Enhanced secure encryption scheme using dual chaotic models for OFDM-VLC system with HD-MMIM.

This paper innovatively proposes a physical-layer security-enhanced scheme for orthogonal frequency division multiplexing visible light communication (OFDM-VLC) based on high-dimensional multi-mode index modulation (HD-MMIM). The scheme deeply integrates a 1D Logistic chaos model and the 4D hyperchaotic model, establishing a multi-level and all-around dynamic protection framework including bit stream XOR encryption, index table encryption, and HD constellation rotation. Experimental results show that HD-MMIM effectively improves the transmission performance of the VLC system. Compared with 4D-MMIM and 5D-MMIM, the 6D-MMIM has a Q-factor increase of 0.63 dB and 1.12 dB, respectively, and the optimal operating range of bias current for 6D-MMIM is extended by 29.38 mA and 19.15 mA, respectively. Meanwhile, the designed physical layer encryption scheme has a key space of up to 10; unauthorized users cannot demodulate the signal without the correct key, greatly resisting brute-force attacks and enhancing system security.