Performance Analysis Of Relay-aided SWIPT Networks

In wireless networks,the traditional way of powering wireless devices is battery power.With the application of more and more wireless devices in complex environments,the problem of battery replacement and the high cost of human management are becoming increasingly prominent.Wireless energy harvesting does not need to replace the battery frequently and can provide stable energy for the device,so it has attracted widespread attention.In simutanious wireless information and power transfer network,radio frequency signals transmit energy and transmit information.On the other hand,the long-distance transmission of information leads to the degradation of network quality.Cooperative relay technology can expand the network coverage,improve the quality of service and the reliability of data transmission.Simutanious wireless information and power transfer and cooperative relay technology can solve the problem of limited energy and long distance transmission in wireless networks.In simutanious wireless information and power transfer relay network,most of the existing researches assume that no matter how much energy the relay harvests,it can work normally,but the relay is affected by the circuit energy threshold and may not work properly due to insufficient energy,resulting in system outage.Amplify-and-forward(AF)and decode-and-forward(DF)are two common relay forwarding methods,so this paper considers the system performance in the radio frequency simutanious wireless information and power transfer relay network affected by the energy threshold of the relay circuit,the system performance is analyzed in amplify-and-forward and decode-and-forward modes respectively.The main work is as follows:(1)In amplify-and-forward protocol,for a dual-hop multi-relay network with constrained energy,the system performance is affected by the energy threshold of the relay circuit,and the closed form expressions of the system outage probability and throughput are derived in Rician fading channel.Monte Carlo simulation is used to verify the accuracy of the closed form expressions,and the effects of different parameters on the system performance are compared and analyzed in the two relay selection schemes with the shortest first hop distance and the shortest sum of two hops distance.The results show that outage probability decreases first and then increases,and the throughput increases first and then decreases with the increase of time switching factor;The larger the Rician factor,the smaller outage probability is and the larger throughput is.With the increase of the number of source antennas,outage probability decreases and throughput increases;The larger the relay energy threshold,the larger the probability of relay energy constraint is;Comparing the two relay selection schemes,it can be seen that the system performance when the shortest sum of two hops is selected is slightly better than the system performance when the shortest first hop is selected.(2)In decode-and-forward protocol,for a dual-hop multi-relay network with constrained energy,the system performance is affected by the energy threshold of the relay circuit,and finally the closed form expressions of the system outage probability and throughput are obtained in Rician fading channel.The accuracy of the closed form expression is verified by Monte Carlo method.The effect of different parameters on the system performance are compared and analyzed in the two relay selection schemes with the shortest first hop distance and the shortest sum of two hop distances.The results show that the larger the minimum required transmission rate,the larger system outage probability is.When the total transmitting power of the source node is small,the increase of the minimum required transmission rate,the system throughput decrease;When the total transmit power of the source node is large,the increase of minimum required transmission rate of the system,system throughput increase;Increasing the energy conversion efficiency of the system,system outage probability decrease and throughput increase;The system performance when the shortest sum of two hops is selected is slightly better than the system performance when the shortest first hop is selected.