Research On Handover Schemes For Broadband Wireless Networks Based On WiMAX Technology

WiMAX technology based on IEEE 802.16 standard accelerates the manufacture of broadband wireless equipments and deployment of last-mile connection, and promotes the development of global broadband wireless networks. Handover management is one of the most important factors that greatly influence the performance of WiMAX networks, but relevant research and standardization are on the first stage. Based on the analysis of IEEE 802.16 standard and WiMAX network architecture, the handover mechanism for broadband wireless network based on WiMAX technology is studied in this thesis, for the purpose of improving the performance of WiMAX systemsFirstly, existing control messages are used, and handover decision algorithms, which are not defined in the standard, are supplemented to implement an intact and scientific hard handover process in this thesis. By setting up the simulation environment of IEEE 802.16e OFDMA TDD systems, the performances of handover decision algorithms based on signal strength, such as RSS, RSST, RSSH and RSSTH, are analyzed and compared. From the simulation results, RSSTH algorithm shows the best performance. And the best threshold and hysterresis margin of RSSTH are obtained.Secondly, based on the study of the QoS architecture of WiMAX network, a handover algorithm combining admission control policy based QoS is presented in this thesis. The algorithm takes into account the QoS requirements and the characters of five service classes: UGS, rtPS, ertPS, nrtPS, and BE, definded in the IEEE 802.16e-2005 standard. The simulation results show that by using guard-channel and proportional channel borrowing policies, the proposed algorithm not only provides a reasonable priority order for new originated connections and handover connections of different service classes, but also reduces the connection-blocking and connection-droping probabilities of each service class to a tolerable level.Thirdly, by analyzing the cause of handover latency in the IEEE 802.16e-2005 standard, a fast handover scheme in WiMAX broadband wireless network is proposed. The proposed scheme uses the measures such as choosing the neighbor BS with best CINR as the target BS for scanning, non-contention based fast ranging and pre-registratation, to optimize the redundances in existing handover scheme。The analyzing results show that the proposed fast handover scheme reduces the handover latency and the service interrupt time brought by scanning or association. At the same time, this scheme increases the probability of successful handovers and enhances QoS of the system.In the end, the research work in this thesis is included, and further research work is prospected.