On the performance of low-rate wireless correlation-delay-shift-keying system

The performance of a correlation-delay-shift-keying (CDSK) system for low data-rate applications in wireless communications is studied in this paper. In the transmitter, the low-rate data modulates the chaotic spreading sequence by means of a CDSK modulator at baseband. By using a RF modulator, the baseband CDSK-modulated signal is up-converted into a RF passband signal which is then transmitted on the antenna. These modulators allow the transmitter to be able to adjust flexibly the chip period compared with bit duration and locate the transmitted signal at a desired or allocated RF band. The receiver performs in turn the corresponding RF and CDSK demodulations to recover the data. A wireless channel affected by noise, fading, multipath, and delay-spread in the context of low-rate and short-range transmission of the chaotic spread-spectrum signals is described. Schemes for the transmitter and receiver under the impact of the wireless channel are then developed. Bit-error-rate (BER) performance is analyzed with the use of both theoretical derivation and numerical integration. Simulated performance is shown in comparison with the corresponding analyzed ones, where the effect of the spreading factor, modulation delay, and the number of transmission paths on the BER is fully evaluated. Our findings show that the low-rate CDSK system can exploit the multipath nature of wireless channels for improving the BER performance.