriber Identity Module (USIM) and is used by the network to uniquely identify a user's subscription for WLAN-specific procedures. The primary architectural role of the WSID is within the authentication and authorization framework, where it may be used in conjunction with or as an alternative to other identifiers like the IMSI, particularly in scenarios defined by the Wireless LAN Interworking (I-WLAN) specifications.

Operationally, the WSID is utilized during the Extensible Authentication Protocol (EAP) authentication process when a User Equipment (UE) attempts to attach to a WLAN that is integrated with the 3GPP core network. The network, specifically the Authentication, Authorization, and Accounting (AAA) server, can use the WSID to retrieve the correct subscriber profile and authentication credentials from the Home Subscriber Server (HSS). This process is detailed in specifications such as TS 24.234 (3GPP system to Wireless Local Area Network (WLAN) interworking) and TS 31.102 (Characteristics of the Universal Subscriber Identity Module (USIM) application).

Key components involving the WSID include the USIM where it is stored, the UE's WLAN stack that presents it during authentication, and the network's AAA infrastructure and HSS that process it. Its role is pivotal in enabling a standardized, secure method for cellular operators to extend their services and billing models to Wi-Fi hotspots, ensuring that the user experience is consistent and managed under the operator's policy framework. The identifier helps decouple WLAN access authentication from the core cellular identity, providing flexibility in service offering.

Purpose & Motivation

The WSID was introduced to address the growing need for seamless and secure integration between cellular networks and WLANs. Prior to its standardization, operators lacked a consistent, standardized method to identify and authenticate their subscribers on Wi-Fi networks, leading to fragmented user experiences and complex, proprietary authentication mechanisms. The creation of the WSID was motivated by the 3GPP's work on I-WLAN in Release 6, which aimed to define a unified architecture for interworking.

The technology solves the problem of subscriber identity management in heterogeneous access environments. By providing a WLAN-specific identifier stored on the USIM, it allows operators to leverage the existing SIM-based security infrastructure for WLAN access. This approach addressed limitations such as the need for separate usernames/passwords for Wi-Fi and enabled tighter integration with the operator's core network for services like authentication, authorization, and charging. It formed a foundational element for early network convergence efforts.