Differential Pulse-Position Modulation for Multi-User Chaotic Communication

In this paper, we valign="-60pt propose a joint differential pulse position modulation and differential chaos shift key modulation (DPPM-DCSK), where one bit modulates the reference PPM signal by chaotic signal, and the other m(c) bits are mapped by the position index of this chaotic pulse in the information signal. In particular, in the DPPM-DCSK, the information-carrying PPM signal for the current symbol also serves as the reference for the next symbol. It can avoid the energy and rate wastes in the conventional PPM-DCSK. Moreover, we redesign the differential Walsh codes (WC) for DPPM-DCSK to enable multi-user communications. The numerical bit-error-rate (BER) performance of the proposed DPPM-DCSK-WC over multipath Rayleigh fading channels are derived and then verified by simulations. The results demonstrate that the DPPM-DCSK-WC can achieve performance gains of more than 2 dB over the conventional PPM-DCSK and DDCSK-WC for multi-user scenarios, and this gain can be up to 5 dB in the high-delay channels at a BER of 10(-4). In addition, the superior performance of the proposed scheme is proved over ultra-wideband (UWB) wireless channels, which indicates its great potential for chaotic-based wireless applications.