Time domain reshuffling for OFDM based indoor visible light communications

For orthogonal frequency division multiplexing (OFDM) based indoor visible light communication (VLC) systems, we show that the subcarrier channels tend to synchronize and add up to a resultant high peak signal at the leading edge of each symbol when using certain types of modulation formats. Thus, occasional non-ideal transmission conditions such as insufficient guard intervals and a dispersive channel will result in inter-symbol crosstalk. This paper presents a time domain reshuffling (TDR) technique for both DC-biased optical (DCO-) and asymmetrically clipped optical (ACO-) OFDM based VLC systems. Only by simple operations in the frequency domain, the potential high peaks can be relocated in each OFDM symbol to alleviate the crosstalk. Based on Monte-Carlo simulations, we demonstrate the statistical distribution of the signal high peak values and the complementary cumulative distribution function of the peak-to-average power ratio for comparison. By adopting the TDR method, we show that the bit error rate performance can be also improved for both DCO- and ACO-OFDM systems under occasional non-ideal transmission conditions.