Question: What event marks the end of the cell re-selection delay for a User Equipment (UE) in a 1.28 Mcps TDD network, according to 3GPP specifications?
Option 1: Receipt of the first downlink packet from the new cell
Option 2: Completion of the RRC CONNECTION REQUEST message transmission
Option 3: Initiation of sending the SYNCH-UL sequence in the UpPTS for the RRC CONNECTION REQUEST
Option 4: Successful completion of the Location Registration on the new cell
Explanation: The correct answer is Option 3 because, as defined by the specifications, the cell re-selection delay ends when the UE starts to send the SYNCH-UL sequence in the UpPTS, which is a precursor step for sending the RRC CONNECTION REQUEST to perform a Location Registration on the new cell. This marks the moment the UE has effectively camped on and begun interacting with the new cell at a protocol level.