Research On Survivable And Fault-tolerant Topology Control Algorithms In Ad Hoc Networks

Ad Hoc network is a temporary, multi-hop, centerless and autonomous system which is composed of a group of mobile terminals with wireless transmitters and receivers. The characteristics including the existence of critical points, dynamic nodes, poor safety, harsh living environments cause topology to change frequently over time. Therefore, Ad Hoc network raises a very high demand for survivability and fault tolerance. Topology control allows network to tolerate passively frequent topology changes by preserving redundant links and respond proactively to frequent topology changes by reconstructing topology, and thus improves network performance. As a result, the research on survivable and fault-tolerant topology control technology in Ad Hoc networks is of great significance.Combination of fault-tolerant topology control based on QoS and topology maintenance, a survivable and fault-tolerant topology control algorithm was proposed in Ad Hoc networks. The algorithm is mainly composed of three phases. In the stage of initial topology construction, the topology control algorithm based on the shortest path is adopted to select K disjoint paths from source node to destination node for unicast services, and the fault-tolerant topology control algorithm based on K-connectivity is adopted to select K disjoint paths from source node to destination nodes by constructing the shortest path network for multicast services. Finally, the K-connectivity initial network topology is constructed. In the stage of topology optimization, the algorithm deletes the links with the highest link efficiency indicator to construct temporary topology, and treats temporary topology meeting the conditions as a new initial network topology through detection process. The optimization process is carried out until an optimal network topology is obtained. In the stage of topology recovery, the algorithm collects local topology information around the critical points, and then uses the shortest path algorithm to recover the connectivity of link groups, and ultimataly recovers the connectivity of the local network by adding the least cost links.The network simulation software NS2 was adopted to evaluate the efficiency and invulnerability of the proposed algorithm. Simulation results show that the proposed algorithm can improve the quality of services, enhance the ability of survivability, fault tolerance and failure recovery, and thus optimize integral network performance, making the network survive continuously.