Research On Some Technologies Of Mobility Management In WiMAX System

WiMAX is the abbreviation of Worldwide Interoperability for Microwave Access,which is a new wireless metropolitan area networks technology based on IEEE802.16standard. WiMAX can provide high-speed connection for Internet. IEEE802.16standard is an open broadband wireless access technology, which supports high data rateand a range of mobility. Mobility management that provides real-time, low-cost,high-quality and optimized service to mobile node becomes a challenging research issue.Indubitably, mobility management plays an important role in the efficient operation ofmobile communication networks. Mobility management includes location managementand handover management. Handover management includes handover criterion,handover strategy and resource management related to handover.In this dissertation, the handover management of mobility management based onWiMAX technology is studied. The main research contents and innovative results arelisted as follows:1. Aiming at handover problem of WiMAX, a new cross-layer handover schemedesigned for fast handover in hierarchical mobile IPv6over WiMAX MAC handover isproposed. MAC layer handover and IP layer handover are carried out alternately in thisscheme. Some IP layer handover steps are finished before the MAC layer connectionhas been broken, which can accelerate the handover process and reduce the handoverlatency.2. The handover mechanism in WiMAX relay system is studied, which includescanning procedure and handover algorithm. Firstly, in view of cost of scanningprocedure, a new optimization scheme is proposed. The number of the messagetransferred during scanning procedure is reduced by modifying the messages, thusdecreases the cost. Secondly, different scanning types of scanning procedure anddifferent scanning times in different scanning types are studied. Influence of differentparameters on scanning time is analyzed. Then, macro diversity handover algorithms ofrelay system are proposed based on the idea of WiMAX macro diversity handover.Using random walk mobility model, different algorithms are simulated and comparedunder a same scenario. Simulation results show that the proposed algorithms have lesshandover number. Finally, aiming at the update mechanism of anchor BS in macrodiversity handover algorithm, a new selection method of anchor BS is given. The effect of the selection methods of anchor BS on handover number is studied. Results show thatthe new selection method leads to less handover number.3. First, Proxy Mobile IPv6is researched, that is a network based mobilitymanagement protocol. An analytical model of performance analysis is given. Based onthis analytical model, handover latency and cost of different mobility managementprotocols are compared. Then, performance analysis of different protocols by analyticalmodel are given, using IEEE802.16e based wireless metropolitan area networks as thewireless access network. The performances of these protocols are evaluated by somemetrics like handover latency, service disruption time and data delivery cost. Finally, anew fast handover protocol is proposed through the combination of Proxy Mobile IPv6and Fast Handover for Mobile IPv6. After the comparison with the existing ProxyMobile IPv6，it can be seen that the proposed fast handover protocol can achieve lowerhandover latency．4. The average time of finding an idle channel during spectrum handover incognitive radio system is too long. In order to solve this problem, an optimizationscheme is proposed. Using soft combination cooperative spectrum sensing, this schemeoptimizes the sensing time of the single primary user channel to get the shortest averagetime of finding idle channel. Simulation results give the different shortest average timeof finding idle channel and the corresponding sensing time of the single primary userchannel with different parameters.5. An adaptive resource scheduling algorithm with QoS guarantees is proposed forWiMAX Mesh network topology. The scheduling order is determined according to thepriority, QoS satisfaction and topology information of service flows in this algorithm.The system throughput, rtPS packet loss rate and nrtPS throughput of differentalgorithms are compared by simulation. Simulation results show that the proposedadaptive resource scheduling algorithm can meet various QoS requirements, increasethe system throughput with priority-based algorithm.