Binary CGH encryption coding-based DCO-OFDM VLC transmission system

To enhance the security of visible light communication (VLC), a transmission system combining computer generated holography (CGH) cryptographic coding and discrete Fourier transform (DFT) precoding DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) is proposed. First, the transmitted information is encrypted using double random phase and recorded in binary real-valued CGH using Lohmann coding. Next, DFT precoding is applied to the quadrature amplitude modulation (QAM) symbol vector. Finally, DCO-OFDM modulation is executed, and the OFDM signal reaches the receiver through the VLC channel. Transmission simulation shows that the secure transmission scheme not only provides high security, but also reduces the peak to average power ratio (PAPR) of OFDM signals and improves the system's bit error rate (BER). Furthermore, the secure transmission system demonstrates excellent anti-noise and anti-shearing performance. In low SNR and information loss scenarios, the reproduced image at the receiver end maintains a high correlation with the original transmitted image.