OpenRaiser/Intern-Atlas huggingface dataset:
A Weakest Chain Approach to Assessing the Overall Effectiveness of the 802.11 Wireless Network Security
Venue: arXiv cs.CR 2011
Year: 2011

This study aims to assess wireless network security holistically and attempts to determine the weakest link among the parts that comprise the 'secure' aspect of the wireless networks: security protocols, wireless technologies and user habits. The assessment of security protocols is done by determining the time taken to break a specific protocol's encryption key, or to pass an access control by using brute force attack techniques. Passphrase strengths as well as encryption key strengths ranging from 40 to 256 bits are evaluated. Different scenarios are planned and created for passphrase generation, using different character sets and different number of characters. Then each scenario is evaluated based on the time taken to break that passphrase. At the end of the study, it is determined that the choice of the passphrase is the weakest part of the entire 802.11 wireless security system.
Algebraic Hybrid Satellite-Terrestrial Space-Time Codes for Digital Broadcasting in SFN
Venue: arXiv cs.IT 2011
Year: 2011

Lately, different methods for broadcasting future digital TV in a single frequency network (SFN) have been under an intensive study. To improve the transmission to also cover suburban and rural areas, a hybrid scheme may be used. In hybrid transmission, the signal is transmitted both from a satellite and from a terrestrial site. In 2008, Y. Nasser et al. proposed to use a double layer 3D space-time (ST) code in the hybrid 4 x 2 MIMO transmission of digital TV. In this paper, alternative codes with simpler structure are proposed for the 4 x 2 hybrid system, and new codes are constructed for the 3 x 2 system. The performance of the proposed codes is analyzed through computer simulations, showing a significant improvement over simple repetition schemes. The proposed codes prove in addition to be very robust in the presence of power imbalance between the two sites.
Outage Probability in η-μ/η-μ Interference-limited Scenarios
Venue: arXiv cs.IT 2011
Year: 2011

In this paper exact closed-form expressions are derived for the outage probability (OP) in scenarios where both the signal of interest (SOI) and the interfering signals experience η-μ fading and the background noise can be neglected. With the only assumption that the μ parameter is a positive integer number for the interfering signals, the derived expressions are given in elementary terms for maximal ratio combining (MRC) with independent branches. The analysis is also valid when the μ parameters of the pre-combining SOI power envelopes are positive integer or half-integer numbers and the SOI is formed at the receiver from spatially correlated MRC.
Loopy Belief Propagation, Bethe Free Energy and Graph Zeta Function
Venue: arXiv cs.AI 2011
Year: 2011

We propose a new approach to the theoretical analysis of Loopy Belief Propagation (LBP) and the Bethe free energy (BFE) by establishing a formula to connect LBP and BFE with a graph zeta function. The proposed approach is applicable to a wide class of models including multinomial and Gaussian types. The connection derives a number of new theoretical results on LBP and BFE. This paper focuses two of such topics. One is the analysis of the region where the Hessian of the Bethe free energy is positive definite, which derives the non-convexity of BFE for graphs with multiple cycles, and a condition of convexity on a restricted set. This analysis also gives a new condition for the uniqueness of the LBP fixed point. The other result is to clarify the relation between the local stability of a fixed point of LBP and local minima of the BFE, which implies, for example, that a locally stable fixed point of the Gaussian LBP is a local minimum of the Gaussian Bethe free energy.
Performance Comparisons of Routing Protocols in Mobile Ad Hoc Networks
Venue: arXiv cs.NI 2011
Year: 2011

Mobile Ad hoc Network (MANET) is a collection of wireless mobile nodes that dynamically form a network temporarily without any support of central administration. Moreover, Every node in MANET moves arbitrarily making the multi-hop network topology to change randomly at unpredictable times. There are several familiar routing protocols like DSDV, AODV, DSR, etc...which have been proposed for providing communication among all the nodes in the network. This paper presents a performance comparison of proactive and reactive protocols DSDV, AODV and DSR based on metrics such as throughput, packet delivery ratio and average end-to-end delay by using the NS-2 simulator.
Sparse Volterra and Polynomial Regression Models: Recoverability and Estimation
Venue: arXiv cs.LG 2011
Year: 2011

Volterra and polynomial regression models play a major role in nonlinear system identification and inference tasks. Exciting applications ranging from neuroscience to genome-wide association analysis build on these models with the additional requirement of parsimony. This requirement has high interpretative value, but unfortunately cannot be met by least-squares based or kernel regression methods. To this end, compressed sampling (CS) approaches, already successful in linear regression settings, can offer a viable alternative. The viability of CS for sparse Volterra and polynomial models is the core theme of this work. A common sparse regression task is initially posed for the two models. Building on (weighted) Lasso-based schemes, an adaptive RLS-type algorithm is developed for sparse polynomial regressions. The identifiability of polynomial models is critically challenged by dimensionality. However, following the CS principle, when these models are sparse, they could be recovered by far fewer measurements. To quantify the sufficient number of measurements for a given level of sparsity, restricted isometry properties (RIP) are investigated in commonly met polynomial regression settings, generalizing known results for their linear counterparts. The merits of the novel (weighted) adaptive CS algorithms to sparse polynomial modeling are verified through synthetic as well as real data tests for genotype-phenotype analysis.
Happiness is assortative in online social networks
Venue: arXiv cs.SI 2011
Year: 2011

Social networks tend to disproportionally favor connections between individuals with either similar or dissimilar characteristics. This propensity, referred to as assortative mixing or homophily, is expressed as the correlation between attribute values of nearest neighbour vertices in a graph. Recent results indicate that beyond demographic features such as age, sex and race, even psychological states such as "loneliness" can be assortative in a social network. In spite of the increasing societal importance of online social networks it is unknown whether assortative mixing of psychological states takes place in situations where social ties are mediated solely by online networking services in the absence of physical contact. Here, we show that general happiness or Subjective Well-Being (SWB) of Twitter users, as measured from a 6 month record of their individual tweets, is indeed assortative across the Twitter social network. To our knowledge this is the first result that shows assortative mixing in online networks at the level of SWB. Our results imply that online social networks may be equally subject to the social mechanisms that cause assortative mixing in real social networks and that such assortative mixing takes place at the level of SWB. Given the increasing prevalence of online social networks, their propensity to connect users with similar levels of SWB may be an important instrument in better understanding how both positive and negative sentiments spread through online social ties. Future research may focus on how event-specific mood states can propagate and influence user behavior in "real life".
Decimation-Enhanced Finite Alphabet Iterative Decoders for LDPC codes on the BSC
Venue: arXiv cs.IT 2011
Year: 2011

Finite alphabet iterative decoders (FAID) with multilevel messages that can surpass BP in the error floor region for LDPC codes on the BSC were previously proposed. In this paper, we propose decimation-enhanced decoders. The technique of decimation which is incorporated into the message update rule, involves fixing certain bits of the code to a particular value. Under appropriately chosen rules, decimation can significantly reduce the number of iterations required to correct a fixed number of errors, while maintaining the good performance of the original decoder in the error floor region. At the same time, the algorithm is much more amenable to analysis. We shall provide a simple decimation scheme for a particularly good 7-level FAID for column-weight three codes on the BSC, that helps to correct a fixed number of errors in fewer iterations, and provide insights into the analysis of the decoder. We shall also examine the conditions under which the decimation-enhanced 7-level FAID performs at least as good as the 7-level FAID.
Locating Depots for Capacitated Vehicle Routing
Venue: arXiv cs.DS 2011
Year: 2011

We study a location-routing problem in the context of capacitated vehicle routing. The input is a set of demand locations in a metric space and a fleet of k vehicles each of capacity Q. The objective is to locate k depots, one for each vehicle, and compute routes for the vehicles so that all demands are satisfied and the total cost is minimized. Our main result is a constant-factor approximation algorithm for this problem. To achieve this result, we reduce to the k-median-forest problem, which generalizes both k-median and minimum spanning tree, and which might be of independent interest. We give a (3+c)-approximation algorithm for k-median-forest, which leads to a (12+c)-approximation algorithm for the above location-routing problem, for any constant c>0. The algorithm for k-median-forest is just t-swap local search, and we prove that it has locality gap 3+2/t; this generalizes the corresponding result known for k-median. Finally we consider the "non-uniform" k-median-forest problem which has different cost functions for the MST and k-median parts. We show that the locality gap for this problem is unbounded even under multi-swaps, which contrasts with the uniform case. Nevertheless, we obtain a constant-factor approximation algorithm, using an LP based approach.
Designing Flexible GUI to Increase the Acceptance Rate of Product Data Management Systems in Industry
Venue: arXiv cs.HC 2011
Year: 2011

Product Data Management (PDM) desktop and web based systems maintain the organizational technical and managerial data to increase the quality of products by improving the processes of development, business process flows, change management, product structure management, project tracking and resource planning. Though PDM is heavily benefiting industry but PDM community is facing a very serious unresolved issue in PDM system development with flexible and user friendly graphical user interface for efficient human machine communication. PDM systems offer different services and functionalities at a time but the graphical user interfaces of most of the PDM systems are not designed in a way that a user (especially a new user) can easily learn and use them. Targeting this issue, a thorough research was conducted in field of Human Computer Interaction; resultant data provides the information about graphical user interface development using rich internet applications. The accomplished goal of this research was to support the field of PDM with a proposition of a conceptual model for the implementation of a flexible web based graphical user interface. The proposed conceptual model was successfully designed into implementation model and a resultant prototype putting values to the field is now available. Describing the proposition in detail the main concept, implementation designs and developed prototype is also discussed in this paper. Moreover in the end, prototype is compared with respective functions of existing PDM systems .i.e., Windchill and CIM to evaluate its effectiveness against targeted challenge
A Directional Feature with Energy based Offline Signature Verification Network
Venue: arXiv cs.AI 2011
Year: 2011

Signature used as a biometric is implemented in various systems as well as every signature signed by each person is distinct at the same time. So, it is very important to have a computerized signature verification system. In offline signature verification system dynamic features are not available obviously, but one can use a signature as an image and apply image processing techniques to make an effective offline signature verification system. Author proposes a intelligent network used directional feature and energy density both as inputs to the same network and classifies the signature. Neural network is used as a classifier for this system. The results are compared with both the very basic energy density method and a simple directional feature method of offline signature verification system and this proposed new network is found very effective as compared to the above two methods, specially for less number of training samples, which can be implemented practically.
Framework to Solve Load Balancing Problem in Heterogeneous Web Servers
Venue: arXiv cs.DC 2011
Year: 2011

For popular websites most important concern is to handle incoming load dynamically among web servers, so that they can respond to their client without any wait or failure. Different websites use different strategies to distribute load among web servers but most of the schemes concentrate on only one factor that is number of requests, but none of the schemes consider the point that different type of requests will require different level of processing efforts to answer, status record of all the web servers that are associated with one domain name and mechanism to handle a situation when one of the servers is not working. Therefore, there is a fundamental need to develop strategy for dynamic load allocation on web side. In this paper, an effort has been made to introduce a cluster based frame work to solve load distribution problem. This framework aims to distribute load among clusters on the basis of their operational capabilities. Moreover, the experimental results are shown with the help of example, algorithm and analysis of the algorithm.
Design of Automatically Adaptable Web Wrappers
Venue: arXiv cs.AI 2011
Year: 2011

Nowadays, the huge amount of information distributed through the Web motivates studying techniques to be adopted in order to extract relevant data in an efficient and reliable way. Both academia and enterprises developed several approaches of Web data extraction, for example using techniques of artificial intelligence or machine learning. Some commonly adopted procedures, namely wrappers, ensure a high degree of precision of information extracted from Web pages, and, at the same time, have to prove robustness in order not to compromise quality and reliability of data themselves. In this paper we focus on some experimental aspects related to the robustness of the data extraction process and the possibility of automatically adapting wrappers. We discuss the implementation of algorithms for finding similarities between two different version of a Web page, in order to handle modifications, avoiding the failure of data extraction tasks and ensuring reliability of information extracted. Our purpose is to evaluate performances, advantages and draw-backs of our novel system of automatic wrapper adaptation.
Cooperative Retransmissions Through Collisions
Venue: arXiv cs.IT 2011
Year: 2011

Interference in wireless networks is one of the key capacity-limiting factors. Recently developed interference-embracing techniques show promising performance on turning collisions into useful transmissions. However, the interference-embracing techniques are hard to apply in practical applications due to their strict requirements. In this paper, we consider utilising the interference-embracing techniques in a common scenario of two interfering sender-receiver pairs. By employing opportunistic listening and analog network coding (ANC), we show that compared to traditional ARQ retransmission, a higher retransmission throughput can be achieved by allowing two interfering senders to cooperatively retransmit selected lost packets at the same time. This simultaneous retransmission is facilitated by a simple handshaking procedure without introducing additional overhead. Simulation results demonstrate the superior performance of the proposed cooperative retransmission.
The Planetary System: Executable Science, Technology, Engineering and Math Papers
Venue: arXiv cs.DL 2011
Year: 2011

Executable scientific papers contain not just layouted text for reading. They contain, or link to, machine-comprehensible representations of the scientific findings or experiments they describe. Client-side players can thus enable readers to "check, manipulate and explore the result space". We have realized executable papers in the STEM domain with the Planetary system. Semantic annotations associate the papers with a content commons holding the background ontology, the annotations are exposed as Linked Data, and a frontend player application hooks modular interactive services into the semantic annotations.
Cost Sharing in Social Community Networks
Venue: arXiv cs.NI 2011
Year: 2011

Wireless social community networks (WSCNs) is an emerging technology that operate in the unlicensed spectrum and have been created as an alternative to cellular wireless networks for providing low-cost, high speed wireless data access in urban areas. WSCNs is an upcoming idea that is starting to gain attention amongst the civilian Internet users. By using \emph{special} WiFi routers that are provided by a social community network provider (SCNP), users can effectively share their connection with the neighborhood in return for some monthly monetary benefits. However, deployment maps of existing WSCNs reflect their slow progress in capturing the WiFi router market. In this paper, we look at a router design and cost sharing problem in WSCNs to improve deployment. We devise asimple to implement, successful a mechanism is successful if it achieves its intended purpose. For example in this work, a successful mechanism would help install routers in a locality}, \emph{budget-balanced}, \emph{ex-post efficient}, and \emph{individually rational} {a mechanism is individually rational if the benefit each agent obtains is greater than its cost.} auction-based mechanism that generates the \emph{optimal} number of features a router should have and allocates costs to residential users in \emph{proportion} to the feature benefits they receive. Our problem is important to a new-entrant SCNP when it wants to design its multi-feature routers with the goal to popularize them and increase their deployment in a residential locality. Our proposed mechanism accounts for heterogeneous user preferences towards different router features and comes up with the optimal \emph{(feature-set, user costs)} router blueprint that satisfies each user in a locality, in turn motivating them to buy routers and thereby improve deployment.
Efficient and Playful Tools to Teach Unix to New Students
Venue: arXiv cs.OS 2011
Year: 2011

Teaching Unix to new students is a common tasks in many higher schools. This paper presents an approach to such course where the students progress autonomously with the help of the teacher. The traditional textbook is complemented with a wiki, and the main thread of the course is a game, in the form of a treasure hunt. The course finishes with a lab exam, where students have to perform practical manipulations similar to the ones performed during the treasure hunt. The exam is graded fully automatically. This paper discusses the motivations and advantages of the approach, and gives an overall view of the tools we developed. The tools are available from the web, and open-source, hence re-usable outside the Ensimag.
Aorta Segmentation for Stent Simulation
Venue: arXiv cs.CV 2011
Year: 2011

Simulation of arterial stenting procedures prior to intervention allows for appropriate device selection as well as highlights potential complications. To this end, we present a framework for facilitating virtual aortic stenting from a contrast computer tomography (CT) scan. More specifically, we present a method for both lumen and outer wall segmentation that may be employed in determining both the appropriateness of intervention as well as the selection and localization of the device. The more challenging recovery of the outer wall is based on a novel minimal closure tracking algorithm. Our aortic segmentation method has been validated on over 3000 multiplanar reformatting (MPR) planes from 50 CT angiography data sets yielding a Dice Similarity Coefficient (DSC) of 90.67%.
A Token Based Algorithm to Distributed Computation in Sensor Networks
Venue: arXiv cs.NI 2011
Year: 2011

We consider distributed algorithms for data aggregation and function computation in sensor networks. The algorithms perform pairwise computations along edges of an underlying communication graph. A token is associated with each sensor node, which acts as a transmission permit. Nodes with active tokens have transmission permits; they generate messages at a constant rate and send each message to a randomly selected neighbor. By using different strategies to control the transmission permits we can obtain tradeoffs between message and time complexity. Gossip corresponds to the case when all nodes have permits all the time. We study algorithms where permits are revoked after transmission and restored upon reception. Examples of such algorithms include Simple-Random Walk(SRW), Coalescent-Random-Walk(CRW) and Controlled Flooding(CFLD) and their hybrid variants. SRW has a single node permit, which is passed on in the network. CRW, initially initially has a permit for each node but these permits are revoked gradually. The final result for SRW and CRW resides at a single(or few) random node(s) making a direct comparison with GOSSIP difficult. A hybrid two-phase algorithm switching from CRW to CFLD at a suitable pre-determined time can be employed to achieve consensus. We show that such hybrid variants achieve significant gains in both message and time complexity. The per-node message complexity for n-node graphs, such as 2D mesh, torii, and Random geometric graphs, scales as $O(polylog(n))$ and the corresponding time complexity scales as O(n). The reduced per-node message complexity leads to reduced energy utilization in sensor networks.
SPPAM - Statistical PreProcessing AlgorithM
Venue: arXiv cs.AI 2011
Year: 2011

Most machine learning tools work with a single table where each row is an instance and each column is an attribute. Each cell of the table contains an attribute value for an instance. This representation prevents one important form of learning, which is, classification based on groups of correlated records, such as multiple exams of a single patient, internet customer preferences, weather forecast or prediction of sea conditions for a given day. To some extent, relational learning methods, such as inductive logic programming, can capture this correlation through the use of intensional predicates added to the background knowledge. In this work, we propose SPPAM, an algorithm that aggregates past observations in one single record. We show that applying SPPAM to the original correlated data, before the learning task, can produce classifiers that are better than the ones trained using all records.