20,290 research outputs found
Half-Duplex Relaying for the Multiuser Channel
This work focuses on studying the half-duplex (HD) relaying in the Multiple
Access Relay Channel (MARC) and the Compound Multiple Access Channel with a
Relay (cMACr). A generalized Quantize-and-Forward (GQF) has been proposed to
establish the achievable rate regions. Such scheme is developed based on the
variation of the Quantize-and-Forward (QF) scheme and single block with two
slots coding structure. The results in this paper can also be considered as a
significant extension of the achievable rate region of Half-Duplex Relay
Channel (HDRC). Furthermore, the rate regions based on GQF scheme is extended
to the Gaussian channel case. The scheme performance is shown through some
numerical examples.Comment: 7 pages, 4 figures, conference pape
Reliable Physical Layer Network Coding
When two or more users in a wireless network transmit simultaneously, their
electromagnetic signals are linearly superimposed on the channel. As a result,
a receiver that is interested in one of these signals sees the others as
unwanted interference. This property of the wireless medium is typically viewed
as a hindrance to reliable communication over a network. However, using a
recently developed coding strategy, interference can in fact be harnessed for
network coding. In a wired network, (linear) network coding refers to each
intermediate node taking its received packets, computing a linear combination
over a finite field, and forwarding the outcome towards the destinations. Then,
given an appropriate set of linear combinations, a destination can solve for
its desired packets. For certain topologies, this strategy can attain
significantly higher throughputs over routing-based strategies. Reliable
physical layer network coding takes this idea one step further: using
judiciously chosen linear error-correcting codes, intermediate nodes in a
wireless network can directly recover linear combinations of the packets from
the observed noisy superpositions of transmitted signals. Starting with some
simple examples, this survey explores the core ideas behind this new technique
and the possibilities it offers for communication over interference-limited
wireless networks.Comment: 19 pages, 14 figures, survey paper to appear in Proceedings of the
IEE
A Unified Approach for Network Information Theory
In this paper, we take a unified approach for network information theory and
prove a coding theorem, which can recover most of the achievability results in
network information theory that are based on random coding. The final
single-letter expression has a very simple form, which was made possible by
many novel elements such as a unified framework that represents various network
problems in a simple and unified way, a unified coding strategy that consists
of a few basic ingredients but can emulate many known coding techniques if
needed, and new proof techniques beyond the use of standard covering and
packing lemmas. For example, in our framework, sources, channels, states and
side information are treated in a unified way and various constraints such as
cost and distortion constraints are unified as a single joint-typicality
constraint.
Our theorem can be useful in proving many new achievability results easily
and in some cases gives simpler rate expressions than those obtained using
conventional approaches. Furthermore, our unified coding can strictly
outperform existing schemes. For example, we obtain a generalized
decode-compress-amplify-and-forward bound as a simple corollary of our main
theorem and show it strictly outperforms previously known coding schemes. Using
our unified framework, we formally define and characterize three types of
network duality based on channel input-output reversal and network flow
reversal combined with packing-covering duality.Comment: 52 pages, 7 figures, submitted to IEEE Transactions on Information
theory, a shorter version will appear in Proc. IEEE ISIT 201
Distributed Turbo-Like Codes for Multi-User Cooperative Relay Networks
In this paper, a distributed turbo-like coding scheme for wireless networks
with relays is proposed. We consider a scenario where multiple sources
communicate with a single destination with the help of a relay. The proposed
scheme can be regarded as of the decode-and-forward type. The relay decodes the
information from the sources and it properly combines and re-encodes them to
generate some extra redundancy, which is transmitted to the destination. The
amount of redundancy generated by the relay can simply be adjusted according to
requirements in terms of performance, throughput and/or power. At the
destination, decoding of the information of all sources is performed jointly
exploiting the redundancy provided by the relay in an iterative fashion. The
overall communication network can be viewed as a serially concatenated code.
The proposed distributed scheme achieves significant performance gains with
respect to the non-cooperation system, even for a very large number of users.
Furthermore, it presents a high flexibility in terms of code rate, block length
and number of users.Comment: Submitted to ICC 201
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