Performance of chaos-based communication systems under the influence of coexisting conventional spreadspectrum systems

This brief studies the performance of selected chaos-based systems which share their frequency bands with conventional spread-spectrum systems. Such a scenario may occur in normal practice when chaos-based systems are introduced while the conventional systems are still in operation. The particular chaos-based systems under study are the coherent chaos-shiftkeying system and the noncoherent differential chaos-shift-keying system, and the coexisting conventional system employs the standard direct-sequence spread-spectrum modulation scheme. Analytical expressions for the bit-error rates are derived in terms of system parameters such as spreading factor, chaotic signal power, conventional spread-spectrum signal power, and noise power spectral density. Finally, computer simulations are performed to verify the analytical findings.