Channel Estimation for Reconfigurable Intelligent Surface-Assisted Wireless Communications Considering Doppler Effect

TL;DR

This paper introduces two Doppler-aware channel estimation schemes for RIS-assisted wireless systems, improving accuracy and efficiency in high-mobility scenarios like millimeter-wave communications.

Contribution

It proposes novel wideband CE methods that incorporate Doppler shift adjustment, suitable for multi-path and single-path environments, with minimal additional overhead.

Findings

High CE accuracy achieved in simulations

Low complexity of proposed algorithms

Outperforms benchmark schemes in achievable rate

Abstract

In wireless systems aided by reconfigurable intelligent surfaces (RISs), channel state information plays a pivotal role in achieving the performance gain of RISs. Mobility renders accurate channel estimation (CE) more challenging due to the Doppler effect. In this letter, we propose two practical wideband CE schemes incorporating Doppler shift adjustment (DSA) for multi-path and single-path propagation environments, respectively, for RIS-assisted communication with passive reflecting elements. For the multi-path scenario, ordinary CE is first executed assuming quasi-static channels, followed by DSA realized via joint RIS reflection pattern selection and transformations between frequency and time domains. The proposed CE necessitates only one more symbol incurring negligible extra overhead compared with the number of symbols required for the original CE. For the single-path case which is especially applicable to millimeter-wave and terahertz systems, a novel low-complexity CE method is devised capitalizing on the form of the array factors at the RIS. Simulation results demonstrate that the proposed algorithms yield high CE accuracy and achievable rate with low complexity, and outperform representative benchmark schemes.