Hybrid Beamforming Algorithm with Null Steering for RIS-empowered 6G System

In this paper, we explore advancements in the 6th-generation mobile communication system (6G) to achieve extremely high-speed communication with peak data rates surpassing 100 Gbps. Our research focuses on enhancing MIMO spatial multiplexing capabilities by developing a New Radio Network Topology (NRNT) utilizing devices like Reconfigurable Intelligent Surfaces (RIS) to control the reflection and transmission of radio waves. Concurrently, we address propagation losses in high-frequency bands, such as millimeter waves (mmW), through the use of massive MIMO (mMIMO) and cost-effective hybrid beamforming (BF) techniques. However, when integrating NRNT and hybrid BF, traditional beam selection algorithms, such as the maximum RSRP criterion, may fail to select beams that facilitate multiple propagation paths (multipaths). To address this, we propose a novel method that enables beam selection towards previously un selected RIS directions. This is achieved by employing vectors from the kernel of the channel matrix, inclusive of analog beams between the base station (BS) and mobile station (MS), as precoding vectors on the BS side. This approach generates beams with nulls in the directions of already selected RIS paths, effectively enhancing multipath formation. We validate the efficacy of our proposed method through MIMO link-level simulations, demonstrating its potential for improving 6G network performance.