Channel Analysis and End-to-End Design for Double RIS-Aided Communication Systems with Spatial Correlation and Finite Scatterers

This paper investigates double RIS-assisted MIMO communication systems over Rician fading channels with practical propagation conditions. Firstly, we derive the statistical channel information in closed form, which reveals the various influences of the system and the environment. Next, we study the active and passive beamforming designs for enhancing communication reliability. In particular, we propose a novel end-to-end design, where each 1-dimensional convolutional neural network (1D-CNN) represents a system entity that minimizes the symbol error rate by controlling the transceiver and RISs' phase shifts. Numerical results validate our analysis and demonstrate the superior improvements of phase shift designs to boost system performance. It is demonstrated that the proposed design can encode multiple data symbols simultaneously over different channel realizations and improve the SER performance without requiring channel information at the transmitter.