Patent ID: 8798004

Claim:
A method for performing a handover in a wireless access system, the method comprising: receiving, by a mobile station (MS) from a serving base station (SBS), a handover command message including an action time field indicating a number of a frame in which the MS starts to perform network reentry; receiving, by the MS from a target base station (TBS), a SFH (super frame header) including a ranging opportunity; and transmitting, by the MS to the TBS, a ranging code on or after the frame indicated by the action time field for the network reentry, wherein, when a dedicated ranging code and a dedicated ranging information are included in the handover command message, the dedicated ranging code is transmitted in a subframe indicated by the dedicated ranging information, the dedicated ranging code and the dedicated ranging information being a ranging code and a ranging opportunity dedicated to the MS, respectively, wherein the dedicated ranging information indicates a subframe index of a ranging opportunity allocated by the TBS, and wherein, when the dedicated ranging code and the dedicated ranging information are not included in the handover command message, a randomly selected ranging code is transmitted through the ranging opportunity indicated by the SFH.