Research On Fault-tolerant Topology Control Algorithms For Ad Hoc Networks

Wireless Ad Hoc network, without any support of fixed communication facilities, is comprised of a collection of wireless nodes communicating with each other. Wireless Ad Hoc network is self-organized, which is very useful in such applications where temporary, fast communication needs to be built.In Ad Hoc network,it is undesirable of nodes transmitting with its maximum power for follow reasons. The energy consumption required for transmitting quickly increases due to its maximum power. What's more, the greater the power with which a node transmits, the greater the likelihood of interfering with other transmissions, which affects network spatial reutilization and reduces network carrying capacity.How to reduce network interference and increase network throughput is one of the main issues in ad hoc network reseach.The topology of Ad Hoc network is susceptible to dynamics for some reasons.First, nodes join and leave the network are recurring. Second, nodes are easily lapse because of its limited energy. Third, nodes interference and link failure are frequent due to wireless channel. The dynamic changes of topology make a great impact on network performance.such as network connectivity,energy consumption, network transmission performance. Therefore, Ad Hoc network needs to be proactive or passive, to respond to the frequent topology changes, how to ensure the survivability of Ad Hoc networks is also one of the main points in ad hoc network reseach.The survivability of network and better transmission performance should be provided by Ad Hoc network.Research work on fault tolerant topology control has been seeking for well-performed algorithms, under the premise of ensuring the network survivability, to construct appropriate network topology, thereby reducing nodes energy consumption, mitigating network collisions and improving network carrying performance. The main works of this paper are as follows:(1) By analysis of the characteristics of wireless Ad Hoc networks, we study the significance of fault-tolerant topology control and research issues. By comparison of several representative proactive fault-tolerant topology control algorithms and three representative passive fault-tolerant topology control algorithms, we obtain the two types of algorithm weaknesses and the issues of this paper. (2) Topology control without fault tolerance will degrade the reliability of Ad Hoc networks, and will be not suitable for dynamics changes of network topology. In this paper.we propose a new strategy which can increase maintenance function for topology control algorithms based on nodes'position.Theoretical analysis and experimental results shows that the new strategy can efficiently maintain the network connectivity and guarantee the topology of best performances.(3) Most of passive fault-tolerant topology control algorithms are overly concerned on the network survivability, and ignores the issues whether the transmission performance of networks meets the application of QoS requirements;Its topology generated can not optimize interfere mostly. In this paper, a fault-tolerant topology control algorithm of QoS guarantee, referred to as the AIFT, is proposed, the new algorithm can generate K connected topology, and optimize interference furthest.The simulation results show that AIFT decreases interference and improves the throughput capacity of network.(4) In the interest of adding the function of topology control to network protocol,we revise OPNET network simulator, add processing module for topology control to the wireless MAC protocol and verify its feasibility by experiments.