OFDM Covert Communication System Based on the QC-LDPC and Symbol Spread Spectrum

As a new technology to solve wireless communication security problems, covert communication can not only hide the transmitted secret information, but also hide the communication process. Therefore, it has become a hot research issue in wireless communication security in recent years. Aiming at the problems of the square root law model in the practical process, this paper deduces and analyzes a constraint condition of the signal-to-noise ratio to measure the covert system. Thus, a covert communication model of OFDM system based on the combination of QC-LDPC and symbol spread spectrum is constructed. Through theoretical and simulation analysis methods, we respectively proved the Gaussian-like, low probability of detection characteristics of the model's radio frequency signal and the reliable communication performance of the system under low signal-to-noise ratio. It is proved that the model can successfully realize the covert communication with limited parameters.