Enhanced ADO-OFDM-based adaptive digital dimming VLC system

Abstract

Visible light communication (VLC) has shown significant growth in recent years. VLC simultaneously offers illumination and communication. In VLC systems, dimming control is used to handle the lighting and energy consumption constraints. In this paper, a new, to the best of our knowledge, adaptive digital dimming optical-orthogonal frequency division multiplexing (ADDO-OFDM) based on pulse width modulation is proposed to combine enhanced asymmetrically clipped DC biased optical OFDM (EADO-OFDM) and negative EADO-OFDM (ENADO-OFDM). It exploits the performance benefits of EADO-OFDM and ENADO-OFDM. The proposed ADDO-OFDM controls the dimming level in a vast range with an acceptable bit error rate with a favorable data length.

Real-Time Implementation of Hybrid Visible Light/Infrared Communications Supporting Full-Range Dynamic Dimming Control

“…In this figure, the PWM duty cycle is set at 0.6, and the PWM period is set at 0.0184 s, which means the frequency is higher than 50 Hz to alleviate the flickering effect. It is clear that the waveform is formed by a PWM and an inverted PWM waveform, each carrying different data frames, corresponding to (10). During PWM "ON" slots, VL frames carrying PAM4 symbols are received, while during PWM "OFF" slots, IR frames carrying OOK symbols are received.…”

“…In recent years, extensive research has been dedicated to VLC dimming control, primarily focusing on techniques such as amplitude modulation (AM) and pulse width modulation (PWM) [9], [10], [11]. In AM-based approaches, brightness control relies on adjusting the current supplied to the light source, but this method may compromise dimming precision, reduce device lifespan, and cause chromaticity shift problems [12], [13].…”

Recent progress in InGaN-based photodetectors for visible light communication

“…Compared to on–off keying (OOK), OFDM has attracted much attention due to its robustness against inter-symbol interference (ISI) and frequency-selective fading, which can increase the data rate of the communication link. 49 By dividing a wide fading channel into multiple narrow sub-channels, flatness can be assumed at each sub-channel and receiver, and simple single-tap equalization can be performed to effectively cancel the channel effects and enhance the communication capability of the device. 48 This characteristic makes OFDM highly advantageous when used in band-limited systems compared to other frequency-division multiplexing (FDM) techniques.…”

“…48 This characteristic makes OFDM highly advantageous when used in band-limited systems compared to other frequency-division multiplexing (FDM) techniques. In the OFDM modulation scheme, there are two ways to increase the high rate: (1) using a higher QAM order and modulate relatively few subcarriers; 49 (2) adopting a lower QAM order and modulating relatively more subcarriers. 48 The first method requires a higher sub-carrier signal-to-noise ratio, while the second method increases the computational complexity.…”