Layered Optical OFDM With Adaptive Bias for Dimming Compatible Visible Light Communications
Baolong Li, Xiaomei Xue, Simeng Feng, Wei Xu
Abstract
Capable of supporting the dual functionalities of dimming control and high-speed data transmission, dimmable optical orthogonal frequency division multiplexing (O-OFDM) has attracted increasing attentions in visible light communication (VLC). A major design challenge in the dimmable O-OFDM is to realize spectrally efficient VLC link compatible with dimming control while conforming to the low-complexity philosophy of the intensity modulation/direct detection (IM/DD) system. To cope with this challenge, a novel scheme is conceived, named as adaptively biased layered O-OFDM (ABLO-OFDM), which can be well integrated with the industry-preferred pulse width modulation (PWM) dimming technique. Similar to the conventional layered asymmetrically clipped O-OFDM (LACO-OFDM), multiple layers of subcarriers are utilized to transmit information data in ABLO-OFDM, resulting in high spectral efficiency. Only one inverse fast Fourier transform (IFFT) block is required in ABLO-OFDM to generate the layered O-OFDM signal compared to multiple IFFT blocks in LACO-OFDM. Moreover, the demodulation of the dimmable ABLO-OFDM (DABLO-OFDM) signal can straightforwardly rely on standard OFDM receiver, which is immune to the dimming process. Therefore, the proposed scheme achieves high spectral efficiency whilst possessing low-complexity transceiver compared to conventional O-OFDM. It is shown that DABLO-OFDM is superior to its counterparts in terms of the achievable spectral efficiency for intermediate dimming levels.