Robust Power Allocation in Covert Communication: Imperfect CDI

The study of the fundamental limits covert communications, where a transmitter Alice wants to send information desired recipient Bob without detection that transmission by an attentive and capable warden Willie, has emerged recently as topic great research interest. Previous work assumed distribution multipath fading on channel, which we term channel (CDI), is known Alice, hence facilitating her characterization Willie's capabilities detect signal. However, in practice, Willie tends be passive environment heterogeneous, implying lack signaling interchange between makes it difficult if not impossible for estimate CDI exactly provide covertness guarantees. In this paper, address issue developing communication schemes various assumptions Alice's imperfect CDI: 1) when knows within some distance nominal distribution; 2) only mean variance are available; 3) complex Gaussian but unknown. each case, formulate new optimization problems find power allocations maximize rate subject requirement under uncertain CDI. Moreover, may able or faced with error estimation, investigate two these issues. Numerical results presented compare proposed from aspects, attaining desirable system performance.