2,100 research outputs found
The Multi-Sender Multicast Index Coding
We focus on the following instance of an index coding problem, where a set of
receivers are required to decode multiple messages, whilst each knows one of
the messages a priori. In particular, here we consider a generalized setting
where they are multiple senders, each sender only knows a subset of messages,
and all senders are required to collectively transmit the index code. For a
single sender, Ong and Ho (ICC, 2012) have established the optimal index
codelength, where the lower bound was obtained using a pruning algorithm. In
this paper, the pruning algorithm is simplified, and used in conjunction with
an appending technique to give a lower bound to the multi-sender case. An upper
bound is derived based on network coding. While the two bounds do not match in
general, for the special case where no two senders know any message bit in
common, the bounds match, giving the optimal index codelength. The results are
derived based on graph theory, and are expressed in terms of strongly connected
components.Comment: This is an extended version of the same-titled paper accepted and to
be presented at the IEEE International Symposium on Information Theory
(ISIT), Istanbul, in July 201
The Single-Uniprior Index-Coding Problem: The Single-Sender Case and The Multi-Sender Extension
Index coding studies multiterminal source-coding problems where a set of
receivers are required to decode multiple (possibly different) messages from a
common broadcast, and they each know some messages a priori. In this paper, at
the receiver end, we consider a special setting where each receiver knows only
one message a priori, and each message is known to only one receiver. At the
broadcasting end, we consider a generalized setting where there could be
multiple senders, and each sender knows a subset of the messages. The senders
collaborate to transmit an index code. This work looks at minimizing the number
of total coded bits the senders are required to transmit. When there is only
one sender, we propose a pruning algorithm to find a lower bound on the optimal
(i.e., the shortest) index codelength, and show that it is achievable by linear
index codes. When there are two or more senders, we propose an appending
technique to be used in conjunction with the pruning technique to give a lower
bound on the optimal index codelength; we also derive an upper bound based on
cyclic codes. While the two bounds do not match in general, for the special
case where no two distinct senders know any message in common, the bounds
match, giving the optimal index codelength. The results are expressed in terms
of strongly connected components in directed graphs that represent the
index-coding problems.Comment: Author final manuscrip
Cache-Aided Coded Multicast for Correlated Sources
The combination of edge caching and coded multicasting is a promising
approach to improve the efficiency of content delivery over cache-aided
networks. The global caching gain resulting from content overlap distributed
across the network in current solutions is limited due to the increasingly
personalized nature of the content consumed by users. In this paper, the
cache-aided coded multicast problem is generalized to account for the
correlation among the network content by formulating a source compression
problem with distributed side information. A correlation-aware achievable
scheme is proposed and an upper bound on its performance is derived. It is
shown that considerable load reductions can be achieved, compared to state of
the art correlation-unaware schemes, when caching and delivery phases
specifically account for the correlation among the content files.Comment: In proceeding of IEEE International Symposium on Turbo Codes and
Iterative Information Processing (ISTC), 201
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Effective video multicast over wireless internet
With the rapid growth of wireless networks and great success of Internet video, wireless video services are expected to be widely deployed in the near future. As different types of wireless networks are converging into all IP networks, i.e., the Internet, it is important to study video delivery over the wireless Internet. This paper proposes a novel end-system based adaptation protocol calledWireless Hybrid Adaptation Layered Multicast (WHALM) protocol for layered video multicast over wireless Internet. In WHALM the sender dynamically collects bandwidth distribution from the receivers and uses an optimal layer rate allocation mechanism to reduce the mismatches between the coarse-grained layer subscription levels and the heterogeneous and dynamic rate requirements from the receivers, thus maximizing the degree of satisfaction of all the receivers in a multicast session. Based on sampling theory and theory of probability, we reduce the required number of bandwidth feedbacks to a reasonable degree and use a scalable feedback mechanism to control the feedback process practically. WHALM is also tuned to perform well in wireless networks by integrating an end-to-end loss differentiation algorithm (LDA) to differentiate error losses from congestion losses at the receiver side. With a series of simulation experiments over NS platform, WHALM has been proved to be able to greatly improve the degree of satisfaction of all the receivers while avoiding congestion collapse on the wireless Internet
Broadcast Caching Networks with Two Receivers and Multiple Correlated Sources
The correlation among the content distributed across a cache-aided broadcast
network can be exploited to reduce the delivery load on the shared wireless
link. This paper considers a two-user three-file network with correlated
content, and studies its fundamental limits for the worst-case demand. A class
of achievable schemes based on a two-step source coding approach is proposed.
Library files are first compressed using Gray-Wyner source coding, and then
cached and delivered using a combination of correlation-unaware cache-aided
coded multicast schemes. The second step is interesting in its own right and
considers a multiple-request caching problem, whose solution requires coding in
the placement phase. A lower bound on the optimal peak rate-memory trade-off is
derived, which is used to evaluate the performance of the proposed scheme. It
is shown that for symmetric sources the two-step strategy achieves the lower
bound for large cache capacities, and it is within half of the joint entropy of
two of the sources conditioned on the third source for all other cache sizes.Comment: in Proceedings of Asilomar Conference on Signals, Systems and
Computers, Pacific Grove, California, November 201
A Novel Network Coded Parallel Transmission Framework for High-Speed Ethernet
Parallel transmission, as defined in high-speed Ethernet standards, enables
to use less expensive optoelectronics and offers backwards compatibility with
legacy Optical Transport Network (OTN) infrastructure. However, optimal
parallel transmission does not scale to large networks, as it requires
computationally expensive multipath routing algorithms to minimize differential
delay, and thus the required buffer size, optimize traffic splitting ratio, and
ensure frame synchronization. In this paper, we propose a novel framework for
high-speed Ethernet, which we refer to as network coded parallel transmission,
capable of effective buffer management and frame synchronization without the
need for complex multipath algorithms in the OTN layer. We show that using
network coding can reduce the delay caused by packet reordering at the
receiver, thus requiring a smaller overall buffer size, while improving the
network throughput. We design the framework in full compliance with high-speed
Ethernet standards specified in IEEE802.3ba and present solutions for network
encoding, data structure of coded parallel transmission, buffer management and
decoding at the receiver side. The proposed network coded parallel transmission
framework is simple to implement and represents a potential major breakthrough
in the system design of future high-speed Ethernet.Comment: 6 pages, 8 figures, Submitted to Globecom201
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