her hand (Figure 1.17): - trusted Wi-Fi access via the STa interface; - untrusted Wi-Fi access via the SWa interface; - PGW entity via the S6b interface; - ePDG entity via the SWm interface; - HSS entity via the SWx interface. Server Trusted Untrusted Wi-Fi Wi-Fi Access Access Figure 1.17. AAA server interfaces using the DIAMETER protocol Wi-Fi Integration to the 4G Mobile Network The SWx interface is used by the AAA server to retrieve the authentication data; the subscriber profile and the parameters for the PMIPv6, MIPv41 FA, GTPv2 and DSMIPv6 mechanisms. The SWx interface is used to register the address of the PGW and the AAA server in the HSS when establishing tunnel S2a, S2b or S2c. The SWx interface is used by the HSS entity for updating the mobile profile and for detaching it. Table 1.1 summarizes the DIAMETER messages exchanged on the SWx interface. Messages Comments AAA server request to retrieve Multimedia-Authentication-Request (MAR) authentication data HSS entity response containing Multimedia-Authentication-Answer (MAA) authentication data AAA server request to register the PGW Server-Assignment-Request (SAR) entity and retrieve the mobile profile HSS entity response containing mobile Server-Assignment-Answer (SAA) profile Registration-Termination-Request (RTR) HSS server request for mobile detachment Registration-Termination-Answe (RTA) AAA server response to RTR request Push-Profile-Request (PPR) HSS entity request for mobile profile update Push-Profile-Answer (PPA) AAA server response to PPR request Table 1.1. DIAMETER messages on the SWx interface The STa and SWa interfaces share the same authentication procedure. During the authentication phase, the AAA server decides whether Wi-Fi access is trusted or untrusted and communicates the decision to the Wi-Fi access point. The STa and SWa interfaces are used to carry information relating to the PMIPv6, MIPv4 FA (only in the case of the STa interface), GTPv2 and DSMIPv6 mechanisms. Architecture Based on Wi-Fi Access The STa and SWa interfaces are used