Anotace:
A covert communication system is proposed in this study, in which a~ non-zero mean Gaussian sequence is used as a~ random carrier and its mean is modulated by a~ covert binary bit. The aperiodic transmitted signal exhibits the same statistical characteristics as the ambient noise to confuse an~ eavesdropper. The received signal is multiplied with the pseudo-random sequence synchronized with the transmitter to recover these positive and negative mean Gaussian sequence. The sample mean estimator and hard decision are used to determine the covert message, and accordingly, theoretical bit error rate in additive white Gaussian noise channel is also derived. Simulation results are very consistent with the theoretical derivation. The proposed system works in the physical layer with the advantages of simple structure, strong concealment, good BER performance and very suitable for low-cost, resource-limited and low-rate transmission devices.