A method for performing a handover of a mobile subscriber station, MSS, by a serving base station, BS, in a broadband wireless access, BWA, communication system including the MSS, the serving BS, and a plurality of neighbor BSs (560, 580, 590), the method comprising the steps of: transmitting, to the MSS, a handover request message including information on at least one recommended BS (560, 580) to which the MSS can perform handover, among the neighbor BSs, and an information field indicating whether the serving BS supports a network assisted handover; receiving, from the MSS, a handover indication message including an identifier, ID, field; receiving information related to a handover process of the MSS from the selected target BS after receiving the handover indication message; transmitting a notification for ordering a release of a source allocated to the MSS, to other at least one recommended BS excluding the selected target BS from the at least one recommended BS, in response to receiving the information related to the handover process; and wherein the network assisted handover indicates that the MSS performs a handover to the selected target BS among the at least one recommended BS without notifying the serving BS of the selected target BS, wherein, if the information field does not indicate that the network assisted handover is supported, the ID field in the handover indication message is set to a value indicating a selected target BS determined by the MSS among the at least one recommended BS, and wherein, if the information field indicates that the network assisted handover is supported, the ID field in the handover indication message is set to a predefined value that does not indicate a certain target BS. transmitting, to the MSS, a handover request message including information on at least one recommended BS (560, 580) to which the MSS can perform handover, among the neighbor BSs, and an information field indicating whether the serving BS supports a network assisted handover; receiving, from the MSS, a handover indication message including an identifier, ID, field; receiving information related to a handover process of the MSS from the selected target BS after receiving the handover indication message; transmitting a notification for ordering a release of a source allocated to the MSS, to other at least one recommended BS excluding the selected target BS from the at least one recommended BS, in response to receiving the information related to the handover process; and wherein the network assisted handover indicates that the MSS performs a handover to the selected target BS among the at least one recommended BS without notifying the serving BS of the selected target BS, wherein, if the information field does not indicate that the network assisted handover is supported, the ID field in the handover indication message is set to a value indicating a selected target BS determined by the MSS among the at least one recommended BS, and wherein, if the information field indicates that the network assisted handover is supported, the ID field in the handover indication message is set to a predefined value that does not indicate a certain target BS.