Patent ID: 7966017

Claim:
A method of performing a connected mode handover of a user equipment (UE) from a serving base station to a target base station during discontinuous reception (DRX) operation in a mobile communication system, the method comprising the steps of: transmitting, by the UE, a cell change report to the serving base station in which the UE is located, and then suspending the DRX operation to transition to an active mode; receiving, by the UE, a handover command message transmitted from the serving base station, and completing the handover to a target cell under a control of the target base station; checking, by the UE, if a DRX resume condition included in the handover command message is a first condition that performs additional procedures after the handover completion; when the DRX resume condition is the first condition, waiting, by the UE, until a control message including a DRX resume command is received from the target base station; and transitioning, by the UE, from the active mode to a sleep mode, and resuming the DRX operation after the control message including the DRX resume command is received.