Covert Communication in Continuous-Time Systems

TL;DR

This paper investigates covert communication in continuous-time AWGN channels, demonstrating that O(WT) bits can be covertly transmitted in T seconds with or without knowledge of the Willie channel, extending discrete-time results.

Contribution

It establishes the feasibility of covert communication directly in continuous-time channels and provides constructions for reliable, undetectable transmission under different channel knowledge scenarios.

Findings

O(WT) bits can be covertly transmitted in T seconds

Achieves reliable covert communication in continuous-time AWGN channels

Works for both known and unknown path-loss scenarios

Abstract

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.