Orthogonal frequency division multiplexing modulation techniques in visible light communication

With its unique advantages, Visible Light Communication (VLC) can compensate for limitations in radio frequency communication, allowing it to become a recent avid topic of research. Orthogonal Frequency Division Multiplexing (OFDM) has been widely used in VLC due to its high rate of data transfer and frequency selective fading resistance. We compare the performance of several OFDM modulation techniques in VLC, including unipolar schemes, enhanced schemes and hybrid schemes based on discrete Fourier transformation, as well as optical OFDM systems based on Hartley transform and LED index modulation. We perform these comparisons in terms of energy efficiency, spectral efficiency, bit error rate, and algorithm complexity. The principles of some kinds of optical OFDM systems are firstly illustrated and their spectrum efficiencies are theoretically analyzed and compared. We also research and analysis the improved design of receivers in optical OFDM systems. The challenges and upcoming research of OFDM systems in VLC are summarized. The research in this paper can provide a research reference and propose more efficient unipolar modulation schemes to further improve the spectral efficiency and reliability of optical OFDM systems.