1,577 research outputs found
Outer Bounds on the Admissible Source Region for Broadcast Channels with Correlated Sources
Two outer bounds on the admissible source region for broadcast channels with
correlated sources are presented: the first one is strictly tighter than the
existing outer bound by Gohari and Anantharam while the second one provides a
complete characterization of the admissible source region in the case where the
two sources are conditionally independent given the common part. These outer
bounds are deduced from the general necessary conditions established for the
lossy source broadcast problem via suitable comparisons between the virtual
broadcast channel (induced by the source and the reconstructions) and the
physical broadcast channel
Separate Source-Channel Coding for Broadcasting Correlated Gaussians
The problem of broadcasting a pair of correlated Gaussian sources using
optimal separate source and channel codes is studied. Considerable performance
gains over previously known separate source-channel schemes are observed.
Although source-channel separation yields suboptimal performance in general, it
is shown that the proposed scheme is very competitive for any bandwidth
compression/expansion scenarios. In particular, for a high channel SNR
scenario, it can be shown to achieve optimal power-distortion tradeoff.Comment: 6 pages (with an extra proof), ISIT2011, to appea
Minimum Expected Distortion in Gaussian Layered Broadcast Coding with Successive Refinement
A transmitter without channel state information (CSI) wishes to send a
delay-limited Gaussian source over a slowly fading channel. The source is coded
in superimposed layers, with each layer successively refining the description
in the previous one. The receiver decodes the layers that are supported by the
channel realization and reconstructs the source up to a distortion. In the
limit of a continuum of infinite layers, the optimal power distribution that
minimizes the expected distortion is given by the solution to a set of linear
differential equations in terms of the density of the fading distribution. In
the optimal power distribution, as SNR increases, the allocation over the
higher layers remains unchanged; rather the extra power is allocated towards
the lower layers. On the other hand, as the bandwidth ratio b (channel uses per
source symbol) tends to zero, the power distribution that minimizes expected
distortion converges to the power distribution that maximizes expected
capacity. While expected distortion can be improved by acquiring CSI at the
transmitter (CSIT) or by increasing diversity from the realization of
independent fading paths, at high SNR the performance benefit from diversity
exceeds that from CSIT, especially when b is large.Comment: To appear in the proceedings of the 2007 IEEE International Symposium
on Information Theory, Nice, France, June 24-29, 200
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