41,712 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
Distortion Exponent in MIMO Fading Channels with Time-Varying Source Side Information
Transmission of a Gaussian source over a time-varying multiple-input
multiple-output (MIMO) channel is studied under strict delay constraints.
Availability of a correlated side information at the receiver is assumed, whose
quality, i.e., correlation with the source signal, also varies over time. A
block-fading model is considered for the states of the time-varying channel and
the time-varying side information; and perfect state information at the
receiver is assumed, while the transmitter knows only the statistics. The high
SNR performance, characterized by the \textit{distortion exponent}, is studied
for this joint source-channel coding problem. An upper bound is derived and
compared with lowers based on list decoding, hybrid digital-analog
transmission, as well as multi-layer schemes which transmit successive
refinements of the source, relying on progressive and superposed transmission
with list decoding. The optimal distortion exponent is characterized for the
single-input multiple-output (SIMO) and multiple-input single-output (MISO)
scenarios by showing that the distortion exponent achieved by multi-layer
superpositon encoding with joint decoding meets the proposed upper bound. In
the MIMO scenario, the optimal distortion exponent is characterized in the low
bandwidth ratio regime, and it is shown that the multi-layer superposition
encoding performs very close to the upper bound in the high bandwidth expansion
regime.Comment: Submitted to IEEE Transactions on Information Theor
Joint Source-Channel Cooperative Transmission over Relay-Broadcast Networks
Reliable transmission of a discrete memoryless source over a multiple-relay
relay-broadcast network is considered. Motivated by sensor network
applications, it is assumed that the relays and the destinations all have
access to side information correlated with the underlying source signal. Joint
source-channel cooperative transmission is studied in which the relays help the
transmission of the source signal to the destinations by using both their
overheard signals, as in the classical channel cooperation scenario, as well as
the available correlated side information. Decode-and-forward (DF) based
cooperative transmission is considered in a network of multiple relay terminals
and two different achievability schemes are proposed: i) a regular encoding and
sliding-window decoding scheme without explicit source binning at the encoder,
and ii) a semi-regular encoding and backward decoding scheme with binning based
on the side information statistics. It is shown that both of these schemes lead
to the same source-channel code rate, which is shown to be the "source-channel
capacity" in the case of i) a physically degraded relay network in which the
side information signals are also degraded in the same order as the channel;
and ii) a relay-broadcast network in which all the terminals want to
reconstruct the source reliably, while at most one of them can act as a relay.Comment: Submitted to IEEE Transactions on Information Theory, 201
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Distributed video coding in wireless multimedia sensor network for multimedia broadcasting
Recently the development of Distributed Video Coding (DVC) has provided the promising theory
support to realize the infrastructure of Wireless Multimedia Sensor Network (WMSN), which composed of autonomous hardware for capturing and transmission of quality audio-visual content. The implementation of DVC in WMSN can better solve the problem of energy constraint of the sensor nodes due to the benefit of lower computational encoder in DVC. In this paper, a practical DVC scheme, pixel-domain Wyner-Ziv(PDWZ) video
coding, with slice structure and adaptive rate selection(ARS) is proposed to solve the certain problems when applying DVC into WMSN. Firstly, the proposed slice structure in PDWZ has extended the feasibility of PDWZ to work with any interleaver size used in Slepian-wolf turbo codec for heterogeneous applications. Meanwhile,
based on the slice structure, an adaptive code rate selection has been proposed aiming at reduce the system delay occurred in feedback request. The simulation results clearly showed the enhancement in R-D performance and perceptual quality. It also can be observed that system delay caused by frequent feedback is greatly reduced, which gives a promising support for WMSN with low latency and facilitates the QoS management
Lists that are smaller than their parts: A coding approach to tunable secrecy
We present a new information-theoretic definition and associated results,
based on list decoding in a source coding setting. We begin by presenting
list-source codes, which naturally map a key length (entropy) to list size. We
then show that such codes can be analyzed in the context of a novel
information-theoretic metric, \epsilon-symbol secrecy, that encompasses both
the one-time pad and traditional rate-based asymptotic metrics, but, like most
cryptographic constructs, can be applied in non-asymptotic settings. We derive
fundamental bounds for \epsilon-symbol secrecy and demonstrate how these bounds
can be achieved with MDS codes when the source is uniformly distributed. We
discuss applications and implementation issues of our codes.Comment: Allerton 2012, 8 page
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