HyRIS: Hybrid Precoder based Reconfigurable Intelligent Surface Assisted Wireless Networks

在过去的几年里，多输入多输出（MIMO）技术已经获得了巨大的吸引力，特别是对于毫米波频率的通信。特别地，毫米波通信需要定向传输，这可以通过适当的预编码器设计来实现。考虑到预编码器设计在这样一个系统中的重要性，以及可重构智能表面（RIS）在未来无线网络中的引入，HyRIS工作计划致力于研究和解决预编码器设计RIS辅助无线网络面临的挑战。具体地，给定RIS在修改反射信号的属性（通过操纵相位和幅度）方面的能力，RIS可以被利用以通过干扰减少和覆盖范围扩展来提高性能。然而，为RIS辅助网络设计最佳预编码器是复杂的。这种复杂性源于预编码设计参数的相互依赖性（即，在发射机、RIS和接收机处）以及硬件和系统约束（例如，有限分辨率相移）。为此，HyRIS旨在设计高效，低成本和低复杂度的实用解决方案，这些解决方案对信道估计误差具有鲁棒性，并且在资源有限的情况下具有可扩展性。

Over the past years, multiple-input multiple-output (MIMO) technology has gained significant traction, especially for communication at millimeter-wave frequencies. In particular, millimeter-wave communications require directional transmission which can be achieved through appropriate precoder design. Looking at the importance of precoder design in such a system and the introduction of reconfigurable intelligent surfaces (RIS) for future wireless networks, the HyRIS work program is dedicated to investigate and address the open challenges for precoder design RIS-assisted wireless networks. In particular, given the capability of RIS in modifying the properties of the reflected signals (by manipulating the phase and amplitude), RIS can be leveraged to boost the performance through interference reduction and coverage extension. Nevertheless, designing optimal precoders for RIS-assisted networks is complex. This complexity stems from the interdependency of the precoding design parameters (i.e., at the transmitter, RIS, and receiver) as well as the hardware and system constraints (e.g., finite-resolution phase shift). To this end, HyRIS aims at devising highly efficient, low-cost, and low-complexity practical solutions which are robust against channel-estimation errors and scalable under limited resources scenarios.