The Sound and the Fury: Hiding Communications in Noisy Wireless Networks with Interference Uncertainty
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Covert communication can prevent the opponent from knowing that a wireless communication has occurred. In the additive white Gaussian noise channels, a square root law is obtained and the result shows that Alice can reliably and covertly transmit O(√(n)) bits to Bob in n channel uses. If additional "friendly" node near the adversary can produce artificial noise to aid in hiding the communication, the covert throughput can be improved, i.e., Alice can covertly transmit O({n,λ^α/2√(n)}) bits to Bob over n uses of the channel (λ is the density of friendly nodes and α is the path loss exponent). In this paper, we consider the covert communication in noisy wireless networks, where potential transmitters form a stationary Poisson point process. Alice wishes to communicate covertly to Bob without being detected by a warden Willie. In this scenario, Bob and Willie not only experience the ambient noise, but also the aggregated interference. Our results show that uncertainty in interference experienced by Willie is beneficial to Alice. When the distance between Alice and Willie d_a,w=ω(n^δ/4) (δ=2/α is stability exponent), Alice can reliably and covertly transmit O(_2√(n)) bits to Bob in n channel uses, and there is no limitation on the transmit power of transmitters. Although the covert throughput is lower than the square root law and the friendly jamming scheme, the spatial throughput is higher. From the network perspective, the communications are hidden in "the sound and the fury" of noisy wireless networks, and what Willie sees is merely a "shadow" wireless network where he knows for certain that some nodes are transmitting, but he cannot catch anyone red-handed.
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