Performance analysis of precoded layered ACO-OFDM for visible light communication systems

Optical-orthogonal frequency division multiplexing (O-OFDM) is regarded as an effective scheme for intensity modulation and direct detection (IM-DD) based visible light communication (VLC) systems. State-of-the-art O-OFDM approaches complying with IM-DD constraints are; direct-current (DC) biased O-OFDM (DCO-OFDM) and asymmetrically clipped (AC)O-OFDM. ACO-OFDM has half the spectral efficiency (SE) of DCO-OFDM, howbeit, its SE can be augmented towards that of DCO-OFDM using layered ACO-OFDM (LACO-OFDM). Nevertheless, LACO-OFDM suffers from a high peak-to-average power ratio (PAPR). Forthright extension of PAPR reduction techniques devised for ACO-OFDM to LACO-OFDM can be unwieldy and complex. Hence, precoding can be an alternative to counterbalance the high PAPR without a considerable increase in complexity. As our contribution, we comprehensively investigate the performances of Fourier transform (FT) and Hartley transform (HT) precoding on LACO-OFDM. The bit error rate (BER) is analyzed in additive white Gaussian noise (AWGN) and time dispersive channels. Furthermore, the impact of superimposition of layers, PAPR, electrical-to-optical power conversion efficiency and system complexities are also investigated.