Research Of Modeling And Simulation In Wireless Mesh Networks

Wireless Mesh Network (WMN) was suggested firstly in1990s, and applied towireless access network in2002. It was considered to be the outcome of thecombination of mobile ad hoc networks and WLAN, developed on the basis of ad hocnetwork. In recent years WMN gradually becomes a research hotspot by virtue of itsown characteristics, which corresponds to future development direction of the network.The faster networks develop, the more complex for its scale and structure, and therelevant analyses for them become more and more difficult. Modeling (mathematicalanalysis) is used to simplify or idealize the model, suitable for a rough qualitativeestimate of the early project but complex for the overall analysis. Computer simulationsgenerally provide statistics for instance in the parameters of quantitative reference.Because it’s easy in dealing with more delicate model and global analysis, it is alwaysused for the improvement of systems. Combining the modeling and simulation, theperformance of network can be better reflected to provide evidence in the beginning ofnetwork strutting, with the accuracy and reliability of network designing improved, andunnecessary investment reduced in a certain degree.In this paper, first of all, the basic structure, features and key issues of WMN，thefeatures of OPNET are expounded. Secondly, the bearer service-based wireless meshnetwork simulation processes are established according to specific needs. Topology,traffic source, flow control, routing models and etc are desighed. The sub modelsinclude traffic source model, flow control model and routing model.In the following part, each sub model is established separately and the simulationperformance is studied with OPNET Modeler14.5. The characteristics of traffic sourcesare discussed in the taffic source model, especially the self-similarity, long-rangedependence and heavy-tailed feature that widespread in network flow. Besides, theON/OFF traffic source models are applied to simulate the self-similarity of network.The call admission control, traffic policing and shaping in network are detailedexplained in the flow control model, and the method of flow control in this paper isstudied. It is obtained through simulation analysis that packet loss rate is reduced,average link utilization improved, and business flow smoothed with flow control. Therouting model is confined to in the fifth chapter. For the sake of virtual hierarchicalmesh network structure advanced in this paper, a Virtual Hierarchical Hybrid Routing is raised, which applies link state routing algorithm in the reliable routing plan, and anglerouting based on geographical position in unreliable routing plane to improve theperformance degradation at the network caused by the link-state routing in poor linkstatus. Finally, the flow control and routing models are combined, and the performanceof the routing algorithm both in smooth flow and non-smooth flow also tested, thesimulation results reveal that the performance of VHHR routing protocol is close to thelink-state routing protocol in stationary traffic, however, the VHHR will switch to theangle route, rather than wait until the link state recovery in non-stationary, thus thebusiness can be transmited in time, delay and packet loss. rate reduced, so that thenetwork can operate normally.