324 research outputs found
Side-information Scalable Source Coding
The problem of side-information scalable (SI-scalable) source coding is
considered in this work, where the encoder constructs a progressive
description, such that the receiver with high quality side information will be
able to truncate the bitstream and reconstruct in the rate distortion sense,
while the receiver with low quality side information will have to receive
further data in order to decode. We provide inner and outer bounds for general
discrete memoryless sources. The achievable region is shown to be tight for the
case that either of the decoders requires a lossless reconstruction, as well as
the case with degraded deterministic distortion measures. Furthermore we show
that the gap between the achievable region and the outer bounds can be bounded
by a constant when square error distortion measure is used. The notion of
perfectly scalable coding is introduced as both the stages operate on the
Wyner-Ziv bound, and necessary and sufficient conditions are given for sources
satisfying a mild support condition. Using SI-scalable coding and successive
refinement Wyner-Ziv coding as basic building blocks, a complete
characterization is provided for the important quadratic Gaussian source with
multiple jointly Gaussian side-informations, where the side information quality
does not have to be monotonic along the scalable coding order. Partial result
is provided for the doubly symmetric binary source with Hamming distortion when
the worse side information is a constant, for which one of the outer bound is
strictly tighter than the other one.Comment: 35 pages, submitted to IEEE Transaction on Information Theor
Approximate Capacity of Gaussian Relay Networks
We present an achievable rate for general Gaussian relay networks. We show
that the achievable rate is within a constant number of bits from the
information-theoretic cut-set upper bound on the capacity of these networks.
This constant depends on the topology of the network, but not the values of the
channel gains. Therefore, we uniformly characterize the capacity of Gaussian
relay networks within a constant number of bits, for all channel parameters.Comment: This paper is submited to 2008 IEEE International Symposium on
Information Theory (ISIT 2008) -In the revised format the approximation gap
(\kappa) is sharpene
Nonintersecting Subspaces Based on Finite Alphabets
Two subspaces of a vector space are here called ``nonintersecting'' if they
meet only in the zero vector. The following problem arises in the design of
noncoherent multiple-antenna communications systems. How many pairwise
nonintersecting M_t-dimensional subspaces of an m-dimensional vector space V
over a field F can be found, if the generator matrices for the subspaces may
contain only symbols from a given finite alphabet A subseteq F? The most
important case is when F is the field of complex numbers C; then M_t is the
number of antennas. If A = F = GF(q) it is shown that the number of
nonintersecting subspaces is at most (q^m-1)/(q^{M_t}-1), and that this bound
can be attained if and only if m is divisible by M_t. Furthermore these
subspaces remain nonintersecting when ``lifted'' to the complex field. Thus the
finite field case is essentially completely solved. In the case when F = C only
the case M_t=2 is considered. It is shown that if A is a PSK-configuration,
consisting of the 2^r complex roots of unity, the number of nonintersecting
planes is at least 2^{r(m-2)} and at most 2^{r(m-1)-1} (the lower bound may in
fact be the best that can be achieved).Comment: 14 page
Increasing Throughput by Efficient Target Localization in WSN
The assumptions made for target localization in wireless sensor network is not up to date. Restricted equipment assets, vitality protection and clamor disturbance because of remote channel dispute and instrumentation commotion make new limitations on originators these days. In the proposed paper target localization system which is based on TDOA is discussed. At the point when an event is identified, every sensor having a place with a gathering computes an estimation of the objective's area. A MAC convention for remote sensor systems i.e. Occasion Based –Medium Access Control (EB-MAC) is produced, which is adjusted for occasion based frameworks that portrays target confinement frameworks. Besides, EB-MAC gave a dependable correspondence stage where high channel conflict was brought down while keeping up high throughpu
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