论文标题
在空间相关的通道上，RIS辅助的无细胞大型MIMO系统的上行链路性能
Uplink Performance of RIS-aided Cell-Free Massive MIMO System Over Spatially Correlated Channels
论文作者
论文摘要
我们考虑了一个实用的空间相关的可重构智能表面（RIS）辅助的无细胞（CF）大量多输入 - 型 - 元素输出（MMIMO）系统，具有多个Antenna接入点（APS），而不是空间相关的RICIAN褪色通道。采用最小平方误差（MMSE）通道估计器来估计聚合的RIS通道。然后，我们以最大比率（MR）和局部最小平方误差（L-MMSE）在AP处的上行频谱效率（SE）进行了研究，并获得了封闭形式的表达式以表征前者的性能。通过广泛的蒙特卡洛模拟验证了我们衍生的分析结果的准确性。我们的结果表明，增加RIS元素的数量始终是有益的，但是当RIS元素数量足够大时，回报率会减少。此外，在少数RIS元素下，AP天线数量对系统性能的影响更为明显，而RIS元素的空间相关性对系统性能产生了更严重的负面影响。
We consider a practical spatially correlated reconfigurable intelligent surface (RIS)-aided cell-free (CF) massive multiple-input-multiple-output (mMIMO) system with multi-antenna access points (APs) over spatially correlated Rician fading channels. The minimum mean square error (MMSE) channel estimator is adopted to estimate the aggregated RIS channels. Then, we investigate the uplink spectral efficiency (SE) with the maximum ratio (MR) and the local minimum mean squared error (L-MMSE) combining at the APs and obtain the closed-form expression for characterizing the performance of the former. The accuracy of our derived analytical results has been verified by extensive Monte-Carlo simulations. Our results show that increasing the number of RIS elements is always beneficial, but with diminishing returns when the number of RIS elements is sufficiently large. Furthermore, the effect of the number of AP antennas on system performance is more pronounced under a small number of RIS elements, while the spatial correlation of RIS elements imposes a more severe negative impact on the system performance than that of the AP antennas.
