Ultra-wideband noise communication system using the transmitted reference technique with the time diversity is proposed for a covert data transmission through additive white Gaussian noise channel. Spectrum modulation of transmitted signals is performed as a result from linear superposition between the noise references and informative noise carriers delayed at the time diversity significantly exceeding the coherent time. The delayed noise carriers are multiplied by antipodal symbols at the same rate of binary data stream. Spectral power density of result noise signals is modulated by antipodal harmonic functions with the period in inverse proportion to diversity time delay. The time delay in the correlation receiver corresponds to the diversity time delay of informative noise signals. The correlation estimation problem appears in the case of data transmitting on the base of continuous noise carriers. Fluctuation analysis of correlation estimations with nonstationary trend at the data rate is performed. The intersystem jamming occurring in digital noise communications increase the correlation fluctuations at the receiver output and initiate asymptotic limitation of correlation performances without thermal noise in a wireless channel. Nonstationary trends of output correlation estimations become little if the informative time delay significantly exceeds the coherent times as noise carriers as additive white Gaussian noise. The forming of digital noise carriers is produced by the time window method. Simulation of noise communications shows that utilizing continuously noise carriers with time windows permits to decrease randomly fluctuations of correlation performances in the case when the product of noise signal bandwidth by bit duration exceeds one hundred units.
Read full abstract