A Low-Complex and Power-Efficient Optical OFDM for VLC Systems

Commercially available Light Emitting Diode (LED) luminaries requires both high power efficiency and low complexity from Visible Light Communication (VLC) system deployments. Asymmetrically-clipped Direct-current (DC) biased Optical-OFDM (ADO-OFDM) is a recently emerged waveform in VLC systems to achieve the optimal solution for spectral and power efficiency problems. However, in ADO-OFDM, a high DC bias is used to attain uni-polar signals which decrease the power efficiency. In this work, we conceive a novel modulation technique called Variably-biased Asymmetrically-clipped Optical OFDM (VAO-OFDM) with pre-distortion for VLC systems. In VAO-OFDM, we design a variably bias which depends on specific samples. Variably bias does not enforce any interference on the originally transmitted symbols because of its frequency components falling on the pre-defined sub-carriers. Due to the pre-distortion process, the computational-complexity of proposed VAO-OFDM is decreased considerably over the ADO-OFDM. Further, the ADO-OFDM and VAO-OFDM performance is evaluated in terms of Bit Error Rate (BER) and power efficiency using MATLAB simulations and validated on the experimental setup by the LabView software-based VLC testbed. Simulation results show that the VAO-OFDM gains SNR of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{10 dB}$</tex-math></inline-formula> at a BER of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-3}$</tex-math></inline-formula> over the ADO-OFDM, and experimental results show that the BER performance of ADO-OFDM and VAO-OFDM is obtained as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.02 \times 10^{-3}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$5.18 \times 10^{-5}$</tex-math></inline-formula> at a signal bandwidth of 1 MHz. Therefore, the VAO-OFDM performance is enhanced substantially when compare to ADO-OFDM.