2,527 research outputs found
Slepian-Wolf Coding for Broadcasting with Cooperative Base-Stations
We propose a base-station (BS) cooperation model for broadcasting a discrete
memoryless source in a cellular or heterogeneous network. The model allows the
receivers to use helper BSs to improve network performance, and it permits the
receivers to have prior side information about the source. We establish the
model's information-theoretic limits in two operational modes: In Mode 1, the
helper BSs are given information about the channel codeword transmitted by the
main BS, and in Mode 2 they are provided correlated side information about the
source. Optimal codes for Mode 1 use \emph{hash-and-forward coding} at the
helper BSs; while, in Mode 2, optimal codes use source codes from Wyner's
\emph{helper source-coding problem} at the helper BSs. We prove the optimality
of both approaches by way of a new list-decoding generalisation of [8, Thm. 6],
and, in doing so, show an operational duality between Modes 1 and 2.Comment: 16 pages, 1 figur
Complete Interference Mitigation Through Receiver-Caching in Wyner's Networks
We present upper and lower bounds on the per-user multiplexing gain (MG) of
Wyner's circular soft-handoff model and Wyner's circular full model with
cognitive transmitters and receivers with cache memories. The bounds are tight
for cache memories with prelog in the soft-handoff model and for
in the full model, where denotes the number of possibly
demanded files. In these cases the per-user MG of the two models is ,
the same as for non-interfering point-to-point links with caches at the
receivers. Large receiver cache-memories thus allow to completely mitigate
interference in these networks.Comment: Submitted to ITW 2016 in Cambridg
Source Coding Problems with Conditionally Less Noisy Side Information
A computable expression for the rate-distortion (RD) function proposed by
Heegard and Berger has eluded information theory for nearly three decades.
Heegard and Berger's single-letter achievability bound is well known to be
optimal for \emph{physically degraded} side information; however, it is not
known whether the bound is optimal for arbitrarily correlated side information
(general discrete memoryless sources). In this paper, we consider a new setup
in which the side information at one receiver is \emph{conditionally less
noisy} than the side information at the other. The new setup includes degraded
side information as a special case, and it is motivated by the literature on
degraded and less noisy broadcast channels. Our key contribution is a converse
proving the optimality of Heegard and Berger's achievability bound in a new
setting. The converse rests upon a certain \emph{single-letterization} lemma,
which we prove using an information theoretic telescoping identity {recently
presented by Kramer}. We also generalise the above ideas to two different
successive-refinement problems
The Finite Field Multi-Way Relay Channel with Correlated Sources: Beyond Three Users
The multi-way relay channel (MWRC) models cooperative communication networks
in which many users exchange messages via a relay. In this paper, we consider
the finite field MWRC with correlated messages. The problem is to find all
achievable rates, defined as the number of channel uses required per reliable
exchange of message tuple. For the case of three users, we have previously
established that for a special class of source distributions, the set of all
achievable rates can be found [Ong et al., ISIT 2010]. The class is specified
by an almost balanced conditional mutual information (ABCMI) condition. In this
paper, we first generalize the ABCMI condition to the case of more than three
users. We then show that if the sources satisfy the ABCMI condition, then the
set of all achievable rates is found and can be attained using a separate
source-channel coding architecture.Comment: Author's final version (to be presented at ISIT 2012
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