OpenRaiser/Intern-Atlas huggingface dataset:
Conjugate-Root Offset-QAM for Orthogonal Multicarrier Transmission
Venue: arXiv cs.IT 2015
Year: 2015

Current implementations of OFDM/OQAM are restricted to band-limited symmetric filters. To circumvent this, non-symmetric conjugate root (CR) filters are proposed for OQAM modulation. The system is applied to Generalized Frequency Division Multiplexing (GFDM) and a method for achieving transmit diversity with OQAM modulation is presented. The proposal reduces implementation complexity compared to existing works and provides a more regular phase space. GFDM/CR-OQAM outperforms conventional GFDM in terms of symbol error rate in fading multipath channels and provides a more localized spectrum compared to conventional OQAM.
The nonassociative algebras used to build fast-decodable space-time block codes
Venue: arXiv cs.IT 2015
Year: 2015

Let $K/F$ and $K/L$ be two cyclic Galois field extensions and $D=(K/F,σ,c)$ a cyclic algebra. Given an invertible element $d\in D$, we present three families of unital nonassociative algebras over $L\cap F$ defined on the direct sum of $n$ copies of $D$. Two of these families appear either explicitly or implicitly in the designs of fast-decodable space-time block codes in papers by Srinath, Rajan, Markin, Oggier, and the authors. We present conditions for the algebras to be division and propose a construction for fully diverse fast decodable space-time block codes of rate-$m$ for $nm$ transmit and $m$ receive antennas. We present a DMT-optimal rate-3 code for 6 transmit and 3 receive antennas which is fast-decodable, with ML-decoding complexity at most $\mathcal{O}(M^{15})$.
Time Centrality in Dynamic Complex Networks
Venue: arXiv cs.SI 2015
Year: 2015

There is an ever-increasing interest in investigating dynamics in time-varying graphs (TVGs). Nevertheless, so far, the notion of centrality in TVG scenarios usually refers to metrics that assess the relative importance of nodes along the temporal evolution of the dynamic complex network. For some TVG scenarios, however, more important than identifying the central nodes under a given node centrality definition is identifying the key time instants for taking certain actions. In this paper, we thus introduce and investigate the notion of time centrality in TVGs. Analogously to node centrality, time centrality evaluates the relative importance of time instants in dynamic complex networks. In this context, we present two time centrality metrics related to diffusion processes. We evaluate the two defined metrics using both a real-world dataset representing an in-person contact dynamic network and a synthetically generated randomized TVG. We validate the concept of time centrality showing that diffusion starting at the best classified time instants (i.e. the most central ones), according to our metrics, can perform a faster and more efficient diffusion process.
Overlapping Community Structure in Co-authorship Networks: a Case Study
Venue: arXiv cs.SI 2015
Year: 2015

Community structure is one of the key properties of real-world complex networks. It plays a crucial role in their behaviors and topology. While an important work has been done on the issue of community detection, very little attention has been devoted to the analysis of the community structure. In this paper, we present an extensive investigation of the overlapping community network deduced from a large-scale co-authorship network. The nodes of the overlapping community network represent the functional communities of the co-authorship network, and the links account for the fact that communities share some nodes in the co-authorship network. The comparative evaluation of the topological properties of these two networks shows that they share similar topological properties. These results are very interesting. Indeed, the network of communities seems to be a good representative of the original co-authorship network. With its smaller size, it may be more practical in order to realize various analyses that cannot be performed easily in large-scale real-world networks.
The Blacklisting Memory Scheduler: Balancing Performance, Fairness and Complexity
Venue: arXiv cs.DC 2015
Year: 2015

In a multicore system, applications running on different cores interfere at main memory. This inter-application interference degrades overall system performance and unfairly slows down applications. Prior works have developed application-aware memory schedulers to tackle this problem. State-of-the-art application-aware memory schedulers prioritize requests of applications that are vulnerable to interference, by ranking individual applications based on their memory access characteristics and enforcing a total rank order. In this paper, we observe that state-of-the-art application-aware memory schedulers have two major shortcomings. First, such schedulers trade off hardware complexity in order to achieve high performance or fairness, since ranking applications with a total order leads to high hardware complexity. Second, ranking can unfairly slow down applications that are at the bottom of the ranking stack. To overcome these shortcomings, we propose the Blacklisting Memory Scheduler (BLISS), which achieves high system performance and fairness while incurring low hardware complexity, based on two observations. First, we find that, to mitigate interference, it is sufficient to separate applications into only two groups. Second, we show that this grouping can be efficiently performed by simply counting the number of consecutive requests served from each application. We evaluate BLISS across a wide variety of workloads/system configurations and compare its performance and hardware complexity, with five state-of-the-art memory schedulers. Our evaluations show that BLISS achieves 5% better system performance and 25% better fairness than the best-performing previous scheduler while greatly reducing critical path latency and hardware area cost of the memory scheduler (by 79% and 43%, respectively), thereby achieving a good trade-off between performance, fairness and hardware complexity.
Dynamic Causality in Event Structures (Technical Report)
Venue: arXiv cs.LO 2015
Year: 2015

In [1] we present an extension of Prime Event Structures by a mechanism to express dynamicity in the causal relation. More precisely we add the possibility that the occurrence of an event can add or remove causal dependencies between events and analyse the expressive power of the resulting Event Structures w.r.t. to some well-known Event Structures from the literature. This technical report contains some additional information and the missing proofs of [1].
The Method of Constructing Models of Peer to Peer Protocols
Venue: arXiv cs.NI 2015
Year: 2015

The models of peer to peer protocols are presented with the help of one-step processes. On the basis of this presentation and the method of randomization of one-step processes described method for constructing models of peer to peer protocols. As specific implementations of proposed method the models of FastTrack and Bittorrent protocols are studied.
Oblivious Transfer Protocol with Verification
Venue: arXiv cs.CR 2015
Year: 2015

Although random sequences can be used to generate probability events, they come with the risk of cheating in an unsupervised situation. In such cases, the oblivious transfer protocol may be used and this paper presents a variation to the DH key-exchange to serve as this protocol. A method to verify the correctness of the procedure, without revealing the random numbers used by the two parties, is also proposed.
On the Feasibility of Attribute-Based Encryption on Smartphone Devices
Venue: arXiv cs.CR 2015
Year: 2015

Attribute-Based Encryption (ABE) is a powerful cryptographic tool that allows fine-grained access control over data. Due to its features, ABE has been adopted in several applications, such as encrypted storage or access control systems. Recently, researchers argued about the non acceptable performance of ABE when implemented on mobile devices. Indeed, the non feasibility of ABE on mobile devices would hinder the deployment of novel protocols and services--that could instead exploit the full potential of such devices. However, we believe the conclusion of non usability was driven by a not-very efficient implementation. In this paper, we want to shine a light on this concern by studying the feasibility of applying ABE on smartphone devices. In particular, we implemented AndrABEn, an ABE library for Android operating system. Our library is written in the C language and implements two main ABE schemes: Ciphertext-Policy Attribute-Based Encryption, and Key- Policy Attribute-Based Encryption. We also run a thorough set of experimental evaluation for AndrABEn, and compare it with the current state-of-the-art (considering the same experimental setting). The results confirm the possibility to effectively use ABE on smartphone devices, requiring an acceptable amount of resources in terms of computations and energy consumption. Since the current state-of-the-art claims the non feasibility of ABE on mobile devices, we believe that our study (together with the AndrABEn library that we made available online) is a key result that will pave the way for researchers and developers to design and implement novel protocols and applications for mobile devices.
Software for Wearable Devices: Challenges and Opportunities
Venue: arXiv cs.HC 2015
Year: 2015

Wearable devices are a new form of mobile computer system that provides exclusive and user-personalized services. Wearable devices bring new issues and challenges to computer science and technology. This paper summarizes the development process and the categories of wearable devices. In addition, we present new key issues arising in aspects of wearable devices, including operating systems, database management system, network communication protocol, application development platform, privacy and security, energy consumption, human-computer interaction, software engineering, and big data.
Evaluation Evaluation a Monte Carlo study
Venue: arXiv cs.AI 2015
Year: 2015

Over the last decade there has been increasing concern about the biases embodied in traditional evaluation methods for Natural Language Processing/Learning, particularly methods borrowed from Information Retrieval. Without knowledge of the Bias and Prevalence of the contingency being tested, or equivalently the expectation due to chance, the simple conditional probabilities Recall, Precision and Accuracy are not meaningful as evaluation measures, either individually or in combinations such as F-factor. The existence of bias in NLP measures leads to the 'improvement' of systems by increasing their bias, such as the practice of improving tagging and parsing scores by using most common value (e.g. water is always a Noun) rather than the attempting to discover the correct one. The measures Cohen Kappa and Powers Informedness are discussed as unbiased alternative to Recall and related to the psychologically significant measure DeltaP. In this paper we will analyze both biased and unbiased measures theoretically, characterizing the precise relationship between all these measures as well as evaluating the evaluation measures themselves empirically using a Monte Carlo simulation.
Declaratively solving Google Code Jam problems with Picat
Venue: arXiv cs.PL 2015
Year: 2015

In this paper we present several examples of solving algorithmic problems from the Google Code Jam programming contest with Picat programming language using declarative techniques: constraint logic programming and tabled logic programming. In some cases the use of Picat simplifies the implementation compared to conventional imperative programming languages, while in others it allows to directly convert the problem statement into an efficiently solvable declarative problem specification without inventing an imperative algorithm.
Modifying the Yamaguchi Four-Component Decomposition Scattering Powers Using a Stochastic Distance
Venue: arXiv cs.IT 2015
Year: 2015

Model-based decompositions have gained considerable attention after the initial work of Freeman and Durden. This decomposition which assumes the target to be reflection symmetric was later relaxed in the Yamaguchi et al. decomposition with the addition of the helix parameter. Since then many decomposition have been proposed where either the scattering model was modified to fit the data or the coherency matrix representing the second order statistics of the full polarimetric data is rotated to fit the scattering model. In this paper we propose to modify the Yamaguchi four-component decomposition (Y4O) scattering powers using the concept of statistical information theory for matrices. In order to achieve this modification we propose a method to estimate the polarization orientation angle (OA) from full-polarimetric SAR images using the Hellinger distance. In this method, the OA is estimated by maximizing the Hellinger distance between the un-rotated and the rotated $T_{33}$ and the $T_{22}$ components of the coherency matrix $\mathbf{[T]}$. Then, the powers of the Yamaguchi four-component model-based decomposition (Y4O) are modified using the maximum relative stochastic distance between the $T_{33}$ and the $T_{22}$ components of the coherency matrix at the estimated OA. The results show that the overall double-bounce powers over rotated urban areas have significantly improved with the reduction of volume powers. The percentage of pixels with negative powers have also decreased from the Y4O decomposition. The proposed method is both qualitatively and quantitatively compared with the results obtained from the Y4O and the Y4R decompositions for a Radarsat-2 C-band San-Francisco dataset and an UAVSAR L-band Hayward dataset.
Watch and Learn: Optimizing from Revealed Preferences Feedback
Venue: arXiv cs.DS 2015
Year: 2015

A Stackelberg game is played between a leader and a follower. The leader first chooses an action, then the follower plays his best response. The goal of the leader is to pick the action that will maximize his payoff given the follower's best response. In this paper we present an approach to solving for the leader's optimal strategy in certain Stackelberg games where the follower's utility function (and thus the subsequent best response of the follower) is unknown. Stackelberg games capture, for example, the following interaction between a producer and a consumer. The producer chooses the prices of the goods he produces, and then a consumer chooses to buy a utility maximizing bundle of goods. The goal of the seller here is to set prices to maximize his profit---his revenue, minus the production cost of the purchased bundle. It is quite natural that the seller in this example should not know the buyer's utility function. However, he does have access to revealed preference feedback---he can set prices, and then observe the purchased bundle and his own profit. We give algorithms for efficiently solving, in terms of both computational and query complexity, a broad class of Stackelberg games in which the follower's utility function is unknown, using only "revealed preference" access to it. This class includes in particular the profit maximization problem, as well as the optimal tolling problem in nonatomic congestion games, when the latency functions are unknown. Surprisingly, we are able to solve these problems even though the optimization problems are non-convex in the leader's actions.
Adoption Factors for e-Malls in the SME Sector in Saudi Arabia
Venue: arXiv cs.CY 2015
Year: 2015

The small and medium-sized enterprise (SME) sector represents one of the fundamental pillars in the trade field. It contributes significantly to raising the economies of countries by providing significant numbers of job opportunities, which are beneficial to directly supporting national economies. One of the most important obstacles facing this sector in the information technology era is the lack of online trading channels with consumers, which require more financial support than the their capabilities. Therefore, e-Malls might be one of the best low-cost solutions to overcome this obstacle. Also, they provide electronic platforms that include most SME requirements for sales via electronic channels as well as offer essential technical support. According to a report published in 2013 by the Saudi Arabian Monetary Agency (SAMA), the percentage of SMEs is equivalent to 90% of the total number of companies in Saudi Arabia, which is numbered at 848,500. The e-Mall is a modern idea in Saudi Arabia that requires the use of the Disunion Of Innovation (DOI) approach to diffuse e-Malls through determining companies requirements and difficulties. Therefore, this paper focuses on the factors that help SMEs to adopt e-Malls. A quantitative questionnaire was conducted on 108 companies in Saudi Arabia to find what obstacles and requirements they face to adopt an e-Mall and focus on the factors affecting the implementation of this system, which are divided into organizational, technical and cultural factors.
Coded Caching with Heterogenous Cache Sizes
Venue: arXiv cs.IT 2015
Year: 2015

We investigate the coded caching scheme under heterogenous cache sizes.
Challenges in transforming, engaging and improving m-learning in Higher Educational Institutions: Oman perspective
Venue: arXiv cs.CY 2015
Year: 2015

Nowadays, the student community is growing up with mobile devices and it has becomes an integral part of their life. Devices such as smartphones, tablets, and e-book readers connect users to access information and enabling instant communication with others. The enormous growth and affordability of mobile devices influenced their learning practices. Mobile technologies are playing a significant role in students' academic activities. The factors like convenience, flexibility, engagement, interactivity and easy-to-use enable mobile learning more attractive to students. With these trends in mind, it is important for the educators to inherit the mobile technologies in effective teaching and learning. Our study explores the challenges that exist in implementing the m-learning technologies in the teaching and learning practices of higher educational institutions of Oman. Our study also addressed various issue like adoption of technology, transition to new technology and issues related to engaging students. Based on the outcomes of the study, a framework has been formulated to address all the challenges that are identified for the successful implementation of m-learning.
Heuristic algorithms for obtaining Polynomial Threshold Functions with low densities
Venue: arXiv cs.CC 2015
Year: 2015

In this paper we present several heuristic algorithms, including a Genetic Algorithm (GA), for obtaining polynomial threshold function (PTF) representations of Boolean functions (BFs) with small number of monomials. We compare these among each other and against the algorithm of Oztop via computational experiments. The results indicate that our heuristic algorithms find more parsimonious representations compared to the those of non-heuristic and GA-based algorithms.
New algorithm for the discrete logarithm problem on elliptic curves
Venue: arXiv cs.CR 2015
Year: 2015

A new algorithms for computing discrete logarithms on elliptic curves defined over finite fields is suggested. It is based on a new method to find zeroes of summation polynomials. In binary elliptic curves one is to solve a cubic system of Boolean equations. Under a first fall degree assumption the regularity degree of the system is at most $4$. Extensive experimental data which supports the assumption is provided. An heuristic analysis suggests a new asymptotical complexity bound $2^{c\sqrt{n\ln n}}, c\approx 1.69$ for computing discrete logarithms on an elliptic curve over a field of size $2^n$. For several binary elliptic curves recommended by FIPS the new method performs better than Pollard's.
Computing on Masked Data to improve the Security of Big Data
Venue: arXiv cs.CR 2015
Year: 2015

Organizations that make use of large quantities of information require the ability to store and process data from central locations so that the product can be shared or distributed across a heterogeneous group of users. However, recent events underscore the need for improving the security of data stored in such untrusted servers or databases. Advances in cryptographic techniques and database technologies provide the necessary security functionality but rely on a computational model in which the cloud is used solely for storage and retrieval. Much of big data computation and analytics make use of signal processing fundamentals for computation. As the trend of moving data storage and computation to the cloud increases, homeland security missions should understand the impact of security on key signal processing kernels such as correlation or thresholding. In this article, we propose a tool called Computing on Masked Data (CMD), which combines advances in database technologies and cryptographic tools to provide a low overhead mechanism to offload certain mathematical operations securely to the cloud. This article describes the design and development of the CMD tool.
Robust Timing Synchronization for AC-OFDM Based Optical Wireless Communications
Venue: arXiv cs.IT 2015
Year: 2015

Visible light communications (VLC) have recently attracted a growing interest and can be a potential solution to realize indoor wireless communication with high bandwidth capacity for RF-restricted environments such as airplanes and hospitals. Optical based orthogonal frequency division multiplexing (OFDM) systems have been proposed in the literature to combat multipath distortion and intersymbol interference (ISI) caused by multipath signal propagation. In this paper, we present a robust timing synchronization scheme suitable for asymmetrically clipped (AC) OFDM based optical intensity modulated direct detection (IM/DD) wireless systems. Our proposed method works perfectly for ACO-OFDM, Pulse amplitude modulated discrete multitone (PAM-DMT) and discrete Hartley transform (DHT) based optical OFDM systems. In contrast to existing OFDM timing synchronization methods which are either not suitable for AC OFDM techniques due to unipolar nature of output signal or perform poorly, our proposed method is suitable for AC OFDM schemes and outperforms all other available techniques. Both numerical and experimental results confirm the accuracy of the proposed method. Our technique is also computationally efficient as it requires very few computations as compared to conventional methods in order to achieve good accuracy.
Separating decision tree complexity from subcube partition complexity
Venue: arXiv cs.CC 2015
Year: 2015

The subcube partition model of computation is at least as powerful as decision trees but no separation between these models was known. We show that there exists a function whose deterministic subcube partition complexity is asymptotically smaller than its randomized decision tree complexity, resolving an open problem of Friedgut, Kahn, and Wigderson (2002). Our lower bound is based on the information-theoretic techniques first introduced to lower bound the randomized decision tree complexity of the recursive majority function. We also show that the public-coin partition bound, the best known lower bound method for randomized decision tree complexity subsuming other general techniques such as block sensitivity, approximate degree, randomized certificate complexity, and the classical adversary bound, also lower bounds randomized subcube partition complexity. This shows that all these lower bound techniques cannot prove optimal lower bounds for randomized decision tree complexity, which answers an open question of Jain and Klauck (2010) and Jain, Lee, and Vishnoi (2014).