Beamformer design for large-dimension reconfigurable intelligent surface (RIS) is investigated. The challenge arises from the expanded near-field of RIS where its beam-forming gain is, in general, distance-dependent due to near-field diffraction. To gain more insights into this effect, we first analyze the performance of conventional collimated beamforming using Fresnel integrals and compare it with that of focused beamforming. Then, a two-step beamforming scheme is proposed. The principle of the proposed scheme is to divide the RIS into multiple subarrays followed by steering the sub-beams of the individual subarrays to focus. Providing proper subarray size, the proposed scheme retains the low complexity of collimated beamforming and achieves a near-optimal performance, as shown both analytically and numerically.
Two-Step Beamforming Scheme for Large-Dimension Reconfigurable Intelligent Surface
01.06.2022
1232756 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch