OpenRaiser/Intern-Atlas huggingface dataset:
Delay Constrained Throughput Analysis of a Correlated MIMO Wireless Channel
Venue: arXiv cs.NI 2011
Year: 2011

The maximum traffic arrival rate at the network for a given delay guarantee (delay constrained throughput) has been well studied for wired channels. However, few results are available for wireless channels, especially when multiple antennas are employed at the transmitter and receiver. In this work, we analyze the network delay constrained throughput of a multiple input multiple output (MIMO) wireless channel with time-varying spatial correlation. The MIMO channel is modeled via its virtual representation, where the individual spatial paths between the antenna pairs are Gilbert-Elliot channels. The whole system is then described by a K-State Markov chain, where K depends upon the degree of freedom (DOF) of the channel. We prove that the DOF based modeling is indeed accurate. Furthermore, we study the impact of the delay requirements at the network layer, violation probability and the number of antennas on the throughput under different fading speeds and signal strength.
Aspects of Nonabelian Group Based Cryptography: A Survey and Open Problems
Venue: arXiv cs.CR 2011
Year: 2011

Most common public key cryptosystems and public key exchange protocols presently in use, such as the RSA algorithm, Diffie-Hellman, and elliptic curve methods are number theory based and hence depend on the structure of abelian groups. The strength of computing machinery has made these techniques theoretically susceptible to attack and hence recently there has been an active line of research to develop cryptosystems and key exchange protocols using noncommutative cryptographic platforms. This line of investigation has been given the broad title of noncommutative algebraic cryptography. This was initiated by two public key protocols that used the braid groups, one by Ko, Lee et.al.and one by Anshel, Anshel and Goldfeld. The study of these protocols and the group theory surrounding them has had a large effect on research in infinite group theory. In this paper we survey these noncommutative group based methods and discuss several ideas in abstract infinite group theory that have arisen from them. We then present a set of open problems.
On Non-Bayesian Social Learning
Venue: arXiv cs.SI 2011
Year: 2011

We study a model of information aggregation and social learning recently proposed by Jadbabaie, Sandroni, and Tahbaz-Salehi, in which individual agents try to learn a correct state of the world by iteratively updating their beliefs using private observations and beliefs of their neighbors. No individual agent's private signal might be informative enough to reveal the unknown state. As a result, agents share their beliefs with others in their social neighborhood to learn from each other. At every time step each agent receives a private signal, and computes a Bayesian posterior as an intermediate belief. The intermediate belief is then averaged with the belief of neighbors to form the individual's belief at next time step. We find a set of minimal sufficient conditions under which the agents will learn the unknown state and reach consensus on their beliefs without any assumption on the private signal structure. The key enabler is a result that shows that using this update, agents will eventually forecast the indefinite future correctly.
Remarks on separating words
Venue: arXiv cs.FL 2011
Year: 2011

The separating words problem asks for the size of the smallest DFA needed to distinguish between two words of length <= n (by accepting one and rejecting the other). In this paper we survey what is known and unknown about the problem, consider some variations, and prove several new results.
Real Islamic Logic
Venue: arXiv cs.LO 2011
Year: 2011

Four options for assigning a meaning to Islamic Logic are surveyed including a new proposal for an option named "Real Islamic Logic" (RIL). That approach to Islamic Logic should serve modern Islamic objectives in a way comparable to the functionality of Islamic Finance. The prospective role of RIL is analyzed from several perspectives: (i) parallel distributed systems design, (ii) reception by a community structured audience, (iii) informal logic and applied non-classical logics, and (iv) (in)tractability and artificial intelligence.
Vector Broadcast Channels: Optimality of Threshold Feedback Policies
Venue: arXiv cs.IT 2011
Year: 2011

Beamforming techniques utilizing only partial channel state information (CSI) has gained popularity over other communication strategies requiring perfect CSI thanks to their lower feedback requirements. The amount of feedback in beamforming based communication systems can be further reduced through selective feedback techniques in which only the users with channels good enough are allowed to feed back by means of a decentralized feedback policy. In this paper, we prove that thresholding at the receiver is the rate-wise optimal decentralized feedback policy for feedback limited systems with prescribed feedback constraints. This result is highly adaptable due to its distribution independent nature, provides an analytical justification for the use of threshold feedback policies in practical systems, and reinforces previous work analyzing threshold feedback policies as a selective feedback technique without proving its optimality. It is robust to selfish unilateral deviations. Finally, it reduces the search for rate-wise optimal feedback policies subject to feedback constraints from function spaces to a finite dimensional Euclidean space.
Note on minimally k-connected graphs
Venue: arXiv cs.DM 2011
Year: 2011

A k-tree is either a complete graph on (k+1) vertices or given a k-tree G' with n vertices, a k-tree G with (n+1) vertices can be constructed by introducing a new vertex v and picking a k-clique Q in G' and then joining each vertex u in Q. A graph G is k-edge-connected if the graph remains connected even after deleting fewer edges than k from the graph. A k-edge-connected graph G is said to be minimally k-connected if G \ {e} is no longer k-edge-connected for any edge e belongs to E(G) where E(G) denotes the set of edges of G. In this paper we find two separate O (n2) algorithms so that a minimally 2-connected graph can be obtained from a 2-tree and a minimally k-connected graph can be obtained from a k-tree. In a k-tree (k \geq 2) we find the edges which are insensitive to the k-connectivity have both their end vertices of degrees greater than or equal to k+1.This property is fully exploited to find an algorithm which reduces any k-tree to a minimally k-connected graph.
Distributed Video Coding: Codec Architecture and Implementation
Venue: arXiv cs.MM 2011
Year: 2011

Distributed Video Coding (DVC) is a new coding paradigm for video compression, based on Slepian- Wolf (lossless coding) and Wyner-Ziv (lossy coding) information theoretic results. DVC is useful for emerging applications such as wireless video cameras, wireless low-power surveillance networks and disposable video cameras for medical applications etc. The primary objective of DVC is low-complexity video encoding, where bulk of computation is shifted to the decoder, as opposed to low-complexity decoder in conventional video compression standards such as H.264 and MPEG etc. There are couple of early architectures and implementations of DVC from Stanford University[2][3] in 2002, Berkeley University PRISM (Power-efficient, Robust, hIgh-compression, Syndrome-based Multimedia coding)[4][5] in 2002 and European project DISCOVER (DIStributed COding for Video SERvices)[6] in 2007. Primarily there are two types of DVC techniques namely pixel domain and transform domain based. Transform domain design will have better rate-distortion (RD) performance as it exploits spatial correlation between neighbouring samples and compacts the block energy into as few transform coefficients as possible (aka energy compaction). In this paper, architecture, implementation details and "C" model results of our transform domain DVC are presented.
High-Energy-First (HEF) Heuristic for Energy-Efficient Target Coverage Problem
Venue: arXiv cs.NI 2011
Year: 2011

Target coverage problem in wireless sensor networks is concerned with maximizing the lifetime of the network while continuously monitoring a set of targets. A sensor covers targets which are within the sensing range. For a set of sensors and a set of targets, the sensor-target coverage relationship is assumed to be known. A sensor cover is a set of sensors that covers all the targets. The target coverage problem is to determine a set of sensor covers with maximum aggregated lifetime while constraining the life of each sensor by its initial battery life. The problem is proved to be NP-complete and heuristic algorithms to solve this problem are proposed. In the present study, we give a unified interpretation of earlier algorithms and propose a new and efficient algorithm. We show that all known algorithms are based on a common reasoning though they seem to be derived from different algorithmic paradigms. We also show that though some algorithms guarantee bound on the quality of the solution, this bound is not meaningful and not practical too. Our interpretation provides a better insight to the solution techniques. We propose a new greedy heuristic which prioritizes sensors on residual battery life. We show empirically that the proposed algorithm outperforms all other heuristics in terms of quality of solution. Our experimental study over a large set of randomly generated problem instances also reveals that a very naïve greedy approach yields solutions which is reasonably (appx. 10%) close to the actual optimal solutions.
Robust Additively Coupled Games
Venue: arXiv cs.GT 2011
Year: 2011

We study the robust Nash equilibrium (RNE) for a class of games in communications systems and networks where the impact of users on each other is an additive function of their strategies. Each user measures this impact, which may be corrupted by uncertainty in feedback delays, estimation errors, movements of users, etc. To study the outcome of the game in which such uncertainties are encountered, we utilize the worst-case robust optimization theory. The existence and uniqueness conditions of RNE are derived using finite-dimensions variational inequalities. To describe the effect of uncertainty on the performance of the system, we use two criteria measured at the RNE and at the equilibrium of the game without uncertainty. The first is the difference between the respective social utility of users and, the second is the differences between the strategies of users at their respective equilibria. These differences are obtained for the case of a unique NE and multiple NEs. To reach the RNE, we propose a distributed algorithm based on the proximal response map and derive the conditions for its convergence. Simulations of the power control game in interference channels, and Jackson networks validate our analysis.
Cooperative searching for stochastic targets
Venue: arXiv cs.IT 2011
Year: 2011

Spatial search problems abound in the real world, from locating hidden nuclear or chemical sources to finding skiers after an avalanche. We exemplify the formalism and solution for spatial searches involving two agents that may or may not choose to share information during a search. For certain classes of tasks, sharing information between multiple searchers makes cooperative searching advantageous. In some examples, agents are able to realize synergy by aggregating information and moving based on local judgments about maximal information gathering expectations. We also explore one- and two-dimensional simplified situations analytically and numerically to provide a framework for analyzing more complex problems. These general considerations provide a guide for designing optimal algorithms for real-world search problems.
Distribution-Independent Evolvability of Linear Threshold Functions
Venue: arXiv cs.LG 2011
Year: 2011

Valiant's (2007) model of evolvability models the evolutionary process of acquiring useful functionality as a restricted form of learning from random examples. Linear threshold functions and their various subclasses, such as conjunctions and decision lists, play a fundamental role in learning theory and hence their evolvability has been the primary focus of research on Valiant's framework (2007). One of the main open problems regarding the model is whether conjunctions are evolvable distribution-independently (Feldman and Valiant, 2008). We show that the answer is negative. Our proof is based on a new combinatorial parameter of a concept class that lower-bounds the complexity of learning from correlations. We contrast the lower bound with a proof that linear threshold functions having a non-negligible margin on the data points are evolvable distribution-independently via a simple mutation algorithm. Our algorithm relies on a non-linear loss function being used to select the hypotheses instead of 0-1 loss in Valiant's (2007) original definition. The proof of evolvability requires that the loss function satisfies several mild conditions that are, for example, satisfied by the quadratic loss function studied in several other works (Michael, 2007; Feldman, 2009; Valiant, 2010). An important property of our evolution algorithm is monotonicity, that is the algorithm guarantees evolvability without any decreases in performance. Previously, monotone evolvability was only shown for conjunctions with quadratic loss (Feldman, 2009) or when the distribution on the domain is severely restricted (Michael, 2007; Feldman, 2009; Kanade et al., 2010)
Bounds and Inequalities Relating h-Index, g-Index, e-Index and Generalized Impact Factor
Venue: arXiv cs.DL 2011
Year: 2011

Finding relationships among different indices such as h-index, g-index, e-index, and generalized impact factor is a challenging task. In this paper, we describe some bounds and inequalities relating h-index, g-index, e-index, and generalized impact factor. We derive the bounds and inequalities relating these indexing parameters from their basic definitions and without assuming any continuous model to be followed by any of them.
Study of the effect of cost policies in the convergence of selfish strategies in Pure Nash Equilibria in Congestion Games
Venue: arXiv cs.GT 2011
Year: 2011

In this work we study of competitive situations among users of a set of global resources. More precisely we study the effect of cost policies used by these resources in the convergence time to a pure Nash equilibrium. The work is divided in two parts. In the theoretical part we prove lower and upper bounds on the convergence time for various cost policies. We then implement all the models we study and provide some experimental results. These results follows the theoretical with one exception which is the most interesting among the experiments. In the case of coalitional users the theoretical upper bound is pseudo-polynomial to the number of users but the experimental results shows that the convergence time is polynomial.
A family of abstract interpretations for static analysis of concurrent higher-order programs
Venue: arXiv cs.PL 2011
Year: 2011

We develop a framework for computing two foundational analyses for concurrent higher-order programs: (control-)flow analysis (CFA) and may-happen-in-parallel analysis (MHP). We pay special attention to the unique challenges posed by the unrestricted mixture of first-class continuations and dynamically spawned threads. To set the stage, we formulate a concrete model of concurrent higher-order programs: the P(CEK*)S machine. We find that the systematic abstract interpretation of this machine is capable of computing both flow and MHP analyses. Yet, a closer examination finds that the precision for MHP is poor. As a remedy, we adapt a shape analytic technique-singleton abstraction-to dynamically spawned threads (as opposed to objects in the heap). We then show that if MHP analysis is not of interest, we can substantially accelerate the computation of flow analysis alone by collapsing thread interleavings with a second layer of abstraction.
Using a Non-Commutative Bernstein Bound to Approximate Some Matrix Algorithms in the Spectral Norm
Venue: arXiv cs.DS 2011
Year: 2011

We focus on \emph{row sampling} based approximations for matrix algorithms, in particular matrix multipication, sparse matrix reconstruction, and \math{\ell_2} regression. For \math{\matA\in\R^{m\times d}} (\math{m} points in \math{d\ll m} dimensions), and appropriate row-sampling probabilities, which typically depend on the norms of the rows of the \math{m\times d} left singular matrix of \math{\matA} (the \emph{leverage scores}), we give row-sampling algorithms with linear (up to polylog factors) dependence on the stable rank of \math{\matA}. This result is achieved through the application of non-commutative Bernstein bounds. Keywords: row-sampling; matrix multiplication; matrix reconstruction; estimating spectral norm; linear regression; randomized
Orthogonal Range Searching on the RAM, Revisited
Venue: arXiv cs.CG 2011
Year: 2011

We present several new results on one of the most extensively studied topics in computational geometry, orthogonal range searching. All our results are in the standard word RAM model for points in rank space: ** We present two data structures for 2-d orthogonal range emptiness. The first achieves O(n lglg n) space and O(lglg n) query time. This improves the previous results by Alstrup, Brodal, and Rauhe(FOCS'00), with O(n lg^eps n) space and O(lglg n) query time, or with O(nlglg n) space and O(lg^2 lg n) query time. Our second data structure uses O(n) space and answers queries in O(lg^eps n) time. The best previous O(n)-space data structure, due to Nekrich (WADS'07), answers queries in O(lg n/lglg n) time. ** For 3-d orthogonal range reporting, we obtain space O(n lg^{1+eps} n) and query time O(lglg n + k), for any constant eps>0. This improves previous results by Afshani (ESA'08), Karpinski and Nekrich (COCOON'09), and Chan (SODA'11), with O(n lg^3 n) space and O(lglg n + k) query time, or with O(n lg^{1+eps} n) space and O(lg^2 lg n + k) query time. This implies improved bounds for orthogonal range reporting in all constant dimensions above 3. ** We give a randomized algorithm for 4-d offline dominance range reporting/emptiness with running time O(n lg n + k). This resolves two open problems from Preparata and Shamos' seminal book: **** given n axis-aligned rectangles in the plane, we can report all k enclosure pairs in O(n lg n + k) expected time. The best known result was an O([n lg n + k] lglg n) algorithm from SoCG'95 by Gupta, Janardan, Smid, and Dasgupta. **** given n points in 4-d, we can find all maximal points in O(n lg n) expected time. The best previous result was an O(n lg n lglg n) algorithm due to Gabow, Bentley, and Tarjan (STOC'84). This implies record time bounds for the maxima problem in all constant dimensions above 4.
Acyclic and Star Colorings of Cographs
Venue: arXiv cs.DS 2011
Year: 2011

An \emph{acyclic coloring} of a graph is a proper vertex coloring such that the union of any two color classes induces a disjoint collection of trees. The more restricted notion of \emph{star coloring} requires that the union of any two color classes induces a disjoint collection of stars. We prove that every acyclic coloring of a cograph is also a star coloring and give a linear-time algorithm for finding an optimal acyclic and star coloring of a cograph. If the graph is given in the form of a cotree, the algorithm runs in O(n) time. We also show that the acyclic chromatic number, the star chromatic number, the treewidth plus one, and the pathwidth plus one are all equal for cographs.
Visual Localisation of Mobile Devices in an Indoor Environment under Network Delay Conditions
Venue: arXiv cs.RO 2011
Year: 2011

Current progresses in home automation and service robotic environment have highlighted the need to develop interoperability mechanisms that allow a standard communication between the two systems. During the development of the DHCompliant protocol, the problem of locating mobile devices in an indoor environment has been investigated. The communication of the device with the location service has been carried out to study the time delay that web services offer in front of the sockets. The importance of obtaining data from real-time location systems portends that a basic tool for interoperability, such as web services, can be ineffective in this scenario because of the delays added in the invocation of services. This paper is focused on introducing a web service to resolve a coordinates request without any significant delay in comparison with the sockets.
Polynomial kernels for Proper Interval Completion and related problems
Venue: arXiv cs.DS 2011
Year: 2011

Given a graph G = (V,E) and a positive integer k, the Proper Interval Completion problem asks whether there exists a set F of at most k pairs of (V \times V)\E such that the graph H = (V,E \cup F) is a proper interval graph. The Proper Interval Completion problem finds applications in molecular biology and genomic research. First announced by Kaplan, Tarjan and Shamir in FOCS '94, this problem is known to be FPT, but no polynomial kernel was known to exist. We settle this question by proving that Proper Interval Completion admits a kernel with at most O(k^5) vertices. Moreover, we prove that a related problem, the so-called Bipartite Chain Deletion problem, admits a kernel with at most O(k^2) vertices, completing a previous result of Guo.
Image Encryption Using Differential Evolution Approach in Frequency Domain
Venue: arXiv cs.CR 2011
Year: 2011

This paper presents a new effective method for image encryption which employs magnitude and phase manipulation using Differential Evolution (DE) approach. The novelty of this work lies in deploying the concept of keyed discrete Fourier transform (DFT) followed by DE operations for encryption purpose. To this end, a secret key is shared between both encryption and decryption sides. Firstly two dimensional (2-D) keyed discrete Fourier transform is carried out on the original image to be encrypted. Secondly crossover is performed between two components of the encrypted image, which are selected based on Linear Feedback Shift Register (LFSR) index generator. Similarly, keyed mutation is performed on the real parts of a certain components selected based on LFSR index generator. The LFSR index generator initializes it seed with the shared secret key to ensure the security of the resulting indices. The process shuffles the positions of image pixels. A new image encryption scheme based on the DE approach is developed which is composed with a simple diffusion mechanism. The deciphering process is an invertible process using the same key. The resulting encrypted image is found to be fully distorted, resulting in increasing the robustness of the proposed work. The simulation results validate the proposed image encryption scheme.
A Comparative Case Study of Code Reuse With Language Oriented Programming
Venue: arXiv cs.SE 2011
Year: 2011

There is a gap between our ability to reuse high-level concepts in software design and our ability to reuse the code implementing them. Language Oriented Programming (LOP) is a software development paradigm that aims to close this gap, through extensive use of Domain Specific Languages (DSLs). With LOP, the high-level reusable concepts become reusable DSL constructs, and their translation into code level concepts is done in the DSL implementation. Particular products are implemented using DSL code, thus reusing only high-level concepts. In this paper we provide a comparison between two implementation approaches for LOP: (a) using external DSLs with a projectional language workbench (MPS); and (b) using internal DSLs with an LOP language (Cedalion). To demonstrate how reuse is achieved in each approach, we present a small case study, where LOP is used to build a Software Product Line (SPL) of calculator software.