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0811.4200
|
Two Models for Noisy Feedback in MIMO Channels
|
cs.IT math.IT
|
Two distinct models of feedback, suited for FDD (Frequency Division Duplex)
and TDD (Frequency Division Duplex) systems respectively, have been widely
studied in the literature. In this paper, we compare these two models of
feedback in terms of the diversity multiplexing tradeoff for varying amount of
channel state information at the terminals. We find that, when all
imperfections are accounted for, the maximum achievable diversity order in FDD
systems matches the diversity order in TDD systems. TDD systems achieve better
diversity order at higher multiplexing gains. In FDD systems, the maximum
diversity order can be achieved with just a single bit of feedback. Additional
bits of feedback (perfect or imperfect) do not affect the diversity order if
the receiver does not know the channel state information.
|
0811.4227
|
Entanglement-assisted communication of classical and quantum information
|
quant-ph cs.IT math.IT
|
We consider the problem of transmitting classical and quantum information
reliably over an entanglement-assisted quantum channel. Our main result is a
capacity theorem that gives a three-dimensional achievable rate region. Points
in the region are rate triples, consisting of the classical communication rate,
the quantum communication rate, and the entanglement consumption rate of a
particular coding scheme. The crucial protocol in achieving the boundary points
of the capacity region is a protocol that we name the classically-enhanced
father protocol. The classically-enhanced father protocol is more general than
other protocols in the family tree of quantum Shannon theoretic protocols, in
the sense that several previously known quantum protocols are now child
protocols of it. The classically-enhanced father protocol also shows an
improvement over a time-sharing strategy for the case of a qubit dephasing
channel--this result justifies the need for simultaneous coding of classical
and quantum information over an entanglement-assisted quantum channel. Our
capacity theorem is of a multi-letter nature (requiring a limit over many uses
of the channel), but it reduces to a single-letter characterization for at
least three channels: the completely depolarizing channel, the quantum erasure
channel, and the qubit dephasing channel.
|
0811.4339
|
Finite Lattice-Size Effects in MIMO Detection
|
cs.IT math.IT
|
Many powerful data detection algorithms employed in multiple-input
multiple-output (MIMO) communication systems, such as sphere decoding (SD) and
lattice-reduction (LR)-aided detection, were initially designed for infinite
lattices. Detection in MIMO systems is, however, based on finite lattices. In
this paper, we systematically study the consequences of finite lattice-size for
the performance and complexity of MIMO detection algorithms formulated for
infinite lattices. Specifically, we find, considering performance and
complexity, that LR does not seem to offer advantages when used in conjunction
with SD.
|
0811.4346
|
Dynamic Indexability: The Query-Update Tradeoff for One-Dimensional
Range Queries
|
cs.DS cs.DB
|
The B-tree is a fundamental secondary index structure that is widely used for
answering one-dimensional range reporting queries. Given a set of $N$ keys, a
range query can be answered in $O(\log_B \nm + \frac{K}{B})$ I/Os, where $B$ is
the disk block size, $K$ the output size, and $M$ the size of the main memory
buffer. When keys are inserted or deleted, the B-tree is updated in $O(\log_B
N)$ I/Os, if we require the resulting changes to be committed to disk right
away. Otherwise, the memory buffer can be used to buffer the recent updates,
and changes can be written to disk in batches, which significantly lowers the
amortized update cost. A systematic way of batching up updates is to use the
logarithmic method, combined with fractional cascading, resulting in a dynamic
B-tree that supports insertions in $O(\frac{1}{B}\log\nm)$ I/Os and queries in
$O(\log\nm + \frac{K}{B})$ I/Os. Such bounds have also been matched by several
known dynamic B-tree variants in the database literature.
In this paper, we prove that for any dynamic one-dimensional range query
index structure with query cost $O(q+\frac{K}{B})$ and amortized insertion cost
$O(u/B)$, the tradeoff $q\cdot \log(u/q) = \Omega(\log B)$ must hold if
$q=O(\log B)$. For most reasonable values of the parameters, we have $\nm =
B^{O(1)}$, in which case our query-insertion tradeoff implies that the bounds
mentioned above are already optimal. Our lower bounds hold in a dynamic version
of the {\em indexability model}, which is of independent interests.
|
0811.4349
|
Anti Plagiarism Application with Algorithm Karp-Rabin at Thesis in
Gunadarma University
|
cs.IT cs.DL math.IT
|
Plagiarism that is plagiarizing or composition retrieval, opinion, etcetera
from other people and makes it is likely composition and opinion him-self.
Plagiarism can be considered to be crime because stealing others copyrights.
Like action a student copying some part of writings without valid permission
from the original writer. In education world, plagiarism perpetrator can get
the devil to pay from school/university. Plagiarism perpetrator conceived of
plagiator. This thing is possible unable to be paid attention by the side of
campus because of limitation from some interconnected factors for example
student amounts Gunadarma University reaching thousands and incommensurate to
tester amounts or lecturer the side of campus in charge directs problem thesis.
In this paper, an application have been developed in order to check and look
for 5 type percentage similarity from a thesis with other one at certain part
or chapters. Percentage got that is 0%, under 15%, between 15-50%, up to 50%
and 100%. So it should be expected that the results could be used by thesis
advisor and also thesis examiner from the Student at Gunadarma University.
|
0811.4354
|
Soft-Input Soft-Output Sphere Decoding
|
cs.IT math.IT
|
Soft-input soft-output (SISO) detection algorithms form the basis for
iterative decoding. The associated computational complexity often poses
significant challenges for practical receiver implementations, in particular in
the context of multiple-input multiple-output wireless systems. In this paper,
we present a low-complexity SISO sphere decoder which is based on the single
tree search paradigm, proposed originally for soft-output detection in Studer
et al., IEEE J-SAC, 2008. The algorithm incorporates clipping of the extrinsic
log-likelihood ratios in the tree search, which not only results in significant
complexity savings, but also allows to cover a large performance/complexity
trade-off region by adjusting a single parameter.
|
0811.4391
|
Cross-Layer Link Adaptation Design for Relay Channels with Cooperative
ARQ Protocol
|
cs.IT math.IT
|
The cooperative automatic repeat request (C-ARQ) is a link layer relaying
protocol which exploits the spatial diversity and allows the relay node to
retransmit the source data packet to the destination, when the latter is unable
to decode the source data correctly. This paper presents a cross-layer link
adaptation design for C-ARQ based relay channels in which both source and relay
nodes employ adaptive modulation coding and power adaptation at the physical
layer. For this scenario, we first derive closed-form expressions for the
system spectral efficiency and average power consumption. We then present a low
complexity iterative algorithm to find the optimized adaptation solution by
maximizing the spectral efficiency subject to a packet loss rate (PLR) and an
average power consumption constraint. The results indicate that the proposed
adaptation scheme enhances the spectral efficiency noticeably when compared to
other adaptive schemes, while guaranteeing the required PLR performance.
|
0811.4395
|
List Decoding Tensor Products and Interleaved Codes
|
cs.IT math.IT
|
We design the first efficient algorithms and prove new combinatorial bounds
for list decoding tensor products of codes and interleaved codes. We show that
for {\em every} code, the ratio of its list decoding radius to its minimum
distance stays unchanged under the tensor product operation (rather than
squaring, as one might expect). This gives the first efficient list decoders
and new combinatorial bounds for some natural codes including multivariate
polynomials where the degree in each variable is bounded. We show that for {\em
every} code, its list decoding radius remains unchanged under $m$-wise
interleaving for an integer $m$. This generalizes a recent result of Dinur et
al \cite{DGKS}, who proved such a result for interleaved Hadamard codes
(equivalently, linear transformations). Using the notion of generalized Hamming
weights, we give better list size bounds for {\em both} tensoring and
interleaving of binary linear codes. By analyzing the weight distribution of
these codes, we reduce the task of bounding the list size to bounding the
number of close-by low-rank codewords. For decoding linear transformations,
using rank-reduction together with other ideas, we obtain list size bounds that
are tight over small fields.
|
0811.4397
|
Joint Adaptive Modulation-Coding and Cooperative ARQ for Wireless Relay
Networks
|
cs.IT math.IT
|
This paper presents a cross-layer approach to jointly design adaptive
modulation and coding (AMC) at the physical layer and cooperative truncated
automatic repeat request (ARQ) protocol at the data link layer. We first derive
an exact closed form expression for the spectral efficiency of the proposed
joint AMC-cooperative ARQ scheme. Aiming at maximizing this system performance
measure, we then optimize an AMC scheme which directly satisfies a prescribed
packet loss rate constraint at the data-link layer. The results indicate that
utilizing cooperative ARQ as a retransmission strategy, noticeably enhances the
spectral efficiency compared with the system that employs AMC alone at the
physical layer. Moreover, the proposed adaptive rate cooperative ARQ scheme
outperforms the fixed rate counterpart when the transmission modes at the
source and relay are chosen based on the channel statistics. This in turn
quantifies the possible gain achieved by joint design of AMC and ARQ in
wireless relay networks.
|
0811.4403
|
Joint Adaptive Modulation Coding and Cooperative ARQ over Relay
Channels-Applications to Land Mobile Satellite Communications
|
cs.IT math.IT
|
In a cooperative relay network, a relay node (R) facilitates data
transmission to the destination node (D), when the latter is unable to decode
the source node (S) data correctly. This paper considers such a system model
and presents a cross-layer approach to jointly design adaptive modulation and
coding (AMC) at the physical layer and cooperative truncated automatic repeat
request (ARQ) protocol at the data link layer. We first derive a closed form
expression for the spectral efficiency of the joint cooperative ARQ-AMC scheme.
Aiming at maximizing this performance measure, we then optimize two AMC schemes
for S-D and R-D links, which directly satisfy a prescribed packet loss rate
constraint. As an interesting application, we also consider the problem of
joint link adaptation and blockage mitigation in land mobile satellite
communications (LMSC). We also present a new relay-assisted transmission
protocol for LMSC, which delivers the source data to the destination via the
relaying link, when the S-D channel is in outage. Numerical results indicate
that the proposed schemes noticeably enhances the spectral efficiency compared
to a system, which uses a conventional ARQ-AMC scheme at the S-D link, or a
system which employs an optimized fixed rate cooperative-ARQ protocol.
|
0811.4413
|
A Spectral Algorithm for Learning Hidden Markov Models
|
cs.LG cs.AI
|
Hidden Markov Models (HMMs) are one of the most fundamental and widely used
statistical tools for modeling discrete time series. In general, learning HMMs
from data is computationally hard (under cryptographic assumptions), and
practitioners typically resort to search heuristics which suffer from the usual
local optima issues. We prove that under a natural separation condition (bounds
on the smallest singular value of the HMM parameters), there is an efficient
and provably correct algorithm for learning HMMs. The sample complexity of the
algorithm does not explicitly depend on the number of distinct (discrete)
observations---it implicitly depends on this quantity through spectral
properties of the underlying HMM. This makes the algorithm particularly
applicable to settings with a large number of observations, such as those in
natural language processing where the space of observation is sometimes the
words in a language. The algorithm is also simple, employing only a singular
value decomposition and matrix multiplications.
|
0811.4458
|
Learning Class-Level Bayes Nets for Relational Data
|
cs.LG cs.AI
|
Many databases store data in relational format, with different types of
entities and information about links between the entities. The field of
statistical-relational learning (SRL) has developed a number of new statistical
models for such data. In this paper we focus on learning class-level or
first-order dependencies, which model the general database statistics over
attributes of linked objects and links (e.g., the percentage of A grades given
in computer science classes). Class-level statistical relationships are
important in themselves, and they support applications like policy making,
strategic planning, and query optimization. Most current SRL methods find
class-level dependencies, but their main task is to support instance-level
predictions about the attributes or links of specific entities. We focus only
on class-level prediction, and describe algorithms for learning class-level
models that are orders of magnitude faster for this task. Our algorithms learn
Bayes nets with relational structure, leveraging the efficiency of single-table
nonrelational Bayes net learners. An evaluation of our methods on three data
sets shows that they are computationally feasible for realistic table sizes,
and that the learned structures represent the statistical information in the
databases well. After learning compiles the database statistics into a Bayes
net, querying these statistics via Bayes net inference is faster than with SQL
queries, and does not depend on the size of the database.
|
0811.4483
|
Wide spread spectrum watermarking with side information and interference
cancellation
|
cs.MM cs.IT math.IT
|
Nowadays, a popular method used for additive watermarking is wide spread
spectrum. It consists in adding a spread signal into the host document. This
signal is obtained by the sum of a set of carrier vectors, which are modulated
by the bits to be embedded. To extract these embedded bits, weighted
correlations between the watermarked document and the carriers are computed.
Unfortunately, even without any attack, the obtained set of bits can be
corrupted due to the interference with the host signal (host interference) and
also due to the interference with the others carriers (inter-symbols
interference (ISI) due to the non-orthogonality of the carriers). Some recent
watermarking algorithms deal with host interference using side informed
methods, but inter-symbols interference problem is still open. In this paper,
we deal with interference cancellation methods, and we propose to consider ISI
as side information and to integrate it into the host signal. This leads to a
great improvement of extraction performance in term of signal-to-noise ratio
and/or watermark robustness.
|
0811.4489
|
Automatic Generation of the Axial Lines of Urban Environments to Capture
What We Perceive
|
cs.CG cs.CV
|
Based on the concepts of isovists and medial axes, we developed a set of
algorithms that can automatically generate axial lines for representing
individual linearly stretched parts of open space of an urban environment. Open
space is the space between buildings, where people can freely move around. The
generation of the axial lines has been a key aspect of space syntax research,
conventionally relying on hand-drawn axial lines of an urban environment, often
called axial map, for urban morphological analysis. Although various attempts
have been made towards an automatic solution, few of them can produce the axial
map that consists of the least number of longest visibility lines, and none of
them really works for different urban environments. Our algorithms provide a
better solution than existing ones. Throughout this paper, we have also argued
and demonstrated that the axial lines constitute a true skeleton, superior to
medial axes, in capturing what we perceive about the urban environment.
Keywords: Visibility, space syntax, topological analysis, medial axes, axial
lines, isovists
|
0811.4565
|
Ergodic Capacity Analysis of Amplify-and-Forward MIMO Dual-Hop Systems
|
cs.IT math.IT
|
This paper presents an analytical characterization of the ergodic capacity of
amplify-and-forward (AF) MIMO dual-hop relay channels, assuming that the
channel state information is available at the destination terminal only. In
contrast to prior results, our expressions apply for arbitrary numbers of
antennas and arbitrary relay configurations. We derive an expression for the
exact ergodic capacity, simplified closed-form expressions for the high SNR
regime, and tight closed-form upper and lower bounds. These results are made
possible to employing recent tools from finite-dimensional random matrix theory
to derive new closed-form expressions for various statistical properties of the
equivalent AF MIMO dual-hop relay channel, such as the distribution of an
unordered eigenvalue and certain random determinant properties. Based on the
analytical capacity expressions, we investigate the impact of the system and
channel characteristics, such as the antenna configuration and the relay power
gain. We also demonstrate a number of interesting relationships between the
dual-hop AF MIMO relay channel and conventional point-to-point MIMO channels in
various asymptotic regimes.
|
0811.4603
|
Frozen Footprints
|
cs.DL cs.IR
|
Bibliometrics has the ambitious goal of measuring science. To this end, it
exploits the way science is disseminated trough scientific publications and the
resulting citation network of scientific papers. We survey the main historical
contributions to the field, the most interesting bibliometric indicators, and
the most popular bibliometric data sources. Moreover, we discuss distributions
commonly used to model bibliometric phenomena and give an overview of methods
to build bibliometric maps of science.
|
0811.4630
|
Channel State Prediction, Feedback and Scheduling for a Multiuser
MIMO-OFDM Downlink
|
cs.IT math.IT
|
We consider the downlink of a MIMO-OFDM wireless systems where the
base-station (BS) has M antennas and serves K single-antenna user terminals
(UT) with K larger than or equal to M. Users estimate their channel vectors
from common downlink pilot symbols and feed back a prediction, which is used by
the BS to compute the linear beamforming matrix for the next time slot and to
select the users to be served according to the proportional fair scheduling
(PFS) algorithm. We consider a realistic physical channel model used as a
benchmark in standardization and some alternatives for the channel estimation
and prediction scheme. We show that a parametric method based on ESPRIT is able
to accurately predict the channel even for relatively high user mobility.
However, there exists a class of channels characterized by large Doppler spread
(high mobility) and clustered angular spread for which prediction is
intrinsically difficult and all considered methods fail. We propose a modified
PFS that take into account the "predictability" state of the UTs, and
significantly outperform the classical PFS in the presence of prediction
errors. The main conclusion of this work is that multiuser MIMO downlink yields
very good performance even in the presence of high mobility users, provided
that the nonpredictable users are handled appropriately
|
0811.4697
|
Informed stego-systems in active warden context: statistical
undetectability and capacity
|
cs.IT cs.MM math.IT
|
Several authors have studied stego-systems based on Costa scheme, but just a
few ones gave both theoretical and experimental justifications of these schemes
performance in an active warden context. We provide in this paper a
steganographic and comparative study of three informed stego-systems in active
warden context: scalar Costa scheme, trellis-coded quantization and spread
transform scalar Costa scheme. By leading on analytical formulations and on
experimental evaluations, we show the advantages and limits of each scheme in
term of statistical undetectability and capacity in the case of active warden.
Such as the undetectability is given by the distance between the stego-signal
and the cover distance. It is measured by the Kullback-Leibler distance.
|
0811.4699
|
Mapping Images with the Coherence Length Diagrams
|
cs.CV
|
Statistical pattern recognition methods based on the Coherence Length Diagram
(CLD) have been proposed for medical image analyses, such as quantitative
characterisation of human skin textures, and for polarized light microscopy of
liquid crystal textures. Further investigations are made on image maps
originated from such diagram and some examples related to irregularity of
microstructures are shown.
|
0811.4700
|
Trellis-coded quantization for public-key steganography
|
cs.MM cs.IT math.IT
|
This paper deals with public-key steganography in the presence of a passive
warden. The aim is to hide secret messages within cover-documents without
making the warden suspicious, and without any preliminar secret key sharing.
Whereas a practical attempt has been already done to provide a solution to this
problem, it suffers of poor flexibility (since embedding and decoding steps
highly depend on cover-signals statistics) and of little capacity compared to
recent data hiding techniques. Using the same framework, this paper explores
the use of trellis-coded quantization techniques (TCQ and turbo TCQ) to design
a more efficient public-key scheme. Experiments on audio signals show great
improvements considering Cachin's security criterion.
|
0811.4702
|
Information-theoretic resolution of perceptual WSS watermarking of non
i.i.d. Gaussian signals
|
cs.IT cs.MM math.IT
|
The theoretical foundations of data hiding have been revealed by formulating
the problem as message communication over a noisy channel. We revisit the
problem in light of a more general characterization of the watermark channel
and of weighted distortion measures. Considering spread spectrum based
information hiding, we release the usual assumption of an i.i.d. cover signal.
The game-theoretic resolution of the problem reveals a generalized
characterization of optimum attacks. The paper then derives closed-form
expressions for the different parameters exhibiting a practical embedding and
extraction technique.
|
0811.4706
|
Comparing Measures of Sparsity
|
cs.IT math.IT
|
Sparsity of representations of signals has been shown to be a key concept of
fundamental importance in fields such as blind source separation, compression,
sampling and signal analysis. The aim of this paper is to compare several
commonlyused sparsity measures based on intuitive attributes. Intuitively, a
sparse representation is one in which a small number of coefficients contain a
large proportion of the energy. In this paper six properties are discussed:
(Robin Hood, Scaling, Rising Tide, Cloning, Bill Gates and Babies), each of
which a sparsity measure should have. The main contributions of this paper are
the proofs and the associated summary table which classify commonly-used
sparsity measures based on whether or not they satisfy these six propositions
and the corresponding proofs. Only one of these measures satisfies all six: The
Gini Index. measures based on whether or not they satisfy these six
propositions and the corresponding proofs. Only one of these measures satisfies
all six: The Gini Index.
|
0811.4717
|
Prospective Study for Semantic Inter-Media Fusion in Content-Based
Medical Image Retrieval
|
cs.IR cs.CL
|
One important challenge in modern Content-Based Medical Image Retrieval
(CBMIR) approaches is represented by the semantic gap, related to the
complexity of the medical knowledge. Among the methods that are able to close
this gap in CBMIR, the use of medical thesauri/ontologies has interesting
perspectives due to the possibility of accessing on-line updated relevant
webservices and to extract real-time medical semantic structured information.
The CBMIR approach proposed in this paper uses the Unified Medical Language
System's (UMLS) Metathesaurus to perform a semantic indexing and fusion of
medical media. This fusion operates before the query processing (retrieval) and
works at an UMLS-compliant conceptual indexing level. Our purpose is to study
various techniques related to semantic data alignment, preprocessing, fusion,
clustering and retrieval, by evaluating the various techniques and highlighting
future research directions. The alignment and the preprocessing are based on
partial text/image retrieval feedback and on the data structure. We analyze
various probabilistic, fuzzy and evidence-based approaches for the fusion
process and different similarity functions for the retrieval process. All the
proposed methods are evaluated on the Cross Language Evaluation Forum's (CLEF)
medical image retrieval benchmark, by focusing also on a more homogeneous
component medical image database: the Pathology Education Instructional
Resource (PEIR).
|
0811.4718
|
On the Fourier Spectra of the Infinite Families of Quadratic APN
Functions
|
cs.IT cs.CR cs.DM math.IT
|
It is well known that a quadratic function defined on a finite field of odd
degree is almost bent (AB) if and only if it is almost perfect nonlinear (APN).
For the even degree case there is no apparent relationship between the values
in the Fourier spectrum of a function and the APN property. In this article we
compute the Fourier spectrum of the new quadranomial family of APN functions.
With this result, all known infinite families of APN functions now have their
Fourier spectra and hence their nonlinearities computed.
|
0811.4733
|
Kinematic Analysis of a Serial - Parallel Machine Tool: the VERNE
machine
|
cs.RO
|
The paper derives the inverse and the forward kinematic equations of a serial
- parallel 5-axis machine tool: the VERNE machine. This machine is composed of
a three-degree-of-freedom (DOF) parallel module and a two-DOF serial tilting
table. The parallel module consists of a moving platform that is connected to a
fixed base by three non-identical legs. These legs are connected in a way that
the combined effects of the three legs lead to an over-constrained mechanism
with complex motion. This motion is defined as a simultaneous combination of
rotation and translation. In this paper we propose symbolical methods that able
to calculate all kinematic solutions and identify the acceptable one by adding
analytical constraint on the disposition of legs of the parallel module.
|
0811.4773
|
Two-way source coding with a helper
|
cs.IT math.IT
|
Consider the two-way rate-distortion problem in which a helper sends a common
limited-rate message to both users based on side information at its disposal.
We characterize the region of achievable rates and distortions where a Markov
form (Helper)-(User 1)-(User 2) holds. The main insight of the result is that
in order to achieve the optimal rate, the helper may use a binning scheme, as
in Wyner-Ziv, where the side information at the decoder is the "further" user,
namely, User 2. We derive these regions explicitly for the Gaussian sources
with square error distortion, analyze a trade-off between the rate from the
helper and the rate from the source, and examine a special case where the
helper has the freedom to send different messages, at different rates, to the
encoder and the decoder.
|
0812.0038
|
Omnidirectional Relay in Wireless Networks
|
cs.IT math.IT
|
For wireless networks with multiple sources, an omnidirectional relay scheme
is developed, where each node can simultaneously relay different messages in
different directions. This is accomplished by the decode-and-forward relay
strategy, with each relay binning the multiple messages to be transmitted, in
the same spirit of network coding. Specially for the all-source all-cast
problem, where each node is an independent source to be transmitted to all the
other nodes, this scheme completely eliminates interference in the whole
network, and the signal transmitted by any node can be used by any other node.
For networks with some kind of symmetry, assuming no beamforming is to be
performed, this omnidirectional relay scheme is capable of achieving the
maximum achievable rate.
|
0812.0070
|
An Integrated Software-based Solution for Modular and Self-independent
Networked Robot
|
cs.RO
|
An integrated software-based solution for a modular and self-independent
networked robot is introduced. The wirelessly operatable robot has been
developed mainly for autonomous monitoring works with full control over web.
The integrated software solution covers three components : a) the digital
signal processing unit for data retrieval and monitoring system; b) the
externally executable codes for control system; and c) the web programming for
interfacing the end-users with the robot. It is argued that this integrated
software-based approach is crucial to realize a flexible, modular and low
development cost mobile monitoring apparatus.
|
0812.0319
|
Secrecy Capacity of a Class of Broadcast Channels with an Eavesdropper
|
cs.IT math.IT
|
We study the security of communication between a single transmitter and
multiple receivers in a broadcast channel in the presence of an eavesdropper.
We consider several special classes of channels. As the first model, we
consider the degraded multi-receiver wiretap channel where the legitimate
receivers exhibit a degradedness order while the eavesdropper is more noisy
with respect to all legitimate receivers. We establish the secrecy capacity
region of this channel model. Secondly, we consider the parallel multi-receiver
wiretap channel with a less noisiness order in each sub-channel, where this
order is not necessarily the same for all sub-channels. We establish the common
message secrecy capacity and sum secrecy capacity of this channel. Thirdly, we
study a special class of degraded parallel multi-receiver wiretap channels and
provide a stronger result. In particular, we study the case with two
sub-channels two users and one eavesdropper, where there is a degradedness
order in each sub-channel such that in the first (resp. second) sub-channel the
second (resp. first) receiver is degraded with respect to the first (resp.
second) receiver, while the eavesdropper is degraded with respect to both
legitimate receivers in both sub-channels. We determine the secrecy capacity
region of this channel. Finally, we focus on a variant of this previous channel
model where the transmitter can use only one of the sub-channels at any time.
We characterize the secrecy capacity region of this channel as well.
|
0812.0329
|
Block-Sparsity: Coherence and Efficient Recovery
|
cs.IT math.IT
|
We consider compressed sensing of block-sparse signals, i.e., sparse signals
that have nonzero coefficients occuring in clusters. Based on an uncertainty
relation for block-sparse signals, we define a block-coherence measure and we
show that a block-version of the orthogonal matching pursuit algorithm recovers
block k-sparse signals in no more than k steps if the block-coherence is
sufficiently small. The same condition on block-sparsity is shown to guarantee
successful recovery through a mixed l2/l1 optimization approach. The
significance of the results lies in the fact that making explicit use of
block-sparsity can yield better reconstruction properties than treating the
signal as being sparse in the conventional sense thereby ignoring the
additional structure in the problem.
|
0812.0340
|
A Matlab Implementation of a Flat Norm Motivated Polygonal Edge Matching
Method using a Decomposition of Boundary into Four 1-Dimensional Currents
|
cs.CV cs.CG
|
We describe and provide code and examples for a polygonal edge matching
method.
|
0812.0382
|
k-means requires exponentially many iterations even in the plane
|
cs.CG cs.DS cs.LG
|
The k-means algorithm is a well-known method for partitioning n points that
lie in the d-dimensional space into k clusters. Its main features are
simplicity and speed in practice. Theoretically, however, the best known upper
bound on its running time (i.e. O(n^{kd})) can be exponential in the number of
points. Recently, Arthur and Vassilvitskii [3] showed a super-polynomial
worst-case analysis, improving the best known lower bound from \Omega(n) to
2^{\Omega(\sqrt{n})} with a construction in d=\Omega(\sqrt{n}) dimensions. In
[3] they also conjectured the existence of superpolynomial lower bounds for any
d >= 2.
Our contribution is twofold: we prove this conjecture and we improve the
lower bound, by presenting a simple construction in the plane that leads to the
exponential lower bound 2^{\Omega(n)}.
|
0812.0389
|
Approximation Algorithms for Bregman Co-clustering and Tensor Clustering
|
cs.DS cs.LG
|
In the past few years powerful generalizations to the Euclidean k-means
problem have been made, such as Bregman clustering [7], co-clustering (i.e.,
simultaneous clustering of rows and columns of an input matrix) [9,18], and
tensor clustering [8,34]. Like k-means, these more general problems also suffer
from the NP-hardness of the associated optimization. Researchers have developed
approximation algorithms of varying degrees of sophistication for k-means,
k-medians, and more recently also for Bregman clustering [2]. However, there
seem to be no approximation algorithms for Bregman co- and tensor clustering.
In this paper we derive the first (to our knowledge) guaranteed methods for
these increasingly important clustering settings. Going beyond Bregman
divergences, we also prove an approximation factor for tensor clustering with
arbitrary separable metrics. Through extensive experiments we evaluate the
characteristics of our method, and show that it also has practical impact.
|
0812.0438
|
An Introduction to Knowledge Management
|
cs.DB cs.CR
|
Knowledge has been lately recognized as one of the most important assets of
organizations. Managing knowledge has grown to be imperative for the success of
a company. This paper presents an overview of Knowledge Management and various
aspects of secure knowledge management. A case study of knowledge management
activities at Tata Steel is also discussed
|
0812.0564
|
Provenance Traces
|
cs.PL cs.DB
|
Provenance is information about the origin, derivation, ownership, or history
of an object. It has recently been studied extensively in scientific databases
and other settings due to its importance in helping scientists judge data
validity, quality and integrity. However, most models of provenance have been
stated as ad hoc definitions motivated by informal concepts such as "comes
from", "influences", "produces", or "depends on". These models lack clear
formalizations describing in what sense the definitions capture these intuitive
concepts. This makes it difficult to compare approaches, evaluate their
effectiveness, or argue about their validity.
We introduce provenance traces, a general form of provenance for the nested
relational calculus (NRC), a core database query language. Provenance traces
can be thought of as concrete data structures representing the operational
semantics derivation of a computation; they are related to the traces that have
been used in self-adjusting computation, but differ in important respects. We
define a tracing operational semantics for NRC queries that produces both an
ordinary result and a trace of the execution. We show that three pre-existing
forms of provenance for the NRC can be extracted from provenance traces.
Moreover, traces satisfy two semantic guarantees: consistency, meaning that the
traces describe what actually happened during execution, and fidelity, meaning
that the traces "explain" how the expression would behave if the input were
changed. These guarantees are much stronger than those contemplated for
previous approaches to provenance; thus, provenance traces provide a general
semantic foundation for comparing and unifying models of provenance in
databases.
|
0812.0617
|
The Capacity Region of the Cognitive Z-interference Channel with One
Noiseless Component
|
cs.IT math.IT
|
We study the discrete memoryless Z-interference channel (ZIC) where the
transmitter of the pair that suffers from interference is cognitive. We first
provide upper and lower bounds on the capacity of this channel. We then show
that, when the channel of the transmitter-receiver pair that does not face
interference is noiseless, the two bounds coincide and therefore yield the
capacity region. The obtained results imply that, unlike in the Gaussian
cognitive ZIC, in the considered channel superposition encoding at the
non-cognitive transmitter as well as Gel'fand-Pinsker encoding at the cognitive
transmitter are needed in order to minimize the impact of interference. As a
byproduct of the obtained capacity region, we obtain the capacity result for a
generalized Gel'fand-Pinsker problem.
|
0812.0621
|
Channel Estimation and Linear Precoding in Multiuser Multiple-Antenna
TDD Systems
|
cs.IT math.IT
|
Traditional approaches in the analysis of downlink systems decouple the
precoding and the channel estimation problems. However, in cellular systems
with mobile users, these two problems are in fact tightly coupled. In this
paper, this coupling is explicitly studied by accounting for channel training
overhead and estimation error while determining the overall system throughput.
The paper studies the problem of utilizing imperfect channel estimates for
efficient linear precoding and user selection. It presents precoding methods
that take into account the degree of channel estimation error.
Information-theoretic lower and upper bounds are derived to evaluate the
performance of these precoding methods. In typical scenarios, these bounds are
close.
|
0812.0659
|
Probabilistic reasoning with answer sets
|
cs.AI cs.LO
|
This paper develops a declarative language, P-log, that combines logical and
probabilistic arguments in its reasoning. Answer Set Prolog is used as the
logical foundation, while causal Bayes nets serve as a probabilistic
foundation. We give several non-trivial examples and illustrate the use of
P-log for knowledge representation and updating of knowledge. We argue that our
approach to updates is more appealing than existing approaches. We give
sufficiency conditions for the coherency of P-log programs and show that Bayes
nets can be easily mapped to coherent P-log programs.
|
0812.0698
|
Emergent Community Structure in Social Tagging Systems
|
cs.IR cs.CY cs.HC
|
A distributed classification paradigm known as collaborative tagging has been
widely adopted in new Web applications designed to manage and share online
resources. Users of these applications organize resources (Web pages, digital
photographs, academic papers) by associating with them freely chosen text
labels, or tags. Here we leverage the social aspects of collaborative tagging
and introduce a notion of resource distance based on the collective tagging
activity of users. We collect data from a popular system and perform
experiments showing that our definition of distance can be used to build a
weighted network of resources with a detectable community structure. We show
that this community structure clearly exposes the semantic relations among
resources. The communities of resources that we observe are a genuinely
emergent feature, resulting from the uncoordinated activity of a large number
of users, and their detection paves the way for mapping emergent semantics in
social tagging systems.
|
0812.0743
|
A Novel Clustering Algorithm Based on Quantum Games
|
cs.LG cs.AI cs.CV cs.GT cs.MA cs.NE quant-ph
|
Enormous successes have been made by quantum algorithms during the last
decade. In this paper, we combine the quantum game with the problem of data
clustering, and then develop a quantum-game-based clustering algorithm, in
which data points in a dataset are considered as players who can make decisions
and implement quantum strategies in quantum games. After each round of a
quantum game, each player's expected payoff is calculated. Later, he uses a
link-removing-and-rewiring (LRR) function to change his neighbors and adjust
the strength of links connecting to them in order to maximize his payoff.
Further, algorithms are discussed and analyzed in two cases of strategies, two
payoff matrixes and two LRR functions. Consequently, the simulation results
have demonstrated that data points in datasets are clustered reasonably and
efficiently, and the clustering algorithms have fast rates of convergence.
Moreover, the comparison with other algorithms also provides an indication of
the effectiveness of the proposed approach.
|
0812.0759
|
A new Contrast Based Image Fusion using Wavelet Packets
|
cs.IT cs.MM math.IT
|
Image Fusion, a technique which combines complimentary information from
different images of the same scene so that the fused image is more suitable for
segmentation, feature extraction, object recognition and Human Visual System.
In this paper, a simple yet efficient algorithm is presented based on contrast
using wavelet packet decomposition. First, all the source images are decomposed
into low and high frequency sub-bands and then fusion of high frequency
sub-bands is done by the means of Directive Contrast. Now, inverse wavelet
packet transform is performed to reconstruct the fused image. The performance
of the algorithm is carried out by the comparison made between proposed and
existing algorithm.
|
0812.0790
|
Justifications for Logic Programs under Answer Set Semantics
|
cs.AI cs.PL
|
The paper introduces the notion of off-line justification for Answer Set
Programming (ASP). Justifications provide a graph-based explanation of the
truth value of an atom w.r.t. a given answer set. The paper extends also this
notion to provide justification of atoms during the computation of an answer
set (on-line justification), and presents an integration of on-line
justifications within the computation model of Smodels. Off-line and on-line
justifications provide useful tools to enhance understanding of ASP, and they
offer a basic data structure to support methodologies and tools for debugging
answer set programs. A preliminary implementation has been developed in
ASP-PROLOG.
(To appear in Theory and Practice of Logic Programming (TPLP))
|
0812.0874
|
Stroke Fragmentation based on Geometry Features and HMM
|
cs.HC cs.CV
|
Stroke fragmentation is one of the key steps in pen-based interaction. In
this letter, we present a unified HMM-based stroke fragmentation technique that
can do segment point location and primitive type determination simultaneously.
The geometry features included are used to evaluate local features, and the HMM
model is utilized to measure the global drawing context. Experiments prove that
the model can efficiently represent smooth curves as well as strokes made up of
arbitrary lines and circular arcs.
|
0812.0882
|
Elagage d'un perceptron multicouches : utilisation de l'analyse de la
variance de la sensibilit\'e des param\`etres
|
cs.NE
|
The stucture determination of a neural network for the modelisation of a
system remain the core of the problem. Within this framework, we propose a
pruning algorithm of the network based on the use of the analysis of the
sensitivity of the variance of all the parameters of the network. This
algorithm will be tested on two examples of simulation and its performances
will be compared with three other algorithms of pruning of the literature
|
0812.0885
|
Elementary epistemological features of machine intelligence
|
cs.AI
|
Theoretical analysis of machine intelligence (MI) is useful for defining a
common platform in both theoretical and applied artificial intelligence (AI).
The goal of this paper is to set canonical definitions that can assist
pragmatic research in both strong and weak AI. Described epistemological
features of machine intelligence include relationship between intelligent
behavior, intelligent and unintelligent machine characteristics, observable and
unobservable entities and classification of intelligence. The paper also
establishes algebraic definitions of efficiency and accuracy of MI tests as
their quality measure. The last part of the paper addresses the learning
process with respect to the traditional epistemology and the epistemology of MI
described here. The proposed views on MI positively correlate to the Hegelian
monistic epistemology and contribute towards amalgamating idealistic
deliberations with the AI theory, particularly in a local frame of reference.
|
0812.0933
|
Decision trees are PAC-learnable from most product distributions: a
smoothed analysis
|
cs.LG cs.CC
|
We consider the problem of PAC-learning decision trees, i.e., learning a
decision tree over the n-dimensional hypercube from independent random labeled
examples. Despite significant effort, no polynomial-time algorithm is known for
learning polynomial-sized decision trees (even trees of any super-constant
size), even when examples are assumed to be drawn from the uniform distribution
on {0,1}^n. We give an algorithm that learns arbitrary polynomial-sized
decision trees for {\em most product distributions}. In particular, consider a
random product distribution where the bias of each bit is chosen independently
and uniformly from, say, [.49,.51]. Then with high probability over the
parameters of the product distribution and the random examples drawn from it,
the algorithm will learn any tree. More generally, in the spirit of smoothed
analysis, we consider an arbitrary product distribution whose parameters are
specified only up to a [-c,c] accuracy (perturbation), for an arbitrarily small
positive constant c.
|
0812.0972
|
Network Protection Codes: Providing Self-healing in Autonomic Networks
Using Network Coding
|
cs.NI cs.IT math.IT
|
Agile recovery from link failures in autonomic communication networks is
essential to increase robustness, accessibility, and reliability of data
transmission. However, this must be done with the least amount of protection
resources, while using simple management plane functionality. Recently, network
coding has been proposed as a solution to provide agile and cost efficient
network self-healing against link failures, in a manner that does not require
data rerouting, packet retransmission, or failure localization, hence leading
to simple control and management planes. To achieve this, separate paths have
to be provisioned to carry encoded packets, hence requiring either the addition
of extra links, or reserving some of the resources for this purpose.
In this paper we introduce autonomic self-healing strategies for autonomic
networks in order to protect against link failures. The strategies are based on
network coding and reduced capacity, which is a technique that we call network
protection codes (NPC). In these strategies, an autonomic network is able to
provide self-healing from various network failures affecting network operation.
The techniques improve service and enhance reliability of autonomic
communication.
Network protection codes are extended to provide self-healing from multiple
link failures in autonomic networks. We provide implementation aspects of the
proposed strategies. We present bounds and network protection code
constructions. Finally, we study the construction of such codes over the binary
field. The paper also develops an Integer Linear Program formulation to
evaluate the cost of provisioning connections using the proposed strategies.
|
0812.1014
|
Adaptive Spam Detection Inspired by a Cross-Regulation Model of Immune
Dynamics: A Study of Concept Drift
|
cs.AI cs.IR nlin.AO
|
This paper proposes a novel solution to spam detection inspired by a model of
the adaptive immune system known as the crossregulation model. We report on the
testing of a preliminary algorithm on six e-mail corpora. We also compare our
results statically and dynamically with those obtained by the Naive Bayes
classifier and another binary classification method we developed previously for
biomedical text-mining applications. We show that the cross-regulation model is
competitive against those and thus promising as a bio-inspired algorithm for
spam detection in particular, and binary classification in general.
|
0812.1029
|
Uncovering protein interaction in abstracts and text using a novel
linear model and word proximity networks
|
cs.IR cs.LG
|
We participated in three of the protein-protein interaction subtasks of the
Second BioCreative Challenge: classification of abstracts relevant for
protein-protein interaction (IAS), discovery of protein pairs (IPS) and text
passages characterizing protein interaction (ISS) in full text documents. We
approached the abstract classification task with a novel, lightweight linear
model inspired by spam-detection techniques, as well as an uncertainty-based
integration scheme. We also used a Support Vector Machine and the Singular
Value Decomposition on the same features for comparison purposes. Our approach
to the full text subtasks (protein pair and passage identification) includes a
feature expansion method based on word-proximity networks. Our approach to the
abstract classification task (IAS) was among the top submissions for this task
in terms of the measures of performance used in the challenge evaluation
(accuracy, F-score and AUC). We also report on a web-tool we produced using our
approach: the Protein Interaction Abstract Relevance Evaluator (PIARE). Our
approach to the full text tasks resulted in one of the highest recall rates as
well as mean reciprocal rank of correct passages. Our approach to abstract
classification shows that a simple linear model, using relatively few features,
is capable of generalizing and uncovering the conceptual nature of
protein-protein interaction from the bibliome. Since the novel approach is
based on a very lightweight linear model, it can be easily ported and applied
to similar problems. In full text problems, the expansion of word features with
word-proximity networks is shown to be useful, though the need for some
improvements is discussed.
|
0812.1091
|
Communicating the Difference of Correlated Gaussian Sources Over a MAC
|
cs.IT math.IT
|
This paper considers the problem of transmitting the difference of two
jointly Gaussian sources over a two-user additive Gaussian noise multiple
access channel (MAC). The goal is to recover this difference within an average
mean squared error distortion criterion. Each transmitter has access to only
one of the two Gaussian sources and is limited by an average power constraint.
In this work, a lattice coding scheme that achieves a distortion within a
constant of a distortion lower bound is presented if the signal to noise ratio
(SNR) is greater than a threshold. Further, uncoded transmission is shown to be
worse in performance to lattice coding methods. An alternative lattice coding
scheme is presented that can potentially improve on the performance of uncoded
transmission.
|
0812.1094
|
S\'election de la structure d'un perceptron multicouches pour la
r\'eduction dun mod\`ele de simulation d'une scierie
|
cs.NE
|
Simulation is often used to evaluate the relevance of a Directing Program of
Production (PDP) or to evaluate its impact on detailed sc\'enarii of
scheduling. Within this framework, we propose to reduce the complexity of a
model of simulation by exploiting a multilayer perceptron. A main phase of the
modeling of one system using a multilayer perceptron remains the determination
of the structure of the network. We propose to compare and use various pruning
algorithms in order to determine the optimal structure of the network used to
reduce the complexity of the model of simulation of our case of application: a
sawmill.
|
0812.1119
|
An analysis of a random algorithm for estimating all the matchings
|
cs.GR cs.AI
|
Counting the number of all the matchings on a bipartite graph has been
transformed into calculating the permanent of a matrix obtained from the
extended bipartite graph by Yan Huo, and Rasmussen presents a simple approach
(RM) to approximate the permanent, which just yields a critical ratio
O($n\omega(n)$) for almost all the 0-1 matrices, provided it's a simple
promising practical way to compute this #P-complete problem. In this paper, the
performance of this method will be shown when it's applied to compute all the
matchings based on that transformation. The critical ratio will be proved to be
very large with a certain probability, owning an increasing factor larger than
any polynomial of $n$ even in the sense for almost all the 0-1 matrices. Hence,
RM fails to work well when counting all the matchings via computing the
permanent of the matrix. In other words, we must carefully utilize the known
methods of estimating the permanent to count all the matchings through that
transformation.
|
0812.1126
|
Emerge-Sort: Converging to Ordered Sequences by Simple Local Operators
|
cs.AI cs.DS
|
In this paper we examine sorting on the assumption that we do not know in
advance which way to sort a sequence of numbers and we set at work simple local
comparison and swap operators whose repeating application ends up in sorted
sequences. These are the basic elements of Emerge-Sort, our approach to
self-organizing sorting, which we then validate experimentally across a range
of samples. Observing an O(n2) run-time behaviour, we note that the n/logn
delay coefficient that differentiates Emerge-Sort from the classical comparison
based algorithms is an instantiation of the price of anarchy we pay for not
imposing a sorting order and for letting that order emerge through the local
interactions.
|
0812.1155
|
Complex Agent Networks explaining the HIV epidemic among homosexual men
in Amsterdam
|
cs.MA q-bio.PE
|
Simulating the evolution of the Human Immunodeficiency Virus (HIV) epidemic
requires a detailed description of the population network, especially for small
populations in which individuals can be represented in detail and accuracy. In
this paper, we introduce the concept of a Complex Agent Network(CAN) to model
the HIV epidemics by combining agent-based modelling and complex networks, in
which agents represent individuals that have sexual interactions. The
applicability of CANs is demonstrated by constructing and executing a detailed
HIV epidemic model for men who have sex with men (MSM) in Amsterdam, including
a distinction between steady and casual relationships. We focus on MSM contacts
because they play an important role in HIV epidemics and have been tracked in
Amsterdam for a long time. Our experiments show good correspondence between the
historical data of the Amsterdam cohort and the simulation results.
|
0812.1203
|
An Efficient Adaptive Distributed Space-Time Coding Scheme for
Cooperative Relaying
|
cs.IT math.IT
|
A non-regenerative dual-hop wireless system based on a distributed space-time
coding strategy is considered. It is assumed that each relay retransmits an
appropriately scaled space-time coded version of its received signal. The main
goal of this paper is to investigate a power allocation strategy in relay
stations, which is based on minimizing the outage probability. In the high
signal-to-noise ratio regime for the relay-destination link, it is shown that a
threshold-based power allocation scheme (i.e., the relay remains silent if its
channel gain with the source is less than a prespecified threshold) is optimum.
Monte-Carlo simulations show that the derived on-off power allocation scheme
performs close to optimum for finite signal-to-noise ratio values. Numerical
results demonstrate a dramatic improvement in system performance as compared to
the case that the relay stations forward their received signals with full
power. In addition, a hybrid amplify-and-forward/detect-and-forward scheme is
proposed for the case that the quality of the source-relay link is good.
Finally, the robustness of the proposed scheme in the presence of channel
estimation errors is numerically evaluated.
|
0812.1244
|
Decomposition Principles and Online Learning in Cross-Layer Optimization
for Delay-Sensitive Applications
|
cs.MM cs.LG
|
In this paper, we propose a general cross-layer optimization framework in
which we explicitly consider both the heterogeneous and dynamically changing
characteristics of delay-sensitive applications and the underlying time-varying
network conditions. We consider both the independently decodable data units
(DUs, e.g. packets) and the interdependent DUs whose dependencies are captured
by a directed acyclic graph (DAG). We first formulate the cross-layer design as
a non-linear constrained optimization problem by assuming complete knowledge of
the application characteristics and the underlying network conditions. The
constrained cross-layer optimization is decomposed into several cross-layer
optimization subproblems for each DU and two master problems. The proposed
decomposition method determines the necessary message exchanges between layers
for achieving the optimal cross-layer solution. However, the attributes (e.g.
distortion impact, delay deadline etc) of future DUs as well as the network
conditions are often unknown in the considered real-time applications. The
impact of current cross-layer actions on the future DUs can be characterized by
a state-value function in the Markov decision process (MDP) framework. Based on
the dynamic programming solution to the MDP, we develop a low-complexity
cross-layer optimization algorithm using online learning for each DU
transmission. This online algorithm can be implemented in real-time in order to
cope with unknown source characteristics, network dynamics and resource
constraints. Our numerical results demonstrate the efficiency of the proposed
online algorithm.
|
0812.1340
|
Obtaining Depth Maps From Color Images By Region Based Stereo Matching
Algorithms
|
cs.CV
|
In the paper, region based stereo matching algorithms are developed for
extraction depth information from two color stereo image pair. A filter
eliminating unreliable disparity estimation was used for increasing reliability
of the disparity map. Obtained results by algorithms were represented and
compared.
|
0812.1357
|
A Novel Clustering Algorithm Based on Quantum Random Walk
|
cs.LG
|
The enormous successes have been made by quantum algorithms during the last
decade. In this paper, we combine the quantum random walk (QRW) with the
problem of data clustering, and develop two clustering algorithms based on the
one dimensional QRW. Then, the probability distributions on the positions
induced by QRW in these algorithms are investigated, which also indicates the
possibility of obtaining better results. Consequently, the experimental results
have demonstrated that data points in datasets are clustered reasonably and
efficiently, and the clustering algorithms are of fast rates of convergence.
Moreover, the comparison with other algorithms also provides an indication of
the effectiveness of the proposed approach.
|
0812.1394
|
Conceptual approach through an annotation process for the representation
and the information contents enhancement in economic intelligence (EI)
|
cs.IR
|
In the era of the information society, the impact of the information systems
on the economy of material and immaterial is certainly perceptible. With
regards to the information resources of an organization, the annotation
involved to enrich informational content, to track the intellectual activities
on a document and to set the added value on information for the benefit of
solving a decision-making problem in the context of economic intelligence. Our
contribution is distinguished by the representation of an annotation process
and its inherent concepts to lead the decisionmaker to an anticipated decision:
the provision of relevant and annotated information. Such information in the
system is made easy by taking into account the diversity of resources and those
that are well annotated so formally and informally by the EI actors. A capital
research framework consist of integrating in the decision-making process the
annotator activity, the software agent (or the reasoning mechanisms) and the
information resources enhancement.
|
0812.1405
|
Cognitive Coexistence between Infrastructure and Ad-hoc Systems
|
cs.IT math.IT
|
The rapid proliferation of wireless systems makes interference management
more and more important. This paper presents a novel cognitive coexistence
framework, which enables an infrastructure system to reduce interference to
ad-hoc or peer-to-peer communication links in close proximity. Motivated by the
superior resources of the infrastructure system, we study how its centralized
resource allocation can accommodate the ad-hoc links based on sensing and
predicting their interference patterns.
Based on an ON/OFF continuous-time Markov chain model, the optimal allocation
of power and transmission time is formulated as a convex optimization problem
and closed-form solutions are derived. The optimal scheduling is extended to
the case where the infrastructure channel is random and rate constraints need
only be met in the long-term average. Finally, the multi-terminal case is
addressed and the problem of optimal sub-channel allocation discussed.
Numerical performance analysis illustrates that utilizing the superior
flexibility of the infrastructure links can effectively mitigate interference.
|
0812.1462
|
Logic programs with propositional connectives and aggregates
|
cs.AI
|
Answer set programming (ASP) is a logic programming paradigm that can be used
to solve complex combinatorial search problems. Aggregates are an ASP construct
that plays an important role in many applications. Defining a satisfactory
semantics of aggregates turned out to be a difficult problem, and in this paper
we propose a new approach, based on an analogy between aggregates and
propositional connectives. First, we extend the definition of an answer
set/stable model to cover arbitrary propositional theories; then we define
aggregates on top of them both as primitive constructs and as abbreviations for
formulas. Our definition of an aggregate combines expressiveness and
simplicity, and it inherits many theorems about programs with nested
expressions, such as theorems about strong equivalence and splitting.
|
0812.1553
|
Analysis of Energy Efficiency in Fading Channels under QoS Constraints
|
cs.IT math.IT
|
Energy efficiency in fading channels in the presence of Quality of Service
(QoS) constraints is studied. Effective capacity, which provides the maximum
arrival rate that a wireless channel can sustain while satisfying statistical
QoS constraints, is considered. Spectral efficiency--bit energy tradeoff is
analyzed in the low-power and wideband regimes by employing the effective
capacity formulation, rather than the Shannon capacity. Through this analysis,
energy requirements under QoS constraints are identified. The analysis is
conducted under two assumptions: perfect channel side information (CSI)
available only at the receiver and perfect CSI available at both the receiver
and transmitter. In particular, it is shown in the low-power regime that the
minimum bit energy required under QoS constraints is the same as that attained
when there are no such limitations. However, this performance is achieved as
the transmitted power vanishes. Through the wideband slope analysis, the
increased energy requirements at low but nonzero power levels in the presence
of QoS constraints are determined. A similar analysis is also conducted in the
wideband regime, and minimum bit energy and wideband slope expressions are
obtained. In this regime, the required bit energy levels are found to be
strictly greater than those achieved when Shannon capacity is considered.
Overall, a characterization of the energy-bandwidth-delay tradeoff is provided.
|
0812.1554
|
Molecular communication: Physically realistic models and achievable
information rates
|
cs.IT math.IT
|
Molecular communication is a biologically-inspired method of communication
with attractive properties for microscale and nanoscale devices. In molecular
communication, messages are transmitted by releasing a pattern of molecules at
a transmitter, which propagate through a fluid medium towards a receiver. In
this paper, molecular communication is formulated as a mathematical
communication problem in an information-theoretic context. Physically realistic
models are obtained, with sufficient abstraction to allow manipulation by
communication and information theorists. Although mutual information in these
channels is intractable, we give sequences of upper and lower bounds on the
mutual information which trade off complexity and performance, and present
results to illustrate the feasibility of these bounds in estimating the true
mutual information.
|
0812.1557
|
To Cooperate, or Not to Cooperate in Imperfectly-Known Fading Channels
|
cs.IT math.IT
|
In this paper, communication over imperfectly-known fading channels with
different degrees of cooperation is studied. The three-node relay channel is
considered. It is assumed that communication starts with the network training
phase in which the receivers estimate the fading coefficients of their
respective channels. In the data transmission phase, amplify-and-forward and
decode-and-forward relaying schemes are employed. For different cooperation
protocols, achievable rate expressions are obtained. These achievable rate
expressions are then used to find the optimal resource allocation strategies.
In particular, the fraction of total time or bandwidth that needs to be
allocated to the relay for best performance is identified. Under a total power
constraint, optimal allocation of power between the source and relay is
investigated. Finally, bit energy requirements in the low-power regime are
studied.
|
0812.1558
|
Pilot-Symbol-Assisted Communications with Noncausal and Causal Wiener
Filters
|
cs.IT math.IT
|
In this paper, pilot-assisted transmission over time-selective flat fading
channels is studied. It is assumed that noncausal and causal Wiener filters are
employed at the receiver to perform channel estimation with the aid of training
symbols sent periodically by the transmitter. For both filters, the variances
of estimate errors are obtained from the Doppler power spectrum of the channel.
Subsequently, achievable rate expressions are provided. The training period,
and data and training power allocations are jointly optimized by maximizing the
achievable rate expressions. Numerical results are obtained by modeling the
fading as a Gauss-Markov process. The achievable rates of causal and noncausal
filtering approaches are compared. For the particular ranges of parameters
considered in the paper, the performance loss incurred by using a causal filter
as opposed to a noncausal filter is shown to be small. The impact of aliasing
that occurs in the undersampled version of the channel Doppler spectrum due to
fast fading is analyzed. Finally, energy-per-bit requirements are investigated
in the presence of noncausal and causal Wiener filters.
|
0812.1560
|
Achievable Rates and Training Optimization for Fading Relay Channels
with Memory
|
cs.IT math.IT
|
In this paper, transmission over time-selective, flat fading relay channels
is studied. It is assumed that channel fading coefficients are not known a
priori. Transmission takes place in two phases: network training phase and data
transmission phase. In the training phase, pilot symbols are sent and the
receivers employ single-pilot MMSE estimation or noncausal Wiener filter to
learn the channel. Amplify-and-Forward (AF) and Decode-and-Forward (DF)
techniques are considered in the data transmission phase and achievable rate
expressions are obtained. The training period, and data and training power
allocations are jointly optimized by using the achievable rate expressions.
Numerical results are obtained considering Gauss-Markov and lowpass fading
models. Achievable rates are computed and energy-per-bit requirements are
investigated. The optimal power distributions among pilot and data symbols are
provided.
|
0812.1597
|
Transmission Techniques for Relay-Interference Networks
|
cs.IT math.IT
|
In this paper we study the relay-interference wireless network, in which
relay (helper) nodes are to facilitate competing information flows over a
wireless network. We examine this in the context of a deterministic wireless
interaction model, which eliminates the channel noise and focuses on the signal
interactions. Using this model, we show that almost all the known schemes such
as interference suppression, interference alignment and interference separation
are necessary for relay-interference networks. In addition, we discover a new
interference management technique, which we call interference neutralization,
which allows for over-the-air interference removal, without the transmitters
having complete access the interfering signals. We show that interference
separation, suppression, and neutralization arise in a fundamental manner,
since we show complete characterizations for special configurations of the
relay-interference network.
|
0812.1599
|
Multi-Agent Reinforcement Learning and Genetic Policy Sharing
|
cs.MA cs.AI
|
The effects of policy sharing between agents in a multi-agent dynamical
system has not been studied extensively. I simulate a system of agents
optimizing the same task using reinforcement learning, to study the effects of
different population densities and policy sharing. I demonstrate that sharing
policies decreases the time to reach asymptotic behavior, and results in
improved asymptotic behavior.
|
0812.1629
|
An application of the O'Nan-Scott theorem to the group generated by the
round functions of an AES-like cipher
|
math.GR cs.IT math.IT
|
In a previous paper, we had proved that the permutation group generated by
the round functions of an AES-like cipher is primitive. Here we apply the O'Nan
Scott classification of primitive groups to prove that this group is the
alternating group.
|
0812.1713
|
Secret Communication with Feedback
|
cs.IT math.IT
|
Secure communication with feedback is studied. An achievability scheme in
which the backward channel is used to generate a shared secret key is proposed.
The scenario of binary symmetric forward and backward channels is considered,
and a combination of the proposed scheme and Maurer's coding scheme is shown to
achieve improved secrecy rates. The scenario of a Gaussian channel with perfect
output feedback is also analyzed and the Schalkwijk-Kailath coding scheme is
shown to achieve the secrecy capacity for this channel.
|
0812.1778
|
The Impact of QoS Constraints on the Energy Efficiency of Fixed-Rate
Wireless Transmissions
|
cs.IT math.IT
|
Transmission over wireless fading channels under quality of service (QoS)
constraints is studied when only the receiver has channel side information.
Being unaware of the channel conditions, transmitter is assumed to send the
information at a fixed rate. Under these assumptions, a two-state (ON-OFF)
transmission model is adopted, where information is transmitted reliably at a
fixed rate in the ON state while no reliable transmission occurs in the OFF
state. QoS limitations are imposed as constraints on buffer violation
probabilities, and effective capacity formulation is used to identify the
maximum throughput that a wireless channel can sustain while satisfying
statistical QoS constraints. Energy efficiency is investigated by obtaining the
bit energy required at zero spectral efficiency and the wideband slope in both
wideband and low-power regimes assuming that the receiver has perfect channel
side information (CSI). In both wideband and low-power regimes, the increased
energy requirements due to the presence of QoS constraints are quantified.
Comparisons with variable-rate/fixed-power and variable-rate/variable-power
cases are given. Energy efficiency is further analyzed in the presence of
channel uncertainties. The optimal fraction of power allocated to training is
identified under QoS constraints. It is proven that the minimum bit energy in
the low-power regime is attained at a certain nonzero power level below which
bit energy increases without bound with vanishing power.
|
0812.1780
|
On the Energy Efficiency of Orthogonal Signaling
|
cs.IT math.IT
|
In this paper, transmission over the additive white Gaussian noise (AWGN)
channel, and coherent and noncoherent fading channels using M-ary orthogonal
frequency-shift keying (FSK) or on-off frequency-shift keying (OOFSK) is
considered. The receiver is assumed to perform hard-decision detection. In this
setting, energy required to reliably send one bit of information is
investigated. It is shown that for fixed M and duty cycle, bit energy
requirements grow without bound as the signal-to-noise ratio (SNR) vanishes.
The minimum bit energy values are numerically obtained for different values of
M and the duty cycle. The impact of fading on the energy efficiency is
identified. Requirements to approach the minimum bit energy of -1.59 dB are
determined.
|
0812.1811
|
Stability of graph communities across time scales
|
physics.soc-ph cs.IR physics.data-an
|
The complexity of biological, social and engineering networks makes it
desirable to find natural partitions into communities that can act as
simplified descriptions and provide insight into the structure and function of
the overall system. Although community detection methods abound, there is a
lack of consensus on how to quantify and rank the quality of partitions. We
show here that the quality of a partition can be measured in terms of its
stability, defined in terms of the clustered autocovariance of a Markov process
taking place on the graph. Because the stability has an intrinsic dependence on
time scales of the graph, it allows us to compare and rank partitions at each
time and also to establish the time spans over which partitions are optimal.
Hence the Markov time acts effectively as an intrinsic resolution parameter
that establishes a hierarchy of increasingly coarser clusterings. Within our
framework we can then provide a unifying view of several standard partitioning
measures: modularity and normalized cut size can be interpreted as one-step
time measures, whereas Fiedler's spectral clustering emerges at long times. We
apply our method to characterize the relevance and persistence of partitions
over time for constructive and real networks, including hierarchical graphs and
social networks. We also obtain reduced descriptions for atomic level protein
structures over different time scales.
|
0812.1843
|
Identification of parameters underlying emotions and a classification of
emotions
|
cs.AI
|
The standard classification of emotions involves categorizing the expression
of emotions. In this paper, parameters underlying some emotions are identified
and a new classification based on these parameters is suggested.
|
0812.1857
|
Dependence Balance Based Outer Bounds for Gaussian Networks with
Cooperation and Feedback
|
cs.IT math.IT
|
We obtain new outer bounds on the capacity regions of the two-user multiple
access channel with generalized feedback (MAC-GF) and the two-user interference
channel with generalized feedback (IC-GF). These outer bounds are based on the
idea of dependence balance which was proposed by Hekstra and Willems [1]. To
illustrate the usefulness of our outer bounds, we investigate three different
channel models. We first consider a Gaussian MAC with noisy feedback (MAC-NF),
where transmitter $k$, $k=1,2$, receives a feedback $Y_{F_{k}}$, which is the
channel output $Y$ corrupted with additive white Gaussian noise $Z_{k}$. As the
feedback noise variances become large, one would expect the feedback to become
useless, which is not reflected by the cut-set bound. We demonstrate that our
outer bound improves upon the cut-set bound for all non-zero values of the
feedback noise variances. Moreover, in the limit as $\sigma_{Z_{k}}^{2}\to
\infty$, $k=1,2$, our outer bound collapses to the capacity region of the
Gaussian MAC without feedback. Secondly, we investigate a Gaussian MAC with
user-cooperation (MAC-UC), where each transmitter receives an additive white
Gaussian noise corrupted version of the channel input of the other transmitter
[2]. For this channel model, the cut-set bound is sensitive to the cooperation
noises, but not sensitive enough. For all non-zero values of cooperation noise
variances, our outer bound strictly improves upon the cut-set outer bound.
Thirdly, we investigate a Gaussian IC with user-cooperation (IC-UC). For this
channel model, the cut-set bound is again sensitive to cooperation noise
variances but not sensitive enough. We demonstrate that our outer bound
strictly improves upon the cut-set bound for all non-zero values of cooperation
noise variances.
|
0812.1869
|
Convex Sparse Matrix Factorizations
|
cs.LG
|
We present a convex formulation of dictionary learning for sparse signal
decomposition. Convexity is obtained by replacing the usual explicit upper
bound on the dictionary size by a convex rank-reducing term similar to the
trace norm. In particular, our formulation introduces an explicit trade-off
between size and sparsity of the decomposition of rectangular matrices. Using a
large set of synthetic examples, we compare the estimation abilities of the
convex and non-convex approaches, showing that while the convex formulation has
a single local minimum, this may lead in some cases to performance which is
inferior to the local minima of the non-convex formulation.
|
0812.2049
|
Consensus Answers for Queries over Probabilistic Databases
|
cs.DB
|
We address the problem of finding a "best" deterministic query answer to a
query over a probabilistic database. For this purpose, we propose the notion of
a consensus world (or a consensus answer) which is a deterministic world
(answer) that minimizes the expected distance to the possible worlds (answers).
This problem can be seen as a generalization of the well-studied inconsistent
information aggregation problems (e.g. rank aggregation) to probabilistic
databases. We consider this problem for various types of queries including SPJ
queries, \Topk queries, group-by aggregate queries, and clustering. For
different distance metrics, we obtain polynomial time optimal or approximation
algorithms for computing the consensus answers (or prove NP-hardness). Most of
our results are for a general probabilistic database model, called {\em and/xor
tree model}, which significantly generalizes previous probabilistic database
models like x-tuples and block-independent disjoint models, and is of
independent interest.
|
0812.2195
|
Equivalence of SQL Queries in Presence of Embedded Dependencies
|
cs.DB
|
We consider the problem of finding equivalent minimal-size reformulations of
SQL queries in presence of embedded dependencies [1]. Our focus is on
select-project-join (SPJ) queries with equality comparisons, also known as safe
conjunctive (CQ) queries, possibly with grouping and aggregation. For SPJ
queries, the semantics of the SQL standard treat query answers as multisets
(a.k.a. bags), whereas the stored relations may be treated either as sets,
which is called bag-set semantics for query evaluation, or as bags, which is
called bag semantics. (Under set semantics, both query answers and stored
relations are treated as sets.)
In the context of the above Query-Reformulation Problem, we develop a
comprehensive framework for equivalence of CQ queries under bag and bag-set
semantics in presence of embedded dependencies, and make a number of conceptual
and technical contributions. Specifically, we develop equivalence tests for CQ
queries in presence of arbitrary sets of embedded dependencies under bag and
bag-set semantics, under the condition that chase [9] under set semantics
(set-chase) on the inputs terminates. We also present equivalence tests for
aggregate CQ queries in presence of embedded dependencies. We use our
equivalence tests to develop sound and complete (whenever set-chase on the
inputs terminates) algorithms for solving instances of the Query-Reformulation
Problem with CQ queries under each of bag and bag-set semantics, as well as for
instances of the problem with aggregate queries.
|
0812.2202
|
Greedy Signal Recovery Review
|
math.NA cs.IT math.IT
|
The two major approaches to sparse recovery are L1-minimization and greedy
methods. Recently, Needell and Vershynin developed Regularized Orthogonal
Matching Pursuit (ROMP) that has bridged the gap between these two approaches.
ROMP is the first stable greedy algorithm providing uniform guarantees.
Even more recently, Needell and Tropp developed the stable greedy algorithm
Compressive Sampling Matching Pursuit (CoSaMP). CoSaMP provides uniform
guarantees and improves upon the stability bounds and RIC requirements of ROMP.
CoSaMP offers rigorous bounds on computational cost and storage. In many cases,
the running time is just O(NlogN), where N is the ambient dimension of the
signal. This review summarizes these major advances.
|
0812.2275
|
Secrecy capacity of a class of orthogonal relay eavesdropper channels
|
cs.IT math.IT
|
The secrecy capacity of relay channels with orthogonal components is studied
in the presence of an additional passive eavesdropper node. The relay and
destination receive signals from the source on two orthogonal channels such
that the destination also receives transmissions from the relay on its channel.
The eavesdropper can overhear either one or both of the orthogonal channels.
Inner and outer bounds on the secrecy capacity are developed for both the
discrete memoryless and the Gaussian channel models. For the discrete
memoryless case, the secrecy capacity is shown to be achieved by a partial
decode-and-forward (PDF) scheme when the eavesdropper can overhear only one of
the two orthogonal channels. Two new outer bounds are presented for the
Gaussian model using recent capacity results for a Gaussian multi-antenna
point-to-point channel with a multi-antenna eavesdropper. The outer bounds are
shown to be tight for two sub-classes of channels. The first sub-class is one
in which the source and relay are clustered and the and the eavesdropper
receives signals only on the channel from the source and the relay to the
destination, for which the PDF strategy is optimal. The second is a sub-class
in which the source does not transmit to the relay, for which a
noise-forwarding strategy is optimal.
|
0812.2291
|
Characterizing Truthful Multi-Armed Bandit Mechanisms
|
cs.DS cs.GT cs.LG
|
We consider a multi-round auction setting motivated by pay-per-click auctions
for Internet advertising. In each round the auctioneer selects an advertiser
and shows her ad, which is then either clicked or not. An advertiser derives
value from clicks; the value of a click is her private information. Initially,
neither the auctioneer nor the advertisers have any information about the
likelihood of clicks on the advertisements. The auctioneer's goal is to design
a (dominant strategies) truthful mechanism that (approximately) maximizes the
social welfare.
If the advertisers bid their true private values, our problem is equivalent
to the "multi-armed bandit problem", and thus can be viewed as a strategic
version of the latter. In particular, for both problems the quality of an
algorithm can be characterized by "regret", the difference in social welfare
between the algorithm and the benchmark which always selects the same "best"
advertisement. We investigate how the design of multi-armed bandit algorithms
is affected by the restriction that the resulting mechanism must be truthful.
We find that truthful mechanisms have certain strong structural properties --
essentially, they must separate exploration from exploitation -- and they incur
much higher regret than the optimal multi-armed bandit algorithms. Moreover, we
provide a truthful mechanism which (essentially) matches our lower bound on
regret.
|
0812.2301
|
Cooperative Hybrid ARQ Protocols: Unified Frameworks for Protocol
Analysis
|
cs.IT math.IT
|
Cooperative hybrid-ARQ (HARQ) protocols, which can exploit the spatial and
temporal diversities, have been widely studied. The efficiency of cooperative
HARQ protocols is higher than that of cooperative protocols, because
retransmissions are only performed when necessary. We classify cooperative HARQ
protocols as three decode-and-forward based HARQ (DF-HARQ) protocols and two
amplified-and-forward based (AF-HARQ) protocols. To compare these protocols and
obtain the optimum parameters, two unified frameworks are developed for
protocol analysis. Using the frameworks, we can evaluate and compare the
maximum throughput and outage probabilities according to the SNR, the relay
location, and the delay constraint for the protocols.
|
0812.2309
|
Classification of Cell Images Using MPEG-7-influenced Descriptors and
Support Vector Machines in Cell Morphology
|
stat.AP cs.CV stat.ML
|
Counting and classifying blood cells is an important diagnostic tool in
medicine. Support Vector Machines are increasingly popular and efficient and
could replace artificial neural network systems. Here a method to classify
blood cells is proposed using SVM. A set of statistics on images are
implemented in C++. The MPEG-7 descriptors Scalable Color Descriptor, Color
Structure Descriptor, Color Layout Descriptor and Homogeneous Texture
Descriptor are extended in size and combined with textural features
corresponding to textural properties perceived visually by humans. From a set
of images of human blood cells these statistics are collected. A SVM is
implemented and trained to classify the cell images. The cell images come from
a CellaVision DM-96 machine which classify cells from images from microscopy.
The output images and classification of the CellaVision machine is taken as
ground truth, a truth that is 90-95% correct. The problem is divided in two --
the primary and the simplified. The primary problem is to classify the same
classes as the CellaVision machine. The simplified problem is to differ between
the five most common types of white blood cells. An encouraging result is
achieved in both cases -- error rates of 10.8% and 3.1% -- considering that the
SVM is misled by the errors in ground truth. Conclusion is that further
investigation of performance is worthwhile.
|
0812.2313
|
Urologic robots and future directions
|
cs.RO
|
PURPOSE OF REVIEW: Robot-assisted laparoscopic surgery in urology has gained
immense popularity with the daVinci system, but a lot of research teams are
working on new robots. The purpose of this study is to review current urologic
robots and present future development directions. RECENT FINDINGS: Future
systems are expected to advance in two directions: improvements of remote
manipulation robots and developments of image-guided robots. SUMMARY: The final
goal of robots is to allow safer and more homogeneous outcomes with less
variability of surgeon performance, as well as new tools to perform tasks on
the basis of medical transcutaneous imaging, in a less invasive way, at lower
costs. It is expected that improvements for a remote system could be augmented
in reality, with haptic feedback, size reduction, and development of new tools
for natural orifice translumenal endoscopic surgery. The paradigm of
image-guided robots is close to clinical availability and the most advanced
robots are presented with end-user technical assessments. It is also notable
that the potential of robots lies much further ahead than the accomplishments
of the daVinci system. The integration of imaging with robotics holds a
substantial promise, because this can accomplish tasks otherwise impossible.
Image-guided robots have the potential to offer a paradigm shift.
|
0812.2324
|
The MIMO Iterative Waterfilling Algorithm
|
cs.IT cs.GT math.IT
|
This paper considers the non-cooperative maximization of mutual information
in the vector Gaussian interference channel in a fully distributed fashion via
game theory. This problem has been widely studied in a number of works during
the past decade for frequency-selective channels, and recently for the more
general MIMO case, for which the state-of-the art results are valid only for
nonsingular square channel matrices. Surprisingly, these results do not hold
true when the channel matrices are rectangular and/or rank deficient matrices.
The goal of this paper is to provide a complete characterization of the MIMO
game for arbitrary channel matrices, in terms of conditions guaranteeing both
the uniqueness of the Nash equilibrium and the convergence of asynchronous
distributed iterative waterfilling algorithms. Our analysis hinges on new
technical intermediate results, such as a new expression for the MIMO
waterfilling projection valid (also) for singular matrices, a mean-value
theorem for complex matrix-valued functions, and a general contraction theorem
for the multiuser MIMO watefilling mapping valid for arbitrary channel
matrices. The quite surprising result is that uniqueness/convergence conditions
in the case of tall (possibly singular) channel matrices are more restrictive
than those required in the case of (full rank) fat channel matrices. We also
propose a modified game and algorithm with milder conditions for the uniqueness
of the equilibrium and convergence, and virtually the same performance (in
terms of Nash equilibria) of the original game.
|
0812.2379
|
On the Decoder Error Probability of Rank Metric Codes and
Constant-Dimension Codes
|
cs.IT math.IT
|
Rank metric codes and constant-dimension codes (CDCs) have been considered
for error control in random network coding. Since decoder errors are more
detrimental to system performance than decoder failures, in this paper we
investigate the decoder error probability (DEP) of bounded distance decoders
(BDDs) for rank metric codes and CDCs. For rank metric codes, we consider a
channel motivated by network coding, where errors with the same row space are
equiprobable. Over such channels, we establish upper bounds on the DEPs of
BDDs, determine the exact DEP of BDDs for maximum rank distance (MRD) codes,
and show that MRD codes have the greatest DEPs up to a scalar. To evaluate the
DEPs of BDDs for CDCs, we first establish some fundamental geometric properties
of the projective space. Using these geometric properties, we then consider
BDDs in both subspace and injection metrics and derive analytical expressions
of their DEPs for CDCs, over a symmetric operator channel, as functions of
their distance distributions. Finally, we focus on CDCs obtained by lifting
rank metric codes and establish two important results: First, we derive
asymptotically tight upper bounds on the DEPs of BDDs in both metrics; Second,
we show that the DEPs for KK codes are the greatest up to a scalar among all
CDCs obtained by lifting rank metric codes.
|
0812.2388
|
Physics of risk and uncertainty in quantum decision making
|
physics.soc-ph cs.AI quant-ph
|
The Quantum Decision Theory, developed recently by the authors, is applied to
clarify the role of risk and uncertainty in decision making and in particular
in relation to the phenomenon of dynamic inconsistency. By formulating this
notion in precise mathematical terms, we distinguish three types of
inconsistency: time inconsistency, planning paradox, and inconsistency
occurring in some discounting effects. While time inconsistency is well
accounted for in classical decision theory, the planning paradox is in
contradiction with classical utility theory. It finds a natural explanation in
the frame of the Quantum Decision Theory. Different types of discounting
effects are analyzed and shown to enjoy a straightforward explanation within
the suggested theory. We also introduce a general methodology based on
self-similar approximation theory for deriving the evolution equations for the
probabilities of future prospects. This provides a novel classification of
possible discount factors, which include the previously known cases
(exponential or hyperbolic discounting), but also predicts a novel class of
discount factors that decay to a strictly positive constant for very large
future time horizons. This class may be useful to deal with very long-term
discounting situations associated with intergenerational public policy choices,
encompassing issues such as global warming and nuclear waste disposal.
|
0812.2405
|
A New Trend in Optimization on Multi Overcomplete Dictionary toward
Inpainting
|
cs.MM cs.AI
|
Recently, great attention was intended toward overcomplete dictionaries and
the sparse representations they can provide. In a wide variety of signal
processing problems, sparsity serves a crucial property leading to high
performance. Inpainting, the process of reconstructing lost or deteriorated
parts of images or videos, is an interesting application which can be handled
by suitably decomposition of an image through combination of overcomplete
dictionaries. This paper addresses a novel technique of such a decomposition
and investigate that through inpainting of images. Simulations are presented to
demonstrate the validation of our approach.
|
0812.2409
|
Sensing Models and Its Impact on Network Coverage in Wireless Sensor
Network
|
cs.IT math.IT
|
Network coverage of wireless sensor network (WSN) means how well an area of
interest is being monitored by the deployed network. It depends mainly on
sensing model of nodes. In this paper, we present three types of sensing models
viz. Boolean sensing model, shadow-fading sensing model and Elfes sensing
model. We investigate the impact of sensing models on network coverage. We also
investigate network coverage based on Poisson node distribution. A comparative
study between regular and random node placement has also been presented in this
paper. This study will be useful for coverage analysis of WSN.
|
0812.2411
|
Probabilistic SVM/GMM Classifier for Speaker-Independent Vowel
Recognition in Continues Speech
|
cs.MM cs.AI
|
In this paper, we discuss the issues in automatic recognition of vowels in
Persian language. The present work focuses on new statistical method of
recognition of vowels as a basic unit of syllables. First we describe a vowel
detection system then briefly discuss how the detected vowels can feed to
recognition unit. According to pattern recognition, Support Vector Machines
(SVM) as a discriminative classifier and Gaussian mixture model (GMM) as a
generative model classifier are two most popular techniques. Current
state-ofthe- art systems try to combine them together for achieving more power
of classification and improving the performance of the recognition systems. The
main idea of the study is to combine probabilistic SVM and traditional GMM
pattern classification with some characteristic of speech like band-pass energy
to achieve better classification rate. This idea has been analytically
formulated and tested on a FarsDat based vowel recognition system. The results
show inconceivable increases in recognition accuracy. The tests have been
carried out by various proposed vowel recognition algorithms and the results
have been compared.
|
0812.2454
|
On the statistical physics of directed polymers in a random medium and
their relation to tree codes
|
cs.IT math.IT
|
Using well-known results from statistical physics, concerning the almost-sure
behavior of the free energy of directed polymers in a random medium, we prove
that random tree codes achieve the distortion-rate function almost surely under
a certain symmetry condition.
|
0812.2458
|
Square Complex Orthogonal Designs with no Zero Entry for any $2^m$
Antennas
|
cs.IT math.IT
|
Space-time block codes from square complex orthogonal designs (SCOD) have
been extensively studied and most of the existing SCODs contain large number of
zeros. The zeros in the designs result in high peak-to-average power ratio and
also impose a severe constraint on hardware implementation of the code while
turning off some of the transmitting antennas whenever a zero is transmitted.
Recently, SCODs with no zero entry have been constructed for $2^a$ transmit
antennas whenever $a+1$ is a power of 2. Though there exists codes for 4 and 16
transmit antennas with no zero entry, there is no general method of
construction which gives codes for any number of transmit antennas. In this
paper, we construct SCODs for any power of 2 number of transmit antennas having
all its entries non-zero. Simulation results show that the codes constructed in
this paper outperform the existing codes for the same number of antennas under
peak power constraint while performing the same under average power constraint.
|
0812.2535
|
Pattern Recognition and Memory Mapping using Mirroring Neural Networks
|
cs.AI cs.NE
|
In this paper, we present a new kind of learning implementation to recognize
the patterns using the concept of Mirroring Neural Network (MNN) which can
extract information from distinct sensory input patterns and perform pattern
recognition tasks. It is also capable of being used as an advanced associative
memory wherein image data is associated with voice inputs in an unsupervised
manner. Since the architecture is hierarchical and modular it has the potential
of being used to devise learning engines of ever increasing complexity.
|
0812.2559
|
A Separation Algorithm for Improved LP-Decoding of Linear Block Codes
|
cs.IT math.IT
|
Maximum Likelihood (ML) decoding is the optimal decoding algorithm for
arbitrary linear block codes and can be written as an Integer Programming (IP)
problem. Feldman et al. relaxed this IP problem and presented Linear
Programming (LP) based decoding algorithm for linear block codes. In this
paper, we propose a new IP formulation of the ML decoding problem and solve the
IP with generic methods. The formulation uses indicator variables to detect
violated parity checks. We derive Gomory cuts from our formulation and use them
in a separation algorithm to find ML codewords. We further propose an efficient
method of finding cuts induced by redundant parity checks (RPC). Under certain
circumstances we can guarantee that these RPC cuts are valid and cut off the
fractional optimal solutions of LP decoding. We demonstrate on two LDPC codes
and one BCH code that our separation algorithm performs significantly better
than LP decoding.
|
0812.2574
|
Feature Selection By KDDA For SVM-Based MultiView Face Recognition
|
cs.CV cs.LG
|
Applications such as face recognition that deal with high-dimensional data
need a mapping technique that introduces representation of low-dimensional
features with enhanced discriminatory power and a proper classifier, able to
classify those complex features. Most of traditional Linear Discriminant
Analysis suffer from the disadvantage that their optimality criteria are not
directly related to the classification ability of the obtained feature
representation. Moreover, their classification accuracy is affected by the
"small sample size" problem which is often encountered in FR tasks. In this
short paper, we combine nonlinear kernel based mapping of data called KDDA with
Support Vector machine classifier to deal with both of the shortcomings in an
efficient and cost effective manner. The proposed here method is compared, in
terms of classification accuracy, to other commonly used FR methods on UMIST
face database. Results indicate that the performance of the proposed method is
overall superior to those of traditional FR approaches, such as the Eigenfaces,
Fisherfaces, and D-LDA methods and traditional linear classifiers.
|
0812.2575
|
Face Detection Using Adaboosted SVM-Based Component Classifier
|
cs.CV cs.LG
|
Recently, Adaboost has been widely used to improve the accuracy of any given
learning algorithm. In this paper we focus on designing an algorithm to employ
combination of Adaboost with Support Vector Machine as weak component
classifiers to be used in Face Detection Task. To obtain a set of effective
SVM-weaklearner Classifier, this algorithm adaptively adjusts the kernel
parameter in SVM instead of using a fixed one. Proposed combination outperforms
in generalization in comparison with SVM on imbalanced classification problem.
The proposed here method is compared, in terms of classification accuracy, to
other commonly used Adaboost methods, such as Decision Trees and Neural
Networks, on CMU+MIT face database. Results indicate that the performance of
the proposed method is overall superior to previous Adaboost approaches.
|
0812.2602
|
The statistical restricted isometry property and the Wigner semicircle
distribution of incoherent dictionaries
|
cs.IT cs.DM math.IT math.PR
|
In this article we present a statistical version of the Candes-Tao restricted
isometry property (SRIP for short) which holds in general for any incoherent
dictionary which is a disjoint union of orthonormal bases. In addition, we show
that, under appropriate normalization, the eigenvalues of the associated Gram
matrix fluctuate around 1 according to the Wigner semicircle distribution. The
result is then applied to various dictionaries that arise naturally in the
setting of finite harmonic analysis, giving, in particular, a better
understanding on a remark of Applebaum-Howard-Searle-Calderbank concerning RIP
for the Heisenberg dictionary of chirp like functions.
|
0812.2702
|
Standard Logics Are Valuation-Nonmonotonic
|
cs.LO cs.AI quant-ph
|
It has recently been discovered that both quantum and classical propositional
logics can be modelled by classes of non-orthomodular and thus non-distributive
lattices that properly contain standard orthomodular and Boolean classes,
respectively. In this paper we prove that these logics are complete even for
those classes of the former lattices from which the standard orthomodular
lattices and Boolean algebras are excluded. We also show that neither quantum
nor classical computers can be founded on the latter models. It follows that
logics are "valuation-nonmonotonic" in the sense that their possible models
(corresponding to their possible hardware implementations) and the valuations
for them drastically change when we add new conditions to their defining
conditions. These valuations can even be completely separated by putting them
into disjoint lattice classes by a technique presented in the paper.
|
0812.2709
|
Variations on a theme by Schalkwijk and Kailath
|
cs.IT math.IT
|
Schalkwijk and Kailath (1966) developed a class of block codes for Gaussian
channels with ideal feedback for which the probability of decoding error
decreases as a second-order exponent in block length for rates below capacity.
This well-known but surprising result is explained and simply derived here in
terms of a result by Elias (1956) concerning the minimum mean-square distortion
achievable in transmitting a single Gaussian random variable over multiple uses
of the same Gaussian channel. A simple modification of the Schalkwijk-Kailath
scheme is then shown to have an error probability that decreases with an
exponential order which is linearly increasing with block length. In the
infinite bandwidth limit, this scheme produces zero error probability using
bounded expected energy at all rates below capacity. A lower bound on error
probability for the finite bandwidth case is then derived in which the error
probability decreases with an exponential order which is linearly increasing in
block length at the same rate as the upper bound.
|
0812.2719
|
Secret Sharing over Fast-Fading MIMO Wiretap Channels
|
cs.IT math.IT
|
Secret sharing over the fast-fading MIMO wiretap channel is considered. A
source and a destination try to share secret information over a fast-fading
MIMO channel in the presence of a wiretapper who also makes channel
observations that are different from but correlated to those made by the
destination. An interactive authenticated unrestricted public channel is also
available for use by the source and destination in the secret sharing process.
This falls under the "channel-type model with wiretapper" considered by
Ahlswede and Csiszar. A minor extension of their result (to continuous channel
alphabets) is employed to evaluate the key capacity of the fast-fading MIMO
wiretap channel. The effects of spatial dimensionality provided by the use of
multiple antennas at the source, destination, and wiretapper are then
investigated.
|
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