Question: What triggers a User Equipment (UE) to send an UPDATE message with a cause value of "cell reselection" during the cell re-selection process in a 7.68 Mcps TDD network?
Option 1: Receipt of a dedicated paging message from the new cell.
Option 2: Completion of a successful handover procedure initiated by the network.
Option 3: The UE's detection of a change in cell levels, prompting it to camp on a new cell.
Option 4: Expiration of a timer set for periodic location updates.
Explanation: During cell re-selection, the UE autonomously decides to switch to a new cell based on measured cell levels. Once the UE camps on this new cell, it initiates an UPDATE procedure with the specified cause, indicating the reason for the update is cell re-selection. This process is UE-driven, based on its assessment of surrounding cell signal strengths, and not directly triggered by network messages (like dedicated paging or handover commands) or periodic timer expirations.