Experimental Demonstration of a Real-Time gigabit OFDM-VLC system with a cost-efficient precoding scheme

We experimentally demonstrated a real-time laser-diode (LD) based orthogonal frequency division multiplexing (OFDM) visible light communication (VLC) system with a cost-efficient precoding scheme. The precoding scheme is based on Hadamard matrix and proposed for combating the fading effect of OFDM-VLC system. Compared with an orthogonal circulant matrix transform (OCT) precoding scheme, the proposed scheme can be realized without multiplier. In the experiment, the OCT scheme and a common pre-emphasis scheme are also implemented in the real-time OFDM-VLC system for comparison. The experimental results show that the effectiveness of the proposed scheme is as same as that of OCT scheme, and compared with the pre-emphasis scheme, the proposed scheme can make a better improvement to the system performance. And when the power of the light received after 3.5-m transmission is beyond 5-mW, by using 32-QAM mapping, the system with the proposed precoding scheme can achieve a data rate at 3.63-Gb/s with a bit-error-rate (BER) at below 3.8e−3.