Quantization Beam Analysis and Codebook Design for One-Bit Reconfigurable Intelligent Surface

The 1-bit phase controlling of the reconfigurable intelligent surface (RIS) is commonly leveraged to reduce deployment costs. However, the 1-bit phase limitation also brings an unavoidable quantization beam on passive beamforming. In this letter, we investigate the quantization beam on a conventional 1-bit RIS and design the prephasing map to suppress the power of the quantization beam while enhancing passive beamforming. In particular, we analytically derive directions of the quantization beam of 1-bit RIS, which is important for interference management and multi-user broadcasting. Moreover, we propose the map fusion (MF) method to improve the power gain in the RIS codebook design while suppressing the power of the quantization beam. The simulation result shows that directions of the quantization beam can be precisely obtained, and the proposed MF method can effectively suppress the negative impact of the quantization beam and improve transmission efficiency.