On Visible Light Communication Using LED Array with DFT-Spread OFDM

DFT-Spread OFDM has been well studied in radio frequency (RF) systems thanks to its effectiveness in reducing the peak-to-average power ratio (PAPR). However, due to the inherent positive real signal constraint in visible light communications (VLC), the implementation of DFT-Spread OFDM in VLC faces some different challenges with respect to its high PAPR. This paper presents an LED array assisted visible light communication system using DFT-Spread OFDM. With this technique, theoretical analysis are firstly derived to help characterize the system PAPR reduction in VLC systems. Specifically, two different subcarrier allocation modes namely localized DFT-Spread and interleaved DFT-Spread OFDM are explicitly studied with their time domain signal expressions. Moreover, based on the results, detailed comparisons of DFT-Spread OFDM in terms of PAPR reduction are made for VLC and RF systems. Simulation results show that the proposed system not only leads to a reduced PAPR, but also achieves a performance gain in BER without any loss of system transmission rate.