Patent ID: 8503394

Claim:
A method of transmitting uplink data during a handover in a wireless access system, the method comprising: transmitting, to a serving base station, quality of signal information periodically; receiving, from the serving base station, a handover command (HO command) message including a dedicated preamble and an identifier of a mobile station, wherein the identifier is for use at a target base station; synchronizing with the target base station using at least the identifier or the dedicated preamble; transmitting, to the target base station, a handover confirm (HO Confirm) message after a completion of the synchronization with the target base station, wherein the HO Confirm message comprises a header, a handover confirm payload and an information bit, wherein the information bit indicates whether the uplink data is present; receiving, from the target base station, information regarding a radio resource for transmitting the uplink data after a handover complete (HO Complete) message for indicating a completion of the handover of the mobile station is transmitted by the target base station to a Mobility Management Entity (MME); and transmitting, to the target base station, the uplink data via the radio resource.