3,424 research outputs found
Limits of Reliable Communication with Low Probability of Detection on AWGN Channels
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 bits can be sent from the transmitter to the
receiver in channel uses while lower-bounding
for any , where and 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 bits can be sent in
LPD channel uses. Conversely, attempting to transmit more than
bits either results in detection by the warden with probability one or a
non-zero probability of decoding error at the receiver as .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 Wireless Communication with a Poisson Field of Interferers
In this paper, we study covert communication in wireless networks consisting
of a transmitter, Alice, an intended receiver, Bob, a warden, Willie, and a
Poisson field of interferers. Bob and Willie are subject to uncertain shot
noise due to the ambient signals from interferers in the network. With the aid
of stochastic geometry, we analyze the throughput of the covert communication
between Alice and Bob subject to given requirements on the covertness against
Willie and the reliability of decoding at Bob. We consider non-fading and
fading channels. We analytically obtain interesting findings on the impacts of
the density and the transmit power of the concurrent interferers on the covert
throughput. That is, the density and the transmit power of the interferers have
no impact on the covert throughput as long as the network stays in the
interference-limited regime, for both the non-fading and the fading cases. When
the interference is sufficiently small and comparable with the receiver noise,
the covert throughput increases as the density or the transmit power of the
concurrent interferers increases
Fundamental limits of quantum-secure covert optical sensing
We present a square root law for active sensing of phase of a single
pixel using optical probes that pass through a single-mode lossy thermal-noise
bosonic channel. Specifically, we show that, when the sensor uses an -mode
covert optical probe, the mean squared error (MSE) of the resulting estimator
scales as ; improving the
scaling necessarily leads to detection by the adversary with high probability.
We fully characterize this limit and show that it is achievable using laser
light illumination and a heterodyne receiver, even when the adversary captures
every photon that does not return to the sensor and performs arbitrarily
complex measurement as permitted by the laws of quantum mechanics.Comment: 13 pages, 1 figure, submitted to ISIT 201
Fundamental Limits of Communication with Low Probability of Detection
This paper considers the problem of communication over a discrete memoryless
channel (DMC) or an additive white Gaussian noise (AWGN) channel subject to the
constraint that the probability that an adversary who observes the channel
outputs can detect the communication is low. Specifically, the relative entropy
between the output distributions when a codeword is transmitted and when no
input is provided to the channel must be sufficiently small. For a DMC whose
output distribution induced by the "off" input symbol is not a mixture of the
output distributions induced by other input symbols, it is shown that the
maximum amount of information that can be transmitted under this criterion
scales like the square root of the blocklength. The same is true for the AWGN
channel. Exact expressions for the scaling constant are also derived.Comment: Version to appear in IEEE Transactions on Information Theory; minor
typos in v2 corrected. Part of this work was presented at ISIT 2015 in Hong
Kon
Capacity of a Nonlinear Optical Channel with Finite Memory
The channel capacity of a nonlinear, dispersive fiber-optic link is
revisited. To this end, the popular Gaussian noise (GN) model is extended with
a parameter to account for the finite memory of realistic fiber channels. This
finite-memory model is harder to analyze mathematically but, in contrast to
previous models, it is valid also for nonstationary or heavy-tailed input
signals. For uncoded transmission and standard modulation formats, the new
model gives the same results as the regular GN model when the memory of the
channel is about 10 symbols or more. These results confirm previous results
that the GN model is accurate for uncoded transmission. However, when coding is
considered, the results obtained using the finite-memory model are very
different from those obtained by previous models, even when the channel memory
is large. In particular, the peaky behavior of the channel capacity, which has
been reported for numerous nonlinear channel models, appears to be an artifact
of applying models derived for independent input in a coded (i.e., dependent)
scenario
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