Enhanced versions of DCSK and FM-DCSK data transmission systems

Over the past five years many different modulation schemes have been proposed for chaotic communications. Of these, the DCSK and FM-DCSK techniques offer the best noise performance. However, even the noise performance of these schemes is a few dB worse than that of the conventional noncoherent FSK technique. The paper shows how the noise performance of DCSK and FM-DCSK systems can be improved considerably. Two solutions are considered: in the first version more than one information bit is sent using the same reference signal, while in the second version the received noisy sample functions are cleaned by averaging