30 research outputs found
Lossy Compression with Near-uniform Encoder Outputs
It is well known that lossless compression of a discrete memoryless source
with near-uniform encoder output is possible at a rate above its entropy if and
only if the encoder is randomized. This work focuses on deriving conditions for
near-uniform encoder output(s) in the Wyner-Ziv and the distributed lossy
compression problems. We show that in the Wyner-Ziv problem, near-uniform
encoder output and operation close to the WZ-rate limit is simultaneously
possible, whereas in the distributed lossy compression problem, jointly
near-uniform outputs is achievable in the interior of the distributed lossy
compression rate region if the sources share non-trivial G\'{a}cs-K\"{o}rner
common information.Comment: Submitted to the 2016 IEEE International Symposium on Information
Theory (11 Pages, 3 Figures
Strong Coordination over Multi-hop Line Networks
We analyze the problem of strong coordination over a multi-hop line network
in which the node initiating the coordination is a terminal network node. We
assume that each node has access to a certain amount of randomness that is
local to the node, and that the nodes share some common randomness, which are
used together with explicit hop-by-hop communication to achieve strong
coordination. We derive the trade-offs among the required rates of
communication on the network links, the rates of local randomness available to
network nodes, and the rate of common randomness to realize strong
coordination. We present an achievable coding scheme built using multiple
layers of channel resolvability codes, and establish several settings in which
this scheme is proven to offer the best possible trade-offs.Comment: 35 pages, 9 Figures, 4 Tables. A part of this work were published in
the 2015 IEEE Information Theory Workshop, and a part was accepted for
publication in the 50th Annual Conference on Information Sciences and System
Strong Coordination over Noisy Channels: Is Separation Sufficient?
We study the problem of strong coordination of actions of two agents and
that communicate over a noisy communication channel such that the actions
follow a given joint probability distribution. We propose two novel schemes for
this noisy strong coordination problem, and derive inner bounds for the
underlying strong coordination capacity region. The first scheme is a joint
coordination-channel coding scheme that utilizes the randomness provided by the
communication channel to reduce the local randomness required in generating the
action sequence at agent . The second scheme exploits separate coordination
and channel coding where local randomness is extracted from the channel after
decoding. Finally, we present an example in which the joint scheme is able to
outperform the separate scheme in terms of coordination rate.Comment: 9 pages, 4 figures. An extended version of a paper accepted for the
IEEE International Symposium on Information Theory (ISIT), 201
Strong Coordination over Noisy Channels: Is Separation Sufficient?
We study the problem of strong coordination of actions of two agents and
that communicate over a noisy communication channel such that the actions
follow a given joint probability distribution. We propose two novel schemes for
this noisy strong coordination problem, and derive inner bounds for the
underlying strong coordination capacity region. The first scheme is a joint
coordination-channel coding scheme that utilizes the randomness provided by the
communication channel to reduce the local randomness required in generating the
action sequence at agent . The second scheme exploits separate coordination
and channel coding where local randomness is extracted from the channel after
decoding. Finally, we present an example in which the joint scheme is able to
outperform the separate scheme in terms of coordination rate.Comment: 9 pages, 4 figures. An extended version of a paper accepted for the
IEEE International Symposium on Information Theory (ISIT), 201
An Equivalence Between Secure Network and Index Coding
We extend the equivalence between network coding and index coding by Effros,
El Rouayheb, and Langberg to the secure communication setting in the presence
of an eavesdropper. Specifically, we show that the most general versions of
secure network-coding setup by Chan and Grant and the secure index-coding setup
by Dau, Skachek, and Chee, which also include the randomised encoding setting,
are equivalent
On the Capacity Region for Secure Index Coding
We study the index coding problem in the presence of an eavesdropper, where
the aim is to communicate without allowing the eavesdropper to learn any single
message aside from the messages it may already know as side information. We
establish an outer bound on the underlying secure capacity region of the index
coding problem, which includes polymatroidal and security constraints, as well
as the set of additional decoding constraints for legitimate receivers. We then
propose a secure variant of the composite coding scheme, which yields an inner
bound on the secure capacity region of the index coding problem. For the
achievability of secure composite coding, a secret key with vanishingly small
rate may be needed to ensure that each legitimate receiver who wants the same
message as the eavesdropper, knows at least two more messages than the
eavesdropper. For all securely feasible index coding problems with four or
fewer messages, our numerical results establish the secure index coding
capacity region
Throughput and Latency in Finite-Buffer Line Networks
This work investigates the effect of finite buffer sizes on the throughput
capacity and packet delay of line networks with packet erasure links that have
perfect feedback. These performance measures are shown to be linked to the
stationary distribution of an underlying irreducible Markov chain that models
the system exactly. Using simple strategies, bounds on the throughput capacity
are derived. The work then presents two iterative schemes to approximate the
steady-state distribution of node occupancies by decoupling the chain to
smaller queueing blocks. These approximate solutions are used to understand the
effect of buffer sizes on throughput capacity and the distribution of packet
delay. Using the exact modeling for line networks, it is shown that the
throughput capacity is unaltered in the absence of hop-by-hop feedback provided
packet-level network coding is allowed. Finally, using simulations, it is
confirmed that the proposed framework yields accurate estimates of the
throughput capacity and delay distribution and captures the vital trends and
tradeoffs in these networks.Comment: 19 pages, 14 figures, accepted in IEEE Transactions on Information
Theor