Research On Target Coverage In Wireless Sensor Network

Target coverage is a basic problem in wireless sensor networks. Its researches includes the monitoring quality of target coverage, how to schedule sensor nodes to cover targets in order to extend network lifetime. To maximize the network lifetime of target coverage, this paper has done the following researches on the target coverage problem in wireless sensor networks.1. Improving on the algorithm of disjoint set covers, this paper proposes a linear programming algorithm to solve the target coverage problem.Firstly, we divide operate time into time slices, in which a time slice is called to be a timeslot. In every timeslot, only a set cover is chosen to monitor the targets. A sensor node may be dispatched into several cover sets, which breaks the integer programming ideas and introduces the linear programming idea. Then, we design the network model in which the initial energies of sensor nodes are not completely unequal, deeply analyze the network model of target coverage, and propose a linear programming expression to describe the target coverage problem. Finally, proposed a linear programming algorithm to solve the target coverage problem. Furthermore, we prove the target coverage problem to be a NP-complete. All of these establish the theoretical foundation of the target coverage problem.2. To reduce the computational complexity, we proposed a centralized heuristic greedy optimum target coverage algorithm to solve the target coverage problem.The target coverage problem is a NP-completely problem. In practice, under the condition that sensor nodes'processing power, communicating capacity, energy supply is serious restricted, it is difficult for sink node to execute the linear programming algorithm. In order to reduce the computational complexity, we analyze the energy model of target coverage, present the concept of the key target and the prior coverage of key target. Moreover, we choose sensor with most energy utility as active sensor. In the end, we present a centralized heuristic greedy optimum target coverage algorithm. Measurement results show that the new algorithm could increase network lifetime and achieve more adaptability and stability. 3. Considering the distributed and self-organizing features of wireless, we proposed a distributed optimum algorithm for target coverage problem.Above the linear programming algorithm and the heuristic greedy optimum target coverage algorithm are centralized executed, in which sink node or base station must get all the information of the whole network and becomes the bottleneck of the whole network. Meanwhile, it would increase the network flow and increase the energy consumption for the information of the network management to be concentrated and dispatched. In order to overcome these shortcomings of the centralized algorithms, considering the distributed and self-organizing feature of wireless sensor networks, we design a distributed optimum algorithm for target coverage.Firstly, we put forward the local h-hop target coverage problem, and prove the feasibility of the 1-hop distributed algorithm. Then, on the basis of analyzing the energy model of the target coverage, we introduce the concept of the key target, and design the energy utility function of sensor node, and establish an adaptive adjustment mechanism of the waiting time.4. In view of the network model of wireless sensor networks with adjustable sensing ranges, we further proposed a linear programming algorithm to solve the target coverage problem with adjustable sensing ranges.Adjusting sensing range is an important approach to reduce energy consumption. In wireless sensor networks with adjustable sensing ranges, by adjusting its sensing range, sensor nodes reduce overlapping coverage, reduce energy consumption, and extend the network lifetime of the target coverage. At the same time, by adjusting its sensing ranges, energy consumption can be balanced between the targets, consequently to prolong the network lifetime of target coverage.Firstly, we analyze the target coverage problem with adjustable sensing ranges. Then we use linear programming expressions to describe the target coverage problem with adjustable sensing ranges, and propose an energy-efficient heuristic algorithm. Finally, we design simulation experiment experiments to evaluate the performance of our algorithm.5. Propose an Energy-Balance Heuristic Distributed Algorithm for Target Coverage with Adjustable Sensing Ranges. The target coverage problem with adjustable sensing ranges is NP-complete. In order to reduce the computational complexity, taking into account the dynamic topology, distributed, and self-organizing characteristics, we adopt a distributed algorithm to seek the network lifetime of target coverage in the local h-hop network, consequently the whole optimum solution is approached by local optimum solution. Finally, we propose an Energy-Balance Heuristic Distributed Algorithm for Target Coverage with Adjustable Sensing Ranges based on the energy balance and adaptively adjusting sensing ranges.