Flexible Coverage Control of Reconfigurable Intelligent Surface with Ring-type Codebook

The reconfigurable intelligent surface (RIS), as an innovative device for network deployment, has emerged as a promising technique within the sixth generation (6G) radio network topology. In pursuit of achieving higher beamforming gain within the near-field region due to the high operation frequency and large array size, near-field beamforming schemes such as the ring-type codebook (RTC) have been proposed. Nevertheless, the user equipment (UE)-specific narrow beams generated by the existing schemes are not suitable for RIS to effectively forward control channels, which may require wider beams to cover a group of UEs. In this paper, the wide beam generation scheme based on the RTC codeword selection mechanism is proposed. While combined with the proposed beam shaping methods, RIS can dynamically switch between wide and narrow beams using RTC, providing flexibility in adapting to the forwarding of both data and control channels.