Question: In a Voice Group Call Service (VGCS), if a mobile station has stored group IDs "123" and "1234" in its SIM/USIM, which group ID will it derive from a group call reference of "91234"?
Option 1: The mobile station will not be able to derive any group ID.
Option 2: The mobile station will derive both "123" and "1234" as valid group IDs.
Option 3: The mobile station will derive "1234" as the group ID, being the longest match.
Option 4: The mobile station will always derive the shortest stored group ID, so it will derive "123".
Explanation: According to the VGCS specifications, the mobile station derives the group ID by identifying the **longest** group ID amongst those stored in the SIM/USIM that matches the least significant digits of the group call reference. Since "1234" is the longest match for the group call reference "91234", it will be derived as the group ID. This ensures that the most specific and likely intended group ID is selected when multiple matches are possible, based on the stored IDs in the SIM/USIM.