Optimization of Liquid Lens-based Imaging Receiver for MIMO VLC Systems

TL;DR

This paper introduces a liquid lens-based imaging receiver for MIMO VLC systems that dynamically adjusts focus to reduce channel correlation, significantly improving BER performance under various receiver orientations.

Contribution

The paper develops a mathematical model and optimization schemes for liquid lens adjustment in MIMO VLC, enhancing receiver adaptability and performance over static lenses.

Findings

BER improved from 4e-2 to 5e-4 at 10° orientation variance

Liquid lens adaptation outperforms static lenses in dynamic conditions

Proposed schemes effectively reduce channel correlation

Abstract

In this paper, a liquid lens-based imaging receiver is proposed for multiple-input multiple-output (MIMO) visible light communication (VLC) systems. By dynamically adjusting the focal length and orientation angles of the liquid lens, the spatial correlation between MIMO channel gains is reduced, leading to enhanced bit-error rate (BER) performance. Unlike static lenses, liquid lenses offer adaptability in dynamic conditions, including user mobility and random receiver orientation. An accurate mathematical framework is developed to model the channel gains of the proposed system, and an optimization problem is formulated to minimize its BER. Due to the complexity of the resulting channel model, two lens adjustment schemes, namely, ($i$) the CLS scheme, and ($ii$) the VULO scheme are introduced. Numerical results demonstrate that the proposed liquid lens-based system offers substantial BER improvements over conventional static lens-based receivers across a wide range of random receiver orientation conditions. Specifically, at a random receiver orientation variance of $10^{\circ}$, the BER is improved from $4\times 10^{-2}$ to $5\times 10^{-4}$ by employing the proposed liquid lens.