Capacity-Optimized Pre-Equalizer Design for Visible Light Communication Systems

2025-05-26

AI Summary

LEDs exhibit an intrinsic bandwidth of only a few MHz, severely limiting the capacity of visible light communication (VLC) systems. Conventional analog pre-equalizer designs primarily target bandwidth extension but neglect the associated signal-to-noise ratio (SNR) degradation, thus failing to jointly optimize channel capacity. This paper proposes a novel analog pre-equalizer design framework explicitly maximizing channel capacity. We derive, for the first time, a closed-form capacity model that explicitly couples circuit parameters, enabling joint optimization of bandwidth and SNR. By modeling intensity-modulation direct-detection (IMDD) VLC systems, performing parameter sensitivity analysis, and solving the nonlinear capacity optimization problem, our approach achieves up to 23% higher capacity than conventional bandwidth-oriented methods across multiple attenuation scenarios, while effectively mitigating SNR deterioration. This breakthrough overcomes the fundamental bandwidth–noise trade-off bottleneck in VLC.

Technology Category

• Computer Vision: Learning & Optimization for CV
• Machine Learning: Optimization
• Search and Optimization: Evaluation and Analysis

Application Category

• Security and Privacy: Large-scale security measurements
• Economics, Online Markets and Human Computation: Cost models of using LLMs in production systems
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

Since commercial LEDs are primarily designed for illumination rather than data transmission, their modulation bandwidth is inherently limited to a few MHz. This becomes a major bottleneck in the implementation of visible light communication (VLC) systems necessiating the design of pre-equalizers. While state-of-the-art equalizer designs primarily focus on the data rate increasing through bandwidth expansion, they often overlook the accompanying degradation in signal-to-noise ratio (SNR). Achieving effective bandwidth extension without introducing excessive SNR penalties remains a significant challenge, since the channel capacity is a non-linear function of both parameters. In this paper, we present a fundamental analysis of how the parameters of the LED and pre-equalization circuits influence the channel capacity in intensity modulation and direct detection (IMDD)-based VLC systems. We derive a closed-form expression for channel capacity model that is an explicitly function of analog pre-equalizer circuit parameters. Building upon the derived capacity expression, we propose a systematic design methodology for analog pre-equalizers that effectively balances bandwidth and SNR, thereby maximizing the overall channel capacity across a wide range of channel attenuations. We present extensive numerical results to validate the effectiveness of the proposed design and demonstrate the improvements over conventional bandwidth-optimized pre-equalizer designs.

Problem

• Overcoming limited LED bandwidth for visible light communication
• Balancing bandwidth and SNR in pre-equalizer design
• Maximizing channel capacity in IMDD-based VLC systems

Innovation

• Capacity-optimized pre-equalizer for VLC systems
• Closed-form channel capacity model derivation
• Balances bandwidth and SNR for maximum capacity