Location-aware Beamforming Design for Reconfigurable Intelligent Surface Aided Communication System

The reconfigurable intelligent surface (RIS) is promising in fulfilling the requirement of green communication in the fifth- and sixth-generation (5G/6G) mobile communication networks. Considering the limits of the conventional channel state information (CSI) acquisition techniques for the RIS-aided communication system, this paper proposes a location-aware beamforming design for the RIS-aided millimeter-wave (mmWave) communication system without the channel estimation process. First, according to the system geometry, the relationship between the channel model and the user location is established, which is further used to derive the CSI error bound using the location error bound. Then, a worst-case robust beamforming optimization problem is formulated and solved to combat the effect of location error on the beamforming design. Simulation results demonstrate that the proposed approach outperforms the conventional non-robust approach in terms of the worst-case signal-to-noise ratio (SNR) at the receiver, and becomes more advantageous in the presence of higher level of the user location uncertainty.