Question: In an IMS (IP Multimedia Subsystem) using GPRS/EPS access, which entity can trigger the retrieval of user location and/or UE Time Zone information from the SGSN/MME for scenarios requiring this data prior to session delivery?
Option 1: P-CSCF (Proxy-Call Session Control Function) via PCC mechanisms
Option 2: IMS AS (Application Server) via the HSS (Home Subscriber Server)
Option 3: MGCF (Media Gateway Control Function) directly from the SGSN/MME
Option 4: UE (User Equipment) initiating a location request to the network
Explanation: According to IMS procedures for retrieving network-provided location information, when user location and/or UE Time Zone information is required but not already available (e.g., prior to session delivery), an IMS Application Server (IMS AS) can initiate the retrieval process. This is done via the HSS, as specified in relevant 3GPP technical specifications, ensuring operator policy coordination for appropriate method usage in specific scenarios.