168 research outputs found

    Limits of Reliable Communication with Low Probability of Detection on AWGN Channels

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    We present a square root limit on the amount of information transmitted reliably and with low probability of detection (LPD) over additive white Gaussian noise (AWGN) channels. Specifically, if the transmitter has AWGN channels to an intended receiver and a warden, both with non-zero noise power, we prove that o(n)o(\sqrt{n}) bits can be sent from the transmitter to the receiver in nn channel uses while lower-bounding α+β≥1−ϵ\alpha+\beta\geq1-\epsilon for any ϵ>0\epsilon>0, where α\alpha and β\beta respectively denote the warden's probabilities of a false alarm when the sender is not transmitting and a missed detection when the sender is transmitting. Moreover, in most practical scenarios, a lower bound on the noise power on the channel between the transmitter and the warden is known and O(n)O(\sqrt{n}) bits can be sent in nn LPD channel uses. Conversely, attempting to transmit more than O(n)O(\sqrt{n}) bits either results in detection by the warden with probability one or a non-zero probability of decoding error at the receiver as n→∞n\rightarrow\infty.Comment: Major revision in v2. Context, esp. the relationship to steganography updated. Also, added discussion on secret key length. Results are unchanged from previous version. Minor revision in v3. Major revision in v4, Clarified derivations (adding appendix), also context, esp. relationship to previous work in communication updated. Results are unchanged from previous revision

    Covert Communications with a Full-Duplex Receiver over Wireless Fading Channels

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    In this work, we propose a covert communication scheme where the transmitter attempts to hide its transmission to a full-duplex receiver, from a warden that is to detect this covert transmission using a radiometer. Specifically, we first derive the detection error rate at the warden, based on which the optimal detection threshold for its radiometer is analytically determined and its expected detection error rate over wireless fading channels is achieved in a closed-form expression. Our analysis indicates that the artificial noise deliberately produced by the receiver with a random transmit power, although causes self-interference, offers the capability of achieving a positive effective covert rate for any transmit power (can be infinity) subject to any given covertness requirement on the expected detection error rate. This work is the first study on the use of the full-duplex receiver with controlled artificial noise for achieving covert communications and invites further investigation in this regard.ARC Discovery Projects Grant DP15010390
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