Channel Estimation for STAR-RIS-aided Wireless Communication

TL;DR

This paper proposes efficient uplink channel estimation schemes for STAR-RIS-assisted two-user systems, comparing time switching and energy splitting protocols, and demonstrating improved estimation accuracy with optimized training strategies.

Contribution

It introduces novel channel estimation schemes tailored for STAR-RIS with TS and ES protocols, including an algorithm for joint design of pilots, power-splitting, and training patterns.

Findings

TS protocol yields lower channel estimation error than ES.

Proposed algorithms effectively improve channel estimation accuracy.

Numerical results validate the efficiency of the proposed schemes.

Abstract

In this letter, we study efficient uplink channel estimation design for a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted two-user communication systems. We first consider the time switching (TS) protocol for STAR-RIS and propose an efficient scheme to separately estimate the channels of the two users with optimized training (transmission/reflection) pattern. Next, we consider the energy splitting (ES) protocol for STAR-RIS under the practical coupled phase-shift model and devise a customized scheme to simultaneously estimate the channels of both users. Although the problem of minimizing the resultant channel estimation error for the ES protocol is difficult to solve, we propose an efficient algorithm to obtain a high-quality solution by jointly designing the pilot sequences, power-splitting ratio, and training patterns. Numerical results show the effectiveness of the proposed channel estimation designs and reveal that the STAR-RIS under the TS protocol achieves a smaller channel estimation error than the ES case.