260 research outputs found
Strong Converse Theorems for Classes of Multimessage Multicast Networks: A R\'enyi Divergence Approach
This paper establishes that the strong converse holds for some classes of
discrete memoryless multimessage multicast networks (DM-MMNs) whose
corresponding cut-set bounds are tight, i.e., coincide with the set of
achievable rate tuples. The strong converse for these classes of DM-MMNs
implies that all sequences of codes with rate tuples belonging to the exterior
of the cut-set bound have average error probabilities that necessarily tend to
one (and are not simply bounded away from zero). Examples in the classes of
DM-MMNs include wireless erasure networks, DM-MMNs consisting of independent
discrete memoryless channels (DMCs) as well as single-destination DM-MMNs
consisting of independent DMCs with destination feedback. Our elementary proof
technique leverages properties of the R\'enyi divergence.Comment: Submitted to IEEE Transactions on Information Theory, Jul 18, 2014.
Revised on Jul 31, 201
Cooperative Relay Broadcast Channels
The capacity regions are investigated for two relay broadcast channels
(RBCs), where relay links are incorporated into standard two-user broadcast
channels to support user cooperation. In the first channel, the Partially
Cooperative Relay Broadcast Channel, only one user in the system can act as a
relay and transmit to the other user through a relay link. An achievable rate
region is derived based on the relay using the decode-and-forward scheme. An
outer bound on the capacity region is derived and is shown to be tighter than
the cut-set bound. For the special case where the Partially Cooperative RBC is
degraded, the achievable rate region is shown to be tight and provides the
capacity region. Gaussian Partially Cooperative RBCs and Partially Cooperative
RBCs with feedback are further studied. In the second channel model being
studied in the paper, the Fully Cooperative Relay Broadcast Channel, both users
can act as relay nodes and transmit to each other through relay links. This is
a more general model than the Partially Cooperative RBC. All the results for
Partially Cooperative RBCs are correspondingly generalized to the Fully
Cooperative RBCs. It is further shown that the AWGN Fully Cooperative RBC has a
larger achievable rate region than the AWGN Partially Cooperative RBC. The
results illustrate that relaying and user cooperation are powerful techniques
in improving the capacity of broadcast channels.Comment: Submitted to the IEEE Transactions on Information Theory, July 200
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/
Cooperative Strategies for Simultaneous and Broadcast Relay Channels
Consider the \emph{simultaneous relay channel} (SRC) which consists of a set
of relay channels where the source wishes to transmit common and private
information to each of the destinations. This problem is recognized as being
equivalent to that of sending common and private information to several
destinations in presence of helper relays where each channel outcome becomes a
branch of the \emph{broadcast relay channel} (BRC). Cooperative schemes and
capacity region for a set with two memoryless relay channels are investigated.
The proposed coding schemes, based on \emph{Decode-and-Forward} (DF) and
\emph{Compress-and-Forward} (CF) must be capable of transmitting information
simultaneously to all destinations in such set.
Depending on the quality of source-to-relay and relay-to-destination
channels, inner bounds on the capacity of the general BRC are derived. Three
cases of particular interest are considered: cooperation is based on DF
strategy for both users --referred to as DF-DF region--, cooperation is based
on CF strategy for both users --referred to as CF-CF region--, and cooperation
is based on DF strategy for one destination and CF for the other --referred to
as DF-CF region--. These results can be seen as a generalization and hence
unification of previous works. An outer-bound on the capacity of the general
BRC is also derived. Capacity results are obtained for the specific cases of
semi-degraded and degraded Gaussian simultaneous relay channels. Rates are
evaluated for Gaussian models where the source must guarantee a minimum amount
of information to both users while additional information is sent to each of
them.Comment: 32 pages, 7 figures, To appear in IEEE Trans. on Information Theor
An upper bound on relaying over capacity based on channel simulation
The upper bound on the capacity of a 3-node discrete memoryless relay channel
is considered, where a source X wants to send information to destination Y with
the help of a relay Z. Y and Z are independent given X, and the link from Z to
Y is lossless with rate . A new inequality is introduced to upper-bound
the capacity when the encoding rate is beyond the capacities of both individual
links XY and XZ. It is based on generalization of the blowing-up lemma, linking
conditional entropy to decoding error, and channel simulation, to the case with
side information. The achieved upper-bound is strictly better than the
well-known cut-set bound in several cases when the latter is , with
being the channel capacity between X and Y. One particular case is
when the channel is statistically degraded, i.e., either Y is a statistically
degraded version of Z with respect to X, or Z is a statistically degraded
version of Y with respect to X. Moreover in this case, the bound is shown to be
explicitly computable. The binary erasure channel is analyzed in detail and
evaluated numerically.Comment: Submitted to IEEE Transactions on Information Theory, 21 pages, 6
figure
Capacity Theorems for the Fading Interference Channel with a Relay and Feedback Links
Handling interference is one of the main challenges in the design of wireless
networks. One of the key approaches to interference management is node
cooperation, which can be classified into two main types: relaying and
feedback. In this work we consider simultaneous application of both cooperation
types in the presence of interference. We obtain exact characterization of the
capacity regions for Rayleigh fading and phase fading interference channels
with a relay and with feedback links, in the strong and very strong
interference regimes. Four feedback configurations are considered: (1) feedback
from both receivers to the relay, (2) feedback from each receiver to the relay
and to one of the transmitters (either corresponding or opposite), (3) feedback
from one of the receivers to the relay, (4) feedback from one of the receivers
to the relay and to one of the transmitters. Our results show that there is a
strong motivation for incorporating relaying and feedback into wireless
networks.Comment: Accepted to the IEEE Transactions on Information Theor
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