Question: When a UE accesses IMS via an untrusted WLAN, what additional information is required to be provided along with the cell-ID (if available) during specific procedures like IMS registration and emergency session initiation?
Option 1: WLAN AP identity and geographical location coordinates
Option 2: Timestamp of when the cell-ID was last updated and UE's IP address
Option 3: Information describing when the cell-ID data was collected to calculate its 'age'
Option 4: Details of the UE's operating system and device model
Explanation: According to IMS specifications for untrusted WLAN access, providing the cell-ID (if available) during certain procedures must be accompanied by additional information that indicates when the cell-ID data was collected. This allows for the calculation of the 'age' of the cell-ID information, which is crucial for assessing its relevance and accuracy in locating the UE or making registration decisions.