On what basis UE decides whether it should trigger TAU procedure or not ?
Yes it is mandatory to do TAU after handover if the target ENB TAC is not part of TAI_list which UE has. If target ENB is part of TAI-list then there wont be any TAU from UE.
Yes it is needed as after X2 handover where MME is not involved, MME does not know the location of UE if it happens to be in a different TA.
After UE handover to target ENB it sent RRC Connection Reconfiguration complete.why UE doing suddenly Tracking Area Update request? Even it is in RRC-Connected State.
Does anyone has an idea, after handover procedure when MME gets changed , target MME sends update location request to HSS ?
What could be the scenario in which source eNodeB triggers "handover cancel" procedure towards the MME ?