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  • 601.
    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].

  • 602.
    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.

  • 603.
    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.

  • 604.
    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.

  • 605.
    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.

  • 606.
    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.

  • 607.
    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. 

  • 608.
    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.

  • 609.
    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. 

  • 610.
    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.

  • 611.
    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.

  • 612.
    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. 

  • 613.
    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. 

  • 614.
    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%.

  • 615.
    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.

  • 616.
    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.

  • 617.
    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.

  • 618.
    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.

  • 619.
    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.

  • 620.
    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.

  • 621.
    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.

  • 622.
    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.

  • 623.
    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.

  • 624.
    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.

  • 625.
    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.

  • 626.
    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. 

  • 627.
    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
  • 628.
    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.

  • 629.
    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.

  • 630.
    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.

  • 631.
    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.

  • 632.
    Wilander, John
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Contributions to Specification, Implementation, and Execution of Secure Software2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis contributes to three research areas in software security, namely security requirements and intrusion prevention via static analysis and runtime detection.

    We have investigated current practice in security requirements by doing a field study of eleven requirement specifications on IT systems. The conclusion is that security requirements are poorly specified due to three things:  inconsistency in the selection of requirements, inconsistency in level of detail, and almost no requirements on standard security solutions. A follow-up interview study addressed the reasons for the inconsistencies and the impact of poor security requirements. It shows that the projects had relied heavily on in-house security competence and that mature producers of software compensate for poor requirements in general but not in the case of security and privacy requirements specific to the customer domain.

    Further, we have investigated the effectiveness of five publicly available static analysis tools for security. The test results show high rates of false positives for the tools building on lexical analysis and low rates of true positives for the tools building on syntactical and semantical analysis. As a first step toward a more effective and generic solution we propose decorated dependence graphs as a way of modeling and pattern matching security properties of code. The models can be used to characterize both good and bad programming practice as well as visually explain code properties to programmers. We have implemented a prototype tool that demonstrates how such models can be used to detect integer input validation flaws.

    Finally, we investigated the effectiveness of publicly available tools for runtime prevention of buffer overflow attacks. Our initial comparison showed that the best tool as of 2003 was effective against only 50 % of the attacks and there were six attack forms which none of the tools could handle. A follow-up study includes the release of a buffer overflow testbed which covers 850 attack forms. Our evaluation results show that the most popular, publicly available countermeasures cannot prevent all of these buffer overflow attack forms.

  • 633.
    Wrona, Michal
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Local-to-Global Consistency Implies Tractability of Abduction2014Conference paper (Refereed)
  • 634.
    Wrona, Michal
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Syntactically Characterizing Local-to-Global Consistency in ORD-Horn2012Conference paper (Other academic)
    Abstract [en]

    Establishing local consistency is one of the most frequently used algorithmic techniques in constraint satisfaction in general and in spatial and temporal reasoning in particular. A collection of constraints is globally consistent if it is completely explicit, that is, every partial solution may be extended to a full solution by greedily assigning values to variables one at a time. We will say that a structure B has local-to-global consistency if establishing local-consistency yields a globally consistent instance of CSP(B) .

    This paper studies local-to-global consistency for ORD-Horn languages, that is, structures definable over the ordered rationals (ℚ; < ) within the formalism of ORD-Horn clauses. This formalism has attracted a lot of attention and is of crucial importance to spatial and temporal reasoning. We provide a syntactic characterization (in terms of first-order definability) of all ORD-Horn languages enjoying local-to-global consistency.

  • 635.
    Wrona, Michal
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Tractability Frontier for Dually-Closed Ord-Horn Quantified Constraint Satisfaction Problems2014In: MATHEMATICAL FOUNDATIONS OF COMPUTER SCIENCE 2014, PT I, Springer Berlin/Heidelberg, 2014, Vol. 8634, p. 535-546Conference paper (Refereed)
    Abstract [en]

    A temporal constraint language is a relational structure with a first-order definition in the rational numbers with the order. We study here the complexity of the Quantified Constraint Satisfaction Problem (QCSP) for Ord-Horn languages: probably the most widely studied family of all temporal constraint languages.

    We restrict ourselves to a natural subclass that we call dually-closed Ord-Horn languages. The main result of the paper states that the QCSP for a dually-closed Ord-Horn language is either in P or it is coNP-hard.

  • 636.
    Xu, Yang
    et al.
    Lund University, Sweden.
    Årzen, Karl-Erik
    Lund University, Sweden.
    Cervin, Anton
    Lund University, Sweden.
    Bini, Enrico
    Scuola Superiore Sant’Anna, Italy.
    Tanasa, Bogdan
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Exploiting Job Response-Time Information in the Co-Design of Real-Time Control Systems2015In: 2015 IEEE 21ST INTERNATIONAL CONFERENCE ON EMBEDDED AND REAL-TIME COMPUTING SYSTEMS AND APPLICATIONS, Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 247-256Conference paper (Refereed)
    Abstract [en]

    We consider a real-time system of multiple tasks, each task having a plant to control. The overall quadratic control cost is to be optimized. We exploit the periodicity of the task response time, which corresponds to a periodic delay pattern in the feedback control loop. Perturbed periods are used as a tool to find a finite hyper period. We present an analytical procedure to design a periodic linear-quadratic-Gaussian (LQG) controller for tasks with fixed execution times as well as a numerical solution to the periodic -- stochastic LQG problem for tasks with variable execution times. The controllers are evaluated using simulations in real-time scheduling and control co-design examples.

  • 637.
    Yang, Ming-Jie
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Design and Implementation of a Compiler for an XML-based Hardware Description Language to Support Energy Optimization2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    GPU-based heterogeneous system architectures are popular as they combine the advantages of CPU with the benefits of GPU. Development of high-performance and power-efficient software for heterogeneous system architecture needs to take both hardware and software specifications into consideration, which leads the software development process to be more complicated. To simplify the software development process, Architecture Description Languages (ADLs) came out. By modeling the target architecture components into structural formats, programmers can adapt their software to the platforms which they used.

    XPDL is a modular and extensible XML-based platform description language which is mainly designed to support optimization.The purposes of this thesis are to design the query API (Application Programming Interface) and develop a compiler which translates the XPDL descriptors to libraries that implement the API to support programmers for the development of adaptive high-performance and energy-optimized software.

    In this thesis, we design and develop a compiler to generate the API according to the XPDL descriptors.The main workflow of the designed compiler is following: first, the toolchain validates the XPDL descriptors against XSDs. Second, it parses the descriptors into DOM trees and transforms them into XPDL model trees. Next, the compiler links all XPDL model trees together, which results in the intermediate representation (IR). Then, any unspecified node values which means the unknown attributes, are handled by microbenchmark generator and executor. In the end, the code generator generates the libraries which expose the API according to the information in the IR. Finally, a few example codes are discussed to show how the API can be used to develop performance adaptive applications on heterogeneous systems.

  • 638.
    Yildiz, George
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Wallström, Fredrik
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Evaluation of Couchbase As a Tool to Solve a Scalability Problem with Shared Geographical Objects2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Sharing a large amount of data between many mobile devices can lead to scalability problems. One of these scalability problems is that the data becomes too large to store on mobile devices and that many updates are sent to each device. In this thesis, Couchbase is evaluated as a tool to solve this problem where the data has a geographical position. The scalability problem is solved by partitioning the data with the help of Couchbase channels and Google’s tile-based mapping system. Synchronising and storing only data of interest for each user has been in focus. The result showed that it was effective to use a Couchbase solution together with Google’s tile-based mapping system to reduce the amount of data that was required to be stored for each user. It was shown to be more effective to store objects encoded as base64 data instead of their binary data representation for the data set used in this study. The reason for this is because Couchbase stores Binary Large Objects (BLOBs) as separate files and the BLOBs in the data set had much smaller file size than what the disk sector size was. A test to find how the synchronisation time was affected by the number of channels was conducted. It showed that the synchronisation time increased linearly with an increasing number of channels when the objects were stored in separate files. When the objects were encoded as base64 data, the number of channels used had a minor effect on the synchronisation time. The conclusion is that the approach presented in this study has been effective. However, the results are data dependent and therefore it is recommended to rerun similar tests in order to decide the number of channels to use when partitioning the data.

  • 639.
    Zadegan, Farrokh Ghani
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Carlsson, Gunnar
    Ericsson, Linköping, Sweden.
    Larsson, Erik
    Lund University, Sweden.
    Scenario-Based Network Design for P16872013In: SSoCC'13, 2013Conference paper (Other academic)
    Abstract [en]

    To improve testability of integrated circuits against manufacturing defects, and to better handle the complexity of modern designs during debugging and characterization, it is common to embed testing, debugging, configuration, and monitoring features (called on-chip instruments) within the chip. IEEE P1687 proposes a flexible network for accessing and operating such on-chip instruments from outside the chip, and facilitates reusing instrument access procedures in different usage scenarios throughout the chip's life-cycle-spanning from chip prototyping to in-field test. Efficient access (in terms of time) to on-chip instruments requires careful design of the instrument access network. However, it is shown that a network optimized for one usage scenario, is not necessarily efficient in other scenarios. To address the problem of designing a network which is efficient in terms of instrument access time under multiple scenarios, in this work, we compare a number of network design approaches provided by P1687, in terms of instrument access time and hardware overhead.

  • 640.
    Zadegan, Farrokh Ghani
    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.
    Ingelsson, Urban
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    Asani, Golnaz
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    Carlsson, Gunnar
    Ericsson, Linköping, Sweden.
    Larsson, Erik
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    Test Scheduling in an IEEE P1687 Environment with Resource and Power Constraints2011In: Proceedings of the Asian Test Symposium, IEEE , 2011, p. 525-531Conference paper (Refereed)
    Abstract [en]

    In contrast to IEEE 1149.1, IEEE P1687 allows, through segment insertion bits, flexible scan paths for accessing on-chip instruments, such as test, debug, monitoring, measurement and configuration features. Flexible access to embedded instruments allows test time reduction, which is important at production test. However, the test access scheme should be carefully selected such that resource constraints are not violated and power constraints are met. For IEEE P1687, we detail in this paper session-based and session-less test scheduling, and propose resource and power-aware test scheduling algorithms for the detailed scheduling types. Results using the implementation of our algorithms shows on ITC’02-based benchmarks significant test time reductions when compared to non-optimized test schedules.

  • 641.
    Zadegan, Farrokh Ghani
    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.
    Ingelsson, Urban
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    Carlsson, Gunnar
    Ericsson, Linköping, Sweden.
    Larsson, Erik
    Linköping University, Department of Computer and Information Science, ESLAB - Embedded Systems Laboratory.
    Automated Design for IEEE P16872011In: The 11th Swedish System-on-Chip Conference, Varberg, Sweden, May 2-3, 2011., 2011Conference paper (Other academic)
  • 642.
    Zeng, Haibo
    et al.
    Department of Electrical and Computer Engineering, Virginia Tech, Blacksburg, USA.
    Joshi, Prachi
    Department of Electrical and Computer Engineering, Virginia Tech, USA.
    Thiele, Daniel
    Elektrobit Automotive GmbH, Germany.
    Diemer, Jonas
    Symtavision, Braunschweig, Germany.
    Axer, Philip
    NXP Semiconductors, Hamburg, Germany.
    Ernst, Rolf
    Institut für Datentechnik und Kommunikationsnetze, Technische Universität Braunschweig, Germany.
    Eles, Petru
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Networked Real-Time Embedded Systems2017In: Handbook of Hardware/Software Codesign / [ed] Soonhoi Ha and Jürgen Teich, Dordrecht: Springer, 2017, p. 753-792Chapter in book (Refereed)
    Abstract [en]

    This chapter gives an overview on various real-time communication protocols, from the Controller Area Network (CAN) that was standardized over twenty years ago but is still popular, to the FlexRay protocol that provides strong predictability and fault tolerance, to the more recent Ethernet-based networks. The design of these protocols including their messaging mechanisms was driven by diversified requirements on bandwidth, real-time predictability, reliability, cost, etc. The chapter provides three examples of real-time communication protocols: CAN as an example of event-triggered communication, FlexRay as a heterogeneous protocol supporting both time-triggered and event-triggered communications, and different incarnations of Ethernet that provide desired temporal guarantees.

  • 643.
    Zhan, Jinyu
    et al.
    Univ Elect Sci and Technol China, Peoples R China.
    Zhang, Xia
    Univ Texas Dallas, TX 75083 USA.
    Jiang, Wei
    Univ Elect Sci and Technol China, Peoples R China.
    Ma, Yue
    Univ Notre Dame, IN 46556 USA.
    Jiang, Ke
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Energy optimization of security-sensitive mixed-criticality applications for distributed real-time systems2018In: Journal of Parallel and Distributed Computing, ISSN 0743-7315, E-ISSN 1096-0848, Vol. 117, p. 115-126Article in journal (Refereed)
    Abstract [en]

    Existing studies on mixed-criticality systems are usually safety-oriented, which seriously ignore the security and energy related requirements. In this paper we are interested in the design of security-sensitive mixed-criticality real-time systems. We first establish the system model to capture security-critical applications in mixed-criticality systems. Higher security-criticality protection always results in significant time and energy overhead in mixed-criticality systems. Thus, this paper proposes a system-level design framework for energy optimization of security-sensitive mixed-criticality system with hard real-time constraints. Since the time complexity of finding optimal solutions grows exponentially as problem size grows, a GA (Genetic Algorithm) based on efficient heuristic algorithm is devised to address the system-level optimization problem. Extensive experiments and a real-life case study have been conducted to show the efficiency of the proposed technique, which can obtain balanced minimal energy consumption while satisfying strict security and timing constraints. The proposed approach can save up to 28.9% energy consumption compared with other three candidates. (C) 2018 Elsevier Inc. All rights reserved.

  • 644.
    Zhang, Xia
    et al.
    University of Electronic Science and Technology, China.
    Zhang, Jinyu
    University of Electronic Science and Technology, China.
    Jiang, Wei
    University of Electronic Science and Technology, China.
    Ma, Yue
    University of Electronic Science and Technology, China.
    Jiang, Ke
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Design Optimization of Security-Sensitive Mixed-Criticality Real-Time Embedded Systems2013Conference paper (Refereed)
    Abstract [en]

    In this paper we are interested in securitysensitive mixed-criticality real-time systems. Existing researches on mixed-criticality systems usually are safety-oriented, which seriously ignore the security requirements. We firstly establish the system model to capture security-critical applications in mixed-criticality systems. Higher security-criticality protection always results in significant time and energy overhead in mixedcriticality systems. Thus, this paper proposes a system-level design framework for energy optimization of security-sensitive mixed-criticality system. Since the time complexity of finding optimal solutions grows exponentially as problem size grows, a GA based efficient heuristic algorithm is devised to address the system-level optimization problem. Extensive experiments demonstrate the efficiency of the proposed technique, which can obtain balanced minimal energy consumption while satisfying strict security and timing constraints.

  • 645.
    Zhang, Ying
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Li, Huawei
    Institute of Computing Technology, Chinese Academy of Sciences, Beijing, China.
    Li, Xiaowei
    Institute of Computing Technology, Chinese Academy of Sciences, Beijing, China.
    Automatic Test Program Generation Using Executing Trace Based Constraint Extraction for Embedded Processors2013In: IEEE Transactions on Very Large Scale Integration (vlsi) Systems, ISSN 1063-8210, E-ISSN 1557-9999, Vol. 21, no 7, p. 1220-1233Article in journal (Refereed)
    Abstract [en]

    Software-based self-testing (SBST) has been a promising method for processor testing, but the complexity of the state-of-art processors still poses great challenges for SBST. This paper utilizes the executing trace collected during executing training programs on the processor under test to simplify mappings and functional constraint extraction for ports of inner components, which facilitate structural test generation with constraints at gate level, and automatic test instruction generation (ATIG) even for hidden control logic (HCL). In addition, for sequential HCL, we present a test routine generation technique on the basis of an extended finite state machine, so that structural patterns for combinational subcircuits in the sequential HCL can be mapped into the test routines to form a test program. Experimental results demonstrate that the proposed ATIG method can achieve good structural fault coverage with compact test programs on modern processors.

  • 646.
    Zhang, Ying
    et al.
    School of Software Engineering, Tongji University, China.
    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.
    Jiang, Jianhui
    School of Software Engineering, Tongji University, China.
    Li, Huawei
    State Key Laboratory of Computer Architecture, Institute of Computing Technology, Chinese Academy of Sciences, China.
    Fujita, Masahiro
    VLSI Design and Education Center, University of Tokyo, Japan .
    Temperature-Aware Software-Based Self-Testing for Delay Faults2015In: Proc. Design, Automation and Test in Europe Conference (DATE’15), Grenoble, France, Mar. 9-13, 2015., 2015Conference paper (Refereed)
    Abstract [en]

    Delay defects under high temperature have been one of the most critical factors to affect the reliability of computer systems, and the current test methods don’t address this problem properly. In this paper, a temperature-aware software-based selftesting (SBST) technique is proposed to self-heat the processors within a high temperature range and effectively test delay faults under high temperature. First, it automatically generates highquality test programs through automatic test instruction generation (ATIG), and avoids over-testing caused by nonfunctional patterns. Second, it exploits two effective powerintensive program transformations to self-heat up the processors internally. Third, it applies a greedy algorithm to search the optimized schedule of the test templates in order to generate the test program while making sure that the temperature of the processor under test is within the specified range. Experimental results show that the generated program is successful to guarantee delay test within the given temperature range, and achieves high test performance with functional patterns.

  • 647.
    Zhang, Ying
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Rezine, Ahmed
    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.
    Automatic Test Program Generation for Out-of-Order Superscalar Processors2012In: 21st IEEE Asian Test Symposium (ATS12), Niigata, Japan, November 19-22, 2012., IEEE, 2012Conference paper (Refereed)
    Abstract [en]

    This paper presents a high-level automatic test instruction generation (HATIG) technical that allows, for the first time, to test the scheduling unit of an out-of-order super scalar processor. This technique leverages on existing bounded model checking tools in order to generate software-based self-testing programs from a global EFSM model of the processor under test. The experimental results have demonstrated the efficiency of the proposed technique.

  • 648.
    Ögren, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Wikblad, Ludwig
    Linköping University, Department of Computer and Information Science, Software and Systems.
    En testprocess för webbutvecklingsprojekt med små team2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Finding a suitable approach for testing in small development teams is a challenge. Many small companies view traditional test processes and test process improvement models as too resource intensive for their needs. Minimal Test Practice Framework (MTPF) is a framework for testing which purpose is to provide a minimalistic approach to test improvement. The goal of this study was to examine how MTPF can be adapted to a small development team without incurring a time cost that the team would experience as too high. The study was performed in the department Web \& Mobile of the company Exsitec. At the department teams of 2-6 people develop web applications to business customers. During the study a testprocess was developed in close cooperation with the developers of the department with the aim of adapting it as well as possible to the needs of the department. The study was performed as action research in three phases, according to the method Cooperative Method Development, in a project with two developers. During the first phase all developers in the department were interviewed to establish an understanding of the environment for the study. During the second phase a set of possible improvements was developed together with the developers. During the third phase some of these improvements were implemented and evaluated. By focusing on unit testing central business logic in the application the developed test process improved the developers confidence in the code quality without being perceived as too resource intensive.

  • 649.
    Öhberg, Tomas
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Auto-tuning Hybrid CPU-GPU Execution of Algorithmic Skeletons in SkePU2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The trend in computer architectures has for several years been heterogeneous systems consisting of a regular CPU and at least one additional, specialized processing unit, such as a GPU.The different characteristics of the processing units and the requirement of multiple tools and programming languages makes programming of such systems a challenging task. Although there exist tools for programming each processing unit, utilizing the full potential of a heterogeneous computer still requires specialized implementations involving multiple frameworks and hand-tuning of parameters.To fully exploit the performance of heterogeneous systems for a single computation, hybrid execution is needed, i.e. execution where the workload is distributed between multiple, heterogeneous processing units, working simultaneously on the computation.

    This thesis presents the implementation of a new hybrid execution backend in the algorithmic skeleton framework SkePU. The skeleton framework already gives programmers a user-friendly interface to algorithmic templates, executable on different hardware using OpenMP, CUDA and OpenCL. With this extension it is now also possible to divide the computational work of the skeletons between multiple processing units, such as between a CPU and a GPU. The results show an improvement in execution time with the hybrid execution implementation for all skeletons in SkePU. It is also shown that the new implementation results in a lower and more predictable execution time compared to a dynamic scheduling approach based on an earlier implementation of hybrid execution in SkePU.

  • 650.
    Öhlin, Petra
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Prioritizing Tests with Spotify’s Test & Build Data using History-based, Modification-based & Machine Learning Approaches2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis intends to determine the extent to which machine learning can be used to solve the regression test prioritization (RTP) problem. RTP is used to order tests with respect to probability of failure. This will optimize for a fast failure, which is desirable if a test suite takes a long time to run or uses a significant amount of computational resources. A common machine learning task is to predict probabilities; this makes RTP an interesting application of machine learning. A supervised learning method is investigated to train a model to predict probabilities of failure, given a test case and a code change. The features investigated are chosen based on previous research of history- based and modification-based RTP. The main motivation for looking at these research areas is that they resemble the data provided by Spotify. The result of the report shows that it is possible to improve how tests run with RTP using machine learning. Nevertheless, a much simpler history- based approach is the best performing approach. It is looking at the history of test results, the more failures recorded for the test case over time, the higher priority it gets. Less is sometimes more. 

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