Efficient Data Transmission Using MPPM Dimming Control in Indoor Visible Light Communication

Abstract

In conventional visible light communication (VLC) dimming control systems utilizing pulse width modulation (PWM), reducing the duty cycle will push up the receiver sensitivity requirement if the transmission rate is kept constant. In this paper, we investigate a dimming control mechanism in indoor VLC to satisfy the receiver sensitivity requirement, which can achieve efficient data transmission while maintaining communication quality. To transmit excess signals, we propose a modification based on a conventional PWM scheme, which combines multi-pulse position modulation (MPPM) dimming control pulses with orthogonal frequency division multiplexing (OFDM) signals. Numerical results show that by utilizing the MPPM pattern effect, excess signals are transmitted, which can reduce the quadrature amplitude modulation (QAM) symbol rate and alleviate the receiver sensitivity requirement under a steadily high data rate and a bit error rate (BER) that is less than 10 À3 .

Hybrid modulation schemes for data transmission improvement of indoor visible light communication system

“…Here, Boltzmann's constant is k, absolute temperature is , the open-loop voltage gain is G,  is the fixed capacitance of photo-detector per unit area and m g is the FET transconductance. The all previous parameters are presented in [3], [22], [24]. Signals are only transmitted within the "on" period of PWM pulses in conventional PWM dimming control systems.…”

“…Signals are only transmitted within the "on" period of PWM pulses in conventional PWM dimming control systems. Thus, for intensity modulation signals, if it is required to keep the average data rate constant, the M-QAM required data rate after dimming is inversely-proportional to duty cycle D [22][23][24] which can be represented as…”

“…By using MPPM pattern encoding, excess data transmission can be achieved and the reduced data rate due to dimming control can be compensated. It is verified that proposed method can allow reduction of QAM symbol rate and required receiver sensitivity while stretching the range of reliable constant rate transmission [22][23][24]. This work introduces an elaborated modeling and simulation of the compensating effect of the different pulse position modulation techniques on the conventional M-QAM DCO OFDM PWM modulation dimming techniques.…”

“…This means that the bit error rate (BER) performance gets degradation and the power consumption of the VLC system decreases [20][21]. In order to compensate for the decreased data rate when dimming, a method to combine variable M-QAM DCO OFDM signal with multiple pulse position modulation (MPPM) dimming control pulses is proposed in [22]. By using MPPM pattern encoding, excess data transmission can be achieved and the reduced data rate due to dimming control can be compensated.…”

Dimmable Visible Light Communications Based on Multilayer ACO-OFDM

“…Alternatively, a much wider PWM signal is used in [16] where the time-domain OFDM signals are only modulated during the on-state of PWM, which is easy to implement but sacrifices the data rate since the time of off-state is wasted. The idea is further extended in [17] to utilize multi-PPM (MPPM) for dimming control and carrying information simultaneously, where more information bits can be transmitted but the disadvantage of wasting time is still unsolved. Reverse polarity optical-OFDM is proposed in [18], which combines the fast ACO-OFDM signal with the relatively slow PWM dimming signal to fully utilize the duty cycle and LED dynamic range.…”