7 research outputs found
Finite Blocklength Analysis of Gaussian Random Coding in AWGN Channels under Covert Constraint
This paper considers the achievability and converse bounds on the maximal
channel coding rate at a given blocklength and error probability over AWGN
channels. The problem stems from covert communication with Gaussian codewords.
By re-visiting [18], we first present new and more general achievability bounds
for random coding schemes under maximal or average probability of error
requirements. Such general bounds are then applied to covert communication in
AWGN channels where codewords are generated from Gaussian distribution while
meeting the maximal power constraint. Further comparison is made between the
new achievability bounds and existing one with deterministic codebooks.Comment: 18 page
The First and Second Order Asymptotics of Covert Communication over AWGN Channels
This paper investigates the asymptotics of the maximal throughput of
communication over AWGN channels by channel uses under a covert constraint
in terms of an upper bound of Kullback-Leibler divergence (KL
divergence). It is shown that the first and second order asymptotics of the
maximal throughput are and
, respectively.
The technique we use in the achievability is quasi--neighborhood
notion from information geometry. We prove that if the generating distribution
of the codebook is close to Dirac measure in the weak sense, then the
corresponding output distribution at the adversary satisfies covert constraint
in terms of most common divergences. This helps link the local differential
geometry of the distribution of noise with covert constraint. For the converse,
the optimality of Gaussian distribution for minimizing KL divergence under
second order moment constraint is extended from dimension to dimension .
It helps to establish the upper bound on the average power of the code to
satisfy the covert constraint, which further leads to the direct converse bound
in terms of covert metric
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
Digital Watermarking, Fingerprinting and Compression: An Information-Theoretic Perspective
The ease with which digital data can be duplicated and distributed over the media and the Internethas raised many concerns about copyright infringement.In many situations, multimedia data (e.g., images, music, movies, etc) are illegally circulated, thus violatingintellectual property rights. In an attempt toovercome this problem, watermarking has been suggestedin the literature as the most effective means for copyright protection and authentication. Watermarking is the procedure whereby information (pertaining to owner and/or copyright) is embedded into host data, such that it is:(i) hidden, i.e., not perceptually visible; and(ii) recoverable, even after a (possibly malicious) degradation of the protected work. In this thesis,we prove some theoretical results that establish the fundamental limits of a general class of watermarking schemes. The main focus of this thesis is the problem ofjoint watermarking and compression of images, whichcan be briefly described as follows: due to bandwidth or storage constraints, a watermarked image is distributed in quantized form, using bits per image dimension, and is subject to some additional degradation (possibly due to malicious attacks). The hidden message carries bits per image dimension. Our main result is the determination of the region of allowable rates , such that: (i) an average distortion constraint between the original and the watermarked/compressed image is satisfied, and (ii) the hidden message is detected from the degraded image with very high probability. Using notions from information theory, we prove coding theorems that establish the rate regionin the following cases: (a) general i.i.d. image distributions,distortion constraints and memoryless attacks, (b) memoryless attacks combined with collusion (for fingerprinting applications), and (c) general---not necessarily stationary or ergodic---Gaussian image distributions and attacks, and average quadratic distortion constraints. Moreover, we prove a multi-user version of a result by Costa on the capacity of a Gaussian channel with known interference at the encoder
One-shot achievability and converse bounds of Gaussian random coding in AWGN channels under covert constraint
The achievability and converse bounds on the throughput of covert communication over AWGN channels are investigated in this paper. By re-visiting [8], several new achievability bounds on maximal and average probability of error based on random coding scheme are presented, which leads to results on achievability bounds when the codewords are generated from Gaussian distribution and then selected from a subset under maximal power constraint. The bounds provide us the framework for analyzing the maximal throughput under covert constraint of total variation distance