Inherent diversity combining techniques to mitigate frequency selective fading in chaos-based DSSS systems

Analysis of communication systems with combiners, assuming flat fading channels, is well-known. However, this analysis for a chaos-based DSSS system with a frequency selective channel, giving proper mathematical model and derived expressions for the probability of error, practically does not exist. This paper presents the theoretical model of a chaos-based DSSS system assuming frequency selective channel that is composed of a primary channel and a number of secondary channels. In order to investigate the consequences of delays on signal transmission in these channels, this paper uses presentation of signals in discrete time domain and theoretical frame of discrete time stochastic processes. The channel is represented by a modified Saleh-Valenzuela model, which results in a number of delayed signal replicas at the receiver side. For the sake of explanation, the delays are assumed to remain in a chip interval. For the sake of comparison, the theoretical models and derived expressions are confirmed by the simulation of the system.