Anscombe Root DCO-OFDM for SPAD-Based Visible Light Communication

For high-speed visible light communication (VLC) with weak signals such as in underwater environment, dc-biased optical orthogonal frequency-division multiplexing (DCO-OFDM) based on single-photon avalanche diodes (SPADs) is viewed as a promising scheme. Since the channel noise is Poisson distributed, the maximum likelihood (ML) detection is mathematically intractable for DCO-OFDM, and the ML-detection-based minimum distance criterion originally for Gaussian channels is applied to SPAD-based DCO-OFDM. However, the error performance is degraded. For this reason, we propose an Anscombe root (AR) DCO-OFDM by using the existing AR transformation before fast Fourier transformation at the receiver side and a square operation at the transmitter. For the proposed AR-DCO-OFDM, the channel noise is well approximated to be Gaussian distributed, and thus, the asymptotically optimal detection is based on the low-complexity minimum-distance criterion. Extensive simulations indicate that our proposed AR-DCO-OFDM can substantially improve the conventional DCO-OFDM with minimum-distance detection for SPAD-based VLC systems, and the attained gain is above 5 dB at the bit error rate of $\text{10}^{-\text{4}}$ for numerous scenarios.