14,812 research outputs found
Capacity Region of Finite State Multiple-Access Channel with Delayed State Information at the Transmitters
A single-letter characterization is provided for the capacity region of
finite-state multiple access channels. The channel state is a Markov process,
the transmitters have access to delayed state information, and channel state
information is available at the receiver. The delays of the channel state
information are assumed to be asymmetric at the transmitters. We apply the
result to obtain the capacity region for a finite-state Gaussian MAC, and for a
finite-state multiple-access fading channel. We derive power control strategies
that maximize the capacity region for these channels
The Capacity of the Gaussian Cooperative Two-user Multiple Access Channel to within a Constant Gap
The capacity region of the cooperative two-user Multiple Access Channel (MAC)
in Gaussian noise is determined to within a constant gap for both the
Full-Duplex (FD) and Half-Duplex (HD) case. The main contributions are: (a) for
both FD and HD: unilateral cooperation suffices to achieve capacity to within a
constant gap where only the user with the strongest link to the destination
needs to engage in cooperation, (b) for both FD and HD: backward joint decoding
is not necessary to achieve capacity to within a constant gap, and (c) for HD:
time sharing between the case where the two users do not cooperate and the case
where the user with the strongest link to the destination acts as pure relay
for the other user suffices to achieve capacity to within a constant gap. These
findings show that simple achievable strategies are approximately optimal for
all channel parameters with interesting implications for practical cooperative
schemes.Comment: Submitted to the 2013 IEEE International Conference on Communications
(ICC 2013
Capacity Theorems for Quantum Multiple Access Channels
We consider quantum channels with two senders and one receiver. For an
arbitrary such channel, we give multi-letter characterizations of two different
two-dimensional capacity regions. The first region characterizes the rates at
which it is possible for one sender to send classical information while the
other sends quantum information. The second region gives the rates at which
each sender can send quantum information. We give an example of a channel for
which each region has a single-letter description, concluding with a
characterization of the rates at which each user can simultaneously send
classical and quantum information.Comment: 5 pages. Conference version of quant-ph/0501045, to appear in the
proceedings of the IEEE International Symposium on Information Theory,
Adelaide, Australia, 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/
Interference Mitigation in Large Random Wireless Networks
A central problem in the operation of large wireless networks is how to deal
with interference -- the unwanted signals being sent by transmitters that a
receiver is not interested in. This thesis looks at ways of combating such
interference.
In Chapters 1 and 2, we outline the necessary information and communication
theory background, including the concept of capacity. We also include an
overview of a new set of schemes for dealing with interference known as
interference alignment, paying special attention to a channel-state-based
strategy called ergodic interference alignment.
In Chapter 3, we consider the operation of large regular and random networks
by treating interference as background noise. We consider the local performance
of a single node, and the global performance of a very large network.
In Chapter 4, we use ergodic interference alignment to derive the asymptotic
sum-capacity of large random dense networks. These networks are derived from a
physical model of node placement where signal strength decays over the distance
between transmitters and receivers. (See also arXiv:1002.0235 and
arXiv:0907.5165.)
In Chapter 5, we look at methods of reducing the long time delays incurred by
ergodic interference alignment. We analyse the tradeoff between reducing delay
and lowering the communication rate. (See also arXiv:1004.0208.)
In Chapter 6, we outline a problem that is equivalent to the problem of
pooled group testing for defective items. We then present some new work that
uses information theoretic techniques to attack group testing. We introduce for
the first time the concept of the group testing channel, which allows for
modelling of a wide range of statistical error models for testing. We derive
new results on the number of tests required to accurately detect defective
items, including when using sequential `adaptive' tests.Comment: PhD thesis, University of Bristol, 201
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