The Research On Energy Consumption Models And Charging Strategies For Rechargeable Wireless Sensor Networks

The information world and the physic world are binded up together tightly through the rising and gradually matured technologies of wireless sensor networks. Wireless sensor networks have shed light on the promising future of modern signal and information processing techniques. However, the pervasive usage of wireless sensor networks also bring us new challenges at the mean time.The energy related problems are indensively considered in the research area of wireless sensor networks. The limited energy supply is a key issue which impedes the long-term operation of wireless sensor networks. The energy-aware data routing schemes, MAC layer protocols, power control strategies together with cross-layer optimization approaches have been proposed by researchers in order to prolong the lifetime of wireless sensor neworks. Recently, a breakthough in wireless energy transfer technique made by Kurs and his team in MIT paved the road for the research of energy replenishing issues in wireless sensor networks. If a sensor node can be charged by a wireless energy transfer device remotely in a proper way, the network might not be vulnerable to malfunctions stemming from insufficient energy supply. However, few effort has been endevoured into the study of wireless sensor networks with wireless energy transfer device. In this article, we focus on the modeling issues of rechargeable wireless sensor networks adopting wireless energy transfer technique. After studying these models, we propose a series of optimization problems successively. The working strategies for rechargeable sensor networks and wireless energy transfer device are also acquired simultaneously from solving these optimization problems. The main contributions of this article lie in the following three aspects:Firstly, the dynamic model of single-based rechargeable wireless sensor networks of static topology is proposed according to the comprehensively analysis of requirements which sensor nodes and wireless energy transfer device must comply with. In order to make the wireless energy transfer device stay at the service station as long as possible while keeping all sensor nodes above certain energy level, an optimization problem is formulated. This optimization problem is then transformed into a linear programming problem with the help of several theorems. The optimal travelling path and charging duration of wirelss energy transfer device as well as the dynamic date routing scheme of wireless sensor networks are obtained through solving this problem.Secondly, the dynamic model of single-based rechargeable wireless sensor networks of dynamic topology is proposed. The wireless energy transfer device works as a roaming data collector which gatheres data directly from sensor nodes being charged. The very sensor node renders as a temporary cluster head of local sensor nodes cluster. Since all sensor nodes would receive energy from the energy replenishing device, the cluster head node and the way of clustering are both supposed to be alterable, which causes the dynamic topology of this type of networks. The optimization problem raised in accordance with the dynamic topology must take into consideration the different requirements of distinct sensor nodes over different time instances. Solving this problem yields the dynamic clustering schemes of the sensor networks, and the corresponding working strategies for sensor nodes and energy replenishing device.At last, the model of multi-based rechargeable wireless sensor networks is proposed. Placing several base stations in a relativey huge sensing area will eventually reduce the overheads of transmitting data within the whole networks. Based on the results of the former two research, we introduce the concept of the index of sensor node activity, and form an optimization problem to maximize it. After solving this problem, we obtain the optimal dynamic and cyclic working strategies and power control tactics for wireless sensor networks and wireless energy transfer device.