Reducing Connection Disruption Time during WiMAX Handover

Mobile WiMAX, the enhanced version of the IEEE 802.16 standard with mobility support, defines the implementation of hard handover is mandatory. Being a break before make technique, the HHO concept in MWiMAX suffers from a lengthy “inter-handover” CDT that could lead to unwanted hazards like packet losses, call disruptions or even call drops, while on the move. This occurs in the actual handover phase, when an MS terminates the connection with the SBS and tries to set-up connections with the selected TBS. In MWiMAX, data, voice and multimedia contents are intermixed and each requires different mechanisms for its transmission, particularly during handover. So, such a lengthy CDT may cause serious service disruptions in case of real-time high-speed delay-sensitive voice and streaming multimedia applications in MWiMAX networks. To solve this problem without many changes to 802.16e equipments, we propose an enhanced link-layer QoS aware handover scheme-Passport Handover to accelerate handover process. We also propose a connection CID assignment strategy to avoid confliction of CIDs of handing over services with that of ongoing services in the target BS. Finally we have evaluated the performance using OPNET Modeler.