Downlink Analysis Of MMIMO Relaying Systems With Low-resolution ADCs

With the increase of various smart devices and terminal products,the data of mobile communication has increased exponentially,making 4G(the 4th generation mobile communication)unable to meet the needs of society.The fifth-generation mobile communication technology is proposed,enabling a large number of mobile terminals to maintain high-quality communications at the same time.As one of the most important technologies of 5G,the massive multiple-input multipleoutput technology uses a sufficiently large antenna array to increase the spatial multiplexing and thus increase the transmission rate.On this basis,the relay and Massive MIMO are combined to obtain the mMIMO relay technology,which can improve the communication quality and effectively expand the communication coverage.Low-resolution ADCs is widely used because it can reduce the hardware cost brought by large-scale antenna arrays.This paper mainly studies the impact of lowresolution ADCs on the downlink of mMIMO relay system.The specific innovative research work is as follows:(1)For the downlink of massive MIMO relay system with low-resolution ADCs,the signal transmission process of this system is processed under the assumption that the base station and the relay have perfect channel state information.Since most of the previous researches are based on Rayleigh fading channels,Rician fading channels with line-of-sight components are more suitable for 5G practical application scenarios.Therefore,this article derived the closed sum rate expression of the downlink under the Rician fading channel and other channel fading models by processing the Rician factor.(2)In the actual communication process,it is difficult for the base station and the relay to have perfect channel state information.That is to say,it is impossible to know the specific channel coefficients in advance.Therefore,this article studied the system downlink based on low-resolution ADCs under imperfect channel state information.This chapter uses the minimum mean square error estimator to estimate channel matrixes and derives the expression of sum rate under imperfect CSI.The simulation results show that there is a trade-off between the number of antennas and the quantization accuracy when the system maintains good performance,which proves that lowresolution quantization is an effective solution to the problem of high cost and power consumption of mMIMO.(3)The fifth chapter of this paper studies the comprehensive performance of the downlink of a massive MIMO relay system with low-resolution ADCs.First,when the number of antennas tends to infinity,the sum rate of the system is analyzed asymptotically.The results show that when the number of antennas approaches infinity,the downlink sum rate of the system is mainly related to the number of relay antennas,the quantization gain and the number of users.After that,under certain assumptions,the power scaling law is proposed on the basis of the derivation of the third chapter.In the simulation part,the system capacity of downlink based on low-resolution ADCs under perfect and imperfect CSI is analyzed and compared.