Joint Channel Estimation and Signal Recovery for RIS-Empowered Multi-User Communications

TL;DR

This paper introduces two novel joint channel estimation and signal recovery schemes for RIS-assisted wireless systems, leveraging message passing algorithms to improve accuracy and robustness in the presence of numerous unknown variables.

Contribution

The paper proposes two innovative message passing-based schemes for joint channel estimation and signal recovery in RIS systems, addressing key technical challenges and enhancing performance.

Findings

Proposed schemes outperform existing benchmarks in simulations.

The bidirectional approach simplifies complex computations.

RIS parameter settings significantly impact scheme performance.

Abstract

Reconfigurable intelligent surfaces (RISs) have been recently considered as a promising candidate for energy-efficient solutions in future wireless networks. Their dynamic and lowpower configuration enables coverage extension, massive connectivity, and low-latency communications. Due to a large number of unknown variables referring to the RIS unit elements and the transmitted signals, channel estimation and signal recovery in RIS-based systems are the ones of the most critical technical challenges. To address this problem, we focus on the RIS-assisted wireless communication system and present two joint channel estimation and signal recovery schemes based on message passing algorithms in this paper. Specifically, the proposed bidirectional scheme applies the Taylor series expansion and Gaussian approximation to simplify the sum-product procedure in the formulated problem. In addition, the inner iteration that adopts two variants of approximate message passing algorithms is incorporated to ensure robustness and convergence. Two ambiguities removal methods are also discussed in this paper. Our simulation results show that the proposed schemes show the superiority over the state-of-art benchmark method. We also provide insights on the impact of different RIS parameter settings on the proposed schemes.