Research On Distributed Topology Control Algorithm For Optimizing Transmission Performance In Ad Hoc Networks

Ad hoc networks, without any support of fixed communication facilities, are comprised of a collection of wireless nodes communicating with each other. Ad hoc networks are self-organized and multi-hop wireless networks, which are very useful in such applicants where temporary, fast and on-demand communication needs to be built.It is undesirable in Ad hoc networks to have nodes transmit with its maximum power for two reasons. Firstly, the power required for transmitting quickly increases as the pair of sender and receiver become far away from each other, which ultimately affects network spatial reutilization and decreases the network lifetime. Secondly, the greater the power with which a node transmits, the greater the likelihood of the transmission interfering with other transmissions, which results in excessive signal interference and reduces traffic carrying capacity. However, lower transmitting power and more frequents failure of bottleneck nodes mean a more likely disconnected network.Research work on topology control has been seeking for well-performed algorithms to reduce the consumption of the nodes' transmission power, thereby saving nodes'energy, mitigating network collisions and improving traffic carrying capacity.Algorithm analysis and network simulation demonstrate that the interference between nodes is a key factor for network transmission capacity. A distributed topology control algorithm, bases on one spectacular feature of directional antenna is anti-interference, is advanced. The main contributions of this paper are as follows:(1) By analysis and comparison of several classical topology control algorithms, we study how nodes'density distribution and transmission range impact on the network topology. Simulation results show that the topology generated by the topology control algorithms should be possessed of less nodes'degree and narrow transmission range.(2) Through the EMA(External Module Access) interface of the network simulator-OPNET, a network platform for topology control is built to analyze the network transmission performance under the influence of different algorithms. Simulation results demonstrate that topology control is effective in Ad hoc networks, and the interference between nodes is one of the important factors which impact on the network transmission performances.(3) Advance a distributed topology control algorithm-SDTC(Steered beam Directional antenna based Topology Control algorithm). Theory proves that the algorithm is of strong connectivity and undirected property, and it is a distributed, sparse and degree of nodes bounded algorithm. In SDTC algorithm, each node needs only the location information of local neighbors. Experiment results show that the proposed algorithm significantly reduces the transmission power of nodes, and improves the network performances.