Covert wireless communication with artificial noise generation

Covert communication conceals the transmission of the message from an attentive adversary. Recent work on the limits of covert communication in additive white Gaussian noise channels has demonstrated that a covert transmitter (Alice) can reliably transmit a maximum of O(√n) bits to a covert receiver (Bob) without being detected by an adversary (Warden Willie) in n channel uses. This paper focuses on the scenario where other 'friendly' nodes distributed according to a two-dimensional Poisson point process with density m are present. We propose a strategy where the friendly node closest to the adversary, without close coordination with Alice, produces artificial noise. We show that this method allows Alice to reliably and covertly send O(min {{n,m^gamma/2√n) bits to Bob in n channel uses, where γ is the path-loss exponent. We also consider a setting where there are N_w collaborating adversaries uniformly and randomly located in the environment and show that in n channel uses, Alice can reliably and covertly send O(min n,(m^gamma/2} √n/N_w ^γ) bits to Bob when γ >2 , and O(min {n,(m√n/N_w ²log² N_w)) when γ = 2. Conversely, we demonstrate that no higher covert throughput is possible for γ >2.