Digital signal transmission with cascaded heterogeneous chaotic systems

A new chaos based secure communication scheme is proposed to transmit digital signals by combining the concepts of chaotic-switching and chaotic-modulation approaches. In this scheme two heterogeneous chaotic circuits are used both at the transmitter and receiver modules. First a binary message signal is scrambled by two chaotic attractors produced by a set of chaotic systems (No. 1) of the drive module. The so produced small amplitude scrambled chaotic signal is further directly injected or modulated by different chaotic system (No. 2) within the drive module. Then the chaotic signal generated by this second chaotic system No. 2 is transmitted to the response module through the channel. An appropriate feedback loop is constructed in the response module to achieve synchronization among the variables of the drive and response modules and the binary information signal is recovered by using the synchronization error followed by low-pass filtering and thresholding. Simulation results are reported in which the quality of the recovered signal is higher and the encoding of the information signal is potentially secure. The effect of perturbing factors like channel noise and nonidentity of parameters are also considered.