Multiuser precoding scheme and achievable rate analysis for massive MIMO system

Weiqiang Tan,Wen Liu,Zheng Shi,Lisheng Fan,Xi Yang,Wei Huang

doi:10.1186/s13638-018-1223-1

Abstract

We analyze the downlink multiuser precoding of massive multiple input multiple output (MIMO) system, where the base station (BS) has ideal channel state information (CSI) and adopts three types of different linear precoding schemes, i.e., maximum ratio transmission (MRT), zero-forcing (ZF), and minimum mean squared error (MMSE). Under a Rayleigh fading channel, we attain the exact expressions on the achievable rate for these three precoding schemes. Moreover, we provide several insights on the achievable rates and reveal the relation of the number of BS antennas, the number of users, and the input signal-to-noise ratio (SNR) with the achievable rates respectively. It is found in general that the achievable rate increases with the number of BS antennas and the input SNR. To be more specific, the MRT precoding scheme is much inferior to the ZF and MMSE precoding schemes and tends to be at a fixed rate at the high SNR case. On the contrary, the MRT precoding scheme outperforms ZF precoding schemes at the low SNR case. Moreover, the total achievable rate always does not increase with the number of users and the optimal number of users always exists for the ZF and MMSE precoding schemes.

Highlights

Massive multiple input multiple output (MIMO), well viewed as one of the important techniques for fifth generation (5G) wireless communication, has attracted a great deal of research interest in current years [1,2,3]
Our results indicate that the achievable rate increases with the number of base station (BS) antennas and the input signal-to-noise ratio (SNR) for different linear precoding and there exists the best number of users for ZF and minimum mean squared error (MMSE) precoding scheme
The achievable rate with MMSE precoding schemes is always better than that with ZF precoding schemes, and the achievable rate with maximum ratio transmission (MRT) scheme tends to have a fixed rate when the input SNR goes without bounds, which is a well predictor of the theoretical analysis in Corollary 2 due to the fact that the signal gain increases as the input SNR grows, while the inter-user interference increases

Summary

Introduction

Massive multiple input multiple output (MIMO), well viewed as one of the important techniques for fifth generation (5G) wireless communication, has attracted a great deal of research interest in current years [1,2,3]. We consider a general Rayleigh fading channel model and obtain the exact expressions on the achievable SE of massive MIMO systems for MRT, ZF, and MMSE precoding schemes by exploiting the theory of large dimensional random matrix and the probability density function (p.d.f.) of random variables. Our results indicate that the achievable rate increases with the number of BS antennas and the input SNR for different linear precoding and there exists the best number of users for ZF and MMSE precoding scheme. By utilizing different linear precoding schemes, we present the achievable ergodic rate of the centralized massive MIMO system

Channel model

Findings

Conclusions