Rate Optimization and Interference Suppression in RIS-assisted MIMO Systems

Abstract

Abstract—Since the beginning of the modern era of wireless communication, the propagation medium has been considered a randomly behaving entity between transmitter and receiver, which degrades the quality of the received signal due to the uncontrollable interaction between the transmitted radio waves and the propagation medium. In 5G systems, in order to obtain higher spectrum efficiency, multiple-input multiple-output (MIMO) is introduced. When MIMO is applied in a multi-cell scenario, inter-cell interference will inevitably deteriorate the quality of service (QoS) of cell edge users. For a cell-edge user that suffers both high signal attenuation from its serving Base Station(BS) and severe co-channel interference from a neighboring BS, an Reconfigurable intelligent surfaces (RIS) can be deployed at the cell edge to help not only improve the desired signal power but also suppress the interference by properly designing its reflect beamforming, thus creating a “signal hotspot” as well as “interference-free zone” in its vicinity. The presence of RIS provides the possibility for different communication needs between multiple devices. This paper proposes a multi-objective optimization method based on non-dominated sorting genetic algorithm II(NSGAII) to improve the achievable rate of communication users while reducing interference to non-communication users.