FM-DCSK: a novel method for chaotic communications

In binary Differential Chaos Shift Keying (DCSK), each information bit is mapped to the correlation between two pieces of a chaotic waveform. The receiver determines the correlation (which is proportional to the energy per bit) in order to demodulate the received signal. Since a chaotic signal is not periodic, the energy per bit is not constant and can only be estimated, even in the noise-free case. This estimation has a non-zero variance that limits the attainable data rate. This problem can be avoided if the energy per bit is kept constant. In this paper, the DCSK technique is combined with frequency modulation in order to achieve two properties: the excellent noise performance of DCSK is maintained; in addition, the energy per bit is kept constant in order not to limit the data rate. A low-pass equivalent model that significantly speeds up the simulation of an FM-DCSK system is also developed. Finally the noise performance of the proposed FM-DCSK system is given.