Performance Analysis For Massive MIMO-OFDM Systems With Low-resolution ADCs

With the rapid development of Internet technology and multimedia applications,the demand for data traffic is becoming higher and higher,which requires the next generation wireless communication technology(5G)to have higher channel bandwidth and communication capacity.As one of the key technologies in 5 Q Massive Multiple-Input Multiple-Output(MIMO)technology has outstanding advantages in improving system spectrum efficiency and transmission reliability.However,in the process of implementing Massive MIMO systems,it will also face many challenges.Among them,the high computational complexity of signal processing and the high hardware cost and power consumption are two serious challenges.One of the effective techniques to solve the above problems is to reduce the resolution of analog-to-digital converters(ADCs)at the base station.In the above context,this paper will focus on these challenges for further research,and investigate the channel estimation,performance analysis and optimization for the massive MIMO systems with low-resolution ADCs.Firstly,the basic theory of massive MIMO-OFDM is studied.The basic model and transmission process are introduced and the channel characteristics are theoretically analyzed in this paper.At the same time,the low-resolution technology is analyzed theoretically,which provides an important theoretical basis for future research.Then,we investigate the achievable rate performance for the massive MIMO-OFDM system,where each antenna is equipped with low-resolution ADC,both the Maximum Ratio Combining(MRC)and the Zero Forcing(ZF)receiver are assumed to be employed.The closed-form expression for the uplink achievable rate is derived by using the Additive Quantization Noise Model(AQNM),which allows us to reform the nonlinear quantization function into a linear one.Based on analytical results,the factors affecting the performance of low-precision systems and their relations are studied.Then,we develop an energy consumption model to study the energy efficiency,the relationship between energy efficiency and spectral efficiency is discussed.Simulation results are presented to verify the analytical results,we illustrate that the performance loss of using low-resolution ADCs can be compensated by deploying more antennas at the base station.Finally,the channel estimation for the massive MIMO-OFDM systems with low-resolution ADCs is further discussed,and the Minimum Mean Squared Error(MMSE)algorithm is used with the orthogonal pilot sequences.Considering the MRC and ZF algorithms respectively,the approximate expressions of the uplink achievable rate based on the imperfect CSI are derived.Then the performance between the low-resolution quantization system and the conventional system with infinite resolution ADCs is compared,and the optimization problem is given.The result shows that the massive MIMO-OFDM systems with low-resolution ADCs can maintain a certain spectral efficiency by adjusting the quantizer precision and the number of base station antennas.Since the system complexity and hardware cost are reduced,it provides an effective method to deploy low-precision system in practice.