Robust Precoding for Multi-User Visible Light Communications with Quantized Channel Information

TL;DR

This paper develops a robust precoding method for multi-user visible light communication systems that accounts for quantized channel information, minimizing power while ensuring quality of service.

Contribution

It introduces a novel robust precoding design that handles channel quantization errors in VLC, formulated as a second order cone programming problem.

Findings

Robust precoder effectively reduces power consumption.

Performance degrades gracefully with increased quantization levels.

Proposed method outperforms non-robust precoding in quantized scenarios.

Abstract

In this paper, we address the design of multi-user multiple-input single-output (MU-MISO) precoders for indoor visible light communication (VLC) systems. The goal is to minimize the transmitted optical power per light emitting diode (LED) under imperfect channel state information (CSI) at the transmitter side. Robust precoders for imperfect CSI available in the literature include noisy and outdated channel estimation cases. However, to the best of our knowledge, no work has considered adding robustness against channel quantization. In this paper, we fill this gap by addressing the case of imperfect CSI due to the quantization of VLC channels. We model the quantization errors in the CSI through polyhedric uncertainty regions. For polyhedric uncertainty regions and positive real channels, as is the case of VLC channels, we show that the robust precoder against channel quantization errors that minimizes the transmitted optical power while guaranteeing a target signal to noise plus interference ratio (SNIR) per user is the solution of a second order cone programming (SOCP) problem. Finally, we evaluate its performance under different quantization levels through numerical simulations.