Research On Relay Cooperative Transmission Strategies Based On RF Energy Harvesting WSN

One of the key problems of 5G and B5G technologies is to guarantee reliable communication at low cost,low complexity and low power consumption,especially for applications including large-scale Io T and large-scale Wireless Sensor Networks（WSN）.In recent years,with the continuous development of sensor technology,WSN applications are becoming more and more widespread,including in industry and agriculture,weather detection,military defense,etc,but the limited energy of the sensor curbs the sustainable development of WSN.Therefore,prolonging the lifecycle of sensor nodes and maintaining their sensing performance is a major issue in WSN.Radio Frequency Energy Harvesting（RF-EH）technology^[1]has been continuously researched and analyzed to make the energy-constrained WSN self-sustaining operation.In order to further expand the system scope and solve the energy replenishment problem of WSN relay nodes,the relay collaboration system based on Simultaneous Wireless Information and Power Transfer（SWIPT）has been emerging.Therefore,how to effectively use the harvested energy and combine with wireless collaborative relay technology to expand the WSN system range and increase the system capacity is the focus of research for energy harvesting wireless sensor networks.The specific work of the dissertation is as follows:（1）In order to solve the difficult problem of short life cycle of WSN,a radio frequency power beacon（PB）-assisted wireless energy harvesting relay system model is constructed for the two-hop multi-relay transmission problem in energy harvesting wireless sensor networks,in which the relay nodes operate in full duplex mode.The relay node in this system model can obtain energy not only from the wireless PB in the system model,but also from the RF signal of the source node and the loop self-interference signal,and transmit the sensing information to the multi-antenna destination node with the help of these two parts of energy.Further,the destination node can use selection combining or maximal ratio combining strategy to receive the sensor information.In order to analyze the impact of key parameters on the system performance,the analytical expressions for the outage probability and throughput of the selection combining and maximal ratio combining strategies under the decode-and-forward approach are derived,respectively,and then a joint optimization of the time switching factor and power splitting factor with the goal of maximizing the throughput is proposed under the multiple constraints of guaranteeing the quality of service（Qo S）of the communication.Simulation results show that parameters such as PB transmit power,time switching factor,number of antennas,and power splitting factor have significant effects on the outage performance,and the proposed algorithm can result in a significant improvement in system throughput gain compared with the random relay selection algorithm and the max-min relay selection algorithm.（2）To address the network lifetime and energy replenishment problems of wireless sensor networks,a multi-relay system model of wireless energy harvesting wireless portable energy communication（SWIPT）assisted by radio frequency Power Beacon（PB）is constructed,and a relay selection strategy based on Adaptive Chaotic Particle Swarm Optimization（ACPSO）algorithm is proposed with the goal of optimizing system throughput.Where the relay node works in half-duplex operation and the model takes into account the direct link between the source and destination nodes.Under the characteristics of relay nodes with capturing source nodes and PB energy,the system throughput of the destination node under the maximal ratio combining technique is derived,and then the problem is modeled under multiple constraints to ensure the communication Qo S,and the 0-1NP hard problem is transformed into two coupled subproblems through mathematical transformation,namely,the external optimal relay selection problem and the internal joint optimization problem of time switching factor and power splitting factor,where the internal joint optimization problem is solved by the ACPSO algorithm.Simulation and numerical results show that each network parameter has a significant impact on the total system throughput performance and that the ACPSO algorithm can quickly and efficiently maximize the total system throughput.