Joint Channel and Symbol Estimation for Hybrid RIS Wireless Communications

The study of advanced architectures for reconfigurable intelligent surfaces (RIS) integrated sensing capabilities has been the focus of recent research in the past few years. A promising architecture is the so-called hybrid RIS (HRIS), which comprises hybrids of sensing and reflecting meta-atoms. This enables HRIS to have signal processing capabilities, which can be used to partially solve the channel estimation task. This work proposes a semi-blind approach to the HRIS-assisted MIMO wireless communication system by empowering the HRIS with joint symbol detection and channel estimation functions based on alternating least squares estimation methods. Simulation results indicate the remarkable performance of the proposed receivers in terms of normalized mean square error and symbol error rate, compared to solutions found in the literature, showing the efficacy of HRIS in MIMO systems and the potential of semi-blind methods in this context.