Research On Ad Hoc Networks Taking Account Of Obstacles

In order to meet the demands of packet latency as well as communication and computation overhead, this thesis solves real world problems involving obstacles in wireless ad hoc networks. In general, obstacles in ad hoc networks may cause the following problems. On the one hand, ad hoc networks may be disconnected. Thus, the whole network can not be covered by the backbone networks. On the other hand, while two nodes are within wireless range of each other, they may be restrained from communicating directly due to physical obstacles. Eventually, routing scheme may end in failure. A real mobility model is described, and then a new solution is proposed for backbone network construction and routing protocol design. The performance evaluation is achieved by simulations in the end.Firstly, a truer mobility model called OCMM is put forward for the disconnected character. This model is designed in consideration of the presentation of obstacles, the setup of standby nodes and the movement patterns of the network nodes. In order to guarantee network connectivity, both centralized and distributed designs are adopted to place the minimum number of standby nodes in appropriate places.Secondly, two constructed algorithms are designed for backbone networks in ad hoc network with obstacle. For the virtual backbone networks, standby nodes are setup using centralized method and a new clustering algorithm OCA is described. By simulations, OCA algorithm is proved high performance through comparing with the Lowest-ID and the Highest-Degree heuristics in terms of the topological connectivity, the number of clusters and reaffiliation frequency. For the mobile backbone networks, standby nodes are setup using distributed method and a new algorithm OCDS is proposed. The selection of dominating nodes, the deletion of redundant dominating nodes and the construction of connected graph are designed in detail, and then a simulation example is described to explain the process.Finally, a position based routing called VTBR is designed for ad hoc networks with voids. It achieves its goal by combining the proactive and reactive routing. The performance comparison between VTBR and traditional position based routing protocols shows that VTBR algorithm has a much higher packet delivery success rate and a shorter average path length.