CASCADE and CREAM: Covert Communications Enhancement Based on Frequency Diverse Array

As a multi-antenna technology which is capable to beamform with respect to the angle and distance domain, frequency diverse array (FDA) is born to be a promising candidate to achieve two-dimensional wireless security. In this paper, we first investigate the potentials of FDA on enhancing covert communications performance. By introducing two performance metrics which are referred to as Covertness-Achieving SCheme under Anti-Eavesdropping District (CASCADE) and Covert Rate for a fixed Eavesdropping Area Measurement (CREAM), we exhaustively compare the FDA-assisted covert communications performance with its traditional phased array counterpart in two typical scenarios where there exists a clear district without the adversary near the legitimate receiver or not. Through theoretical analysis, the advantages of utilizing FDA on improving system covertness are fully validated, and the optimal covert rate are derived. Numerical simulations are also presented to verify our demonstration.