476 research outputs found
Source Coding When the Side Information May Be Delayed
For memoryless sources, delayed side information at the decoder does not
improve the rate-distortion function. However, this is not the case for more
general sources with memory, as demonstrated by a number of works focusing on
the special case of (delayed) feedforward. In this paper, a setting is studied
in which the encoder is potentially uncertain about the delay with which
measurements of the side information are acquired at the decoder. Assuming a
hidden Markov model for the sources, at first, a single-letter characterization
is given for the set-up where the side information delay is arbitrary and known
at the encoder, and the reconstruction at the destination is required to be
(near) lossless. Then, with delay equal to zero or one source symbol, a
single-letter characterization is given of the rate-distortion region for the
case where side information may be delayed or not, unbeknownst to the encoder.
The characterization is further extended to allow for additional information to
be sent when the side information is not delayed. Finally, examples for binary
and Gaussian sources are provided.Comment: revised July 201
Multipath streaming: fundamental limits and efficient algorithms
We investigate streaming over multiple links. A file is split into small
units called chunks that may be requested on the various links according to
some policy, and received after some random delay. After a start-up time called
pre-buffering time, received chunks are played at a fixed speed. There is
starvation if the chunk to be played has not yet arrived. We provide lower
bounds (fundamental limits) on the starvation probability of any policy. We
further propose simple, order-optimal policies that require no feedback. For
general delay distributions, we provide tractable upper bounds for the
starvation probability of the proposed policies, allowing to select the
pre-buffering time appropriately. We specialize our results to: (i) links that
employ CSMA or opportunistic scheduling at the packet level, (ii) links shared
with a primary user (iii) links that use fair rate sharing at the flow level.
We consider a generic model so that our results give insight into the design
and performance of media streaming over (a) wired networks with several paths
between the source and destination, (b) wireless networks featuring spectrum
aggregation and (c) multi-homed wireless networks.Comment: 24 page
Lecture Notes on Network Information Theory
These lecture notes have been converted to a book titled Network Information
Theory published recently by Cambridge University Press. This book provides a
significantly expanded exposition of the material in the lecture notes as well
as problems and bibliographic notes at the end of each chapter. The authors are
currently preparing a set of slides based on the book that will be posted in
the second half of 2012. More information about the book can be found at
http://www.cambridge.org/9781107008731/. The previous (and obsolete) version of
the lecture notes can be found at http://arxiv.org/abs/1001.3404v4/
Limited-Rate Channel State Feedback for Multicarrier Block Fading Channels
The capacity of a fading channel can be substantially increased by feeding
back channel state information from the receiver to the transmitter. With
limited-rate feedback what state information to feed back and how to encode it
are important open questions. This paper studies power loading in a
multicarrier system using no more than one bit of feedback per sub-channel. The
sub-channels can be correlated and full channel state information is assumed at
the receiver.Comment: Submitted to IEEE Transactions on Information Theor
Universal Estimation of Directed Information
Four estimators of the directed information rate between a pair of jointly
stationary ergodic finite-alphabet processes are proposed, based on universal
probability assignments. The first one is a Shannon--McMillan--Breiman type
estimator, similar to those used by Verd\'u (2005) and Cai, Kulkarni, and
Verd\'u (2006) for estimation of other information measures. We show the almost
sure and convergence properties of the estimator for any underlying
universal probability assignment. The other three estimators map universal
probability assignments to different functionals, each exhibiting relative
merits such as smoothness, nonnegativity, and boundedness. We establish the
consistency of these estimators in almost sure and senses, and derive
near-optimal rates of convergence in the minimax sense under mild conditions.
These estimators carry over directly to estimating other information measures
of stationary ergodic finite-alphabet processes, such as entropy rate and
mutual information rate, with near-optimal performance and provide alternatives
to classical approaches in the existing literature. Guided by these theoretical
results, the proposed estimators are implemented using the context-tree
weighting algorithm as the universal probability assignment. Experiments on
synthetic and real data are presented, demonstrating the potential of the
proposed schemes in practice and the utility of directed information estimation
in detecting and measuring causal influence and delay.Comment: 23 pages, 10 figures, to appear in IEEE Transactions on Information
Theor
Entropy and Quantum Kolmogorov Complexity: A Quantum Brudno's Theorem
In classical information theory, entropy rate and Kolmogorov complexity per
symbol are related by a theorem of Brudno. In this paper, we prove a quantum
version of this theorem, connecting the von Neumann entropy rate and two
notions of quantum Kolmogorov complexity, both based on the shortest qubit
descriptions of qubit strings that, run by a universal quantum Turing machine,
reproduce them as outputs.Comment: 26 pages, no figures. Reference to publication added: published in
the Communications in Mathematical Physics
(http://www.springerlink.com/content/1432-0916/
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