| As one of the cores of future wireless communications,Massive MIMO(Multiple-Input Multiple-Output)technology has great advantages in transmission security,communication network rate,and spectral efficiency.Among which spectrum efficiency is one of the important indexes to measure the performance of Massive MIMO system.However,with the increase of the number of system antennas,the hardware overhead will gradually increase.In order to reduce the cost of hardware,imperfect hardware is usually used.Therefore,how to maintain the high spectral efficiency of the system when hardware impairment has become the current research focus.This thesis focuses on the selection of high spectral efficiency in Massive MIMO systems and the impact of hardware impairment on the system spectral efficiency.Firstly,for the M-MMSE(Multicell Minimum Mean-Squared Error)and several common receive combinations/precoding schemes,the average and spectrum efficiency and performance of the system are analyzed in the uplink and downlink respectively.Comparing the complexity of these several receive combination/precoding schemes,M-MMSE,RZF(Regular Zero-Forming)and MR(MaximRatio)are selected schemes that compromise between high spectral efficiency and low complexity;Secondly,for the downlink of massive MIMO system,under the condition of non-ideal channel,through beamforming design and corresponding optimization algorithm,the receiver impairment and transmitter impairment of massive MIMO system are studied respectively.The simulation results show that considering receiver impairment or transmitter impairment is more robust than not considering impairment under non-ideal channel conditions;Thirdly,in Massive MIMO system uplink and downlink with actual number of antennas,combined with the model of transmitter impairment and receiver impairment in the second part and the receive combination/precoding schemes selected in the first part,the effect of hardware impairment on uplink and downlink spectrum efficiency is studied.Simulation results show that the smaller the hardware impairment,the higher the achievable and spectral efficiency of the system,and the greater the effect of hardware impairment on downlink spectrum efficiency than uplink. |
