Effect of Rayleigh fading on non-coherent sequence synchronization for multi-user chaos based DS-CDMA

This paper presents the theoretical analysis and simulation results of the effects of frequency flat fading on non-coherent synchronization of a chaos-based DS-CDMA system. The quality of synchronization, both in acquisition and tracking stages, is evaluated in the presence of noise, inter-user interference and fading. This is the first time that a chaotic pilot is used for a non-coherent synchronization block giving it both security (complete signal masking including pilot) as well as usability in low SNRs. There is close agreement between the derived analytical upper bound results in the presence of fading and the simulation results. It is shown in theoretical analysis and simulation that the error output of the tracking loop can be approximated to a Gaussian distribution. Two chip waveforms have been investigated for non-coherent tracking and noise performance of the tracking phase is simulated. The bit error rate of a DS-CDMA system with a chaotic pilot is then investigated in the presence of noise and fading. The effect of partial (worst case) synchronization in terms of SNR difference is then evaluated to be 1 dB for the noise only case, 0.1 dB for single user case with uncompensated fading and 1.1 dB for the eight user case.