Investigation On Power Splitting Methods For Wireless Energy-harvesting Relay Networks

In last few years,with leaping forward of wireless communication,a variety of terminal devices have appeared in our lives.These devices are popular because of their small size and convenient portability,since the battery capacity is limited,it cannot last for a long time.Therefore,how to provide sufficient energy for equipment in mobile wireless communication has became a great significance of researchers.The emergence of wireless energy-harvesting communication combining communication technology and energy technology provides a solution to this problem.It can complete the transmission of information and realize the collection and transmission of energy.This can not only deal with the problem that information cannot be stably and reliably transmitted due to energy shortage,but also save energy and conform the theme of green environmental protection communication.Based on this,this thesis studies the power splitting and security versus reliability in wireless energy-harvesting relay networks.The main research work and innovations are as follows:Firstly,this thesis study the optimization of multi-relay power splitting based on ergodic capacity maximization.This thesis proposes an optimal power splitting scheme,which maximizes the channel ergodic capacity from the source node to the destination node,and combines the one-dimensional search method to obtain the optimal power splitting factor,and then compares it with the channel ergodic capacity under the traditional equal power splitting scheme.The simulation results show that under the same number of relays,the performance of reliability under optimal power splitting scheme is better than the traditional equal power splitting scheme.And as the number of relays increases,the ergodic capacity of the system gradually increases,which indicates that increasing the number of relays can effectively increase the ergodic capacity of the system,improve system transmission reliability.Secondly,this thesis studies the joint optimization of relay selection and power splitting in energy-harvesting multi-relay network.We get the optimal power distribution factor according to the optimal power distribution scheme,then maximize the channel capacity and get the best relay node.Based on the maximum channel capacity,we can get the expressions of outage probability and eavesdropping probability,and the formula is simulated.The simulation results show that the relayoptimization and power allocation joint optimization scheme proposed in this thesis can reduce the outage probability and eavesdropping.And with the increase of the number of relays,the performance of security is getting better.In addition,the performance of security and reliability under optimal power splitting scheme is better than the traditional relay selection and equal power splitting scheme.Finally,this thesis analyzes the physical layer security in energy-harvesting multi-antenna relay network.In multi-antenna relay network,we can obtain the precoding matrix according to the criterion of maximizing the signal-to-noise ratio(SNR).We get the optimal energy distribution factor according to the optimal energy distribution scheme,then get the best relay node.Based on the maximum channel capacity,we can get the expressions of outage probability and eavesdropping probability,and the formula is simulated.The simulation results show that the outage probability and eavesdropping probability of the system decrease with the increase of the number of antennas,that is,the security performance of the system will become better with the increase of the number of antennas.And the system physical layer security performance under the optimal power allocation scheme is significantly better than the traditional equal power allocation scheme.