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1111.2988
|
Application of PSO, Artificial Bee Colony and Bacterial Foraging
Optimization algorithms to economic load dispatch: An analysis
|
cs.NE cs.AI
|
This paper illustrates successful implementation of three evolutionary
algorithms, namely- Particle Swarm Optimization(PSO), Artificial Bee Colony
(ABC) and Bacterial Foraging Optimization (BFO) algorithms to economic load
dispatch problem (ELD). Power output of each generating unit and optimum fuel
cost obtained using all three algorithms have been compared. The results
obtained show that ABC and BFO algorithms converge to optimal fuel cost with
reduced computational time when compared to PSO for the two example problems
considered.
|
1111.2991
|
Cyclotomic Constructions of Cyclic Codes with Length Being the Product
of Two Primes
|
cs.IT math.IT
|
Cyclic codes are an interesting type of linear codes and have applications in
communication and storage systems due to their efficient encoding and decoding
algorithms. They have been studied for decades and a lot of progress has been
made. In this paper, three types of generalized cyclotomy of order two and
three classes of cyclic codes of length $n_1n_2$ and dimension $(n_1n_2+1)/2$
are presented and analysed, where $n_1$ and $n_2$ are two distinct primes.
Bounds on their minimum odd-like weight are also proved. The three
constructions produce the best cyclic codes in certain cases.
|
1111.3000
|
Digital Manifolds and the Theorem of Jordan-Brouwer
|
cs.CV math.GT
|
We give an answer to the question given by T.Y.Kong in his article "Can 3-D
Digital Topology be Based on Axiomatically Defined Digital Spaces?" In this
article he asks the question, if so called "good pairs" of neighborhood
relations can be found on the set Z^n such that the existence of digital
manifolds of dimension n-1, that separate their complement in exactly two
connected sets, is guaranteed. To achieve this, we use a technique developed by
M. Khachan et.al. A set given in Z^n is translated into a simplicial complex
that can be used to study the topological properties of the original discrete
point-set. In this way, one is able to define the notion of a (n-1)-dimensional
digital manifold and prove the digital analog of the Jordan-Brouwer-Theorem.
|
1111.3025
|
Intelligent Distributed Production Control
|
cs.SY
|
This editorial introduces the special issue of the Springer journal, Journal
of Intelligent Manufacturing, on intelligent distributed production control.
This special issue contains selected papers presented at the 13th IFAC
Symposium on Information Control Problems in Manufacturing - INCOM'2009
(Bakhtadze and Dolgui, 2009). The papers in this special issue were selected
because of their high quality and their specific way of addressing the variety
of issues dealing with intelligent distributed production control. Previous
global discussions about the state of the art in intelligent distributed
production control are provided, as well as exploratory guidelines for future
research in this area.
|
1111.3033
|
ModuLand plug-in for Cytoscape: determination of hierarchical layers of
overlapping network modules and community centrality
|
physics.comp-ph cond-mat.dis-nn cs.SI q-bio.MN
|
Summary: The ModuLand plug-in provides Cytoscape users an algorithm for
determining extensively overlapping network modules. Moreover, it identifies
several hierarchical layers of modules, where meta-nodes of the higher
hierarchical layer represent modules of the lower layer. The tool assigns
module cores, which predict the function of the whole module, and determines
key nodes bridging two or multiple modules. The plug-in has a detailed
JAVA-based graphical interface with various colouring options. The ModuLand
tool can run on Windows, Linux, or Mac OS. We demonstrate its use on protein
structure and metabolic networks. Availability: The plug-in and its user guide
can be downloaded freely from: http://www.linkgroup.hu/modules.php. Contact:
csermely.peter@med.semmelweis-univ.hu Supplementary information: Supplementary
information is available at Bioinformatics online.
|
1111.3048
|
On a Connection Between Small Set Expansions and Modularity Clustering
in Social Networks
|
cs.SI cs.CC physics.soc-ph
|
In this paper we explore a connection between two seemingly different
problems from two different domains: the small-set expansion problem studied in
unique games conjecture, and a popular community finding approach for social
networks known as the modularity clustering approach. We show that a
sub-exponential time algorithm for the small-set expansion problem leads to a
sub-exponential time constant factor approximation for some hard input
instances of the modularity clustering problem.
|
1111.3069
|
A fusion algorithm for joins based on collections in Odra (Object
Database for Rapid Application development)
|
cs.DB
|
In this paper we present the functionality of a currently under development
database programming methodology called ODRA (Object Database for Rapid
Application development) which works fully on the object oriented principles.
The database programming language is called SBQL (Stack based query language).
We discuss some concepts in ODRA for e.g. the working of ODRA, how ODRA runtime
environment operates, the interoperability of ODRA with .net and java .A view
of ODRA's working with web services and xml. Currently the stages under
development in ODRA are query optimization. So we present the prior work that
is done in ODRA related to Query optimization and we also present a new fusion
algorithm of how ODRA can deal with joins based on collections like set, lists,
and arrays for query optimization.
|
1111.3106
|
Practical Distributed Control Synthesis
|
cs.LO cs.SY
|
Classic distributed control problems have an interesting dichotomy: they are
either trivial or undecidable. If we allow the controllers to fully
synchronize, then synthesis is trivial. In this case, controllers can
effectively act as a single controller with complete information, resulting in
a trivial control problem. But when we eliminate communication and restrict the
supervisors to locally available information, the problem becomes undecidable.
In this paper we argue in favor of a middle way. Communication is, in most
applications, expensive, and should hence be minimized. We therefore study a
solution that tries to communicate only scarcely and, while allowing
communication in order to make joint decision, favors local decisions over
joint decisions that require communication.
|
1111.3108
|
Synthesis of Switching Rules for Ensuring Reachability Properties of
Sampled Linear Systems
|
cs.LO cs.SY
|
We consider here systems with piecewise linear dynamics that are periodically
sampled with a given period {\tau} . At each sampling time, the mode of the
system, i.e., the parameters of the linear dynamics, can be switched, according
to a switching rule. Such systems can be modelled as a special form of hybrid
automata, called "switched systems", that are automata with an infinite real
state space. The problem is to find a switching rule that guarantees the system
to still be in a given area V at the next sampling time, and so on
indefinitely. In this paper, we will consider two approaches: the indirect one
that abstracts the system under the form of a finite discrete event system, and
the direct one that works on the continuous state space.
Our methods rely on previous works, but we specialize them to a simplified
context (linearity, periodic switching instants, absence of control input),
which is motivated by the features of a focused case study: a DC-DC boost
converter built by electronics laboratory SATIE (ENS Cachan). Our enhanced
methods allow us to treat successfully this real-life example.
|
1111.3122
|
ESLO: from transcription to speakers' personal information annotation
|
cs.CL
|
This paper presents the preliminary works to put online a French oral corpus
and its transcription. This corpus is the Socio-Linguistic Survey in Orleans,
realized in 1968. First, we numerized the corpus, then we handwritten
transcribed it with the Transcriber software adding different tags about
speakers, time, noise, etc. Each document (audio file and XML file of the
transcription) was described by a set of metadata stored in an XML format to
allow an easy consultation. Second, we added different levels of annotations,
recognition of named entities and annotation of personal information about
speakers. This two annotation tasks used the CasSys system of transducer
cascades. We used and modified a first cascade to recognize named entities.
Then we built a second cascade to annote the designating entities, i.e.
information about the speaker. These second cascade parsed the named entity
annotated corpus. The objective is to locate information about the speaker and,
also, what kind of information can designate him/her. These two cascades was
evaluated with precision and recall measures.
|
1111.3127
|
Tracing the temporal evolution of clusters in a financial stock market
|
cs.CE math.ST q-fin.ST stat.TH
|
We propose a methodology for clustering financial time series of stocks'
returns, and a graphical set-up to quantify and visualise the evolution of
these clusters through time. The proposed graphical representation allows for
the application of well known algorithms for solving classical combinatorial
graph problems, which can be interpreted as problems relevant to portfolio
design and investment strategies. We illustrate this graph representation of
the evolution of clusters in time and its use on real data from the Madrid
Stock Exchange market.
|
1111.3152
|
\'Evaluation de lexiques syntaxiques par leur int\'egartion dans
l'analyseur syntaxiques FRMG
|
cs.CL
|
In this paper, we evaluate various French lexica with the parser FRMG: the
Lefff, LGLex, the lexicon built from the tables of the French Lexicon-Grammar,
the lexicon DICOVALENCE and a new version of the verbal entries of the Lefff,
obtained by merging with DICOVALENCE and partial manual validation. For this,
all these lexica have been converted to the format of the Lefff, Alexina
format. The evaluation was made on the part of the EASy corpus used in the
first evaluation campaign Passage.
|
1111.3153
|
Construction du lexique LGLex \`a partir des tables du Lexique-Grammaire
des verbes du grec moderne
|
cs.CL
|
In this paper, we summerize the work done on the resources of Modern Greek on
the Lexicon-Grammar of verbs. We detail the definitional features of each
table, and all changes made to the names of features to make them consistent.
Through the development of the table of classes, including all the features, we
have considered the conversion of tables in a syntactic lexicon: LGLex. The
lexicon, in plain text format or XML, is generated by the LGExtract tool
(Constant & Tolone, 2010). This format is directly usable in applications of
Natural Language Processing (NLP).
|
1111.3160
|
On the Spatial Degrees of Freedom of Multicell and Multiuser MIMO
Channels
|
cs.IT math.IT
|
We study the converse and achievability for the degrees of freedom of the
multicellular multiple-input multiple-output (MIMO) multiple access channel
(MAC) with constant channel coefficients. We assume L>1 homogeneous cells with
K>0 users per cell where the users have M antennas and the base stations are
equipped with N antennas. The degrees of freedom outer bound for this L-cell
and K-user MIMO MAC is formulated. The characterized outer bound uses insight
from a limit on the total degrees of freedom for the L-cell heterogeneous MIMO
network. We also show through an example that a scheme selecting a transmitter
and performing partial message sharing outperforms a multiple distributed
transmission strategy in terms of the total degrees of freedom. Simple linear
schemes attaining the outer bound (i.e., those achieving the optimal degrees of
freedom) are explores for a few cases. The conditions for the required spatial
dimensions attaining the optimal degrees of freedom are characterized in terms
of K, L, and the number of transmit streams. The optimal degrees of freedom for
the two-cell MIMO MAC are examined by using transmit zero forcing and null
space interference alignment and subsequently, simple receive zero forcing is
shown to provide the optimal degrees of freedom for L>1. By the uplink and
downlink duality, the degrees of freedom results in this paper are also
applicable to the downlink. In the downlink scenario, we study the degrees of
freedom of L-cell MIMO interference channel exploring multiuser diversity.
Strong convergence modes of the instantaneous degrees of freedom as the number
of users increases are characterized.
|
1111.3163
|
On the Derivation of Optimal Partial Successive Interference
Cancellation
|
cs.IT math.IT
|
The necessity of accurate channel estimation for Successive and Parallel
Interference Cancellation is well known. Iterative channel estimation and
channel decoding (for instance by means of the Expectation-Maximization
algorithm) is particularly important for these multiuser detection schemes in
the presence of time varying channels, where a high density of pilots is
necessary to track the channel. This paper designs a method to analytically
derive a weighting factor $\alpha$, necessary to improve the efficiency of
interference cancellation in the presence of poor channel estimates. Moreover,
this weighting factor effectively mitigates the presence of incorrect decisions
at the output of the channel decoder. The analysis provides insight into the
properties of such interference cancellation scheme and the proposed approach
significantly increases the effectiveness of Successive Interference
Cancellation under the presence of channel estimation errors, which leads to
gains of up to 3 dB.
|
1111.3166
|
On the Concatenation of Non-Binary Random Linear Fountain Codes with
Maximum Distance Separable Codes
|
cs.IT math.IT
|
A novel fountain coding scheme has been introduced. The scheme consists of a
parallel concatenation of a MDS block code with a LRFC code, both constructed
over the same field, $F_q$. The performance of the concatenated fountain coding
scheme has been analyzed through derivation of tight bounds on the probability
of decoding failure as a function of the overhead. It has been shown how the
concatenated scheme performs as well as LRFC codes in channels characterized by
high erasure probabilities, whereas they provide failure probabilities lower by
several orders of magnitude at moderate/low erasure probabilities.
|
1111.3176
|
The influence of the network topology on epidemic spreading
|
physics.soc-ph cond-mat.stat-mech cs.SI
|
The influence of the network's structure on the dynamics of spreading
processes has been extensively studied in the last decade. Important results
that partially answer this question show a weak connection between the
macroscopic behavior of these processes and specific structural properties in
the network, such as the largest eigenvalue of a topology related matrix.
However, little is known about the direct influence of the network topology on
microscopic level, such as the influence of the (neighboring) network on the
probability of a particular node's infection. To answer this question, we
derive both an upper and a lower bound for the probability that a particular
node is infective in a susceptible-infective-susceptible model for two cases of
spreading processes: reactive and contact processes. The bounds are derived by
considering the $n-$hop neighborhood of the node; the bounds are tighter as one
uses a larger $n-$hop neighborhood to calculate them. Consequently, using local
information for different neighborhood sizes, we assess the extent to which the
topology influences the spreading process, thus providing also a strong
macroscopic connection between the former and the latter. Our findings are
complemented by numerical results for a real-world e-mail network. A very good
estimate for the infection density $\rho$ is obtained using only 2-hop
neighborhoods which account for 0.4% of the entire network topology on average.
|
1111.3182
|
Context Tree Switching
|
cs.IT math.IT
|
This paper describes the Context Tree Switching technique, a modification of
Context Tree Weighting for the prediction of binary, stationary, n-Markov
sources. By modifying Context Tree Weighting's recursive weighting scheme, it
is possible to mix over a strictly larger class of models without increasing
the asymptotic time or space complexity of the original algorithm. We prove
that this generalization preserves the desirable theoretical properties of
Context Tree Weighting on stationary n-Markov sources, and show empirically
that this new technique leads to consistent improvements over Context Tree
Weighting as measured on the Calgary Corpus.
|
1111.3200
|
On the Application of the Baum-Welch Algorithm for Modeling the Land
Mobile Satellite Channel
|
cs.IT math.IT
|
Accurate channel models are of high importance for the design of upcoming
mobile satellite systems. Nowadays most of the models for the LMSC are based on
Markov chains and rely on measurement data, rather than on pure theoretical
considerations. A key problem lies in the determination of the model parameters
out of the observed data. In this work we face the issue of state
identification of the underlying Markov model whose model parameters are a
priori unknown. This can be seen as a HMM problem. For finding the ML estimates
of such model parameters the BW algorithm is adapted to the context of channel
modeling. Numerical results on test data sequences reveal the capabilities of
the proposed algorithm. Results on real measurement data are finally presented.
|
1111.3204
|
Time Interference Alignment via Delay Offset for Long Delay Networks
|
cs.IT math.IT
|
Time Interference Alignment is a flavor of Interference Alignment that
increases the network capacity by suitably staggering the transmission delays
of the senders. In this work the analysis of the existing literature is
generalized and the focus is on the computation of the dof for networks with
randomly placed users in a n-dimensional Euclidean space. In the basic case
without coordination among the transmitters analytical expressions of the sum
dof can be derived. If the transmit delays are coordinated, in 20% of the cases
time Interference Alignment yields additional dof with respect to orthogonal
access schemes. The potential capacity improvements for satellite networks are
also investigated.
|
1111.3240
|
Salt-and-Pepper Noise Removal Based on Sparse Signal Processing
|
cs.IT math.IT
|
In this paper, we propose a new method for Salt-and-Pepper noise removal from
images. Whereas most of the existing methods are based on Ordered Statistics
filters, our method is based on the growing theory of Sparse Signal Processing.
In other words, we convert the problem of denoising into a sparse signal
reconstruction problem which can be dealt with the corresponding techniques. As
a result, the output image of our method is preserved from the undesirable
opacity which is a disadvantage of most of the other methods. We also introduce
an efficient reconstruction algorithm which will be used in our method.
Simulation results indicate that our method outperforms the other best-known
methods both in term of PSNR and visual criterion. Furthermore, our method can
be easily used for reconstruction of missing samples in erasure channels.
|
1111.3270
|
Mining Biclusters of Similar Values with Triadic Concept Analysis
|
cs.DS cs.AI cs.DB
|
Biclustering numerical data became a popular data-mining task in the
beginning of 2000's, especially for analysing gene expression data. A bicluster
reflects a strong association between a subset of objects and a subset of
attributes in a numerical object/attribute data-table. So called biclusters of
similar values can be thought as maximal sub-tables with close values. Only few
methods address a complete, correct and non redundant enumeration of such
patterns, which is a well-known intractable problem, while no formal framework
exists. In this paper, we introduce important links between biclustering and
formal concept analysis. More specifically, we originally show that Triadic
Concept Analysis (TCA), provides a nice mathematical framework for
biclustering. Interestingly, existing algorithms of TCA, that usually apply on
binary data, can be used (directly or with slight modifications) after a
preprocessing step for extracting maximal biclusters of similar values.
|
1111.3271
|
On Bellman's principle with inequality constraints
|
math.OC cs.SY math.PR
|
We consider an example by Haviv (1996) of a constrained Markov decision
process that, in some sense, violates Bellman's principle. We resolve this
issue by showing how to preserve a form of Bellman's principle that accounts
for a change of constraint at states that are reachable from the initial state.
|
1111.3274
|
Pilotless Recovery of Clipped OFDM Signals by Compressive Sensing over
Reliable Data Carriers
|
cs.IT math.IT
|
In this paper we propose a novel form of clipping mitigation in OFDM using
compressive sensing that completely avoids tone reservation and hence rate loss
for this purpose. The method builds on selecting the most reliable
perturbations from the constellation lattice upon decoding at the receiver, and
performs compressive sensing over these observations in order to completely
recover the temporally sparse nonlinear distortion. As such, the method
provides a unique practical solution to the problem of initial erroneous
decoding decisions in iterative ML methods, offering both the ability to
augment these techniques and to solely recover the distorted signal in one
shot.
|
1111.3275
|
Information storage capacity of discrete spin systems
|
cs.IT cond-mat.str-el math-ph math.IT math.MP nlin.CG quant-ph
|
Understanding the limits imposed on information storage capacity of physical
systems is a problem of fundamental and practical importance which bridges
physics and information science. There is a well-known upper bound on the
amount of information that can be stored reliably in a given volume of discrete
spin systems which are supported by gapped local Hamiltonians. However, all the
previously known systems were far below this theoretical bound, and it remained
open whether there exists a gapped spin system that saturates this bound. Here,
we present a construction of spin systems which saturate this theoretical limit
asymptotically by borrowing an idea from fractal properties arising in the
Sierpinski triangle. Our construction provides not only the best classical
error-correcting code which is physically realizable as the energy ground space
of gapped frustration-free Hamiltonians, but also a new research avenue for
correlated spin phases with fractal spin configurations.
|
1111.3281
|
A prototype system for handwritten sub-word recognition: Toward
Arabic-manuscript transliteration
|
cs.CV cs.IR
|
A prototype system for the transliteration of diacritics-less Arabic
manuscripts at the sub-word or part of Arabic word (PAW) level is developed.
The system is able to read sub-words of the input manuscript using a set of
skeleton-based features. A variation of the system is also developed which
reads archigraphemic Arabic manuscripts, which are dot-less, into
archigraphemes transliteration. In order to reduce the complexity of the
original highly multiclass problem of sub-word recognition, it is redefined
into a set of binary descriptor classifiers. The outputs of trained binary
classifiers are combined to generate the sequence of sub-word letters. SVMs are
used to learn the binary classifiers. Two specific Arabic databases have been
developed to train and test the system. One of them is a database of the Naskh
style. The initial results are promising. The systems could be trained on other
scripts found in Arabic manuscripts.
|
1111.3304
|
Eigenvector Synchronization, Graph Rigidity and the Molecule Problem
|
cs.CE cs.DS math.CO q-bio.QM
|
The graph realization problem has received a great deal of attention in
recent years, due to its importance in applications such as wireless sensor
networks and structural biology. In this paper, we extend on previous work and
propose the 3D-ASAP algorithm, for the graph realization problem in
$\mathbb{R}^3$, given a sparse and noisy set of distance measurements. 3D-ASAP
is a divide and conquer, non-incremental and non-iterative algorithm, which
integrates local distance information into a global structure determination.
Our approach starts with identifying, for every node, a subgraph of its 1-hop
neighborhood graph, which can be accurately embedded in its own coordinate
system. In the noise-free case, the computed coordinates of the sensors in each
patch must agree with their global positioning up to some unknown rigid motion,
that is, up to translation, rotation and possibly reflection. In other words,
to every patch there corresponds an element of the Euclidean group Euc(3) of
rigid transformations in $\mathbb{R}^3$, and the goal is to estimate the group
elements that will properly align all the patches in a globally consistent way.
Furthermore, 3D-ASAP successfully incorporates information specific to the
molecule problem in structural biology, in particular information on known
substructures and their orientation. In addition, we also propose 3D-SP-ASAP, a
faster version of 3D-ASAP, which uses a spectral partitioning algorithm as a
preprocessing step for dividing the initial graph into smaller subgraphs. Our
extensive numerical simulations show that 3D-ASAP and 3D-SP-ASAP are very
robust to high levels of noise in the measured distances and to sparse
connectivity in the measurement graph, and compare favorably to similar
state-of-the art localization algorithms.
|
1111.3374
|
From Caesar to Twitter: An Axiomatic Approach to Elites of Social
Networks
|
cs.SI physics.soc-ph
|
In many societies there is an elite, a relatively small group of powerful
individuals that is well-connected and highly influential. Since the ancient
days of Julius Caesar's senate of Rome to the recent days of celebrities on
Twitter, the size of the elite is a result of conflicting social forces
competing to increase or decrease it.
The main contribution of this paper is the answer to the question how large
the elite is at equilibrium. We take an axiomatic approach to solve this:
assuming that an elite exists and it is influential, stable and either minimal
or dense, we prove that its size must be $\Theta(\sqrt{m})$ (where $m$ is the
number of edges in the network).
As an approximation for the elite, we then present an empirical study on nine
large real-world networks of the subgraph formed by the highest degree nodes,
also known as the rich-club. Our findings indicate that elite properties such
as disproportionate influence, stability and density of
$\Theta(\sqrt{m})$-rich-clubs are universal properties and should join a
growing list of common phenomena shared by social networks and complex systems
such as "small world," power law degree distributions, high clustering, etc.
|
1111.3376
|
Fingerprinting with Equiangular Tight Frames
|
cs.IT cs.MM math.IT
|
Digital fingerprinting is a framework for marking media files, such as
images, music, or movies, with user-specific signatures to deter illegal
distribution. Multiple users can collude to produce a forgery that can
potentially overcome a fingerprinting system. This paper proposes an
equiangular tight frame fingerprint design which is robust to such collusion
attacks. We motivate this design by considering digital fingerprinting in terms
of compressed sensing. The attack is modeled as linear averaging of multiple
marked copies before adding a Gaussian noise vector. The content owner can then
determine guilt by exploiting correlation between each user's fingerprint and
the forged copy. The worst-case error probability of this detection scheme is
analyzed and bounded. Simulation results demonstrate the average-case
performance is similar to the performance of orthogonal and simplex fingerprint
designs, while accommodating several times as many users.
|
1111.3393
|
Infinite Excess Entropy Processes with Countable-State Generators
|
cs.IT cond-mat.stat-mech math.IT math.PR nlin.CD
|
We present two examples of finite-alphabet, infinite excess entropy processes
generated by invariant hidden Markov models (HMMs) with countable state sets.
The first, simpler example is not ergodic, but the second is. It appears these
are the first constructions of processes of this type. Previous examples of
infinite excess entropy processes over finite alphabets admit only invariant
HMM presentations with uncountable state sets.
|
1111.3395
|
The Capacity of a Class of Multi-Way Relay Channels
|
cs.IT math.IT
|
The capacity of a class of multi-way relay channels, where L users
communicate via a relay (at possibly different rates), is derived for the case
where the channel outputs are modular sums of the channel inputs and the
receiver noise. The cut-set upper bound to the capacity is shown to be
achievable. More specifically, the capacity is achieved using (i) rate
splitting, (ii) functional-decode-forward, and (iii) joint source-channel
coding. We note that while separate source-channel coding can achieve the
common-rate capacity, joint source-channel coding is used to achieve the
capacity for the general case where the users are transmitting at different
rates.
|
1111.3396
|
Functional-Decode-Forward for the General Discrete Memoryless Two-Way
Relay Channel
|
cs.IT math.IT
|
We consider the general discrete memoryless two-way relay channel, where two
users exchange messages via a relay, and propose two functional-decode-forward
coding strategies for this channel. Functional-decode-forward involves the
relay decoding a function of the users' messages rather than the individual
messages themselves. This function is then broadcast back to the users, which
can be used in conjunction with the user's own message to decode the other
user's message. Via a numerical example, we show that functional-decode-forward
with linear codes is capable of achieving strictly larger sum rates than those
achievable by other strategies.
|
1111.3403
|
Upper bounds on the smallest size of a complete arc in the plane PG(2,q)
|
math.CO cs.IT math.IT
|
New upper bounds on the smallest size t_{2}(2,q) of a complete arc in the
projective plane PG(2,q) are obtained for q <= 9109. From these new bounds it
follows that for q <= 2621 and q = 2659,2663,2683,2693,2753,2801, the relation
t_{2}(2,q) < 4.5\sqrt{q} holds. Also, for q <= 5399 and q =
5413,5417,5419,5441,5443,5471,5483,5501,5521, we have t_{2}(2,q) < 4.8\sqrt{q}.
Finally, for q <= 9067 it holds that t_{2}(2,q) < 5\sqrt{q}. The new upper
bounds are obtained by finding new small complete arcs with the help of a
computer search using randomized greedy algorithms.
|
1111.3412
|
Outage probability of selective decode and forward relaying with secrecy
constraints
|
cs.IT math.IT
|
We study the outage probability of opportunistic relay selection in
decode-and-forward relaying with secrecy constraints. We derive the closed-form
expression for the outage probability. Based on the analytical result, the
asymptotic performance is then investigated. The accuracy of our performance
analysis is verified by the simulation results.
|
1111.3420
|
Optimal Self-Dual Z4-Codes and a Unimodular Lattice in Dimension 41
|
math.CO cs.IT math.IT math.NT
|
For lengths up to 47 except 37, we determine the largest minimum Euclidean
weight among all Type I Z4-codes of that length. We also give the first example
of an optimal odd unimodular lattice in dimension 41 explicitly, which is
constructed from some Type I Z4-code of length 41.
|
1111.3427
|
Joint Spectral Radius and Path-Complete Graph Lyapunov Functions
|
math.OC cs.SY
|
We introduce the framework of path-complete graph Lyapunov functions for
approximation of the joint spectral radius. The approach is based on the
analysis of the underlying switched system via inequalities imposed among
multiple Lyapunov functions associated to a labeled directed graph. Inspired by
concepts in automata theory and symbolic dynamics, we define a class of graphs
called path-complete graphs, and show that any such graph gives rise to a
method for proving stability of the switched system. This enables us to derive
several asymptotically tight hierarchies of semidefinite programming
relaxations that unify and generalize many existing techniques such as common
quadratic, common sum of squares, and maximum/minimum-of-quadratics Lyapunov
functions. We compare the quality of approximation obtained by certain classes
of path-complete graphs including a family of dual graphs and all path-complete
graphs with two nodes on an alphabet of two matrices. We provide approximation
guarantees for several families of path-complete graphs, such as the De Bruijn
graphs, establishing as a byproduct a constructive converse Lyapunov theorem
for maximum/minimum-of-quadratics Lyapunov functions.
|
1111.3462
|
Extending the adverbial coverage of a NLP oriented resource for French
|
cs.CL
|
This paper presents a work on extending the adverbial entries of LGLex: a NLP
oriented syntactic resource for French. Adverbs were extracted from the
Lexicon-Grammar tables of both simple adverbs ending in -ment '-ly' (Molinier
and Levrier, 2000) and compound adverbs (Gross, 1986; 1990). This work relies
on the exploitation of fine-grained linguistic information provided in existing
resources. Various features are encoded in both LG tables and they haven't been
exploited yet. They describe the relations of deleting, permuting, intensifying
and paraphrasing that associate, on the one hand, the simple and compound
adverbs and, on the other hand, different types of compound adverbs. The
resulting syntactic resource is manually evaluated and freely available under
the LGPL-LR license.
|
1111.3477
|
The cross-correlation distribution of a $p$-ary $m$-sequence of period
$p^{2m}-1$ and its decimation by $\frac{(p^{m}+1)^{2}}{2(p^{e}+1)}$
|
cs.IT math.IT
|
Let $n=2m$, $m$ odd, $e|m$, and $p$ odd prime with $p\equiv1\ \mathrm{mod}\
4$. Let $d=\frac{(p^{m}+1)^{2}}{2(p^{e}+1)}$. In this paper, we study the
cross-correlation between a $p$-ary $m$-sequence $\{s_{t}\}$ of period
$p^{2m}-1$ and its decimation $\{s_{dt}\}$. Our result shows that the
cross-correlation function is six-valued and that it takes the values in
$\{-1,\ \pm p^{m}-1,\ \frac{1\pm p^{\frac{e}{2}}}{2}p^{m}-1,\ \frac{(1-
p^{e})}{2}p^{m}-1\}$. Also, the distribution of the cross-correlation is
completely determined.
|
1111.3530
|
Preliminary Analysis of Google+'s Privacy
|
cs.SI cs.CR
|
In this paper we provide a preliminary analysis of Google+ privacy. We
identified that Google+ shares photo metadata with users who can access the
photograph and discuss its potential impact on privacy. We also identified that
Google+ encourages the provision of other names including maiden name, which
may help criminals performing identity theft. We show that Facebook lists are a
superset of Google+ circles, both functionally and logically, even though
Google+ provides a better user interface. Finally we compare the use of
encryption and depth of privacy control in Google+ versus in Facebook.
|
1111.3567
|
On the Measurement of Privacy as an Attacker's Estimation Error
|
cs.IT cs.CR math.IT
|
A wide variety of privacy metrics have been proposed in the literature to
evaluate the level of protection offered by privacy enhancing-technologies.
Most of these metrics are specific to concrete systems and adversarial models,
and are difficult to generalize or translate to other contexts. Furthermore, a
better understanding of the relationships between the different privacy metrics
is needed to enable more grounded and systematic approach to measuring privacy,
as well as to assist systems designers in selecting the most appropriate metric
for a given application.
In this work we propose a theoretical framework for privacy-preserving
systems, endowed with a general definition of privacy in terms of the
estimation error incurred by an attacker who aims to disclose the private
information that the system is designed to conceal. We show that our framework
permits interpreting and comparing a number of well-known metrics under a
common perspective. The arguments behind these interpretations are based on
fundamental results related to the theories of information, probability and
Bayes decision.
|
1111.3602
|
On the Rabin signature
|
cs.CR cs.IT math.IT
|
Some Rabin signature schemes may be exposed to forgery; several variants are
here described to counter this vulnerability. Blind Rabin signatures are also
discussed.
|
1111.3616
|
An Experimental Investigation of SIMO, MIMO, Interference-Alignment (IA)
and Coordinated Multi-Point (CoMP)
|
cs.IT math.IT
|
In this paper we present experimental implementations of interference
alignment (IA) and coordinated multi-point transmission (CoMP). We provide
results for a system with three base-stations and three mobile-stations all
having two antennas. We further employ OFDM modulation, with high-order
constellations, and measure many positions both line-of-sight and
non-line-of-sight under interference limited conditions. We find the CoMP
system to perform better than IA at the cost of a higher back-haul capacity
requirement. During the measurements we also logged the channel estimates for
off-line processing. We use these channel estimates to calculate the
performance under ideal conditions. The performance estimates obtained this way
is substantially higher than what is actually observed in the end-to-end
transmissions---in particular in the CoMP case where the theoretical
performance is very high. We find the reason for this discrepancy to be the
impact of dirty-RF effects such as phase-noise and non-linearities. We are able
to model the dirty-RF effects to some extent. These models can be used to
simulate more complex systems and still account for the dirty-RF effects (e.g.,
systems with tens of mobiles and base-stations). Both IA and CoMP perform
better than reference implementations of single-user SIMO and MIMO in our
measurements.
|
1111.3645
|
Classical codes for quantum broadcast channels
|
quant-ph cs.IT math.IT
|
We present two approaches for transmitting classical information over quantum
broadcast channels. The first technique is a quantum generalization of the
superposition coding scheme for the classical broadcast channel. We use a
quantum simultaneous nonunique decoder and obtain a proof of the rate region
stated in [Yard et al., IEEE Trans. Inf. Theory 57 (10), 2011]. Our second
result is a quantum generalization of the Marton coding scheme. The error
analysis for the quantum Marton region makes use of ideas in our earlier work
and an idea recently presented by Radhakrishnan et al. in arXiv:1410.3248. Both
results exploit recent advances in quantum simultaneous decoding developed in
the context of quantum interference channels.
|
1111.3652
|
Features and heterogeneities in growing network models
|
physics.soc-ph cond-mat.dis-nn cs.SI q-bio.MN
|
Many complex networks from the World-Wide-Web to biological networks are
growing taking into account the heterogeneous features of the nodes. The
feature of a node might be a discrete quantity such as a classification of a
URL document as personal page, thematic website, news, blog, search engine,
social network, ect. or the classification of a gene in a functional module.
Moreover the feature of a node can be a continuous variable such as the
position of a node in the embedding space. In order to account for these
properties, in this paper we provide a generalization of growing network models
with preferential attachment that includes the effect of heterogeneous features
of the nodes. The main effect of heterogeneity is the emergence of an
"effective fitness" for each class of nodes, determining the rate at which
nodes acquire new links. The degree distribution exhibits a multiscaling
behaviour analogous to the the fitness model. This property is robust with
respect to variations in the model, as long as links are assigned through
effective preferential attachment. Beyond the degree distribution, in this
paper we give a full characterization of the other relevant properties of the
model. We evaluate the clustering coefficient and show that it disappears for
large network size, a property shared with the Barab\'asi-Albert model.
Negative degree correlations are also present in the studied class of models,
along with non-trivial mixing patterns among features. We therefore conclude
that both small clustering coefficients and disassortative mixing are outcomes
of the preferential attachment mechanism in general growing networks.
|
1111.3659
|
Living in Living Cities
|
nlin.AO cs.SI physics.soc-ph
|
This paper presents an overview of current and potential applications of
living technology to some urban problems. Living technology can be described as
technology that exhibits the core features of living systems. These features
can be useful to solve dynamic problems. In particular, urban problems
concerning mobility, logistics, telecommunications, governance, safety,
sustainability, and society and culture are presented, while solutions
involving living technology are reviewed. A methodology for developing living
technology is mentioned, while supraoptimal public transportation systems are
used as a case study to illustrate the benefits of urban living technology.
Finally, the usefulness of describing cities as living systems is discussed.
|
1111.3689
|
CBLOCK: An Automatic Blocking Mechanism for Large-Scale De-duplication
Tasks
|
cs.DB
|
De-duplication---identification of distinct records referring to the same
real-world entity---is a well-known challenge in data integration. Since very
large datasets prohibit the comparison of every pair of records, {\em blocking}
has been identified as a technique of dividing the dataset for pairwise
comparisons, thereby trading off {\em recall} of identified duplicates for {\em
efficiency}. Traditional de-duplication tasks, while challenging, typically
involved a fixed schema such as Census data or medical records. However, with
the presence of large, diverse sets of structured data on the web and the need
to organize it effectively on content portals, de-duplication systems need to
scale in a new dimension to handle a large number of schemas, tasks and data
sets, while handling ever larger problem sizes. In addition, when working in a
map-reduce framework it is important that canopy formation be implemented as a
{\em hash function}, making the canopy design problem more challenging. We
present CBLOCK, a system that addresses these challenges. CBLOCK learns hash
functions automatically from attribute domains and a labeled dataset consisting
of duplicates. Subsequently, CBLOCK expresses blocking functions using a
hierarchical tree structure composed of atomic hash functions. The application
may guide the automated blocking process based on architectural constraints,
such as by specifying a maximum size of each block (based on memory
requirements), impose disjointness of blocks (in a grid environment), or
specify a particular objective function trading off recall for efficiency. As a
post-processing step to automatically generated blocks, CBLOCK {\em rolls-up}
smaller blocks to increase recall. We present experimental results on two
large-scale de-duplication datasets at Yahoo!---consisting of over 140K movies
and 40K restaurants respectively---and demonstrate the utility of CBLOCK.
|
1111.3690
|
New Candidates Welcome! Possible Winners with respect to the Addition of
New Candidates
|
cs.AI
|
In voting contexts, some new candidates may show up in the course of the
process. In this case, we may want to determine which of the initial candidates
are possible winners, given that a fixed number $k$ of new candidates will be
added. We give a computational study of this problem, focusing on scoring
rules, and we provide a formal comparison with related problems such as control
via adding candidates or cloning.
|
1111.3696
|
Achieving AWGN Channel Capacity with Sparse Graph Modulation and "In the
Air" Coupling
|
cs.IT math.IT
|
Communication over a multiple access channel is considered. Each user
modulates his signal as a superposition of redundant data streams where
interconnection of data bits can be represented by means of a sparse graph. The
receiver observes a signal resulting from the coupling of the sparse modulation
graphs. Iterative interference cancellation decoding is analyzed. It is proved
that spatial graph coupling allows to achieve the AWGN channel capacity with
equal power transmissions.
|
1111.3728
|
Variability Aware Network Utility Maximization
|
cs.SY cs.NI math.OC
|
Network Utility Maximization (NUM) provides the key conceptual framework to
study resource allocation amongst a collection of users/entities across
disciplines as diverse as economics, law and engineering. In network
engineering, this framework has been particularly insightful towards
understanding how Internet protocols allocate bandwidth, and motivated diverse
research on distributed mechanisms to maximize network utility while
incorporating new relevant constraints, on energy/power, storage, stability,
etc., for systems ranging from communication networks to the smart-grid.
However when the available resources and/or users' utilities vary over time, a
user's allocations will tend to vary, which in turn may have a detrimental
impact on the users' utility or quality of experience. This paper introduces a
generalized NUM framework which explicitly incorporates the detrimental impact
of temporal variability in a user's allocated rewards. It explicitly
incorporates tradeoffs amongst the mean and variability in users' allocations.
We propose an online algorithm to realize variance-sensitive NUM, which, under
stationary ergodic assumptions, is shown to be asymptotically optimal, i.e.,
achieves a time-average equal to that of an offline algorithm with knowledge of
the future variability in the system. This substantially extends work on NUM to
an interesting class of relevant problems where users/entities are sensitive to
temporal variability in their service or allocated rewards.
|
1111.3735
|
A Bayesian Model for Plan Recognition in RTS Games applied to StarCraft
|
cs.LG cs.AI
|
The task of keyhole (unobtrusive) plan recognition is central to adaptive
game AI. "Tech trees" or "build trees" are the core of real-time strategy (RTS)
game strategic (long term) planning. This paper presents a generic and simple
Bayesian model for RTS build tree prediction from noisy observations, which
parameters are learned from replays (game logs). This unsupervised machine
learning approach involves minimal work for the game developers as it leverage
players' data (com- mon in RTS). We applied it to StarCraft1 and showed that it
yields high quality and robust predictions, that can feed an adaptive AI.
|
1111.3739
|
The function space to describe the dynamics of linear systems
|
cs.SY
|
Usually, the dynamics of linear time-invariant systems described by an
integral operator of convolution type, which is defined in the Hilbert space of
Lebesgue square integrable functions on the whole line. Such a description
leads to contradictions. It is shown that the transition to the Hilbert space
of almost periodic functions leads to the elimination of the detected
inconsistencies. Multiple signals and interference with discrete spectrum are
systems of sets. The properties of these systems lead to a new more effective
method to combat noise in this space. The method used to identify the
differential equations for the airbus. Baseline data were obtained during
automatic landing.
|
1111.3752
|
Single-User Beamforming in Large-Scale MISO Systems with Per-Antenna
Constant-Envelope Constraints: The Doughnut Channel
|
cs.IT math.IT
|
Large antenna arrays at the base station (BS) has recently been shown to
achieve remarkable intra-cell interference suppression at low complexity.
However, building large arrays in practice, would require the use of
power-efficient RF amplifiers, which generally have poor linearity
characteristics and hence would require the use of input signals with a very
small peak-to-average power ratio (PAPR). In this paper, we consider the
single-user Multiple-Input Single-Output (MISO) downlink channel for the case
where the BS antennas are constrained to transmit signals having constant
envelope (CE). We show that, with per-antenna CE transmission the effective
channel seen by the receiver is a SISO AWGN channel with its input constrained
to lie in a doughnut-shaped region. For single-path direct-line-of-sight (DLOS)
and general i.i.d. fading channels, analysis of the effective doughnut channel
shows that under a per-antenna CE input constraint, i) compared to an
average-only total transmit power constrained MISO channel, the extra total
transmit power required to achieve a desired information rate is small and
bounded, ii) with N base station antennas an O(N) array power gain is
achievable, and iii) for a desired information rate, using power-efficient
amplifiers with CE inputs would require significantly less total transmit power
when compared to using highly linear (power-inefficient) amplifiers with high
PAPR inputs.
|
1111.3784
|
Automatic Optimized Discovery, Creation and Processing of Astronomical
Catalogs
|
astro-ph.IM cs.DB
|
We present the design of a novel way of handling astronomical catalogs in
Astro-WISE in order to achieve the scalability required for the data produced
by large scale surveys. A high level of automation and abstraction is achieved
in order to facilitate interoperation with visualization software for
interactive exploration. At the same time flexibility in processing is enhanced
and data is shared implicitly between scientists.
This is accomplished by using a data model that primarily stores how catalogs
are derived; the contents of the catalogs are only created when necessary and
stored only when beneficial for performance. Discovery of existing catalogs and
creation of new catalogs is done through the same process by directly
requesting the final set of sources (astronomical objects) and attributes
(physical properties) that is required, for example from within visualization
software.
New catalogs are automatically created to provide attributes of sources for
which no suitable existing catalogs can be found. These catalogs are defined to
contain the new attributes on the largest set of sources the calculation of the
attributes is applicable to, facilitating reuse for future data requests.
Subsequently, only those parts of the catalogs that are required for the
requested end product are actually processed, ensuring scalability.
The presented mechanisms primarily determine which catalogs are created and
what data has to be processed and stored: the actual processing and storage
itself is left to existing functionality of the underlying information system.
|
1111.3805
|
Diversity of the MMSE receiver in flat fading and frequency selective
MIMO channels at fixed rate
|
cs.IT math.IT
|
In this contribution, the evaluation of the diversity of the MIMO MMSE
receiver is addressed for finite rates in both flat fading channels and
frequency selective fading channels with cyclic prefix. It has been observed
recently that in contrast with the other MIMO receivers, the MMSE receiver has
a diversity depending on the aimed finite rate, and that for sufficiently low
rates the MMSE receiver reaches the full diversity - that is, the diversity of
the ML receiver. This behavior has so far only been partially explained. The
purpose of this paper is to provide complete proofs for flat fading MIMO
channels, and to improve the partial existing results in frequency selective
MIMO channels with cyclic prefix.
|
1111.3818
|
Good Pairs of Adjacency Relations in Arbitrary Dimensions
|
cs.CV
|
In this text we show, that the notion of a "good pair" that was introduced in
the paper "Digital Manifolds and the Theorem of Jordan-Brouwer" has actually
known models. We will show, how to choose cubical adjacencies, the
generalizations of the well known 4- and 8-neighborhood to arbitrary
dimensions, in order to find good pairs. Furthermore, we give another proof for
the well known fact that the Khalimsky-topology implies good pairs. The outcome
is consistent with the known theory as presented by T.Y. Kong, A. Rosenfeld,
G.T. Herman and M. Khachan et.al and gives new insights in higher dimensions.
|
1111.3820
|
A Closed Form Expression for the Exact Bit Error Probability for Viterbi
Decoding of Convolutional Codes
|
cs.IT math.IT
|
In 1995, Best et al. published a formula for the exact bit error probability
for Viterbi decoding of the rate R=1/2, memory m=1 (2-state) convolutional
encoder with generator matrix G(D)=(1 1+D) when used to communicate over the
binary symmetric channel. Their formula was later extended to the rate R=1/2,
memory m=2 (4-state) convolutional encoder with generator matrix G(D)=(1+D^2
1+D+D^2) by Lentmaier et al.
In this paper, a different approach to derive the exact bit error probability
is described. A general recurrent matrix equation, connecting the average
information weight at the current and previous states of a trellis section of
the Viterbi decoder, is derived and solved. The general solution of this matrix
equation yields a closed form expression for the exact bit error probability.
As special cases, the expressions obtained by Best et al. for the 2-state
encoder and by Lentmaier et al. for a 4-state encoder are obtained. The closed
form expression derived in this paper is evaluated for various realizations of
encoders, including rate R=1/2 and R=2/3 encoders, of as many as 16 states.
Moreover, it is shown that it is straightforward to extend the approach to
communication over the quantized additive white Gaussian noise channel.
|
1111.3837
|
Necessary and sufficient condition for saturating the upper bound of
quantum discord
|
quant-ph cs.IT math.IT
|
We revisit the upper bound of quantum discord given by the von Neumann
entropy of the measured subsystem. Using the Koashi-Winter relation, we obtain
a trade-off between the amount of classical correlation and quantum discord in
the tripartite pure states. The difference between the quantum discord and its
upper bound is interpreted as a measure on the classical correlative capacity.
Further, we give the explicit characterization of the quantum states saturating
the upper bound of quantum discord, through the equality condition for the
Araki-Lieb inequality. We also demonstrate that the saturating of the upper
bound of quantum discord precludes any further correlation between the measured
subsystem and the environment.
|
1111.3846
|
No Free Lunch versus Occam's Razor in Supervised Learning
|
cs.LG cs.IT math.IT
|
The No Free Lunch theorems are often used to argue that domain specific
knowledge is required to design successful algorithms. We use algorithmic
information theory to argue the case for a universal bias allowing an algorithm
to succeed in all interesting problem domains. Additionally, we give a new
algorithm for off-line classification, inspired by Solomonoff induction, with
good performance on all structured problems under reasonable assumptions. This
includes a proof of the efficacy of the well-known heuristic of randomly
selecting training data in the hope of reducing misclassification rates.
|
1111.3854
|
(Non-)Equivalence of Universal Priors
|
cs.IT math.IT
|
Ray Solomonoff invented the notion of universal induction featuring an aptly
termed "universal" prior probability function over all possible computable
environments. The essential property of this prior was its ability to dominate
all other such priors. Later, Levin introduced another construction --- a
mixture of all possible priors or `universal mixture'. These priors are well
known to be equivalent up to multiplicative constants. Here, we seek to clarify
further the relationships between these three characterisations of a universal
prior (Solomonoff's, universal mixtures, and universally dominant priors). We
see that the the constructions of Solomonoff and Levin define an identical
class of priors, while the class of universally dominant priors is strictly
larger. We provide some characterisation of the discrepancy.
|
1111.3866
|
Sequential search based on kriging: convergence analysis of some
algorithms
|
math.ST cs.LG math.OC stat.TH
|
Let $\FF$ be a set of real-valued functions on a set $\XX$ and let $S:\FF \to
\GG$ be an arbitrary mapping. We consider the problem of making inference about
$S(f)$, with $f\in\FF$ unknown, from a finite set of pointwise evaluations of
$f$. We are mainly interested in the problems of approximation and
optimization. In this article, we make a brief review of results concerning
average error bounds of Bayesian search methods that use a random process prior
about $f$.
|
1111.3919
|
Recipe recommendation using ingredient networks
|
cs.SI physics.soc-ph
|
The recording and sharing of cooking recipes, a human activity dating back
thousands of years, naturally became an early and prominent social use of the
web. The resulting online recipe collections are repositories of ingredient
combinations and cooking methods whose large-scale and variety yield
interesting insights about both the fundamentals of cooking and user
preferences. At the level of an individual ingredient we measure whether it
tends to be essential or can be dropped or added, and whether its quantity can
be modified. We also construct two types of networks to capture the
relationships between ingredients. The complement network captures which
ingredients tend to co-occur frequently, and is composed of two large
communities: one savory, the other sweet. The substitute network, derived from
user-generated suggestions for modifications, can be decomposed into many
communities of functionally equivalent ingredients, and captures users'
preference for healthier variants of a recipe. Our experiments reveal that
recipe ratings can be well predicted with features derived from combinations of
ingredient networks and nutrition information.
|
1111.3925
|
A Low-Delay Low-Complexity EKF Design for Joint Channel and CFO
Estimation in Multi-User Cognitive Communications
|
cs.IT math.IT
|
Parameter estimation in cognitive communications can be formulated as a
multi-user estimation problem, which is solvable under maximum likelihood
solution but involves high computational complexity. This paper presents a
time-sharing and interference mitigation based EKF (Extended Kalman Filter)
design for joint CFO (carrier frequency offset) and channel estimation at
multiple cognitive users. The key objective is to realize low implementation
complexity by decomposing highdimensional parameters into multiple separate
low-dimensional estimation problems, which can be solved in a time-shared
manner via pipelining operation. We first present a basic EKF design that
estimates the parameters from one TX user to one RX antenna. Then such basic
design is time-shared and reused to estimate parameters from multiple TX users
to multiple RX antennas. Meanwhile, we use interference mitigation module to
cancel the co-channel interference at each RX sample. In addition, we further
propose adaptive noise variance tracking module to improve the estimation
performance. The proposed design enjoys low delay and low buffer size (because
of its online real-time processing), as well as low implementation complexity
(because of time-sharing and pipeling design). Its estimation performance is
verified to be close to Cramer-Rao bound.
|
1111.3934
|
Model-based Utility Functions
|
cs.AI
|
Orseau and Ring, as well as Dewey, have recently described problems,
including self-delusion, with the behavior of agents using various definitions
of utility functions. An agent's utility function is defined in terms of the
agent's history of interactions with its environment. This paper argues, via
two examples, that the behavior problems can be avoided by formulating the
utility function in two steps: 1) inferring a model of the environment from
interactions, and 2) computing utility as a function of the environment model.
Basing a utility function on a model that the agent must learn implies that the
utility function must initially be expressed in terms of specifications to be
matched to structures in the learned model. These specifications constitute
prior assumptions about the environment so this approach will not work with
arbitrary environments. But the approach should work for agents designed by
humans to act in the physical world. The paper also addresses the issue of
self-modifying agents and shows that if provided with the possibility to modify
their utility functions agents will not choose to do so, under some usual
assumptions.
|
1111.3966
|
Partial Decode-Forward Binning Schemes for the Causal Cognitive Relay
Channels
|
cs.IT math.IT
|
The causal cognitive relay channel (CRC) has two sender-receiver pairs, in
which the second sender obtains information from the first sender causally and
assists the transmission of both senders. In this paper, we study both the
full- and half-duplex modes. In each mode, we propose two new coding schemes
built successively upon one another to illustrate the impact of different
coding techniques. The first scheme called partial decode-forward binning
(PDF-binning) combines the ideas of partial decode-forward relaying and
Gelfand-Pinsker binning. The second scheme called Han-Kobayashi partial
decode-forward binning (HK-PDF-binning) combines PDF-binning with Han-Kobayashi
coding by further splitting rates and applying superposition coding,
conditional binning and relaxed joint decoding.
In both schemes, the second sender decodes a part of the message from the
first sender, then uses Gelfand-Pinsker binning technique to bin against the
decoded codeword, but in such a way that allows both state nullifying and
forwarding. For the Gaussian channels, this PDF-binning essentializes to a
correlation between the transmit signal and the binning state, which
encompasses the traditional dirty-paper-coding binning as a special case when
this correlation factor is zero. We also provide the closed-form optimal
binning parameter for each scheme.
The 2-phase half-duplex schemes are adapted from the full-duplex ones by
removing block Markov encoding, sending different message parts in different
phases and applying joint decoding across both phases. Analysis shows that the
HK-PDF-binning scheme in both modes encompasses the Han-Kobayashi rate region
and achieves both the partial decode-forward relaying rate for the first sender
and interference-free rate for the second sender. Furthermore, this scheme
outperforms all existing schemes.
|
1111.3969
|
The Object Projection Feature Estimation Problem in Unsupervised
Markerless 3D Motion Tracking
|
cs.CV cs.GR
|
3D motion tracking is a critical task in many computer vision applications.
Existing 3D motion tracking techniques require either a great amount of
knowledge on the target object or specific hardware. These requirements
discourage the wide spread of commercial applications based on 3D motion
tracking. 3D motion tracking systems that require no knowledge on the target
object and run on a single low-budget camera require estimations of the object
projection features (namely, area and position). In this paper, we define the
object projection feature estimation problem and we present a novel 3D motion
tracking system that needs no knowledge on the target object and that only
requires a single low-budget camera, as installed in most computers and
smartphones. Our system estimates, in real time, the three-dimensional position
of a non-modeled unmarked object that may be non-rigid, non-convex, partially
occluded, self occluded, or motion blurred, given that it is opaque, evenly
colored, and enough contrasting with the background in each frame. Our system
is also able to determine the most relevant object to track in the screen. Our
3D motion tracking system does not impose hard constraints, therefore it allows
a market-wide implementation of applications that use 3D motion tracking.
|
1111.4045
|
An Information-Theoretic Privacy Criterion for Query Forgery in
Information Retrieval
|
cs.IT cs.CR math.IT
|
In previous work, we presented a novel information-theoretic privacy
criterion for query forgery in the domain of information retrieval. Our
criterion measured privacy risk as a divergence between the user's and the
population's query distribution, and contemplated the entropy of the user's
distribution as a particular case. In this work, we make a twofold
contribution. First, we thoroughly interpret and justify the privacy metric
proposed in our previous work, elaborating on the intimate connection between
the celebrated method of entropy maximization and the use of entropies and
divergences as measures of privacy. Secondly, we attempt to bridge the gap
between the privacy and the information-theoretic communities by substantially
adapting some technicalities of our original work to reach a wider audience,
not intimately familiar with information theory and the method of types.
|
1111.4052
|
A Facial Expression Classification System Integrating Canny, Principal
Component Analysis and Artificial Neural Network
|
cs.CV
|
Facial Expression Classification is an interesting research problem in recent
years. There are a lot of methods to solve this problem. In this research, we
propose a novel approach using Canny, Principal Component Analysis (PCA) and
Artificial Neural Network. Firstly, in preprocessing phase, we use Canny for
local region detection of facial images. Then each of local region's features
will be presented based on Principal Component Analysis (PCA). Finally, using
Artificial Neural Network (ANN)applies for Facial Expression Classification. We
apply our proposal method (Canny_PCA_ANN) for recognition of six basic facial
expressions on JAFFE database consisting 213 images posed by 10 Japanese female
models. The experimental result shows the feasibility of our proposal method.
|
1111.4083
|
Unbiased Statistics of a CSP - A Controlled-Bias Generator
|
cs.AI
|
We show that estimating the complexity (mean and distribution) of the
instances of a fixed size Constraint Satisfaction Problem (CSP) can be very
hard. We deal with the main two aspects of the problem: defining a measure of
complexity and generating random unbiased instances. For the first problem, we
rely on a general framework and a measure of complexity we presented at
CISSE08. For the generation problem, we restrict our analysis to the Sudoku
example and we provide a solution that also explains why it is so difficult.
|
1111.4174
|
Universal Secure Multiplex Network Coding with Dependent and Non-Uniform
Messages
|
cs.IT cs.CR cs.NI math.IT
|
We consider the random linear precoder at the source node as a secure network
coding. We prove that it is strongly secure in the sense of Harada and Yamamoto
and universal secure in the sense of Silva and Kschischang, while allowing
arbitrary small but nonzero mutual information to the eavesdropper. Our
security proof allows statistically dependent and non-uniform multiple secret
messages, while all previous constructions of weakly or strongly secure network
coding assumed independent and uniform messages, which are difficult to be
ensured in practice.
|
1111.4181
|
Locating privileged spreaders on an Online Social Network
|
physics.soc-ph cs.SI
|
Social media have provided plentiful evidence of their capacity for
information diffusion. Fads and rumors, but also social unrest and riots travel
fast and affect large fractions of the population participating in online
social networks (OSNs). This has spurred much research regarding the mechanisms
that underlie social contagion, and also who (if any) can unleash system-wide
information dissemination. Access to real data, both regarding topology --the
network of friendships-- and dynamics --the actual way in which OSNs users
interact--, is crucial to decipher how the former facilitates the latter's
success, understood as efficiency in information spreading. With the
quantitative analysis that stems from complex network theory, we discuss who
(and why) has privileged spreading capabilities when it comes to information
diffusion. This is done considering the evolution of an episode of political
protest which took place in Spain, spanning one month in 2011.
|
1111.4232
|
A Model of Spatial Thinking for Computational Intelligence
|
cs.AI
|
Trying to be effective (no matter who exactly and in what field) a person
face the problem which inevitably destroys all our attempts to easily get to a
desired goal. The problem is the existence of some insuperable barriers for our
mind, anotherwords barriers for principles of thinking. They are our clue and
main reason for research. Here we investigate these barriers and their features
exposing the nature of mental process. We start from special structures which
reflect the ways to define relations between objects. Then we came to realizing
about what is the material our mind uses to build thoughts, to make
conclusions, to understand, to form reasoning, etc. This can be called a mental
dynamics. After this the nature of mental barriers on the required level of
abstraction as well as the ways to pass through them became clear. We begin to
understand why thinking flows in such a way, with such specifics and with such
limitations we can observe in reality. This can help us to be more optimal. At
the final step we start to understand, what ma-thematical models can be applied
to such a picture. We start to express our thoughts in a language of
mathematics, developing an apparatus for our Spatial Theory of Mind, suitable
to represent processes and infrastructure of thinking. We use abstract algebra
and stay invariant in relation to the nature of objects.
|
1111.4244
|
Efficient Capacity Computation and Power Optimization for Relay Networks
|
cs.IT math.IT
|
The capacity or approximations to capacity of various single-source
single-destination relay network models has been characterized in terms of the
cut-set upper bound. In principle, a direct computation of this bound requires
evaluating the cut capacity over exponentially many cuts. We show that the
minimum cut capacity of a relay network under some special assumptions can be
cast as a minimization of a submodular function, and as a result, can be
computed efficiently. We use this result to show that the capacity, or an
approximation to the capacity within a constant gap for the Gaussian, wireless
erasure, and Avestimehr-Diggavi-Tse deterministic relay network models can be
computed in polynomial time. We present some empirical results showing that
computing constant-gap approximations to the capacity of Gaussian relay
networks with around 300 nodes can be done in order of minutes.
For Gaussian networks, cut-set capacities are also functions of the powers
assigned to the nodes. We consider a family of power optimization problems and
show that they can be solved in polynomial time. In particular, we show that
the minimization of the sum of powers assigned to the nodes subject to a
minimum rate constraint (measured in terms of cut-set bounds) can be computed
in polynomial time. We propose an heuristic algorithm to solve this problem and
measure its performance through simulations on random Gaussian networks. We
observe that in the optimal allocations most of the power is assigned to a
small subset of relays, which suggests that network simplification may be
possible without excessive performance degradation.
|
1111.4246
|
The No-U-Turn Sampler: Adaptively Setting Path Lengths in Hamiltonian
Monte Carlo
|
stat.CO cs.LG
|
Hamiltonian Monte Carlo (HMC) is a Markov chain Monte Carlo (MCMC) algorithm
that avoids the random walk behavior and sensitivity to correlated parameters
that plague many MCMC methods by taking a series of steps informed by
first-order gradient information. These features allow it to converge to
high-dimensional target distributions much more quickly than simpler methods
such as random walk Metropolis or Gibbs sampling. However, HMC's performance is
highly sensitive to two user-specified parameters: a step size {\epsilon} and a
desired number of steps L. In particular, if L is too small then the algorithm
exhibits undesirable random walk behavior, while if L is too large the
algorithm wastes computation. We introduce the No-U-Turn Sampler (NUTS), an
extension to HMC that eliminates the need to set a number of steps L. NUTS uses
a recursive algorithm to build a set of likely candidate points that spans a
wide swath of the target distribution, stopping automatically when it starts to
double back and retrace its steps. Empirically, NUTS perform at least as
efficiently as and sometimes more efficiently than a well tuned standard HMC
method, without requiring user intervention or costly tuning runs. We also
derive a method for adapting the step size parameter {\epsilon} on the fly
based on primal-dual averaging. NUTS can thus be used with no hand-tuning at
all. NUTS is also suitable for applications such as BUGS-style automatic
inference engines that require efficient "turnkey" sampling algorithms.
|
1111.4267
|
Control Neuronal por Modelo Inverso de un Servosistema Usando Algoritmos
de Aprendizaje Levenberg-Marquardt y Bayesiano
|
cs.AI cs.CE
|
In this paper we present the experimental results of the neural network
control of a servo-system in order to control its speed. The control strategy
is implemented by using an inverse-model control based on Artificial Neural
Networks (ANNs). The network training was performed using two learning
algorithms: Levenberg-Marquardt and Bayesian regularization. We evaluate the
generalization capability for each method according to both the correct
operation of the controller to follow the reference signal, and the control
efforts developed by the ANN-based controller.
|
1111.4278
|
Counting solutions from finite samplings
|
cond-mat.stat-mech cond-mat.dis-nn cs.IT math.IT physics.bio-ph
|
We formulate the solution counting problem within the framework of inverse
Ising problem and use fast belief propagation equations to estimate the entropy
whose value provides an estimate on the true one. We test this idea on both
diluted models (random 2-SAT and 3-SAT problems) and fully-connected model
(binary perceptron), and show that when the constraint density is small, this
estimate can be very close to the true value. The information stored by the
salamander retina under the natural movie stimuli can also be estimated and our
result is consistent with that obtained by Monte Carlo method. Of particular
significance is sizes of other metastable states for this real neuronal network
are predicted.
|
1111.4289
|
Interfacial Numerical Dispersion and New Conformal FDTD Method
|
physics.comp-ph cs.CE cs.NA
|
This article shows the interfacial relation in electrodynamics shall be
corrected in discrete grid form which can be seen as certain numerical
dispersion beyond the usual bulk type. Furthermore we construct a lossy
conductor model to illustrate how to simulate more general materials other than
traditional PEC or simple dielectrics, by a new conformal FDTD method which
main considers the effects of penetrative depth and the distribution of free
bulk electric charge and current.
|
1111.4290
|
A Single Euler Number Feature for Multi-font Multi-size Kannada Numeral
Recognition
|
cs.CV
|
In this paper a novel approach is proposed based on single Euler number
feature which is free from thinning and size normalization for multi-font and
multi-size Kannada numeral recognition system. A nearest neighbor
classification is used for classification of Kannada numerals by considering
the Euclidian distance. A total 1500 numeral images with different font sizes
between (10..84) are tested for algorithm efficiency and the overall the
classification accuracy is found to be 99.00% .The said method is thinning
free, fast, and showed encouraging results on varying font styles and sizes of
Kannada numerals.
|
1111.4291
|
Multi-font Multi-size Kannada Numeral Recognition Based on Structural
Features
|
cs.CV
|
In this paper a fast and novel method is proposed for multi-font multi-size
Kannada numeral recognition which is thinning free and without size
normalization approach. The different structural feature are used for numeral
recognition namely, directional density of pixels in four directions, water
reservoirs, maximum profile distances, and fill hole density are used for the
recognition of Kannada numerals. A Euclidian minimum distance criterion is used
to find minimum distances and K-nearest neighbor classifier is used to classify
the Kannada numerals by varying the size of numeral image from 16 to 50 font
sizes for the 20 different font styles from NUDI and BARAHA popular word
processing Kannada software. The total 1150 numeral images are tested and the
overall accuracy of classification is found to be 100%. The average time taken
by this method is 0.1476 seconds.
|
1111.4297
|
Battling the Internet Water Army: Detection of Hidden Paid Posters
|
cs.SI
|
We initiate a systematic study to help distinguish a special group of online
users, called hidden paid posters, or termed "Internet water army" in China,
from the legitimate ones. On the Internet, the paid posters represent a new
type of online job opportunity. They get paid for posting comments and new
threads or articles on different online communities and websites for some
hidden purposes, e.g., to influence the opinion of other people towards certain
social events or business markets. Though an interesting strategy in business
marketing, paid posters may create a significant negative effect on the online
communities, since the information from paid posters is usually not
trustworthy. When two competitive companies hire paid posters to post fake news
or negative comments about each other, normal online users may feel overwhelmed
and find it difficult to put any trust in the information they acquire from the
Internet. In this paper, we thoroughly investigate the behavioral pattern of
online paid posters based on real-world trace data. We design and validate a
new detection mechanism, using both non-semantic analysis and semantic
analysis, to identify potential online paid posters. Our test results with
real-world datasets show a very promising performance.
|
1111.4316
|
Semantic Navigation on the Web of Data: Specification of Routes, Web
Fragments and Actions
|
cs.NI cs.CL
|
The massive semantic data sources linked in the Web of Data give new meaning
to old features like navigation; introduce new challenges like semantic
specification of Web fragments; and make it possible to specify actions relying
on semantic data. In this paper we introduce a declarative language to face
these challenges. Based on navigational features, it is designed to specify
fragments of the Web of Data and actions to be performed based on these data.
We implement it in a centralized fashion, and show its power and performance.
Finally, we explore the same ideas in a distributed setting, showing their
feasibility, potentialities and challenges.
|
1111.4339
|
Kolmogorov complexity and computably enumerable sets
|
math.LO cs.IT math.IT
|
We study the computably enumerable sets in terms of the: (a) Kolmogorov
complexity of their initial segments; (b) Kolmogorov complexity of finite
programs when they are used as oracles. We present an extended discussion of
the existing research on this topic, along with recent developments and open
problems. Besides this survey, our main original result is the following
characterization of the computably enumerable sets with trivial initial segment
prefix-free complexity. A computably enumerable set $A$ is $K$-trivial if and
only if the family of sets with complexity bounded by the complexity of $A$ is
uniformly computable from the halting problem.
|
1111.4343
|
Question Answering in a Natural Language Understanding System Based on
Object-Oriented Semantics
|
cs.CL
|
Algorithms of question answering in a computer system oriented on input and
logical processing of text information are presented. A knowledge domain under
consideration is social behavior of a person. A database of the system includes
an internal representation of natural language sentences and supplemental
information. The answer {\it Yes} or {\it No} is formed for a general question.
A special question containing an interrogative word or group of interrogative
words permits to find a subject, object, place, time, cause, purpose and way of
action or event. Answer generation is based on identification algorithms of
persons, organizations, machines, things, places, and times. Proposed
algorithms of question answering can be realized in information systems closely
connected with text processing (criminology, operation of business, medicine,
document systems).
|
1111.4345
|
Compressed Sensing with General Frames via Optimal-dual-based
$\ell_1$-analysis
|
cs.IT math.IT
|
Compressed sensing with sparse frame representations is seen to have much
greater range of practical applications than that with orthonormal bases. In
such settings, one approach to recover the signal is known as
$\ell_1$-analysis. We expand in this article the performance analysis of this
approach by providing a weaker recovery condition than existing results in the
literature. Our analysis is also broadly based on general frames and
alternative dual frames (as analysis operators). As one application to such a
general-dual-based approach and performance analysis, an optimal-dual-based
technique is proposed to demonstrate the effectiveness of using alternative
dual frames as analysis operators. An iterative algorithm is outlined for
solving the optimal-dual-based $\ell_1$-analysis problem. The effectiveness of
the proposed method and algorithm is demonstrated through several experiments.
|
1111.4350
|
Incentive Mechanisms for Hierarchical Spectrum Markets
|
cs.NI cs.GT cs.SY
|
In this paper, we study spectrum allocation mechanisms in hierarchical
multi-layer markets which are expected to proliferate in the near future based
on the current spectrum policy reform proposals. We consider a setting where a
state agency sells spectrum channels to Primary Operators (POs) who
subsequently resell them to Secondary Operators (SOs) through auctions. We show
that these hierarchical markets do not result in a socially efficient spectrum
allocation which is aimed by the agency, due to lack of coordination among the
entities in different layers and the inherently selfish revenue-maximizing
strategy of POs. In order to reconcile these opposing objectives, we propose an
incentive mechanism which aligns the strategy and the actions of the POs with
the objective of the agency, and thus leads to system performance improvement
in terms of social welfare. This pricing-based scheme constitutes a method for
hierarchical market regulation. A basic component of the proposed incentive
mechanism is a novel auction scheme which enables POs to allocate their
spectrum by balancing their derived revenue and the welfare of the SOs.
|
1111.4362
|
Hardware Implementation of Successive Cancellation Decoders for Polar
Codes
|
cs.AR cs.IT math.IT
|
The recently-discovered polar codes are seen as a major breakthrough in
coding theory; they provably achieve the theoretical capacity of discrete
memoryless channels using the low complexity successive cancellation (SC)
decoding algorithm. Motivated by recent developments in polar coding theory, we
propose a family of efficient hardware implementations for SC polar decoders.
We show that such decoders can be implemented with O(n) processing elements,
O(n) memory elements, and can provide a constant throughput for a given target
clock frequency. Furthermore, we show that SC decoding can be implemented in
the logarithm domain, thereby eliminating costly multiplication and division
operations and reducing the complexity of each processing element greatly. We
also present a detailed architecture for an SC decoder and provide logic
synthesis results confirming the linear growth in complexity of the decoder as
the code length increases.
|
1111.4460
|
Parametrized Stochastic Multi-armed Bandits with Binary Rewards
|
cs.LG
|
In this paper, we consider the problem of multi-armed bandits with a large,
possibly infinite number of correlated arms. We assume that the arms have
Bernoulli distributed rewards, independent across time, where the probabilities
of success are parametrized by known attribute vectors for each arm, as well as
an unknown preference vector, each of dimension $n$. For this model, we seek an
algorithm with a total regret that is sub-linear in time and independent of the
number of arms. We present such an algorithm, which we call the Two-Phase
Algorithm, and analyze its performance. We show upper bounds on the total
regret which applies uniformly in time, for both the finite and infinite arm
cases. The asymptotics of the finite arm bound show that for any $f \in
\omega(\log(T))$, the total regret can be made to be $O(n \cdot f(T))$. In the
infinite arm case, the total regret is $O(\sqrt{n^3 T})$.
|
1111.4470
|
Efficient Regression in Metric Spaces via Approximate Lipschitz
Extension
|
cs.LG
|
We present a framework for performing efficient regression in general metric
spaces. Roughly speaking, our regressor predicts the value at a new point by
computing a Lipschitz extension --- the smoothest function consistent with the
observed data --- after performing structural risk minimization to avoid
overfitting. We obtain finite-sample risk bounds with minimal structural and
noise assumptions, and a natural speed-precision tradeoff. The offline
(learning) and online (prediction) stages can be solved by convex programming,
but this naive approach has runtime complexity $O(n^3)$, which is prohibitive
for large datasets. We design instead a regression algorithm whose speed and
generalization performance depend on the intrinsic dimension of the data, to
which the algorithm adapts. While our main innovation is algorithmic, the
statistical results may also be of independent interest.
|
1111.4500
|
Equivalence of History and Generator Epsilon-Machines
|
math.PR cond-mat.stat-mech cs.IT math.IT nlin.CD stat.ML
|
Epsilon-machines are minimal, unifilar presentations of stationary stochastic
processes. They were originally defined in the history machine sense, as hidden
Markov models whose states are the equivalence classes of infinite pasts with
the same probability distribution over futures. In analyzing synchronization,
though, an alternative generator definition was given: unifilar, edge-emitting
hidden Markov models with probabilistically distinct states. The key difference
is that history epsilon-machines are defined by a process, whereas generator
epsilon-machines define a process. We show here that these two definitions are
equivalent in the finite-state case.
|
1111.4503
|
The Anatomy of the Facebook Social Graph
|
cs.SI physics.soc-ph
|
We study the structure of the social graph of active Facebook users, the
largest social network ever analyzed. We compute numerous features of the graph
including the number of users and friendships, the degree distribution, path
lengths, clustering, and mixing patterns. Our results center around three main
observations. First, we characterize the global structure of the graph,
determining that the social network is nearly fully connected, with 99.91% of
individuals belonging to a single large connected component, and we confirm the
"six degrees of separation" phenomenon on a global scale. Second, by studying
the average local clustering coefficient and degeneracy of graph neighborhoods,
we show that while the Facebook graph as a whole is clearly sparse, the graph
neighborhoods of users contain surprisingly dense structure. Third, we
characterize the assortativity patterns present in the graph by studying the
basic demographic and network properties of users. We observe clear degree
assortativity and characterize the extent to which "your friends have more
friends than you". Furthermore, we observe a strong effect of age on friendship
preferences as well as a globally modular community structure driven by
nationality, but we do not find any strong gender homophily. We compare our
results with those from smaller social networks and find mostly, but not
entirely, agreement on common structural network characteristics.
|
1111.4533
|
In-Network Redundancy Generation for Opportunistic Speedup of Backup
|
cs.DC cs.IT cs.NI math.IT
|
Erasure coding is a storage-efficient alternative to replication for
achieving reliable data backup in distributed storage systems. During the
storage process, traditional erasure codes require a unique source node to
create and upload all the redundant data to the different storage nodes.
However, such a source node may have limited communication and computation
capabilities, which constrain the storage process throughput. Moreover, the
source node and the different storage nodes might not be able to send and
receive data simultaneously -- e.g., nodes might be busy in a datacenter
setting, or simply be offline in a peer-to-peer setting -- which can further
threaten the efficacy of the overall storage process. In this paper we propose
an "in-network" redundancy generation process which distributes the data
insertion load among the source and storage nodes by allowing the storage nodes
to generate new redundant data by exchanging partial information among
themselves, improving the throughput of the storage process. The process is
carried out asynchronously, utilizing spare bandwidth and computing resources
from the storage nodes. The proposed approach leverages on the local
repairability property of newly proposed erasure codes tailor made for the
needs of distributed storage systems. We analytically show that the performance
of this technique relies on an efficient usage of the spare node resources, and
we derive a set of scheduling algorithms to maximize the same. We
experimentally show, using availability traces from real peer-to-peer
applications as well as Google data center availability and workload traces,
that our algorithms can, depending on the environment characteristics, increase
the throughput of the storage process significantly (up to 90% in data centers,
and 60% in peer-to-peer settings) with respect to the classical naive data
insertion approach.
|
1111.4541
|
Large Scale Spectral Clustering Using Approximate Commute Time Embedding
|
cs.LG
|
Spectral clustering is a novel clustering method which can detect complex
shapes of data clusters. However, it requires the eigen decomposition of the
graph Laplacian matrix, which is proportion to $O(n^3)$ and thus is not
suitable for large scale systems. Recently, many methods have been proposed to
accelerate the computational time of spectral clustering. These approximate
methods usually involve sampling techniques by which a lot information of the
original data may be lost. In this work, we propose a fast and accurate
spectral clustering approach using an approximate commute time embedding, which
is similar to the spectral embedding. The method does not require using any
sampling technique and computing any eigenvector at all. Instead it uses random
projection and a linear time solver to find the approximate embedding. The
experiments in several synthetic and real datasets show that the proposed
approach has better clustering quality and is faster than the state-of-the-art
approximate spectral clustering methods.
|
1111.4555
|
Large Deviations Performance of Consensus+Innovations Distributed
Detection with Non-Gaussian Observations
|
cs.IT math.IT
|
We establish the large deviations asymptotic performance (error exponent) of
consensus+innovations distributed detection over random networks with generic
(non-Gaussian) sensor observations. At each time instant, sensors 1) combine
theirs with the decision variables of their neighbors (consensus) and 2)
assimilate their new observations (innovations). This paper shows for general
non-Gaussian distributions that consensus+innovations distributed detection
exhibits a phase transition behavior with respect to the network degree of
connectivity. Above a threshold, distributed is as good as centralized, with
the same optimal asymptotic detection performance, but, below the threshold,
distributed detection is suboptimal with respect to centralized detection. We
determine this threshold and quantify the performance loss below threshold.
Finally, we show the dependence of the threshold and performance on the
distribution of the observations: distributed detectors over the same random
network, but with different observations' distributions, for example, Gaussian,
Laplace, or quantized, may have different asymptotic performance, even when the
corresponding centralized detectors have the same asymptotic performance.
|
1111.4570
|
Four Degrees of Separation
|
cs.SI physics.soc-ph
|
Frigyes Karinthy, in his 1929 short story "L\'aancszemek" ("Chains")
suggested that any two persons are distanced by at most six friendship links.
(The exact wording of the story is slightly ambiguous: "He bet us that, using
no more than five individuals, one of whom is a personal acquaintance, he could
contact the selected individual [...]". It is not completely clear whether the
selected individual is part of the five, so this could actually allude to
distance five or six in the language of graph theory, but the "six degrees of
separation" phrase stuck after John Guare's 1990 eponymous play. Following
Milgram's definition and Guare's interpretation, we will assume that "degrees
of separation" is the same as "distance minus one", where "distance" is the
usual path length-the number of arcs in the path.) Stanley Milgram in his
famous experiment challenged people to route postcards to a fixed recipient by
passing them only through direct acquaintances. The average number of
intermediaries on the path of the postcards lay between 4.4 and 5.7, depending
on the sample of people chosen.
We report the results of the first world-scale social-network graph-distance
computations, using the entire Facebook network of active users (\approx721
million users, \approx69 billion friendship links). The average distance we
observe is 4.74, corresponding to 3.74 intermediaries or "degrees of
separation", showing that the world is even smaller than we expected, and
prompting the title of this paper. More generally, we study the distance
distribution of Facebook and of some interesting geographic subgraphs, looking
also at their evolution over time.
The networks we are able to explore are almost two orders of magnitude larger
than those analysed in the previous literature. We report detailed statistical
metadata showing that our measurements (which rely on probabilistic algorithms)
are very accurate.
|
1111.4572
|
On the mean square error of randomized averaging algorithms
|
math.OC cs.SI cs.SY
|
This paper regards randomized discrete-time consensus systems that preserve
the average "on average". As a main result, we provide an upper bound on the
mean square deviation of the consensus value from the initial average. Then, we
apply our result to systems where few or weakly correlated interactions take
place: these assumptions cover several algorithms proposed in the literature.
For such systems we show that, when the network size grows, the deviation tends
to zero, and the speed of this decay is not slower than the inverse of the
size. Our results are based on a new approach, which is unrelated to the
convergence properties of the system.
|
1111.4575
|
Information Theoretic Exemplification of the Impact of
Transmitter-Receiver Cognition on the Channel Capacity
|
cs.IT math.IT
|
In this paper, we study, information theoretically, the impact of transmitter
and or receiver cognition on the channel capacity. The cognition can be
described by state information, dependent on the channel noise and or input.
Specifically, as a new idea, we consider the receiver cognition as a state
information dependent on the noise and we derive a capacity theorem based on
the Gaussian version of the Cover-Chiang capacity theorem for two-sided state
information channel. As intuitively expected, the receiver cognition increases
the channel capacity and our theorem shows this increase quantitatively. Also,
our capacity theorem includes the famous Costa theorem as its special cases.
|
1111.4580
|
Networked estimation under information constraints
|
cs.IT cs.MA cs.SI math.IT
|
In this paper, we study estimation of potentially unstable linear dynamical
systems when the observations are distributed over a network. We are interested
in scenarios when the information exchange among the agents is restricted. In
particular, we consider that each agent can exchange information with its
neighbors only once per dynamical system evolution-step. Existing work with
similar information-constraints is restricted to static parameter estimation,
whereas, the work on dynamical systems assumes large number of information
exchange iterations between every two consecutive system evolution steps.
We show that when the agent communication network is sparely-connected, the
sparsity of the network plays a key role in the stability and performance of
the underlying estimation algorithm. To this end, we introduce the notion of
\emph{Network Tracing Capacity} (NTC), which is defined as the largest two-norm
of the system matrix that can be estimated with bounded error. Extending this
to fully-connected networks or infinite information exchanges (per dynamical
system evolution-step), we note that the NTC is infinite, i.e., any dynamical
system can be estimated with bounded error. In short, the NTC characterizes the
estimation capability of a sparse network by relating it to the evolution of
the underlying dynamical system.
|
1111.4596
|
Grassmannian Differential Limited Feedback for Interference Alignment
|
cs.IT math.IT
|
Channel state information (CSI) in the interference channel can be used to
precode, align, and reduce the dimension of interference at the receivers, to
achieve the channel's maximum multiplexing gain, through what is known as
interference alignment. Most interference alignment algorithms require
knowledge of all the interfering channels to compute the alignment precoders.
CSI, considered available at the receivers, can be shared with the transmitters
via limited feedback. When alignment is done by coding over frequency
extensions in a single antenna system, the required CSI lies on the
Grassmannian manifold and its structure can be exploited in feedback.
Unfortunately, the number of channels to be shared grows with the square of the
number of users, creating too much overhead with conventional feedback methods.
This paper proposes Grassmannian differential feedback to reduce feedback
overhead by exploiting both the channel's temporal correlation and Grassmannian
structure. The performance of the proposed algorithm is characterized both
analytically and numerically as a function of channel length, mobility, and the
number of feedback bits. The main conclusions are that the proposed feedback
strategy allows interference alignment to perform well over a wide range of
Doppler spreads, and to approach perfect CSI performance in slowly varying
channels. Numerical results highlight the trade-off between the frequency of
feedback and the accuracy of individual feedback updates.
|
1111.4610
|
A wildland fire modeling and visualization environment
|
physics.ao-ph cs.CE
|
We present an overview of a modeling environment, consisting of a coupled
atmosphere-wildfire model, utilities for visualization, data processing, and
diagnostics, open source software repositories, and a community wiki. The fire
model, called SFIRE, is based on a fire-spread model, implemented by the
level-set method, and it is coupled with the Weather Research Forecasting (WRF)
model. A version with a subset of the features is distributed with WRF 3.3 as
WRF-Fire. In each time step, the fire module takes the wind as input and
returns the latent and sensible heat fluxes. The software architecture uses WRF
parallel infrastructure for massively parallel computing. Recent features of
the code include interpolation from an ideal logarithmic wind profile for
nonhomogeneous fuels and ignition from a fire perimeter with an atmosphere and
fire spin-up. Real runs use online sources for fuel maps, fine-scale
topography, and meteorological data, and can run faster than real time.
Visualization pathways allow generating images and animations in many packages,
including VisTrails, VAPOR, MayaVi, and Paraview, as well as output to Google
Earth. The environment is available from openwfm.org. New diagnostic variables
were added to the code recently, including a new kind of fireline intensity,
which takes into account also the speed of burning, unlike Byram's fireline
intensity.
|
1111.4619
|
Redundant Wavelets on Graphs and High Dimensional Data Clouds
|
cs.CV
|
In this paper, we propose a new redundant wavelet transform applicable to
scalar functions defined on high dimensional coordinates, weighted graphs and
networks. The proposed transform utilizes the distances between the given data
points. We modify the filter-bank decomposition scheme of the redundant wavelet
transform by adding in each decomposition level linear operators that reorder
the approximation coefficients. These reordering operators are derived by
organizing the tree-node features so as to shorten the path that passes through
these points. We explore the use of the proposed transform to image denoising,
and show that it achieves denoising results that are close to those obtained
with the BM3D algorithm.
|
1111.4626
|
On an Achievable Rate of Large Rayleigh Block-Fading MIMO Channels with
No CSI
|
cs.IT math.IT
|
Training-based transmission over Rayleigh block-fading multiple-input
multiple-output (MIMO) channels is investigated. As a training method a
combination of a pilot-assisted scheme and a biased signaling scheme is
considered. The achievable rates of successive decoding (SD) receivers based on
the linear minimum mean-squared error (LMMSE) channel estimation are analyzed
in the large-system limit, by using the replica method under the assumption of
replica symmetry. It is shown that negligible pilot information is best in
terms of the achievable rates of the SD receivers in the large-system limit.
The obtained analytical formulas of the achievable rates can improve the
existing lower bound on the capacity of the MIMO channel with no channel state
information (CSI), derived by Hassibi and Hochwald, for all signal-to-noise
ratios (SNRs). The comparison between the obtained bound and a high SNR
approximation of the channel capacity, derived by Zheng and Tse, implies that
the high SNR approximation is unreliable unless quite high SNR is considered.
Energy efficiency in the low SNR regime is also investigated in terms of the
power per information bit required for reliable communication. The required
minimum power is shown to be achieved at a positive rate for the SD receiver
with no CSI, whereas it is achieved in the zero-rate limit for the case of
perfect CSI available at the receiver. Moreover, numerical simulations imply
that the presented large-system analysis can provide a good approximation for
not so large systems. The results in this paper imply that SD schemes can
provide a significant performance gain in the low-to-moderate SNR regimes,
compared to conventional receivers based on one-shot channel estimation.
|
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