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0807.3396
|
Universal Denoising of Discrete-time Continuous-Amplitude Signals
|
cs.IT cs.LG math.IT math.ST stat.TH
|
We consider the problem of reconstructing a discrete-time signal (sequence)
with continuous-valued components corrupted by a known memoryless channel. When
performance is measured using a per-symbol loss function satisfying mild
regularity conditions, we develop a sequence of denoisers that, although
independent of the distribution of the underlying `clean' sequence, is
universally optimal in the limit of large sequence length. This sequence of
denoisers is universal in the sense of performing as well as any sliding window
denoising scheme which may be optimized for the underlying clean signal. Our
results are initially developed in a ``semi-stochastic'' setting, where the
noiseless signal is an unknown individual sequence, and the only source of
randomness is due to the channel noise. It is subsequently shown that in the
fully stochastic setting, where the noiseless sequence is a stationary
stochastic process, our schemes universally attain optimum performance. The
proposed schemes draw from nonparametric density estimation techniques and are
practically implementable. We demonstrate efficacy of the proposed schemes in
denoising gray-scale images in the conventional additive white Gaussian noise
setting, with additional promising results for less conventional noise
distributions.
|
0807.3483
|
Implementing general belief function framework with a practical
codification for low complexity
|
cs.AI
|
In this chapter, we propose a new practical codification of the elements of
the Venn diagram in order to easily manipulate the focal elements. In order to
reduce the complexity, the eventual constraints must be integrated in the
codification at the beginning. Hence, we only consider a reduced hyper power
set $D_r^\Theta$ that can be $2^\Theta$ or $D^\Theta$. We describe all the
steps of a general belief function framework. The step of decision is
particularly studied, indeed, when we can decide on intersections of the
singletons of the discernment space no actual decision functions are easily to
use. Hence, two approaches are proposed, an extension of previous one and an
approach based on the specificity of the elements on which to decide. The
principal goal of this chapter is to provide practical codes of a general
belief function framework for the researchers and users needing the belief
function theory.
|
0807.3566
|
Stabilizer Quantum Codes: A Unified View based on Forney-style Factor
Graphs
|
quant-ph cs.IT math.IT
|
Quantum error-correction codes (QECCs) are a vital ingredient of quantum
computation and communication systems. In that context it is highly desirable
to design QECCs that can be represented by graphical models which possess a
structure that enables efficient and close-to-optimal iterative decoding. In
this paper we focus on stabilizer QECCs, a class of QECCs whose construction is
rendered non-trivial by the fact that the stabilizer label code, a code that is
associated with a stabilizer QECC, has to satisfy a certain self-orthogonality
condition. In order to design graphical models of stabilizer label codes that
satisfy this condition, we extend a duality result for Forney-style factor
graphs (FFGs) to the stabilizer label code framework. This allows us to
formulate a simple FFG design rule for constructing stabilizer label codes, a
design rule that unifies several earlier stabilizer label code constructions.
|
0807.3574
|
Mode Switching for MIMO Communication Based on Delay and Channel
Quantization
|
cs.IT math.IT
|
This paper has been withdrawn by the author as a major revision is made and a
new version is uploaded at arXiv:0812.3120
|
0807.3582
|
Error Correction Capability of Column-Weight-Three LDPC Codes: Part II
|
cs.IT math.IT
|
The relation between the girth and the error correction capability of
column-weight-three LDPC codes is investigated. Specifically, it is shown that
the Gallager A algorithm can correct $g/2-1$ errors in $g/2$ iterations on a
Tanner graph of girth $g \geq 10$.
|
0807.3590
|
Counting the Faces of Randomly-Projected Hypercubes and Orthants, with
Applications
|
math.MG cs.IT math.IT math.OC math.PR
|
Let $A$ be an $n$ by $N$ real valued random matrix, and $\h$ denote the
$N$-dimensional hypercube. For numerous random matrix ensembles, the expected
number of $k$-dimensional faces of the random $n$-dimensional zonotope $A\h$
obeys the formula $E f_k(A\h) /f_k(\h) = 1-P_{N-n,N-k}$, where $P_{N-n,N-k}$ is
a fair-coin-tossing probability. The formula applies, for example, where the
columns of $A$ are drawn i.i.d. from an absolutely continuous symmetric
distribution. The formula exploits Wendel's Theorem\cite{We62}.
Let $\po$ denote the positive orthant; the expected number of $k$-faces of
the random cone$A \po$ obeys $ {\cal E} f_k(A\po) /f_k(\po) = 1 - P_{N-n,N-k}$.
The formula applies to numerous matrix ensembles, including those with iid
random columns from an absolutely continuous, centrally symmetric distribution.
There is an asymptotically sharp threshold in the behavior of face counts of
the projected hypercube; thresholds known for projecting the simplex and the
cross-polytope, occur at very different locations. We briefly consider face
counts of the projected orthant when $A$ does not have mean zero; these do
behave similarly to those for the projected simplex. We consider non-random
projectors of the orthant; the 'best possible' $A$ is the one associated with
the first $n$ rows of the Fourier matrix.
These geometric face-counting results have implications for signal
processing, information theory, inverse problems, and optimization. Most of
these flow in some way from the fact that face counting is related to
conditions for uniqueness of solutions of underdetermined systems of linear
equations.
|
0807.3593
|
An outer bound for 2-receiver discrete memoryless broadcast channels
|
cs.IT math.IT
|
An outer bound to the two-receiver discrete memoryless broadcast channel is
presented. We compare it to the known outer bounds and show that the outer
bound presented is at least as tight as the existing bounds.
|
0807.3622
|
TuLiPA: Towards a Multi-Formalism Parsing Environment for Grammar
Engineering
|
cs.CL
|
In this paper, we present an open-source parsing environment (Tuebingen
Linguistic Parsing Architecture, TuLiPA) which uses Range Concatenation Grammar
(RCG) as a pivot formalism, thus opening the way to the parsing of several
mildly context-sensitive formalisms. This environment currently supports
tree-based grammars (namely Tree-Adjoining Grammars, TAG) and Multi-Component
Tree-Adjoining Grammars with Tree Tuples (TT-MCTAG)) and allows computation not
only of syntactic structures, but also of the corresponding semantic
representations. It is used for the development of a tree-based grammar for
German.
|
0807.3669
|
A new probabilistic transformation of belief mass assignment
|
cs.AI
|
In this paper, we propose in Dezert-Smarandache Theory (DSmT) framework, a
new probabilistic transformation, called DSmP, in order to build a subjective
probability measure from any basic belief assignment defined on any model of
the frame of discernment. Several examples are given to show how the DSmP
transformation works and we compare it to main existing transformations
proposed in the literature so far. We show the advantages of DSmP over
classical transformations in term of Probabilistic Information Content (PIC).
The direct extension of this transformation for dealing with qualitative belief
assignments is also presented.
|
0807.3755
|
Approximating Document Frequency with Term Count Values
|
cs.IR cs.DL
|
For bounded datasets such as the TREC Web Track (WT10g) the computation of
term frequency (TF) and inverse document frequency (IDF) is not difficult.
However, when the corpus is the entire web, direct IDF calculation is
impossible and values must instead be estimated. Most available datasets
provide values for term count (TC) meaning the number of times a certain term
occurs in the entire corpus. Intuitively this value is different from document
frequency (DF), the number of documents (e.g., web pages) a certain term occurs
in. We conduct a comparison study between TC and DF values within the Web as
Corpus (WaC). We found a very strong correlation with Spearman's rho >0.8
(p<0.005) which makes us confident in claiming that for such recently created
corpora the TC and DF values can be used interchangeably to compute IDF values.
These results are useful for the generation of accurate lexical signatures
based on the TF-IDF scheme.
|
0807.3795
|
Relational Lattice Axioms
|
cs.DB
|
Relational lattice is a formal mathematical model for Relational algebra. It
reduces the set of six classic relational algebra operators to two: natural
join and inner union. We continue to investigate Relational lattice properties
with emphasis onto axiomatic definition. New results include additional axioms,
equational definition for set difference (more generally anti-join), and case
study demonstrating application of the relational lattice theory for query
transformations.
|
0807.3803
|
Quantum Convolutional Coding with Shared Entanglement: General Structure
|
quant-ph cs.IT math.IT
|
We present a general theory of entanglement-assisted quantum convolutional
coding. The codes have a convolutional or memory structure, they assume that
the sender and receiver share noiseless entanglement prior to quantum
communication, and they are not restricted to possess the
Calderbank-Shor-Steane structure as in previous work. We provide two
significant advances for quantum convolutional coding theory. We first show how
to "expand" a given set of quantum convolutional generators. This expansion
step acts as a preprocessor for a polynomial symplectic Gram-Schmidt
orthogonalization procedure that simplifies the commutation relations of the
expanded generators to be the same as those of entangled Bell states (ebits)
and ancilla qubits. The above two steps produce a set of generators with
equivalent error-correcting properties to those of the original generators. We
then demonstrate how to perform online encoding and decoding for a stream of
information qubits, halves of ebits, and ancilla qubits. The upshot of our
theory is that the quantum code designer can engineer quantum convolutional
codes with desirable error-correcting properties without having to worry about
the commutation relations of these generators.
|
0807.3806
|
On the Rate of Channel Polarization
|
cs.IT math.IT
|
It is shown that for any binary-input discrete memoryless channel $W$ with
symmetric capacity $I(W)$ and any rate $R <I(W)$, the probability of block
decoding error for polar coding under successive cancellation decoding
satisfies $P_e \le 2^{-N^\beta}$ for any $\beta<\frac12$ when the block-length
$N$ is large enough.
|
0807.3845
|
Formal semantics of language and the Richard-Berry paradox
|
cs.CL cs.CC cs.LO
|
The classical logical antinomy known as Richard-Berry paradox is combined
with plausible assumptions about the size i.e. the descriptional complexity of
Turing machines formalizing certain sentences, to show that formalization of
language leads to contradiction.
|
0807.3908
|
A Distributed Process Infrastructure for a Distributed Data Structure
|
cs.AI cs.DL
|
The Resource Description Framework (RDF) is continuing to grow outside the
bounds of its initial function as a metadata framework and into the domain of
general-purpose data modeling. This expansion has been facilitated by the
continued increase in the capacity and speed of RDF database repositories known
as triple-stores. High-end RDF triple-stores can hold and process on the order
of 10 billion triples. In an effort to provide a seamless integration of the
data contained in RDF repositories, the Linked Data community is providing
specifications for linking RDF data sets into a universal distributed graph
that can be traversed by both man and machine. While the seamless integration
of RDF data sets is important, at the scale of the data sets that currently
exist and will ultimately grow to become, the "download and index" philosophy
of the World Wide Web will not so easily map over to the Semantic Web. This
essay discusses the importance of adding a distributed RDF process
infrastructure to the current distributed RDF data structure.
|
0807.3913
|
DMT of weighted Parallel Channels: Application to Broadcast Channel
|
cs.IT math.IT
|
In a broadcast channel with random packet arrival and transmission queues,
the stability of the system is achieved by maximizing a weighted sum rate
capacity with suitable weights that depend on the queue size. The weighted sum
rate capacity using Dirty Paper Coding (DPC) and Zero Forcing (ZF) is
asymptotically equivalent to the weighted sum capacity over parallel
single-channels. In this paper, we study the Diversity Multiplexing Tradeoff
(DMT) of the fading broadcast channel under a fixed weighted sum rate capacity
constraint. The DMT of both identical and different parallel weighted MISO
channels is first derived. Finally, we deduce the DMT of a broadcast channel
using DPC and ZF precoders.
|
0807.3917
|
Channel polarization: A method for constructing capacity-achieving codes
for symmetric binary-input memoryless channels
|
cs.IT math.IT
|
A method is proposed, called channel polarization, to construct code
sequences that achieve the symmetric capacity $I(W)$ of any given binary-input
discrete memoryless channel (B-DMC) $W$. The symmetric capacity is the highest
rate achievable subject to using the input letters of the channel with equal
probability. Channel polarization refers to the fact that it is possible to
synthesize, out of $N$ independent copies of a given B-DMC $W$, a second set of
$N$ binary-input channels $\{W_N^{(i)}:1\le i\le N\}$ such that, as $N$ becomes
large, the fraction of indices $i$ for which $I(W_N^{(i)})$ is near 1
approaches $I(W)$ and the fraction for which $I(W_N^{(i)})$ is near 0
approaches $1-I(W)$. The polarized channels $\{W_N^{(i)}\}$ are
well-conditioned for channel coding: one need only send data at rate 1 through
those with capacity near 1 and at rate 0 through the remaining. Codes
constructed on the basis of this idea are called polar codes. The paper proves
that, given any B-DMC $W$ with $I(W)>0$ and any target rate $R < I(W)$, there
exists a sequence of polar codes $\{{\mathscr C}_n;n\ge 1\}$ such that
${\mathscr C}_n$ has block-length $N=2^n$, rate $\ge R$, and probability of
block error under successive cancellation decoding bounded as $P_{e}(N,R) \le
\bigoh(N^{-\frac14})$ independently of the code rate. This performance is
achievable by encoders and decoders with complexity $O(N\log N)$ for each.
|
0807.3991
|
Codes Associated with Special Linear Groups and Power Moments of
Multi-dimensional Kloosterman Sums
|
math.NT cs.IT math.IT
|
In this paper, we construct the binary linear codes $C(SL(n,q))$ associated
with finite special linear groups $SL(n,q)$, with both \emph{n,q} powers of
two. Then, via Pless power moment identity and utilizing our previous result on
the explicit expression of the Gauss sum for $SL(n,q)$, we obtain a recursive
formula for the power moments of multi-dimensional Kloosterman sums in terms of
the frequencies of weights in $C(SL(n,q))$. In particular, when $n=2$, this
gives a recursive formula for the power moments of Kloosterman sums. We
illustrate our results with some examples.
|
0807.4009
|
Statistical mechanics of lossy compression for non-monotonic multilayer
perceptrons
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.IT
|
A lossy data compression scheme for uniformly biased Boolean messages is
investigated via statistical mechanics techniques. We utilize tree-like
committee machine (committee tree) and tree-like parity machine (parity tree)
whose transfer functions are non-monotonic. The scheme performance at the
infinite code length limit is analyzed using the replica method. Both committee
and parity treelike networks are shown to saturate the Shannon bound. The AT
stability of the Replica Symmetric solution is analyzed, and the tuning of the
non-monotonic transfer function is also discussed.
|
0807.4074
|
Low-delay, Low-PAPR, High-rate Non-square Complex Orthogonal Designs
|
cs.IT math.IT
|
The maximal rate for non-square Complex Orthogonal Designs (CODs) with $n$
transmit antennas is ${1/2}+\frac{1}{n}$ if $n$ is even and
${1/2}+\frac{1}{n+1}$ if $n$ is odd, which are close to 1/2 for large values of
$n.$ A class of maximal rate non-square CODs have been constructed by Liang
(IEEE Trans. Inform. Theory, 2003) and Lu et. al. (IEEE Trans. Inform. Theory,
2005) have shown that the decoding delay of the codes given by Liang, can be
reduced by 50% when number of transmit antennas is a multiple of 4. Adams et.
al. (IEEE Trans. Inform. Theory, 2007) have shown that the designs of Liang are
of minimal-delay for $n$ equal to 1 and 3 modulo 4 and that of Lu et.al. are of
minimal delay when $n$ is a multiple of $4.$ However, these minimal delays are
large compared to the delays of the rate 1/2 non-square CODs constructed by
Tarokh et al (IEEE Trans. Inform. Theory, 1999) from rate-1 real orthogonal
designs (RODs). In this paper, we construct a class of rate-1/2 non-square CODs
for any $n$ with the decoding delay equal to 50% of that of the delay of the
rate-1/2 codes given by Tarokh et al. This is achieved by giving first a
general construction of rate-1 square Real Orthogonal Designs (RODs) which
includes as special cases the well known constructions of Adams, Lax and
Phillips and Geramita and Pullman, and then making use of it to obtain the
desired rate-1/2 non-square COD. For the case of 9 transmit antennas, our
rate-1/2 COD is shown to be of minimal-delay. The proposed construction results
in designs with zero entries which may have high Peak-to-Average Power Ratio
(PAPR) and it is shown that by appropriate postmultiplication, a design with no
zero entries can be obtained with no change in the code parameters.
|
0807.4128
|
Square Complex Orthogonal Designs with Low PAPR and Signaling Complexity
|
cs.IT math.IT
|
Space-Time Block Codes from square complex orthogonal designs (SCOD) have
been extensively studied and most of the existing SCODs contain large number of
zero. The zeros in the designs result in high peak-to-average power ratio
(PAPR) and also impose a severe constraint on hardware implementation of the
code when turning off some of the transmitting antennas whenever a zero is
transmitted. Recently, rate 1/2 SCODs with no zero entry have been reported for
8 transmit antennas. In this paper, SCODs with no zero entry for $2^a$ transmit
antennas whenever $a+1$ is a power of 2, are constructed which includes the 8
transmit antennas case as a special case. More generally, for arbitrary values
of $a$, explicit construction of $2^a\times 2^a$ rate $\frac{a+1}{2^a}$ SCODs
with the ratio of number of zero entries to the total number of entries equal
to $1-\frac{a+1}{2^a}2^{\lfloor log_2(\frac{2^a}{a+1}) \rfloor}$ is reported,
whereas for standard known constructions, the ratio is $1-\frac{a+1}{2^a}$. The
codes presented do not result in increased signaling complexity. Simulation
results show that the codes constructed in this paper outperform the codes
using the standard construction under peak power constraint while performing
the same under average power constraint.
|
0807.4198
|
Positive factor networks: A graphical framework for modeling
non-negative sequential data
|
cs.LG
|
We present a novel graphical framework for modeling non-negative sequential
data with hierarchical structure. Our model corresponds to a network of coupled
non-negative matrix factorization (NMF) modules, which we refer to as a
positive factor network (PFN). The data model is linear, subject to
non-negativity constraints, so that observation data consisting of an additive
combination of individually representable observations is also representable by
the network. This is a desirable property for modeling problems in
computational auditory scene analysis, since distinct sound sources in the
environment are often well-modeled as combining additively in the corresponding
magnitude spectrogram. We propose inference and learning algorithms that
leverage existing NMF algorithms and that are straightforward to implement. We
present a target tracking example and provide results for synthetic observation
data which serve to illustrate the interesting properties of PFNs and motivate
their potential usefulness in applications such as music transcription, source
separation, and speech recognition. We show how a target process characterized
by a hierarchical state transition model can be represented as a PFN. Our
results illustrate that a PFN which is defined in terms of a single target
observation can then be used to effectively track the states of multiple
simultaneous targets. Our results show that the quality of the inferred target
states degrades gradually as the observation noise is increased. We also
present results for an example in which meaningful hierarchical features are
extracted from a spectrogram. Such a hierarchical representation could be
useful for music transcription and source separation applications. We also
propose a network for language modeling.
|
0807.4247
|
Z2Z4-linear codes: rank and kernel
|
cs.IT cs.DM math.IT
|
A code C is Z2Z4-additive if the set of coordinates can be partitioned into
two subsets X and Y such that the punctured code of C by deleting the
coordinates outside X (respectively, Y) is a binary linear code (respectively,
a quaternary linear code). In this paper, the rank and dimension of the kernel
for Z2Z4-linear codes, which are the corresponding binary codes of
Z2Z4-additive codes, are studied. The possible values of these two parameters
for Z2Z4-linear codes, giving lower and upper bounds, are established. For each
possible rank r between these bounds, the construction of a Z2Z4-linear code
with rank r is given. Equivalently, for each possible dimension of the kernel
k, the construction of a Z2Z4-linear code with dimension of the kernel k is
given. Finally, the bounds on the rank, once the kernel dimension is fixed, are
established and the construction of a Z2Z4-additive code for each possible pair
(r,k) is given.
|
0807.4322
|
Carnot in the Information Age: Discrete Symmetric Channels
|
cond-mat.stat-mech cs.IT math.IT
|
Modeling communication channels as thermal systems results in Hamiltonians
which are an explicit function of the temperature. The first two authors have
recently generalized the second thermodynamic law to encompass systems with
temperature-dependent energy levels, $dQ=TdS+<d\mathcal{E}/dT>dT$, where
{$<\cdot>$} denotes averaging over the Boltzmann distribution, recomputing the
mutual information and other main properties of the popular Gaussian channel.
Here the mutual information for the binary symmetric channel as well as for the
discrete symmetric channel consisting of 4 input/output (I/O) symbols is
explicitly calculated using the generalized second law of thermodynamics. For
equiprobable I/O the mutual information of the examined channels has a very
simple form, -$\gamma U(\gamma)|_0^\beta$, where $U$ denotes the internal
energy of the channel. We prove that this simple form of the mutual information
governs the class of discrete memoryless symmetric communication channels with
equiprobable I/O symbols.
|
0807.4325
|
Schroedinger-like PageRank equation and localization in the WWW
|
physics.soc-ph cond-mat.stat-mech cs.IR physics.data-an
|
The WorldWide Web is one of the most important communication systems we use
in our everyday life. Despite its central role, the growth and the development
of the WWW is not controlled by any central authority. This situation has
created a huge ensemble of connections whose complexity can be fruitfully
described and quantified by network theory. One important application that
allows to sort out the information present in these connections is given by the
PageRank alghorithm. Computation of this quantity is usually made iteratively
with a large use of computational time. In this paper we show that the PageRank
can be expressed in terms of a wave function obeying a Schroedinger-like
equation. In particular the topological disorder given by the unbalance of
outgoing and ingoing links between pages, induces wave function and potential
structuring. This allows to directly localize the pages with the largest score.
Through this new representation we can now compute the PageRank without
iterative techniques. For most of the cases of interest our method is faster
than the original one. Our results also clarify the role of topology in the
diffusion of information within complex networks. The whole approach opens the
possibility to novel techniques inspired by quantum physics for the analysis of
the WWW properties.
|
0807.4345
|
Avoider robot design to dim the fire with dt basic mini system
|
cs.RO
|
Avoider robot is mean robot who is designed to avoid the block in around.
Except that, this robot is also added by an addition application to dim the
fire. This robot is made with ultrasonic sensor PING. This sensor is set on the
front, right and left from robot. This sensor is used robot to look for the
right street, so that robot can walk on. After the robot can look for the right
street, next accomplished the robot is looking for the fire in around. And the
next, dim the fire with fan. This robot is made with basic stamp 2
micro-controller. And that micro-controller can be found in dt-basic mini
system module. This robot is made with servo motor on the right and left side,
which is used to movement.
|
0807.4417
|
On Introspection, Metacognitive Control and Augmented Data Mining Live
Cycles
|
cs.AI
|
We discuss metacognitive modelling as an enhancement to cognitive modelling
and computing. Metacognitive control mechanisms should enable AI systems to
self-reflect, reason about their actions, and to adapt to new situations. In
this respect, we propose implementation details of a knowledge taxonomy and an
augmented data mining life cycle which supports a live integration of obtained
models.
|
0807.4478
|
An Image-Based Sensor System for Autonomous Rendez-Vous with
Uncooperative Satellites
|
cs.CV cs.AI
|
In this paper are described the image processing algorithms developed by
SENER, Ingenieria y Sistemas to cope with the problem of image-based,
autonomous rendez-vous (RV) with an orbiting satellite. The methods developed
have a direct application in the OLEV (Orbital Life Extension Extension
Vehicle) mission. OLEV is a commercial mission under development by a
consortium formed by Swedish Space Corporation, Kayser-Threde and SENER, aimed
to extend the operational life of geostationary telecommunication satellites by
supplying them control, navigation and guidance services. OLEV is planned to
use a set of cameras to determine the angular position and distance to the
client satellite during the complete phases of rendez-vous and docking, thus
enabling the operation with satellites not equipped with any specific
navigational aid to provide support during the approach. The ability to operate
with un-equipped client satellites significantly expands the range of
applicability of the system under development, compared to other competing
video technologies already tested in previous spatial missions, such as the
ones described here below.
|
0807.4494
|
Fast, exact (but unstable) spin spherical harmonic transforms
|
astro-ph cs.IT math.IT
|
In many applications data are measured or defined on a spherical manifold;
spherical harmonic transforms are then required to access the frequency content
of the data. We derive algorithms to perform forward and inverse spin spherical
harmonic transforms for functions of arbitrary spin number. These algorithms
involve recasting the spin transform on the two-sphere S^2 as a Fourier
transform on the two-torus T^2. Fast Fourier transforms are then used to
compute Fourier coefficients, which are related to spherical harmonic
coefficients through a linear transform. By recasting the problem as a Fourier
transform on the torus we appeal to the usual Shannon sampling theorem to
develop spherical harmonic transforms that are theoretically exact for
band-limited functions, thereby providing an alternative sampling theorem on
the sphere. The computational complexity of our forward and inverse spin
spherical harmonic transforms scale as O(L^3) for any arbitrary spin number,
where L is the harmonic band-limit of the spin function on the sphere.
Numerical experiments are performed and unfortunately the forward transform is
found to be unstable for band-limits above L~32. The instability is due to the
poorly conditioned linear system relating Fourier and spherical harmonic
coefficients. The inverse transform is expected to be stable, although it is
not possible to verify this hypothesis.
|
0807.4548
|
Compound Multiple Access Channels with Partial Cooperation
|
cs.IT math.IT
|
A two-user discrete memoryless compound multiple access channel with a common
message and conferencing decoders is considered. The capacity region is
characterized in the special cases of physically degraded channels and
unidirectional cooperation, and achievable rate regions are provided for the
general case. The results are then extended to the corresponding Gaussian
model. In the Gaussian setup, the provided achievable rates are shown to lie
within some constant number of bits from the boundary of the capacity region in
several special cases. An alternative model, in which the encoders are
connected by conferencing links rather than having a common message, is studied
as well, and the capacity region for this model is also determined for the
cases of physically degraded channels and unidirectional cooperation. Numerical
results are also provided to obtain insights about the potential gains of
conferencing at the decoders and encoders.
|
0807.4580
|
A Logical Model and Data Placement Strategies for MEMS Storage Devices
|
cs.DB
|
MEMS storage devices are new non-volatile secondary storages that have
outstanding advantages over magnetic disks. MEMS storage devices, however, are
much different from magnetic disks in the structure and access characteristics.
They have thousands of heads called probe tips and provide the following two
major access facilities: (1) flexibility: freely selecting a set of probe tips
for accessing data, (2) parallelism: simultaneously reading and writing data
with the set of probe tips selected. Due to these characteristics, it is
nontrivial to find data placements that fully utilize the capability of MEMS
storage devices. In this paper, we propose a simple logical model called the
Region-Sector (RS) model that abstracts major characteristics affecting data
retrieval performance, such as flexibility and parallelism, from the physical
MEMS storage model. We also suggest heuristic data placement strategies based
on the RS model and derive new data placements for relational data and
two-dimensional spatial data by using those strategies. Experimental results
show that the proposed data placements improve the data retrieval performance
by up to 4.0 times for relational data and by up to 4.8 times for
two-dimensional spatial data of approximately 320 Mbytes compared with those of
existing data placements. Further, these improvements are expected to be more
marked as the database size grows.
|
0807.4581
|
Robust Recovery of Signals From a Structured Union of Subspaces
|
nlin.CG cs.IT math.IT nlin.SI
|
Traditional sampling theories consider the problem of reconstructing an
unknown signal $x$ from a series of samples. A prevalent assumption which often
guarantees recovery from the given measurements is that $x$ lies in a known
subspace. Recently, there has been growing interest in nonlinear but structured
signal models, in which $x$ lies in a union of subspaces. In this paper we
develop a general framework for robust and efficient recovery of such signals
from a given set of samples. More specifically, we treat the case in which $x$
lies in a sum of $k$ subspaces, chosen from a larger set of $m$ possibilities.
The samples are modelled as inner products with an arbitrary set of sampling
functions. To derive an efficient and robust recovery algorithm, we show that
our problem can be formulated as that of recovering a block-sparse vector whose
non-zero elements appear in fixed blocks. We then propose a mixed
$\ell_2/\ell_1$ program for block sparse recovery. Our main result is an
equivalence condition under which the proposed convex algorithm is guaranteed
to recover the original signal. This result relies on the notion of block
restricted isometry property (RIP), which is a generalization of the standard
RIP used extensively in the context of compressed sensing. Based on RIP we also
prove stability of our approach in the presence of noise and modelling errors.
A special case of our framework is that of recovering multiple measurement
vectors (MMV) that share a joint sparsity pattern. Adapting our results to this
context leads to new MMV recovery methods as well as equivalence conditions
under which the entire set can be determined efficiently.
|
0807.4618
|
AceWiki: A Natural and Expressive Semantic Wiki
|
cs.HC cs.AI
|
We present AceWiki, a prototype of a new kind of semantic wiki using the
controlled natural language Attempto Controlled English (ACE) for representing
its content. ACE is a subset of English with a restricted grammar and a formal
semantics. The use of ACE has two important advantages over existing semantic
wikis. First, we can improve the usability and achieve a shallow learning
curve. Second, ACE is more expressive than the formal languages of existing
semantic wikis. Our evaluation shows that people who are not familiar with the
formal foundations of the Semantic Web are able to deal with AceWiki after a
very short learning phase and without the help of an expert.
|
0807.4619
|
Guaranteed Cost LQG Control of Uncertain Linear Quantum Stochastic
Systems
|
quant-ph cs.SY math.OC
|
In this paper, we formulate and solve a guaranteed cost control problem for a
class of uncertain linear stochastic quantum systems. For these quantum
systems, a connection with an associated classical (non-quantum) system is
first established. Using this connection, the desired guaranteed cost results
are established. The theory presented is illustrated using an example from
quantum optics.
|
0807.4620
|
A Compositional Query Algebra for Second-Order Logic and Uncertain
Databases
|
cs.DB cs.LO
|
World-set algebra is a variable-free query language for uncertain databases.
It constitutes the core of the query language implemented in MayBMS, an
uncertain database system. This paper shows that world-set algebra captures
exactly second-order logic over finite structures, or equivalently, the
polynomial hierarchy. The proofs also imply that world-set algebra is closed
under composition, a previously open problem.
|
0807.4623
|
AceWiki: Collaborative Ontology Management in Controlled Natural
Language
|
cs.HC cs.AI
|
AceWiki is a prototype that shows how a semantic wiki using controlled
natural language - Attempto Controlled English (ACE) in our case - can make
ontology management easy for everybody. Sentences in ACE can automatically be
translated into first-order logic, OWL, or SWRL. AceWiki integrates the OWL
reasoner Pellet and ensures that the ontology is always consistent. Previous
results have shown that people with no background in logic are able to add
formal knowledge to AceWiki without being instructed or trained in advance.
|
0807.4671
|
Codes Associated with $O^+(2n,2^r)$ and Power Moments of Kloosterman
Sums
|
math.NT cs.IT math.IT
|
In this paper, we construct three binary linear codes $C(SO^+(2,q))$,
$C(O^+(2,q))$, $C(SO^+(4,q))$, respectively associated with the orthogonal
groups $SO^+(2,q)$, $O^+(2,q)$, $SO^+(4,q)$, with $q$ powers of two. Then we
obtain recursive formulas for the power moments of Kloosterman and
2-dimensional Kloosterman sums in terms of the frequencies of weights in the
codes. This is done via Pless power moment identity and by utilizing the
explicit expressions of Gauss sums for the orthogonal groups. We emphasize
that, when the recursive formulas for the power moments of Kloosterman sums are
compared, the present one is computationally more effective than the previous
one constructed from the special linear group $SL(2,q)$. We illustrate our
results with some examples.
|
0807.4680
|
Hacia una teoria de unificacion para los comportamientos cognitivos
|
cs.AI
|
Each cognitive science tries to understand a set of cognitive behaviors. The
structuring of knowledge of this nature's aspect is far from what it can be
expected about a science. Until now universal standard consistently describing
the set of cognitive behaviors has not been found, and there are many questions
about the cognitive behaviors for which only there are opinions of members of
the scientific community. This article has three proposals. The first proposal
is to raise to the scientific community the necessity of unified the cognitive
behaviors. The second proposal is claim the application of the Newton's
reasoning rules about nature of his book, Philosophiae Naturalis Principia
Mathematica, to the cognitive behaviors. The third is to propose a scientific
theory, currently developing, that follows the rules established by Newton to
make sense of nature, and could be the theory to explain all the cognitive
behaviors.
|
0807.4701
|
An image processing analysis of skin textures
|
cs.CV
|
Colour and coarseness of skin are visually different. When image processing
is involved in the skin analysis, it is important to quantitatively evaluate
such differences using texture features. In this paper, we discuss a texture
analysis and measurements based on a statistical approach to the pattern
recognition. Grain size and anisotropy are evaluated with proper diagrams. The
possibility to determine the presence of pattern defects is also discussed.
|
0807.4753
|
Counterexamples to the maximal p-norm multiplicativity conjecture for
all p > 1
|
quant-ph cs.IT math-ph math.IT math.MP
|
For all p > 1, we demonstrate the existence of quantum channels with
non-multiplicative maximal output p-norms. Equivalently, for all p >1, the
minimum output Renyi entropy of order p of a quantum channel is not additive.
The violations found are large; in all cases, the minimum output Renyi entropy
of order p for a product channel need not be significantly greater than the
minimum output entropy of its individual factors. Since p=1 corresponds to the
von Neumann entropy, these counterexamples demonstrate that if the additivity
conjecture of quantum information theory is true, it cannot be proved as a
consequence of any channel-independent guarantee of maximal p-norm
multiplicativity. We also show that a class of channels previously studied in
the context of approximate encryption lead to counterexamples for all p > 2.
|
0807.4770
|
Channel Coding and Decoding in a Relay System Operated with Physical
layer Network Coding
|
cs.NI cs.IT math.IT
|
Physical-layer Network Coding (PNC) can significantly improve the throughput
of wireless two way relay channel (TWRC) by allowing the two end nodes to
transmit messages to the relay simultaneously. To achieve reliable
communication, channel coding could be applied on top of PNC. This paper
investigates link-by-link channel-coded PNC, in which a critical process at the
relay is to transform the superimposed channel-coded packets received from the
two end nodes plus noise, Y3=X1+X2+W3, to the network-coded combination of the
source packets, S1 XOR S2 . This is in distinct to the traditional
multiple-access problem, in which the goal is to obtain S1 and S2 separately.
The transformation from Y3 to (S1 XOR S2) is referred to as the
Channel-decoding-Network-Coding process (CNC) in that it involves both channel
decoding and network coding operations. A contribution of this paper is the
insight that in designing CNC, we should first (i) channel-decode Y3 to the
superimposed source symbols S1+S2 before (ii) transforming S1+S2 to the
network-coded packets (S1 XOR S2) . Compared with previously proposed
strategies for CNC, this strategy reduces the channel-coding network-coding
mismatch. It is not obvious, however, that an efficient decoder for step (i)
exists. A second contribution of this paper is to provide an explicit
construction of such a decoder based on the use of the Repeat Accumulate (RA)
code. Specifically, we redesign the belief propagation algorithm of the RA code
for traditional point-to-point channel to suit the need of the PNC
multiple-access channel. Simulation results show that our new scheme
outperforms the previously proposed schemes significantly in terms of BER
without added complexity.
|
0807.4846
|
Error-Correcting Codes in Projective Spaces via Rank-Metric Codes and
Ferrers Diagrams
|
cs.IT math.IT
|
Coding in the projective space has received recently a lot of attention due
to its application in network coding. Reduced row echelon form of the linear
subspaces and Ferrers diagram can play a key role for solving coding problems
in the projective space. In this paper we propose a method to design
error-correcting codes in the projective space. We use a multilevel approach to
design our codes. First, we select a constant weight code. Each codeword
defines a skeleton of a basis for a subspace in reduced row echelon form. This
skeleton contains a Ferrers diagram on which we design a rank-metric code. Each
such rank-metric code is lifted to a constant dimension code. The union of
these codes is our final constant dimension code. In particular the codes
constructed recently by Koetter and Kschischang are a subset of our codes. The
rank-metric codes used for this construction form a new class of rank-metric
codes. We present a decoding algorithm to the constructed codes in the
projective space. The efficiency of the decoding depends on the efficiency of
the decoding for the constant weight codes and the rank-metric codes. Finally,
we use puncturing on our final constant dimension codes to obtain large codes
in the projective space which are not constant dimension.
|
0807.4881
|
Capacity and Performance of Adaptive MIMO System Based on Beam-Nulling
|
cs.IT math.IT
|
In this paper, we propose a scheme called "beam-nulling" for MIMO adaptation.
In the beam-nulling scheme, the eigenvector of the weakest subchannel is fed
back and then signals are sent over a generated subspace orthogonal to the
weakest subchannel. Theoretical analysis and numerical results show that the
capacity of beam-nulling is closed to the optimal water-filling at medium SNR.
Additionally, signal-to-interference-plus-noise ratio (SINR) of MMSE receiver
is derived for beam-nulling. Then the paper presents the associated average
bit-error rate (BER) of beam-nulling numerically which is verified by
simulation. Simulation results are also provided to compare beam-nulling with
beamforming. To improve performance further, beam-nulling is concatenated with
linear dispersion code. Simulation results are also provided to compare the
concatenated beam-nulling scheme with the beamforming scheme at the same data
rate. Additionally, the existing beamforming and new proposed beam-nulling can
be extended if more than one eigenvector is available at the transmitter. The
new extended schemes are called multi-dimensional (MD) beamforming and MD
beam-nulling. Theoretical analysis and numerical results in terms of capacity
are also provided to evaluate the new extended schemes. Simulation results show
that the MD scheme with LDC can outperform the MD scheme with STBC
significantly when the data rate is high.
|
0807.4995
|
Algebraic Soft-Decision Decoding of Hermitian Codes
|
cs.IT math.IT
|
An algebraic soft-decision decoder for Hermitian codes is presented. We apply
Koetter and Vardy's soft-decision decoding framework, now well established for
Reed-Solomon codes, to Hermitian codes. First we provide an algebraic
foundation for soft-decision decoding. Then we present an interpolation
algorithm finding the Q-polynomial that plays a key role in the decoding. With
some simulation results, we compare performances of the algebraic soft-decision
decoders for Hermitian codes and Reed-Solomon codes, favorable to the former.
|
0807.5091
|
Message-passing for Maximum Weight Independent Set
|
cs.AI cs.IT math.IT
|
We investigate the use of message-passing algorithms for the problem of
finding the max-weight independent set (MWIS) in a graph. First, we study the
performance of the classical loopy max-product belief propagation. We show that
each fixed point estimate of max-product can be mapped in a natural way to an
extreme point of the LP polytope associated with the MWIS problem. However,
this extreme point may not be the one that maximizes the value of node weights;
the particular extreme point at final convergence depends on the initialization
of max-product. We then show that if max-product is started from the natural
initialization of uninformative messages, it always solves the correct LP -- if
it converges. This result is obtained via a direct analysis of the iterative
algorithm, and cannot be obtained by looking only at fixed points.
The tightness of the LP relaxation is thus necessary for max-product
optimality, but it is not sufficient. Motivated by this observation, we show
that a simple modification of max-product becomes gradient descent on (a
convexified version of) the dual of the LP, and converges to the dual optimum.
We also develop a message-passing algorithm that recovers the primal MWIS
solution from the output of the descent algorithm. We show that the MWIS
estimate obtained using these two algorithms in conjunction is correct when the
graph is bipartite and the MWIS is unique.
Finally, we show that any problem of MAP estimation for probability
distributions over finite domains can be reduced to an MWIS problem. We believe
this reduction will yield new insights and algorithms for MAP estimation.
|
0807.5120
|
Accelerated Option Pricing in Multiple Scenarios
|
cs.CE
|
This paper covers a massive acceleration of Monte-Carlo based pricing method
for financial products and financial derivatives. The method is applicable in
risk management settings, where a financial product has to be priced under a
number of potential future scenarios. Instead of starting a separate nested
Monte Carlo simulation for each scenario under consideration, the new method
covers the utilization of very few representative nested simulations and
estimating the product prices at each scenario by a smoothing method based on
the state-space. This smoothing technique can be e.g. non-parametric regression
or kernel smoothing.
|
0808.0012
|
Lectures on Probability, Entropy, and Statistical Physics
|
physics.data-an cond-mat.stat-mech cs.IT math.IT math.ST physics.gen-ph stat.TH
|
These lectures deal with the problem of inductive inference, that is, the
problem of reasoning under conditions of incomplete information. Is there a
general method for handling uncertainty? Or, at least, are there rules that
could in principle be followed by an ideally rational mind when discussing
scientific matters? What makes one statement more plausible than another? How
much more plausible? And then, when new information is acquired how do we
change our minds? Or, to put it differently, are there rules for learning? Are
there rules for processing information that are objective and consistent? Are
they unique? And, come to think of it, what, after all, is information? It is
clear that data contains or conveys information, but what does this precisely
mean? Can information be conveyed in other ways? Is information physical? Can
we measure amounts of information? Do we need to? Our goal is to develop the
main tools for inductive inference--probability and entropy--from a thoroughly
Bayesian point of view and to illustrate their use in physics with examples
borrowed from the foundations of classical statistical physics.
|
0808.0036
|
Why Does a Kronecker Model Result in Misleading Capacity Estimates?
|
cs.IT math.IT
|
Many recent works that study the performance of multi-input multi-output
(MIMO) systems in practice assume a Kronecker model where the variances of the
channel entries, upon decomposition on to the transmit and the receive
eigen-bases, admit a separable form. Measurement campaigns, however, show that
the Kronecker model results in poor estimates for capacity. Motivated by these
observations, a channel model that does not impose a separable structure has
been recently proposed and shown to fit the capacity of measured channels
better. In this work, we show that this recently proposed modeling framework
can be viewed as a natural consequence of channel decomposition on to its
canonical coordinates, the transmit and/or the receive eigen-bases. Using tools
from random matrix theory, we then establish the theoretical basis behind the
Kronecker mismatch at the low- and the high-SNR extremes: 1) Sparsity of the
dominant statistical degrees of freedom (DoF) in the true channel at the
low-SNR extreme, and 2) Non-regularity of the sparsity structure (disparities
in the distribution of the DoF across the rows and the columns) at the high-SNR
extreme.
|
0808.0037
|
An Energy-Based Comparison of Long-Hop and Short-Hop Routing in MIMO
Networks
|
cs.IT math.IT
|
This paper considers the problem of selecting either routes that consist of
long hops or routes that consist of short hops in a network of multiple-antenna
nodes, where each transmitting node employs spatial multiplexing. This
distance-dependent route selection problem is approached from the viewpoint of
energy efficiency, where a route is selected with the objective of minimizing
the transmission energy consumed while satisfying a target outage criterion at
the final destination. Deterministic line networks and two-dimensional random
networks are considered. It is shown that when 1) the number of hops traversed
between the source and destination grows large or 2) when the target success
probability approaches one or 3) when the number of transmit and/or receive
antennas grows large, short-hop routing requires less energy than long-hop
routing. It is also shown that if both routing strategies are subject to the
same delay constraint, long-hop routing requires less energy than short-hop
routing as the target success probability approaches one. In addition,
numerical analysis indicates that given loose outage constraints, only a small
number of transmit antennas are needed for short-hop routing to have its
maximum advantage over long-hop routing, while given stringent outage
constraints, the advantage of short-hop over long-hop routing always increases
with additional transmit antennas.
|
0808.0056
|
I'm sorry to say, but your understanding of image processing
fundamentals is absolutely wrong
|
cs.AI cs.CV cs.IR cs.RO q-bio.NC
|
The ongoing discussion whether modern vision systems have to be viewed as
visually-enabled cognitive systems or cognitively-enabled vision systems is
groundless, because perceptual and cognitive faculties of vision are separate
components of human (and consequently, artificial) information processing
system modeling.
|
0808.0075
|
Optimal Beamforming for Two-Way Multi-Antenna Relay Channel with
Analogue Network Coding
|
cs.IT math.IT
|
This paper studies the wireless two-way relay channel (TWRC), where two
source nodes, S1 and S2, exchange information through an assisting relay node,
R. It is assumed that R receives the sum signal from S1 and S2 in one
time-slot, and then amplifies and forwards the received signal to both S1 and
S2 in the next time-slot. By applying the principle of analogue network (ANC),
each of S1 and S2 cancels the so-called "self-interference" in the received
signal from R and then decodes the desired message. Assuming that S1 and S2 are
each equipped with a single antenna and R with multi-antennas, this paper
analyzes the capacity region of an ANC-based TWRC with linear processing
(beamforming) at R. The capacity region contains all the achievable
bidirectional rate-pairs of S1 and S2 under the given transmit power
constraints at S1, S2, and R. We present the optimal relay beamforming
structure as well as an efficient algorithm to compute the optimal beamforming
matrix based on convex optimization techniques. Low-complexity suboptimal relay
beamforming schemes are also presented, and their achievable rates are compared
against the capacity with the optimal scheme.
|
0808.0112
|
Mathematical Structure of Quantum Decision Theory
|
cs.AI math-ph math.MP quant-ph
|
One of the most complex systems is the human brain whose formalized
functioning is characterized by decision theory. We present a "Quantum Decision
Theory" of decision making, based on the mathematical theory of separable
Hilbert spaces. This mathematical structure captures the effect of
superposition of composite prospects, including many incorporated intentions,
which allows us to explain a variety of interesting fallacies and anomalies
that have been reported to particularize the decision making of real human
beings. The theory describes entangled decision making, non-commutativity of
subsequent decisions, and intention interference of composite prospects. We
demonstrate how the violation of the Savage's sure-thing principle (disjunction
effect) can be explained as a result of the interference of intentions, when
making decisions under uncertainty. The conjunction fallacy is also explained
by the presence of the interference terms. We demonstrate that all known
anomalies and paradoxes, documented in the context of classical decision
theory, are reducible to just a few mathematical archetypes, all of which
finding straightforward explanations in the frame of the developed quantum
approach.
|
0808.0234
|
DMT of Multi-hop Cooperative Networks - Part I: Basic Results
|
cs.IT math.IT
|
In this two-part paper, the DMT of cooperative multi-hop networks is
examined. The focus is on single-source single-sink (ss-ss) multi-hop relay
networks having slow-fading links and relays that potentially possess multiple
antennas. The present paper examines the two end-points of the DMT of
full-duplex networks. In particular, the maximum achievable diversity of
arbitrary multi-terminal wireless networks is shown to be equal to the min-cut.
The maximum multiplexing gain of arbitrary full-duplex ss-ss networks is shown
to be equal to the min-cut rank, using a new connection to a deterministic
network. We also prove some basic results including a proof that the colored
noise encountered in AF protocols for cooperative networks can be treated as
white noise for DMT computations. The DMT of a parallel channel with
independent MIMO links is also computed here. As an application of these basic
results, we prove that a linear tradeoff between maximum diversity and maximum
multiplexing gain is achievable for full-duplex networks with single antenna
nodes. All protocols in this paper are explicit and rely only upon
amplify-and-forward (AF) relaying. Half duplex networks are studied, and
explicit codes for all protocols proposed in both parts, are provided in the
companion paper.
|
0808.0235
|
DMT of Multi-hop Cooperative Networks - Part II: Half-Duplex Networks
with Full-Duplex Performance
|
cs.IT math.IT
|
We consider single-source single-sink (ss-ss) multi-hop relay networks, with
slow-fading links and single-antenna half-duplex relay nodes. In a companion
paper, we established some basic results which laid the foundation for the
results presented here. In the present paper, we consider two families of
networks of half-duplex networks. KPP networks may be viewed as the union of K
node-disjoint parallel relaying paths. Generalizations of these networks
include KPP(I) networks, which permit interference between paths and KPP(D)
networks, which possess a direct link between source and sink. We characterize
the DMT of these families of networks completely and show that they can achieve
the cut-set bound, thus proving that full-duplex performance can be obtained
even in the presence of the half-duplex constraint. We then consider layered
networks, and prove that a linear DMT between maximum diversity and maximum
multiplexing gain is achievable. All protocols in this paper are explicit and
use only amplify-and-forward relaying. We also construct codes that achieve the
optimal DMT for all the proposed schemes. Two key implications of the results
in the paper are that the half-duplex constraint does not entail any rate loss
for a large class of cooperative networks and that AF protocols are often
optimal.
|
0808.0272
|
Kovalenko's Full-Rank Limit and Overhead as Lower Bounds for
Error-Performances of LDPC and LT Codes over Binary Erasure Channels
|
cs.IT cs.DM math.CO math.IT
|
We present Kovalenko's full-rank limit as a tight lower bound for decoding
error probability of LDPC codes and LT codes over BEC. From the limit, we
derive a full-rank overhead as a lower bound for stable overheads for
successful maximum-likelihood decoding of the codes.
|
0808.0291
|
One shot schemes for decentralized quickest change detection
|
cs.IT math.IT
|
This work considers the problem of quickest detection with N distributed
sensors that receive continuous sequential observations from the environment.
These sensors employ cumulative sum (CUSUM) strategies and communicate to a
central fusion center by one shot schemes. One shot schemes are schemes in
which the sensors communicate with the fusion center only once, after which
they must signal a detection. The communication is clearly asynchronous and the
case is considered in which the fusion center employs a minimal strategy, which
means that it declares an alarm when the first communication takes place. It is
assumed that the observations received at the sensors are independent and that
the time points at which the appearance of a signal can take place are
different. It is shown that there is no loss of performance of one shot schemes
as compared to the centralized case in an extended Lorden min-max sense, since
the minimum of N CUSUMs is asymptotically optimal as the mean time between
false alarms increases without bound.
|
0808.0374
|
A 8 bits Pipeline Analog to Digital Converter Design for High Speed
Camera Application
|
cs.RO cs.CV
|
- This paper describes a pipeline analog-to-digital converter is implemented
for high speed camera. In the pipeline ADC design, prime factor is designing
operational amplifier with high gain so ADC have been high speed. The other
advantage of pipeline is simple on concept, easy to implement in layout and
have flexibility to increase speed. We made design and simulation using Mentor
Graphics Software with 0.6 \mu m CMOS technology with a total power dissipation
of 75.47 mW. Circuit techniques used include a precise comparator, operational
amplifier and clock management. A switched capacitor is used to sample and
multiplying at each stage. Simulation a worst case DNL and INL of 0.75 LSB. The
design operates at 5 V dc. The ADC achieves a SNDR of 44.86 dB. keywords:
pipeline, switched capacitor, clock management
|
0808.0387
|
Design and Implementation a 8 bits Pipeline Analog to Digital Converter
in the Technology 0.6 \mu m CMOS Process
|
cs.RO cs.CV
|
This paper describes a 8 bits, 20 Msamples/s pipeline analog-to-digital
converter implemented in 0.6 \mu m CMOS technology with a total power
dissipation of 75.47 mW. Circuit techniques used include a precise comparator,
operational amplifier and clock management. A switched capacitor is used to
sample and multiplying at each stage. Simulation a worst case DNL and INL of
0.75 LSB. The design operate at 5 V dc. The ADC achieves a SNDR of 44.86 dB.
keywords : pipeline, switched capacitor, clock management
|
0808.0518
|
Building a terminology network for search: the KoMoHe project
|
cs.DL cs.DB
|
The paper reports about results on the GESIS-IZ project "Competence Center
Modeling and Treatment of Semantic Heterogeneity" (KoMoHe). KoMoHe supervised a
terminology mapping effort, in which 'cross-concordances' between major
controlled vocabularies were organized, created and managed. In this paper we
describe the establishment and implementation of cross-concordances for search
in a digital library (DL).
|
0808.0521
|
Logics for the Relational Syllogistic
|
cs.LO cs.CC cs.CL
|
The Aristotelian syllogistic cannot account for the validity of many
inferences involving relational facts. In this paper, we investigate the
prospects for providing a relational syllogistic. We identify several fragments
based on (a) whether negation is permitted on all nouns, including those in the
subject of a sentence; and (b) whether the subject noun phrase may contain a
relative clause. The logics we present are extensions of the classical
syllogistic, and we pay special attention to the question of whether reductio
ad absurdum is needed. Thus our main goal is to derive results on the existence
(or non-existence) of syllogistic proof systems for relational fragments. We
also determine the computational complexity of all our fragments.
|
0808.0544
|
Generalized Cross-correlation Properties of Chu Sequences
|
cs.IT math.IT
|
In this paper, we analyze the cross-correlation properties for Chu sequences,
which provide information on the distribution of the maximum magnitudes of the
cross-correlation function. Furthermore, we can obtain the number of available
sequences for a given maximum magnitude of the cross-correlation function and
the sequence length.
|
0808.0548
|
How could the replica method improve accuracy of performance assessment
of channel coding?
|
cs.IT math.IT
|
We explore the relation between the techniques of statistical mechanics and
information theory for assessing the performance of channel coding. We base our
study on a framework developed by Gallager in {\em IEEE Trans. Inform. Theory}
{\bf 11}, 3 (1965), where the minimum decoding error probability is
upper-bounded by an average of a generalized Chernoff's bound over a code
ensemble. We show that the resulting bound in the framework can be directly
assessed by the replica method, which has been developed in statistical
mechanics of disordered systems, whereas in Gallager's original methodology
further replacement by another bound utilizing Jensen's inequality is
necessary. Our approach associates a seemingly {\em ad hoc} restriction with
respect to an adjustable parameter for optimizing the bound with a phase
transition between two replica symmetric solutions, and can improve the
accuracy of performance assessments of general code ensembles including low
density parity check codes, although its mathematical justification is still
open.
|
0808.0549
|
Resource Allocation of MU-OFDM Based Cognitive Radio Systems Under
Partial Channel State Information
|
cs.IT cs.NE math.CO math.IT
|
This paper has been withdrawn by the author due to some errors.
|
0808.0556
|
Logic Engines as Interactors
|
cs.PL cs.MA
|
We introduce a new programming language construct, Interactors, supporting
the agent-oriented view that programming is a dialog between simple,
self-contained, autonomous building blocks.
We define Interactors as an abstraction of answer generation and refinement
in Logic Engines resulting in expressive language extension and metaprogramming
patterns, including emulation of Prolog's dynamic database.
A mapping between backtracking based answer generation in the callee and
"forward" recursion in the caller enables interaction between different
branches of the callee's search process and provides simplified design patterns
for algorithms involving combinatorial generation and infinite answer streams.
Interactors extend language constructs like Ruby, Python and C#'s multiple
coroutining block returns through yield statements and they can emulate the
action of monadic constructs and catamorphisms in functional languages.
Keywords: generalized iterators, logic engines, agent oriented programming
language constructs, interoperation with stateful objects, metaprogramming
|
0808.0558
|
Communication Through Jamming over a Slotted ALOHA Channel
|
cs.IT math.IT
|
This work derives bounds on the jamming capacity of a slotted ALOHA system. A
system with n legitimate users, each with a Bernoulli arrival process is
considered. Packets are temporarily stored at the corresponding user queues,
and a slotted ALOHA strategy is used for packet transmissions over the shared
channel. The scenario considered is that of a pair of illegitimate users that
jam legitimate transmissions in order to communicate over the slotted ALOHA
channel. Jamming leads to binary signaling between the illegitimate users, with
packet collisions due to legitimate users treated as (multiplicative) noise in
this channel. Further, the queueing dynamics at the legitimate users
stochastically couples the jamming strategy used by the illegitimate users and
the channel evolution.
By considering various i.i.d. jamming strategies, achievable jamming rates
over the slotted ALOHA channel are derived. Further, an upper bound on the
jamming capacity over the class of all ergodic jamming policies is derived.
These bounds are shown to be tight in the limit where the offered system load
approaches unity.
|
0808.0596
|
On row-by-row coding for 2-D constraints
|
cs.IT math.IT
|
A constant-rate encoder--decoder pair is presented for a fairly large family
of two-dimensional (2-D) constraints. Encoding and decoding is done in a
row-by-row manner, and is sliding-block decodable.
Essentially, the 2-D constraint is turned into a set of independent and
relatively simple one-dimensional (1-D) constraints; this is done by dividing
the array into fixed-width vertical strips. Each row in the strip is seen as a
symbol, and a graph presentation of the respective 1-D constraint is
constructed. The maxentropic stationary Markov chain on this graph is next
considered: a perturbed version of the corresponding probability distribution
on the edges of the graph is used in order to build an encoder which operates
in parallel on the strips. This perturbation is found by means of a network
flow, with upper and lower bounds on the flow through the edges.
A key part of the encoder is an enumerative coder for constant-weight binary
words. A fast realization of this coder is shown, using floating-point
arithmetic.
|
0808.0684
|
9-variable Boolean Functions with Nonlinearity 242 in the Generalized
Rotation Class
|
cs.CR cs.IT math.IT
|
In 2006, 9-variable Boolean functions having nonlinearity 241, which is
strictly greater than the bent concatenation bound of 240, have been discovered
in the class of Rotation Symmetric Boolean Functions (RSBFs) by Kavut, Maitra
and Yucel. To improve this nonlinearity result, we have firstly defined some
subsets of the n-variable Boolean functions as the "generalized classes of
k-RSBFs and k-DSBFs (k-Dihedral Symmetric Boolean Functions)", where k is a
positive integer dividing n and k-RSBFs is a subset of l-RSBFs if k < l.
Secondly, utilizing the steepest-descent like iterative heuristic search
algorithm used previously to identify the 9-variable RSBFs with nonlinearity
241, we have made a search within the classes of 3-RSBFs and 3-DSBFs. The
search has accomplished to find 9-variable Boolean functions with nonlinearity
242 in both of these classes. It should be emphasized that although the class
of 3-RSBFs contains functions with nonlinearity 242; 1-RSBFs or simply RSBFs,
which is a subset of 3-RSBFs, does not contain any. This result also shows that
the covering radius of the first order Reed-Muller code R(1, 9) is at least
equal to 242. Thirdly, motivated by the fact that RSBFs are invariant under a
special permutation of the input vector, we have classified all possible
permutations up to the linear equivalence of Boolean functions that are
invariant under those permutations. Specifically, for 9-variable Boolean
functions, 9! possible permutations are classified into 30 classes; and the
search algorithm identifies some of these classes as "rich". The rich classes
yield new Boolean functions with nonlinearity 242 having different
autocorrelation spectra from those of the functions found in the generalized
3-RSBF and 3-DSBF classes.
|
0808.0745
|
Relay-Assisted User Scheduling in Wireless Networks with Hybrid-ARQ
|
cs.IT math.IT
|
This paper studies the problem of relay-assisted user scheduling for downlink
wireless transmission. The base station or access point employs hybrid
automatic-repeat-request (HARQ) with the assistance of a set of fixed relays to
serve a set of mobile users. By minimizing a cost function of the queue lengths
at the base station and the number of retransmissions of the head-of-line
packet for each user, the base station can schedule an appropriate user in each
time slot and an appropriate transmitter to serve it. It is shown that a
priority-index policy is optimal for a linear cost function with packets
arriving according to a Poisson process and for an increasing convex cost
function where packets must be drained from the queues at the base station.
|
0808.0768
|
Foundations of Information Theory
|
cs.IT math.IT
|
Information is the basic concept of information theory. However, there is no
definition of this concept that can encompass all uses of the term information
in information theories and beyond. Many question a possibility of such a
definition. However, foundations of information theory developed in the context
of the general theory of information made it possible to build such a relevant
and at the same time, encompassing definition. Foundations of information
theory are built in a form of ontological principles, which reflect basic
features of information and information processes.
|
0808.0845
|
Mutual information is copula entropy
|
cs.IT cs.LG math.IT math.ST stat.TH
|
We prove that mutual information is actually negative copula entropy, based
on which a method for mutual information estimation is proposed.
|
0808.0876
|
Capacity Regions and Bounds for a Class of Z-interference Channels
|
cs.IT math.IT
|
We define a class of Z-interference channels for which we obtain a new upper
bound on the capacity region. The bound exploits a technique first introduced
by Korner and Marton. A channel in this class has the property that, for the
transmitter-receiver pair that suffers from interference, the conditional
output entropy at the receiver is invariant with respect to the transmitted
codewords. We compare the new capacity region upper bound with the
Han/Kobayashi achievable rate region for interference channels. This comparison
shows that our bound is tight in some cases, thereby yielding specific points
on the capacity region as well as sum capacity for certain Z-interference
channels. In particular, this result can be used as an alternate method to
obtain sum capacity of Gaussian Z-interference channels. We then apply an
additional restriction on our channel class: the transmitter-receiver pair that
suffers from interference achieves its maximum output entropy with a single
input distribution irrespective of the interference distribution. For these
channels we show that our new capacity region upper bound coincides with the
Han/Kobayashi achievable rate region, which is therefore capacity-achieving. In
particular, for these channels superposition encoding with partial decoding is
shown to be optimal and a single-letter characterization for the capacity
region is obtained.
|
0808.0948
|
Capacity of a Class of Diamond Channels
|
cs.IT math.IT
|
We study a special class of diamond channels which was introduced by Schein
in 2001. In this special class, each diamond channel consists of a transmitter,
a noisy relay, a noiseless relay and a receiver. We prove the capacity of this
class of diamond channels by providing an achievable scheme and a converse. The
capacity we show is strictly smaller than the cut-set bound. Our result also
shows the optimality of a combination of decode-and-forward (DAF) and
compress-and-forward (CAF) at the noisy relay node. This is the first example
where a combination of DAF and CAF is shown to be capacity achieving. Finally,
we note that there exists a duality between this diamond channel coding problem
and the Kaspi-Berger source coding problem.
|
0808.0954
|
Achievable rate regions for bi-directional relaying
|
cs.IT math.IT
|
In a bi-directional relay channel, two nodes wish to exchange independent
messages over a shared wireless half-duplex channel with the help of a relay.
In this paper, we derive achievable rate regions for four new half-duplex
protocols and compare these to four existing half-duplex protocols and outer
bounds. In time, our protocols consist of either two or three phases. In the
two phase protocols, both users simultaneously transmit during the first phase
and the relay alone transmits during the second phase, while in the three phase
protocol the two users sequentially transmit followed by a transmission from
the relay. The relay may forward information in one of four manners; we outline
existing Amplify and Forward (AF), Decode and Forward (DF) and Compress and
Forward (CF) relaying schemes and introduce the novel Mixed Forward scheme. The
latter is a combination of CF in one direction and DF in the other. We derive
achievable rate regions for the CF and Mixed relaying schemes for the two and
three phase protocols. In the last part of this work we provide a comprehensive
treatment of 8 possible half-duplex bi-directional relaying protocols in
Gaussian noise, obtaining their respective achievable rate regions, outer
bounds, and their relative performance under different SNR and relay
geometries.
|
0808.0973
|
Text Modeling using Unsupervised Topic Models and Concept Hierarchies
|
cs.AI cs.IR
|
Statistical topic models provide a general data-driven framework for
automated discovery of high-level knowledge from large collections of text
documents. While topic models can potentially discover a broad range of themes
in a data set, the interpretability of the learned topics is not always ideal.
Human-defined concepts, on the other hand, tend to be semantically richer due
to careful selection of words to define concepts but they tend not to cover the
themes in a data set exhaustively. In this paper, we propose a probabilistic
framework to combine a hierarchy of human-defined semantic concepts with
statistical topic models to seek the best of both worlds. Experimental results
using two different sources of concept hierarchies and two collections of text
documents indicate that this combination leads to systematic improvements in
the quality of the associated language models as well as enabling new
techniques for inferring and visualizing the semantics of a document.
|
0808.0978
|
Cognitive MIMO Radio: A Competitive Optimality Design Based on Subspace
Projections
|
cs.IT cs.GT math.IT
|
Cognitive MIMO Radio: A Competitive Optimality Design Based on Subspace
Projections
|
0808.0987
|
A new graph perspective on max-min fairness in Gaussian parallel
channels
|
cs.IT cs.DM math.CO math.IT
|
In this work we are concerned with the problem of achieving max-min fairness
in Gaussian parallel channels with respect to a general performance function,
including channel capacity or decoding reliability as special cases. As our
central results, we characterize the laws which determine the value of the
achievable max-min fair performance as a function of channel sharing policy and
power allocation (to channels and users). In particular, we show that the
max-min fair performance behaves as a specialized version of the Lovasz
function, or Delsarte bound, of a certain graph induced by channel sharing
combinatorics. We also prove that, in addition to such graph, merely a certain
2-norm distance dependent on the allowable power allocations and used
performance functions, is sufficient for the characterization of max-min fair
performance up to some candidate interval. Our results show also a specific
role played by odd cycles in the graph induced by the channel sharing policy
and we present an interesting relation between max-min fairness in parallel
channels and optimal throughput in an associated interference channel.
|
0808.1000
|
Fitness Landscape Analysis for Dynamic Resource Allocation in Multiuser
OFDM Based Cognitive Radio Systems
|
cs.IT cs.NE math.CO math.IT
|
This paper has been withdrawn.
|
0808.1007
|
On Quantum Capacity of Compound Channels
|
quant-ph cs.IT math-ph math.IT math.MP
|
In this paper we address the issue of universal or robust communication over
quantum channels. Specifically, we consider memoryless communication scenario
with channel uncertainty which is an analog of compound channel in classical
information theory. We determine the quantum capacity of finite compound
channels and arbitrary compound channels with informed decoder. Our approach in
the finite case is based on the observation that perfect channel knowledge at
the decoder does not increase the capacity of finite quantum compound channels.
As a consequence we obtain coding theorem for finite quantum averaged channels,
the simplest class of channels with long-term memory. The extension of these
results to quantum compound channels with uninformed encoder and decoder, and
infinitely many constituents remains an open problem.
|
0808.1125
|
Verified Null-Move Pruning
|
cs.AI
|
In this article we review standard null-move pruning and introduce our
extended version of it, which we call verified null-move pruning. In verified
null-move pruning, whenever the shallow null-move search indicates a fail-high,
instead of cutting off the search from the current node, the search is
continued with reduced depth.
Our experiments with verified null-move pruning show that on average, it
constructs a smaller search tree with greater tactical strength in comparison
to standard null-move pruning. Moreover, unlike standard null-move pruning,
which fails badly in zugzwang positions, verified null-move pruning manages to
detect most zugzwangs and in such cases conducts a re-search to obtain the
correct result. In addition, verified null-move pruning is very easy to
implement, and any standard null-move pruning program can use verified
null-move pruning by modifying only a few lines of code.
|
0808.1211
|
Commonsense Knowledge, Ontology and Ordinary Language
|
cs.AI cs.CL
|
Over two decades ago a "quite revolution" overwhelmingly replaced
knowledgebased approaches in natural language processing (NLP) by quantitative
(e.g., statistical, corpus-based, machine learning) methods. Although it is our
firm belief that purely quantitative approaches cannot be the only paradigm for
NLP, dissatisfaction with purely engineering approaches to the construction of
large knowledge bases for NLP are somewhat justified. In this paper we hope to
demonstrate that both trends are partly misguided and that the time has come to
enrich logical semantics with an ontological structure that reflects our
commonsense view of the world and the way we talk about in ordinary language.
In this paper it will be demonstrated that assuming such an ontological
structure a number of challenges in the semantics of natural language (e.g.,
metonymy, intensionality, copredication, nominal compounds, etc.) can be
properly and uniformly addressed.
|
0808.1247
|
Self-Motions of General 3-RPR Planar Parallel Robots
|
cs.RO
|
This paper studies the kinematic geometry of general 3-RPR planar parallel
robots with actuated base joints. These robots, while largely overlooked, have
simple direct kinematics and large singularity-free workspace. Furthermore,
their kinematic geometry is the same as that of a newly developed parallel
robot with SCARA-type motions. Starting from the direct and inverse kinematic
model, the expressions for the singularity loci of 3-RPR planar parallel robots
are determined. Then, the global behaviour at all singularities is
geometrically described by studying the degeneracy of the direct kinematic
model. Special cases of self-motions are then examined and the degree of
freedom gained in such special configurations is kinematically interpreted.
Finally, a practical example is discussed and experimental validations
performed on an actual robot prototype are presented.
|
0808.1368
|
On some deterministic dictionaries supporting sparsity
|
cs.IT math.IT
|
We describe a new construction of an incoherent dictionary, referred to as
the oscillator dictionary, which is based on considerations in the
representation theory of finite groups. The oscillator dictionary consists of
order of p^5 unit vectors in a Hilbert space of dimension p, where p is an odd
prime, whose pairwise inner products have magnitude of at most 4/sqrt(p). An
explicit algorithm to construct a large portion of the oscillator dictionary is
presented.
|
0808.1378
|
A Novel Symbolic Type Neural Network Model- Application to River Flow
Forecasting
|
cs.NE cs.SC
|
In this paper we introduce a new symbolic type neural tree network called
symbolic function network (SFN) that is based on using elementary functions to
model systems in a symbolic form. The proposed formulation permits feature
selection, functional selection, and flexible structure. We applied this model
on the River Flow forecasting problem. The results found to be superior in both
fitness and sparsity.
|
0808.1400
|
A Class of Maximal-Rate, Low-PAPR, Non-square Complex Orthogonal Designs
|
cs.IT math.IT
|
Space-time block codes (STBCs) from non-square complex orthogonal designs are
bandwidth efficient when compared with those from square real/complex
orthogonal designs. Though there exists rate-1 ROD for any number of transmit
antennas, rate-1 complex orthogonal designs (COD) does not exist for more than
2 transmit antennas. Liang (IEEE Trans. Inform. Theory, 2003) and Lu et al
(IEEE Trans. Inform. Theory, 2005) have constructed a class of maximal rate
non-square CODs where the rate is ${1/2}+\frac{1}{n}$ if number of transmit
antennas $n$ is even and ${1/2}+\frac{1}{n+1}$ if $n$ is odd. In this paper, we
present a simple construction for maximal rate non-square CODs obtained from
square CODs which resembles the construction of rate-1 non-square RODs from
square RODs. These designs are shown to be amenable for construction of a class
of generalized CODs (called Coordinate-Interleaved Scaled CODs) with low
peak-to-average power ratio (PAPR) having the same parameters as the maximal
rate codes. Simulation results indicate that these codes perform better than
the existing maximal rate codes under peak power constraint while performing
the same under average power constraint.
|
0808.1417
|
The finite harmonic oscillator and its associated sequences
|
cs.IT cs.CR cs.DM math-ph math.GR math.IT math.MP math.NT math.PR math.QA math.RT math.SG quant-ph
|
A system of functions (signals) on the finite line, called the oscillator
system, is described and studied. Applications of this system for discrete
radar and digital communication theory are explained.
Keywords: Weil representation, commutative subgroups, eigenfunctions, random
behavior, deterministic construction
|
0808.1455
|
Personal Semantic Web Through A Space Based Computing Environment
|
cs.NI cs.MA
|
The Semantic Web through technologies such to support the canonical
representation information and presenting it to users in a method by which its
meaning can be understood or at least communi- cated and interpreted by all
parties. As the Semantic Web evolves into more of a computing platform rather
than an information platform more dynamic structures, interactions and
behaviours will evolve leading to systems which localise and personalise this
Dynamic Semantic Web.
|
0808.1495
|
The finite harmonic oscillator and its applications to sequences,
communication and radar
|
cs.IT math.IT
|
A novel system, called the oscillator system, consisting of order of p^3
functions (signals) on the finite field F_p; with p an odd prime, is described
and studied. The new functions are proved to satisfy good auto-correlation,
cross-correlation and low peak-to-average power ratio properties. Moreover, the
oscillator system is closed under the operation of discrete Fourier transform.
Applications of the oscillator system for discrete radar and digital
communication theory are explained. Finally, an explicit algorithm to construct
the oscillator system is presented.
|
0808.1508
|
Comparison between CPBPV, ESC/Java, CBMC, Blast, EUREKA and Why for
Bounded Program Verification
|
cs.SE cs.AI cs.LO
|
This report describes experimental results for a set of benchmarks on program
verification. It compares the capabilities of CPBVP "Constraint Programming
framework for Bounded Program Verification" [4] with the following frameworks:
ESC/Java, CBMC, Blast, EUREKA and Why.
|
0808.1661
|
Medical robotics: where we come from, where we are and where we could go
|
cs.RO
|
This short note presents a viewpoint about medical robotics.
|
0808.1721
|
Initial Results on the F-logic to OWL Bi-directional Translation on a
Tabled Prolog Engine
|
cs.AI cs.SE
|
In this paper, we show our results on the bi-directional data exchange
between the F-logic language supported by the Flora2 system and the OWL
language. Most of the TBox and ABox axioms are translated preserving the
semantics between the two representations, such as: proper inclusion,
individual definition, functional properties, while some axioms and
restrictions require a change in the semantics, such as: numbered and qualified
cardinality restrictions. For the second case, we translate the OWL definite
style inference rules into F-logic style constraints. We also describe a set of
reasoning examples using the above translation, including the reasoning in
Flora2 of a variety of ABox queries.
|
0808.1753
|
Index wiki database: design and experiments
|
cs.IR cs.CL
|
With the fantastic growth of Internet usage, information search in documents
of a special type called a "wiki page" that is written using a simple markup
language, has become an important problem. This paper describes the software
architectural model for indexing wiki texts in three languages (Russian,
English, and German) and the interaction between the software components (GATE,
Lemmatizer, and Synarcher). The inverted file index database was designed using
visual tool DBDesigner. The rules for parsing Wikipedia texts are illustrated
by examples. Two index databases of Russian Wikipedia (RW) and Simple English
Wikipedia (SEW) are built and compared. The size of RW is by order of magnitude
higher than SEW (number of words, lexemes), though the growth rate of number of
pages in SEW was found to be 14% higher than in Russian, and the rate of
acquisition of new words in SEW lexicon was 7% higher during a period of five
months (from September 2007 to February 2008). The Zipf's law was tested with
both Russian and Simple Wikipedias. The entire source code of the indexing
software and the generated index databases are freely available under GPL (GNU
General Public License).
|
0808.2059
|
Diversity-Multiplexing Tradeoffs in MIMO Relay Channels
|
cs.IT math.IT
|
A multi-hop relay channel with multiple antenna terminals in a quasi-static
slow fading environment is considered. For both full-duplex and half-duplex
relays the fundamental diversity-multiplexing tradeoff (DMT) is analyzed. It is
shown that, while decode-and-forward (DF) relaying achieves the optimal DMT in
the full-duplex relay scenario, the dynamic decode-and-forward (DDF) protocol
is needed to achieve the optimal DMT if the relay is constrained to half-duplex
operation. For the latter case, static protocols are considered as well, and
the corresponding achievable DMT performance is characterized.
|
0808.2073
|
Lower Bounds on the Rate-Distortion Function of LDGM Codes
|
cs.IT math.IT
|
A recent line of work has focused on the use of low-density generator matrix
(LDGM) codes for lossy source coding. In this paper, wedevelop a generic
technique for deriving lower bounds on the rate-distortion functions of binary
linear codes, with particular interest on the effect of bounded degrees. The
underlying ideas can be viewing as the source coding analog of the classical
result of Gallager, providing bounds for channel coding over the binary
symmetric channel using bounded degree LDPC codes. We illustrate this method
for different random ensembles of LDGM codes, including the check-regular
ensemble and bit-check-regular ensembles, by deriving explicit lower bounds on
their rate-distortion performance as a function of the degrees.
|
0808.2083
|
Histogram-Aware Sorting for Enhanced Word-Aligned Compression in Bitmap
Indexes
|
cs.DB
|
Bitmap indexes must be compressed to reduce input/output costs and minimize
CPU usage. To accelerate logical operations (AND, OR, XOR) over bitmaps, we use
techniques based on run-length encoding (RLE), such as Word-Aligned Hybrid
(WAH) compression. These techniques are sensitive to the order of the rows: a
simple lexicographical sort can divide the index size by 9 and make indexes
several times faster. We investigate reordering heuristics based on computed
attribute-value histograms. Simply permuting the columns of the table based on
these histograms can increase the sorting efficiency by 40%.
|
0808.2089
|
Capacity-achieving Feedback Scheme for Gaussian Finite-State Markov
Channels with Channel State Information
|
cs.IT math.IT
|
In this paper, we propose capacity-achieving communication schemes for
Gaussian finite-state Markov channels (FSMCs) subject to an average channel
input power constraint, under the assumption that the transmitters can have
access to delayed noiseless output feedback as well as instantaneous or delayed
channel state information (CSI). We show that the proposed schemes reveals
connections between feedback communication and feedback control.
|
0808.2092
|
On zero-rate error exponent for BSC with noisy feedback
|
cs.IT math.IT
|
For the information transmission a binary symmetric channel is used. There is
also another noisy binary symmetric channel (feedback channel), and the
transmitter observes without delay all the outputs of the forward channel via
that feedback channel. The transmission of a nonexponential number of messages
(i.e. the transmission rate equals zero) is considered. The achievable decoding
error exponent for such a combination of channels is investigated. It is shown
that if the crossover probability of the feedback channel is less than a
certain positive value, then the achievable error exponent is better than the
similar error exponent of the no-feedback channel.
The transmission method described and the corresponding lower bound for the
error exponent can be strengthened, and also extended to the positive
transmission rates.
|
0808.2181
|
Spectrum Sharing Between Cellular and Mobile Ad Hoc Networks:
Transmission-Capacity Trade-Off
|
cs.IT math.IT
|
Spectrum sharing between wireless networks improves the efficiency of
spectrum usage, and thereby alleviates spectrum scarcity due to growing demands
for wireless broadband access. To improve the usual underutilization of the
cellular uplink spectrum, this paper studies spectrum sharing between a
cellular uplink and a mobile ad hoc networks. These networks access either all
frequency sub-channels or their disjoint sub-sets, called spectrum underlay and
spectrum overlay, respectively. Given these spectrum sharing methods, the
capacity trade-off between the coexisting networks is analyzed based on the
transmission capacity of a network with Poisson distributed transmitters. This
metric is defined as the maximum density of transmitters subject to an outage
constraint for a given signal-to-interference ratio (SIR). Using tools from
stochastic geometry, the transmission-capacity trade-off between the coexisting
networks is analyzed, where both spectrum overlay and underlay as well as
successive interference cancelation (SIC) are considered. In particular, for
small target outage probability, the transmission capacities of the coexisting
networks are proved to satisfy a linear equation, whose coefficients depend on
the spectrum sharing method and whether SIC is applied. This linear equation
shows that spectrum overlay is more efficient than spectrum underlay.
Furthermore, this result also provides insight into the effects of different
network parameters on transmission capacities, including link diversity gains,
transmission distances, and the base station density. In particular, SIC is
shown to increase transmission capacities of both coexisting networks by a
linear factor, which depends on the interference-power threshold for qualifying
canceled interferers.
|
0808.2227
|
Higher Order Moments Generation by Mellin Transform for Compound Models
of Clutter
|
cs.CV
|
The compound models of clutter statistics are found suitable to describe the
nonstationary nature of radar backscattering from high-resolution observations.
In this letter, we show that the properties of Mellin transform can be utilized
to generate higher order moments of simple and compound models of clutter
statistics in a compact manner.
|
0808.2314
|
Capacity of Symmetric K-User Gaussian Very Strong Interference Channels
|
cs.IT math.IT
|
This paper studies a symmetric K user Gaussian interference channel with K
transmitters and K receivers. A "very strong" interference regime is derived
for this channel setup. A "very strong" interference regime is one where the
capacity region of the interference channel is the same as the capacity region
of the channel with no interference. In this regime, the interference can be
perfectly canceled by all the receivers without incurring any rate penalties. A
"very strong" interference condition for an example symmetric K user
deterministic interference channel is also presented.
|
0808.2486
|
Wet Paper Coding for Watermarking of Binary Images
|
cs.IT cs.CR math.IT
|
We propose a new method to embed data in binary images, including scanned
text, figures, and signatures. Our method relies on the concept of wet paper
codes. The shuffling before embedding is used in order to equalize irregular
embedding capacity from diverse areas in the image. The hidden data can be
extracted without the original binary image. We illustrate some examples of
watermarked binary images after wet paper coding.
|
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