PAPR reduced OFDM visible light communication using exponential nonlinear companding

In visible light communication (VLC), LEDs are used to transmit data using intensity modulation. LEDs have a limited operating voltage range and the voltage-current characteristic shows a nonlinear behavior. When an orthogonal frequency division multiplexing (OFDM) signal is used to drive these transmitter LEDs (VLC-OFDM), LED chip overheating and nonlinear distortions occur, due to high peak-to-average power ratio (PAPR) of the OFDM signal. Unlike radio frequency baseband communication systems, the VLC-OFDM signal is a real-valued signal. This would lend itself to the PAPR reduction in VLC-OFDM. In this paper, we propose to use exponential nonlinear companding transformation techniques in VLC-OFDM to reduce the PAPR. Simulation results demonstrate that with the exponential companding function employed in VLC-OFDM, the PAPR of the VLC-OFDM is significantly reduced, compared with previously considered methods.