Spectral And Energy Efficiency Of Massive MIMO Systems With Channel Aging And Phase Noise

An immense growth in the number of associated wireless devices have been seen recently.Thus,future wireless systems have to gratify three main necessities:having a very high data throughput;simultaneously serving tremendous users;and having low latency.Massive multiple-input multiple-output(MIMO)technology,where base station(BS)equipped with a large number of antennas serves many active users in the identical time-frequency resource,can meet the above requirements,and hence,it has been a promising technology for next generations of wireless systems.In particular,with a simple power control scheme,massive MIMO can offer uniformly better service for all users.However,many challenges still exist for practical massive MIMO systems.In this thesis,we focus on the performance of massive MIMO with channel aging and phase noise.In the first part,we extract the spectral efficiency of the uplink massive MIMO systems taking into consideration a practical channel impairment called channel aging or aged channel state information(CSI).We study both maximum ratio combining(MRC)and zero forcing(ZF)receivers at the BS.We obtain tight lower bounds for both receivers on the spectral efficiency and present an effective way to evaluate the sum-rate of the system.Furthermore,we describe the effect of channel aging on the power scaling law.The spectral and energy efficiency tradeoff is also examined.We derive informative and useful power scaling laws.We show that the transmit power of each user can be scaled down by 1/√m(M be the number of BS antennas)to maintain a fixed rate,when M→∞.We have uncovered that aged CSI does not harm the power scaling law.We also conclude that aged CSI source in the lessening of sum-rate by dipping the effective signal-to-interference-and-noise ratio(SINR).The larger the doppler shift,the more prominent the reduction in spectral efficiency.For a doppler shift of αn = 0.5,the spectral efficiency decreases 25%compared with the one of perfect CSI.Lesser the value of normalized doppler shift,the greater the decrease in spectral efficiency.In the second part,we emphasis on the massive MIMO performance under phase noise impairments.We present a unique joint channel phase model that allows us to study massive MIMO systems with maximum ratio transmission(MRT)precoder underneath these practical situations by mean of deterministic equivalent of the sum-rate.The important outcome is that attenuation because of user mobility is exceeds than due to phase noise.We conclude that phase noise,being time dependent,contributes to channel aging.However,we provide that the combined effects of user mobility and phase noise do not lessen the power scaling law by 1/√M as previously been concluded in massive MIMO systems with imperfect CSI.Numerical results expose the influence of both effects in massive MIMO systems for various types of local oscillators(LOs).An interesting observation is that user mobility is more severe than the phase noise.Finally,we conclude that massive MIMO technology can achieve considerable performance even in time varying situations.