Massive multiple-input multiple-output (MIMO) wireless system is increasingly becoming a vital factor in fifth-generation (5G) communication systems. It is attracting considerable interest due to improve range, spectral efficiency, and coverage as compared to the conventional MIMO systems. In massive MIMO systems, the maximum likelihood detector achieve the optimum performance but it has exponential complexity for realistic antenna configurations systems, Moreover, Linear detectors commonly suffer from a matrix inversion which is not hardware-friendly. There is an increase in the computational complexity associated with the unique benefits of the massive MIMO systems. The system might be classified as an ill-conditioned problem and hence, the signal cannot be detected. To reduce the data detection complexity, we investigate a linear detector based on the multiple search direction conjugate gradient (MSD-CG) in the massive MIMO uplink systems. Several theoretical iterative techniques that can be used to balance complexity and performance for massive MIMO detection have been proposed in the literature. These methods whose convergence rate for common applications is slow where there is a decrease in the base station to user antenna ratio. In this paper, the performance of the CG method has been advanced by a projection method that necessitates a search direction in each sub-domain instead of making all search directions conjugate to each other. In this regard, our results show that the proposed algorithm with realistic antenna configurations is superior to the existing methods in terms of computational complexity for large-scale MIMO systems.

大规模多输入多输出（MIMO）无线系统正日益成为第五代（5G）通信系统中的重要因素。与传统的MIMO系统相比，由于范围，频谱效率和覆盖范围的改善，它引起了人们的极大兴趣。在大规模MIMO系统中，最大似然检测器可实现最佳性能，但对于现实的天线配置系统却具有指数级的复杂性。此外，线性检测器通常会遭受矩阵反转，这对硬件不友好。与大规模MIMO系统的独特优势相关的计算复杂性不断增加。该系统可能被分类为病态问题，因此无法检测到信号。为了降低数据检测的复杂度，我们研究了大规模MIMO上行链路系统中基于多搜索方向共轭梯度（MSD-CG）的线性检测器。文献中提出了几种理论迭代技术，可用于平衡大规模MIMO检测的复杂性和性能。这些方法的通用应用的收敛速度很慢，其中基站与用户天线的比率有所降低。在本文中，通过投影方法提高了CG方法的性能，该方法需要在每个子域中搜索方向，而不是使所有搜索方向彼此共轭。在这方面，我们的结果表明，针对大规模MIMO系统，所提出的具有现实天线配置的算法在计算复杂度方面优于现有方法。