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0902.0465
|
AxialGen: A Research Prototype for Automatically Generating the Axial
Map
|
cs.RO cs.CG
|
AxialGen is a research prototype for automatically generating the axial map,
which consists of the least number of the longest visibility lines (or axial
lines) for representing individual linearly stretched parts of open space of an
urban environment. Open space is the space between closed spaces such as
buildings and street blocks. This paper aims to provide an accessible guide to
software AxialGen, and the underlying concepts and ideas. We concentrate on the
explanation and illustration of the key concept of bucket: its definition,
formation and how it is used in generating the axial map.
Keywords: Bucket, visibility, medial axes, axial lines, isovists, axial map
|
0902.0514
|
Graphical Reasoning in Compact Closed Categories for Quantum Computation
|
cs.SC cs.AI
|
Compact closed categories provide a foundational formalism for a variety of
important domains, including quantum computation. These categories have a
natural visualisation as a form of graphs. We present a formalism for
equational reasoning about such graphs and develop this into a generic proof
system with a fixed logical kernel for equational reasoning about compact
closed categories. Automating this reasoning process is motivated by the slow
and error prone nature of manual graph manipulation. A salient feature of our
system is that it provides a formal and declarative account of derived results
that can include `ellipses'-style notation. We illustrate the framework by
instantiating it for a graphical language of quantum computation and show how
this can be used to perform symbolic computation.
|
0902.0562
|
A Unified Perspective on Parity- and Syndrome-Based Binary Data
Compression Using Off-the-Shelf Turbo Codecs
|
cs.IT math.IT
|
We consider the problem of compressing memoryless binary data with or without
side information at the decoder. We review the parity- and the syndrome-based
approaches and discuss their theoretical limits, assuming that there exists a
virtual binary symmetric channel between the source and the side information,
and that the source is not necessarily uniformly distributed. We take a
factor-graph-based approach in order to devise how to take full advantage of
the ready-available iterative decoding procedures when turbo codes are
employed, in both a parity- or a syndrome-based fashion. We end up obtaining a
unified decoder formulation that holds both for error-free and for error-prone
encoder-to-decoder transmission over generic channels. To support the
theoretical results, the different compression systems analyzed in the paper
are also experimentally tested. They are compared against several different
approaches proposed in literature and shown to be competitive in a variety of
cases.
|
0902.0606
|
Beyond Zipf's law: Modeling the structure of human language
|
cs.CL physics.soc-ph
|
Human language, the most powerful communication system in history, is closely
associated with cognition. Written text is one of the fundamental
manifestations of language, and the study of its universal regularities can
give clues about how our brains process information and how we, as a society,
organize and share it. Still, only classical patterns such as Zipf's law have
been explored in depth. In contrast, other basic properties like the existence
of bursts of rare words in specific documents, the topical organization of
collections, or the sublinear growth of vocabulary size with the length of a
document, have only been studied one by one and mainly applying heuristic
methodologies rather than basic principles and general mechanisms. As a
consequence, there is a lack of understanding of linguistic processes as
complex emergent phenomena. Beyond Zipf's law for word frequencies, here we
focus on Heaps' law, burstiness, and the topicality of document collections,
which encode correlations within and across documents absent in random null
models. We introduce and validate a generative model that explains the
simultaneous emergence of all these patterns from simple rules. As a result, we
find a connection between the bursty nature of rare words and the topical
organization of texts and identify dynamic word ranking and memory across
documents as key mechanisms explaining the non trivial organization of written
text. Our research can have broad implications and practical applications in
computer science, cognitive science, and linguistics.
|
0902.0657
|
Efficient implementation of linear programming decoding
|
cs.IT math.IT
|
While linear programming (LP) decoding provides more flexibility for
finite-length performance analysis than iterative message-passing (IMP)
decoding, it is computationally more complex to implement in its original form,
due to both the large size of the relaxed LP problem, and the inefficiency of
using general-purpose LP solvers. This paper explores ideas for fast LP
decoding of low-density parity-check (LDPC) codes. We first prove, by modifying
the previously reported Adaptive LP decoding scheme to allow removal of
unnecessary constraints, that LP decoding can be performed by solving a number
of LP problems that contain at most one linear constraint derived from each of
the parity-check constraints. By exploiting this property, we study a sparse
interior-point implementation for solving this sequence of linear programs.
Since the most complex part of each iteration of the interior-point algorithm
is the solution of a (usually ill-conditioned) system of linear equations for
finding the step direction, we propose a preconditioning algorithm to
facilitate iterative solution of such systems. The proposed preconditioning
algorithm is similar to the encoding procedure of LDPC codes, and we
demonstrate its effectiveness via both analytical methods and computer
simulation results.
|
0902.0668
|
Application of the Weil representation: diagonalization of the discrete
Fourier transform
|
cs.IT cs.DM math.IT math.RT
|
We survey a new application of the Weil representation to construct a
canonical basis of eigenvectors for the discrete Fourier transform (DFT). The
transition matrix from the standard basis to the canonical basis defines a
novel transform which we call the discrete oscillator transform (DOT for
short). In addition, we describe a fast algorithm for computing the DOT in
certain cases.
|
0902.0673
|
Optimal profiles in variable speed flows
|
math.HO cs.CE math.OC physics.flu-dyn
|
Where a 2D problem of optimal profile in variable speed flow is resolved in a
class of convex Bezier curves, using symbolic and numerical computations.
|
0902.0744
|
Embedding Data within Knowledge Spaces
|
cs.AI cs.HC cs.IR
|
The promise of e-Science will only be realized when data is discoverable,
accessible, and comprehensible within distributed teams, across disciplines,
and over the long-term--without reliance on out-of-band (non-digital) means. We
have developed the open-source Tupelo semantic content management framework and
are employing it to manage a wide range of e-Science entities (including data,
documents, workflows, people, and projects) and a broad range of metadata
(including provenance, social networks, geospatial relationships, temporal
relations, and domain descriptions). Tupelo couples the use of global
identifiers and resource description framework (RDF) statements with an
aggregatable content repository model to provide a unified space for securely
managing distributed heterogeneous content and relationships.
|
0902.0763
|
Genetic algorithm based optimization and post optimality analysis of
multi-pass face milling
|
cs.CE
|
This paper presents an optimization technique for the multi-pass face milling
process. Genetic algorithm (GA) is used to obtain the optimum cutting
parameters by minimizing the unit production cost for a given amount of
material removal. Cutting speed, feed and depth of cut for the finish and rough
passes are the cutting parameters. An equal depth of cut for roughing passes
has been considered. A lookup table containing the feasible combinations of
depth of cut in finish and rough passes is generated so as to reduce the number
of variables by one. The resulting mixed integer nonlinear optimization problem
is solved in a single step using GA. The entire technique is demonstrated in a
case study. Post optimality analysis of the example problem is done to develop
a strategy for optimizing without running GA again for different values of
total depth of cut.
|
0902.0798
|
Alleviating Media Bias Through Intelligent Agent Blogging
|
cs.AI
|
Consumers of mass media must have a comprehensive, balanced and plural
selection of news to get an unbiased perspective; but achieving this goal can
be very challenging, laborious and time consuming. News stories development
over time, its (in)consistency, and different level of coverage across the
media outlets are challenges that a conscientious reader has to overcome in
order to alleviate bias.
In this paper we present an intelligent agent framework currently
facilitating analysis of the main sources of on-line news in El Salvador. We
show how prior tools of text analysis and Web 2.0 technologies can be combined
with minimal manual intervention to help individuals on their rational decision
process, while holding media outlets accountable for their work.
|
0902.0822
|
Bootstrapped Oblivious Transfer and Secure Two-Party Function
Computation
|
cs.CR cs.IT math.IT
|
We propose an information theoretic framework for the secure two-party
function computation (SFC) problem and introduce the notion of SFC capacity. We
study and extend string oblivious transfer (OT) to sample-wise OT. We propose
an efficient, perfectly private OT protocol utilizing the binary erasure
channel or source. We also propose the bootstrap string OT protocol which
provides disjoint (weakened) privacy while achieving a multiplicative increase
in rate, thus trading off security for rate. Finally, leveraging our OT
protocol, we construct a protocol for SFC and establish a general lower bound
on SFC capacity of the binary erasure channel and source.
|
0902.0838
|
The Ergodic Capacity of Phase-Fading Interference Networks
|
cs.IT math.IT
|
We identify the role of equal strength interference links as bottlenecks on
the ergodic sum capacity of a $K$ user phase-fading interference network, i.e.,
an interference network where the fading process is restricted primarily to
independent and uniform phase variations while the channel magnitudes are held
fixed across time. It is shown that even though there are $K(K-1)$ cross-links,
only about $K/2$ disjoint and equal strength interference links suffice to
determine the capacity of the network regardless of the strengths of the rest
of the cross channels. This scenario is called a \emph{minimal bottleneck
state}. It is shown that ergodic interference alignment is capacity optimal for
a network in a minimal bottleneck state. The results are applied to large
networks. It is shown that large networks are close to bottleneck states with a
high probability, so that ergodic interference alignment is close to optimal
for large networks. Limitations of the notion of bottleneck states are also
highlighted for channels where both the phase and the magnitudes vary with
time. It is shown through an example that for these channels, joint coding
across different bottleneck states makes it possible to circumvent the capacity
bottlenecks.
|
0902.0892
|
A Unified Framework for Linear-Programming Based Communication Receivers
|
cs.IT math.IT
|
It is shown that a large class of communication systems which admit a
sum-product algorithm (SPA) based receiver also admit a corresponding
linear-programming (LP) based receiver. The two receivers have a relationship
defined by the local structure of the underlying graphical model, and are
inhibited by the same phenomenon, which we call 'pseudoconfigurations'. This
concept is a generalization of the concept of 'pseudocodewords' for linear
codes. It is proved that the LP receiver has the 'maximum likelihood
certificate' property, and that the receiver output is the lowest cost
pseudoconfiguration. Equivalence of graph-cover pseudoconfigurations and
linear-programming pseudoconfigurations is also proved. A concept of 'system
pseudodistance' is defined which generalizes the existing concept of
pseudodistance for binary and nonbinary linear codes. It is demonstrated how
the LP design technique may be applied to the problem of joint equalization and
decoding of coded transmissions over a frequency selective channel, and a
simulation-based analysis of the error events of the resulting LP receiver is
also provided. For this particular application, the proposed LP receiver is
shown to be competitive with other receivers, and to be capable of
outperforming turbo equalization in bit and frame error rate performance.
|
0902.0899
|
Comparative concept similarity over Minspaces: Axiomatisation and
Tableaux Calculus
|
cs.AI
|
We study the logic of comparative concept similarity $\CSL$ introduced by
Sheremet, Tishkovsky, Wolter and Zakharyaschev to capture a form of qualitative
similarity comparison. In this logic we can formulate assertions of the form "
objects A are more similar to B than to C". The semantics of this logic is
defined by structures equipped by distance functions evaluating the similarity
degree of objects. We consider here the particular case of the semantics
induced by \emph{minspaces}, the latter being distance spaces where the minimum
of a set of distances always exists. It turns out that the semantics over
arbitrary minspaces can be equivalently specified in terms of preferential
structures, typical of conditional logics. We first give a direct
axiomatisation of this logic over Minspaces. We next define a decision
procedure in the form of a tableaux calculus. Both the calculus and the
axiomatisation take advantage of the reformulation of the semantics in terms of
preferential structures.
|
0902.0947
|
On the Gaussian MAC with Imperfect Feedback
|
cs.IT math.IT
|
New achievable rate regions are derived for the two-user additive white
Gaussian multiple-access channel with noisy feedback. The regions exhibit the
following two properties. Irrespective of the (finite) Gaussian feedback-noise
variances, the regions include rate points that lie outside the no-feedback
capacity region, and when the feedback-noise variances tend to 0 the regions
converge to the perfect-feedback capacity region. The new achievable regions
also apply to the partial-feedback setting where one of the transmitters has a
noisy feedback link and the other transmitter has no feedback at all. Again,
irrespective of the (finite) noise variance on the feedback link, the regions
include rate points that lie outside the no-feedback capacity region. Moreover,
in the case of perfect partial feedback, i.e., where the only feedback link is
noise-free, for certain channel parameters the new regions include rate points
that lie outside the Cover-Leung region. This answers in the negative the
question posed by van der Meulen as to whether the Cover-Leung region equals
the capacity region of the Gaussian multiple-access channel with perfect
partial feedback. Finally, we propose new achievable regions also for a setting
where the receiver is cognizant of the realizations of the noise sequences on
the feedback links.
|
0902.0966
|
Beam Selection Gain Versus Antenna Selection Gain
|
cs.IT math.IT
|
We consider beam selection using a fixed beamforming network (FBN) at a base
station with $M$ array antennas. In our setting, a Butler matrix is deployed at
the RF stage to form $M$ beams, and then the best beam is selected for
transmission. We provide the proofs of the key properties of the noncentral
chi-square distribution and the following properties of the beam selection gain
verifying that beam selection is superior to antenna selection in Rician
channels with any $K$-factors. Furthermore, we find asymptotically tight
stochastic bounds of the beam selection gain, which yield approximate closed
form expressions of the expected selection gain and the ergodic capacity. Beam
selection has the order of growth of the ergodic capacity
$\mathnormal{\Theta}(\log(M))$ regardless of user location in contrast to
$\mathnormal{\Theta}(\log(\log(M)))$ for antenna selection.
|
0902.1033
|
New Confidence Measures for Statistical Machine Translation
|
cs.CL
|
A confidence measure is able to estimate the reliability of an hypothesis
provided by a machine translation system. The problem of confidence measure can
be seen as a process of testing : we want to decide whether the most probable
sequence of words provided by the machine translation system is correct or not.
In the following we describe several original word-level confidence measures
for machine translation, based on mutual information, n-gram language model and
lexical features language model. We evaluate how well they perform individually
or together, and show that using a combination of confidence measures based on
mutual information yields a classification error rate as low as 25.1% with an
F-measure of 0.708.
|
0902.1037
|
Optimal design and optimal control of structures undergoing finite
rotations and elastic deformations
|
cs.NE cs.CE
|
In this work we deal with the optimal design and optimal control of
structures undergoing large rotations. In other words, we show how to find the
corresponding initial configuration and the corresponding set of multiple load
parameters in order to recover a desired deformed configuration or some
desirable features of the deformed configuration as specified more precisely by
the objective or cost function. The model problem chosen to illustrate the
proposed optimal design and optimal control methodologies is the one of
geometrically exact beam. First, we present a non-standard formulation of the
optimal design and optimal control problems, relying on the method of Lagrange
multipliers in order to make the mechanics state variables independent from
either design or control variables and thus provide the most general basis for
developing the best possible solution procedure. Two different solution
procedures are then explored, one based on the diffuse approximation of
response function and gradient method and the other one based on genetic
algorithm. A number of numerical examples are given in order to illustrate both
the advantages and potential drawbacks of each of the presented procedures.
|
0902.1040
|
Fast solving of Weighted Pairing Least-Squares systems
|
cs.MS cs.NE
|
This paper presents a generalization of the "weighted least-squares" (WLS),
named "weighted pairing least-squares" (WPLS), which uses a rectangular weight
matrix and is suitable for data alignment problems. Two fast solving methods,
suitable for solving full rank systems as well as rank deficient systems, are
studied. Computational experiments clearly show that the best method, in terms
of speed, accuracy, and numerical stability, is based on a special {1, 2,
3}-inverse, whose computation reduces to a very simple generalization of the
usual "Cholesky factorization-backward substitution" method for solving linear
systems.
|
0902.1041
|
Kolmogorov Complexity and Solovay Functions
|
cs.CC cs.IT math.IT math.LO
|
Solovay proved that there exists a computable upper bound f of the
prefix-free Kolmogorov complexity function K such that f (x) = K(x) for
infinitely many x. In this paper, we consider the class of computable functions
f such that K(x) <= f (x)+O(1) for all x and f (x) <= K(x) + O(1) for
infinitely many x, which we call Solovay functions. We show that Solovay
functions present interesting connections with randomness notions such as
Martin-L\"of randomness and K-triviality.
|
0902.1080
|
A Model for Managing Collections of Patterns
|
cs.AI
|
Data mining algorithms are now able to efficiently deal with huge amount of
data. Various kinds of patterns may be discovered and may have some great
impact on the general development of knowledge. In many domains, end users may
want to have their data mined by data mining tools in order to extract patterns
that could impact their business. Nevertheless, those users are often
overwhelmed by the large quantity of patterns extracted in such a situation.
Moreover, some privacy issues, or some commercial one may lead the users not to
be able to mine the data by themselves. Thus, the users may not have the
possibility to perform many experiments integrating various constraints in
order to focus on specific patterns they would like to extract. Post processing
of patterns may be an answer to that drawback. Thus, in this paper we present a
framework that could allow end users to manage collections of patterns. We
propose to use an efficient data structure on which some algebraic operators
may be used in order to retrieve or access patterns in pattern bases.
|
0902.1179
|
The Complexity of Datalog on Linear Orders
|
cs.LO cs.CC cs.DB
|
We study the program complexity of datalog on both finite and infinite linear
orders. Our main result states that on all linear orders with at least two
elements, the nonemptiness problem for datalog is EXPTIME-complete. While
containment of the nonemptiness problem in EXPTIME is known for finite linear
orders and actually for arbitrary finite structures, it is not obvious for
infinite linear orders. It sharply contrasts the situation on other infinite
structures; for example, the datalog nonemptiness problem on an infinite
successor structure is undecidable. We extend our upper bound results to
infinite linear orders with constants.
As an application, we show that the datalog nonemptiness problem on Allen's
interval algebra is EXPTIME-complete.
|
0902.1220
|
Opportunistic Communications in Fading Multiaccess Relay Channels
|
cs.IT math.IT
|
The problem of optimal resource allocation is studied for ergodic fading
orthogonal multiaccess relay channels (MARCs) in which the users (sources)
communicate with a destination with the aid of a half-duplex relay that
transmits on a channel orthogonal to that used by the transmitting sources.
Under the assumption that the instantaneous fading state information is
available at all nodes, the maximum sum-rate and the optimal user and relay
power allocations (policies) are developed for a decode-and-forward (DF) relay.
With the observation that a DF relay results in two multiaccess channels, one
at the relay and the other at the destination, a single known lemma on the
sum-rate of two intersecting polymatroids is used to determine the DF sum-rate
and the optimal user and relay policies. The lemma also enables a broad
topological classification of fading MARCs into one of three types. The first
type is the set of partially clustered MARCs where a user is clustered either
with the relay or with the destination such that the users waterfill on their
bottle-neck links to the distant receiver. The second type is the set of
clustered MARCs where all users are either proximal to the relay or to the
destination such that opportunistic multiuser scheduling to one of the
receivers is optimal. The third type consists of arbitrarily clustered MARCs
which are a combination of the first two types, and for this type it is shown
that the optimal policies are opportunistic non-waterfilling solutions. The
analysis is extended to develop the rate region of a K-user orthogonal
half-duplex MARC. Finally, cutset outer bounds are used to show that DF
achieves the capacity region for a class of clustered orthogonal half-duplex
MARCs.
|
0902.1227
|
Discovering general partial orders in event streams
|
cs.AI cs.LG
|
Frequent episode discovery is a popular framework for pattern discovery in
event streams. An episode is a partially ordered set of nodes with each node
associated with an event type. Efficient (and separate) algorithms exist for
episode discovery when the associated partial order is total (serial episode)
and trivial (parallel episode). In this paper, we propose efficient algorithms
for discovering frequent episodes with general partial orders. These algorithms
can be easily specialized to discover serial or parallel episodes. Also, the
algorithms are flexible enough to be specialized for mining in the space of
certain interesting subclasses of partial orders. We point out that there is an
inherent combinatorial explosion in frequent partial order mining and most
importantly, frequency alone is not a sufficient measure of interestingness. We
propose a new interestingness measure for general partial order episodes and a
discovery method based on this measure, for filtering out uninteresting partial
orders. Simulations demonstrate the effectiveness of our algorithms.
|
0902.1258
|
Extraction de concepts sous contraintes dans des donn\'ees d'expression
de g\`enes
|
cs.LG
|
In this paper, we propose a technique to extract constrained formal concepts.
|
0902.1259
|
Database Transposition for Constrained (Closed) Pattern Mining
|
cs.LG
|
Recently, different works proposed a new way to mine patterns in databases
with pathological size. For example, experiments in genome biology usually
provide databases with thousands of attributes (genes) but only tens of objects
(experiments). In this case, mining the "transposed" database runs through a
smaller search space, and the Galois connection allows to infer the closed
patterns of the original database. We focus here on constrained pattern mining
for those unusual databases and give a theoretical framework for database and
constraint transposition. We discuss the properties of constraint transposition
and look into classical constraints. We then address the problem of generating
the closed patterns of the original database satisfying the constraint,
starting from those mined in the "transposed" database. Finally, we show how to
generate all the patterns satisfying the constraint from the closed ones.
|
0902.1267
|
A Note on the Diagonalization of the Discrete Fourier Transform
|
cs.IT cs.DM math.IT math.RT
|
Following the approach developed by S. Gurevich and R. Hadani, an analytical
formula of the canonical basis of the DFT is given for the case $N=p$ where $p$
is a prime number and $p\equiv 1$ (mod 4).
|
0902.1275
|
Delay Performance Optimization for Multiuser Diversity Systems with
Bursty-Traffic and Heterogeneous Wireless Links
|
cs.IT math.IT
|
This paper presents a cross-layer approach for optimizing the delay
performance of a multiuser diversity system with heterogeneous block-fading
channels and a delay-sensitive bursty-traffic. We consider the downlink of a
time-slotted multiuser system employing opportunistic scheduling with fair
performance at the medium access (MAC) layer and adaptive modulation and coding
(AMC) with power control at the physical layer. Assuming individual user
buffers which temporarily store the arrival traffic of users at the MAC layer,
we first present a large deviations based statistical model to evaluate the
delay-bound violation of packets in the user buffers. Aiming at minimizing the
delay probability of the individual users, we then optimize the AMC and power
control module subject to a target packet-error rate constraint. In the case of
a quantized feedback channel, we also present a constant-power AMC based
opportunistic scheduling scheme. Numerical and simulation results are provided
to evaluate the delay performance of the proposed adaptation schemes in a
multiuser setup.
|
0902.1278
|
Fountain Codes Based Distributed Storage Algorithms for Large-scale
Wireless Sensor Networks
|
cs.IT cs.DS cs.NI math.IT
|
We consider large-scale sensor networks with n nodes, out of which k are in
possession, (e.g., have sensed or collected in some other way) k information
packets. In the scenarios in which network nodes are vulnerable because of, for
example, limited energy or a hostile environment, it is desirable to
disseminate the acquired information throughout the network so that each of the
n nodes stores one (possibly coded) packet and the original k source packets
can be recovered later in a computationally simple way from any (1 + \epsilon)k
nodes for some small \epsilon > 0.
We developed two distributed algorithms for solving this problem based on
simple random walks and Fountain codes. Unlike all previously developed
schemes, our solution is truly distributed, that is, nodes do not know n, k or
connectivity in the network, except in their own neighborhoods, and they do not
maintain any routing tables. In the first algorithm, all the sensors have the
knowledge of n and k. In the second algorithm, each sensor estimates these
parameters through the random walk dissemination. We present analysis of the
communication/transmission and encoding/decoding complexity of these two
algorithms, and provide extensive simulation results as well
|
0902.1284
|
Multi-Label Prediction via Compressed Sensing
|
cs.LG
|
We consider multi-label prediction problems with large output spaces under
the assumption of output sparsity -- that the target (label) vectors have small
support. We develop a general theory for a variant of the popular error
correcting output code scheme, using ideas from compressed sensing for
exploiting this sparsity. The method can be regarded as a simple reduction from
multi-label regression problems to binary regression problems. We show that the
number of subproblems need only be logarithmic in the total number of possible
labels, making this approach radically more efficient than others. We also
state and prove robustness guarantees for this method in the form of regret
transform bounds (in general), and also provide a more detailed analysis for
the linear prediction setting.
|
0902.1299
|
Perfect Quantum Network Communication Protocol Based on Classical
Network Coding
|
quant-ph cs.IT math.IT
|
This paper considers a problem of quantum communication between parties that
are connected through a network of quantum channels. The model in this paper
assumes that there is no prior entanglement shared among any of the parties,
but that classical communication is free. The task is to perfectly transfer an
unknown quantum state from a source subsystem to a target subsystem, where both
source and target are formed by ordered sets of some of the nodes. It is proved
that a lower bound of the rate at which this quantum communication task is
possible is given by the classical min-cut max-flow theorem of network coding,
where the capacities in question are the quantum capacities of the edges of the
network.
|
0902.1351
|
On the minimum distance graph of an extended Preparata code
|
cs.IT cs.DM math.IT
|
The minimum distance graph of an extended Preparata code P(m) has vertices
corresponding to codewords and edges corresponding to pairs of codewords that
are distance 6 apart. The clique structure of this graph is investigated and it
is established that the minimum distance graphs of two extended Preparata codes
are isomorphic if and only if the codes are equivalent.
|
0902.1475
|
Personalised and Dynamic Trust in Social Networks
|
cs.CY cs.IR physics.soc-ph
|
We propose a novel trust metric for social networks which is suitable for
application in recommender systems. It is personalised and dynamic and allows
to compute the indirect trust between two agents which are not neighbours based
on the direct trust between agents that are neighbours. In analogy to some
personalised versions of PageRank, this metric makes use of the concept of
feedback centrality and overcomes some of the limitations of other trust
metrics.In particular, it does not neglect cycles and other patterns
characterising social networks, as some other algorithms do. In order to apply
the metric to recommender systems, we propose a way to make trust dynamic over
time. We show by means of analytical approximations and computer simulations
that the metric has the desired properties. Finally, we carry out an empirical
validation on a dataset crawled from an Internet community and compare the
performance of a recommender system using our metric to one using collaborative
filtering.
|
0902.1505
|
On the Bures Volume of Separable Quantum States
|
quant-ph cs.IT math.FA math.IT math.MG
|
We obtain two sided estimates for the Bures volume of an arbitrary subset of
the set of $N\times N$ density matrices, in terms of the Hilbert-Schmidt volume
of that subset. For general subsets, our results are essentially optimal (for
large $N$). As applications, we derive in particular nontrivial lower and upper
bounds for the Bures volume of sets of separable states and for sets of states
with positive partial transpose.
PACS numbers: 02.40.Ft, 03.65.Db, 03.65.Ud, 03.67.Mn
|
0902.1591
|
Correlated Sources over Broadcast Channels
|
cs.IT math.IT
|
The problem of reliable transmission of correlated sources over the broadcast
channel, originally studied by Han and Costa, is revisited. An alternative
characterization of their sufficient condition for reliable transmission is
given, which includes results of Marton for channel coding over broadcast
channels and of Gray and Wyner for distributed source coding. A
``minimalistic'' coding scheme is presented, which is based on joint typicality
encoding and decoding, without requiring the use of Cover's superposition
coding, random hashing, and common part between two sources. The analysis of
the coding scheme is also conceptually simple and relies on a new multivariate
covering lemma and an application of the Fourier--Motzkin elimination
procedure.
|
0902.1629
|
Improvements of real coded genetic algorithms based on differential
operators preventing premature convergence
|
cs.NE cs.AI
|
This paper presents several types of evolutionary algorithms (EAs) used for
global optimization on real domains. The interest has been focused on
multimodal problems, where the difficulties of a premature convergence usually
occurs. First the standard genetic algorithm (SGA) using binary encoding of
real values and its unsatisfactory behavior with multimodal problems is briefly
reviewed together with some improvements of fighting premature convergence. Two
types of real encoded methods based on differential operators are examined in
detail: the differential evolution (DE), a very modern and effective method
firstly published by R. Storn and K. Price, and the simplified real-coded
differential genetic algorithm SADE proposed by the authors. In addition, an
improvement of the SADE method, called CERAF technology, enabling the
population of solutions to escape from local extremes, is examined. All methods
are tested on an identical set of objective functions and a systematic
comparison based on a reliable methodology is presented. It is confirmed that
real coded methods generally exhibit better behavior on real domains than the
binary algorithms, even when extended by several improvements. Furthermore, the
positive influence of the differential operators due to their possibility of
self-adaptation is demonstrated. From the reliability point of view, it seems
that the real encoded differential algorithm, improved by the technology
described in this paper, is a universal and reliable method capable of solving
all proposed test problems.
|
0902.1634
|
A bound on the size of linear codes
|
cs.IT math.IT
|
We present a bound on the size of linear codes. This bound is independent of
other known bounds, e.g. the Griesmer bound.
|
0902.1647
|
A competitive comparison of different types of evolutionary algorithms
|
cs.NE cs.AI
|
This paper presents comparison of several stochastic optimization algorithms
developed by authors in their previous works for the solution of some problems
arising in Civil Engineering. The introduced optimization methods are: the
integer augmented simulated annealing (IASA), the real-coded augmented
simulated annealing (RASA), the differential evolution (DE) in its original
fashion developed by R. Storn and K. Price and simplified real-coded
differential genetic algorithm (SADE). Each of these methods was developed for
some specific optimization problem; namely the Chebychev trial polynomial
problem, the so called type 0 function and two engineering problems - the
reinforced concrete beam layout and the periodic unit cell problem
respectively. Detailed and extensive numerical tests were performed to examine
the stability and efficiency of proposed algorithms. The results of our
experiments suggest that the performance and robustness of RASA, IASA and SADE
methods are comparable, while the DE algorithm performs slightly worse. This
fact together with a small number of internal parameters promotes the SADE
method as the most robust for practical use.
|
0902.1665
|
Novel anisotropic continuum-discrete damage model capable of
representing localized failure of massive structures. Part II: identification
from tests under heterogeneous stress field
|
cs.NE cs.CE
|
In Part I of this paper we have presented a simple model capable of
describing the localized failure of a massive structure. In this part, we
discuss the identification of the model parameters from two kinds of
experiments: a uniaxial tensile test and a three-point bending test. The former
is used only for illustration of material parameter response dependence, and we
focus mostly upon the latter, discussing the inverse optimization problem for
which the specimen is subjected to a heterogeneous stress field.
|
0902.1690
|
Back analysis of microplane model parameters using soft computing
methods
|
cs.NE cs.AI
|
A new procedure based on layered feed-forward neural networks for the
microplane material model parameters identification is proposed in the present
paper. Novelties are usage of the Latin Hypercube Sampling method for the
generation of training sets, a systematic employment of stochastic sensitivity
analysis and a genetic algorithm-based training of a neural network by an
evolutionary algorithm. Advantages and disadvantages of this approach together
with possible extensions are thoroughly discussed and analyzed.
|
0902.1734
|
A New Achievable Rate for the Gaussian Parallel Relay Channel
|
cs.IT math.IT
|
Schein and Gallager introduced the Gaussian parallel relay channel in 2000.
They proposed the Amplify-and-Forward (AF) and the Decode-and-Forward (DF)
strategies for this channel. For a long time, the best known achievable rate
for this channel was based on the AF and DF with time sharing (AF-DF).
Recently, a Rematch-and-Forward (RF) scheme for the scenario in which different
amounts of bandwidth can be assigned to the first and second hops were
proposed.
In this paper, we propose a \emph{Combined Amplify-and-Decode Forward (CADF)}
scheme for the Gaussian parallel relay channel. We prove that the CADF scheme
always gives a better achievable rate compared to the RF scheme, when there is
a bandwidth mismatch between the first hop and the second hop. Furthermore, for
the equal bandwidth case (Schein's setup), we show that the time sharing
between the CADF and the DF schemes (CADF-DF) leads to a better achievable rate
compared to the time sharing between the RF and the DF schemes (RF-DF) as well
as the AF-DF.
|
0902.1786
|
On the Dynamics of the Error Floor Behavior in (Regular) LDPC Codes
|
cs.IT math.IT
|
It is shown that dominant trapping sets of regular LDPC codes, so called
absorption sets, undergo a two-phased dynamic behavior in the iterative
message-passing decoding algorithm. Using a linear dynamic model for the
iteration behavior of these sets, it is shown that they undergo an initial
geometric growth phase which stabilizes in a final bit-flipping behavior where
the algorithm reaches a fixed point. This analysis is shown to lead to very
accurate numerical calculations of the error floor bit error rates down to
error rates that are inaccessible by simulation. The topology of the dominant
absorption sets of an example code, the IEEE 802.3an (2048,1723) regular LDPC
code, are identified and tabulated using topological relationships in
combination with search algorithms.
|
0902.1790
|
Counting Distinctions: On the Conceptual Foundations of Shannon's
Information Theory
|
cs.IT cs.LO math.IT math.LO
|
Categorical logic has shown that modern logic is essentially the logic of
subsets (or "subobjects"). Partitions are dual to subsets so there is a dual
logic of partitions where a "distinction" [an ordered pair of distinct elements
(u,u') from the universe U ] is dual to an "element". An element being in a
subset is analogous to a partition p on U making a distinction, i.e., if u and
u' were in different blocks of p. Subset logic leads to finite probability
theory by taking the (Laplacian) probability as the normalized size of each
subset-event of a finite universe. The analogous step in the logic of
partitions is to assign to a partition the number of distinctions made by a
partition normalized by the total number of ordered pairs |UxU| from the finite
universe. That yields a notion of "logical entropy" for partitions and a
"logical information theory." The logical theory directly counts the
(normalized) number of distinctions in a partition while Shannon's theory gives
the average number of binary partitions needed to make those same distinctions.
Thus the logical theory is seen as providing a conceptual underpinning for
Shannon's theory based on the logical notion of "distinctions." (forthcoming in
Synthese)
|
0902.1834
|
Optimal Probabilistic Ring Exploration by Asynchronous Oblivious Robots
|
cs.DS cs.CC cs.DC cs.RO
|
We consider a team of $k$ identical, oblivious, asynchronous mobile robots
that are able to sense (\emph{i.e.}, view) their environment, yet are unable to
communicate, and evolve on a constrained path. Previous results in this weak
scenario show that initial symmetry yields high lower bounds when problems are
to be solved by \emph{deterministic} robots. In this paper, we initiate
research on probabilistic bounds and solutions in this context, and focus on
the \emph{exploration} problem of anonymous unoriented rings of any size. It is
known that $\Theta(\log n)$ robots are necessary and sufficient to solve the
problem with $k$ deterministic robots, provided that $k$ and $n$ are coprime.
By contrast, we show that \emph{four} identical probabilistic robots are
necessary and sufficient to solve the same problem, also removing the coprime
constraint. Our positive results are constructive.
|
0902.1853
|
A Unified Approach to Sparse Signal Processing
|
cs.IT math.IT
|
A unified view of sparse signal processing is presented in tutorial form by
bringing together various fields. For each of these fields, various algorithms
and techniques, which have been developed to leverage sparsity, are described
succinctly. The common benefits of significant reduction in sampling rate and
processing manipulations are revealed.
The key applications of sparse signal processing are sampling, coding,
spectral estimation, array processing, component analysis, and multipath
channel estimation. In terms of reconstruction algorithms, linkages are made
with random sampling, compressed sensing and rate of innovation. The redundancy
introduced by channel coding in finite/real Galois fields is then related to
sampling with similar reconstruction algorithms. The methods of Prony,
Pisarenko, and MUSIC are next discussed for sparse frequency domain
representations. Specifically, the relations of the approach of Prony to an
annihilating filter and Error Locator Polynomials in coding are emphasized; the
Pisarenko and MUSIC methods are further improvements of the Prony method. Such
spectral estimation methods is then related to multi-source location and DOA
estimation in array processing. The notions of sparse array beamforming and
sparse sensor networks are also introduced. Sparsity in unobservable source
signals is also shown to facilitate source separation in SCA; the algorithms
developed in this area are also widely used in compressed sensing. Finally, the
multipath channel estimation problem is shown to have a sparse formulation;
algorithms similar to sampling and coding are used to estimate OFDM channels.
|
0902.1911
|
Topological Centrality and Its Applications
|
cs.IR cs.AI
|
Recent development of network structure analysis shows that it plays an
important role in characterizing complex system of many branches of sciences.
Different from previous network centrality measures, this paper proposes the
notion of topological centrality (TC) reflecting the topological positions of
nodes and edges in general networks, and proposes an approach to calculating
the topological centrality. The proposed topological centrality is then used to
discover communities and build the backbone network. Experiments and
applications on research network show the significance of the proposed
approach.
|
0902.1942
|
On the Classification of Type II Codes of Length 24
|
math.NT cs.DM cs.IT math.CO math.IT
|
We give a new, purely coding-theoretic proof of Koch's criterion on the
tetrad systems of Type II codes of length 24 using the theory of harmonic
weight enumerators. This approach is inspired by Venkov's approach to the
classification of the root systems of Type II lattices in R^{24}, and gives a
new instance of the analogy between lattices and codes.
|
0902.1947
|
Cooperative Spectrum Sensing based on the Limiting Eigenvalue Ratio
Distribution in Wishart Matrices
|
cs.IT math.IT
|
Recent advances in random matrix theory have spurred the adoption of
eigenvalue-based detection techniques for cooperative spectrum sensing in
cognitive radio. Most of such techniques use the ratio between the largest and
the smallest eigenvalues of the received signal covariance matrix to infer the
presence or absence of the primary signal. The results derived so far in this
field are based on asymptotical assumptions, due to the difficulties in
characterizing the exact distribution of the eigenvalues ratio. By exploiting a
recent result on the limiting distribution of the smallest eigenvalue in
complex Wishart matrices, in this paper we derive an expression for the
limiting eigenvalue ratio distribution, which turns out to be much more
accurate than the previous approximations also in the non-asymptotical region.
This result is then straightforwardly applied to calculate the decision
threshold as a function of a target probability of false alarm. Numerical
simulations show that the proposed detection rule provides a substantial
performance improvement compared to the other eigenvalue-based algorithms.
|
0902.1996
|
Convergence and Tradeoff of Utility-Optimal CSMA
|
cs.IT math.IT
|
It has been recently suggested that in wireless networks, CSMA-based
distributed MAC algorithms could achieve optimal utility without any message
passing. We present the first proof of convergence of such adaptive CSMA
algorithms towards an arbitrarily tight approximation of utility-optimizing
schedule. We also briefly discuss the tradeoff between optimality at
equilibrium and short-term fairness practically achieved by such algorithms.
|
0902.2036
|
Modified Papoulis-Gerchberg algorithm for sparse signal recovery
|
cs.IT math.IT
|
Motivated by the well-known Papoulis-Gerchberg algorithm, an iterative
thresholding algorithm for recovery of sparse signals from few observations is
proposed. The sequence of iterates turns out to be similar to that of the
thresholded Landweber iterations, although not the same. The performance of the
proposed algorithm is experimentally evaluated and compared to other
state-of-the-art methods.
|
0902.2104
|
Tableau-based decision procedure for full coalitional multiagent
temporal-epistemic logic of linear time
|
cs.LO cs.MA
|
We develop a tableau-based decision procedure for the full coalitional
multiagent temporal-epistemic logic of linear time CMATEL(CD+LT). It extends
LTL with operators of common and distributed knowledge for all coalitions of
agents. The tableau procedure runs in exponential time, matching the lower
bound obtained by Halpern and Vardi for a fragment of our logic, thus providing
a complexity-optimal decision procedure for CMATEL(CD+LT).
|
0902.2125
|
Tableau-based procedure for deciding satisfiability in the full
coalitional multiagent epistemic logic
|
cs.LO cs.MA
|
We study the multiagent epistemic logic CMAELCD with operators for common and
distributed knowledge for all coalitions of agents. We introduce Hintikka
structures for this logic and prove that satisfiability in such structures is
equivalent to satisfiability in standard models. Using this result, we design
an incremental tableau based decision procedure for testing satisfiability in
CMAELCD.
|
0902.2141
|
Extracting the Kolmogorov Complexity of Strings and Sequences from
Sources with Limited Independence
|
cs.CC cs.IT math.IT
|
An infinite binary sequence has randomness rate at least $\sigma$ if, for
almost every $n$, the Kolmogorov complexity of its prefix of length $n$ is at
least $\sigma n$. It is known that for every rational $\sigma \in (0,1)$, on
one hand, there exists sequences with randomness rate $\sigma$ that can not be
effectively transformed into a sequence with randomness rate higher than
$\sigma$ and, on the other hand, any two independent sequences with randomness
rate $\sigma$ can be transformed into a sequence with randomness rate higher
than $\sigma$. We show that the latter result holds even if the two input
sequences have linear dependency (which, informally speaking, means that all
prefixes of length $n$ of the two sequences have in common a constant fraction
of their information). The similar problem is studied for finite strings. It is
shown that from any two strings with sufficiently large Kolmogorov complexity
and sufficiently small dependence, one can effectively construct a string that
is random even conditioned by any one of the input strings.
|
0902.2186
|
A List of Household Objects for Robotic Retrieval Prioritized by People
with ALS (Version 092008)
|
cs.RO cs.HC
|
This technical report is designed to serve as a citable reference for the
original prioritized object list that the Healthcare Robotics Lab at Georgia
Tech released on its website in September of 2008. It is also expected to serve
as the primary citable reference for the research associated with this list
until the publication of a detailed, peer-reviewed paper.
The original prioritized list of object classes resulted from a needs
assessment involving 8 motor-impaired patients with amyotrophic lateral
sclerosis (ALS) and targeted, in-person interviews of 15 motor-impaired ALS
patients. All of these participants were drawn from the Emory ALS Center.
The prioritized object list consists of 43 object classes ranked by how
important the participants considered each class to be for retrieval by an
assistive robot. We intend for this list to be used by researchers to inform
the design and benchmarking of robotic systems, especially research related to
autonomous mobile manipulation.
|
0902.2187
|
A Standalone Markerless 3D Tracker for Handheld Augmented Reality
|
cs.CV cs.GR cs.MM
|
This paper presents an implementation of a markerless tracking technique
targeted to the Windows Mobile Pocket PC platform. The primary aim of this work
is to allow the development of standalone augmented reality applications for
handheld devices based on natural feature tracking. In order to achieve this
goal, a subset of two computer vision libraries was ported to the Pocket PC
platform. They were also adapted to use fixed point math, with the purpose of
improving the overall performance of the routines. The port of these libraries
opens up the possibility of having other computer vision tasks being executed
on mobile platforms. A model based tracking approach that relies on edge
information was adopted. Since it does not require a high processing power, it
is suitable for constrained devices such as handhelds. The OpenGL ES graphics
library was used to perform computer vision tasks, taking advantage of existing
graphics hardware acceleration. An augmented reality application was created
using the implemented technique and evaluations were done regarding tracking
performance and accuracy
|
0902.2206
|
Feature Hashing for Large Scale Multitask Learning
|
cs.AI
|
Empirical evidence suggests that hashing is an effective strategy for
dimensionality reduction and practical nonparametric estimation. In this paper
we provide exponential tail bounds for feature hashing and show that the
interaction between random subspaces is negligible with high probability. We
demonstrate the feasibility of this approach with experimental results for a
new use case -- multitask learning with hundreds of thousands of tasks.
|
0902.2230
|
BagPack: A general framework to represent semantic relations
|
cs.CL cs.IR
|
We introduce a way to represent word pairs instantiating arbitrary semantic
relations that keeps track of the contexts in which the words in the pair occur
both together and independently. The resulting features are of sufficient
generality to allow us, with the help of a standard supervised machine learning
algorithm, to tackle a variety of unrelated semantic tasks with good results
and almost no task-specific tailoring.
|
0902.2235
|
On Isometries for Convolutional Codes
|
cs.IT math.IT
|
In this paper we will discuss isometries and strong isometries for
convolutional codes. Isometries are weight-preserving module isomorphisms
whereas strong isometries are, in addition, degree-preserving. Special cases of
these maps are certain types of monomial transformations. We will show a form
of MacWilliams Equivalence Theorem, that is, each isometry between
convolutional codes is given by a monomial transformation. Examples show that
strong isometries cannot be characterized this way, but special attention paid
to the weight adjacency matrices allows for further descriptions. Various
distance parameters appearing in the literature on convolutional codes will be
discussed as well.
|
0902.2260
|
Network Coding with Two-Way Relaying: Achievable Rate Regions and
Diversity-Multiplexing Tradeoffs
|
cs.IT math.IT
|
This paper addresses the fundamental characteristics of information exchange
via multihop network coding over two-way relaying in a wireless ad hoc network.
The end-to-end rate regions achieved by time-division multihop (TDMH),
MAC-layer network coding (MLNC) and PHY-layer network coding (PLNC) are first
characterized. It is shown that MLNC does not always achieve better rates than
TDMH, time sharing between TDMH and MLNC is able to achieve a larger rate
region, and PLNC dominates the rate regions achieved by TDMH and MLNC. An
opportunistic scheduling algorithm for MLNC and PLNC is then proposed to
stabilize the two-way relaying system for Poisson arrivals whenever the rate
pair is within the Shannon rate regions of MLNC and PLNC. To understand the
two-way transmission limits of multihop network coding, the sum-rate
optimization with or without certain traffic pattern and the end-to-end
diversity-multiplexing tradeoffs (DMTs) of two-way transmission over multiple
relay nodes are also analyzed.
|
0902.2316
|
On weak isometries of Preparata codes
|
cs.IT math.IT
|
Let C1 and C2 be codes with code distance d. Codes C1 and C2 are called
weakly isometric, if there exists a mapping J:C1->C2, such that for any x,y
from C1 the equality d(x,y)=d holds if and only if d(J(x),J(y))=d. Obviously
two codes are weakly isometric if and only if the minimal distance graphs of
these codes are isomorphic. In this paper we prove that Preparata codes of
length n>=2^12 are weakly isometric if and only if these codes are equivalent.
The analogous result is obtained for punctured Preparata codes of length not
less than 2^10-1.
|
0902.2345
|
What's in a Message?
|
cs.CL
|
In this paper we present the first step in a larger series of experiments for
the induction of predicate/argument structures. The structures that we are
inducing are very similar to the conceptual structures that are used in Frame
Semantics (such as FrameNet). Those structures are called messages and they
were previously used in the context of a multi-document summarization system of
evolving events. The series of experiments that we are proposing are
essentially composed from two stages. In the first stage we are trying to
extract a representative vocabulary of words. This vocabulary is later used in
the second stage, during which we apply to it various clustering approaches in
order to identify the clusters of predicates and arguments--or frames and
semantic roles, to use the jargon of Frame Semantics. This paper presents in
detail and evaluates the first stage.
|
0902.2362
|
XML Representation of Constraint Networks: Format XCSP 2.1
|
cs.AI
|
We propose a new extended format to represent constraint networks using XML.
This format allows us to represent constraints defined either in extension or
in intension. It also allows us to reference global constraints. Any instance
of the problems CSP (Constraint Satisfaction Problem), QCSP (Quantified CSP)
and WCSP (Weighted CSP) can be represented using this format.
|
0902.2367
|
Dequantizing Compressed Sensing: When Oversampling and Non-Gaussian
Constraints Combine
|
math.OC cs.IT math.IT
|
In this paper we study the problem of recovering sparse or compressible
signals from uniformly quantized measurements. We present a new class of convex
optimization programs, or decoders, coined Basis Pursuit DeQuantizer of moment
$p$ (BPDQ$_p$), that model the quantization distortion more faithfully than the
commonly used Basis Pursuit DeNoise (BPDN) program. Our decoders proceed by
minimizing the sparsity of the signal to be reconstructed subject to a
data-fidelity constraint expressed in the $\ell_p$-norm of the residual error
for $2\leq p\leq \infty$.
We show theoretically that, (i) the reconstruction error of these new
decoders is bounded if the sensing matrix satisfies an extended Restricted
Isometry Property involving the $\ell_p$ norm, and (ii), for Gaussian random
matrices and uniformly quantized measurements, BPDQ$_p$ performance exceeds
that of BPDN by dividing the reconstruction error due to quantization by
$\sqrt{p+1}$. This last effect happens with high probability when the number of
measurements exceeds a value growing with $p$, i.e. in an oversampled situation
compared to what is commonly required by BPDN = BPDQ$_2$. To demonstrate the
theoretical power of BPDQ$_p$, we report numerical simulations on signal and
image reconstruction problems.
|
0902.2370
|
Outer Bounds on the Admissible Source Region for Broadcast Channels with
Dependent Sources
|
cs.IT math.IT
|
Outer bounds on the admissible source region for broadcast channels with
dependent sources are developed and used to prove capacity results for several
classes of sources and channels.
|
0902.2399
|
A Multi-Round Communication Lower Bound for Gap Hamming and Some
Consequences
|
cs.CC cs.DB cs.DS
|
The Gap-Hamming-Distance problem arose in the context of proving space lower
bounds for a number of key problems in the data stream model. In this problem,
Alice and Bob have to decide whether the Hamming distance between their $n$-bit
input strings is large (i.e., at least $n/2 + \sqrt n$) or small (i.e., at most
$n/2 - \sqrt n$); they do not care if it is neither large nor small. This
$\Theta(\sqrt n)$ gap in the problem specification is crucial for capturing the
approximation allowed to a data stream algorithm.
Thus far, for randomized communication, an $\Omega(n)$ lower bound on this
problem was known only in the one-way setting. We prove an $\Omega(n)$ lower
bound for randomized protocols that use any constant number of rounds.
As a consequence we conclude, for instance, that $\epsilon$-approximately
counting the number of distinct elements in a data stream requires
$\Omega(1/\epsilon^2)$ space, even with multiple (a constant number of) passes
over the input stream. This extends earlier one-pass lower bounds, answering a
long-standing open question. We obtain similar results for approximating the
frequency moments and for approximating the empirical entropy of a data stream.
In the process, we also obtain tight $n - \Theta(\sqrt{n}\log n)$ lower and
upper bounds on the one-way deterministic communication complexity of the
problem. Finally, we give a simple combinatorial proof of an $\Omega(n)$ lower
bound on the one-way randomized communication complexity.
|
0902.2420
|
Self-Assembly as Graph Grammar as Distributed System
|
cs.DC cs.NE
|
In 2004, Klavins et al. introduced the use of graph grammars to describe --
and to program -- systems of self-assembly. It turns out that these graph
grammars are a "dual notion" of a graph rewriting characterization of
distributed systems that was proposed by Degano and Montanari over twenty years
ago. By applying techniques obtained from this observation, we prove a
generalized version of Soloveichik and Winfree's theorem on local determinism,
and we also present a canonical method to simulate asynchronous
constant-size-message-passing models of distributed computing with systems of
self-assembly.
|
0902.2425
|
Finding Community Structure Based on Subgraph Similarity
|
cs.NI cs.IR physics.soc-ph
|
Community identification is a long-standing challenge in the modern network
science, especially for very large scale networks containing millions of nodes.
In this paper, we propose a new metric to quantify the structural similarity
between subgraphs, based on which an algorithm for community identification is
designed. Extensive empirical results on several real networks from disparate
fields has demonstrated that the present algorithm can provide the same level
of reliability, measure by modularity, while takes much shorter time than the
well-known fast algorithm proposed by Clauset, Newman and Moore (CNM). We
further propose a hybrid algorithm that can simultaneously enhance modularity
and save computational time compared with the CNM algorithm.
|
0902.2436
|
Nested Lattice Codes for Gaussian Relay Networks with Interference
|
cs.IT math.IT
|
In this paper, a class of relay networks is considered. We assume that, at a
node, outgoing channels to its neighbors are orthogonal, while incoming signals
from neighbors can interfere with each other. We are interested in the
multicast capacity of these networks. As a subclass, we first focus on Gaussian
relay networks with interference and find an achievable rate using a lattice
coding scheme. It is shown that there is a constant gap between our achievable
rate and the information theoretic cut-set bound. This is similar to the recent
result by Avestimehr, Diggavi, and Tse, who showed such an approximate
characterization of the capacity of general Gaussian relay networks. However,
our achievability uses a structured code instead of a random one. Using the
same idea used in the Gaussian case, we also consider linear finite-field
symmetric networks with interference and characterize the capacity using a
linear coding scheme.
|
0902.2438
|
Capacity of the Gaussian Two-way Relay Channel to within 1/2 Bit
|
cs.IT math.IT
|
In this paper, a Gaussian two-way relay channel, where two source nodes
exchange messages with each other through a relay, is considered. We assume
that all nodes operate in full-duplex mode and there is no direct channel
between the source nodes. We propose an achievable scheme composed of nested
lattice codes for the uplink and structured binning for the downlink. We show
that the scheme achieves within 1/2 bit from the cut-set bound for all channel
parameters and becomes asymptotically optimal as the signal to noise ratios
increase.
|
0902.2446
|
Detection of Gaussian signals via hexagonal sensor networks
|
math.OC cs.SY
|
This paper considers a special case of the problem of identifying a static
scalar signal, depending on the location, using a planar network of sensors in
a distributed fashion. Motivated by the application to monitoring wild-fires
spreading and pollutants dispersion, we assume the signal to be Gaussian in
space. Using a network of sensors positioned to form a regular hexagonal
tessellation, we prove that each node can estimate the parameters of the
Gaussian from local measurements. Moreover, we study the sensitivity of these
estimates to additive errors affecting the measurements. Finally, we show how a
consensus algorithm can be designed to fuse the local estimates into a shared
global estimate, effectively compensating the measurement errors.
|
0902.2504
|
Hyperset Approach to Semi-structured Databases and the Experimental
Implementation of the Query Language Delta
|
cs.DB
|
This thesis presents practical suggestions towards the implementation of the
hyperset approach to semi-structured databases and the associated query
language Delta. This work can be characterised as part of a top-down approach
to semi-structured databases, from theory to practice. The main original part
of this work consisted in implementation of the hyperset Delta query language
to semi-structured databases, including worked example queries. In fact, the
goal was to demonstrate the practical details of this approach and language.
The required development of an extended, practical version of the language
based on the existing theoretical version, and the corresponding operational
semantics. Here we present detailed description of the most essential steps of
the implementation. Another crucial problem for this approach was to
demonstrate how to deal in reality with the concept of the equality relation
between (hyper)sets, which is computationally realised by the bisimulation
relation. In fact, this expensive procedure, especially in the case of
distributed semi-structured data, required some additional theoretical
considerations and practical suggestions for efficient implementation. To this
end the 'local/global' strategy for computing the bisimulation relation over
distributed semi-structured data was developed and its efficiency was
experimentally confirmed.
|
0902.2559
|
Power Allocation Games for MIMO Multiple Access Channels with
Coordination
|
cs.IT math.IT
|
A game theoretic approach is used to derive the optimal decentralized power
allocation (PA) in fast fading multiple access channels where the transmitters
and receiver are equipped with multiple antennas. The players (the mobile
terminals) are free to choose their PA in order to maximize their individual
transmission rates (in particular they can ignore some specified centralized
policies). A simple coordination mechanism between users is introduced. The
nature and influence of this mechanism is studied in detail. The coordination
signal indicates to the users the order in which the receiver applies
successive interference cancellation and the frequency at which this order is
used. Two different games are investigated: the users can either adapt their
temporal PA to their decoding rank at the receiver or optimize their spatial PA
between their transmit antennas. For both games a thorough analysis of the
existence, uniqueness and sum-rate efficiency of the network Nash equilibrium
is conducted. Analytical and simulation results are provided to assess the gap
between the decentralized network performance and its equivalent virtual
multiple input multiple output system, which is shown to be zero in some cases
and relatively small in general.
|
0902.2692
|
Combining coded signals with arbitrary modulations in orthogonal relay
channels
|
cs.IT math.IT
|
We consider a relay channel for which the following assumptions are made. (1)
The source-destination and relay-destination channels are orthogonal (frequency
division relay channel). (2) The relay implements the decode-and-forward
protocol. (3) The source and relay implement the same channel encoder, namely,
a onvolutional encoder. (4) They can use arbitrary and possibly different
modulations. In this framework, we derive the best combiner in the sense of the
maximum likelihood (ML) at the destination and the branch metrics of the
trellis associated with its channel decoder for the ML combiner and also for
the maximum ratio combiner (MRC), cooperative-MRC (C-MRC), and the minimum
mean-square error (MMSE) combiner.
|
0902.2751
|
Object Classification by means of Multi-Feature Concept Learning in a
Multi Expert-Agent System
|
cs.MA cs.LG
|
Classification of some objects in classes of concepts is an essential and
even breathtaking task in many applications. A solution is discussed here based
on Multi-Agent systems. A kernel of some expert agents in several classes is to
consult a central agent decide among the classification problem of a certain
object. This kernel is moderated with the center agent, trying to manage the
querying agents for any decision problem by means of a data-header like feature
set. Agents have cooperation among concepts related to the classes of this
classification decision-making; and may affect on each others' results on a
certain query object in a multi-agent learning approach. This leads to an
online feature learning via the consulting trend. The performance is discussed
to be much better in comparison to some other prior trends while system's
message passing overload is decreased to less agents and the expertism helps
the performance and operability of system win the comparison.
|
0902.2788
|
Using SLP Neural Network to Persian Handwritten Digits Recognition
|
cs.CV
|
This paper has been withdrawn by the author ali pourmohammad.
|
0902.2851
|
Leader Election Problem Versus Pattern Formation Problem
|
cs.DC cs.MA
|
Leader election and arbitrary pattern formation are funda- mental tasks for a
set of autonomous mobile robots. The former consists in distinguishing a unique
robot, called the leader. The latter aims in arranging the robots in the plane
to form any given pattern. The solv- ability of both these tasks turns out to
be necessary in order to achieve more complex tasks. In this paper, we study
the relationship between these two tasks in a model, called CORDA, wherein the
robots are weak in several aspects. In particular, they are fully asynchronous
and they have no direct means of communication. They cannot remember any
previous observation nor computation performed in any previous step. Such
robots are said to be oblivious. The robots are also uniform and anonymous,
i.e, they all have the same program using no global parameter (such as an
identity) allowing to differentiate any of them. Moreover, we assume that none
of them share any kind of common coordinate mechanism or common sense of
direction and we discuss the influence of a common handedness (i.e.,
chirality). In such a system, Flochini et al. proved in [11] that it is
possible to elect a leader for n \geq 3 robots if it is possible to form any
pattern for n \geq 3. In this paper, we show that the converse is true for n
\geq 4 when the robots share a common handedness and for n \geq 5 when they do
not. Thus, we deduce that with chirality (resp. without chirality) both
problems are equivalent for n \geq 4 (resp. n \geq 5) in CORDA.
|
0902.2871
|
The Semantics of Kalah Game
|
cs.AI
|
The present work consisted in developing a plateau game. There are the
traditional ones (monopoly, cluedo, ect.) but those which interest us leave
less place at the chance (luck) than to the strategy such that the chess game.
Kallah is an old African game, its rules are simple but the strategies to be
used are very complex to implement. Of course, they are based on a strongly
mathematical basis as in the film "Rain-Man" where one can see that gambling
can be payed with strategies based on mathematical theories. The Artificial
Intelligence gives the possibility "of thinking" to a machine and, therefore,
allows it to make decisions. In our work, we use it to give the means to the
computer choosing its best movement.
|
0902.2917
|
Full Rate L2-Orthogonal Space-Time CPM for Three Antennas
|
cs.IT math.IT
|
To combine the power efficiency of Continuous Phase Modulation (CPM) with
enhanced performance in fading environments, some authors have suggested to use
CPM in combination with Space-Time Codes (STC). Recently, we have proposed a
CPM ST-coding scheme based on L2-orthogonality for two transmitting antennas.
In this paper we extend this approach to the three antennas case. We
analytically derive a family of coding schemes which we call Parallel Code
(PC). This code family has full rate and we prove that the proposed coding
scheme achieves full diversity as confirmed by accompanying simulations. We
detail an example of the proposed ST codes that can be interpreted as a
conventional CPM scheme with different alphabet sets for the different transmit
antennas which results in a simplified implementation. Thanks to
L2-orthogonality, the decoding complexity, usually exponentially proportional
to the number of transmitting antennas, is reduced to linear complexity.
|
0902.2948
|
Optimized L2-Orthogonal STC CPM for 3 Antennas
|
cs.IT math.IT
|
In this paper, we introduce further our recently designed family of L2
orthogonal Space-Time codes for CPM. With their advantage of maintaining both
the constant envelope properties of CPM, the diversity of Space-Time codes and
moreover orthogonality, and thus reduced decoding complexity, these codes are
also full rate, even for more than two transmitting antennas. The issue of
power efficiency for these codes is first dealt with by proving that the
inherent increase in bandwidth in these systems is quite moderate. It is then
detailed how the initial state of the code influences the coding gain and has
to be optimized. For the two and three antennas case, we determine the optimal
values by computer simulations and show how the coding gain and therewith the
bit error performance are significantly improved by this optimization.
|
0902.2953
|
ImageSpace: An Environment for Image Ontology Management
|
cs.DL cs.DB cs.MM cs.SE
|
More and more researchers have realized that ontologies will play a critical
role in the development of the Semantic Web, the next generation Web in which
content is not only consumable by humans, but also by software agents. The
development of tools to support ontology management including creation,
visualization, annotation, database storage, and retrieval is thus extremely
important. We have developed ImageSpace, an image ontology creation and
annotation tool that features (1) full support for the standard web ontology
language DAML+OIL; (2) image ontology creation, visualization, image annotation
and display in one integrated framework; (3) ontology consistency assurance;
and (4) storing ontologies and annotations in relational databases. It is
expected that the availability of such a tool will greatly facilitate the
creation of image repositories as islands of the Semantic Web.
|
0902.2969
|
Ptarithmetic
|
cs.LO cs.AI cs.CC
|
The present article introduces ptarithmetic (short for "polynomial time
arithmetic") -- a formal number theory similar to the well known Peano
arithmetic, but based on the recently born computability logic (see
http://www.cis.upenn.edu/~giorgi/cl.html) instead of classical logic. The
formulas of ptarithmetic represent interactive computational problems rather
than just true/false statements, and their "truth" is understood as existence
of a polynomial time solution. The system of ptarithmetic elaborated in this
article is shown to be sound and complete. Sound in the sense that every
theorem T of the system represents an interactive number-theoretic
computational problem with a polynomial time solution and, furthermore, such a
solution can be effectively extracted from a proof of T. And complete in the
sense that every interactive number-theoretic problem with a polynomial time
solution is represented by some theorem T of the system.
The paper is self-contained, and can be read without any previous familiarity
with computability logic.
|
0902.2975
|
Writing Positive/Negative-Conditional Equations Conveniently
|
cs.AI cs.LO
|
We present a convenient notation for positive/negative-conditional equations.
The idea is to merge rules specifying the same function by using case-, if-,
match-, and let-expressions. Based on the presented macro-rule-construct,
positive/negative-conditional equational specifications can be written on a
higher level. A rewrite system translates the macro-rule-constructs into
positive/negative-conditional equations.
|
0902.2995
|
ASF+ --- eine ASF-aehnliche Spezifikationssprache
|
cs.AI cs.SC
|
Maintaining the main aspects of the algebraic specification language ASF as
presented in [Bergstra&al.89] we have extend ASF with the following concepts:
While once exported names in ASF must stay visible up to the top the module
hierarchy, ASF+ permits a more sophisticated hiding of signature names. The
erroneous merging of distinct structures that occurs when importing different
actualizations of the same parameterized module in ASF is avoided in ASF+ by a
more adequate form of parameter binding. The new ``Namensraum''-concept of ASF+
permits the specifier on the one hand directly to identify the origin of hidden
names and on the other to decide whether an imported module is only to be
accessed or whether an important property of it is to be modified. In the first
case he can access one single globally provided version; in the second he has
to import a copy of the module. Finally ASF+ permits semantic conditions on
parameters and the specification of tasks for a theorem prover.
|
0902.3026
|
OntoELAN: An Ontology-based Linguistic Multimedia Annotator
|
cs.DL cs.DB cs.MM cs.SE
|
Despite its scientific, political, and practical value, comprehensive
information about human languages, in all their variety and complexity, is not
readily obtainable and searchable. One reason is that many language data are
collected as audio and video recordings which imposes a challenge to document
indexing and retrieval. Annotation of multimedia data provides an opportunity
for making the semantics explicit and facilitates the searching of multimedia
documents. We have developed OntoELAN, an ontology-based linguistic multimedia
annotator that features: (1) support for loading and displaying ontologies
specified in OWL; (2) creation of a language profile, which allows a user to
choose a subset of terms from an ontology and conveniently rename them if
needed; (3) creation of ontological tiers, which can be annotated with profile
terms and, therefore, corresponding ontological terms; and (4) saving
annotations in the XML format as Multimedia Ontology class instances and,
linked to them, class instances of other ontologies used in ontological tiers.
To our best knowledge, OntoELAN is the first audio/video annotation tool in
linguistic domain that provides support for ontology-based annotation.
|
0902.3027
|
Ontology-Based Annotation of Multimedia Language Data for the Semantic
Web
|
cs.DL cs.DB cs.MM
|
There is an increasing interest and effort in preserving and documenting
endangered languages. Language data are valuable only when they are
well-cataloged, indexed and searchable. Many language data, particularly those
of lesser-spoken languages, are collected as audio and video recordings. While
multimedia data provide more channels and dimensions to describe a language's
function, and gives a better presentation of the cultural system associated
with the language of that community, they are not text-based or structured (in
binary format), and their semantics is implicit in their content. The content
is thus easy for a human being to understand, but difficult for computers to
interpret. Hence, there is a great need for a powerful and user-friendly system
to annotate multimedia data with text-based, well-structured and searchable
metadata. This chapter describes an ontology-based multimedia annotation tool,
OntoELAN, that enables annotation of language multimedia data with a linguistic
ontology.
|
0902.3056
|
New Results in the Simultaneous Message Passing Model
|
cs.DC cs.CC cs.IT math.IT quant-ph
|
Consider the following Simultaneous Message Passing (SMP) model for computing
a relation f subset of X x Y x Z. In this model Alice, on input x in X and Bob,
on input y in Y, send one message each to a third party Referee who then
outputs a z in Z such that (x,y,z) in f. We first show optimal 'Direct sum'
results for all relations f in this model, both in the quantum and classical
settings, in the situation where we allow shared resources (shared entanglement
in quantum protocols and public coins in classical protocols) between Alice and
Referee and Bob and Referee and no shared resource between Alice and Bob. This
implies that, in this model, the communication required to compute k
simultaneous instances of f, with constant success overall, is at least k-times
the communication required to compute one instance with constant success.
This in particular implies an earlier Direct sum result, shown by
Chakrabarti, Shi, Wirth and Yao, 2001, for the Equality function (and a class
of other so-called robust functions), in the classical smp model with no shared
resources between any parties.
Furthermore we investigate the gap between the smp model and the one-way
model in communication complexity and exhibit a partial function that is
exponentially more expensive in the former if quantum communication with
entanglement is allowed, compared to the latter even in the deterministic case.
|
0902.3072
|
Syntactic variation of support verb constructions
|
cs.CL
|
We report experiments about the syntactic variations of support verb
constructions, a special type of multiword expressions (MWEs) containing
predicative nouns. In these expressions, the noun can occur with or without the
verb, with no clear-cut semantic difference. We extracted from a large French
corpus a set of examples of the two situations and derived statistical results
from these data. The extraction involved large-coverage language resources and
finite-state techniques. The results show that, most frequently, predicative
nouns occur without a support verb. This fact has consequences on methods of
extracting or recognising MWEs.
|
0902.3076
|
Coding for the Non-Orthogonal Amplify-and-Forward Cooperative Channel
|
cs.IT math.IT
|
In this work, we consider the problem of coding for the half-duplex
non-orthogonal amplify-and-forward (NAF) cooperative channel where the
transmitter to relay and the inter-relay links are highly reliable. We derive
bounds on the diversity order of the NAF protocol that are achieved by a
distributed space-time bit-interleaved coded modulation (D-ST-BICM) scheme
under iterative APP detection and decoding. These bounds lead to the design of
space-time precoders that ensure maximum diversity order and high coding gains.
The word error rate performance of D-ST-BICM are also compared to outage
probability limits.
|
0902.3114
|
Analysis of the Second Moment of the LT Decoder
|
cs.IT math.IT
|
We analyze the second moment of the ripple size during the LT decoding
process and prove that the standard deviation of the ripple size for an LT-code
with length $k$ is of the order of $\sqrt k.$ Together with a result by Karp
et. al stating that the expectation of the ripple size is of the order of $k$
[3], this gives bounds on the error probability of the LT decoder. We also give
an analytic expression for the variance of the ripple size up to terms of
constant order, and refine the expression in [3] for the expectation of the
ripple size up to terms of the order of $1/k$, thus providing a first step
towards an analytic finite-length analysis of LT decoding.
|
0902.3176
|
Error-Correcting Tournaments
|
cs.AI cs.LG
|
We present a family of pairwise tournaments reducing $k$-class classification
to binary classification. These reductions are provably robust against a
constant fraction of binary errors. The results improve on the PECOC
construction \cite{SECOC} with an exponential improvement in computation, from
$O(k)$ to $O(\log_2 k)$, and the removal of a square root in the regret
dependence, matching the best possible computation and regret up to a constant.
|
0902.3178
|
Multiple Multicasts with the Help of a Relay
|
cs.IT math.IT
|
The problem of simultaneous multicasting of multiple messages with the help
of a relay terminal is considered. In particular, a model is studied in which a
relay station simultaneously assists two transmitters in multicasting their
independent messages to two receivers. The relay may also have an independent
message of its own to multicast. As a first step to address this general model,
referred to as the compound multiple access channel with a relay (cMACr), the
capacity region of the multiple access channel with a "cognitive" relay is
characterized, including the cases of partial and rate-limited cognition. Then,
achievable rate regions for the cMACr model are presented based on
decode-and-forward (DF) and compress-and-forward (CF) relaying strategies.
Moreover, an outer bound is derived for the special case, called the cMACr
without cross-reception, in which each transmitter has a direct link to one of
the receivers while the connection to the other receiver is enabled only
through the relay terminal. The capacity region is characterized for a binary
modulo additive cMACr without cross-reception, showing the optimality of binary
linear block codes, thus highlighting the benefits of physical layer network
coding and structured codes. Results are extended to the Gaussian channel model
as well, providing achievable rate regions for DF and CF, as well as for a
structured code design based on lattice codes. It is shown that the performance
with lattice codes approaches the upper bound for increasing power, surpassing
the rates achieved by the considered random coding-based techniques.
|
0902.3196
|
Symbolic Computing with Incremental Mindmaps to Manage and Mine Data
Streams - Some Applications
|
cs.NE cs.AI
|
In our understanding, a mind-map is an adaptive engine that basically works
incrementally on the fundament of existing transactional streams. Generally,
mind-maps consist of symbolic cells that are connected with each other and that
become either stronger or weaker depending on the transactional stream. Based
on the underlying biologic principle, these symbolic cells and their
connections as well may adaptively survive or die, forming different cell
agglomerates of arbitrary size. In this work, we intend to prove mind-maps'
eligibility following diverse application scenarios, for example being an
underlying management system to represent normal and abnormal traffic behaviour
in computer networks, supporting the detection of the user behaviour within
search engines, or being a hidden communication layer for natural language
interaction.
|
0902.3210
|
Coverage in Multi-Antenna Two-Tier Networks
|
cs.NI cs.IT math.IT
|
In two-tier networks -- comprising a conventional cellular network overlaid
with shorter range hotspots (e.g. femtocells, distributed antennas, or wired
relays) -- with universal frequency reuse, the near-far effect from cross-tier
interference creates dead spots where reliable coverage cannot be guaranteed to
users in either tier. Equipping the macrocell and femtocells with multiple
antennas enhances robustness against the near-far problem. This work derives
the maximum number of simultaneously transmitting multiple antenna femtocells
meeting a per-tier outage probability constraint. Coverage dead zones are
presented wherein cross-tier interference bottlenecks cellular and hotspot
coverage. Two operating regimes are shown namely 1) a cellular-limited regime
in which femtocell users experience unacceptable cross-tier interference and 2)
a hotspot-limited regime wherein both femtocell users and cellular users are
limited by hotspot interference. Our analysis accounts for the per-tier
transmit powers, the number of transmit antennas (single antenna transmission
being a special case) and terrestrial propagation such as the Rayleigh fading
and the path loss exponents. Single-user (SU) multiple antenna transmission at
each tier is shown to provide significantly superior coverage and spatial reuse
relative to multiuser (MU) transmission. We propose a decentralized
carrier-sensing approach to regulate femtocell transmission powers based on
their location. Considering a worst-case cell-edge location, simulations using
typical path loss scenarios show that our interference management strategy
provides reliable cellular coverage with about 60 femtocells per cellsite.
|
0902.3223
|
An Exact Algorithm for the Stratification Problem with Proportional
Allocation
|
cs.LG cs.DM cs.DS
|
We report a new optimal resolution for the statistical stratification problem
under proportional sampling allocation among strata. Consider a finite
population of N units, a random sample of n units selected from this population
and a number L of strata. Thus, we have to define which units belong to each
stratum so as to minimize the variance of a total estimator for one desired
variable of interest in each stratum,and consequently reduce the overall
variance for such quantity. In order to solve this problem, an exact algorithm
based on the concept of minimal path in a graph is proposed and assessed.
Computational results using real data from IBGE (Brazilian Central Statistical
Office) are provided.
|
0902.3286
|
MDS codes on the erasure-erasure wiretap channel
|
cs.IT math.IT
|
This paper considers the problem of perfectly secure communication on a
modified version of Wyner's wiretap channel II where both the main and
wiretapper's channels have some erasures. A secret message is to be encoded
into $n$ channel symbols and transmitted. The main channel is such that the
legitimate receiver receives the transmitted codeword with exactly $n - \nu$
erasures, where the positions of the erasures are random. Additionally, an
eavesdropper (wire-tapper) is able to observe the transmitted codeword with $n
- \mu$ erasures in a similar fashion. This paper studies the maximum achievable
information rate with perfect secrecy on this channel and gives a coding scheme
using nested codes that achieves the secrecy capacity.
|
0902.3287
|
Adaptive Decoding of LDPC Codes with Binary Messages
|
cs.IT math.IT
|
A novel adaptive binary decoding algorithm for LDPC codes is proposed, which
reduces the decoding complexity while having a comparable or even better
performance than corresponding non-adaptive alternatives. In each iteration the
variable node decoders use the binary check node decoders multiple times; each
single use is referred to as a sub-iteration. To process the sequences of
binary messages in each iteration, the variable node decoders employ
pre-computed look-up tables. These look-up tables as well as the number of
sub-iterations per iteration are dynamically adapted during the decoding
process based on the decoder state, represented by the mutual information
between the current messages and the syndrome bits. The look-up tables and the
number of sub-iterations per iteration are determined and optimized using
density evolution. The performance and the complexity of the proposed adaptive
decoding algorithm is exemplified by simulations.
|
0902.3294
|
Progress in Computer-Assisted Inductive Theorem Proving by
Human-Orientedness and Descente Infinie?
|
cs.AI cs.LO
|
In this short position paper we briefly review the development history of
automated inductive theorem proving and computer-assisted mathematical
induction. We think that the current low expectations on progress in this field
result from a faulty narrow-scope historical projection. Our main motivation is
to explain--on an abstract but hopefully sufficiently descriptive level--why we
believe that future progress in the field is to result from human-orientedness
and descente infinie.
|
0902.3372
|
Gaussian Fading Is the Worst Fading
|
cs.IT math.IT
|
The capacity of peak-power limited, single-antenna, noncoherent, flat-fading
channels with memory is considered. The emphasis is on the capacity pre-log,
i.e., on the limiting ratio of channel capacity to the logarithm of the
signal-to-noise ratio (SNR), as the SNR tends to infinity. It is shown that,
among all stationary & ergodic fading processes of a given spectral
distribution function and whose law has no mass point at zero, the Gaussian
process gives rise to the smallest pre-log. The assumption that the law of the
fading process has no mass point at zero is essential in the sense that there
exist stationary & ergodic fading processes whose law has a mass point at zero
and that give rise to a smaller pre-log than the Gaussian process of equal
spectral distribution function. An extension of our results to multiple-input
single-output fading channels with memory is also presented.
|
0902.3373
|
Learning rules from multisource data for cardiac monitoring
|
cs.LG
|
This paper formalises the concept of learning symbolic rules from multisource
data in a cardiac monitoring context. Our sources, electrocardiograms and
arterial blood pressure measures, describe cardiac behaviours from different
viewpoints. To learn interpretable rules, we use an Inductive Logic Programming
(ILP) method. We develop an original strategy to cope with the dimensionality
issues caused by using this ILP technique on a rich multisource language. The
results show that our method greatly improves the feasibility and the
efficiency of the process while staying accurate. They also confirm the
benefits of using multiple sources to improve the diagnosis of cardiac
arrhythmias.
|
0902.3430
|
Domain Adaptation: Learning Bounds and Algorithms
|
cs.LG cs.AI
|
This paper addresses the general problem of domain adaptation which arises in
a variety of applications where the distribution of the labeled sample
available somewhat differs from that of the test data. Building on previous
work by Ben-David et al. (2007), we introduce a novel distance between
distributions, discrepancy distance, that is tailored to adaptation problems
with arbitrary loss functions. We give Rademacher complexity bounds for
estimating the discrepancy distance from finite samples for different loss
functions. Using this distance, we derive novel generalization bounds for
domain adaptation for a wide family of loss functions. We also present a series
of novel adaptation bounds for large classes of regularization-based
algorithms, including support vector machines and kernel ridge regression based
on the empirical discrepancy. This motivates our analysis of the problem of
minimizing the empirical discrepancy for various loss functions for which we
also give novel algorithms. We report the results of preliminary experiments
that demonstrate the benefits of our discrepancy minimization algorithms for
domain adaptation.
|
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