Research On Deployment And Network Life In Wireless Sensor Network Coverage

Since the 70 s of last century, recent advances in sensor technologies, wireless communications, and micro-electro-mechanical systems(MEMS) have greatly promoted the emergence and development of wireless sensor networks(WSNs). Wireless sensor networks have received swift evolution, which benefits from the features of low cost, multi-functional,and self-organization. In wireless sensor networks, in order to avoid the sensor energy depletion or external damage and can’t continue to work, the number of sensors deployed is far more than the quantity to achieve full coverage. It is crucial to design a coverage algorithm while guarantees the quality of network coverage which reducing the number of working sensors.Sensors have limited energy, it is difficult to replace or recharge their batteries, keeping all the nodes on all the time could deplete their energy quickly. Hence, we adopt the duty-cycled mode in this work so as to save energy and extend the network lifetime. To be specific, the nodes are divided into a number of subsets, called cover sets, where each cover set is capable of covering all the monitored tasks. Coverage is one of the most fundamental problems in a wireless sensor network, and is used as an important measurement of the quality of service(Qo S) of wireless sensor networks. Therefore, studying the coverage problem has both theoretical significance and practical values.Based on the analysis and summary of the existing literatures, this thesis addresses two problems: efficient deployment and network lifetime. For the efficient deployment problems,this paper proposes k-perimeter coverage evaluation and deployment schemes. The former aims to evaluate the coverage degree of the monitored area, while the latter aims to deploy additional sensors inside the monitored area to meet the application requirements without affecting the initial deployment. For the coverage evaluation problem, we propose a k-perimeter coverage evaluation scheme(termed as k-PCE). Based on our proposed k-PCE scheme, a greedy k-perimeter coverage rate deployment scheme(termed as k-PCRD) is proposed. We also propose an improved version of k-PCRD(termed as k-IPCRD) so as to further reduce the number of redundant sensors. We prove that the proposed schemes outperform a few mainstream schemes in terms of time complexity.For the network lifetime problem, the paper presents a Centralized Connected Target k-Coverage algorithm(HCCTCk) and a Distributed Connected Target k-Coverage algorithm(HDCTCk) so as to generate connected cover sets for energy efficient connectivity and coverage maintenance in heterogeneous wireless sensor networks(HWSN). Both algorithms aim atachieving minimum connected target k-coverage, where each target in the monitored region is covered by at least k active sensor nodes. In addition, these two algorithms strive to minimize the total number of active sensor nodes and guarantee that each sensor node is connected to a sink such that the sensed data can be forwarded to the sink. Sensor nodes selection strategy is based on the sensing capabilities, remaining battery life and the case of targets coverage. Finally,Theoretical analysis shows that connected cover set generated by the proposed algorithm can fully cover all targets, and the resulted network is connected. At the same time, the simulation verifies the theoretical analysis. The fifth chapter is a summary of the article and future prospects.