Performance Analysis Of Spatially Correlated Massive MIMO With Hardware Impairments

Multiple-input multiple-output(MIMO) system with very large number of base station(BS)antennas has attained a lot of attention in recent years. Since, it improves the overall system capacity as well as Bit Error Rate(BER) by exploiting the advantages of high degrees of freedom and better spatial multiplexing. Performance analysis described in this thesis mainly concern with two serious challenges.Hardware Impairments: Implementation of large number of antennas on a BS expected to have low power consumption and low-budget radio frequency(RF) components which are prone to hardware impairments. Phase noise(PN), high power amplifier(HPA) nonlinearities, or in phase/quadrature-phase(I/Q) imbalance) are some reasons of introduction such impairments that can drastically effect the performance of large scale MIMO system.Various mitigation schemes are used to overcome the impact of hardware impairments but unfortunately, these schemes are not perfect enough such that a certain amount of residual RF hardware impairment always exists.Channel Correlations: Deployment of large number of antennas on both the transmit and the receive side introduces cross correlations between multiple transmission channels.The reason of such correlations is the narrow space between adjacent antenna elements. It is essential to consider such correlations during analyzing the system performance.In the design of practical cellular systems, the actual benefit of multi-antenna transmission is limited by a variety of factors such as hardware impairments and the correlation between multiple transmission channels. In this thesis, we design a new system model for MIMO system by taking transmit RF impairments into account and consider it as an additional distortion during transmission. We further define a spatially correlated channel model to investigate the impact of channel correlations on system capacity. Next a general capacity expression is derived to analyze the performance of massive MIMO in various environments. We further compare an ideal system with an impaired system under uncorrelated and correlated channels. The capacity of MIMO system under correlated channels is more affected by hardware impairments as compared to uncorrelated channels. We find that the impact of hardware impairments and channel correlations have different behavior at a specific range of SNR. Numerical results provide a significant insight of the system performance with variety of scenarios to achieve full advantage of large scale multi-antenna systems in a realistic system environment.