The Design Of Simulation Platform Of Wimax System And Study Of Handover Algorithms

WiMAX technology which is based on the IEEE802. 16 protocol familiy is a promising broadband wireless access system. The key technique of next generation mobile system has been utilized in WiMAX, like Orthogonal Frequency Division Multiplexing, Adaptive Modulation and Coding and Hybrid Automaitc Transmission Request. QoS guarantee is also included. WiMAX provides the mechanism of radio resource management such as scheduling, access control and handover, but does not specify concrete algorithms. This job has been left to the vendors for the sake of segment of the market. This dissertation studied the mecheanism of QoS and handover in WiMAX, and further implemented simulation module on both Matlab and NS2 platform. After comparing the different way of event-driven and time-driven, a QoS based handover algorithm is designed. This algorithm consider the channel status of physical layer and the slot usage of MAC layer, as well as the serviece flow combined with the load of current base station and target base station. The handover decision is made and the target base station is chosen based on these factors. The goal is to improve the ratio of successful handover and thus reduce the time wasted on cell reselection and further decrease the overall delay of handover. Meanwhile the inter-BS load balance is also achieved. Simulation compared with traditional RSSI-based algorithm is conducted.The result shows that the proposed algorithm can not only guarantee the QoS after the handover but also balanced the load of different base stations.