Performance Analysis And Research On Transmission Technology For Massive MIMO Systems In B5G Communication

With the rapid development of artificial intelligence,Internet of Things and other emerging technologies,the ever-increasing growth of communication connected devices has caused an explosive growth of traffic throughput.In order to further meet the requirements of high data rate,reliability and traffic demands in the future mobile communication scenarios.As one of the core technologies of the fifth-generation mobile communication(5G),the massive multiple-input multiple-output(MIMO)technology has attracted a lot of research interest and gradually made their way into mainstream 5G communication systems.Massive MIMO technology takes full advantage of the spatial freedom brought by the extensive number of antenna arrays at both receive and transmit ends of the base station.Thus,it can improve the performance of the communication systems significantly without increasing additional power and bandwidth,and the spectral and energy efficiencies are dramatically increased.However,for beyond 5G(B5G)network which requires higher quality of service,there are still many problems which are yet to be solved in theoretical analysis and practical application of massive MIMO technology.This thesis focuses on four mainstream massive MIMO systems for B5 G mobile communication: distributed massive MIMO(DM-MIMO)system,one-bit massive MIMO system,massive MIMO relaying system with imperfect hardware and full-duplex(FD)cell-free massive MIMO system with coarse analog-to-digital converters/digital-to-analog converters(ADCs/DACs).Based on the in-depth analysis of the spectral and energy efficiencies of above-mentioned four types of systems,the massive MIMO technology for B5 G is better perfected.It also provides abundant theoretical basis and technical support for the engineering design and deployment of systems.The main research contents of this thesis are as follows:(1)We investigate the spectral efficiency(SE)of a multicell downlink(DL)DM-MIMO system with pilot contamination operating over Rician fading channels.Firstly,when the remote antenna unit(RAU)utilizes the minimum mean square error(MMSE)estimation scheme to obtain non-ideal channel state information(CSI),we explore maximum ratio transmission(MRT)and line-of-sight(Lo S)component based equal gain transmission(Lo S-EGT)under non-ideal CSI.The tractable,but accurate closed-form expressions for the lower bounds of the achievable rate of the DM-MIMO system are derived.Based on the obtained closed-form expressions,various power scaling laws concerning DL data transmit power and pilot transmit power are analyzed in detail,as well as the impact of key parameters on system performance.Finally,numerical results show that employing the Lo S-EGT processing can obtain the better SE than the MRT processing for DM-MIMO systems when having a large number of RAU antennas and stronger Lo S component.Finally,the simulation results further show that when the number of all antennas for RAUs is fixed,the better SE performance can be obtained with more RAUs.(2)We study one-bit massive MIMO systems with imperfect radio frequency(RF)chains over Rician fading channels in B5 G networks.Firstly,we accomplish the linear minimum mean square error(LMMSE)channel estimation by virtue of the Bussgang decomposition theory.Furthermore,the approximate achievable rate expressions are derived in closed-form for the scenarios with ideal and non-ideal CSI when the base station(BS)performs the maximum ratio combination(MRC)detection scheme.Then,for the case of finite and infinite number of users,the scaling laws for transmit powers and RF hardware impairments are established based on the obtained closed-form expressions.Besides,it is also found that the different relationship between the large number of users and BS antennas can influence the results of the power scaling laws.Finally,the closed-form expression of energy efficiency(EE)is derived based on the established power consumption model.Numerical results reveal that the moderate number of BS antennas can contribute to better EE.(3)We consider a massive MIMO relaying system with imperfect RF chains and coarse ADCs/DACs.Firstly,the LMMSE channel estimation is accomplished when the relay performs the MRC/MRT schemes.The accurate and approximate achievable rate expressions are derived in closed-form based on the obtained non-ideal CSI.We also evaluate the impacts of critical design parameters on the SE.Moreover,scaling laws for transmit powers and RF hardware impairments are established based on the obtained closed-form expressions when the number of antennas at the relay grows infinity.Besides,the power allocation algorithm for maximizing the SE is proposed.Finally,the closed-form expression of EE is derived based on the established power consumption model.Numerical results show that,in the large-scale antennas regime,the presented power allocation strategy can provide about 90% rate improvement for the case of using 3-bit ADCs/DACs.Moreover,from the point of view of sum achievable rate optimization,employing low-quality RF hardware at the receive and transmit ends of the relay and coarse ADCs with low quantization bit at the receive end of the relay can significantly improve the system’s sum achievable rate.(4)We explore a FD cell-free massive MIMO network equipped with coarse ADCs/DACs at the access point(AP)over Rician fading channels for B5 G communication.Firstly,we suppose that the MMSE scheme is applied to estimate CSI when the AP performs the MRC/MRT schemes.The accurate sum achievable rate expressions for both uplink(UL)and DL are obtained in closed-form for the case of non-ideal CSI,respectively.Then,the expressions of EE for UL and DL can be obtained in closed-form based on the established power dissipation model.Finally,the numerical results show that when the total number of quantization bits of coarse ADCs/DACs at the receive and transmit ends of APs is fixed,employing higher-precision ADCs at the receive end of APs and coarse DACs at the transmit end of APs can notably improve the sum achievable rate for UL and DL of FD cell-free massive MIMO systems.In addition,the simulation results also illustrate that deploying the5-bit and 3-bit ADCs/DACs for UL and DL can obtain the maximum EE.