Question: What action does the UE take when there is a transmission failure of SECURITY MODE COMPLETE message or SECURITY MODE REJECT message indication from lower layers during a registration procedure?
Option 1: The UE shall abort the security mode control procedure and re-initiate the registration procedure.
Option 2: The UE shall continue with the ongoing procedure that triggered the security mode control procedure.
Option 3: The UE shall send a new SECURITY MODE COMPLETE message or SECURITY MODE REJECT message indication to the lower layers.
Option 4: The UE shall wait for further instructions from the network before taking any action.
Explanation: According to the specified abnormal case, when there is a transmission failure of SECURITY MODE COMPLETE message or SECURITY MODE REJECT message indication from lower layers during a registration procedure, the UE shall abort the security mode control procedure and re-initiate the registration procedure. This ensures that the UE can still establish a secure connection with the network despite the initial failure.