Research On Low Complexity Precoding Algorithm For Massive MIMO Systems

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 communication capacity.As one of the key technologies of 5G,MIMO(Multiple-Input Multiple-Output)technology has outstanding advantages in improving system spectrum efficiency and transmission reliability.However,in the process of implementing Massive MIMO systems,it faces serious inter-user interference problems.It is an effective way to solve inter-user interference to use precoding technology.But,it will also face many challenges to use precoding techniques for Massive MIMO systems.Among them,the high computational complexity of signal processing and the high hardware cost and power consumption are two serious challenges.In this paper,we will focus on these challenges for further research.Firstly,the basic theory of massive MIMO is studied.The basic model is introduced and the channel characteristics are theoretically analyzed in this paper.The upper bound of the capacity of the massive MIMO system is theoretically derived.The actual capacity is also simulated and analyzed.Secondly,the precoding technology in Massive MIMO systems equipped with highprecision digital-to-analog converters(DACs)is studied.The linear precoding technology is mainly studied.Aiming at the high computational complexity of traditional precoding algorithm,this paper studies the precoding algorithm based on iteration method,and proposes a precoding algorithm based on PCG(Preconditional Conjugate Gradient)iteration.The simulation results show that the proposed algorithm not only has low complexity,but also has high convergence.Finally,in order to reduce the hardware cost and power consumption of base station,the precoding technology in Massive MIMO system using 1-bit DAC for quantization is studied.Aiming at the disadvantage of traditional linear precoding in 1-bit scenario,the non-linear precoding algorithm is mainly studied.In this paper,a precoding algorithm of Neumann-AM(Neumann series expansion Alternating Minimization)is proposed.The simulation results show that the proposed algorithm not only guarantees the BER performance of quantized precoding,but also greatly reduces the computational complexity.