APPARATUS AND METHOD FOR A HANDOVER IN A COMMUNICATION SYSTEM

摘要

An apparatus and a method for handover in a communication system are provided to minimize a loss of downlink data, which are transmitted to a mobile station from a serving BS(Base Station), by transmitting an HO-IND-ACK(Handover Indication Acknowledge) message to the mobile station so that the mobile station can confirm whether an HO-IND message is successfully transmitted to the serving BS. A mobile station determines a target BS, which can provide a required bandwidth and QoS(Quality of Service), among neighbor BSs. The mobile station transmits a MOB_HO-IND(Mobile Handover Indication) message to a serving BS(201). In response to the MOB_HO-IND message, the serving BS sends an HO_IND_ACK message to the mobile station(203). Receiving the HO_IND_ACK message, the mobile station stops communicating with the serving BS and establishes synchronization with the target BS(205). If the synchronization between the mobile station and the target BS is established, the target BS sends a fast ranging information element to the mobile station and allocates radio resources for an RNG-REQ(Ranging Request) message the mobile station will transmit to the target BS(207). Using the allocated resources, the mobile station transmits the RNG-REQ message to the target BS(209). Receiving the RNG-REQ message, the target BS executes ranging with the mobile station. After executing ranging, the target BS transmits an RNG-RSP(Ranging Response) message to the mobile station(211). Also the target BS allocates radio resources so that the mobile station can send a confirm message for the RNG-RSP message(213). In response to the RNG-RSP message, the mobile station a BRH(Bandwidth Request Header) message to the serving BS(215). Receiving the BRH message, the target BS starts to transmit downlink data to the mobile station(217).