| A wireless sensor network (WSN) is a self-organized distributed intelligent system comprising a large number of small-volume, low-power, ubiquitous sensor nodes that are capable of limited computing and communication capacity. It can be independent to complete the target task intelligently according to the surrounding environment. As wireless sensor networks are widely used in the field of smart healthcare, intelligent home, vehicular networking, efficient agriculture and so on, the requirements for network communication performance are increasing. According to the needs of different application scenarios, the fundamental issue in wireless sensor networks is how to choose optimal coverage schemes. The coverage schemes directly affect the energy-efficiency, communication-bandwidth and process-ability which are all limited in wireless sensor networks. They also determine the improvement of the QoS (Quality of Service) of sense, surveillance, and communication in wireless sensor networks.As one fundamental problem in wireless sensor networks, coverage control exploits node redundancy, node scheduling and density controlling for meeting sensing quality requirement. The network deployment scheme is assumed as a foundation for solving coverage problems, which significantly impact routing protocols, topology, coverage quality and network costs. From the perspective of energy efficiency, this paper studies several problems that involve minimum deployment and optimal coverage issues, including the area coverage, point target coverage, barrier coverage and so on. We propose efficient network deployment schemes to improve the network performance, and reduce the power consumption. The main contributions of our works can be summarized below:1) Research on wireless sensor networks and coverage issues is surveyed, while the challenges and development trend are analyzed. Several classic protocols and algorithms are analyzed and compared. The evaluation system and future research direction are put forward in detail. All of these make full preparations for future studies.2) Fast deploying, networking and information timely obtained in a target area are of great importance. To obtain the required coverage in heterogeneous wireless sensor networks (HWSNs), network designers initially need to determine how many sensor nodes should be deployed in the target area. Too many or too few nodes will limit the effectiveness of information collection and network maintenance. In order to obtain the needed network coverage and minimize the network cost, with the consideration of finite energy and sensing ranges in both sensors nodes and sink nodes, this paper applies the coverage process theory into the assignment of wireless sensor networks to improve the coverage ratio during a given time period. The optimal proportion of sensor nodes and sink nodes is derived through mathematical methods. The optimality design provides helpful configuration guidelines for the practical telemedicine monitor network deployment.3) Energy is one of the crucial factors in wireless sensor networks. The high energy-efficiency and low-power sensor nodes can effectively improve the network performance. This paper considers energy fairness problem in heterogeneous wireless sensor networks. To prevent the problem of’energy holes’occurrence, a nodes’deployment model similar to the cellular network is proposed, in which we deploy heterogeneous sensor nodes judiciously to conserve energy. This model can also ensure prolonged network lifetime. Based on this model, Game Theory is used to model the packet transmission among sensor nodes, and we get the Nash equilibrium by properly designing the measurement function. The proposed scheme not only makes the energy consumption of the network balanced, but also improves the network lifetime.4) Based on the target tracking algorithms of two-dimensional (2D) wireless sensor networks, the target tracking problem in three-dimensional (3D) wireless sensor networks with the consideration of additive and multiplicative noises (AMN) is investigated in this paper, which is different from most previous studies. Firstly, this paper put this target tracking problem as an optimization problem by the problem analysis. A Fisher information matrix is introduced to measure localization accuracy, and the tracking problem can be converted into an optimization problem at each time step. Then, according to the characteristics of the objective function, the number of variables and search space of this problem are reduced. Based on a standard Kalman filter, an optimal tracking algorithm is proposed to avoid the instability problem and maximize the tracking accuracy. The proposed optimal tracking algorithm owns a perfect tracking performance.5) Due to the 3D networks being closer to actual residential environment, coverage problems of 3D wireless sensor networks have practical significance. Different from the existing works on barrier coverage problems, this paper considers the exposure-path prevention problem by using the percolation theory in 3D WSNs, which can be implemented in intruder detecting applications. In this paper, to avoid the loose bounds of critical density, a bond percolation-based scheme is proposed to put the exposure-path problem into a 3D uniform lattice. Within this scheme, according to the mathematical theories of limit theory, probability theory and so on, tighter bonds of critical density for omnidirectional and directional sensor networks under random sensor deployment—a 3D Poisson process are derived. This research can be applied to the intruder detection, avoiding the loose the critical density of the continuous-percolation theory, and has very important significance in theory.To sum up, this paper mainly studies the energy-efficiency node deployment schemes and network coverage optimization problem, and put forward the corresponding solving strategies, which promotes the further theoretical research and practical applications of wireless sensor networks.
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