Research Of Routing And Channel Assignment In Cognitive Wireless Mesh Networks

With the rapid development of wireless communications technology, spectrum resources become scarce while the reality of low average utilization rate is becoming seriously. Cognitive Wireless Mesh Networks (CWMN/CogMesh) is the combination of Cognitive Radio technology which is using dynamic spectrum management to improve the spectrum utilization and Wireless Mesh Networks which is the most promising next generation wireless network technology, it can achieve heterogeneous wireless networks integration and broadband access. It is the potential core technology to build a next generation broadband mobile Internet. This thesis mainly concerns the combined routing and spectrum assignment technology of Cognitive Wireless Mesh Networks under the circumstance of two different spectrum sensing and sharing model: Overlay and Underlay, and also the routing security issue of Wireless Mesh Network in the cognitive environment are discussed. It is significant for building a safety, large capacity, high speed, wide coverage Wireless Mesh Networks.Firstly, the routing and channel assignment technology of Cognitive Wireless Mesh Networks in this thesis is using overlay model to share spectrum resources with authorized networks. With regard to the problems that channel which is available to cognitive nodes is dynamic and heterogeneous, and overhead and backoff delay by channel switching will affect network performance, Channel's Fitness Aware Routing (CFAR) for Cognitive Wireless Mesh Networks is proposed, it is based on shortest-cross flow least rule to select the end-to-end path, and channel switch is also been taken into consideration when spectrum resources are allocated. Simulation result shows that, CFAR can achieve preferably performance of end–to-end delay.Secondly, this thesis has researched the hyacinth model-based routing and channel allocation (HMRCA) strategy of Cognitive Wireless Mesh Networks, based on the analysis that Underlay spectrum sharing model of interference avoidance could more effectively improve spectrum utilization. With regard to the features of limited transmission power and dynamic available channel set, the construction of spectrum aware routing tree will integrate the information of cognitive mesh nodes location and available channel distribution situation, and adaptively allocate and update channel. The simulation result proves that HMRCA strategy can fully utilize available channel to improve network spectrum resources.Thirdly, with the growth of wireless network security threats and routing security problems in Cognitive Wireless Mesh Networks, security metric based routing and channel assignment (SMCAR) strategy is proposed. By quantifying the trust degree between nodes and the security in data transfer channel, the trust relationship between neighboring nodes can be established; by defining security metric as a proof to select a path, a safe end-to-end route can be established. Simulation result shows that SMCAR strategy could improve the safe delivery fraction of traffic flow.Finally, this thesis gives a description of extending NS2 node module to realize multi-channel multi-interface support and dynamic channel switching function, to meet the Cognitive Wireless Mesh Networks simulation environment. Also, this platform could support the research of the other similar network's routing and spectrum technology and performance simulation.