PWM‐based dimmable hybrid optical OFDM for visible‐light communications

In visible‐light communication (VLC) system, hybrid asymmetrically clipped optical orthogonal frequency division multiplexing (HACO‐OFDM) is an attractive multi‐carrier modulation to achieve high power and spectrum efficiency. Dimming control is deemed to be an essential technique in VLC since it can meet diverse luminance demands. However, severe non‐linear distortion occurs when dimming the HACO‐OFDM VLC system, especially with the pulse‐width modulation (PWM) dimming technique. In this work, a novel PWM‐based dimmable hybrid optical OFDM (DHO‐OFDM) scheme is proposed to simultaneously support different illumination requirements and realise a spectral‐efficient VLC link. The transmitted symbols in the authors' proposed DHO‐OFDM can be readily estimated by the standard HACO‐OFDM receiver without requiring the additional detecting the PWM signal, thus reducing the receiver complexity compared to the other PWM‐based dimmable schemes. Moreover, the proposed DHO‐OFDM scheme can support a broad dimming range with a relatively stable communication performance, which makes it more suitable for broadband data transmission. Numerical results have verified the superiorities of DHO‐OFDM over the conventional OFDM schemes in terms of achievable spectral efficiency and bit‐error rate.