11 research outputs found
On Convergence Properties of Shannon Entropy
Convergence properties of Shannon Entropy are studied. In the differential
setting, it is shown that weak convergence of probability measures, or
convergence in distribution, is not enough for convergence of the associated
differential entropies. A general result for the desired differential entropy
convergence is provided, taking into account both compactly and uncompactly
supported densities. Convergence of differential entropy is also characterized
in terms of the Kullback-Liebler discriminant for densities with fairly general
supports, and it is shown that convergence in variation of probability measures
guarantees such convergence under an appropriate boundedness condition on the
densities involved. Results for the discrete setting are also provided,
allowing for infinitely supported probability measures, by taking advantage of
the equivalence between weak convergence and convergence in variation in this
setting.Comment: Submitted to IEEE Transactions on Information Theor
Sum-Rate Capacity for Symmetric Gaussian Multiple Access Channels with Feedback
The feedback sum-rate capacity is established for the symmetric -user
Gaussian multiple-access channel (GMAC). The main contribution is a converse
bound that combines the dependence-balance argument of Hekstra and Willems
(1989) with a variant of the factorization of a convex envelope of Geng and
Nair (2014). The converse bound matches the achievable sum-rate of the
Fourier-Modulated Estimate Correction strategy of Kramer (2002).Comment: 16 pages, 2 figures, published in International Symposium on
Information Theory (ISIT) 201
CSI-based versus RSS-based Secret-Key Generation under Correlated Eavesdropping
Physical-layer security (PLS) has the potential to strongly enhance the
overall system security as an alternative to or in combination with
conventional cryptographic primitives usually implemented at higher network
layers. Secret-key generation relying on wireless channel reciprocity is an
interesting solution as it can be efficiently implemented at the physical layer
of emerging wireless communication networks, while providing
information-theoretic security guarantees. In this paper, we investigate and
compare the secret-key capacity based on the sampling of the entire complex
channel state information (CSI) or only its envelope, the received signal
strength (RSS). Moreover, as opposed to previous works, we take into account
the fact that the eavesdropper's observations might be correlated and we
consider the high signal-to-noise ratio (SNR) regime where we can find simple
analytical expressions for the secret-key capacity. As already found in
previous works, we find that RSS-based secret-key generation is heavily
penalized as compared to CSI-based systems. At high SNR, we are able to
precisely and simply quantify this penalty: a halved pre-log factor and a
constant penalty of about 0.69 bit, which disappears as Eve's channel gets
highly correlated
On the tightness of Marton's regions for semi-additive broadcast channels
We study cost constrained side-information channels, where the cost function depends on a state which is known only to the encoder. In the additive noise case, we bound the capacity loss due to not knowing the cost state at the decoder and show that it is small under various assumptions, and goes to zero in the limit of weak noise. This model plays an important role in the (non-degraded) broadcast channel. In the semi-additive noise case, we bound the gap between the best known single letter achievable region and the true capacity region, using tools developed for the first problem. In the limit of weak noise, we show that the bounds coincide, thus we get the complete characterization of the capacity region
On the Capacity of Large-MIMO Block-Fading Channels
We characterize the capacity of Rayleigh block-fading multiple-input
multiple-output (MIMO) channels in the noncoherent setting where transmitter
and receiver have no a priori knowledge of the realizations of the fading
channel. We prove that unitary space-time modulation (USTM) is not
capacity-achieving in the high signal-to-noise ratio (SNR) regime when the
total number of antennas exceeds the coherence time of the fading channel
(expressed in multiples of the symbol duration), a situation that is relevant
for MIMO systems with large antenna arrays (large-MIMO systems). This result
settles a conjecture by Zheng & Tse (2002) in the affirmative. The
capacity-achieving input signal, which we refer to as Beta-variate space-time
modulation (BSTM), turns out to be the product of a unitary isotropically
distributed random matrix, and a diagonal matrix whose nonzero entries are
distributed as the square-root of the eigenvalues of a Beta-distributed random
matrix of appropriate size. Numerical results illustrate that using BSTM
instead of USTM in large-MIMO systems yields a rate gain as large as 13% for
SNR values of practical interest.Comment: To appear in IEEE Journal on Selected Areas in Communicatio
Stability of Bernstein's Theorem and Soft Doubling for Vector Gaussian Channels
The stability of Bernstein's characterization of Gaussian distributions is
extended to vectors by utilizing characteristic functions. Stability is used to
develop a soft doubling argument that establishes the optimality of Gaussian
vectors for certain communications channels with additive Gaussian noise,
including two-receiver broadcast channels. One novelty is that the argument
does not require the existence of distributions that achieve capacity
Entropy-based goodness-of-fit tests for multivariate distributions
Entropy is one of the most basic and significant descriptors of a probability distribution. It is still a commonly used measure of uncertainty and randomness in information theory and mathematical statistics. We study statistical inference for Shannon
and Rényi’s entropy-related functionals of multivariate Gaussian and Student-t distributions. This thesis investigates three themes. First, we provide a non-parametric
test of goodness-of-fit for a class of multivariate generalized Gaussian distributions
based on maximum entropy principle via using the k-th nearest neighbour (NN) distance estimator of the Shannon entropy. Its asymptotic unbiasedness and consistency
are demonstrated. Second, we show a class of estimators of the Rényi entropy based
on an independent identical distribution sample drawn from an unknown distribution f on R
m. We focus on the maximum Rényi entropy principle for multivariate
Student-t and Pearson type II distributions. We also consider the entropy-based test
for multivariate Student-t distribution using the k-th NN distances estimator of entropy and employ the properties of entropy estimators derived from NN distances.
Third, we introduce a new classes of unimodal rotational invariant directional distributions, which generalize von Mises-Fisher distribution. We propose three types of
distributions in which one of them represents the axial data. We provide all of the
formula together with a short computational study of parameter estimators for each
new type via the method of moments and method of maximum likelihood. We also
offer the goodness-of-fit test to detect that the sample entries follow one of the introduced generalized von Mises-Fisher distribution based on the maximum entropy
principle using the k-th NN distances estimator of Shannon entropy and to prove its L2 -consistence