Large scale multiuser multi-input multi-output (MU-MIMO) system is an emerging wireless technology, which can impart huge spectral efficiency, enhanced link reliability, and serves several users simultaneously in the same frequency–time resource. Pilot contamination (PC) is the major bottleneck in achieving the optimum performance of a multi-cell large MU-MIMO system. We propose a new multi-cell block diagonalization-QR-minimum mean square error (M-BD-QR-MMSE) precoding scheme to diminish the effects of pilot contamination in a multi-cell MIMO system. The reduced effects of Pilot contamination result in the enhancement of spectral efficiency for the multi-cell MU-MIMO system. The design of the proposed scheme utilizes block diagonalization (BD) in combination with MMSE precoding that obtains large null space using QR decomposition operation to reduce intercell and intracell interference much efficiently than conventional precoding schemes. The gain in spectral efficiency with the proposed scheme is enhanced through non-universal pilot reuse in contrast to single-cell schemes. Furthermore, the downlink spectral efficiency expression has been derived for a large scale MIMO system, and the same is computed using Monte Carlo simulations to analyze the results. The numerical results depict that the proposed M-BD-QR-MMSE provides a significant improvement in the spectral efficiency in comparison with traditional single-cell MMSE (S-MMSE), regularized zero-forcing (R-ZF), ZF, Maximum ratio transmission (MRT) and multi-cell MMSE (M-MMSE) schemes. The proposed precoding design provides the spectral enhancements of 32.19 and 50.13 bit/s/Hz/cell in comparison to conventional multi-cell MMSE and single-cell MMSE precoding schemes respectively.

大规模多用户多输入多输出（MU-MIMO）系统是一种新兴的无线技术，可以提供巨大的频谱效率，增强的链路可靠性，并在相同的频率 - 时间资源中同时为多个用户提供服务。导频污染 (PC) 是实现多小区大型 MU-MIMO 系统最佳性能的主要瓶颈。我们提出了一种新的多小区块对角化-QR-最小均方误差 (M-BD-QR-MMSE) 预编码方案，以减少多小区 MIMO 系统中导频污染的影响。导频污染的减少影响导致多小区 MU-MIMO 系统的频谱效率提高。所提出方案的设计利用块对角化 (BD) 结合 MMSE 预编码，使用 QR 分解操作获得大的零空间，比传统的预编码方案更有效地减少小区间和小区间干扰。与单小区方案相比，通过非通用导频重用增强了所提出方案的频谱效率增益。此外，已经为大规模MIMO系统导出了下行链路频谱效率表达式，并且使用蒙特卡罗模拟计算相同的表达式以分析结果。数值结果表明，与传统的单细胞 MMSE (S-MMSE)、正则化迫零 (R-ZF)、ZF、最大比率传输 (MRT) 和多小区 MMSE (M-MMSE) 方案。与传统的多小区 MMSE 和单小区 MMSE 预编码方案相比，所提出的预编码设计分别提供了 32.19 和 50.13 bit/s/Hz/cell 的频谱增强。