Albreem Mahmoud A, Alsharif Mohammed H, Kim Sunghwan
Department of Electronics and Communications Engineering, A'Sharqiyah University, Ibra 400, Oman.
Department of Electrical Engineering, College of Electronics and Information Engineering, Sejong University, 209 Neugdong-ro, Gwangjin-gu, Seoul 05006, Korea.
Entropy (Basel). 2020 Mar 28;22(4):388. doi: 10.3390/e22040388.
Massive multiple-input multiple-output (M-MIMO) is a substantial pillar in fifth generation (5G) mobile communication systems. Although the maximum likelihood (ML) detector attains the optimum performance, it has an exponential complexity. Linear detectors are one of the substitutions and they are comparatively simple to implement. Unfortunately, they sustain a considerable performance loss in high loaded systems. They also include a matrix inversion which is not hardware-friendly. In addition, if the channel matrix is singular or nearly singular, the system will be classified as an ill-conditioned and hence, the signal cannot be equalized. To defeat the inherent noise enhancement, iterative matrix inversion methods are used in the detectors' design where approximate matrix inversion is replacing the exact computation. In this paper, we study a linear detector based on iterative matrix inversion methods in realistic radio channels called QUAsi Deterministic RadIo channel GenerAtor (QuaDRiGa) package. Numerical results illustrate that the conjugate-gradient (CG) method is numerically robust and obtains the best performance with lowest number of multiplications. In the QuaDRiGA environment, iterative methods crave large n to obtain a pleasurable performance. This paper also shows that when the ratio between the user antennas and base station (BS) antennas ( β ) is close to 1, iterative matrix inversion methods are not attaining a good detector's performance.
大规模多输入多输出（M-MIMO）是第五代（5G）移动通信系统的重要支柱。尽管最大似然（ML）检测器能实现最优性能，但其复杂度呈指数级。线性检测器是替代方案之一，且实现起来相对简单。不幸的是，在高负载系统中它们会有相当大的性能损失。它们还包含矩阵求逆，这对硬件不太友好。此外，如果信道矩阵是奇异的或近似奇异的，系统将被归类为病态的，因此信号无法被均衡。为了克服固有的噪声增强问题，在检测器设计中使用了迭代矩阵求逆方法，其中用近似矩阵求逆代替精确计算。在本文中，我们研究了一种基于迭代矩阵求逆方法的线性检测器，该检测器用于名为准确定性无线信道生成器（QuaDRiGa）包的实际无线信道中。数值结果表明，共轭梯度（CG）方法在数值上是稳健的，并且以最少的乘法运算次数获得了最佳性能。在QuaDRiGA环境中，迭代方法需要大量的n才能获得良好的性能。本文还表明，当用户天线与基站（BS）天线的比例（β）接近1时，迭代矩阵求逆方法无法获得良好的检测器性能。
