Question: In a scenario where a UICC does not contain an ISIM application, how is a Temporary Public User Identity derived for SIP registration procedures in an IMS network?
Option 1: Derived from the USIM's IMSI and used for all SIP procedures.
Option 2: Assigned randomly by the P-CSCF during initial SIP registration.
Option 3: Derived from the MSISDN stored on the USIM.
Option 4: Not derived; instead, a Permanent Public User Identity is used.
Explanation: When no ISIM application is present on the UICC, both Private and Temporary Public User Identities are derived from the USIM's IMSI for unique user identification within the operator's network. The Temporary Public User Identity is utilized in SIP registration procedures, ensuring compatibility with the network's requirements for user identification during these processes.