A novel modulation method for secure digital communications

We present a new digital modulation technique that introduces covertness in digital communications. The basic principle is to transmit realizations of a stochastic process in such a manner that the transmitted waveform appears noise-like. In this paper, we have chosen to express the transmitted waveform in a subspace formalism. This allows for an elegant geometrical interpretation of the waveform, and it naturally suggests a simple and accurate matched subspace detector for the receiver. The technique is demonstrated by numerical simulations, and a comparison with an optimal Neyman-Pearson detector shows that our simple subspace detector yields a high-quality and reliable receiver for the modulated signal.