Research On RIS-Aided Wireless Energy-Harvesting Relay Communication Techniques

With the rapid development of wireless communication technology,the wide area deployment of wireless terminal devices has limited the energy acquisition of some devices.However,simultaneous wireless information and power transfer uses the method of transmitting information and energy simultaneously,which helps to alleviate the problem of power supply for terminal devices.Meanwhile,considering the limitations of limited transmission power on signal propagation and coverage,relay cooperative communication technology utilizes distributed nodes to form a virtual multi-input and multi-output network,improving the information transmission capability of wireless communication networks.In addition,Reconfigurable Intelligent Surface(RIS),with the passive beamforming of a large number of array units,can effectively improve the wireless transmission environment and is considered one of the key technologies in the future wireless communication field.In this context,this article delves into the RIS-aided simultaneous wireless information and power transfer relay communication technology,and its main research content and innovative points are as follows:Firstly,a RIS-aided wireless energy-harvesting relay network is considered,which consists of one source,one destination,one energy-harvesting relay and two RIS,where two RIS reflect signals from the source and the relay respectively to complete the transmission of information.Based on the system model,a dual RIS-assisted energy-harvesting relay transmission scheme is proposed,and the optimal power allocation ratio of the portable relay is given.Furthermore,the closed expression of the upper bound of the ergodic capacity of the proposed scheme is derived using Jensen’s inequality.The simulation results show that the ergodic capacity performance of the proposed scheme is significantly superior to traditional RIS-free and single RIS assisted transmission schemes.Secondly,a RIS-aided multiple energy-harvesting relay network is considered,which consists of one source,one destination,two RIS and multiple energy-harvesting relays based on DF strategy.The two RISs reflect signals from the source and the relay respectively.Based on the optimal power allocation ratio of each energy-harvesting relay to maximize the channel capacity,a dual RIS-assisted multiple energy-harvesting relay selection scheme is proposed.Using the Gaussian Chebyshev formula,the approximate expression of the outage probability of the proposed scheme is derived,and compared with the outage probability of the single RIS-assisted scheme.The simulation results show that the outage probability performance of the proposed scheme is significantly superior to the traditional single RIS-assisted multiple energy-harvesting relay selection scheme.At the same time,the more optional relays and RIS reflection units deployed in the network,the better the transmission outage performance of the network.Finally,a multi RIS-assisted multiple relay network is considered,which consists of one source,one destination,two RIS clusters with several RISs available and multiple relays.Therefore,a RISrelay joint selection scheme based on channel capacity maximization is proposed.Firstly,select a RIS which has the best channel gain within the first time slot from the RIS cluster that assists the transmission form source to the relay.Then,based on the transmission results of the first time slot,obtain the successfully decoded relay set.Finally,based on the maximization of channel capacity,select the optimal relay and the RIS which assists the transmission from the relay to the destination to participate in signal transmission,derived the outage probability expression of the proposed scheme.The simulation results show that the proposed RIS-relay joint selection scheme has significantly better outage probability performance than traditional relay selection schemes.At the same time,the more optional RIS and relay deployed,the lower the outage probability.