Subcarrier and Power Allocations for Dimmable Enhanced ADO-OFDM With Iterative Interference Cancellation

In this paper, a novel modulation scheme called enhanced asymmetrically clipped DC-biased optical OFDM (eADO-OFDM) is proposed to accommodate different demands of multi-users in downlink multiple access for visible light communication systems. Meanwhile, to satisfy various dimming levels, enhanced negative ADO-OFDM (eNADO-OFDM) is investigated and combined with eADO-OFDM for multiplexing transmission. By adjusting the proportion of these two signals, the dimming control scheme can be achieved, while the entire dynamic range of light-emitting diodes is exploited. In order to achieve superior transmission performance, the optimal power allocation under the desired dimming level is studied to minimize the overall bit error rate (BER). Moreover, to obtain more accurate estimation, an iterative receiver with interference cancellation, in which the pairwise averaging and pairwise clipping are exploited, is proposed. The simulation results show that the proposed scheme can effectively carry out the dimming control with wide dimming range for illumination and achieve superior BER performance at the same signal-to-noise ratio compared to the conventional counterparts, while only a few iterations are required.