Research On Fault-Tolerant Connectivity And Network Coverage Optimization In Wireless Sensor Networks

Wireless sensor network is a self-organized network system which composed of vast micro sensors,and the sensors communicate with each other in wireless way.The efficient network connectivity and coverage to the deployed area is the basic preconditions of the network function.However,sensors may fail due to various reasons,such as environment change and hardware fault,to affect the network connectivity.As one of the most important parameters of QOS,the network coverage problems should also be ensured and optimized.Aiming at the fault-tolerant connectivity and coverage optimization problems,this paper has done some researches.The main contributions are as follow:1.The arbitrary single node failure problem is studied and the recovery algorithm based on cooperative communication is proposed.The algorithm utilizes the cooperative communication between the involved nodes to rebuild the communication path and recover the network connectivity.In order to overcome the shortness of cooperative communication,the algorithm which uses node mobility as a secondary solution is proposed.On the premise of network connectivity restoration,the energy consumption of the recovery process is minimized and the network performance is improved.2.Aiming at the problems of arbitrary multiple node failure,the restoration algorithm based on cooperative communication and node mobility is proposed.The algorithm divides the deployed area into small grids firstly,then the complicated multiple node failure problems are broken up into multiple single node failure problems.The node failure in each grid is restored by the previous algorithm that based on the cooperative communication and node mobility.The algorithm could minimize the energy consumption of the recovery process while restoring the broken network connectivity caused by arbitrary multiple node failures.3.In order to cover all the targets in the monitor area with minimum number of sensor nodes in the directional sensor networks,the distributed coverage optimization strategy based on clustering is proposed.The nodes are clustered according to some rules,then each cluster head will handle the optimized cover set selection in each cluster to achieve the selection of sensing sector cover set of all the targets.At last,the network performance and lifetime are improved by renewing the cluster heads periodically.4.Considering the targets connected coverage problem in directional sensor networks,the strategy which combines relay and sensor nodes deployment is proposed.To obtain a connected network,minimum number of relays are utilized to connect the targets and sink firstly.Then a certain number of sensors will be deployed around each target,the sensors will be clustered regarding the adjacent relay which is located at the position of each target as the cluster head.Upon working in turns by each cover set in every cluster,the network will maintain a longer cover time of all the targets and the network performance will be improved.5.Given an overall consideration of the fault-tolerant topology and coverage optimization problem in heterogeneous directional sensor networks with multiple sinks,the fault-tolerant connected coverage strategy is proposed.The strategy ensures every node find k-vertex disjoint path to sinks firstly,then each node will determine its working direction according to some distributed coverage optimization rules and form the cover set of the whole network.At last,upon running the distributed coverage optimization rules periodically and using the multiple communication paths reasonably,the network lifetime is extended and performance of the network is enhanced.