Differentially coherent information transmission based on chaotic radio pulses

Subject of the study. Differentially coherent information transmission scheme using chaotic signals as carriers – DCSK (Differential Chaos Shift Keying) was proposed as an alternative to communication systems based on chaotic synchronization. It is resistant to noise and other disturbances at the same level as classic transmission systems based on regular signals. However the requirement of using long time delay lines makes difficult practical implementation of wireless communication systems based on DCSK. A differentially coherent data transmission scheme using chaotic signals as information carriers is considered in the given paper. The scheme includes delay elements only with short duration, which simplifies its practical implementation in microwave frequency ranges in comparison with known analogs. Methods. Computer based simulation of the transmission process was carried out in Matlab environment. Simulation model is described by a system of differential-difference equations. The variables of the system of equations represent the signal at various points of the circuit during the transmission of information. Analytical estimation of noise immunity for channels with white noise and of noise immunity as the function of processing gain are given. Results. It is shown that for small values of processing gain the scheme is affected by its own noise, which complicates its operation even in the absence of external noise. However, its efficiency dramatically increases with the use of ultra-wideband and hyper-wideband signals with big processing gain up-to 106. At such processing gain values stable reception of transmitted pulses can be provided from under noise even with signal-to-noise ratio around $-20$ dB. Discussion. An analysis of the results shows that in the proposed differentially-coherent transmission scheme based on chaotic radio pulses as information carriers there is no problem with the requirement of using long-duration delays, which is critical for DCSK-based scheme. In the considered scheme only short durations delays are used. This radically simplifies practical realization of the scheme in microwave frequency ranges.