OpenRaiser/Intern-Atlas huggingface dataset:
Simulation and Measurement Based Vehicle-to-Vehicle Channel Characterization: Accuracy and Constraint Analysis
Venue: arXiv cs.NI 2014
Year: 2014

In this paper, a deterministic channel model for vehicle-to-vehicle (V2V) communication, is compared against channel measurement data collected during a V2V channel measurement campaign using a channel sounder. Channel metrics such as channel gain, delay and Doppler spreads, eigenvalue decomposition and antenna correlations are derived from the ray tracing (RT) simulations as well as from the measurement data obtained from two different measurements in an urban four-way intersection scenario. The channel metrics are compared separately for line-of-sight (LOS) and non-LOS (NLOS) situation. Most power contributions arise from the LOS component (if present) as well as from multipaths with single bounce reflections. Measurement and simulation results show a very good agreement in the presence of LOS, as most of the received power is contributed from the LOS component. In NLOS, the difference is large because the ray tracer is unable to capture some of the multi bounced propagation paths that are present in the measurements. Despite the limitations of the ray-based propagation model identified in this work, the model is suitable to characterize the channel properties in a sufficient manner.
Convolution, Separation and Concurrency
Venue: arXiv cs.LO 2014
Year: 2014

A notion of convolution is presented in the context of formal power series together with lifting constructions characterising algebras of such series, which usually are quantales. A number of examples underpin the universality of these constructions, the most prominent ones being separation logics, where convolution is separating conjunction in an assertion quantale; interval logics, where convolution is the chop operation; and stream interval functions, where convolution is used for analysing the trajectories of dynamical or real-time systems. A Hoare logic is constructed in a generic fashion on the power series quantale, which applies to each of these examples. In many cases, commutative notions of convolution have natural interpretations as concurrency operations.
Multi-Gigabits Millimetre Wave Wireless Communications for 5G: From Fixed Access to Cellular Networks
Venue: arXiv cs.NI 2014
Year: 2014

With the formidable growth of various booming wireless communication services that require ever-increasing data throughputs, the conventional microwave band below 10 GHz, which is currently used by almost all mobile communication systems, is going to reach its saturation point within just a few years. Therefore, the attention of radio system designers has been pushed towards ever-higher segments of the frequency spectrum in a quest for capacity increase. In this article, we investigate the feasibility, advantages and challenges of future wireless communications over the E-band frequencies. We start from a brief review of the history of E-band spectrum and its light licensing policy as well as benefits/challenges. Then we introduce the propagation characteristics of E-band signals, based on which some potential fixed and mobile applications at the E-band are investigated. In particular, we analyze the achievability of non-trivial multiplexing gain in fixed point-to-point E-band links and propose an E-band mobile broadband (EMB) system as a candidate for the next generation mobile communication networks. The channelization and frame structure of the EMB system are discussed in details.
Modular converter system for low-cost off-grid energy storage using second life Li-ion batteries
Venue: arXiv cs.SY 2014
Year: 2014

Lithium ion batteries are promising for small off- grid energy storage applications in developing countries because of their high energy density and long life. However, costs are prohibitive. Instead, we consider 'used' Li-ion batteries for this application, finding experimentally that many discarded laptop cells, for example, still have good capacity and cycle life. In order to make safe and optimal use of such cells, we present a modular power management system using a separate power converter for every cell. This novel approach allows individual batteries to be used to their full capacity. The power converters operate in voltage droop control mode to provide easy charge balancing and implement a battery management system to estimate the capacity of each cell, as we demonstrate experimentally.
Minimum Linear Arrangement of Series-Parallel Graphs
Venue: arXiv cs.DM 2014
Year: 2014

We present a factor $14D^2$ approximation algorithm for the minimum linear arrangement problem on series-parallel graphs, where $D$ is the maximum degree in the graph. Given a suitable decomposition of the graph, our algorithm runs in time $O(|E|)$ and is very easy to implement. Its divide-and-conquer approach allows for an effective parallelization. Note that a suitable decomposition can also be computed in time $O(|E|\log{|E|})$ (or even $O(\log{|E|}\log^*{|E|})$ on an EREW PRAM using $O(|E|)$ processors). For the proof of the approximation ratio, we use a sophisticated charging method that uses techniques similar to amortized analysis in advanced data structures. On general graphs, the minimum linear arrangement problem is known to be NP-hard. To the best of our knowledge, the minimum linear arrangement problem on series-parallel graphs has not been studied before.
Secure ARP and Secure DHCP Protocols to Mitigate Security Attacks
Venue: arXiv cs.CR 2014
Year: 2014

For network computers to communicate to one another, they need to know one another's IP address and MAC address. Address Resolution Protocol (ARP) is developed to find the Ethernet address that map to a specific IP address. The source computer broadcasts the request for Ethernet address and eventually the target computer replies. The IP to Ethernet address mapping would later be stored in an ARP Cache for some time duration, after which the process is repeated. Since ARP is susceptible to ARP poisoning attacks, we propose to make it unicast, centralized and secure, along with a secure design of DHCP protocol to mitigate MAC spoofing. The secure protocol designs are explained in detail. Lastly we also discuss some performance issues to show how the proposed protocols work.
Inertial Parameter Identification Including Friction and Motor Dynamics
Venue: arXiv cs.RO 2014
Year: 2014

Identification of inertial parameters is fundamental for the implementation of torque-based control in humanoids. At the same time, good models of friction and actuator dynamics are critical for the low-level control of joint torques. We propose a novel method to identify inertial, friction and motor parameters in a single procedure. The identification exploits the measurements of the PWM of the DC motors and a 6-axis force/torque sensor mounted inside the kinematic chain. The partial least-square (PLS) method is used to perform the regression. We identified the inertial, friction and motor parameters of the right arm of the iCub humanoid robot. We verified that the identified model can accurately predict the force/torque sensor measurements and the motor voltages. Moreover, we compared the identified parameters against the CAD parameters, in the prediction of the force/torque sensor measurements. Finally, we showed that the estimated model can effectively detect external contacts, comparing it against a tactile-based contact detection. The presented approach offers some advantages with respect to other state-of-the-art methods, because of its completeness (i.e. it identifies inertial, friction and motor parameters) and simplicity (only one data collection, with no particular requirements).
Prioritized Optimal Control
Venue: arXiv cs.RO 2014
Year: 2014

This paper presents a new technique to control highly redundant mechanical systems, such as humanoid robots. We take inspiration from two approaches. Prioritized control is a widespread multi-task technique in robotics and animation: tasks have strict priorities and they are satisfied only as long as they do not conflict with any higher-priority task. Optimal control instead formulates an optimization problem whose solution is either a feedback control policy or a feedforward trajectory of control inputs. We introduce strict priorities in multi-task optimal control problems, as an alternative to weighting task errors proportionally to their importance. This ensures the respect of the specified priorities, while avoiding numerical conditioning issues. We compared our approach with both prioritized control and optimal control with tests on a simulated robot with 11 degrees of freedom.
Initialization of lattice Boltzmann models with the help of the numerical Chapman-Enskog expansion
Venue: arXiv cs.CE 2014
Year: 2014

We extend the applicability of the numerical Chapman-Enskog expansion as a lifting operator for lattice Boltzmann models to map density and momentum to distribution functions. In earlier work [Vanderhoydonc et al. Multiscale Model. Simul. 10(3): 766-791, 2012] such an expansion was constructed in the context of lifting only the zeroth order velocity moment, namely the density. A lifting operator is necessary to convert information from the macroscopic to the mesoscopic scale. This operator is used for the initialization of lattice Boltzmann models. Given only density and momentum, the goal is to initialize the distribution functions of lattice Boltzmann models. For this initialization, the numerical Chapman-Enskog expansion is used in this paper.
Weighted sampling of outer products
Venue: arXiv cs.DS 2014
Year: 2014

This note gives a simple analysis of the randomized approximation scheme for matrix multiplication of Drineas et al (2006) with a particular sampling distribution over outer products. The result follows from a matrix version of Bernstein's inequality. To approximate the matrix product $AB^\top$ to spectral norm error $\varepsilon\|A\|\|B\|$, it suffices to sample on the order of $(\mathrm{sr}(A) \vee \mathrm{sr}(B)) \log(\mathrm{sr}(A) \wedge \mathrm{sr}(B)) / \varepsilon^2$ outer products, where $\mathrm{sr}(M)$ is the stable rank of a matrix $M$.
Improve CAPTCHA's Security Using Gaussian Blur Filter
Venue: arXiv cs.CV 2014
Year: 2014

Providing security for webservers against unwanted and automated registrations has become a big concern. To prevent these kinds of false registrations many websites use CAPTCHAs. Among all kinds of CAPTCHAs OCR-Based or visual CAPTCHAs are very common. Actually visual CAPTCHA is an image containing a sequence of characters. So far most of visual CAPTCHAs, in order to resist against OCR programs, use some common implementations such as wrapping the characters, random placement and rotations of characters, etc. In this paper we applied Gaussian Blur filter, which is an image transformation, to visual CAPTCHAs to reduce their readability by OCR programs. We concluded that this technique made CAPTCHAs almost unreadable for OCR programs but, their readability by human users still remained high.
A Gesture Recognition System for Detecting Behavioral Patterns of ADHD
Venue: arXiv cs.CV 2014
Year: 2014

We present an application of gesture recognition using an extension of Dynamic Time Warping (DTW) to recognize behavioural patterns of Attention Deficit Hyperactivity Disorder (ADHD). We propose an extension of DTW using one-class classifiers in order to be able to encode the variability of a gesture category, and thus, perform an alignment between a gesture sample and a gesture class. We model the set of gesture samples of a certain gesture category using either GMMs or an approximation of Convex Hulls. Thus, we add a theoretical contribution to classical warping path in DTW by including local modeling of intra-class gesture variability. This methodology is applied in a clinical context, detecting a group of ADHD behavioural patterns defined by experts in psychology/psychiatry, to provide support to clinicians in the diagnose procedure. The proposed methodology is tested on a novel multi-modal dataset (RGB plus Depth) of ADHD children recordings with behavioural patterns. We obtain satisfying results when compared to standard state-of-the-art approaches in the DTW context.
Stochastic Optimal Linear Control of Wireless Networked Control Systems with Delays and Packet Losses
Venue: arXiv cs.SY 2014
Year: 2014

In this paper, the design of the optimal decentralized state-feedback controllers is considered for a wireless sensor and actuator network (WSAN) with stochastic network-induced delays and packet losses. In particular, taking advantage of multiple controllers, we model the WSAN as a wireless networked control system (NCS) with decentralized controllers, and then formulate the stochastic optimal state-feedback control problem as a non-cooperative linear quadratic (LQ) game. The optimal control law of each controller is obtained that is a function of the current plant state and all past control signals. The performance of the proposed stochastic optimal control algorithm is investigated using both a genetic control system and a load frequency control (LFC) system in power grid.
Problem Based Learning and Implementations
Venue: arXiv cs.CY 2014
Year: 2014

In an era where learning is considered a problem, we decided to go for problems for the sake of learning! The purpose of this study was to throw light on the issues involved in two forms of PBL viz., Case Study Based PBL and Research Based PBL The influence of course and subject on the learning method was investigated. Students perceptions and concerns were analyzed using questionnaires. A slight variation was found among the different courses of Engineering, Business and IT, as also among the sample subjects considered. It is concluded that careful and systematic introduction to the case study based learning can be progressively led to the Research based learning as the student progresses from the first semester to the final semester of a graduate degree course or from graduate degree course to post graduate degree course.
QoS Survey in IPv6 and Queuing Methods
Venue: arXiv cs.NI 2014
Year: 2014

The routes in IP networks are determined by the IP destination address and the routing tables in each router on the path to the destination. Hence all the IP packets follow the same route until the route is changes due to congestion, link failure or topology updates. IPv4 tried using Type of Service (TOS) field in the IP header to classify traffic and that did not succeed as it was based on fair self-classification of applications in comparison to the network traffic of other applications. As multimedia applications were quite foreign at the initial IPv4 stage, TOS field was not used uniformly. As there are different existing Quality of Service (QoS) paradigms available, IPv6 QoS approach was designed to be more flexible. The IPv6 protocol thus has QoS-specific elements in Base header and Extension headers which can be used in different ways to enhance multimedia application performance. In this paper, we plan to survey these options and other QoS architectures and discuss their strengths and weaknesses. Some basic simulation for various queuing schemes is presented for comparison and a new queuing scheme prioritized WFQ with RR is proposed.
Analysis of Demand Driven Ad-hoc Routing Protocols on Performance and Mobility
Venue: arXiv cs.NI 2014
Year: 2014

Mobile ad hoc networking (MANET) is a growing technology that can support the operation of adaptive wireless networks. With the increased demand rate of wireless applications it is useful to have more adaptive and self organizing technologies that adapt to changes within a network region. In this paper we initially present a brief listing of table driven ad hoc routing protocols and eventually analyze in detail the behaviour of demand driven ad hoc routing protocols like - Ad Hoc On Demand Distance Vector Routing (AODV), Dynamic Source Routing (DSR), Temporally-Ordered Routing Algorithm (TORA) in terms of throughput, traffic dropped, routing traffic and mobility. The output graphs are eventually discussed, thus enabling us to understand the routing technology better.
Applying Genetic Algorithm for Prioritization of Test Case Scenarios Derived from UML Diagrams
Venue: arXiv cs.SE 2014
Year: 2014

Software testing involves identifying the test cases whichdiscover errors in the program. However, exhaustive testing ofsoftware is very time consuming. In this paper, a technique isproposed to prioritize test case scenarios by identifying the critical path clusters using genetic algorithm. The test case scenarios are derived from the UML activity diagram and state chart diagram. The testing efficiency is optimized by applying the genetic algorithm on the test data. The information flow metric is adopted in this work for calculating the information flow complexity associated with each node of the activity diagram and state chart diagram.
The Visualization of Change in Word Meaning over Time using Temporal Word Embeddings
Venue: arXiv cs.CL 2014
Year: 2014

We describe a visualization tool that can be used to view the change in meaning of words over time. The tool makes use of existing (static) word embedding datasets together with a timestamped $n$-gram corpus to create {\em temporal} word embeddings.
Privacy Leakage in Mobile Computing: Tools, Methods, and Characteristics
Venue: arXiv cs.CR 2014
Year: 2014

The number of smartphones, tablets, sensors, and connected wearable devices are rapidly increasing. Today, in many parts of the globe, the penetration of mobile computers has overtaken the number of traditional personal computers. This trend and the always-on nature of these devices have resulted in increasing concerns over the intrusive nature of these devices and the privacy risks that they impose on users or those associated with them. In this paper, we survey the current state of the art on mobile computing research, focusing on privacy risks and data leakage effects. We then discuss a number of methods, recommendations, and ongoing research in limiting the privacy leakages and associated risks by mobile computing.
Gaussian Process Models with Parallelization and GPU acceleration
Venue: arXiv cs.DC 2014
Year: 2014

In this work, we present an extension of Gaussian process (GP) models with sophisticated parallelization and GPU acceleration. The parallelization scheme arises naturally from the modular computational structure w.r.t. datapoints in the sparse Gaussian process formulation. Additionally, the computational bottleneck is implemented with GPU acceleration for further speed up. Combining both techniques allows applying Gaussian process models to millions of datapoints. The efficiency of our algorithm is demonstrated with a synthetic dataset. Its source code has been integrated into our popular software library GPy.
Sparse Beamforming and User-Centric Clustering for Downlink Cloud Radio Access Network
Venue: arXiv cs.IT 2014
Year: 2014

This paper considers a downlink cloud radio access network (C-RAN) in which all the base-stations (BSs) are connected to a central computing cloud via digital backhaul links with finite capacities. Each user is associated with a user-centric cluster of BSs; the central processor shares the user's data with the BSs in the cluster, which then cooperatively serve the user through joint beamforming. Under this setup, this paper investigates the user scheduling, BS clustering and beamforming design problem from a network utility maximization perspective. Differing from previous works, this paper explicitly considers the per-BS backhaul capacity constraints. We formulate the network utility maximization problem for the downlink C-RAN under two different models depending on whether the BS clustering for each user is dynamic or static over different user scheduling time slots. In the former case, the user-centric BS cluster is dynamically optimized for each scheduled user along with the beamforming vector in each time-frequency slot, while in the latter case the user-centric BS cluster is fixed for each user and we jointly optimize the user scheduling and the beamforming vector to account for the backhaul constraints. In both cases, the nonconvex per-BS backhaul constraints are approximated using the reweighted l1-norm technique. This approximation allows us to reformulate the per-BS backhaul constraints into weighted per-BS power constraints and solve the weighted sum rate maximization problem through a generalized weighted minimum mean square error approach. This paper shows that the proposed dynamic clustering algorithm can achieve significant performance gain over existing naive clustering schemes. This paper also proposes two heuristic static clustering schemes that can already achieve a substantial portion of the gain.
Block-Sparsity-Induced Adaptive Filter for Multi-Clustering System Identification
Venue: arXiv cs.IT 2014
Year: 2014

In order to improve the performance of least mean square (LMS)-based adaptive filtering for identifying block-sparse systems, a new adaptive algorithm called block-sparse LMS (BS-LMS) is proposed in this paper. The basis of the proposed algorithm is to insert a penalty of block-sparsity, which is a mixed \$l_{2, 0}\$ norm of adaptive tap-weights with equal group partition sizes, into the cost function of traditional LMS algorithm. To describe a block-sparse system response, we first propose a Markov-Gaussian model, which can generate a kind of system responses of arbitrary average sparsity and arbitrary average block length using given parameters. Then we present theoretical expressions of the steady-state misadjustment and transient convergence behavior of BS-LMS with an appropriate group partition size for white Gaussian input data. Based on the above results, we theoretically demonstrate that BS-LMS has much better convergence behavior than \$l_0\$-LMS with the same small level of misadjustment. Finally, numerical experiments verify that all of the theoretical analysis agrees well with simulation results in a large range of parameters.
Axiomatizing Propositional Dependence Logics
Venue: arXiv cs.LO 2014
Year: 2014

We give sound and complete Hilbert-style axiomatizations for propositional dependence logic (PD), modal dependence logic (MDL), and extended modal dependence logic (EMDL) by extending existing axiomatizations for propositional logic and modal logic. In addition, we give novel labeled tableau calculi for PD, MDL, and EMDL. We prove soundness, completeness and termination for each of the labeled calculi.
A Parallel Stochastic Approximation Method for Nonconvex Multi-Agent Optimization Problems
Venue: arXiv cs.MA 2014
Year: 2014

Consider the problem of minimizing the expected value of a (possibly nonconvex) cost function parameterized by a random (vector) variable, when the expectation cannot be computed accurately (e.g., because the statistics of the random variables are unknown and/or the computational complexity is prohibitive). Classical sample stochastic gradient methods for solving this problem may empirically suffer from slow convergence. In this paper, we propose for the first time a stochastic parallel Successive Convex Approximation-based (best-response) algorithmic framework for general nonconvex stochastic sum-utility optimization problems, which arise naturally in the design of multi-agent systems. The proposed novel decomposition enables all users to update their optimization variables in parallel by solving a sequence of strongly convex subproblems, one for each user. Almost surely convergence to stationary points is proved. We then customize our algorithmic framework to solve the stochastic sum rate maximization problem over Single-Input-Single-Output (SISO) frequency-selective interference channels, multiple-input-multiple-output (MIMO) interference channels, and MIMO multiple-access channels. Numerical results show that our algorithms are much faster than state-of-the-art stochastic gradient schemes while achieving the same (or better) sum-rates.