Channel Estimation for Optical Intelligent Reflecting Surface-Assisted VLC System: A Joint Space-Time Sampling Approach

TL;DR

This paper introduces a novel channel estimation protocol for optical intelligent reflecting surfaces in visible light communication, leveraging space-time coherence and a joint sampling approach to enable efficient CSI acquisition.

Contribution

It unveils coherence characteristics of OIRS channels and proposes a dynamic beam alignment and joint sampling algorithm for accurate channel estimation.

Findings

The proposed scheme outperforms benchmark methods in accuracy.

The coherence analysis enables faster beam alignment.

Numerical results confirm the effectiveness of the joint space-time sampling approach.

Abstract

Optical intelligent reflecting surface (OIRS) has attracted increasing attention due to its capability of overcoming signal blockages in visible light communication (VLC), an emerging technology for the next-generation advanced transceivers. However, current works on OIRS predominantly assume known channel state information (CSI), which is essential to practical OIRS configuration. To bridge such a gap, this paper proposes a new and customized channel estimation protocol for OIRSs under the alignment-based channel model. Specifically, we first unveil OIRS spatial and temporal coherence characteristics and derive the coherence distance and the coherence time in closed form. Next, to achieve fast beam alignment over different coherence time, we propose to dynamically tune the rotational angles of the OIRS reflecting elements following a geometric optics-based non-uniform codebook. Given the above beam alignment, we propose an efficient joint space-time sampling-based algorithm to estimate the OIRS channel. In particular, we divide the OIRS into multiple subarrays based on the coherence distance and sequentially estimate their associated CSI, followed by a spacetime interpolation to retrieve full CSI for other non-aligned transceiver antennas. Numerical results validate our theoretical analyses and demonstrate the efficacy of our proposed OIRS channel estimation scheme as compared to other benchmark schemes.