In a communication system, a mobile station (MS) sends a target base station (BS) a notification indicating that it is to perform a handover from a serving BS to the target BS. The target BS transmits to the MS handover process optimization information indicating a possibility of omitting at least one process required by the MS to perform a network re-entry operation with the target BS according to the handover notification from the MS. The MS receives the handover process optimization information and performs a network re-entry operation with the target BS according to the handover process optimization information.