Comparison of the Nonlinear Dynamic Pre- and Post-LED Equalization
1Institute of Telecommunications, Warsaw University of Technology, Nowowiejska 15/19, 00-665 Warsaw, Poland.
Sensors (Basel, Switzerland)
|March 10, 2022
Summary
This study compares pre- and post-equalizers for Visible Light Communications (VLC) systems. Both equalizers perform similarly, but the post-equalizer offers a slight advantage in highly nonlinear conditions with high signal-to-noise ratios.
Area of Science:
- Optical Communications
- Signal Processing
Background:
- Visible Light Communications (VLC) systems utilize white Light-Emitting Diodes (LEDs) as both light sources and transmitters.
- LEDs in VLC systems suffer from low bandwidth and high nonlinearity, necessitating equalization for effective signal transmission.
Purpose of the Study:
- To compare the performance of pre- and post-equalizers in mitigating LED nonlinear dynamic response in VLC systems.
- To evaluate equalizer effectiveness using Modulation Error Ratio (MER) under varying channel conditions and noise levels.
Main Methods:
- A Wiener-Hammerstein model simulated the nonlinear dynamic behavior of the LED.
- A Volterra series-based equalizer, specifically dynamic deviation reduction, was employed for pre- and post-equalization.
- Multilevel Pulse Amplitude Modulation (PAM) was used as the signal format.
Main Results:
- Pre- and post-equalizers showed comparable performance in linear/moderately nonlinear channels with high noise.
- The post-equalizer demonstrated a slight performance improvement (a few dB in MER) in highly nonlinear channels with high Signal-to-Noise Ratio (SNR).
Conclusions:
- The findings provide insights for correcting dynamic characteristics of LEDs in VLC systems.
- Equalizer choice depends on the specific channel nonlinearity and noise conditions for optimal VLC performance.
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