Predistortion and pre-equalization for nonlinearities and low-pass effect mitigation in OFDM-VLC systems

Area of Science:

• Optical Communications
• Wireless Networks
• Signal Processing

Background:

• Visible Light Communication (VLC) using Orthogonal Frequency Division Multiplexing (OFDM) is promising but suffers performance degradation.
• Nonlinearity in High-Power Light-Emitting Diodes (HPLEDs) concerning current and temperature causes significant OFDM-VLC issues.
• High-frequency attenuation in HPLEDs and photodiode capacitance further reduce the signal-to-noise ratio (SNR).

Purpose of the Study:

• To experimentally confirm and model OFDM-VLC performance degradation caused by HPLED nonlinearity and temperature.
• To propose and evaluate a predistortion and digital pre-equalization scheme for mitigating these degradations.
• To demonstrate the effectiveness of the proposed scheme in improving OFDM-VLC system performance.

Main Methods:

• Experimental confirmation and modeling of HPLED nonlinearity and temperature effects on OFDM-VLC.
• Development of a predistortion and digital pre-equalization scheme utilizing a luminous feedback signal.
• Mathematical modeling, simulation, and experimental validation of the proposed mitigation strategy.

Main Results:

• The proposed predistortion and pre-equalization scheme effectively linearizes the transmitted light signal.
• A uniform SNR across all OFDM subcarriers is maintained, significantly enhancing system performance.
• Performance improvements were validated against systems without predistortion, with fixed predistortion, and with simple post-equalization.

Conclusions:

• The developed predistortion and pre-equalization scheme successfully mitigates HPLED nonlinearity and frequency attenuation in OFDM-VLC systems.
• This approach offers a robust solution for improving the reliability and efficiency of visible light communication.
• The findings pave the way for more advanced and stable VLC applications utilizing OFDM transmission.