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0805.0197
|
Flatness of the Energy Landscape for Horn Clauses
|
cond-mat.dis-nn cs.NE
|
The Little-Hopfield neural network programmed with Horn clauses is studied.
We argue that the energy landscape of the system, corresponding to the
inconsistency function for logical interpretations of the sets of Horn clauses,
has minimal ruggedness. This is supported by computer simulations.
|
0805.0202
|
A Pseudo-Boolean Solution to the Maximum Quartet Consistency Problem
|
cs.AI cs.LO
|
Determining the evolutionary history of a given biological data is an
important task in biological sciences. Given a set of quartet topologies over a
set of taxa, the Maximum Quartet Consistency (MQC) problem consists of
computing a global phylogeny that satisfies the maximum number of quartets. A
number of solutions have been proposed for the MQC problem, including Dynamic
Programming, Constraint Programming, and more recently Answer Set Programming
(ASP). ASP is currently the most efficient approach for optimally solving the
MQC problem. This paper proposes encoding the MQC problem with pseudo-Boolean
(PB) constraints. The use of PB allows solving the MQC problem with efficient
PB solvers, and also allows considering different modeling approaches for the
MQC problem. Initial results are promising, and suggest that PB can be an
effective alternative for solving the MQC problem.
|
0805.0231
|
CMA-ES with Two-Point Step-Size Adaptation
|
cs.NE
|
We combine a refined version of two-point step-size adaptation with the
covariance matrix adaptation evolution strategy (CMA-ES). Additionally, we
suggest polished formulae for the learning rate of the covariance matrix and
the recombination weights. In contrast to cumulative step-size adaptation or to
the 1/5-th success rule, the refined two-point adaptation (TPA) does not rely
on any internal model of optimality. In contrast to conventional
self-adaptation, the TPA will achieve a better target step-size in particular
with large populations. The disadvantage of TPA is that it relies on two
additional objective function
|
0805.0241
|
Asymptotically Good LDPC Convolutional Codes Based on Protographs
|
cs.IT math.IT
|
LDPC convolutional codes have been shown to be capable of achieving the same
capacity-approaching performance as LDPC block codes with iterative
message-passing decoding. In this paper, asymptotic methods are used to
calculate a lower bound on the free distance for several ensembles of
asymptotically good protograph-based LDPC convolutional codes. Further, we show
that the free distance to constraint length ratio of the LDPC convolutional
codes exceeds the minimum distance to block length ratio of corresponding LDPC
block codes.
|
0805.0268
|
Towards Exploring Fundamental Limits of System-Specific Cryptanalysis
Within Limited Attack Classes: Application to ABSG
|
cs.CR cs.IT math.IT
|
A new approach on cryptanalysis is proposed where the goal is to explore the
fundamental limits of a specific class of attacks against a particular
cryptosystem. As a first step, the approach is applied on ABSG, which is an
LFSR-based stream cipher where irregular decimation techniques are utilized.
Consequently, under some mild assumptions, which are common in cryptanalysis,
the tight lower bounds on the algorithmic complexity of successful Query-Based
Key-Recovery attacks are derived for two different setups of practical
interest. The proofs rely on the concept of ``typicality'' of information
theory.
|
0805.0272
|
Capacity of The Discrete-Time Non-Coherent Memoryless Gaussian Channels
at Low SNR
|
cs.IT math.IT
|
We address the capacity of a discrete-time memoryless Gaussian channel, where
the channel state information (CSI) is neither available at the transmitter nor
at the receiver. The optimal capacity-achieving input distribution at low
signal-to-noise ratio (SNR) is precisely characterized, and the exact capacity
of a non-coherent channel is derived. The derived relations allow to better
understanding the capacity of non-coherent channels at low SNR. Then, we
compute the non-coherence penalty and give a more precise characterization of
the sub-linear term in SNR. Finally, in order to get more insight on how the
optimal input varies with SNR, upper and lower bounds on the non-zero mass
point location of the capacity-achieving input are given.
|
0805.0330
|
Alternating Automata on Data Trees and XPath Satisfiability
|
cs.LO cs.DB cs.FL
|
A data tree is an unranked ordered tree whose every node is labelled by a
letter from a finite alphabet and an element ("datum") from an infinite set,
where the latter can only be compared for equality. The article considers
alternating automata on data trees that can move downward and rightward, and
have one register for storing data. The main results are that nonemptiness over
finite data trees is decidable but not primitive recursive, and that
nonemptiness of safety automata is decidable but not elementary. The proofs use
nondeterministic tree automata with faulty counters. Allowing upward moves,
leftward moves, or two registers, each causes undecidability. As corollaries,
decidability is obtained for two data-sensitive fragments of the XPath query
language.
|
0805.0337
|
On Distributed Function Computation in Structure-Free Random Networks
|
cs.IT math.IT
|
We consider in-network computation of MAX in a structure-free random multihop
wireless network. Nodes do not know their relative or absolute locations and
use the Aloha MAC protocol. For one-shot computation, we describe a protocol in
which the MAX value becomes available at the origin in $O(\sqrt{n/\log n})$
slots with high probability. This is within a constant factor of that required
by the best coordinated protocol. A minimal structure (knowledge of
hop-distance from the sink) is imposed on the network and with this structure,
we describe a protocol for pipelined computation of MAX that achieves a rate of
$\Omega(1/(\log^2 n)).$
|
0805.0360
|
Prediction and Mitigation of Crush Conditions in Emergency Evacuations
|
cs.CE cs.MA
|
Several simulation environments exist for the simulation of large-scale
evacuations of buildings, ships, or other enclosed spaces. These offer
sophisticated tools for the study of human behaviour, the recreation of
environmental factors such as fire or smoke, and the inclusion of architectural
or structural features, such as elevators, pillars and exits. Although such
simulation environments can provide insights into crowd behaviour, they lack
the ability to examine potentially dangerous forces building up within a crowd.
These are commonly referred to as crush conditions, and are a common cause of
death in emergency evacuations.
In this paper, we describe a methodology for the prediction and mitigation of
crush conditions. The paper is organised as follows. We first establish the
need for such a model, defining the main factors that lead to crush conditions,
and describing several exemplar case studies. We then examine current methods
for studying crush, and describe their limitations. From this, we develop a
three-stage hybrid approach, using a combination of techniques. We conclude
with a brief discussion of the potential benefits of our approach.
|
0805.0375
|
Wireless Secrecy in Cellular Systems with Infrastructure--Aided
Cooperation
|
cs.IT cs.CR math.IT
|
In cellular systems, confidentiality of uplink transmission with respect to
eavesdropping terminals can be ensured by creating intentional inteference via
scheduling of concurrent downlink transmissions. In this paper, this basic idea
is explored from an information-theoretic standpoint by focusing on a two-cell
scenario where the involved base stations are connected via a finite-capacity
backbone link. A number of transmission strategies are considered that aim at
improving uplink confidentiality under constraints on the downlink rate that
acts as an interfering signal. The strategies differ mainly in the way the
backbone link is exploited by the cooperating downlink- to the uplink-operated
base stations. Achievable rates are derived for both the Gaussian (unfaded) and
the fading cases, under different assumptions on the channel state information
available at different nodes. Numerical results are also provided to
corroborate the analysis. Overall, the analysis reveals that a combination of
scheduling and base station cooperation is a promising means to improve
transmission confidentiality in cellular systems.
|
0805.0438
|
Network-based consensus averaging with general noisy channels
|
cs.IT math.IT
|
This paper focuses on the consensus averaging problem on graphs under general
noisy channels. We study a particular class of distributed consensus algorithms
based on damped updates, and using the ordinary differential equation method,
we prove that the updates converge almost surely to exact consensus for finite
variance noise. Our analysis applies to various types of stochastic
disturbances, including errors in parameters, transmission noise, and
quantization noise. Under a suitable stability condition, we prove that the
error is asymptotically Gaussian, and we show how the asymptotic covariance is
specified by the graph Laplacian. For additive parameter noise, we show how the
scaling of the asymptotic MSE is controlled by the spectral gap of the
Laplacian.
|
0805.0459
|
Phase transition in SONFIS&SORST
|
cs.AI
|
In this study, we introduce general frame of MAny Connected Intelligent
Particles Systems (MACIPS). Connections and interconnections between particles
get a complex behavior of such merely simple system (system in
system).Contribution of natural computing, under information granulation
theory, are the main topics of this spacious skeleton. Upon this clue, we
organize two algorithms involved a few prominent intelligent computing and
approximate reasoning methods: self organizing feature map (SOM), Neuro- Fuzzy
Inference System and Rough Set Theory (RST). Over this, we show how our
algorithms can be taken as a linkage of government-society interaction, where
government catches various fashions of behavior: solid (absolute) or flexible.
So, transition of such society, by changing of connectivity parameters (noise)
from order to disorder is inferred. Add to this, one may find an indirect
mapping among financial systems and eventual market fluctuations with MACIPS.
Keywords: phase transition, SONFIS, SORST, many connected intelligent particles
system, society-government interaction
|
0805.0501
|
Decoding Generalized Concatenated Codes Using Interleaved Reed-Solomon
Codes
|
cs.IT math.IT
|
Generalized Concatenated codes are a code construction consisting of a number
of outer codes whose code symbols are protected by an inner code. As outer
codes, we assume the most frequently used Reed-Solomon codes; as inner code, we
assume some linear block code which can be decoded up to half its minimum
distance. Decoding up to half the minimum distance of Generalized Concatenated
codes is classically achieved by the Blokh-Zyablov-Dumer algorithm, which
iteratively decodes by first using the inner decoder to get an estimate of the
outer code words and then using an outer error/erasure decoder with a varying
number of erasures determined by a set of pre-calculated thresholds. In this
paper, a modified version of the Blokh-Zyablov-Dumer algorithm is proposed,
which exploits the fact that a number of outer Reed-Solomon codes with average
minimum distance d can be grouped into one single Interleaved Reed-Solomon code
which can be decoded beyond d/2. This allows to skip a number of decoding
iterations on the one hand and to reduce the complexity of each decoding
iteration significantly - while maintaining the decoding performance - on the
other.
|
0805.0507
|
Spread Codes and Spread Decoding in Network Coding
|
cs.IT math.IT
|
In this paper we introduce the class of Spread Codes for the use in random
network coding. Spread Codes are based on the construction of spreads in finite
projective geometry. The major contribution of the paper is an efficient
decoding algorithm of spread codes up to half the minimum distance.
|
0805.0510
|
Iterative Hard Thresholding for Compressed Sensing
|
cs.IT cs.NA math.IT math.NA
|
Compressed sensing is a technique to sample compressible signals below the
Nyquist rate, whilst still allowing near optimal reconstruction of the signal.
In this paper we present a theoretical analysis of the iterative hard
thresholding algorithm when applied to the compressed sensing recovery problem.
We show that the algorithm has the following properties (made more precise in
the main text of the paper)
- It gives near-optimal error guarantees.
- It is robust to observation noise.
- It succeeds with a minimum number of observations.
- It can be used with any sampling operator for which the operator and its
adjoint can be computed.
- The memory requirement is linear in the problem size.
- Its computational complexity per iteration is of the same order as the
application of the measurement operator or its adjoint.
- It requires a fixed number of iterations depending only on the logarithm of
a form of signal to noise ratio of the signal.
- Its performance guarantees are uniform in that they only depend on
properties of the sampling operator and signal sparsity.
|
0805.0514
|
Efficient recovering of operation tables of black box groups and rings
|
cs.IT cs.DM math.GR math.IT
|
People have been studying the following problem: Given a finite set S with a
hidden (black box) binary operation * on S which might come from a group law,
and suppose you have access to an oracle that you can ask for the operation x*y
of single pairs (x,y) you choose. What is the minimal number of queries to the
oracle until the whole binary operation is recovered, i.e. you know x*y for all
x,y in S?
This problem can trivially be solved by using |S|^2 queries to the oracle, so
the question arises under which circumstances you can succeed with a
significantly smaller number of queries.
In this presentation we give a lower bound on the number of queries needed
for general binary operations. On the other hand, we present algorithms solving
this problem by using |S| queries, provided that * is an abelian group
operation. We also investigate black box rings and give lower and upper bounds
for the number of queries needed to solve product recovering in this case.
|
0805.0516
|
The Gaussian MAC with Conferencing Encoders
|
cs.IT math.IT
|
We derive the capacity region of the Gaussian version of Willems's two-user
MAC with conferencing encoders. This setting differs from the classical MAC in
that, prior to each transmission block, the two transmitters can communicate
with each other over noise-free bit-pipes of given capacities. The derivation
requires a new technique for proving the optimality of Gaussian input
distributions in certain mutual information maximizations under a Markov
constraint. We also consider a Costa-type extension of the Gaussian MAC with
conferencing encoders. In this extension, the channel can be described as a
two-user MAC with Gaussian noise and Gaussian interference where the
interference is known non-causally to the encoders but not to the decoder. We
show that as in Costa's setting the interference sequence can be perfectly
canceled, i.e., that the capacity region without interference can be achieved.
|
0805.0521
|
On the Capacity of Free-Space Optical Intensity Channels
|
cs.IT math.IT
|
New upper and lower bounds are presented on the capacity of the free-space
optical intensity channel. This channel is characterized by inputs that are
nonnegative (representing the transmitted optical intensity) and by outputs
that are corrupted by additive white Gaussian noise (because in free space the
disturbances arise from many independent sources). Due to battery and safety
reasons the inputs are simultaneously constrained in both their average and
peak power. For a fixed ratio of the average power to the peak power the
difference between the upper and the lower bounds tends to zero as the average
power tends to infinity, and the ratio of the upper and lower bounds tends to
one as the average power tends to zero. The case where only an average-power
constraint is imposed on the input is treated separately. In this case, the
difference of the upper and lower bound tends to 0 as the average power tends
to infinity, and their ratio tends to a constant as the power tends to zero.
|
0805.0577
|
Infinity-Norm Sphere-Decoding
|
cs.IT math.IT
|
The most promising approaches for efficient detection in multiple-input
multiple-output (MIMO) wireless systems are based on sphere-decoding (SD). The
conventional (and optimum) norm that is used to conduct the tree traversal step
in SD is the l-2 norm. It was, however, recently observed that using the
l-infinity norm instead reduces the hardware complexity of SD considerably at
only a marginal performance loss. These savings result from a reduction in the
length of the critical path in the circuit and the silicon area required for
metric computation, but are also, as observed previously through simulation
results, a consequence of a reduction in the computational (i.e., algorithmic)
complexity. The aim of this paper is an analytical performance and
computational complexity analysis of l-infinity norm SD. For i.i.d. Rayleigh
fading MIMO channels, we show that l-infinity norm SD achieves full diversity
order with an asymptotic SNR gap, compared to l-2 norm SD, that increases at
most linearly in the number of receive antennas. Moreover, we provide a
closed-form expression for the computational complexity of l-infinity norm SD
based on which we establish that its complexity scales exponentially in the
system size. Finally, we characterize the tree pruning behavior of l-infinity
norm SD and show that it behaves fundamentally different from that of l-2 norm
SD.
|
0805.0589
|
Cascaded Orthogonal Space-Time Block Codes for Wireless Multi-Hop Relay
Networks
|
cs.IT math.IT
|
Distributed space-time block coding is a diversity technique to mitigate the
effects of fading in multi-hop wireless networks, where multiple relay stages
are used by a source to communicate with its destination. This paper proposes a
new distributed space-time block code called the cascaded orthogonal space-time
block code (COSTBC) for the case where the source and destination are equipped
with multiple antennas and each relay stage has one or more single antenna
relays. Each relay stage is assumed to have receive channel state information
(CSI) for all the channels from the source to itself, while the destination is
assumed to have receive CSI for all the channels. To construct the COSTBC,
multiple orthogonal space-time block codes are used in cascade by the source
and each relay stage. In the COSTBC, each relay stage separates the
constellation symbols of the orthogonal space-time block code sent by the
preceding relay stage using its CSI, and then transmits another orthogonal
space-time block code to the next relay stage. COSTBCs are shown to achieve the
maximum diversity gain in a multi-hop wireless network with flat Rayleigh
fading channels. Several explicit constructions of COSTBCs are also provided
for two-hop wireless networks with two and four source antennas and relay
nodes. It is also shown that COSTBCs require minimum decoding complexity thanks
to the connection to orthogonal space-time block codes.
|
0805.0615
|
On Expanded Cyclic Codes
|
cs.IT cs.CC math.IT math.RA
|
The paper has a threefold purpose. The first purpose is to present an
explicit description of expanded cyclic codes defined in $\GF(q^m)$. The
proposed explicit construction of expanded generator matrix and expanded parity
check matrix maintains the symbol-wise algebraic structure and thus keeps many
important original characteristics. The second purpose of this paper is to
identify a class of constant-weight cyclic codes. Specifically, we show that a
well-known class of $q$-ary BCH codes excluding the all-zero codeword are
constant-weight cyclic codes. Moreover, we show this class of codes achieve the
Plotkin bound. The last purpose of the paper is to characterize expanded cyclic
codes utilizing the proposed expanded generator matrix and parity check matrix.
We characterize the properties of component codewords of a codeword and
particularly identify the precise conditions under which a codeword can be
represented by a subbasis. Our developments reveal an alternative while more
general view on the subspace subcodes of Reed-Solomon codes. With the new
insights, we present an improved lower bound on the minimum distance of an
expanded cyclic code by exploiting the generalized concatenated structure. We
also show that the fixed-rate binary expanded Reed-Solomon codes are
asymptotically "bad", in the sense that the ratio of minimum distance over code
length diminishes with code length going to infinity. It overturns the
prevalent conjecture that they are "good" codes and deviates from the ensemble
of generalized Reed-Solomon codes which asymptotically achieves the
Gilbert-Varshamov bound.
|
0805.0642
|
Order to Disorder Transitions in Hybrid Intelligent Systems: a Hatch to
the Interactions of Nations -Governments
|
cs.AI cs.IT math.IT
|
In this study, under general frame of MAny Connected Intelligent Particles
Systems (MACIPS), we reproduce two new simple subsets of such intelligent
complex network, namely hybrid intelligent systems, involved a few prominent
intelligent computing and approximate reasoning methods: self organizing
feature map (SOM), Neuro-Fuzzy Inference System and Rough Set Theory (RST).
Over this, we show how our algorithms can be construed as a linkage of
government-society interaction, where government catches various fashions of
behavior: solid (absolute) or flexible. So, transition of such society, by
changing of connectivity parameters (noise) from order to disorder is inferred.
Add to this, one may find an indirect mapping among financial systems and
eventual market fluctuations with MACIPS.
|
0805.0697
|
Stochastic Optimization Approaches for Solving Sudoku
|
cs.NE
|
In this paper the Sudoku problem is solved using stochastic search techniques
and these are: Cultural Genetic Algorithm (CGA), Repulsive Particle Swarm
Optimization (RPSO), Quantum Simulated Annealing (QSA) and the Hybrid method
that combines Genetic Algorithm with Simulated Annealing (HGASA). The results
obtained show that the CGA, QSA and HGASA are able to solve the Sudoku puzzle
with CGA finding a solution in 28 seconds, while QSA finding a solution in 65
seconds and HGASA in 1.447 seconds. This is mainly because HGASA combines the
parallel searching of GA with the flexibility of SA. The RPSO was found to be
unable to solve the puzzle.
|
0805.0740
|
Diversity-Integration Trade-offs in MIMO Detection
|
cs.OH cs.IT math.IT
|
In this work, a MIMO detection problem is considered. At first, we derive the
Generalized Likelihood Ratio Test (GLRT) for arbitrary transmitted signals and
arbitrary time-correlation of the disturbance. Then, we investigate design
criteria for the transmitted waveforms in both power-unlimited and
power-limited systems and we study the interplay among the rank of the
optimized code matrix, the number of transmit diversity paths and the amount of
energy integrated along each path. The results show that increasing the rank of
the code matrix allows generating a larger number of diversity paths at the
price of reducing the average signal-to-clutter level along each path.
|
0805.0747
|
Pruning Attribute Values From Data Cubes with Diamond Dicing
|
cs.DB cs.DS
|
Data stored in a data warehouse are inherently multidimensional, but most
data-pruning techniques (such as iceberg and top-k queries) are unidimensional.
However, analysts need to issue multidimensional queries. For example, an
analyst may need to select not just the most profitable stores
or--separately--the most profitable products, but simultaneous sets of stores
and products fulfilling some profitability constraints. To fill this need, we
propose a new operator, the diamond dice. Because of the interaction between
dimensions, the computation of diamonds is challenging. We present the first
diamond-dicing experiments on large data sets. Experiments show that we can
compute diamond cubes over fact tables containing 100 million facts in less
than 35 minutes using a standard PC.
|
0805.0785
|
AGNOSCO - Identification of Infected Nodes with artificial Ant Colonies
|
cs.AI cs.MA
|
If a computer node is infected by a virus, worm or a backdoor, then this is a
security risk for the complete network structure where the node is associated.
Existing Network Intrusion Detection Systems (NIDS) provide a certain amount of
support for the identification of such infected nodes but suffer from the need
of plenty of communication and computational power. In this article, we present
a novel approach called AGNOSCO to support the identification of infected nodes
through the usage of artificial ant colonies. It is shown that AGNOSCO
overcomes the communication and computational power problem while identifying
infected nodes properly.
|
0805.0802
|
An Information-Theoretical View of Network-Aware Malware Attacks
|
cs.CR cs.IT cs.NI math.IT
|
This work investigates three aspects: (a) a network vulnerability as the
non-uniform vulnerable-host distribution, (b) threats, i.e., intelligent
malwares that exploit such a vulnerability, and (c) defense, i.e., challenges
for fighting the threats. We first study five large data sets and observe
consistent clustered vulnerable-host distributions. We then present a new
metric, referred to as the non-uniformity factor, which quantifies the
unevenness of a vulnerable-host distribution. This metric is essentially the
Renyi information entropy and better characterizes the non-uniformity of a
distribution than the Shannon entropy. Next, we analyze the propagation speed
of network-aware malwares in view of information theory. In particular, we draw
a relationship between Renyi entropies and randomized epidemic malware-scanning
algorithms. We find that the infection rates of malware-scanning methods are
characterized by the Renyi entropies that relate to the information bits in a
non-unform vulnerable-host distribution extracted by a randomized scanning
algorithm. Meanwhile, we show that a representative network-aware malware can
increase the spreading speed by exactly or nearly a non-uniformity factor when
compared to a random-scanning malware at an early stage of malware propagation.
This quantifies that how much more rapidly the Internet can be infected at the
early stage when a malware exploits an uneven vulnerable-host distribution as a
network-wide vulnerability. Furthermore, we analyze the effectiveness of
defense strategies on the spread of network-aware malwares. Our results
demonstrate that counteracting network-aware malwares is a significant
challenge for the strategies that include host-based defense and IPv6.
|
0805.0849
|
SANA - Network Protection through artificial Immunity
|
cs.CR cs.MA
|
Current network protection systems use a collection of intelligent components
- e.g. classifiers or rule-based firewall systems to detect intrusions and
anomalies and to secure a network against viruses, worms, or trojans. However,
these network systems rely on individuality and support an architecture with
less collaborative work of the protection components. They give less
administration support for maintenance, but offer a large number of individual
single points of failures - an ideal situation for network attacks to succeed.
In this work, we discuss the required features, the performance, and the
problems of a distributed protection system called SANA. It consists of a
cooperative architecture, it is motivated by the human immune system, where the
components correspond to artificial immune cells that are connected for their
collaborative work. SANA promises a better protection against intruders than
common known protection systems through an adaptive self-management while
keeping the resources efficiently by an intelligent reduction of redundant
tasks. We introduce a library of several novel and common used protection
components and evaluate the performance of SANA by a proof-of-concept
implementation.
|
0805.0909
|
SANA - Security Analysis in Internet Traffic through Artificial Immune
Systems
|
cs.CR cs.MA
|
The Attacks done by Viruses, Worms, Hackers, etc. are a Network
Security-Problem in many Organisations. Current Intrusion Detection Systems
have significant Disadvantages, e.g. the need of plenty of Computational Power
or the Local Installation. Therefore, we introduce a novel Framework for
Network Security which is called SANA. SANA contains an artificial Immune
System with artificial Cells which perform certain Tasks in order to to support
existing systems to better secure the Network against Intrusions. The
Advantages of SANA are that it is efficient, adaptive, autonomous, and
massively-distributed. In this Article, we describe the Architecture of the
artificial Immune System and the Functionality of the Components. We explain
briefly the Implementation and discuss Results.
|
0805.0963
|
Correlated Anarchy in Overlapping Wireless Networks
|
cs.GT cs.IT math.IT physics.soc-ph
|
We investigate the behavior of a large number of selfish users that are able
to switch dynamically between multiple wireless access-points (possibly
belonging to different standards) by introducing an iterated non-cooperative
game. Users start out completely uneducated and naive but, by using a fixed set
of strategies to process a broadcasted training signal, they quickly evolve and
converge to an evolutionarily stable equilibrium. Then, in order to measure
efficiency in this steady state, we adapt the notion of the price of anarchy to
our setting and we obtain an explicit analytic estimate for it by using methods
from statistical physics (namely the theory of replicas). Surprisingly, we find
that the price of anarchy does not depend on the specifics of the wireless
nodes (e.g. spectral efficiency) but only on the number of strategies per user
and a particular combination of the number of nodes, the number of users and
the size of the training signal. Finally, we map this game to the well-studied
minority game, generalizing its analysis to an arbitrary number of choices.
|
0805.0990
|
The pre-log of Gaussian broadcast with feedback can be two
|
cs.IT math.IT
|
A generic intuition says that the pre-log, or multiplexing gain, cannot be
larger than the minimum of the number of transmit and receive dimensions. This
suggests that for the scalar broadcast channel, the pre-log cannot exceed one.
By contrast, in this note, we show that when the noises are anti-correlated and
feedback is present, then a pre-log of two can be attained. In other words, in
this special case, in the limit of high SNR, the scalar Gaussian broadcast
channel turns into two parallel AWGN channels. Achievability is established via
a coding strategy due to Schalkwijk, Kailath, and Ozarow.
|
0805.1030
|
Decomposition Techniques for Subgraph Matching
|
cs.CC cs.CL
|
In the constraint programming framework, state-of-the-art static and dynamic
decomposition techniques are hard to apply to problems with complete initial
constraint graphs. For such problems, we propose a hybrid approach of these
techniques in the presence of global constraints. In particular, we solve the
subgraph isomorphism problem. Further we design specific heuristics for this
hard problem, exploiting its special structure to achieve decomposition. The
underlying idea is to precompute a static heuristic on a subset of its
constraint network, to follow this static ordering until a first problem
decomposition is available, and to switch afterwards to a fully propagated,
dynamically decomposing search. Experimental results show that, for sparse
graphs, our decomposition method solves more instances than dedicated,
state-of-the-art matching algorithms or standard constraint programming
approaches.
|
0805.1088
|
Network Coding for Speedup in Switches
|
cs.NI cs.IT math.IT
|
We present a graph theoretic upper bound on speedup needed to achieve 100%
throughput in a multicast switch using network coding. By bounding speedup, we
show the equivalence between network coding and speedup in multicast switches -
i.e. network coding, which is usually implemented using software, can in many
cases substitute speedup, which is often achieved by adding extra switch
fabrics. This bound is based on an approach to network coding problems called
the "enhanced conflict graph". We show that the "imperfection ratio" of the
enhanced conflict graph gives an upper bound on speedup. In particular, we
apply this result to K-by-N switches with traffic patterns consisting of
unicasts and broadcasts only to obtain an upper bound of min{(2K-1)/K,
2N/(N+1)}.
|
0805.1096
|
Adaptive Affinity Propagation Clustering
|
cs.AI
|
Affinity propagation clustering (AP) has two limitations: it is hard to know
what value of parameter 'preference' can yield an optimal clustering solution,
and oscillations cannot be eliminated automatically if occur. The adaptive AP
method is proposed to overcome these limitations, including adaptive scanning
of preferences to search space of the number of clusters for finding the
optimal clustering solution, adaptive adjustment of damping factors to
eliminate oscillations, and adaptive escaping from oscillations when the
damping adjustment technique fails. Experimental results on simulated and real
data sets show that the adaptive AP is effective and can outperform AP in
quality of clustering results.
|
0805.1153
|
Contact state analysis using NFIS and SOM
|
cs.NE cs.AI
|
This paper reports application of neuro- fuzzy inference system (NFIS) and
self organizing feature map neural networks (SOM) on detection of contact state
in a block system. In this manner, on a simple system, the evolution of contact
states, by parallelization of DDA, has been investigated. So, a comparison
between NFIS and SOM results has been presented. The results show applicability
of the proposed methods, by different accuracy, on detection of contact's
distribution.
|
0805.1154
|
Clustering of scientific citations in Wikipedia
|
cs.DL cs.NE
|
The instances of templates in Wikipedia form an interesting data set of
structured information. Here I focus on the cite journal template that is
primarily used for citation to articles in scientific journals. These citations
can be extracted and analyzed: Non-negative matrix factorization is performed
on a (article x journal) matrix resulting in a soft clustering of Wikipedia
articles and scientific journals, each cluster more or less representing a
scientific topic.
|
0805.1209
|
Scaling Laws for Overlaid Wireless Networks: A Cognitive Radio Network
vs. a Primary Network
|
cs.IT cs.NI math.IT
|
We study the scaling laws for the throughputs and delays of two coexisting
wireless networks that operate in the same geographic region. The primary
network consists of Poisson distributed legacy users of density n, and the
secondary network consists of Poisson distributed cognitive users of density m,
with m>n. The primary users have a higher priority to access the spectrum
without particular considerations for the secondary users, while the secondary
users have to act conservatively in order to limit the interference to the
primary users. With a practical assumption that the secondary users only know
the locations of the primary transmitters (not the primary receivers), we first
show that both networks can achieve the same throughput scaling law as what
Gupta and Kumar [1] established for a stand-alone wireless network if proper
transmission schemes are deployed, where a certain throughput is achievable for
each individual secondary user (i.e., zero outage) with high probability. By
using a fluid model, we also show that both networks can achieve the same
delay-throughput tradeoff as the optimal one established by El Gamal et al. [2]
for a stand-alone wireless network.
|
0805.1262
|
Optimal Node Density for Two-Dimensional Sensor Arrays
|
cs.IT math.IT
|
The problem of optimal node density for ad hoc sensor networks deployed for
making inferences about two dimensional correlated random fields is considered.
Using a symmetric first order conditional autoregressive Gauss-Markov random
field model, large deviations results are used to characterize the asymptotic
per-node information gained from the array. This result then allows an analysis
of the node density that maximizes the information under an energy constraint,
yielding insights into the trade-offs among the information, density and
energy.
|
0805.1288
|
Assessment of effective parameters on dilution using approximate
reasoning methods in longwall mining method, Iran coal mines
|
cs.AI
|
Approximately more than 90% of all coal production in Iranian underground
mines is derived directly longwall mining method. Out of seam dilution is one
of the essential problems in these mines. Therefore the dilution can impose the
additional cost of mining and milling. As a result, recognition of the
effective parameters on the dilution has a remarkable role in industry. In this
way, this paper has analyzed the influence of 13 parameters (attributed
variables) versus the decision attribute (dilution value), so that using two
approximate reasoning methods, namely Rough Set Theory (RST) and Self
Organizing Neuro- Fuzzy Inference System (SONFIS) the best rules on our
collected data sets has been extracted. The other benefit of later methods is
to predict new unknown cases. So, the reduced sets (reducts) by RST have been
obtained. Therefore the emerged results by utilizing mentioned methods shows
that the high sensitive variables are thickness of layer, length of stope, rate
of advance, number of miners, type of advancing.
|
0805.1296
|
A Simple Dynamic Mind-map Framework To Discover Associative
Relationships in Transactional Data Streams
|
cs.NE cs.SC
|
In this paper, we informally introduce dynamic mind-maps that represent a new
approach on the basis of a dynamic construction of connectionist structures
during the processing of a data stream. This allows the representation and
processing of recursively defined structures and avoids the problem of a more
traditional, fixed-size architecture with the processing of input structures of
unknown size. For a data stream analysis with association discovery, the
incremental analysis of data leads to results on demand. Here, we describe a
framework that uses symbolic cells to calculate associations based on
transactional data streams as it exists in e.g. bibliographic databases. We
follow a natural paradigm of applying simple operations on cells yielding on a
mind-map structure that adapts over time.
|
0805.1319
|
Emergence, Competition and Dynamical Stabilization of Dissipative
Rotating Spiral Waves in an Excitable Medium: A Computational Model Based on
Cellular Automata
|
nlin.CG cs.NE nlin.AO
|
We report some qualitatively new features of emergence, competition and
dynamical stabilization of dissipative rotating spiral waves (RSWs) in the
cellular-automaton model of laser-like excitable media proposed in
arXiv:cond-mat/0410460v2 ; arXiv:cond-mat/0602345 . Part of the observed
features are caused by unusual mechanism of excitation vorticity when the RSW's
core get into the surface layer of an active medium. Instead of the well known
scenario of RSW collapse, which takes place after collision of RSW's core with
absorbing boundary, we observed complicated transformations of the core leading
to regeneration (nonlinear "reflection" from the boundary) of the RSW or even
to birth of several new RSWs in the surface layer. Computer experiments on
bottlenecked evolution of such the RSW-ensembles (vortex matter) are reported
and a possible explanation of real experiments on spin-lattice relaxation in
dilute paramagnets is proposed on the basis of an analysis of the RSWs
dynamics. Chimera states in RSW-ensembles are revealed and compared with
analogous states in ensembles of nonlocally coupled oscillators. Generally, our
computer experiments have shown that vortex matter states in laser-like
excitable media have some important features of aggregate states of the usual
matter.
|
0805.1327
|
Bit-Interleaved Coded Modulation Revisited: A Mismatched Decoding
Perspective
|
cs.IT math.IT
|
We revisit the information-theoretic analysis of bit-interleaved coded
modulation (BICM) by modeling the BICM decoder as a mismatched decoder. The
mismatched decoding model is well-defined for finite, yet arbitrary, block
lengths, and naturally captures the channel memory among the bits belonging to
the same symbol. We give two independent proofs of the achievability of the
BICM capacity calculated by Caire et al. where BICM was modeled as a set of
independent parallel binary-input channels whose output is the bitwise
log-likelihood ratio. Our first achievability proof uses typical sequences, and
shows that due to the random coding construction, the interleaver is not
required. The second proof is based on the random coding error exponents with
mismatched decoding, where the largest achievable rate is the generalized
mutual information. We show that the generalized mutual information of the
mismatched decoder coincides with the infinite-interleaver BICM capacity. We
also show that the error exponent -and hence the cutoff rate- of the BICM
mismatched decoder is upper bounded by that of coded modulation and may thus be
lower than in the infinite-interleaved model. We also consider the mutual
information appearing in the analysis of iterative decoding of BICM with EXIT
charts. We show that the corresponding symbol metric has knowledge of the
transmitted symbol and the EXIT mutual information admits a representation as a
pseudo-generalized mutual information, which is in general not achievable. A
different symbol decoding metric, for which the extrinsic side information
refers to the hypothesized symbol, induces a generalized mutual information
lower than the coded modulation capacity.
|
0805.1340
|
On the Secure Degrees of Freedom in the K-User Gaussian Interference
Channel
|
cs.IT math.IT
|
This paper studies the K-user Gaussian interference channel with secrecy
constraints. Two distinct network models, namely the interference channel with
confidential messages and the one with an external eavesdropper, are analyzed.
Using interference alignment along with secrecy pre-coding at each transmitter,
it is shown that each user in the network can achieve non-zero secure Degrees
of Freedoms (DoFs) in both scenarios. In particular, the proposed coding scheme
achieves (K-2)/(2K-2) secure DoFs for each user in the interference channel
with confidential messages model, and (K-2)/2K secure DoFs in the case of an
external eavesdropper. The fundamental difference between the two scenarios
stems from the lack of channel state information (CSI) about the external
eavesdropper. Remarkably, the results establish the positive impact of
interference on the secrecy capacity of wireless networks.
|
0805.1437
|
On the Spectrum of Large Random Hermitian Finite-Band Matrices
|
cs.IT math.IT
|
The open problem of calculating the limiting spectrum (or its Shannon
transform) of increasingly large random Hermitian finite-band matrices is
described. In general, these matrices include a finite number of non-zero
diagonals around their main diagonal regardless of their size. Two different
communication setups which may be modeled using such matrices are presented: a
simple cellular uplink channel, and a time varying inter-symbol interference
channel. Selected recent information-theoretic works dealing directly with such
channels are reviewed. Finally, several characteristics of the still unknown
limiting spectrum of such matrices are listed, and some reflections are touched
upon.
|
0805.1442
|
How Many Users should be Turned On in a Multi-Antenna Broadcast Channel?
|
cs.IT math.IT
|
This paper considers broadcast channels with L antennas at the base station
and m single-antenna users, where L and m are typically of the same order. We
assume that only partial channel state information is available at the base
station through a finite rate feedback. Our key observation is that the optimal
number of on-users (users turned on), say s, is a function of signal-to-noise
ratio (SNR) and feedback rate. In support of this, an asymptotic analysis is
employed where L, m and the feedback rate approach infinity linearly. We derive
the asymptotic optimal feedback strategy as well as a realistic criterion to
decide which users should be turned on. The corresponding asymptotic throughput
per antenna, which we define as the spatial efficiency, turns out to be a
function of the number of on-users s, and therefore s must be chosen
appropriately. Based on the asymptotics, a scheme is developed for systems with
finite many antennas and users. Compared with other studies in which s is
presumed constant, our scheme achieves a significant gain. Furthermore, our
analysis and scheme are valid for heterogeneous systems where different users
may have different path loss coefficients and feedback rates.
|
0805.1473
|
A Fast Algorithm and Datalog Inexpressibility for Temporal Reasoning
|
cs.AI cs.LO
|
We introduce a new tractable temporal constraint language, which strictly
contains the Ord-Horn language of Buerkert and Nebel and the class of AND/OR
precedence constraints. The algorithm we present for this language decides
whether a given set of constraints is consistent in time that is quadratic in
the input size. We also prove that (unlike Ord-Horn) this language cannot be
solved by Datalog or by establishing local consistency.
|
0805.1480
|
On-line Learning of an Unlearnable True Teacher through Mobile Ensemble
Teachers
|
cond-mat.dis-nn cs.LG
|
On-line learning of a hierarchical learning model is studied by a method from
statistical mechanics. In our model a student of a simple perceptron learns
from not a true teacher directly, but ensemble teachers who learn from the true
teacher with a perceptron learning rule. Since the true teacher and the
ensemble teachers are expressed as non-monotonic perceptron and simple ones,
respectively, the ensemble teachers go around the unlearnable true teacher with
the distance between them fixed in an asymptotic steady state. The
generalization performance of the student is shown to exceed that of the
ensemble teachers in a transient state, as was shown in similar
ensemble-teachers models. Further, it is found that moving the ensemble
teachers even in the steady state, in contrast to the fixed ensemble teachers,
is efficient for the performance of the student.
|
0805.1485
|
Distributed MIMO Systems with Oblivious Antennas
|
cs.IT math.IT
|
A scenario in which a single source communicates with a single destination
via a distributed MIMO transceiver is considered. The source operates each of
the transmit antennas via finite-capacity links, and likewise the destination
is connected to the receiving antennas through capacity-constrained channels.
Targeting a nomadic communication scenario, in which the distributed MIMO
transceiver is designed to serve different standards or services, transmitters
and receivers are assumed to be oblivious to the encoding functions shared by
source and destination. Adopting a Gaussian symmetric interference network as
the channel model (as for regularly placed transmitters and receivers),
achievable rates are investigated and compared with an upper bound. It is
concluded that in certain asymptotic and non-asymptotic regimes obliviousness
of transmitters and receivers does not cause any loss of optimality.
|
0805.1487
|
A Time Efficient Indexing Scheme for Complex Spatiotemporal Retrieval
|
cs.DB cs.DS
|
The paper is concerned with the time efficient processing of spatiotemporal
predicates, i.e. spatial predicates associated with an exact temporal
constraint. A set of such predicates forms a buffer query or a Spatio-temporal
Pattern (STP) Query with time. In the more general case of an STP query, the
temporal dimension is introduced via the relative order of the spatial
predicates (STP queries with order). Therefore, the efficient processing of a
spatiotemporal predicate is crucial for the efficient implementation of more
complex queries of practical interest. We propose an extension of a known
approach, suitable for processing spatial predicates, which has been used for
the efficient manipulation of STP queries with order. The extended method is
supported by efficient indexing structures. We also provide experimental
results that show the efficiency of the technique.
|
0805.1593
|
On the Probability Distribution of Superimposed Random Codes
|
cs.DB cs.DM cs.IT math.IT
|
A systematic study of the probability distribution of superimposed random
codes is presented through the use of generating functions. Special attention
is paid to the cases of either uniformly distributed but not necessarily
independent or non uniform but independent bit structures. Recommendations for
optimal coding strategies are derived.
|
0805.1662
|
Eliminating Trapping Sets in Low-Density Parity Check Codes by using
Tanner Graph Covers
|
cs.IT math.IT
|
We discuss error floor asympotics and present a method for improving the
performance of low-density parity check (LDPC) codes in the high SNR (error
floor) region.
The method is based on Tanner graph covers that do not have trapping sets
from the original code. The advantages of the method are that it is universal,
as it can be applied to any LDPC code/channel/decoding algorithm and it
improves performance at the expense of increasing the code length, without
losing the code regularity, without changing the decoding algorithm, and, under
certain conditions, without lowering the code rate. The proposed method can be
modified to construct convolutional LDPC codes also.
The method is illustrated by modifying Tanner, MacKay and Margulis codes to
improve performance on the binary symmetric channel (BSC) under the Gallager B
decoding algorithm. Decoding results on AWGN channel are also presented to
illustrate that optimizing codes for one channel/decoding algorithm can lead to
performance improvement on other channels.
|
0805.1696
|
Grammatical Evolution with Restarts for Fast Fractal Generation
|
cs.NE cs.SC
|
In a previous work, the authors proposed a Grammatical Evolution algorithm to
automatically generate Lindenmayer Systems which represent fractal curves with
a pre-determined fractal dimension. This paper gives strong statistical
evidence that the probability distributions of the execution time of that
algorithm exhibits a heavy tail with an hyperbolic probability decay for long
executions, which explains the erratic performance of different executions of
the algorithm. Three different restart strategies have been incorporated in the
algorithm to mitigate the problems associated to heavy tail distributions: the
first assumes full knowledge of the execution time probability distribution,
the second and third assume no knowledge. These strategies exploit the fact
that the probability of finding a solution in short executions is
non-negligible and yield a severe reduction, both in the expected execution
time (up to one order of magnitude) and in its variance, which is reduced from
an infinite to a finite value.
|
0805.1715
|
Isotropy, entropy, and energy scaling
|
cs.IT math.IT nlin.AO
|
Two principles explain emergence. First, in the Receipt's reference frame,
Deg(S) = 4/3 Deg(R), where Supply S is an isotropic radiative energy source,
Receipt R receives S's energy, and Deg is a system's degrees of freedom based
on its mean path length. S's 1/3 more degrees of freedom relative to R enables
R's growth and increasing complexity. Second, rho(R) = Deg(R) times rho(r),
where rho(R) represents the collective rate of R and rho(r) represents the rate
of an individual in R: as Deg(R) increases due to the first principle, the
multiplier effect of networking in R increases. A universe like ours with
isotropic energy distribution, in which both principles are operative, is
therefore predisposed to exhibit emergence, and, for reasons shown, a
ubiquitous role for the natural logarithm.
|
0805.1727
|
Swarm-Based Spatial Sorting
|
cs.AI cs.MA
|
Purpose: To present an algorithm for spatially sorting objects into an
annular structure. Design/Methodology/Approach: A swarm-based model that
requires only stochastic agent behaviour coupled with a pheromone-inspired
"attraction-repulsion" mechanism. Findings: The algorithm consistently
generates high-quality annular structures, and is particularly powerful in
situations where the initial configuration of objects is similar to those
observed in nature. Research limitations/implications: Experimental evidence
supports previous theoretical arguments about the nature and mechanism of
spatial sorting by insects. Practical implications: The algorithm may find
applications in distributed robotics. Originality/value: The model offers a
powerful minimal algorithmic framework, and also sheds further light on the
nature of attraction-repulsion algorithms and underlying natural processes.
|
0805.1785
|
Distributed Self Management for Distributed Security Systems
|
cs.MA cs.AI
|
Distributed system as e.g. artificial immune systems, complex adaptive
systems, or multi-agent systems are widely used in Computer Science, e.g. for
network security, optimisations, or simulations. In these systems, small
entities move through the network and perform certain tasks. At some time, the
entities move to another place and require therefore information where to move
is most profitable. Common used systems do not provide any information or use a
centralised approach where a center delegates the entities. This article
discusses whether small information about the neighbours enhances the
performance of the overall system or not. Therefore, two information-protocols
are introduced and analysed. In addition, the protocols are implemented and
tested using the artificial immune system SANA that protects a network against
intrusions.
|
0805.1786
|
Next Challenges in Bringing Artificial Immune Systems to Production in
Network Security
|
cs.MA cs.AI
|
The human immune system protects the human body against various pathogens
like e.g. biological viruses and bacteria. Artificial immune systems reuse the
architecture, organization, and workflows of the human immune system for
various problems in computer science. In the network security, the artificial
immune system is used to secure a network and its nodes against intrusions like
viruses, worms, and trojans. However, these approaches are far away from
production where they are academic proof-of-concept implementations or use only
a small part to protect against a certain intrusion. This article discusses the
required steps to bring artificial immune systems into production in the
network security domain. It furthermore figures out the challenges and provides
the description and results of the prototype of an artificial immune system,
which is SANA called.
|
0805.1787
|
A Network Protection Framework through Artificial Immunity
|
cs.MA cs.CR
|
Current network protection systems use a collection of intelligent components
- e.g. classifiers or rule-based firewall systems to detect intrusions and
anomalies and to secure a network against viruses, worms, or trojans. However,
these network systems rely on individuality and support an architecture with
less collaborative work of the protection components. They give less
administration support for maintenance, but offer a large number of individual
single points of failures - an ideal situation for network attacks to succeed.
In this work, we discuss the required features, the performance, and the
problems of a distributed protection system called {\it SANA}. It consists of a
cooperative architecture, it is motivated by the human immune system, where the
components correspond to artificial immune cells that are connected for their
collaborative work. SANA promises a better protection against intruders than
common known protection systems through an adaptive self-management while
keeping the resources efficiently by an intelligent reduction of redundancies.
We introduce a library of several novel and common used protection components
and evaluate the performance of SANA by a proof-of-concept implementation.
|
0805.1788
|
Pedestrian Flow at Bottlenecks - Validation and Calibration of Vissim's
Social Force Model of Pedestrian Traffic and its Empirical Foundations
|
cs.MA physics.soc-ph
|
In this contribution first results of experiments on pedestrian flow through
bottlenecks are presented and then compared to simulation results obtained with
the Social Force Model in the Vissim simulation framework. Concerning the
experiments it is argued that the basic dependence between flow and bottleneck
width is not a step function but that it is linear and modified by the effect
of a psychological phenomenon. The simulation results as well show a linear
dependence and the parameters can be calibrated such that the absolute values
for flow and time fit to range of experimental results.
|
0805.1806
|
Tuplix Calculus Specifications of Financial Transfer Networks
|
cs.CE cs.LO
|
We study the application of Tuplix Calculus in modular financial budget
design. We formalize organizational structure using financial transfer
networks. We consider the notion of flux of money over a network, and a way to
enforce the matching of influx and outflux for parts of a network. We exploit
so-called signed attribute notation to make internal streams visible through
encapsulations. Finally, we propose a Tuplix Calculus construct for the
definition of data functions.
|
0805.1827
|
Parallel Pricing Algorithms for Multi--Dimensional Bermudan/American
Options using Monte Carlo methods
|
cs.DC cs.CE
|
In this paper we present two parallel Monte Carlo based algorithms for
pricing multi--dimensional Bermudan/American options. First approach relies on
computation of the optimal exercise boundary while the second relies on
classification of continuation and exercise values. We also evaluate the
performance of both the algorithms in a desktop grid environment. We show the
effectiveness of the proposed approaches in a heterogeneous computing
environment, and identify scalability constraints due to the algorithmic
structure.
|
0805.1844
|
Practical recipes for the model order reduction, dynamical simulation,
and compressive sampling of large-scale open quantum systems
|
quant-ph cs.IT math.IT math.NA
|
This article presents numerical recipes for simulating high-temperature and
non-equilibrium quantum spin systems that are continuously measured and
controlled. The notion of a spin system is broadly conceived, in order to
encompass macroscopic test masses as the limiting case of large-j spins. The
simulation technique has three stages: first the deliberate introduction of
noise into the simulation, then the conversion of that noise into an equivalent
continuous measurement and control process, and finally, projection of the
trajectory onto a state-space manifold having reduced dimensionality and
possessing a Kahler potential of multi-linear form. The resulting simulation
formalism is used to construct a positive P-representation for the thermal
density matrix. Single-spin detection by magnetic resonance force microscopy
(MRFM) is simulated, and the data statistics are shown to be those of a random
telegraph signal with additive white noise. Larger-scale spin-dust models are
simulated, having no spatial symmetry and no spatial ordering; the
high-fidelity projection of numerically computed quantum trajectories onto
low-dimensionality Kahler state-space manifolds is demonstrated. The
reconstruction of quantum trajectories from sparse random projections is
demonstrated, the onset of Donoho-Stodden breakdown at the Candes-Tao sparsity
limit is observed, a deterministic construction for sampling matrices is given,
and methods for quantum state optimization by Dantzig selection are given.
|
0805.1854
|
A New Algorithm for Interactive Structural Image Segmentation
|
cs.CV
|
This paper proposes a novel algorithm for the problem of structural image
segmentation through an interactive model-based approach. Interaction is
expressed in the model creation, which is done according to user traces drawn
over a given input image. Both model and input are then represented by means of
attributed relational graphs derived on the fly. Appearance features are taken
into account as object attributes and structural properties are expressed as
relational attributes. To cope with possible topological differences between
both graphs, a new structure called the deformation graph is introduced. The
segmentation process corresponds to finding a labelling of the input graph that
minimizes the deformations introduced in the model when it is updated with
input information. This approach has shown to be faster than other segmentation
methods, with competitive output quality. Therefore, the method solves the
problem of multiple label segmentation in an efficient way. Encouraging results
on both natural and target-specific color images, as well as examples showing
the reusability of the model, are presented and discussed.
|
0805.1857
|
The Gaussian Many-Help-One Distributed Source Coding Problem
|
cs.IT math.IT
|
Jointly Gaussian memoryless sources are observed at N distinct terminals. The
goal is to efficiently encode the observations in a distributed fashion so as
to enable reconstruction of any one of the observations, say the first one, at
the decoder subject to a quadratic fidelity criterion. Our main result is a
precise characterization of the rate-distortion region when the covariance
matrix of the sources satisfies a "tree-structure" condition. In this
situation, a natural analog-digital separation scheme optimally trades off the
distributed quantization rate tuples and the distortion in the reconstruction:
each encoder consists of a point-to-point Gaussian vector quantizer followed by
a Slepian-Wolf binning encoder. We also provide a partial converse that
suggests that the tree structure condition is fundamental.
|
0805.2027
|
Rollout Sampling Approximate Policy Iteration
|
cs.LG cs.AI cs.CC
|
Several researchers have recently investigated the connection between
reinforcement learning and classification. We are motivated by proposals of
approximate policy iteration schemes without value functions which focus on
policy representation using classifiers and address policy learning as a
supervised learning problem. This paper proposes variants of an improved policy
iteration scheme which addresses the core sampling problem in evaluating a
policy through simulation as a multi-armed bandit machine. The resulting
algorithm offers comparable performance to the previous algorithm achieved,
however, with significantly less computational effort. An order of magnitude
improvement is demonstrated experimentally in two standard reinforcement
learning domains: inverted pendulum and mountain-car.
|
0805.2045
|
Semantic Analysis of Tag Similarity Measures in Collaborative Tagging
Systems
|
cs.DL cs.IR
|
Social bookmarking systems allow users to organise collections of resources
on the Web in a collaborative fashion. The increasing popularity of these
systems as well as first insights into their emergent semantics have made them
relevant to disciplines like knowledge extraction and ontology learning. The
problem of devising methods to measure the semantic relatedness between tags
and characterizing it semantically is still largely open. Here we analyze three
measures of tag relatedness: tag co-occurrence, cosine similarity of
co-occurrence distributions, and FolkRank, an adaptation of the PageRank
algorithm to folksonomies. Each measure is computed on tags from a large-scale
dataset crawled from the social bookmarking system del.icio.us. To provide a
semantic grounding of our findings, a connection to WordNet (a semantic lexicon
for the English language) is established by mapping tags into synonym sets of
WordNet, and applying there well-known metrics of semantic similarity. Our
results clearly expose different characteristics of the selected measures of
relatedness, making them applicable to different subtasks of knowledge
extraction such as synonym detection or discovery of concept hierarchies.
|
0805.2105
|
On Emergence of Dominating Cliques in Random Graphs
|
math.CO cs.IT math.IT
|
Emergence of dominating cliques in Erd\"os-R\'enyi random graph model
${\bbbg(n,p)}$ is investigated in this paper. It is shown this phenomenon
possesses a phase transition. Namely, we have argued that, given a constant
probability $p$, an $n$-node random graph $G$ from ${\bbbg(n,p)}$ and for $r= c
\log_{1/p} n$ with $1 \leq c \leq 2$, it holds: (1) if $p > 1/2$ then an
$r$-node clique is dominating in $G$ almost surely and, (2) if $p \leq (3 -
\sqrt{5})/2$ then an $r$-node clique is not dominating in $G$ almost surely.
The remaining range of probability $p$ is discussed with more attention. A
detailed study shows that this problem is answered by examination of
sub-logarithmic growth of $r$ upon $n$.
|
0805.2185
|
Path Diversity over Packet Switched Networks: Performance Analysis and
Rate Allocation
|
cs.NI cs.IT math.IT
|
Path diversity works by setting up multiple parallel connections between the
end points using the topological path redundancy of the network. In this paper,
\textit{Forward Error Correction} (FEC) is applied across multiple independent
paths to enhance the end-to-end reliability. Network paths are modeled as
erasure Gilbert-Elliot channels. It is known that over any erasure channel,
\textit{Maximum Distance Separable} (MDS) codes achieve the minimum probability
of irrecoverable loss among all block codes of the same size. Based on the
adopted model for the error behavior, we prove that the probability of
irrecoverable loss for MDS codes decays exponentially for an asymptotically
large number of paths. Then, optimal rate allocation problem is solved for the
asymptotic case where the number of paths is large. Moreover, it is shown that
in such asymptotically optimal rate allocation, each path is assigned a
positive rate \textit{iff} its quality is above a certain threshold. The
quality of a path is defined as the percentage of the time it spends in the bad
state. Finally, using dynamic programming, a heuristic suboptimal algorithm
with polynomial runtime is proposed for rate allocation over a finite number of
paths. This algorithm converges to the asymptotically optimal rate allocation
when the number of paths is large. The simulation results show that the
proposed algorithm approximates the optimal rate allocation (found by
exhaustive search) very closely for practical number of paths, and provides
significant performance improvement compared to the alternative schemes of rate
allocation.
|
0805.2199
|
Constraint Complexity of Realizations of Linear Codes on Arbitrary
Graphs
|
cs.DM cs.IT math.IT
|
A graphical realization of a linear code C consists of an assignment of the
coordinates of C to the vertices of a graph, along with a specification of
linear state spaces and linear ``local constraint'' codes to be associated with
the edges and vertices, respectively, of the graph. The $\k$-complexity of a
graphical realization is defined to be the largest dimension of any of its
local constraint codes. $\k$-complexity is a reasonable measure of the
computational complexity of a sum-product decoding algorithm specified by a
graphical realization. The main focus of this paper is on the following
problem: given a linear code C and a graph G, how small can the $\k$-complexity
of a realization of C on G be? As useful tools for attacking this problem, we
introduce the Vertex-Cut Bound, and the notion of ``vc-treewidth'' for a graph,
which is closely related to the well-known graph-theoretic notion of treewidth.
Using these tools, we derive tight lower bounds on the $\k$-complexity of any
realization of C on G. Our bounds enable us to conclude that good
error-correcting codes can have low-complexity realizations only on graphs with
large vc-treewidth. Along the way, we also prove the interesting result that
the ratio of the $\k$-complexity of the best conventional trellis realization
of a length-n code C to the $\k$-complexity of the best cycle-free realization
of C grows at most logarithmically with codelength n. Such a logarithmic growth
rate is, in fact, achievable.
|
0805.2303
|
Graph Algorithms for Improving Type-Logical Proof Search
|
cs.CL
|
Proof nets are a graph theoretical representation of proofs in various
fragments of type-logical grammar. In spite of this basis in graph theory,
there has been relatively little attention to the use of graph theoretic
algorithms for type-logical proof search. In this paper we will look at several
ways in which standard graph theoretic algorithms can be used to restrict the
search space. In particular, we will provide an O(n4) algorithm for selecting
an optimal axiom link at any stage in the proof search as well as a O(kn3)
algorithm for selecting the k best proof candidates.
|
0805.2308
|
Toward Fuzzy block theory
|
cs.AI
|
This study, fundamentals of fuzzy block theory, and its application in
assessment of stability in underground openings, has surveyed. Using fuzzy
topics and inserting them in to key block theory, in two ways, fundamentals of
fuzzy block theory has been presented. In indirect combining, by coupling of
adaptive Neuro Fuzzy Inference System (NFIS) and classic block theory, we could
extract possible damage parts around a tunnel. In direct solution, some
principles of block theory, by means of different fuzzy facets theory, were
rewritten.
|
0805.2324
|
A multilateral filtering method applied to airplane runway image
|
cs.CV
|
By considering the features of the airport runway image filtering, an
improved bilateral filtering method was proposed which can remove noise with
edge preserving. Firstly the steerable filtering decomposition is used to
calculate the sub-band parameters of 4 orients, and the texture feature matrix
is then obtained from the sub-band local median energy. The texture similar,
the spatial closer and the color similar functions are used to filter the
image.The effect of the weighting function parameters is qualitatively analyzed
also. In contrast with the standard bilateral filter and the simulation results
for the real airport runway image show that the multilateral filtering is more
effective than the standard bilateral filtering.
|
0805.2362
|
An optimization problem on the sphere
|
cs.LG cs.CG
|
We prove existence and uniqueness of the minimizer for the average geodesic
distance to the points of a geodesically convex set on the sphere. This implies
a corresponding existence and uniqueness result for an optimal algorithm for
halfspace learning, when data and target functions are drawn from the uniform
distribution.
|
0805.2368
|
A Kernel Method for the Two-Sample Problem
|
cs.LG cs.AI
|
We propose a framework for analyzing and comparing distributions, allowing us
to design statistical tests to determine if two samples are drawn from
different distributions. Our test statistic is the largest difference in
expectations over functions in the unit ball of a reproducing kernel Hilbert
space (RKHS). We present two tests based on large deviation bounds for the test
statistic, while a third is based on the asymptotic distribution of this
statistic. The test statistic can be computed in quadratic time, although
efficient linear time approximations are available. Several classical metrics
on distributions are recovered when the function space used to compute the
difference in expectations is allowed to be more general (eg. a Banach space).
We apply our two-sample tests to a variety of problems, including attribute
matching for databases using the Hungarian marriage method, where they perform
strongly. Excellent performance is also obtained when comparing distributions
over graphs, for which these are the first such tests.
|
0805.2379
|
Linear code-based vector quantization for independent random variables
|
cs.IT math.IT
|
In this paper we analyze the rate-distortion function R(D) achievable using
linear codes over GF(q), where q is a prime number.
|
0805.2422
|
Transceiver Pair Designs for Multiple Access Channels under Fixed Sum
Mutual Information using MMSE Decision Feedback Detection
|
cs.IT math.IT
|
In this paper, we consider the joint design of the transceivers for a
multiple access Multiple Input and Multiple Output (MIMO) system having
Inter-Symbol Interference (ISI) channels. The system we consider is equipped
with the Minimum Mean Square Error (MMSE) Decision-Feedback (DF) detector.
Traditionally, transmitter designs for this system have been based on
constraints of either the transmission power or the
signal-to-interference-and-noise ratio (SINR) for each user. Here, we explore a
novel perspective and examine a transceiver design which is based on a fixed
sum mutual information constraint and minimizes the arithmetic average of mean
square error of MMSE-decision feedback detection. For this optimization
problem, a closed-form solution is obtained and is achieved if and only if the
averaged sum mutual information is uniformly distributed over each active
subchannel. Meanwhile, the mutual information of the currently detected user is
uniformly distributed over each individual symbol within the block signal of
the user, assuming all the previous user signals have been perfectly detected.
|
0805.2423
|
Green Codes: Energy-Efficient Short-Range Communication
|
cs.IT math.IT
|
A green code attempts to minimize the total energy per-bit required to
communicate across a noisy channel. The classical information-theoretic
approach neglects the energy expended in processing the data at the encoder and
the decoder and only minimizes the energy required for transmissions. Since
there is no cost associated with using more degrees of freedom, the
traditionally optimal strategy is to communicate at rate zero.
In this work, we use our recently proposed model for the power consumed by
iterative message passing. Using generalized sphere-packing bounds on the
decoding power, we find lower bounds on the total energy consumed in the
transmissions and the decoding, allowing for freedom in the choice of the rate.
We show that contrary to the classical intuition, the rate for green codes is
bounded away from zero for any given error probability. In fact, as the desired
bit-error probability goes to zero, the optimizing rate for our bounds
converges to 1.
|
0805.2427
|
On Trapping Sets and Guaranteed Error Correction Capability of LDPC
Codes and GLDPC Codes
|
cs.IT math.IT
|
The relation between the girth and the guaranteed error correction capability
of $\gamma$-left regular LDPC codes when decoded using the bit flipping (serial
and parallel) algorithms is investigated. A lower bound on the size of variable
node sets which expand by a factor of at least $3 \gamma/4$ is found based on
the Moore bound. An upper bound on the guaranteed error correction capability
is established by studying the sizes of smallest possible trapping sets. The
results are extended to generalized LDPC codes. It is shown that generalized
LDPC codes can correct a linear fraction of errors under the parallel bit
flipping algorithm when the underlying Tanner graph is a good expander. It is
also shown that the bound cannot be improved when $\gamma$ is even by studying
a class of trapping sets. A lower bound on the size of variable node sets which
have the required expansion is established.
|
0805.2440
|
Analysis of hydrocyclone performance based on information granulation
theory
|
cs.AI
|
This paper describes application of information granulation theory, on the
analysis of hydrocyclone perforamance. In this manner, using a combining of
Self Organizing Map (SOM) and Neuro-Fuzzy Inference System (NFIS), crisp and
fuzzy granules are obtained(briefly called SONFIS). Balancing of crisp granules
and sub fuzzy granules, within non fuzzy information (initial granulation), is
rendered in an open-close iteration. Using two criteria, "simplicity of rules
"and "adaptive threoshold error level", stability of algorithm is guaranteed.
Validation of the proposed method, on the data set of the hydrocyclone is
rendered.
|
0805.2537
|
A toolkit for a generative lexicon
|
cs.CL
|
In this paper we describe the conception of a software toolkit designed for
the construction, maintenance and collaborative use of a Generative Lexicon. In
order to ease its portability and spreading use, this tool was built with free
and open source products. We eventually tested the toolkit and showed it
filters the adequate form of anaphoric reference to the modifier in endocentric
compounds.
|
0805.2629
|
On Full Diversity Space-Time Block Codes with Partial Interference
Cancellation Group Decoding
|
cs.IT math.IT
|
In this paper, we propose a partial interference cancellation (PIC) group
decoding for linear dispersive space-time block codes (STBC) and a design
criterion for the codes to achieve full diversity when the PIC group decoding
is used at the receiver. A PIC group decoding decodes the symbols embedded in
an STBC by dividing them into several groups and decoding each group separately
after a linear PIC operation is implemented. It can be viewed as an
intermediate decoding between the maximum likelihood (ML) receiver that decodes
all the embedded symbols together, i.e., all the embedded symbols are in a
single group, and the zero-forcing (ZF) receiver that decodes all the embedded
symbols separately and independently, i.e., each group has and only has one
embedded symbol, after the ZF operation is implemented. Our proposed design
criterion for the PIC group decoding to achieve full diversity is an
intermediate condition between the loosest ML full rank criterion of codewords
and the strongest ZF linear independence condition of the column vectors in the
equivalent channel matrix. We also propose asymptotically optimal (AO) group
decoding algorithm, which is an intermediate decoding between the MMSE decoding
algorithm and the ML decoding algorithm. The design criterion for the PIC group
decoding applies to the AO group decoding algorithm. It is well-known that the
symbol rate for a full rank linear STBC can be full, i.e., n_t for n_t transmit
antennas. It has been recently shown that its rate is upper bounded by 1 if a
code achieves full diversity with a linear receiver. The intermediate criterion
proposed in this paper provides the possibility for codes of rates between n_t
and 1 that achieve full diversity with a PIC group decoding. This therefore
provides a complexity-performance-rate tradeoff.
|
0805.2641
|
On the Capacity of the Diamond Half-Duplex Relay Channel
|
cs.IT math.IT
|
We consider a diamond-shaped dual-hop communication system consisting a
source, two parallel half-duplex relays and a destination. In a single antenna
configuration, it has been previously shown that a two-phase node-scheduling
algorithm, along with the decode and forward strategy can achieve the capacity
of the diamond channel for a certain symmetric channel gains [1]. In this
paper, we obtain a more general condition for the optimality of the scheme in
terms of power resources and channel gains. In particular, it is proved that if
the product of the capacity of the simultaneously active links are equal in
both transmission phases, the scheme achieves the capacity of the channel.
|
0805.2671
|
Finger Indexed Sets: New Approaches
|
cs.DS cs.DB
|
In the particular case we have insertions/deletions at the tail of a given
set S of $n$ one-dimensional elements, we present a simpler and more concrete
algorithm than that presented in [Anderson, 2007] achieving the same (but also
amortized) upper bound of $O(\sqrt{logd/loglogd})$ for finger searching
queries, where $d$ is the number of sorted keys between the finger element and
the target element we are looking for. Furthermore, in general case we have
insertions/deletions anywhere we present a new randomized algorithm achieving
the same expected time bounds. Even the new solutions achieve the optimal
bounds in amortized or expected case, the advantage of simplicity is of great
importance due to practical merits we gain.
|
0805.2690
|
Increasing Linear Dynamic Range of Commercial Digital Photocamera Used
in Imaging Systems with Optical Coding
|
cs.CV
|
Methods of increasing linear optical dynamic range of commercial photocamera
for optical-digital imaging systems are described. Use of such methods allows
to use commercial photocameras for optical measurements. Experimental results
are reported.
|
0805.2691
|
Equivalent characterizations of partial randomness for a recursively
enumerable real
|
cs.IT cs.CC math.IT math.LO
|
A real number \alpha is called recursively enumerable if there exists a
computable, increasing sequence of rational numbers which converges to \alpha.
The randomness of a recursively enumerable real \alpha can be characterized in
various ways using each of the notions; program-size complexity, Martin-L\"{o}f
test, Chaitin's \Omega number, the domination and \Omega-likeness of \alpha,
the universality of a computable, increasing sequence of rational numbers which
converges to \alpha, and universal probability. In this paper, we generalize
these characterizations of randomness over the notion of partial randomness by
parameterizing each of the notions above by a real number T\in(0,1]. We thus
present several equivalent characterizations of partial randomness for a
recursively enumerable real number.
|
0805.2752
|
The Margitron: A Generalised Perceptron with Margin
|
cs.LG
|
We identify the classical Perceptron algorithm with margin as a member of a
broader family of large margin classifiers which we collectively call the
Margitron. The Margitron, (despite its) sharing the same update rule with the
Perceptron, is shown in an incremental setting to converge in a finite number
of updates to solutions possessing any desirable fraction of the maximum
margin. Experiments comparing the Margitron with decomposition SVMs on tasks
involving linear kernels and 2-norm soft margin are also reported.
|
0805.2775
|
Sample Selection Bias Correction Theory
|
cs.LG
|
This paper presents a theoretical analysis of sample selection bias
correction. The sample bias correction technique commonly used in machine
learning consists of reweighting the cost of an error on each training point of
a biased sample to more closely reflect the unbiased distribution. This relies
on weights derived by various estimation techniques based on finite samples. We
analyze the effect of an error in that estimation on the accuracy of the
hypothesis returned by the learning algorithm for two estimation techniques: a
cluster-based estimation technique and kernel mean matching. We also report the
results of sample bias correction experiments with several data sets using
these techniques. Our analysis is based on the novel concept of distributional
stability which generalizes the existing concept of point-based stability. Much
of our work and proof techniques can be used to analyze other importance
weighting techniques and their effect on accuracy when using a distributionally
stable algorithm.
|
0805.2812
|
Codeword-Independent Performance of Nonbinary Linear Codes Under
Linear-Programming and Sum-Product Decoding
|
cs.IT math.IT
|
A coded modulation system is considered in which nonbinary coded symbols are
mapped directly to nonbinary modulation signals. It is proved that if the
modulator-channel combination satisfies a particular symmetry condition, the
codeword error rate performance is independent of the transmitted codeword. It
is shown that this result holds for both linear-programming decoders and
sum-product decoders. In particular, this provides a natural modulation mapping
for nonbinary codes mapped to PSK constellations for transmission over
memoryless channels such as AWGN channels or flat fading channels with AWGN.
|
0805.2855
|
LCSH, SKOS and Linked Data
|
cs.DL cs.IR
|
A technique for converting Library of Congress Subject Headings MARCXML to
Simple Knowledge Organization System (SKOS) RDF is described. Strengths of the
SKOS vocabulary are highlighted, as well as possible points for extension, and
the integration of other semantic web vocabularies such as Dublin Core. An
application for making the vocabulary available as linked-data on the Web is
also described.
|
0805.2891
|
Learning Low-Density Separators
|
cs.LG cs.AI
|
We define a novel, basic, unsupervised learning problem - learning the lowest
density homogeneous hyperplane separator of an unknown probability
distribution. This task is relevant to several problems in machine learning,
such as semi-supervised learning and clustering stability. We investigate the
question of existence of a universally consistent algorithm for this problem.
We propose two natural learning paradigms and prove that, on input unlabeled
random samples generated by any member of a rich family of distributions, they
are guaranteed to converge to the optimal separator for that distribution. We
complement this result by showing that no learning algorithm for our task can
achieve uniform learning rates (that are independent of the data generating
distribution).
|
0805.2949
|
Performability Aspects of the Atlas Vo; Using Lmbench Suite
|
cs.PF cs.CE cs.DC
|
The ATLAS Virtual Organization is grid's largest Virtual Organization which
is currently in full production stage. Hereby a case is being made that a user
working within that VO is going to face a wide spectrum of different systems,
whose heterogeneity is enough to count as "orders of magnitude" according to a
number of metrics; including integer/float operations, memory throughput
(STREAM) and communication latencies. Furthermore, the spread of performance
does not appear to follow any known distribution pattern, which is demonstrated
in graphs produced during May 2007 measurements. It is implied that the current
practice where either "all-WNs-are-equal" or, the alternative of SPEC-based
rating used by LCG/EGEE is an oversimplification which is inappropriate and
expensive from an operational point of view, therefore new techniques are
needed for optimal grid resources allocation.
|
0805.2995
|
Lossless Compression with Security Constraints
|
cs.IT math.IT
|
Secure distributed data compression in the presence of an eavesdropper is
explored. Two correlated sources that need to be reliably transmitted to a
legitimate receiver are available at separate encoders. Noise-free, limited
rate links from the encoders to the legitimate receiver, one of which can also
be perfectly observed by the eavesdropper, are considered. The eavesdropper
also has its own correlated observation. Inner and outer bounds on the
achievable compression-equivocation rate region are given. Several different
scenarios involving the side information at the transmitters as well as
multiple receivers/eavesdroppers are also considered.
|
0805.2996
|
Lossy Source Transmission over the Relay Channel
|
cs.IT math.IT
|
Lossy transmission over a relay channel in which the relay has access to
correlated side information is considered. First, a joint source-channel
decode-and-forward scheme is proposed for general discrete memoryless sources
and channels. Then the Gaussian relay channel where the source and the side
information are jointly Gaussian is analyzed. For this Gaussian model, several
new source-channel cooperation schemes are introduced and analyzed in terms of
the squared-error distortion at the destination. A comparison of the proposed
upper bounds with the cut-set lower bound is given, and it is seen that joint
source-channel cooperation improves the reconstruction quality significantly.
Moreover, the performance of the joint code is close to the lower bound on
distortion for a wide range of source and channel parameters.
|
0805.3005
|
High-dimensional subset recovery in noise: Sparsified measurements
without loss of statistical efficiency
|
stat.ML cs.IT math.IT
|
We consider the problem of estimating the support of a vector $\beta^* \in
\mathbb{R}^{p}$ based on observations contaminated by noise. A significant body
of work has studied behavior of $\ell_1$-relaxations when applied to
measurement matrices drawn from standard dense ensembles (e.g., Gaussian,
Bernoulli). In this paper, we analyze \emph{sparsified} measurement ensembles,
and consider the trade-off between measurement sparsity, as measured by the
fraction $\gamma$ of non-zero entries, and the statistical efficiency, as
measured by the minimal number of observations $n$ required for exact support
recovery with probability converging to one. Our main result is to prove that
it is possible to let $\gamma \to 0$ at some rate, yielding measurement
matrices with a vanishing fraction of non-zeros per row while retaining the
same statistical efficiency as dense ensembles. A variety of simulation results
confirm the sharpness of our theoretical predictions.
|
0805.3082
|
Weakly Convergent Nonparametric Forecasting of Stationary Time Series
|
math.ST cs.IT math.IT stat.TH
|
The conditional distribution of the next outcome given the infinite past of a
stationary process can be inferred from finite but growing segments of the
past. Several schemes are known for constructing pointwise consistent
estimates, but they all demand prohibitive amounts of input data. In this paper
we consider real-valued time series and construct conditional distribution
estimates that make much more efficient use of the input data. The estimates
are consistent in a weak sense, and the question whether they are pointwise
consistent is still open. For finite-alphabet processes one may rely on a
universal data compression scheme like the Lempel-Ziv algorithm to construct
conditional probability mass function estimates that are consistent in expected
information divergence. Consistency in this strong sense cannot be attained in
a universal sense for all stationary processes with values in an infinite
alphabet, but weak consistency can. Some applications of the estimates to
on-line forecasting, regression and classification are discussed.
|
0805.3091
|
A simple randomized algorithm for sequential prediction of ergodic time
series
|
math.ST cs.IT math.IT stat.TH
|
We present a simple randomized procedure for the prediction of a binary
sequence. The algorithm uses ideas from recent developments of the theory of
the prediction of individual sequences. We show that if the sequence is a
realization of a stationary and ergodic random process then the average number
of mistakes converges, almost surely, to that of the optimum, given by the
Bayes predictor. The desirable finite-sample properties of the predictor are
illustrated by its performance for Markov processes. In such cases the
predictor exhibits near optimal behavior even without knowing the order of the
Markov process. Prediction with side information is also considered.
|
0805.3118
|
Full Diversity Blind Signal Designs for Unique Identification of
Frequency Selective Channels
|
cs.IT math.IT
|
In this paper, we develop two kinds of novel closed-form decompositions on
phase shift keying (PSK) constellations by exploiting linear congruence
equation theory: the one for factorizing a $pq$-PSK constellation into a
product of a $p$-PSK constellation and a $q$-PSK constellation, and the other
for decomposing a specific complex number into a difference of a $p$-PSK
constellation and a $q$-PSK constellation. With this, we propose a simple
signal design technique to blindly and uniquely identify frequency selective
channels with zero-padded block transmission under noise-free environments by
only using the first two block received signal vectors. Furthermore, a
closed-form solution to determine the transmitted signals and the channel
coefficients is obtained. In the Gaussian noise and Rayleigh fading
environment, we prove that the newly proposed signaling scheme enables
non-coherent full diversity for the Generalized Likelihood Ratio Test (GLRT)
receiver.
|
0805.3126
|
Cognitive Architecture for Direction of Attention Founded on Subliminal
Memory Searches, Pseudorandom and Nonstop
|
cs.AI cs.NE
|
By way of explaining how a brain works logically, human associative memory is
modeled with logical and memory neurons, corresponding to standard digital
circuits. The resulting cognitive architecture incorporates basic psychological
elements such as short term and long term memory. Novel to the architecture are
memory searches using cues chosen pseudorandomly from short term memory.
Recalls alternated with sensory images, many tens per second, are analyzed
subliminally as an ongoing process, to determine a direction of attention in
short term memory.
|
0805.3164
|
To Code or Not To Code in Multi-Hop Relay Channels
|
cs.IT math.IT
|
Multi-hop relay channels use multiple relay stages, each with multiple relay
nodes, to facilitate communication between a source and destination.
Previously, distributed space-time coding was used to maximize diversity gain.
Assuming a low-rate feedback link from the destination to each relay stage and
the source, this paper proposes end-to-end antenna selection strategies as an
alternative to distributed space-time coding. One-way (where only the source
has data for destination) and two-way (where the destination also has data for
the source) multi-hop relay channels are considered with both the full-duplex
and half duplex relay nodes. End-to-end antenna selection strategies are
designed and proven to achieve maximum diversity gain by using a single antenna
path (using single antenna of the source, each relay stage and the destination)
with the maximum signal-to-noise ratio at the destination. For the half-duplex
case, two single antenna paths with the two best signal-to-noise ratios in
alternate time slots are used to overcome the rate loss with half-duplex nodes,
with a small diversity gain penalty. Finally to answer the question, whether to
code (distributed space-time code) or not (the proposed end-to-end antenna
selection strategy) in a multi-hop relay channel, end-to-end antenna selection
strategy and distributed space-time coding is compared with respect to several
important performance metrics.
|
0805.3200
|
On Tightness of Mutual Dependence Upperbound for Secret-key Capacity of
Multiple Terminals
|
cs.IT cs.CR math.CO math.IT math.PR
|
Csiszar and Narayan[3] defined the notion of secret key capacity for multiple
terminals, characterized it as a linear program with Slepian-Wolf constraints
of the related source coding problem of communication for omniscience, and
upper bounded it by some information divergence expression from the joint to
the product distribution of the private observations. This paper proves that
the bound is tight for the important case when all users are active, using the
polymatroidal structure[6] underlying the source coding problem. When some
users are not active, the bound may not be tight. This paper gives a
counter-example in which 3 out of the 6 terminals are active.
|
0805.3206
|
Sociological Inequality and the Second Law
|
cs.IT math.IT
|
There are two fair ways to distribute particles in boxes. The first way is to
divide the particles equally between the boxes. The second way, which is
calculated here, is to score fairly the particles between the boxes. The
obtained power law distribution function yields an uneven distribution of
particles in boxes. It is shown that the obtained distribution fits well to
sociological phenomena, such as the distribution of votes in polls and the
distribution of wealth and Benford's law.
|
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