Research On Key Techniques Of Mobile IPv6 In Heterogeneous Networks

The development of wireless technologies merges various wireless networks. Mobile IPv6 can integrate different wireless technologies into Heterogeneous Wireless Networks (HWN). HWN based mobile IPv6 will be used widely. Mobile nodes which have multiple interfaces can roam between different networks and access several networks simultaneously for more service.Comparing to wireless communication of single network, HWN provide more convenience for mobile users and also present more technical challenge. We discuss and analyze the problems of vertical handoff, interface selection, energy saving algorithm, application services and other related areas. The major research topic and contribution are as follows.Introduction of architecture and research contents of Heterogeneous Wireless Networks. Chapter I and II introduce the development of wireless technologies and protocol architecture of HWN. Based on the architecture, we analyze the related knowledge of key technology, including background theory, related researches and current problems. This provides the foundation of following researches.Received Signal Strength (RSS) threshold of vertical handoff. Chapter III proposes Mobile node Motion based Threshold algorithm (MMT). Vertical handoff is one of important technologies of HWN, which concern multiple research areas. After introduction of related research of handoff decision algorithm of vertical handoff, we analyze several typical algorithms of handoff decision. Handoff decision algorithms are based on single parameter or multiple parameters. RSS is very important parameter in both scenarios. In the research before, handoff threshold was configured as fixed signal strength. It didn't consider about the possible influence of mobility of mobile node. This chapter analyzes the different requirements of handoff threshold under different node velocities. By using free space propagation model, we analyze the threshold P_i (handoff in WLAN), P_o (handoff out WLAN), P_t, (execution of handoff out WLAN). In common configuration, people usually configure threshold as ratio of minimum RSS. So that, we calculate the ratio r_i and r_t, of each threshold comparing to minimum RSS. Further research shows the relationship of r_i and r_t, between handoff delay and scanning interval, which can be used calculate one threshold by another. Following simulation results validate the theoretical analysis. We analyze the deviation of threshold and define correction indexα, which can correct the r_i; when MN velocity is high.Selection of multiple interfaces and load balance. Chapter IV propose Dynamic Weight Multi-Interfaces Select algorithm (DWMIS). It is essential and useful to access multiple networks for mobile node with multiple interfaces. Firstly, we analyze multiple interfaces selection problem by traditional load balance mechanism. Secondly, we give the parameters needed for interface selection in HWN. It needs a generic valuation function for various parameters, so we propose DWMIS, which can integrate various parameters. This valuation function synthetically considers each parameter and user policy. It can calculate optimal interface by bandwidth, fairness, energy cost, money cost and etc. In implementation, when user initials a communication request, it needs a fast answer about current optimal interface. The decision module needs to know the link information of low layer. When request arrives, the Decision Module just acquires link parameters of each interface to calculate. That will cause delay. In our implementation, link monitor module periodically collects link parameters and sends them to decision module. However, the updating cycle, T_update, decides the accuracy of calculation. The smaller the cycle is, the more accurate the calculation is. But too small T_update may impose burden to the mobile node. So, there is a trade-off between the calculation accuracy and the system burden.Research of energy saving of IEEE 802.16e sleep mode. Chapter V proposes Linear Increase Algorithm (LIA). We introduce the significance of energy saving research as well as current work of sleep mode of IEEE 802.16e. Firstly, we describe the operation of sleep mode of IEEE 802.16e and present the weakness of original algorithm. After theoretical analysis of response time, power consumption under Poisson process traffic condition, we give the simulation experiment. We compare the two algorithms and conclude that the LIA has better performance. Secondly, we analyze the performance over different parameters. The results can be took into account when choose parameters. Finally, we propose that queues should be allocated in BS for buffer frames. This method can improve the performance of energy saving mechanism. This algorithm does not change the parameters in original standard and only improve the algorithm. The algorithm is compatible with original standard. It can be applicable in all mobile stations.Mechanism of construction VPN in dynamic network environment. As growing of mobile IPv6, some network applications (e.g. VPN technology) do not work well in dynamic network environment such as mobile IPv6 network. How to construct VPN is to be essential problem. Chapter VI proposes Dynamic Tunneling Mechanism (DTM) in mobile IPv6 network environment. Considering the characteristic of mobile node, we propose DTM-HoA and DTM-CoA respectively. These two mechanisms provide method to acquire IPv6 address and update configuration of VPN tunnel. We analyze the initial delay and communication delay of two mechanisms through theory and simulation. We prove that the DTM-CoA is prior to DTM-HoA. Attacker can initial security threat in the open Internet. Even we use encryption algorithm to protect VPN tunnel, the attacker still can attack at the LAN area. Further discussions solve the security problem and propose the secure dynamic tunneling mechanism (SDTM).Chapter VII is the conclusion of whole thesis. We also give the further work of next step.