Research On Target Coverage Problem In Wireless Sensor Network

Coverage problem in wireless sensor network has been widely studied. Due to the low battery of sensors, how to schedule the sensors to maximize the lifetime of network is an important issue for the coverage problem. In this paper, we firstly discuss the algorithms for different kinds of coverage problems such as area coverage problem, target coverage problem, barrier coverage problem and so on.For the wireless sensor networks with unique sensing range, we designed a greedy target coverage algorithm named E-MSC that is based on residual energy of each sensor. Different from other target coverage algorithms like G-MSC, the algorithm E-MSC proposes a new contribution model for sensors in the wireless sensor network:not only considering the uncovered targets within the sensor's sensing range, but also considering the residual energy of each sensor. Besides the new contribution model, we adopt the strategy of selecting the sensors with the maximum contribution that can cover the "remote target" firstly. When the sensor's energy becomes smaller and smaller in E-MSC algorithm, the contribution of the sensor will become smaller and smaller in order to decrease the possibility of its death too early. Finally, we have done simulations of E-MSC algorithm. The results of simulations show that:Compared to the algorithm G-MSC, E-MSC can improve the network lifetime without any extra expense.For the wireless sensor networks with multiple sensing ranges, we study the target coverage problem with multiple sensing ranges in the wireless sensor network formed by random deployment, which has been proofed NP-Complete. For Centralized Greedy Heuristic algorithm (CGH) has many redundant sensors in each round, we propose an innovative centralized algorithm named ECGH in this paper. In order to maximize the lifetime of network, ECGH algorithm introduces a concept of "remote target", and adopts a strategy that adding the sensors which can cover the "remote target" to the working set with a high priority. ECGH overly depends on global information, so we propose a distributed algorithm named EDLGH that is based on Distributed and Localized Greedy Heuristic algorithm (DLGH). EDLGH algorithm only uses local information and designs a "redundant node-check-and-prune" mechanism to significantly reduce the appearance of redundant sensors in each round. Finally, we study the lifetime of ECGH and EDLGH by comparing them with existing CGH and DLGH. Simulation results show that ECGH and EDLGH each outperform better than CGH and DLGH.In order to solve the problem of how to guarantee the infomation sensed by the sensors be transimitted to the Sink, we study the connected target coverage problem in the wireless sensor network formed by random deployment. Because the problem is NP-Complete, we tranform it to Maximum Cover Tree problem (MCT), then propose a greedy connected target coverage algorithm ECTCG to sovle it. Based on the algorithm CWGC, the algorithm ECTCG assigns weights to sensors and edges in the network, then adopts the strategy that selecting the sensors with maximum weight that can cover the "remote target" firstly. Finally, we have done some simulations. The results of simulations show that: compared to the algorithm CWGC, ECTCG can imporve network lifetime without any extra expense.At the end of the paper, we conclude the paper, and then propose the feature study of the target coverage problem in wireless sensor networks.