R-OFDM for RGBA-LED-Based Visible Light Communication With Illumination Constraints

This paper proposes a reshaped orthogonal frequency division multiplexing (R-OFDM) scheme for intensity modulation/ direct detection visible light communication (VLC) systems, where an LED consisting of red, green, blue, and amber chips (RGBA-LED) is adopted as the transmitter. In R-OFDM, the signal is adjusted by signal separation and biasing after clipping (BAC)/scaling before clipping (SBC) operations for transmitting in the RGBA-LED. We optimize both biasing and scaling factors for the BAC and SBC operations, respectively. Correspondingly, a direct detection algorithm is developed for data recovery at receiver. Theoretical bit error rate (BER) performance of the proposed ROFDM scheme is further analyzed. Specifically for the multicolor LED transmission, a low complexity parallel interference cancellation algorithm is also proposed for eliminating the interference caused by cross-talk in multicolor VLC channels. Numerical results over practical optical channels are presented to validate the advantage of the proposed R-OFDM scheme. It is revealed that the R-OFDM achieves noticeable performance gain in term of BER than the conventional Flip-OFDM and ACO-OFDM.