Design of a Superposition Coding PPM-DCSK System for Downlink Multi-User Transmission

The conventional orthogonal multiple-access-based downlink transmission for the differential chaos shift keying system with pulse-position modulation (PPM-DCSK) suffers from lower energy efficiency and data rate. To tackle this problem, a low-complexity superposition coding PPM-DCSK (SC-PPM-DCSK) system for downlink multi-user chaotic communication is proposed in this paper. The proposed system exploits the superposition coding principle on the reference signal and the information-bearing signal to achieve multi-user simultaneous information transmission for the downlink scenario, thus significantly improving the energy efficiency and transmission rate. Furthermore, the analytical expression for the error performance and the throughput of the proposed system are precisely derived over additive white Gaussian noise and multipath Rayleigh fading channels. Simulation results not only verify the accuracy of the analytical method but also illustrate the proposed transmission scheme in achieving significant performance gain compared with the time-sharing-based PPM-DCSK and multiresolution DCSK systems. Due to such superiority, the proposed SC-PPM-DCSK system can be deemed to be an outstanding scheme for downlink multi-user short-range wireless communications.