论文标题
相关通道上的RIS辅助多用户下行链路的低复杂联合波束成形
Low-complexity Joint Beamforming for RIS-Aided Multi-User Downlink over Correlated Channels
论文作者
论文摘要
本文考虑了可重构的智能表面（RIS）辅助多用户通信，其中使用RIS来协助基站（BS）为多个用户提供服务。由被动反射元件组成的RI可以通过调节反射元件的相移来操纵传入电磁波的反射方向。基于优化（AO）的方法通常用于确定RIS元素的相移。尽管基于AO的方法显示RI的显着增益，但由于从BS到RIS到用户的Cascade通道的耦合结构，复杂性很高。另外，RIS的次波长结构引入了可能引起用户强烈干扰的空间相关性。为了处理相关通道上严重的多用户干扰，我们考虑以前提出的自适应用户分组大规模输入和多输出（MIMO）系统，并提出了两种低复杂性波束形成设计方法，具体取决于是否考虑了分组结果。仿真结果证明了所提出的方法比没有用户分组的方法达到的高率。此外，所提出的方法可以与基于AO的方法相似，但复杂性较低。
This paper considers the reconfigurable intelligent surface (RIS)-assisted multi-user communications, where an RIS is used to assist the base station (BS) for serving multiple users. The RIS consisting of passive reflecting elements can manipulate the reflected direction of the incoming electromagnetic waves by adjusting the phase shifts of the reflecting elements. Alternating optimization (AO) based approach is commonly used to determine the phase shifts of the RIS elements. While AO-based approaches have shown significant gain of RIS, the complexity is quite high due to the coupled structure of the cascade channel from the BS through RIS to the user. In addition, the sub-wavelength structure of the RIS introduces spatial correlation that may cause strong interference to users. To handle severe multi-user interference over correlated channels, we consider adaptive user grouping previously proposed for massive mutli-input and multi-output (MIMO) systems and propose two low-complexity beamforming design methods, depending on whether the grouping result is taken into account. Simulation results demonstrate the superior sum rate achieved by the proposed methods than that without user grouping. Besides, the proposed methods can perform similarly to the AO-based approach but with much lower complexity.
