Patent ID: 8804663

Claim:
A method for performing handover in a wireless communication system, the method comprising: receiving, by a mobile station from a serving base station, a handover command message including: information related to a disconnect time, wherein the information related to the disconnect time is configured in units of frames, wherein the disconnect time is a time for the mobile station to disconnect from the serving base station, and wherein the disconnect time indicates a time point at which the serving base station stops sending downlink data to the mobile station and stops an uplink resource allocation for the mobile station, and an action time for the mobile station to transmit a ranging request to a target base station; if the mobile station cannot maintain a connection with the serving base station until the disconnect time, transmitting, by the mobile station to the serving base station, a handover indication message for disconnecting the mobile station from the serving base station earlier than the disconnect time; and transmitting, by the mobile station to the target base station, the ranging request based on a dedicated ranging code at the action time.