Document Type : Research Paper
Author
Assistant Lecturer at Al-Furat Al-Awsat Technical University (ATU)
Abstract
Visible light communication (VLC) has gained traction for high-speed wireless connectivity leveraging LED lighting elements. Orthogonal Frequency Division Multiplexing (OFDM) is an attractive modulation scheme owing to its spectral efficiency and resilience to multipath distortion. However, the nonlinear electro-optic transfer characteristics of optical components introduces signal clipping and quantization noise which corrupts OFDM signals. This paper provides an in-depth analysis of clipping and quantization noise to quantify the impact of LED nonlinearities on OFDM-based VLC system performance. Detailed mathematical models are derived for clipping distortions owing to LED optical power saturation and quantization errors from ADC/DAC finite precision in the modulator and driver circuitry. We quantify through simulations the degradations in terms of error vector magnitude (EVM), signal-to-noise ratio (SNR) loss, and bit error rate (BER) under varying clipping ratios and quantization bit-depths. We demonstrate based on 16-QAM OFDM transmission that the LED driver should possess at least 12 dB signal linear dynamic range and 3 bits quantization to restrict SNR penalty within 3 dB. Adaptive tone mapping and digital pre-distortion techniques are discussed to compensate for intensity distortions enabling high-speed OFDM transmission over VLC links.
Keywords
)