Study of high-order non-equal probability QAM for visible light communication systems

Area of Science:

• Optical Communications
• Digital Modulation Schemes
• Visible Light Communication (VLC)

Background:

• Visible Light Communication (VLC) systems offer a promising alternative for high-speed wireless data transmission.
• Traditional Quadrature Amplitude Modulation (QAM) schemes face limitations in VLC due to nonlinearities in Light-Emitting Diodes (LEDs).

Purpose of the Study:

• To propose and experimentally demonstrate a high-order non-equal probability quadrature amplitude modulation (NEP-QAM) scheme for enhanced VLC performance.
• To address the performance degradation caused by LED nonlinearities in VLC systems.

Main Methods:

• Development of a novel NEP-QAM scheme, specifically NEP-72QAM, utilizing nonlinear coding for signal generation.
• Implementation of a bit-to-symbol labeling scheme to achieve thorough Gray mapping for improved error performance.
• Experimental validation of the NEP-72QAM scheme in a VLC system.

Main Results:

• The proposed NEP-72QAM scheme demonstrates superior performance compared to the traditional 64QAM scheme under both linear and nonlinear LED operating conditions.
• The NEP-72QAM scheme shows a minimal reduction in the driving peak-to-peak voltage range (20 mV) compared to probabilistically shaped 72QAM for a given mutual information threshold.
• The NEP-72QAM scheme offers significantly lower complexity than existing probabilistically shaped modulation schemes.

Conclusions:

• The NEP-72QAM scheme is an effective modulation strategy for improving the performance and efficiency of visible light communication systems.
• This modulation technique provides a practical solution for overcoming LED nonlinearities and reducing system complexity.
• NEP-QAM represents a significant advancement for future VLC applications.