Research On Energy Efficiency Of Multi-user Large-scale MIMO System

As the key technology of 5G,large-scale MIMO technology can achieve both high spectral efficiency and high energy efficiency.With the doubling growth of energy consumption in wireless communication systems,more and more attention has been paid to improving energy efficiency in academia and industry.The key point is that the goal of maximizing system throughput or minimizing system power consumption gradually evolves into the goal of maximizing system energy efficiency.In this context,this paper will study the energy efficiency in large-scale MIMO systems in depth.This paper mainly considers multi-user large-scale MIMO system,including single cell MIMO model and relay-and-forward model.An energy efficiency resource allocation algorithm is proposed based on zero-forcing Linear Precoding technology.The energy efficiency function of MIMO system is established by combining the transmit power of users and the number of transmit antennas at the base station.The energy efficiency function is convex optimized to obtain the maximum energy efficiency.The optimal number of antennas and transmission power of users are obtained by MATLAB simulation.Among them,in the model of half-duplex MIMO amplify-and-forward relay system,considering three power scaling strategies: fixed relay transmission power,fixed user transmission power,fixed user transmission power and relay transmission power,the asymptotic reachability rates of the two schemes using maximum combining ratio and zero forcing reception under three different power scaling strategies are given.The simulation results show that zero forcing reception can achieve higher system spectral efficiency and energy efficiency than maximum combining ratio,and the number of optimal antennas obtained is relatively small.The optimal resource allocation algorithm is superior to three power scaling strategies in maximizing system energy efficiency.This paper also considers the relay-and-forward model in full duplex mode,which is mainly divided into amplification and decoding systems.At the same time,the asymptotic instantaneous rate and the influence of loop interference under three power scaling schemes are analyzed.In the dual-hop amplify-and-forward relay system,with the increase of transmission power,the spectral efficiency of the system increases continuously until it tends to a fixed value.Since the first hop is more important for the system performance gain than the second hop,it can be found that the spectrum efficiency is larger when the number of receiving antenna is bigger than transmittingantenna at the relay.According to the decode-and-forward theorem,when the downlink is stronger than the uplink,the spectrum efficiency of AF system is higher than that of DF system.Loop interference has a greater impact on the two systems.When the downlink is weaker than the uplink,the performance gap between the two systems is very small and is almost not affected by loop interference.Finally,it is found that the amplify-and-forward relay system can suppress the loop interference only under the second power scaling scheme,while the decode-and-forward system can control the loop interference well under the second and third schemes because of the isolation of the uplink and downlink.The three power reduction schemes essentially make the number of antennas at the relay large enough.The simulation shows that the large-scale antenna array at the relay can effectively suppress the loop interference caused by full duplex.The energy efficiency of AF and DF relay systems under the second power scaling scheme is almost the same,while AF systems under the first power scaling scheme have higher energy efficiency and DF systems under the third power scaling scheme performs better.