Real-valued Gram-Schmidt transform-based non-coherent chaos shift keying scheme for visible light communication system

Due to the broadcasting property of visible light channels, the visible light communication (VLC) systems may suffer from the eavesdropping or malicious attacks. In this paper, we exploit the natural high security property of chaotic sequences being sensitive to the initial value, and present an efficient GramSchmidt transform-based non-coherent chaos shift keying (GST-NCSK) modulation scheme to improve the security of information transmission over real-valued VLC channels. In GST-NCSK scheme, the information bits are modulated by the binary phase shift keying (BPSK) scheme, then the BPSK modulated symbols are split to four parallel streams and modulated by the Gram-Schmidt transformed orthogonal chaotic vectors. Then the two modulated symbols and the reference chaotic symbol respectively multiply the weight coefficients to control the bit energy and thereby adjust the lighting color. The resultant symbols are transmitted respectively by the red, green and blue (RGB) light beam of the light emitting diode (LED). The theoretical bit error rate (BER) of the GST-NCSK scheme over the additive white Gaussian noise (AWGN) channel is derived and the security performance is analyzed using the discrete Fourier transform (DFT). The simulations are performed, and the results verify the effectiveness of the theoretical analysis. Moreover, the security is improved by the GST-NCSK scheme with high spectrum efficiency.