Experimental Research on Adaptive 128/64QAM DFT-Spread IFFT/FFT Size Efficient OFDM With a High SE in VLLC System

In this paper, an adaptive inverse fast Fourier transform and fast Fourier transform (IFFT/FFT) size efficient orthogonal frequency division multiplexing (OFDM) modulation scheme with 128/64-quadrature amplitude modulation (QAM) and discrete Fourier transmission-spread (DFT-spread) is proposed and experimentally demonstrated in a visible laser light communication (VLLC) system with a cost-effective 450-nm blue-light laser diode. The experimental results show that the 5.95 Gb/s adaptive IFFT/FFT size-efficient OFDM with the spectral efficiency of 4.76 b/s/Hz transmission over 5-m free-space can be successfully achieved.