Abstract
To transmit bandwidth-intensive applications efficiently, multicast broadcast service (MBS) is one of the important features supported by Mobile WiMAX. As MBS services such as audio and video streaming are usually delay-sensitive, the concept of an MBS zone is also introduced to reduced the handover delay for MBS services. In an MBS zone, the participant BSs transmit the same MBS content synchronously, and MSs do not need to re-register and re-establish the multicast connection during handover between BSs in the same MBS zone. However, when the serving BS and the target BS belong to different MBS zones, the inter-MBS zone handover is performed. The longer inter-MBS zone handover delay and frame offsets between adjacent MBS zones will cause large packet loss and make the QoS of real-time applications infeasible. But the problem of huge packet loss caused by inter-MBS zone handover is little studied. In this paper, we propose an improvement on the inter-MBS zone handover procedure to greatly reduce the handover delay. Moreover, we also propose a data recovery scheme for inter-MBS zone handover by using extra multicast connections as recovery channels for MBS services to minimize the packet loss. Simulation results show that our proposed schemes achieve almost zero packet loss with relatively small number of recovery channels compared to the number of MBS sessions.