Research On Key Techniques Of Network Mobility Supportment

Although network mobility (NEMO) technologies can provide continuous network connections for a network composed of multiple nodes, the existing network mobility basic support protocol is still faced with various problems in route optimization of nested mobile networks, single point of failure and the performance bottleneck of mobile routers, and handover performance during network movements. Current related research is still lack of comprehensiveness, compatibility and high performace. These problems seriously affect the application and further development of network mobility technologies.To solve the above problems of network mobility, this thesis, while remaining as compatible with basic mobile protocols as possible, tries to improve network mobility technologies through effort in route optimization of nested mobile networks, multihomed communication and seamless handover of mobile networks. The contributions of this thesis are included in the following works:1. While being able to expand the communication coverage, the nested structure of mobile networks will cause serious routing problems. To improve the compatibility, deployability and overheads of existing route optimization schemes, this thesis proposes a new route optimization method for nested mobile networks named NMNRO, which advertises the same foreign network prefix within the nested mobile networks by expanding neighbor discovery protocol. By using the care-of address configured by this prefix, NMNRO updates the neighbor cache of access routers and the routing table of mobile routers, and then performs correspondent registration to achieve route optimization. This method provides a relatively complete route optimization solution for nested mobile networks. While reducing overheads, NMNRO has maintained sound deoployability and compatibility. Experiment results indicate that NMNRO has lower handover delay and higher effective throughput, and these benefits become even more evident as the number of nested layers of mobile networks grows.2. To address the single point of failure and performance bottleneck on mobile routers in mobile networks, this thesis proposes MM-NEMO, a multihoming method that is applicable to hybrid multihoming scenarios involving multiple routers and multiple interfaces on mobile networks. By defining the maintenance and exchange methods for attributes of egress interfaces on mobile routers, MM-NEMO enables attributes of all egress interfaces of the mobile network to be stored in each mobile router in a distributed manner. Then, mobile routers use the comentropy-based multiple attribute decision making algorithm to perform the selection of the optimal interface for the communication of internal nodes of mobile network. While being able to solve the single point of failure on mobile routers caused by various reasons, MM-NEMO is applicable to multi-router, multi-interface and hybrid multihoming scenarios. The simulation results show that the interface selection of MM-NEMO can be based on both users’requirements and the attributes of multiple interfaces to facilitate high throughput in mobile network, load sharing, and avoid the performance bottleneck of mobile routers.3. To deal with the high packet loss rate and delay during mobile network handover, this thesis proposes IF-NEMO, a seamless handover solution for mobile networks, which focuses on the optimization of the signaling process under the predictive mode. In IF-NEMO, pre-handover procedures like address configuration and pre-registration are performed through the access router. In this way, the pre-handover delay under the predictive mode in the fast-handover optimization mechanism is reduced, and the success rate of the predictive mode during fast network movement is improved. IF-NEMO is able to significantly cut down on the pre-handover delay and signaling overheads while keeping the handover delay at a low level. Experiment results suggest that IF-NEMO still can perform the handover procedures of predictive mode during fast movement.Based on the research in the three aspects described above and according to the sequence of network movements, this thesis designs an all-in-one method O-NEMO that is able to provide functions of seamless handover, route optimization and multihomed communication for mobile networks. Experiment results show that O-NEMO, as an ideal optimization solution for network mobility technologies, plays a positive role during different stages of network movement by improving the handover performance, routing performance and throughput of mobile networks.