Optical OFDM aided enhanced 3-D visible light communication systems

In this paper, an optical orthogonal frequency division multiplexing (OFDM) based visible light communication (VLC) system exploiting three-dimensional (3-D) signal mapper is proposed. Both asymmetrically-clipped optical OFDM (ACO-OFDM) and direct-current-biased optical OFDM (DCO-OFDM) are considered, which produce unipolar OFDM signals that can be transmitted through light emitting diodes (LED). Compared with conventional OFDM systems where two-dimensional (2-D) signal mappers and one-dimensional (1-D) inverse fast fourier transform (IFFT) are employed, in the proposed VLC system a 3-D signal mapper equipped with new constellations and the 2-D IFFT for OFDM modulation are utilized, which constitute a new 3-D VLC-OFDM system. The bit error rate (BER) performance of the proposed 3-D VLC-OFDM scheme is evaluated in a general multi-path indoor VLC channel model with the presence of additive white Gaussian noise (AWGN). Simulation results show that the new 3-D VLC-OFDM system is capable of achieving at least 2-5 dB gain in terms of electrical E_b/N₀ at the BER of 10^-4, or even completely removing certain high error floors, as compared with a few conventional 2-D and 3-D counterparts.