The Research And Application Of Wireless Power Relay In Wireless Sensor Network

In the application of wireless sensor network, battery capacity of sensor nodes is the most deadly constraints in a number of key factors. In the usage scenario of thousands of wireless sensor nodes to be arranged, for example, environmental monitoring and military applications, people can’t and impossible to replace the wireless sensor nodes that run out of battery power individually. Use energy harvesting or energy harvesting technology allows wireless sensor nodes acquire or capture energy from the environment, with the ability to add energy, so as to achieve the purpose of permanent life of wireless sensor nodes and unlimited use of wireless sensor networks. The sources of energy harvesting include:light, vibration or pressure, temperature, and other electromagnetic energy. Wherein the use of microwave energy to transmit and acquire energy is a new way that enable nodes to obtain energy wirelessly, and now wireless sensor nodes can work in the level of microwatt average power, so that using this non-traditional power to supply energy to them is feasible.The use of microwave to transfer and get energy involved in wireless power transfer (WPT) technology. Radio wave is the carrier of energy and information, therefore, the principle of wireless power transmission and wireless information transmission (WIT) is the same. In this paper we study to provide energy for wireless sensor nodes based on microwave’s far-field radiation pattern. Due to the presence of problems, such as the loss of electromagnetic energy and low efficiency of transmission during the transfer, we try to expand the energy’s transmission distance and increase efficiency by coming up with wireless power relay (WPR) in this paper, so as to ensure the energy supply of sensor nodes. The so-called wireless power relay is used to extend the distance of wireless power transfer device, similar to the microwave relay communication in wireless information transmission.In order to study the proposed problem about wireless power relay in wireless sensor networks, firstly this article outline the system model of WPR and the structure model of the relay itself, On the analog of wireless information transfer system using store and forwarding (SF) to enhance the destination node of the received signals, SF mode can also be used to improve the energy supply of the destination node in the WPR system. Then this paper discusses the specific application about WPR using SF mode to transmit energy, since by using SF mode to expand energy relay transmission distance there is energy loss, it is difficult for the relay node to provide energy to the destination node all the time in this way (unless sufficient short distance), So we apply it to time-sharing working sensor networks with only one source node and one destination node. Through simulation and theory analysis when the relay node transmission power is constant, the closer relative distance between the relay node and the destination node, the greater the instantaneous power of the destination node receives, but the shorter the time of the relay node providing energy for the destination node. Relay node’s transmission power needs to adjust suitably, according to its location and the specific working power and working time of the destination node, so as to make the WPR to achieve the optimal effect.Finally, this article apply the WPR to the wireless sensor networks with multiple source nodes and multiple destination nodes, and propose a protocol of WPR in time-sharing WSN under specific conditions and scenarios, and then analyze the affect for sensor nodes’ energy coverage rate and survival rate in the system before and after the introduction of the WPR. We find that after using the protocol of WPR it can really improve the sensor nodes’ energy coverage rate; We also find that the sensor nodes’ energy coverage rate decrease with the working time of relay providing power increasing; At last, Simulation results show that it can really increase the sensor nodes’ survival rate and the life cycle of WSN after using the protocol of WPR in sensor networks.