Limits of Covert Communication on Two-Hop AWGN Channels

Covert communication aims to achieve secure communications among legitimate network nodes by hiding the existence of the transmission in the first place. Previous work on covert communication mainly focus on the performance analysis of single hop systems, while the performance analysis on two-hop systems remains largely unknown. This paper, for the first time, focuses on the maximum throughput analysis of a two-hop wireless system where the source only communicates with the destination via a relay node. The hypothesis testing problem is first developed to model the probability of false alarms and missed detections at the warden in a two-hop system. Based on the designed hypothesis testing problem, we then conduct theoretical analysis on the maximum throughput of the two-hop system. The results show that the transmitter can communicate with the receiver under a certain detection probability less than a constant is an element of for any is an element of > 0, when the throughput is limited as O(root n) bits in n channel uses. Finally, we conducted analysis to show that this result can be extended to a multi-hop system to ensure a low probability of detection communication.