Optimization of Probabilistic Constellation Shaping for Optical OFDM Systems with Clipping Distortion

2025-07-10

AI Summary

The integration of probabilistic constellation shaping (PCS) with direct-current-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) exacerbates peak-to-average power ratio (PAPR) and associated clipping distortion, degrading spectral efficiency and channel capacity. Method: This paper proposes a PCS optimization framework that jointly accounts for clipping-induced nonlinear distortion to maximize channel capacity. By modeling the clipping nonlinearity, the capacity maximization problem is formulated as a nonconvex optimization, efficiently solved via projected gradient descent. Contribution/Results: The proposed method preserves the spectral efficiency gains of PCS while significantly suppressing PAPR and clipping distortion. Simulation results demonstrate that, under aggressive clipping conditions, the scheme achieves up to 1.8 bit/s/Hz higher capacity than conventional uniform modulation and enhances system robustness—offering a novel pathway toward high-power-efficiency optical wireless communication.

Technology Category

• Search and Optimization: Non-convex Optimization
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Computer Vision: Learning & Optimization for CV

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Security and Privacy: Large-scale security measurements
• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation

Abstract

Optical orthogonal frequency-division multiplexing (OFDM) and probabilistic constellation shaping (PCS) have emerged as powerful techniques to enhance the performance of optical wireless communications (OWC) systems. While PCS improves spectral efficiency and adaptability, we show that its integration with optical OFDM can inadvertently increase the peak-to-average power ratio (PAPR) of the signal, exacerbating clipping distortion due to signal clipping. This letter investigates the impact of PCS on the PAPR of direct current-biased optical OFDM (DCO-OFDM) waveforms and proposes an optimization of PCS that maximizes channel capacity, considering clipping distortion. The optimization problem is shown to be complex and non-convex. We thus present a suboptimal yet efficient solving approach based on projected gradient descent to solve the problem. Simulation results demonstrate the superiority of the proposed approach over the conventional uniform signaling, particularly under severe clipping distortion conditions.

Problem

• Optimize PCS to reduce PAPR in optical OFDM systems
• Maximize channel capacity considering clipping distortion effects
• Develop efficient algorithm for non-convex PCS optimization problem

Innovation

• Optimizes PCS for optical OFDM systems
• Uses projected gradient descent method
• Reduces clipping distortion effectively