论文标题
局部部分零强度合并无细胞的大型MIMO系统
Local Partial Zero-Forcing Combining for Cell-Free Massive MIMO Systems
论文作者
论文摘要
与用户（UES）相比，无细胞的大规模多输入多输出（MIMO）比蜂窝技术更均匀的光谱效率（SE）。实现无细胞大量MIMO的好处的主要挑战是以可扩展的方式实现信号处理。在本文中，我们考虑可扩展的全型零强度（FZF），部分FZF（PFZF），保护性弱PFZF（PWPFZF）以及通过利用通道统计数据组合的局部正则化ZF（LRZF）。我们为FZF，PFZF和PWPFZF提供了上行链路SE的封闭形式表达式，并在独立的雷利褪色通道上结合了大规模褪色解码，考虑了通道估计误差和试点污染。此外，我们研究了试验序列的数量，每AP天线和AP的影响对性能的影响。数值结果表明LRZF提供了最高的SE。但是，当试验序列的数量较大并且每个AP的天线数量很少时，PWPFZF是可取的。原因是PWPFZF具有较低的计算复杂性，并且可以以封闭形式计算SE表达式。此外，我们研究了PWPFZF与分数功率控制的性能，数值结果表明，它可以提高UES的性能，并以可扩展的方式实现所有UES的均匀服务。
Cell-free massive multiple-input multiple-output (MIMO) provides more uniform spectral efficiency (SE) for users (UEs) than cellular technology. The main challenge to achieve the benefits of cell-free massive MIMO is to realize signal processing in a scalable way. In this paper, we consider scalable fullpilot zero-forcing (FZF), partial FZF (PFZF), protective weak PFZF (PWPFZF), and local regularized ZF (LRZF) combining by exploiting channel statistics. We derive closed-form expressions of the uplink SE for FZF, PFZF, and PWPFZF combining with large-scale fading decoding over independent Rayleigh fading channels, taking channel estimation errors and pilot contamination into account. Moreover, we investigate the impact of the number of pilot sequences, antennas per AP, and APs on the performance. Numerical results show that LRZF provides the highest SE. However, PWPFZF is preferable when the number of pilot sequences is large and the number of antennas per AP is small. The reason is that PWPFZF has lower computational complexity and the SE expression can be computed in closed-form. Furthermore, we investigate the performance of PWPFZF combining with fractional power control and the numerical results show that it improves the performance of weak UEs and realizes uniformly good service for all UEs in a scalable fashion.
