Covert Communication in Continuous-Time Systems
This addresses the covert communication problem for secure transmission scenarios, but it is incremental as it extends prior discrete-time models to continuous-time.
The paper tackles the problem of covert communication in continuous-time systems, establishing that O(WT) information bits can be transmitted covertly and reliably from Alice to Bob in T seconds for scenarios with known or unknown path-loss between Alice and Willie.
Recent works have considered the ability of transmitter Alice to communicate reliably to receiver Bob without being detected by warden Willie. These works generally assume a standard discrete-time model. But the assumption of a discrete-time model in standard communication scenarios is often predicated on its equivalence to a continuous-time model, which has not been established for the covert communications problem. Here, we consider the continuous-time channel directly and study if efficient covert communication can still be achieved. We assume that an uninformed jammer is present to assist Alice, and we consider additive white Gaussian noise (AWGN) channels between all parties. For a channel with approximate bandwidth W, we establish constructions such that O(WT) information bits can be transmitted covertly and reliably from Alice to Bob in T seconds for two separate scenarios: 1) when the path-loss between Alice and Willie is known; and 2) when the path-loss between Alice and Willie is unknown.