Using chaotic signals in spread-spectrum communications has a few clear advantages over traditional approaches. Chaotic signals are nonperiodic, wide-band, and more difficult to predict, reconstruct, and characterize than periodic carriers. These properties of chaotic signals make it more difficult to intercept and decode the information modulated upon them. The differential chaos shift keying (DCSK) is a non-coherent modulation scheme, and has good anti-noise performance. In this paper, based on the fundamental theories and with some recent researches of others, the DCSK performance is analyzed and the expressions of the bit error rates are derived for DCSK under AWGN channel, Rayleigh fading channel and Ricean fading channel. In the end, the Logistic mapping with zero mean is used for chaos generation in simulation and compared with simulation results. .Key words: DCSK; Rayleigh fading channel; Ricean fading channel ; Bit error rate . Introduction Chaotic signals have the characteristic of non-periodic, random-like, inherent wideband and sensitive dependence upon initial conditions, etc. Thus, chaotic signals have been widely applied to communication field. Broad continuous spectra of chaotic signals make them very appealing for use as carriers in spread-spectrum communications. Research in this direction has drawn considerable interest in the last few years[1-4]. At present, the studying of the chaos-based communications mainly focuses on chaotic digital communications which include chaotic digital keying modulation, chaos-based direct sequence spread spectrum, chaotic pulse position modulation, and so on. Among them, chaos keying modulation communication systems mainly include chaos shift keying (CSK)[3], chaotic on-off-keying (COOK)[4], differential chaos shift keying (DCSK)[5], frequency-modulated differential chaos shift keying (FM-DCSK)[6], correlation delay shift keying (CDSK)[7], etc. Because of sensitivity for initial conditions, it is difficult that chaotic signals realize reliably synchronization both two sides of transmitter and receiver. Therefore, non-coherent chaos communication systems which don't need chaos-synchronization are becoming a studying focus all over the world recently. DCSK is a typical non-coherent chaos-based communication scheme, almost insensitive to channel distortion, and has good anti-noise performance. In addition, it uses the random-like characteristic of chaotic signals to reach the aim of hidden signal. Therefore, DCSK is one of the chaos-based communication schemes that attract increasing attention [8][9].
