Cooperative Reflection Design with Timing Offsets in Distributed Multi-RIS Communications

TL;DR

This paper proposes a new cooperative reflection design for distributed RIS-assisted wireless systems that accounts for timing offsets, improving data recovery accuracy in practical scenarios with synchronization errors.

Contribution

It introduces a novel joint design method that considers timing offsets in multi-RIS systems, which was not addressed in prior works.

Findings

The proposed algorithm effectively reduces mean-squared error in data recovery.

Numerical results show significant performance gains over existing schemes.

The method is computationally efficient and practical for real-world deployment.

Abstract

This letter investigates a wireless communication system deploying distributed reconfigurable intelligent surfaces (RISs). Existing works have assumed that perfect timing synchronization is available among all the cooperative RISs. For practical considerations, we first study cooperative reflection design for multi-RIS-aided communication systems taking into account timing synchronization errors. We aim to minimize the mean-squared error of the recovered data in the presence of timing offsets subject to the unit modulus constraints imposed on the phase shifts of the RISs. In order to handle this sophisticated nonconvex problem, we develop a computationally-efficient algorithm based on the majorization-minimization framework where the RIS phase shift matrices and the timing offset equalizer are respectively developed in a semi-closed form and a closed form. Numerical examples validate the improved performance of our proposed design compared with various schemes.