Research On Target Coverage Algorithm In Wireless Sensor Networks

With the development of sensor technology, computer networks, Micro Electro Mechanical System (MEMS) and singal processing technology, wireless sensor networks (WSN) become a major concern in research field. Generally, WSN consist of a large number of tiny sensors nodes with limited power supply which are randomly deployed in monitored area. The sensor nodes are capable of data gathering, data processing, wireless communication and self-organization, and finish complex monitor task by collaboration. The acquired data will send to sink node by multi-hop relay. The sink node has ability to process amount of data and send the data to futher region, so romote user can get the data. The features of WSN show that WSN can be deployed at severe environment and the place where people can not arrive.Coverage is the crucial and fundamental issue in the research of WSN, and has great influence on the performance and quality of services (QoS) of the networks. The thesis focuses on energy-efficient target coverage in WSN.Firstly, the thesis presents 0-1 sensing model and probabilistic sensing model, and give a viewpoint that energy of node can be saved by changing sensing radius. Baesd on probabilistic sensing model, an improved simulated annealing algorithm and an elastic net algorithm are proposed to find a sensing radius table of all sensor nodes under the expected coverage ratio. The experiments show that both of them can find sensing radius scheduling scheme and prolong the lifetime of the networks.Secondly, the thesis presents basic notion about connected coverage problem, and defines the problem of connected maximum lifetime set cover and the problem of connected maximum lifetime single target set cover. A GCH algorithm and a DCH algorithm are proposed to slove the two problem. GCH finds key sensor nodes to build a target set cvoer and set up connectivity by using DFS or BFS, while DCH builds connected set cover by finding sensing nodes and forwarding node. The simulations show that the two algorithms are feasible and effective.The general location scheme is not suitable for low-power and low-cost WSN, but most of coverage schemes are based on exact location. The thesis proposes a sink assisted location algorithm by absorbing the merit of DV-Hop and RSSI, which can obtain sensor nodes location information. Then, based on the location information, a coverage algorithm that covers a moving target are presented. The experiments show that algorithm is practicability for the WSN without location equipments that monitors moving target.Finally, aim at the problem that most of coverage algorithm relies on exact location information which is hard to obtain in real application of the network. The thesis presents a distributed and location-free sensor node coverage scheduling algorithm and proves that the randomly deployed WSN is a Possion point process, and draw conclusions that with the increase of density of sensor nodes and the increase of sensing range of sensor nodes, the lifetime of network can be prolonged. The algorithm does not rely on the location information of sensor nodes, and use a few messages of neighborhood to decide work status. The simulations show that the algorithm can decrease the quantity of working nodes under expected coverage intensity and can prolong the lifetime of network.