Codebook Design and Autoencoder-based Codeword Selection for RIS-assisted Communications

In this paper, a one-bit beamforming codebook for Reconfigurable Intelligent Surface (RIS) is designed for an indoor environment. Each codeword in a codebook is a phase pattern at RIS elements that reflects the signal to a desired angle. For a specific reflection angle, those codewords are computed that maximizes the signal-to-noise ratio (SNR) at the receiver (RX). Since multiple codewords can maximize the SNR, an algorithm to reduce the size of the codebook is proposed. This ensures that the codebook does not contain repetitive codewords. In addition, after the codebook design, the codeword selection procedure is performed using an Autoencoder (AE) that minimizes the Bit Error Rate (BER) at the receiver. The proposed method shows promising results compared to existing techniques in terms of BER with reduced codebook size.