Color Multiplexing Based Unipolar OFDM for Indoor RGB LED Visible Light Communication

In this paper, a novel unipolar orthogonal frequency-division multiplexing (OFDM) scheme is proposed for indoor intensity modulation/direct detection (IM/DD) visible light communication (VLC) using red-green-blue (RGB) light emitting diode (LED). The positive and negative parts of a bipolar OFDM signal are transmitted separately on two colors of a RGB LED through color multiplexing. Compared with conventional DC biased optical OFDM (DCO-OFDM) or asymmetrically clipped optical OFDM (ACO-OFDM), the proposed color multiplexed optical OFDM (CMO-OFDM) can greatly improve the overall power efficiency of indoor VLC systems without reducing the total transmission capacity. Two types of receivers are designed and their performances are examined for CMO-OFDM based indoor VLC systems. By utilizing a practical RGB LED model, performance comparisons between CMO-OFDM and conventional unipolar OFDM schemes have also been conducted. The obtained results show that, to achieve the same bit rate, CMO-OFDM based indoor VLC system requires the least average optical power.