339 research outputs found
Adaptive Delivery in Caching Networks
The problem of content delivery in caching networks is investigated for
scenarios where multiple users request identical files. Redundant user demands
are likely when the file popularity distribution is highly non-uniform or the
user demands are positively correlated. An adaptive method is proposed for the
delivery of redundant demands in caching networks. Based on the redundancy
pattern in the current demand vector, the proposed method decides between the
transmission of uncoded messages or the coded messages of [1] for delivery.
Moreover, a lower bound on the delivery rate of redundant requests is derived
based on a cutset bound argument. The performance of the adaptive method is
investigated through numerical examples of the delivery rate of several
specific demand vectors as well as the average delivery rate of a caching
network with correlated requests. The adaptive method is shown to considerably
reduce the gap between the non-adaptive delivery rate and the lower bound. In
some specific cases, using the adaptive method, this gap shrinks by almost 50%
for the average rate.Comment: 8 pages,8 figures. Submitted to IEEE transaction on Communications in
2015. A short version of this article was published as an IEEE Communications
Letter with DOI: 10.1109/LCOMM.2016.255814
Updating Content in Cache-Aided Coded Multicast
Motivated by applications to delivery of dynamically updated, but correlated
data in settings such as content distribution networks, and distributed file
sharing systems, we study a single source multiple destination network coded
multicast problem in a cache-aided network. We focus on models where the caches
are primarily located near the destinations, and where the source has no cache.
The source observes a sequence of correlated frames, and is expected to do
frame-by-frame encoding with no access to prior frames. We present a novel
scheme that shows how the caches can be advantageously used to decrease the
overall cost of multicast, even though the source encodes without access to
past data. Our cache design and update scheme works with any choice of network
code designed for a corresponding cache-less network, is largely decentralized,
and works for an arbitrary network. We study a convex relation of the
optimization problem that results form the overall cost function. The results
of the optimization problem determines the rate allocation and caching
strategies. Numerous simulation results are presented to substantiate the
theory developed.Comment: To Appear in IEEE Journal on Selected Areas in Communications:
Special Issue on Caching for Communication Systems and Network
Caching and Coded Multicasting: Multiple Groupcast Index Coding
The capacity of caching networks has received considerable attention in the
past few years. A particularly studied setting is the case of a single server
(e.g., a base station) and multiple users, each of which caches segments of
files in a finite library. Each user requests one (whole) file in the library
and the server sends a common coded multicast message to satisfy all users at
once. The problem consists of finding the smallest possible codeword length to
satisfy such requests. In this paper we consider the generalization to the case
where each user places requests. The obvious naive scheme consists
of applying times the order-optimal scheme for a single request, obtaining
a linear in scaling of the multicast codeword length. We propose a new
achievable scheme based on multiple groupcast index coding that achieves a
significant gain over the naive scheme. Furthermore, through an information
theoretic converse we find that the proposed scheme is approximately optimal
within a constant factor of (at most) .Comment: 5 pages, 1 figure, to appear in GlobalSIP14, Dec. 201
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