Question: In a GSM network, when a Mobile Station (MS) undergoes a cell change, how does the Base Station Subsystem (BSS) inform the Serving GPRS Support Node (SGSN) about the Local Service Area (LSA) ID of the new cell?
Option 1: By sending an LSA UPDATE message directly to the SGSN
Option 2: Through periodic Location Update messages initiated by the MS
Option 3: By adding the LSA ID(s) of the current/new cell to the UL UNITDATA message
Option 4: Via a dedicated LSA Notification protocol between BSS and SGSN
Explanation: Adding the LSA ID(s) of the current/new cell to the UL UNITDATA message is a specified procedure for informing the SGSN about cell changes, efficiently utilizing existing signaling pathways with minimal overhead. This approach is technically plausible and aligned with telecom network operations, as UL UNITDATA messages are part of GPRS signaling for user data transfer.