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  • 601.
    Toczé, Klervie
    et al.
    Ericsson AB, Linköping, Sweden.
    Vasilevskaya, Maria
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sandahl, Patrik
    Ericsson AB, Linköping, Sweden.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Maintainability of Functional Reactive Programs in a Telecom Server Software2016In: SAC '16 Proceedings of the 31st Annual ACM Symposium on Applied Computing, Association for Computing Machinery (ACM), 2016, p. 2001-2003Conference paper (Other academic)
    Abstract [en]

    Functional Reactive Programming (FRP) is claimed to be a good choice for event handling applications. Current object- oriented telecom applications are known to suffer from additional complexity due to event handling code. In this paper we study the maintainability of FRP programs in the tele- com domain compared to traditional object-oriented programming (OOP), with the motivation that higher maintainability increases the service quality and decreases the costs. Two implementations of the same procedure are created: one using Haskell and the reactive-banana FRP frame- work and one using C++ and the OOP paradigm. Four software experts each with over 20 years of experience and three development engineers working on a product subject to study were engaged in evaluations, based on a questionnaire involving five different aspects of maintainability. The evaluations indicate a higher maintainability profile for FRP compared with OOP. This is confirmed by a more detailed analysis of the code size. While performance was not a main criteria, a preliminary evaluation shows that the OOP prototype is 8-10 times faster than the FRP prototype in the current (non-optimised) implementations.

  • 602.
    Toresson, Gabriel
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Documenting and Improving the Design of a Large-scale System2019Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    As software systems become increasingly larger and more complex, the need to make them easily maintained increases, as large systems are expected to last for many years. It has been estimated that system maintenance is a large part of many IT-departments’ software develop­ment costs. In order to design a complex system to be maintainable it is necessary to introduce structure, often as models in the form of a system architecture and a system design. As development of complex large-scale systems progresses over time, the models may need to be reconstructed. Perhaps because development may have diverted from the initial plan, or because changes had to be made during implementation. This thesis presents a reconstructed documentation of a complex large-scale system, as well as suggestions for how to improve the existing design based on identified needs and insufficiencies. The work was performed primarily using a qualitative manual code review approach of the source code, and the proposal was generated iteratively. The proposed design was evaluated and it was concluded that it does address the needs and insufficiencies, and that it can be realistically implemented.

  • 603.
    Torggler, Manfred
    et al.
    Fernuniv, Germany.
    Keller, Joerg
    Fernuniv, Germany.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asymmetric Crown Scheduling2017In: 2017 25TH EUROMICRO INTERNATIONAL CONFERENCE ON PARALLEL, DISTRIBUTED AND NETWORK-BASED PROCESSING (PDP 2017), IEEE , 2017, p. 421-425Conference paper (Refereed)
    Abstract [en]

    Streaming applications are often used for embedded and high-performance multi and manycore processors. Achieving high throughput without wasting energy can be achieved by static scheduling of parallelizable tasks with frequency scaling. We present asymmetric crown scheduling, which improves on the static crown scheduling approach by allowing flexible split ratios when subdividing processor groups. We formulate the scheduler as an integer linear program and evaluate it with synthetic task sets. The results demonstrate that a small number of split ratios improves energy efficiency of crown schedules by up to 12% with slightly higher scheduling time.

  • 604.
    Tufvesson, Hampus
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Impact of automated validation on software model quality2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Model driven development is gaining momentum, and thus, larger and more complex systems are being represented and developed with the help of modeling. Complex systems often suffer from a number of problems such as difficulties in keeping the model understandable, long compilation times and high coupling. With modeling comes the possibility to validate the models against constraints, which makes it possible to handle problems that traditional static analysis tools can't solve. This thesis is a study on to what degree the usage of automatic model validation can be a useful tool in addressing some of the problems that appear in the development of complex systems. This is done by compiling a list of validation constraints based on existing problems, implementing and applying fixes for these and measuring how a number of different aspects of the model is affected. After applying the fixes and measuring the impact on the models ,it could be seen that validation of dependencies can have a signicant impact on the models by reducing build times of the generated code. Other types of validation constraints require further study to decide what impact they might have on model quality.

  • 605.
    Törnblom, John
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    An Abstraction-Refinement Approach to Formal Verification of Tree Ensembles2019In: Computer Safety, Reliability, and Security: SAFECOMP 2019 Workshops, ASSURE, DECSoS, SASSUR, STRIVE, and WAISE, Turku, Finland, September 10, 2019, Proceedings, Springer, 2019, p. 301-313Conference paper (Refereed)
    Abstract [en]

    Recent advances in machine learning are now being considered for integration in safety-critical systems such as vehicles, medical equipment and critical infrastructure. However, organizations in these domains are currently unable to provide convincing arguments that systems integrating machine learning technologies are safe to operate in their intended environments.

    In this paper, we present a formal verification method for tree ensembles that leverage an abstraction-refinement approach to counteract combinatorial explosion. We implemented the method as an extension to a tool named VoTE, and demonstrate its applicability by verifying the robustness against perturbations in random forests and gradient boosting machines in two case studies. Our abstraction-refinement based extension to VoTE improves the performance by several orders of magnitude, scaling to tree ensembles with up to 50 trees with depth 10, trained on high-dimensional data.

  • 606.
    Törnblom, John
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Formal Verification of Random Forests in Safety-Critical Applications2019In: Formal Techniques for Safety-Critical Systems, Springer, 2019, p. 55-71Conference paper (Refereed)
    Abstract [en]

    Recent advances in machine learning and artificial intelligence are now being applied in safety-critical autonomous systems where software defects may cause severe harm to humans and the environment. Design organizations in these domains are currently unable to provide convincing arguments that systems using complex software implemented using machine learning algorithms are safe and correct.

    In this paper, we present an efficient method to extract equivalence classes from decision trees and random forests, and to formally verify that their input/output mappings comply with requirements. We implement the method in our tool VoRF (Verifier of Random Forests), and evaluate its scalability on two case studies found in the literature. We demonstrate that our method is practical for random forests trained on low-dimensional data with up to 25 decision trees, each with a tree depth of 20. Our work also demonstrates the limitations of the method with high-dimensional data and touches upon the trade-off between large number of trees and time taken for verification.

  • 607.
    Udd, Robert
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Anomaly Detection in SCADA Network Traffic2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Critical infrastructure provides us with the most important parts of modern society, electricity, water and transport. To increase efficiency and to meet new demands from the customer remote monitoring and control of the systems is necessary. This opens new ways for an attacker to reach the Supervisory Control And Data Acquisition (SCADA) systems that control and monitors the physical processes involved. This also increases the need for security features specially designed for these settings. Anomaly-based detection is a technique suitable for the more deterministic SCADA systems. This thesis uses a combination of two techniques to detect anomalies. The first technique is an automatic whitelist that learns the behavior of the network flows. The second technique utilizes the differences in arrival times of the network packets. A prototype anomaly detector has been developed in Bro. To analyze the IEC 60870-5-104 protocol a new parser for Bro was also developed. The resulting anomaly detector was able to achieve a high detection rate for three of the four different types of attacks evaluated. The studied methods of detection are promising when used in a highly deterministic setting, such as a SCADA system.

  • 608.
    Udd, Robert
    et al.
    Sectra AB, Linköping, Sweden.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Kazemtabrizi, Mehrdad
    The Royal Institute of Technology, Stockholm, Sweden.
    Ekstedt, Mathias
    The Royal Institute of Technology, Stockholm, Sweden.
    Exploiting Bro for Intrusion Detection in a SCADA System2016In: Proceedings of the 2nd ACM International Workshop on Cyber-Physical System Security, ACM Digital Library, 2016, p. 44-51Conference paper (Refereed)
    Abstract [en]

    Supervisory control and data acquisition (SCADA) systemsthat run our critical infrastructure are increasingly run withInternet-based protocols and devices for remote monitoring.The embedded nature of the components involved, and thelegacy aspects makes adding new security mechanisms in anefficient manner far from trivial. In this paper we studyan anomaly detection based approach that enables detect-ing zero-day malicious threats and benign malconfigurationsand mishaps. The approach builds on an existing platform(Bro) that lends itself to modular addition of new proto-col parsers and event handling mechanisms. As an examplewe have shown an application of the technique to the IEC-60870-5-104 protocol and tested the anomaly detector withmixed results. The detection accuracy and false positiverate, as well as real-time response was adequate for 3 ofour 4 created attacks. We also discovered some additionalwork that needs to be done to an existing protocol parser toextend its reach.

  • 609.
    Ukhov, Ivan
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    System-Level Analysis and Design under Uncertainty2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    One major problem for the designer of electronic systems is the presence of uncertainty, which is due to phenomena such as process and workload variation. Very often, uncertainty is inherent and inevitable. If ignored, it can lead to degradation of the quality of service in the best case and to severe faults or burnt silicon in the worst case. Thus, it is crucial to analyze uncertainty and to mitigate its damaging consequences by designing electronic systems in such a way that uncertainty is effectively and efficiently taken into account.

    We begin by considering techniques for deterministic system-level analysis and design of certain aspects of electronic systems. These techniques do not take uncertainty into account, but they serve as a solid foundation for those that do. Our attention revolves primarily around power and temperature, as they are of central importance for attaining robustness and energy efficiency. We develop a novel approach to dynamic steady-state temperature analysis of electronic systems and apply it in the context of reliability optimization.

    We then proceed to develop techniques that address uncertainty. The first technique is designed to quantify the variability in process parameters, which is induced by process variation, across silicon wafers based on indirect and potentially incomplete and noisy measurements. The second technique is designed to study diverse system-level characteristics with respect to the variability originating from process variation. In particular, it allows for analyzing transient temperature profiles as well as dynamic steady-state temperature profiles of electronic systems. This is illustrated by considering a problem of design-space exploration with probabilistic constraints related to reliability. The third technique that we develop is designed to efficiently tackle the case of sources of uncertainty that are less regular than process variation, such as workload variation. This technique is exemplified by analyzing the effect that workload units with uncertain processing times have on the timing-, power-, and temperature-related characteristics of the system under consideration.

    We also address the issue of runtime management of electronic systems that are subject to uncertainty. In this context, we perform an early investigation into the utility of advanced prediction techniques for the purpose of fine-grained long-range forecasting of resource usage in large computer systems.

    All the proposed techniques are assessed by extensive experimental evaluations, which demonstrate the superior performance of our approaches to analysis and design of electronic systems compared to existing techniques.

  • 610.
    Ukhov, Ivan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Bao, Min
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, The Institute of Technology.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Steady-State Dynamic Temperature Analysis and Reliability Optimization for Embedded Multiprocessor Systems2012In: 49th ACM/EDAC/IEEE Design Automation Conference (DAC), 3-7 June 2012, San Francisco, ACM/ IEEE , 2012, p. 197-204Conference paper (Refereed)
    Abstract [en]

    In this paper we propose an analytical technique for the steady-state dynamic temperature analysis (SSDTA) of multiprocessor systems with periodic applications. The approach is accurate and, moreover, fast, such that it can be included inside an optimization loop for embedded system design. Using the proposed solution, a temperature-aware reliability optimization, based on the thermal cycling failure mechanism, is presented. The experimental results con firm the quality and speed of our SSDTA technique, compared to the state of the art. They also show that the lifetime of an embedded system can significantly be improved, without sacrificing its energy efficiency, by taking into consideration, during the design stage, the steady-state dynamic temperature profile of the system.

  • 611.
    Ukhov, Ivan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Probabilistic Analysis of Electronic Systems via Adaptive Hierarchical Interpolation2017In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 36, no 11, p. 1883-1896Article in journal (Refereed)
    Abstract [en]

    We present a framework for system-level analysis of electronic systems whose runtime behaviors depend on uncertain parameters. The proposed approach thrives on hierarchical interpolation guided by an advanced adaptation strategy, which makes the framework general and suitable for studying various metrics that are of interest to the designer. Examples of such metrics include the end-to-end delay, total energy consumption, and maximum temperature of the system under consideration. The framework delivers a light generative representation that allows for a straightforward, computationally efficient calculation of the probability distribution and accompanying statistics of the metric at hand. Our technique is illustrated by considering a number of uncertainty-quantification problems and comparing the corresponding results with exhaustive simulations.

  • 612.
    Ukhov, Ivan
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Probabilistic Analysis of Power and Temperature Under Process Variation for Electronic System Design2014In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 33, no 6, p. 931-944Article in journal (Refereed)
    Abstract [en]

    Electronic system design based on deterministic techniques for power-temperature analysis is, in the context of current and future technologies, both unreliable and inefficient since the presence of uncertainty, in particular, due to process variation, is disregarded. In this paper, we propose a flexible probabilistic framework targeted at the quantification of the transient power and temperature variations of an electronic system. The framework is capable of modeling diverse probability laws of the underlying uncertain parameters and arbitrary dependencies of the system on such parameters. For the considered system, under a given workload, our technique delivers analytical representations of the corresponding stochastic power and temperature profiles. These representations allow for a computationally efficient estimation of the probability distributions and accompanying quantities of the power and temperature characteristics of the system. The approximation accuracy and computational time of our approach are assessed by a range of comparisons with Monte Carlo simulations, which confirm the efficiency of the proposed technique.

  • 613.
    Ukhov, Ivan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Temperature-Centric Reliability Analysis and Optimization of Electronic Systems under Process Variation2015In: IEEE Transactions on Very Large Scale Integration (vlsi) Systems, ISSN 1063-8210, E-ISSN 1557-9999, Vol. 23, no 11, p. 2417-2430Article in journal (Refereed)
    Abstract [en]

    Electronic system designs that ignore process variationare unreliable and inefficient. In this paper, we propose asystem-level framework for the analysis of temperature-inducedfailures that considers the uncertainty due to process variation.As an intermediate step, we also develop a probabilistic techniquefor dynamic steady-state temperature analysis. Given an electronicsystem under a certain workload, our framework deliversthe corresponding survival function, founded on the basis ofwell-established reliability models, with a closed-form stochasticparameterization in terms of the quantities that are uncertain atthe design stage. The proposed solution is exemplified consideringsystems with periodic workloads that suffer from the thermalcyclingfatigue. The analysis of this fatigue is a challengingproblem as it requires the availability of detailed temperatureprofiles, which are uncertain due to the variability of processparameters. To demonstrate the computational efficiency of ourframework, we undertake a design-space exploration procedureto minimize the expected energy consumption under a set oftiming, thermal, and reliability constraints.

  • 614.
    Ukhov, Ivan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Marculescu, Diana
    Department of Electrical and Computer Engineering, Carnegie Mellon University, USA.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fast Synthesis of Power and Temperature Profiles for the Development of Data-Driven Resource Managers2017Report (Other academic)
    Abstract [en]

    The goal of this work is to facilitate the development of proactive power- and temperature-aware resource managers that leverage machine learning in order to attain their objectives. In this context, the availability of sufficiently large amounts of relevant data, which are essential for learning and, therefore, exploration of research ideas, is elusive. In order to fulfill the need, we present a toolchain for fast generation of realistic power and temperature profiles of computer systems. The toolchain provides profuse representative data to learn from during development stages. The overreaching objective is to help research by making it tractable to experiment with the highly promising but data-demanding state-of-the-art techniques for prediction.

  • 615.
    Ukhov, Ivan
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Marculescu, Diana
    Department of Electrical and Computer Engineering, Carnegie Mellon University, USA.
    Eles, Petru Ion
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fine-Grained Long-Range Prediction of Resource Usage in Computer Clusters2017Report (Other academic)
    Abstract [en]

    In order to facilitate the development of intelligent resource managers of computer clusters, we investigate the utility of the state-of-the-art neural networks for the purpose of fine-grained long-range prediction of the resource usage in one such cluster. We consider a large data set of real-life traces and describe in detail our workflow, starting from making the data accessible for learning and finishing by predicting the resource usage of individual tasks multiple steps ahead. The experimental results indicate that such fine-grained traces as the ones considered possess a certain structure, and that this structure can be extracted by advanced machine-learning techniques and subsequently utilized for making informed predictions.

  • 616.
    Ukhov, Ivan
    et al.
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Villani, Mattias
    Linköping University, Department of Computer and Information Science, Statistics. Linköping University, Faculty of Arts and Sciences.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory. Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Statistical Analysis of Process Variation Based on Indirect Measurements for Electronic System Design2014In: 2014 19TH ASIA AND SOUTH PACIFIC DESIGN AUTOMATION CONFERENCE (ASP-DAC), New York: IEEE conference proceedings, 2014, p. 436-442Conference paper (Refereed)
    Abstract [en]

    We present a framework for the analysis of process variation across semiconductor wafers. The framework is capable of quantifying the primary parameters affected by process variation, e.g., the effective channel length, which is in contrast with the former techniques wherein only secondary parameters were considered, e.g., the leakage current. Instead of taking direct measurements of the quantity of interest, we employ Bayesian inference to draw conclusions based on indirect observations, e.g., on temperature. The proposed approach has low costs since no deployment of expensive test structures might be needed or only a small subset of the test equipments already deployed for other purposes might need to be activated. The experimental results present an assessment of our framework for a wide range of configurations.

  • 617.
    Uppman, Hannes
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Computational Complexity of the Minimum Cost Homomorphism Problem on Three-element Domains2014Conference paper (Refereed)
    Abstract [en]

    In this paper we study the computational complexity of the extended minimum cost homomorphism problem (Min-Cost-Hom) as a function of a constraint language, i.e. a set of constraint relations and cost functions that are allowed to appear in instances. A wide range of natural combinatorial optimisation problems can be expressed as extended Min-Cost-Homs and a classification of their complexity would be highly desirable, both from a direct, applied point of view as well as from a theoretical perspective.

    The extended Min-Cost-Hom can be understood either as a flexible optimisation version of the constraint satisfaction problem (CSP) or a restriction of the (general-valued) valued constraint satisfaction problem (VCSP). Other optimisation versions of CSPs such as the minimum solution problem (Min-Sol) and the minimum ones problem (Min-Ones) are special cases of the extended Min-Cost-Hom.

    The study of VCSPs has recently seen remarkable progress. A complete classification for the complexity of finite-valued languages on arbitrary finite domains has been obtained Thapper and Živný [STOC’13]. However, understanding the complexity of languages that are not finitevalued appears to be more difficult. The extended Min-Cost-Hom allows us to study problematic languages of this type without having to deal with with the full generality of the VCSP. A recent classification for the complexity of three-element Min-Sol, Uppman [ICALP’13], takes a step in this direction. In this paper we generalise this result considerably by determining the complexity of three-element extended Min-Cost-Hom.

  • 618.
    Uppman, Hannes
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Max-Sur-CSP on Two Elements2012In: Principles and Practice of Constraint Programming: 18th International Conference, CP 2012, Québec City, QC, Canada, October 8-12, 2012. Proceedings / [ed] Michela Milano, Springer Berlin Heidelberg , 2012, p. 38-54Conference paper (Refereed)
    Abstract [en]

    Max-Sur-CSP is the following optimisation problem: given a set of constraints, find a surjective mapping of the variables to domain values that satisfies as many of the constraints as possible. Many natural problems, e.g. Minimum k-Cut (which has many different applications in a variety of fields) and Minimum Distance (which is an important problem in coding theory), can be expressed as Max-Sur-CSPs. We study Max-Sur-CSP on the two-element domain and determine the computational complexity for all constraint languages (families of allowed constraints). Our results show that the problem is solvable in polynomial time if the constraint language belongs to one of three classes, and NP-hard otherwise. An important part of our proof is a polynomial-time algorithm for enumerating all near-optimal solutions to a generalised minimum cut problem. This algorithm may be of independent interest.

  • 619.
    Uppman, Hannes
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    On Some Combinatorial Optimization Problems: Algorithms and Complexity2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is about the computational complexity of several classes of combinatorial optimization problems, all related to the constraint satisfaction problems.

    A constraint language consists of a domain and a set of relations on the domain. For each such language there is a constraint satisfaction problem (CSP). In this problem we are given a set of variables and a collection of constraints, each of which is constraining some variables with a relation in the language. The goal is to determine if domain values can be assigned to the variables in a way that satisfies all constraints. An important question is for which constraint languages the corresponding CSP can be solved in polynomial time. We study this kind of question for optimization problems related to the CSPs.

    The main focus is on extended minimum cost homomorphism problems. These are optimization versions of CSPs where instances come with an objective function given by a weighted sum of unary cost functions, and where the goal is not only to determine if a solution exists, but to find one of minimum cost. We prove a complete classification of the complexity for these problems on three-element domains. We also obtain a classification for the so-called conservative case.

    Another class of combinatorial optimization problems are the surjective maximum CSPs. These problems are variants of CSPs where a non-negative weight is attached to each constraint, and the objective is to find a surjective mapping of the variables to values that maximizes the weighted sum of satisfied constraints. The surjectivity requirement causes these problems to behave quite different from for example the minimum cost homomorphism problems, and many powerful techniques are not applicable. We prove a dichotomy for the complexity of the problems in this class on two-element domains. An essential ingredient in the proof is an algorithm that solves a generalized version of the minimum cut problem. This algorithm might be of independent interest.

    In a final part we study properties of NP-hard optimization problems. This is done with the aid of restricted forms of polynomial-time reductions that for example preserves solvability in sub-exponential time. Two classes of optimization problems similar to those discussed above are considered, and for both we obtain what may be called an easiest NP-hard problem. We also establish some connections to the exponential time hypothesis.

  • 620.
    Uppman, Hannes
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    The Complexity of Three-Element Min-Sol and Conservative Min-Cost-Hom2013In: Automata, Languages, and Programming: 40th International Colloquium, ICALP 2013, Riga, Latvia, July 8-12, 2013, Proceedings, Part I / [ed] Fedor V. Fomin, Rūsiņš Freivalds, Marta Kwiatkowska, David Peleg, Springer Berlin/Heidelberg, 2013, p. 804-815Conference paper (Refereed)
    Abstract [en]

    Thapper and Živný [STOC’13] recently classified the complexity of VCSP for all finite-valued constraint languages. However, the complexity of VCSPs for constraint languages that are not finite-valued remains poorly understood. In this paper we study the complexity of two such VCSPs, namely Min-Cost-Hom and Min-Sol. We obtain a full classification for the complexity of Min-Sol on domains that contain at most three elements and for the complexity of conservative Min-Cost-Hom on arbitrary finite domains. Our results answer a question raised by Takhanov [STACS’10, COCOON’10].

  • 621.
    Usman, Muhammad
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Framework for Within Day Rescheduling due to UnexpectedIncidents in Transportation Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In activity based modelling the concept of rescheduling is very important in order to gain dynamic scheduling of activities and to adjust the effect of unexpected incidents in individual agendas to keep them realistic and valid. This report describes a new framework to investigate algorithms for rescheduling on a large scale. This framework models the information of traffic demand and results of micro simulation of traffic on a loaded network; it enables agents to adapt their schedules by providing them with information about the traffic flow. A perception filter for each agent is included in this framework. It models the concept that some agents can notice the broadcast traffic information about the incident and get their own prediction of the expected delay, while other agents who do not notice the information can become aware only by experiencing traffic jam. Initial agendas are created by means of the FEATHERS activity based schedule generator for mutually independent agents. FEATHERS has no knowledge about the actual transportation network but makes use of an impedance matrix that specifies the minimal travel time between traffic analysis zones. The matrix specifies a free-flow value for the uncongested case and correction values for the loaded network. In this new framework the network state can be changed by agent behaviour and external incidents; the effect of this change in network state is perceived differently by each agent through a perception filter, and according to the perceived value individual adaption is calculated by a ReScheduler. The modified behaviour again creates new traffic demand hence creating a new traffic state; this phenomenon continues for the complete day. Each activity in the agenda is assumed to generate some utility. Each individual is assumed to maximize the total utility over the day. The ReScheduler is implemented using a marginal utility function that monotonically decreases with activity duration. This results in a monotonically converging relaxation algorithm to efficiently determine the new activity timing when less time is available for activities due to increased travel time caused by the incident.

  • 622.
    Vasconcelos Jansson, Erik Sven
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Analysis of Test Coverage Data on a Large-Scale Industrial System2016Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Software testing verifies the program's functional behavior, one important process when engineering critical software. Measuring the degree of testing is done with code coverage, describing the amount of production code affected by tests. Both concepts are extensively used for industrial systems. Previous research has shown that gathering and analyzing test coverages becomes problematic on large-scale systems. Here, development experience, implementation feasibility, coverage measurements and analysis method are explored; providing potential solutions and insights into these issues.

    Outlined are methods for constructing and integrating such gathering and analysis system in a large-scale project, along with the problems encountered and given remedies. Instrumentations for gathering coverage information affect performance negatively, these measurements are provided. Since large-scale test suite measurements are quite lacking, the line, branch, and function criteria are presented here. Finally, an analysis method is proposed, by using coverage set operations and Jaccard indices, to find test similarities.

    Results gathered imply execution time was significantly affected when gathering coverage, [2.656, 2.911] hours for instrumented software, originally between [2.075, 2.260] on the system under test, given under the alpha = 5% and n = 4, while both processor & memory usages were inconclusive. Measured criteria were (59.3, 70.7, 24.6)% for these suites. Analysis method shows potential areas of test redundancy.

  • 623.
    Vasilevskaya, Maria
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Software and Systems.
    Ariani Gunawan, Linda
    Norwegian University of Science and Technology, NTNU.
    Nadjm-Tehrani, Simin
    Linköping University, The Institute of Technology. Linköping University, Department of Computer and Information Science, Software and Systems.
    Herrmann, Peter
    Norwegian University of Science and Technology, NTNU.
    Integrating security mechanisms into embedded systems by domain-specific modelling2014In: Security and Communication Networks, ISSN 1939-0114, E-ISSN 1939-0122, Vol. 7, no 12, p. 2815-2832Article in journal (Refereed)
    Abstract [en]

    Embedded devices are crucial enablers of the Internet of Things and become increasingly common in our daily life. They store, manipulate and transmit sensitive information and, therefore, must be protected against security threats. Due to the security and also resource constraint concerns, designing secure networked embedded systems is a difficult task. Model-based development (MBD) is promoted to address complexity and ease the design of software intensive systems. We leverage MBD and domain-specific modelling to characterise common issues related to security and embedded systems that are specific to a given application domain. Security-specific knowledge relevant for a certain application domain is represented in the form of an adapted information security ontology. Further, the elements of the ontology are associated with security building blocks modelled with the MBD method SPACE. The selection of relevant security building blocks is based on (i) assets automatically elicited from the functional models, (ii) domain security knowledge captured by the security expert and (iii) the platform adopted by the embedded system engineer. A tool is developed to support the steps supporting this methodology and help to bridge between the security and embedded systems domains. We illustrate our approach with a case study from the smart metering domain.

  • 624.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Broman, David
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Sandahl, Kristian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    An Assessment Model for Large Project Courses2014In: Proceedings of the 45th ACM Technical Symposium on Computer Science Education (SIGCSE), Association for Computing Machinery (ACM), 2014Conference paper (Refereed)
    Abstract [en]

    Larger project courses, such as capstone projects, are essential in a modern computing curriculum. Assessing such projects is, how- ever, extremely challenging. There are various aspects and trade-offs of assessments that can affect the quality of a project course. Individual assessments can give fair grading of individuals, but may loose focus of the project as a group activity. Extensive teacher involvement is necessary for objective assessment, but may affect the way students are working. Continuous feedback to students can enhance learning, but may be hard to combine with fair assessment. Most previous work is focusing on some specific assessment aspect, whereas we in this paper present an assessment model that consists of a collection of assessment activities, each covering different aspects. We have applied, developed, and improved these activities during a six-year period and evaluated their usefulness by performing a questionnaire-based survey.

  • 625.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Broman, David
    KTH Royal Institute of Technology, Stockholm, Sweden; University of California, Berkeley, USA.
    Sandahl, Kristian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Assessing Large Project Courses: Model, Activities, and Lessons Learned2015In: ACM Transactions on Computing Education, ISSN 1946-6226, E-ISSN 1946-6226, Vol. 15, no 4, p. 20:1-20:30Article in journal (Refereed)
    Abstract [en]

    In a modern computing curriculum, large project courses are essential to give students hands-on experience of working in a realistic software engineering project. Assessing such projects is, however, extremely challenging. There are various aspects and tradeoffs of assessments that can affect the course quality. Individual assessments can give fair grading of individuals, but may loose focus of the project as a group activity. Extensive teacher involvement is necessary for objective assessment, but may affect the way students are working. Continuous feedback to students can enhance learning, but may be hard to combine with fair assessment. Most previous work is focusing on some specific assessment aspect, whereas we in this paper present an assessment model that consists of a collection of assessment activities, each covering different aspects. We have applied, developed, and improved these activities during a seven-year period. To evaluate the usefulness of the model, we perform questionnaire-based surveys over a two-years period. Furthermore, we design and execute an experiment that studies to what extent students can perform fair peer assessment and to what degree the assessments of students and teachers agree. We analyze the results, discuss findings, and summarize lessons learned.

  • 626.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Linda, Ariani Gunawan
    Norwegian University of Science and Technology, Trondheim, Norway.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Peter, Herrmann
    Norwegian University of Science and Technology, Trondheim, Norway.
    Security Asset Elicitation for Collaborative Models2012In: MDsec '12 Proceedings of the Workshop on Model-Driven Security, ACM Digital Library , 2012Conference paper (Refereed)
    Abstract [en]

    Building secure systems is a difficult job for most engineers since it requires in-depth understanding of security aspects. This task, however, can be assisted by capturing security knowledge in a particular domain and reusing the knowl- edge when designing applications. We use this strategy and employ an information security ontology to represent the se- curity knowledge. The ontology is associated with system designs which are modelled in collaborative building blocks specifying the behaviour of several entities. In this paper, we identify rules to be applied to the elements of collaborations in order to identify security assets present in the design. Further, required protection mechanisms are determined by applying a reasoner to the ontology and the obtained assets. We exemplify our approach with a case study from the smart metering domain. 

  • 627.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Model-based Security Risk Analysis for Networked Embedded Systems2016In: Critical Information Infrastructures Security: 9th International Conference, CRITIS 2014 Limassol, Cyprus, October 13–15, 2014 Revised Selected Papers / [ed] Panayiotou C., Ellinas G., Kyriakides E., Polycarpou M., Springer, 2016, p. 381-386Conference paper (Refereed)
    Abstract [en]

    Finding a balance between functional and non-functional requirements and resources in embedded systems has always been a challenge. What brings this challenge into a sharper focus is that embedded devices are increasingly deployed in many networked applications, some of which will form the backbone of the critical information infrastructures on which we all depend. The Security-Enhanced Embedded system Development (SEED) process has proposed a set of tools that a bridge the two islands of expertise, the engineers specialised in embedded systems development and the security experts. This paper identifies a gap in the tool chain that links the identification of assets to be protected to the associated security risks seen from different stakeholder perspectives. The needed tool support for systematic prioritisation of identified assets, and the selection of security building blocks at design stage based on a risk picture of different stakeholders, are characterised. The ideas are illustrated in a smart metering infrastructure scenario.

  • 628.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Quantifying Risks to Data Assets Using Formal Metrics in Embedded System Design2015In: Computer Safety, Reliability, and Security: 34th International Conference, SAFECOMP 2015, Delft, The Netherlands, September 23-25, 2015, Proceedings / [ed] Floor Koornneef; Coen van Gulijk, Springer, 2015, Vol. 9337, p. 347-361Conference paper (Refereed)
    Abstract [en]

    This paper addresses quantifying security risks associated with data assets within design models of embedded systems. Attack and system behaviours are modelled as time-dependent stochastic processes. The presence of the time dimension allows accounting for dynamic aspects of potential attacks and a system: the probability of a success- ful attack changes as time progresses; and a system possesses different data assets as its execution unfolds. These models are used to quan- tify two important attributes of security: confidentiality and integrity. In particular, likelihood/consequence-based measures of confidentiality and integrity losses are proposed to characterise security risks to data assets. In our method, we consider attack and system behaviours as two sepa- rate models that are later elegantly combined for security analysis. This promotes knowledge reuse and avoids adding extra complexity in the system design process. We demonstrate the effectiveness of the proposed method and metrics on smart metering devices. 

  • 629.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Quantifying Risks to Data Assets Using Formal Metrics in Embedded System Design2015In: Computer safety, reliability, and security : 34th International Conference, SAFECOMP 2015, Delft, the Netherlands, September 22, 2015, Proceedings, Springer, 2015, p. 347-361Conference paper (Refereed)
    Abstract [en]

    This paper addresses quantifying security risks associated with data assets within design models of embedded systems. Attack and system behaviours are modelled as time-dependent stochastic processes. The presence of the time dimension allows accounting for dynamic aspects of potential attacks and a considered system: the probability of a successful attack may change as time progresses; and a system may possess different data assets as its execution unfolds. For system modelling, we employ semi-Markov chains that are a powerful tool to capture system dynamics. For attack modelling, we adapt existing formalisms of attack trees and attack graphs. These models are used to analyse and quantify two important attributes of security: confidentiality and integrity. In particular, likelihood/consequence-based measures of confidentiality and integrity losses are proposed to characterise security risks to data assets. Identifying these risks in embedded systems is especially relevant in order to be able to trade them off against other constraints, e.g. limited resources. In our method, we consider attack and system behaviours as two separate models that are later elegantly combined for security analysis. This promotes knowledge reuse and avoids adding extra complexity in the system design process. We demonstrate the effectiveness of the proposed method and metrics on real smart metering devices.

  • 630.
    Vasilevskaya, Maria
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Support for Cross-domain Composition of Embedded Systems Using MARTE Models2015In: ACM SIGBED Review, ISSN 1551-3688, p. 37-45Article in journal (Refereed)
    Abstract [en]

    Abstract—Embedded systems have evolved from tailormade systems developed by specialist engineers to artefacts built from complex software/hardware components with many extra-functional concerns. Ubiquity of embedded devices demands other facets such as security and safety to be brought to the fore- front. At the same time, cost efficiency dictates building systems from reusable building blocks. However, integration of extra- functional building blocks comes with a certain performance resource overhead that must be taken into consideration while designing resource-constraint embedded systems. This paper builds on the premise that functional models can be extended with platform modelling to help the application engineers to select the right extra-functional building blocks accounting for performance implications of their integration. We define a UML profile relating it to relevant parts of the MARTE profile in order to capture the performance analysis results for a reusable building block, and a generic notion of model-based compatibility analysis for platform models. Additionally, our approach rests on creation of ontologies to store MARTE description of hardware components, and is supported by a MagicDraw plugin developed for capturing the analysis results and performing the compatibility analysis.

  • 631.
    Vergara Alonso, Ekhiotz Jon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Energy Modelling and Fairness for Efficient Mobile Communication2016Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Energy consumption and its management have been clearly identified as a challenge in computing and communication system design, where energy economy is obviously of paramount importance for battery powered devices. This thesis addresses the energy efficiency of mobile communication at the user end in the context of cellular networks.

    We argue that energy efficiency starts by energy awareness and propose EnergyBox, a parametrised tool that enables accurate and repeatable energy quantification at the user end using real data traffic traces as input. EnergyBox offers an abstraction of the underlying states for operation of the wireless interfaces and allows to estimate the energy consumption for different operator settings and device characteristics. The tool is used throughout the thesis to quantify and reveal inefficient data communication patterns of widely used mobile applications.

    We consider two different perspectives in the search of energy-efficient solutions. From the application perspective, we show that systematically quantifying the energy consumption of design choices (e.g., communication patterns, protocols, and data formats) contributes to a significantly smaller energy footprint. From the system perspective, we devise a cross-layer solution that schedules packet transmissions based on the knowledge of the network parameters that impact the energy consumption of the handset. These attempts show that application level decisions require a better understanding of possible energy apportionment policies at system level.

    Finally, we study the generic problem of determining the contribution of an entity (e.g., application) to the total energy consumption of a given system (e.g., mobile device). We compare the state-of-the-art policies in terms of fairness leveraging cooperative game theory and analyse their required information and computational complexity. We show that providing incentives to reduce the total energy consumption of the system (as part of fairness) is tightly coupled to the policy selection. Our study provides guidelines to select an appropriate policy depending on the characteristics of the system. 

  • 632.
    Vergara Alonso, Ekhiotz Jon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Exploiting Energy Awareness in Mobile Communication2013Licentiate thesis, monograph (Other academic)
    Abstract [en]

    Although evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions hamper the quality of experience to a great extent. The massive explosion of mobile applications with the ensuing data exchange over the cellular infrastructure is not only a blessing to the mobile user, but also has a price in terms of rapid discharge of the device battery. Wireless communication is a large contributor to the energy consumption. Thus, the current call for energy economy in mobile devices poses the challenge of reducing the energy consumption of wireless data transmissions at the user end by developing energy-efficient communication.

    This thesis addresses the energy efficiency of data transmission at the user end in the context of cellular networks. We argue that the design of energy-efficient solutions starts by energy awareness and propose EnergyBox, a parametrised tool that enables accurate and repeatable energy quantification at the user end using real data traffic traces as input. EnergyBox abstracts the underlying states for operation of the wireless interfaces and allows to estimate the energy consumption for different operator settings and device characteristics.

    Next, we devise an energy-efficient algorithm that schedules the packet transmissions at the user end based on the knowledge of the network parameters that impact the handset energy consumption. The solution focuses on the characteristics of a given traffic class with the lowest quality of service requirements. The cost of running the solution itself is studied showing that the proposed cross-layer scheduler uses a small amount of energy to significantly extend the battery lifetime at the cost of some added latency. 

    Finally, the benefit of employing EnergyBox to systematically study the different design choices that developers face with respect to data transmissions of applications is shown in the context of location sharing services and instant messaging applications. The results show that quantifying energy consumption of communication patterns, protocols, and data formats can aid the design of tailor-made solutions with a significantly smaller energy footprint. 

  • 633.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Andersson, Simon
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    When Mice Consume Like Elephants: Instant Messaging Applications2014In: e-Energy '14: Proceedings of the 5th international conference on Future energy systems, ACM Press, 2014, p. 97-107Conference paper (Refereed)
    Abstract [en]

    A recent surge in the usage of instant messaging (IM) applications on mobile devices has brought the energy efficiency of these applications into focus of attention. Although IM applications are changing the message communication landscape, this work illustrates that the current versions of IM applications differ vastly in energy consumption when using the third generation (3G) cellular communication. This paper shows the interdependency between energy consumption and IM data patterns in this context. We analyse the user interaction pattern using a IM dataset, consisting of 1043370 messages collected from 51 mobile users. Based on the usage characteristics, we propose a message bundling technique that aggregates consecutive messages over time, reducing the energy consumption with a trade-off against latency. The results show that message bundling can save up to 43% in energy consumption while still maintaining the conversation function. Finally, the energy cost of a common functionality used in IM applications that informs that the user is currently typing a response, so called typing notification, is evaluated showing an energy increase ranging from 40-104%.

  • 634.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    EnergyBox: A Trace-driven Tool for Data Transmission Energy Consumption Studies2013In: EE-LSDS 2013, Energy Efficiency in Large Scale Distributed Systems, Springer, 2013, p. 19-34Conference paper (Refereed)
    Abstract [en]

    Although evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions hamper the quality of experience to a great extent. We argue that the design of energy-efficient solutions starts by energy-awareness and propose EnergyBox, a tool that provides accurate and repeatable energy consumption studies for 3G and WiFi transmissions at the user end. We recognize that the energy consumption of data transmission is highly dependable on the traffic pattern, and provide the means for trace-based iterative packet-driven simulation to derive the operation states of wireless interfaces. The strength of EnergyBox is that it allows to modularly set the 3G network parameters specified at operator level, the adaptive power save mode mechanism for a WiFi device, and the different power levels of the operation states for different handheld devices. EnergyBox enables efficient energy consumption studies using real data, which complements the device-dependent laborious physical power measurements. Using real application transmission traces, we have validated EnergyBox showing an accuracy range of 94-99% for 3G and 93-99% for WiFi compared to the real measured energy consumption by a 3G modem and a smartphone with WiFi.

  • 635.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fairness and Incentive Considerations in Energy Apportionment Policies2016In: ACM Transactions on Modeling and Performance Evaluation of Computing Systems, ISSN 2376-3639, Vol. 2, no 1Article in journal (Refereed)
    Abstract [en]

    The energy consumption of a system is determined by the system component usage patterns and interactions between the coexisting entities and resources. Energy accounting plays an essential role to reveal the contribution of each entity to the total consumption and for energy management. Unfortunately, energy accounting inherits the apportionment problem of accounting in general, which does not have a general single best solution. In this paper we leverage cooperative game theory commonly used in cost allocation problems to study the energy apportionment problem, i.e., the problem of prescribing the actual energy consumption of a system to the consuming entities (e.g., applications, processes or users of the system).

    We identify five relevant fairness properties for energy apportionment and present a detailed categorisation and analysis of eight previously proposed energy apportionment policies from different fields in computer and communication systems. In addition, we propose two novel energy apportionment policies based on cooperative game theory which provide strong fairness notion and a rich incentive structure. Our comparative analysis in terms of the identified five fairness properties as well as information requirement and computational complexity shows that there is a trade-off between fairness and the other evaluation criteria. We provide guidelines to select an energy apportionment policy depending on the purpose of the apportionment and the characteristics of the system.

  • 636.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Watts2Share: Energy-Aware Traffic Consolidation2013In: Green Computing and Communications (GreenCom), 2013 IEEE and Internet of Things (iThings/CPSCom), IEEE International Conference on and IEEE Cyber, Physical and Social Computing, IEEE Computer Society, 2013, p. 14-22Conference paper (Refereed)
    Abstract [en]

    Energy consumption is becoming the Achilles' heel of the mobile user quality of experience partly due to undisciplined use of the cellular (3G) transmissions by applications. The operator infrastructure is typically configured for peak performance, whereas during periods of underutilisation the handsets pay the price by staying in high energy states even if each application only uses a fraction of the maximum available bandwidth. In this paper we promote a bi-radio scenario where instead of independently using own cellular connections, several users share a single cellular link offered by one member of a coalition (a rotating aggregator). We present Watts2Share, an architecture for energy-aware traffic consolidation whereby group members' data flows transmitted through a second radio (e.g., WiFi) are aggregated by the aggregator and retransmitted through the cellular link. Through careful and repeatable studies we demonstrate that this scheme saves up to 68% of the total transmission energy in handsets compared to a pure 3G scenario. The studies are based on a wide range of real traffic traces and real cellular operator settings, and further illustrate that this scheme reduces the overall energy by reducing the signalling overhead, as well as extending the lifetime of all handsets.

  • 637.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sharing the Cost of Lunch: Energy Apportionment Policies2015In: Proceedings of the 11th ACM Symposium on QoS and Security for Wireless and Mobile Networks, ACM Digital Library, 2015, p. 91-97Conference paper (Refereed)
    Abstract [en]

    Energy consumption has become a hot topic in computer and communication technologies pinpointing the need to carefully analyse system efficiency. The energy consumption of a system is determined by the usage patterns of system components and complex interactions between the coexisting entities and resources. Providing transparency of a system’s consumption by breaking down the total consumption is vital to evaluate and provide energy-efficient design and operation.

    In this paper we survey the apportionment problem in different fields such as computer systems, wireless sensor networks, mobile devices and energy-efficient buildings. The challenge lies in how to attribute a share of the total energy consumption to the responsible entities (e.g., applications, processes or users of the system). Our analysis identifies that energy apportionment is a common problem in different fields and reviews five previously applied energy apportionment policies. Also, the work identifies relevant further research.

  • 638.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Prihodko, Mihails
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    EnergyBox: Disclosing the wireless transmission energy cost for mobile devices2014In: Sustainable Computing: Informatics and Systems, ISSN 2210-5379, Vol. 4, no 2, p. 118-135Article in journal (Refereed)
    Abstract [en]

    While evolving mobile technologies bring millions of users closer to the vision of information anywhere-anytime, device battery depletions still hamper the quality of experience to a great extent. The energy consumption of data transmission is highly dependent on the traffic pattern, and we argue that designing energy efficient data transmissions starts by energy awareness. Our work proposes EnergyBox, a parametrised tool that facilitates accurate and repeatable energy consumption studies for 3G and WiFi transmissions at the user end using real traffic data.

    The tool takes as input the parameters of a network operator and the power draw for a given mobile device in the 3G and WiFi transmission states. It outputs an estimate of the consumed energy for a given packet trace, either synthetic or captured in a device using real applications. Using nine different applications with different data patterns the versatility and accuracy of the tool was evaluated. The evaluation was carried out for a modern and popular smartphone in the WiFi setting, a specific mobile broadband module for the 3G setting, and within the operating environment of a major mobile operator in Sweden. A comparison with real power traces indicates that EnergyBox is a valuable tool for repeatable and convenient studies. It exhibits an accuracy of 94–99% for 3G, and 95–99% for WiFi given the studied applications’ traces.

    Next the tool was deployed in a use case where a location sharing application was ran on top of two alternative application layer protocols (HTTP and MQTT) and with two different data exchange formats (JSON and Base64). The illustrative use case helped to identify the appropriateness of the pull and push strategies in sharing location data, and the benefit of EnergyBox in characterising where the breaking point lies for preferring one or the other protocol, under which network load, or exchange data format.

  • 639.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Prihodko, Mihails
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Mobile Location Sharing: An Energy Consumption Study2013In: e-Energy '13 Proceedings of the 4th International Conference on Future Energy Systems: Where Energy, Computing and Communication Meet, New York, NY, USA: ACM Press, 2013, p. 289-290Conference paper (Refereed)
    Abstract [en]

    The use of a mobile device's battery for frequent transmissions of position data in a location sharing application can be more expensive than the location retrieval itself. This is in part due to energy-agnostic application development and in part dependent on choice of protocols. This paper studies the lightweight Message Queuing Telemetry Transport protocol (MQTT) as an application layer protocol on top of the third generation cellular communication. The energy efficiency and amount of data generated by the publish/subscribe MQTT protocol is experimentally compared against the Hypertext Transfer Protocol (HTTP), which is currently used in typical location sharing applications.

    The evaluation results indicate that MQTT is a good candidate as a protocol for location sharing. At comparable bandwidth and energy expenses MQTT offers better quality of user experience, since the subscribers are notified at once when the location of some interesting client has changed. Our measurements show that MQTT is more energy-efficient than HTTP in the idle state and when the number of other users with whom the client shares location is low. When the number of users increases beyond 3, HTTP becomes the preferred option in terms of energy efficiency at the cost of a higher notification delay.

  • 640.
    Vergara Alonso, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Sanjuan, Joseba
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Kernel Level Energy-Efficient 3G Background Traffic Shaper for Android Smartphones2013Conference paper (Refereed)
    Abstract [en]

    Reducing the energy consumption of wireless devices is paramount to a wide spread adoption of mobile applications. Cellular communication imposes high energy consumption on the mobile devices due to the radio resource allocation, which differs from other networks such as WiFi. Most applications are unaware of the energy consumption characteristics of third generation cellular communication (3G). This makes the background small data transfers of undisciplined applications an energy burden due to inefficient utilisation of resources.

    While several approaches exist to reduce the energy consumption of this best-effort background traffic by means of traffic shaping, we find that they are mostly evaluated with simulations and the actual energy overhead for the traffic shaper itself has not been studied. In order to cover this gap, our work realises an existing energy saving algorithm as a Kernel Level Shaper (KLS) within the Android platform, and measures its energy footprint. The total energy savings of our implementation range from 8% to 58% for emulated real background traffic, that is categorised as best-effort traffic. We further show the implications of running the KLS during live operation of applications as an exploratory study.

  • 641.
    Vergara, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Energy-aware Cross-layer Burst Buffering for Wireless Communication2012In: e-Energy '12 Proceedings of the 3rd International Conference on Future Energy Systems: Where Energy, Computing and Communication Meet, ACM , 2012Conference paper (Other academic)
    Abstract [en]

    The massive explosion of mobile applications with the ensuing data exchange over the cellular infrastructure is not only a blessing to the mobile user but also has a price in terms of regular discharging of the device battery. A big contributor to this energy consumption is the power hungry wireless network interface. We leverage a measurement kit to perform accurate physical energy consumption measurements in a third generation (3G) telecommunication modem thus isolating the energy footprint of data transfers as opposed to other mobile phone-based measurement studies. Using the measurement kit we show how the statically configured network parameters, i.e., channel switch timers, and buffer thresholds, in addition to the transfer data pattern and the radio coverage, impact the communication energy footprint. We then demonstrate that being aware of static network parameters creates room for energy savings. This is done by devising a set of algorithms that (a) infer the network parameters efficiently, and (b) use the parameters in a new packet scheduler in the device. The combined regime is shown to transfer background uplink data, from real world traces of Facebook and Skype, with significant energy saving compared to the state-of-the-art.

  • 642.
    Vergara, Ekhiotz Jon
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fairness and Incentive Considerations in Energy Apportionment Policies2016In: ACM Transactions on Modeling and Performance Evaluation of Computing Systems, ISSN 2376-3639, Vol. 2, no 1Article in journal (Refereed)
    Abstract [en]

    The energy consumption of a system is determined by the system component usage patterns and interactions between the coexisting entities and resources. Energy accounting plays an essential role in revealing the contribution of each entity to the total consumption and for energy management. Unfortunately, energy accounting inherits the apportionment problem of accounting in general, which does not have a general single best solution. In this article, we leverage cooperative game theory, which is commonly used in cost allocation problems to study the energy apportionment problem, that is, the problem of prescribing the actual energy consumption of a system to the consuming entities (e.g., applications, processes, or users of the system).

    We identify five relevant fairness properties for energy apportionment and present a detailed categorisation and analysis of eight previously proposed energy apportionment policies from different fields in computer and communication systems. In addition, we propose two novel energy apportionment policies based on cooperative game theory that provide strong fairness notion and a rich incentive structure. Our comparative analysis in terms of the identified five fairness properties as well as information requirement and computational complexity shows that there is a tradeoff between fairness and the other evaluation criteria. We provide guidelines to select an energy apportionment policy depending on the purpose of the apportionment and the characteristics of the system.

  • 643.
    Viel, Brieuc
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Asplund, Mikael
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Why is fingerprint-based indoor localization still so hard?2014In: IEEE International Conference on Pervasive Computing and Communications Workshops (PERCOM Workshops), IEEE Computer Society, 2014, p. 443-448Conference paper (Refereed)
    Abstract [en]

    Wireless indoor localization systems and especially signal strength fingerprinting techniques have been the subject of significant research efforts in the last decades. However, most of the proposed solutions require a costly site-survey to build the radio map which can be used to match radio signatures with specific locations. We investigate a novel indoor localization system that addresses the data collection problem by progressively and semi-autonomously creating a radio-map with limited interaction cost. Moreover, we investigate how spatiotemporal and hardware properties-based variations can affect the RSSI values collected and significantly influence the resulting localization. We show the impact of these fluctuations on our system and discuss possible mitigations.

  • 644.
    Vincelette, Erik
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Forecast: Beräkningar på affärs data2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    RemoteX Technologies AB är ett mjukvaruföretag i Stockholm. De utvecklar branschlösningar för ärendehantering och administration inom och mellan företrädandevis serviceföretag, ex. fastighetsförvaltning, VVS och byggbolag. Deras produkt heter RemoteX Applications och har sedan ett par månader tillbaka en möjlighet att kunna generera jobb utifrån fördefinierade scheman, vilket säkerställer att man kan hantera sina åtaganden i form av ronderingar och planerat underhåll. Deras kunder saknar dock en möjlighet att se vad den samlade mängden scheman kommer att generera framåt i tiden.Detta examensarbete syftar till att bygga en simulator för att beräkna hur mycket jobb som genereras och visa upp detta i ett webbgränssnitt. Simulatorn kommer skrivas i C# och hämta data från bakomliggande databas med LINQ to SQL och fokus ligger på att göra simuleringen så effektiv som möjligt med de tekniker som används. Webbgränssnittet skrivs i HTML5 och JavaScript och använder sig av färdiga JavaScript bibliotek för att visualisera prognosen som skapas av simulatorn.En slutpunkt har byggts i RemoteX REST API som tillhandahåller prognoser 6 månader framåt i tiden. Det går att ge parametrar till slutpunkten för att filtrera sin prognos ytterligare. En front-end som är en ny vy inom planning modulen har skapats och denna kommunicerar med slutpunkten. Denna front-end visualiserar prognosen i form av en agenda.

  • 645.
    Vogel, Harald
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Enhetstestning inom PL/SQL - en fallstudie2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Att ha ett väl fungerande automatiskt testsystem är allt viktigare inom mjukvaruutveckling. Tyvärr är det fortfarande vanligt med företag som framförallt förlitar sig på manuell testning i olika former vilket för med sig en rad problem. Extra svårt blir det för de ovanligare programmeringsspråken, som inte har samma historia av automatisk testning som andra språk. Genom att implementera enhetstestning på liten skala på ett riktigt system i PL/SQL och mäta resultaten, kan flera slutsatser dras om enhetstestnings duglighet. Enhetstestning tar betydligt kortare tid att exekvera än motsvarande tester manuellt och kan lätt återupprepas. De kan även testa kombinationer som är omöjliga eller mycket svåra att utföra manuellt, och de minskar tiden det tar att rätta buggar. Att skriva enhetstester tar initialt mycket tid och kräver en viss kunskap. Det kan även dröja innan enhetstester börjar ge resultat och de behöver underhållas allt eftersom att koden ändras. 

  • 646.
    Walander, Tomas
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Larsson, David
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Critical success factors in Agile software development projects2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 647.
    Wang, Q.
    et al.
    Embedded Intelligent Solutions (EIS) By Semcon AB, Linköping, Sweden.
    Wallin, A.
    Embedded Intelligent Solutions (EIS) By Semcon AB, Linköping, Sweden.
    Izosimov, Viacheslav
    Embedded Intelligent Solutions (EIS) By Semcon AB, Linköping, Sweden.
    Ingelsson, Urban
    Embedded Intelligent Solutions (EIS) By Semcon AB, Linköping, Sweden.
    Peng, Zebo
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Test tool qualification through fault injection2012In: Test Symposium (ETS 2012), IEEE , 2012Conference paper (Other academic)
    Abstract [en]

    According to ISO 26262, a recent automotive functional safety standard, verification tools shall undergo qualification, e.g. to ensure that they do not fail to detect faults that can lead to violation of functional safety requirements. We present a semi-automatic qualification method involving a monitor and fault injection that reduce cost in the qualification process. We experiment on a verification tool implemented in LabVIEW.

  • 648.
    Wen, Liang
    et al.
    University of Elect Science and Technology China, Peoples R China.
    Jiang, Wei
    University of Elect Science and Technology China, Peoples R China.
    Jiang, Ke
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Zhang, Xia
    University of Texas Dallas, TX USA.
    Pan, Xiong
    University of Elect Science and Technology China, Peoples R China.
    Zhou, Keran
    University of Elect Science and Technology China, Peoples R China.
    Detecting Fault Injection Attacks on Embedded Real-Time Applications: A System-Level Perspective2015In: 2015 IEEE 17TH INTERNATIONAL CONFERENCE ON HIGH PERFORMANCE COMPUTING AND COMMUNICATIONS, 2015 IEEE 7TH INTERNATIONAL SYMPOSIUM ON CYBERSPACE SAFETY AND SECURITY, AND 2015 IEEE 12TH INTERNATIONAL CONFERENCE ON EMBEDDED SOFTWARE AND SYSTEMS (ICESS), IEEE , 2015, p. 700-705Conference paper (Refereed)
    Abstract [en]

    This paper presents an approach to the synthesis of secure real-time applications mapped on distributed embedded systems, which focuses on preventing fault injection attacks. We utilize symmetric cryptographic service to protect confidentiality, and deploy fault detection within confidential algorithm to resist fault injection attacks. Several fault detection schemes are identified, and their fault coverage rates and time overheads are derived and measured, respectively. Our synthesis approach makes efforts to determine the best fault detection schemes for the encryption/decryption of messages, such that the overall security strength of resisting fault injection attack is minimized, and the deadline constraint of the real-time applications is guaranteed. Since addressing the problem is still a NP-hard problem, we propose an efficient algorithm based on Fruit fly Optimization Algorithm (FOA), which can achieve better results by lower time overheads, compared with simulated annealing algorithm. Extensive experiments demonstrate the superiority of our approach.

  • 649.
    Wennberg, Per
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Danielson, Viktor
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Evaluation of a Testing Process to Plan and Implement an Improved Test System: A Case Study, Evaluation and Implementation in Lab-VIEW/TestStand2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to ensure the quality of a product, the provider of the product must performcomplete testing of the product. This fact increases the demands on the test systems usedto conduct the testing, the system needs to be reliable.When developing new software for a company, sometimes a requirements specificationcreated at the beginning of the project is not enough. Details of the desired implementationmay get lost when working with a general requirements specification.This thesis presents a case study of how a certain company work with their test systems.The aim of the case study was to find where the largest points of improvements could bemade in a new test system, which was to be implemented during this thesis work. Theimplementation of this new system was done in LabVIEW in conjunction with TestStandand this process is covered in this thesis.The performed case study revealed that the employees at the company found robustnessand usability to be the key factors in a new test system. During and after the implementationof the new system, it was evaluated regarding these two metrics, this process isalso covered in this thesis.

  • 650.
    Wiberg, Fabian
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Patterns for Injection of Mock Objects in a Modeling Environment2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Capsules are modeling language elements which are sometimes used to develop real-time software. One way to test such capsule elements without relying on dependencies to other units is to use mock objects. The aim of the study was to look at existing object-oriented design patterns and investigate how they could be used for capsules, in order to perform mock testing. The focus was to find solutions that were usable from the programmers’ point of view, meaning that they should promote high user effectiveness, efficiency and satisfaction when implementing them. It was also important that program efficiency wasn’t affected negatively. 5 design- or refactoring patterns were adapted for capsules: Constructor Injection, Setter Injection, Parameterize Method, Factory Method and Abstract Factory. Those patterns were evaluated by 5 programmers in a usability test, where Incarnate Injection (an adaptation of Constructor Injection) and Abstract Factory were considered most usable. Incarnate Injection seemed to be easier to implement and promoted high user efficiency, while Abstract Factory was considered more flexible. The performance tests indicated that Abstract Factory compromises program efficiency when the factory product is resource-heavy and is required frequently by dependent capsules. The study showed that it is possible to adapt design patterns to capsules by looking at conceptual similarities between capsules and classes. However, there are cases when this adaptation is impossible. Furthermore, even when adaptation is possible, it was apparent that different patterns adapt differently well to capsules.

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