A method of performing handover operation in a wireless communication system, the method comprising: receiving (S411; S611), at a serving base station a handover request message comprising a plurality of Information elements from a mobile station through a first communication link; transmitting (S412; S413; S612, S613) a handover pre-notification message from the serving base station to a target base station (43, 44); receiving (S414, S415; S614, S615) at the serving base station a handover pre-notification response message comprising handover related information from the target base station; transmitting (S417; S617) a handover response message from the serving base station to the mobile station, wherein the handover response message comprises said handover related information received from the target base station; receiving at the serving base station a first handover indicator message indicating a handover operation from the mobile station; after the receiving of the first handover indicator message, performing (S419 - S421) a setup procedure between the mobile station and the target base station to establish a second communication link with the target base station while maintaining the first communication link with the serving base station; receiving at the serving base station a second handover indicator message Indicating a handover cancel upon failure of the mobile station to establish the second communication link with the target base station from the mobile station, and after the receiving of the second handover indicator message from the mobile station, resuming normal communication with the mobile station using the maintained first communication link. receiving (S411; S611), at a serving base station a handover request message comprising a plurality of Information elements from a mobile station through a first communication link; transmitting (S412; S413; S612, S613) a handover pre-notification message from the serving base station to a target base station (43, 44); receiving (S414, S415; S614, S615) at the serving base station a handover pre-notification response message comprising handover related information from the target base station; transmitting (S417; S617) a handover response message from the serving base station to the mobile station, wherein the handover response message comprises said handover related information received from the target base station; receiving at the serving base station a first handover indicator message indicating a handover operation from the mobile station; after the receiving of the first handover indicator message, performing (S419 - S421) a setup procedure between the mobile station and the target base station to establish a second communication link with the target base station while maintaining the first communication link with the serving base station; receiving at the serving base station a second handover indicator message Indicating a handover cancel upon failure of the mobile station to establish the second communication link with the target base station from the mobile station, and after the receiving of the second handover indicator message from the mobile station, resuming normal communication with the mobile station using the maintained first communication link.