Design And Simulation Of A Topology Control Algorithm For Ad Hoc Networks

Ad Hoc network is a novel form of network which is self-constructed, self-organized and self-managed without centralized administration or wired infrastructure. Because of its many advantages such as flexible networking, quick deployment and distributed control, Ad Hoc network has wide application in the military and civilian fields. However, limited resources, as well as wireless communications and node mobility make the performance of Ad hoc network closely bound up with its topology. Unreasonable network topology will reduce network capacity, increase packet transmission delay and weaken network robustness when faced by node failures. Hence, topology control is an effective measure of great significance to improve the overall performance of Ad Hoc networks.Computational geometry and power control methods were jointly considered to propose a distributed topology control algorithm. The algorithm has three phases, which are information collection, proximity graph generation and symmetry mechanism used to eliminate one-way links between each pair of nodes in neighborhood. In the first phase, every node is aware of local topology through directional information acquired by antennas in order to know local topology. In the second phase, nodes reduce their degree to simplify topology by computing local proximity graph, which is connected and energy utility optimized. In the third phase, symmetry mechanism is used to guarantee two-directional connectivity between nodes as well as global connectivity, and then nodes adjust their transmission power to control and optimize network topology with robustness.On the basis of theoretical analysis of the proposed topology control algorithm in detail, the network simulation software NS2 was adopted to evaluate network performance both in static and dynamic environment under topology control. Simulation results demonstrate the algorithm can optimize network topology and improve network-wide performances, such as saving nodes'energy to prolong their lives, reducing communication jamming and transmission delay to increase efficiency of wireless channels and throughput of networks on condition of network connectivity.