Adaptation of OFDM under visible light communications and illumination constraints

Abstract

Orthogonal frequency division multiplexing (OFDM) is increasingly studied and adopted as a modulation technique for RF and optical communication systems. In this paper, we investigate challenges to the adoption of OFDM for use in lighting systems that support both intensity control and data communication based on the visible light communication (VLC) technology. In particular, we survey the requirements for energy efficiency, intensity control (dimming) and light-emitting diode (LED) driver integration in lighting systems. These requirements are mapped to contemporary and novel OFDM adaptations to show how both the lighting and communications needs can be met in dual-use scenarios while preserving both missions with reasonable performance.

Odd clipping optical orthogonal frequency division multiplexing for VLC system

“…15,16 In order to minimize the clipped parts of the signal, the DC offset is represented as a function of the standard deviation of x[n] as presented in (4) and (5). Finally, the DCO-OFDM adds DC offset to the generated real signal to resolve the problem of the negative parts.…”

“…Suitable value for DC offset is used and then clipping the negative parts of the signal is done. 15,16 In order to minimize the clipped parts of the signal, the DC offset is represented as a function of the standard deviation of x[n] as presented in (4) and (5).…”

“…It was showed that the hybrid scheme offers a good solution for the BER PAPR trade-off as it provides effective PAPR with reduced BER. While in, 16 the author proposed hybrid Pulse Time Modulation (PTM) and DCO-OFDM scheme as a solution for the PAPR problem, the study resulted in Signal-to-Noise Ratio (SNR) gain of 0.9 dB and 0.1 dB for 8-QAM and 16-QAM, respectively, by converting the DCO-OFDM sample into a PTM format before transmitting it.…”

Dimming Control in Visible Light Communication using RPO-OFDM and Concatenated RS-CC

“…The Optical-Orthogonal Frequency Division Multiplexing (O-OFDM) dimming schemes were introduced in 2011 [11]. Simple OFDM based schemes such as the bipolar Direct Currentbiased Optical-OFDM (DCO-OFDM) and Asymmetrically Clipped Optical -OFDM (ACO-OFDM) schemes were commonly used to achieve dimming yet maintaining reliable communication links [6], [12]- [15]. In all the modulation methods mentioned above, data cannot be modulated on to the PWM carrier signal at off pulses (when the PWM pulse is zero).…”

“…The RPO-OFDM was capable of utilizing the full LED dynamic range by reversing the polarity of the PWM pulses thereby ensuring full transmission at all times. It proved to provide better results than other O-OFDM schemes in terms of BER, SNR and data rates [1], [2], [6], [15].…”