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  • 1.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Daniel, Sundmark
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Eldh, S.
    Ericsson AB, Kista, Sweden.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Runtime Verification Tool for Detecting Concurrency Bugs in FreeRTOS Embedded Software2018In: Proceedings - 17th International Symposium on Parallel and Distributed Computing, ISPDC 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 172-179, article id 8452035Conference paper (Refereed)
    Abstract [en]

    This article presents a runtime verification tool for embedded software executing under the open source real-time operating system FreeRTOS. The tool detects and diagnoses concurrency bugs such as deadlock, starvation, and suspension based-locking. The tool finds concurrency bugs at runtime without debugging and tracing the source code. The tool uses the Tracealyzer tool for logging relevant events. Analysing the logs, our tool can detect the concurrency bugs by applying algorithms for diagnosing each concurrency bug type individually. In this paper, we present the implementation of the tool, as well as its functional architecture, together with illustration of its use. The tool can be used during program testing to gain interesting information about embedded software executions. We present initial results of running the tool on some classical bug examples running on an AVR 32-bit board SAM4S. 

  • 2.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Daniel, Sundmark
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Eldh, S.
    Ericsson AB, Stockholm, Sweden.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Concurrency bugs in open source software: a case study2017In: Journal of Internet Services and Applications, ISSN 1867-4828, Vol. 8, no 1, article id 4Article in journal (Refereed)
    Abstract [en]

    Concurrent programming puts demands on software debugging and testing, as concurrent software may exhibit problems not present in sequential software, e.g., deadlocks and race conditions. In aiming to increase efficiency and effectiveness of debugging and bug-fixing for concurrent software, a deep understanding of concurrency bugs, their frequency and fixing-times would be helpful. Similarly, to design effective tools and techniques for testing and debugging concurrent software, understanding the differences between non-concurrency and concurrency bugs in real-word software would be useful. This paper presents an empirical study focusing on understanding the differences and similarities between concurrency bugs and other bugs, as well as the differences among various concurrency bug types in terms of their severity and their fixing time, and reproducibility. Our basis is a comprehensive analysis of bug reports covering several generations of five open source software projects. The analysis involves a total of 11860 bug reports from the last decade, including 351 reports related to concurrency bugs. We found that concurrency bugs are different from other bugs in terms of their fixing time and severity while they are similar in terms of reproducibility. Our findings shed light on concurrency bugs and could thereby influence future design and development of concurrent software, their debugging and testing, as well as related tools.

  • 3.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Daniel, Sundmark
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Runtime Verification for Detecting Suspension Bugs in Multicore and Parallel Software2017In: Proceedings - 10th IEEE International Conference on Software Testing, Verification and Validation Workshops, ICSTW 2017, 2017, p. 77-80Conference paper (Refereed)
    Abstract [en]

    Multicore hardware development increases the popularity of parallel and multicore software, while testing and debugging the software become more difficult, frustrating and costly. Among all types of software bugs, concurrency bugs are both important and troublesome. This type of bugs is increasingly becoming an issue, particularly due to the growing prevalence of multicore hardware. Suspension-based-locking bug is one type of concurrency bugs. This position paper proposes a model based on runtime verification and reflection technique in the context of multicore and parallel software to monitor and detect suspension-based-locking bugs. The model is not only able to detect faults, but also diagnose and even repair them. The model is composed of four layers: Logging, Monitoring, Suspension Bug Diagnosis and Mitigation. The logging layer will observe the events and save them into a file system. The monitoring layer will detect the presents of bugs in the software. The suspension bug diagnosis will identify Suspension bugs by comparing the captured data with the suspension bug properties. Finally, the mitigation layer will reconfigure the software to mitigate the suspension bugs. A functional architecture of a runtime verification tool is also proposed in this paper. This architecture is based on the proposed model and is comprised of different modules. 

  • 4.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. 7809198067.
    Enoiu, Eduard Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Causevic, Adnan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Daniel, Sundmark
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering.
    A Runtime Verification based Concurrency Bug Detector for FreeRTOS Embedded SoftwareIn: Article in journal (Other academic)
  • 5.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sundmark, Daniel
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Eldh, Sigrid
    Ericsson AB, Kista, Sweden.
    Towards Classification of Concurrency Bugs Based on Observable Properties2015In: Proceedings - 1st International Workshop on Complex Faults and Failures in Large Software Systems, COUFLESS 2015, 2015, p. 41-47Conference paper (Refereed)
    Abstract [en]

    In software engineering, classification is a way to find an organized structure of knowledge about objects. Classification serves to investigate the relationship between the items to be classified, and can be used to identify the current gaps in the field. In many cases users are able to order and relate objects by fitting them in a category. This paper presents initial work on a taxonomy for classification of errors (bugs) related to concurrent execution of application level software threads. By classifying concurrency bugs based on their corresponding observable properties, this research aims to examine and structure the state of the art in this field, as well as to provide practitioner support for testing and debugging of concurrent software. We also show how the proposed classification, and the different classes of bugs, relates to the state of the art in the field by providing a mapping of the classification to a number of recently published papers in the software engineering field.

  • 6.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Inam, Rafia
    Ericsson AB, Kista, Sweden.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Survey on Testing for Cyber Physical System2015In: Testing Software and Systems: 27th IFIP WG 6.1 International Conference, ICTSS 2015, Sharjah and Dubai, United Arab Emirates, November 23-25, 2015, Proceedings, 2015, p. 194-207Conference paper (Refereed)
    Abstract [en]

    Cyber Physical Systems (CPS) bridge the cyber-world of computing and communications with the physical world and require development of secure and reliable software. It asserts a big challenge not only on testing and verifying the correctness of all physical and cyber components of such big systems, but also on integration of these components. This paper develops a categorization of multiple levels of testing required to test CPS and makes a comparison of these levels with the levels of software testing based on the V-model. It presents a detailed state-of-the-art survey on the testing approaches performed on the CPS. Further, it provides challenges in CPS testing.

  • 7.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Saadatmand, Mehrdad
    SICS Swedish ICT, Västerås, Sweden.
    Eldh, Sigrid
    Ericsson AB, Kista, Sweden.
    Sundmark, Daniel
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Model for Systematic Monitoring and Debugging of Starvation Bugs in Multicore Software2016In: 2016 ASE Workshop on Specification, Comprehension, Testing and Debugging of Concurrent Programs SCTDCP2016, 2016Conference paper (Refereed)
    Abstract [en]

    With the development of multicore hardware, concurrent, parallel and multicore software are becoming increasingly popular. Software companies are spending a huge amount of time and resources to nd and debug the bugs. Among all types of software bugs, concurrency bugs are also important and troublesome. This type of bugs is increasingly becoming an issue particularly due to the growing prevalence of multicore hardware. In this position paper, we propose a model for monitoring and debugging Starvation bugs as a type of concurrency bugs in multicore software. The model is composed into three phases: monitoring, detecting and debugging. The monitoring phase can support detecting phase by storing collected data from the system execution. The detecting phase can support debugging phase by comparing the stored data with starvation bug's properties, and the debugging phase can help in reproducing and removing the Starvation bug from multicore software. Our intention is that our model is the basis for developing tool(s) to enable solving Starvation bugs in software for multicore platforms.

  • 8.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sundmark, Daniel
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Eldh, Sigrid
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Ericsson AB, Kista, Sweden .
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Afza, Wasif
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    10 Years of research on debugging concurrent and multicore software: a systematic mapping study2017In: Software quality journal, ISSN 0963-9314, E-ISSN 1573-1367, Vol. 25, no 1, p. 49-82Article in journal (Refereed)
    Abstract [en]

    Debugging – the process of identifying, localizing and fixing bugs – is a key activity in software development. Due to issues such as non-determinism and difficulties of reproducing failures, debugging concurrent software is significantly more challenging than debugging sequential software. A number of methods, models and tools for debugging concurrent and multicore software have been proposed, but the body of work partially lacks a common terminology and a more recent view of the problems to solve. This suggests the need for a classification, and an up-to-date comprehensive overview of the area. 

    This paper presents the results of a systematic mapping study in the field of debugging of concurrent and multicore software in the last decade (2005– 2014). The study is guided by two objectives: (1) to summarize the recent publication trends and (2) to clarify current research gaps in the field.

    Through a multi-stage selection process, we identified 145 relevant papers. Based on these, we summarize the publication trend in the field by showing distribution of publications with respect to year , publication venues , representation of academia and industry , and active research institutes . We also identify research gaps in the field based on attributes such as types of concurrency bugs, types of debugging processes , types of research  and research contributions.

    The main observations from the study are that during the years 2005–2014: (1) there is no focal conference or venue to publish papers in this area, hence a large variety of conferences and journal venues (90) are used to publish relevant papers in this area; (2) in terms of publication contribution, academia was more active in this area than industry; (3) most publications in the field address the data race bug; (4) bug identification is the most common stage of debugging addressed by articles in the period; (5) there are six types of research approaches found, with solution proposals being the most common one; and (6) the published papers essentially focus on four different types of contributions, with ”methods” being the type most common one.

    We can further conclude that there is still quite a number of aspects that are not sufficiently covered in the field, most notably including (1) exploring correction  and fixing bugs  in terms of debugging process; (2) order violation, suspension  and starvation  in terms of concurrency bugs; (3) validation and evaluation research  in the matter of research type; (4) metric  in terms of research contribution. It is clear that the concurrent, parallel and multicore software community needs broader studies in debugging.This systematic mapping study can help direct such efforts.

  • 9.
    Abbaspour Asadollah, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sundmark, Daniel
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Eldh, Sigrid
    Ericsson AB, Kista, Sweden.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Paul Enoiu, Eduard
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Study on Concurrency Bugs in an Open Source Software2016In: IFIP Advances in Information and Communication Technology, vol. 472, 2016, Vol. 472, p. 16-31Conference paper (Refereed)
    Abstract [en]

    Concurrent programming puts demands on software debugging and testing, as concurrent software may exhibit problems not present in sequential software, e.g., deadlocks and race conditions. In aiming to increase efficiency and effectiveness of debugging and bug-fixing for concurrent software, a deep understanding of concurrency bugs, their frequency and fixingtimes would be helpful. Similarly, to design effective tools and techniques for testing and debugging concurrent software understanding the differences between non-concurrency and concurrency bugs in real-word software would be useful.

  • 10.
    Bakhshi Valojerdi, Zeinab
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Dependable Fog Computing: A Systematic Literature Review2019Conference paper (Refereed)
    Abstract [en]

    Fog computing has been recently introduced to bridge the gap between cloud resources and the network edge. Fog enables low latency and location awareness, which is considered instrumental for the realization of IoT, but also faces reliability and dependability issues due to node mobility and resource constraints. This paper focuses on the latter, and surveys the state of the art concerning dependability and fog computing, by means of a systematic literature review. Our findings show the growing interest in the topic but the relative immaturity of the technology, without any leading research group. Two problems have attracted special interest: guaranteeing reliable data storage/collection in systems with unreliable and untrusted nodes, and guaranteeing efficient task allocation in the presence of varying computing load. Redundancy-based techniques, both static and dynamic, dominate the architectures of such systems. Reliability, availability and QoS are the most important dependability requirements for fog, whereas aspects such as safety and security, and their important interplay, have not been investigated in depth.

  • 11.
    Bate, Iain
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering.
    Better, Faster, Cheaper, and Safer Too: Is This Really Possible?2012In: IEEE Symposium on Emerging Technologies and Factory Automation, ETFA, 2012, p. 6489706-Conference paper (Refereed)
    Abstract [en]

    Increased levels of automation together with increased complexity of automation systems brings increased responsibility on the system developers in terms of quality demands from the legal perspectives as well as company reputation. Component based development of software systems provides a viable and cost-effective alternative in this context provided one can address the quality and safety certification demands in an efficient manner. In this paper we present our vision, challenges and a brief outline of various research themes in which our team is engaged currently within two major projects.

  • 12.
    Eldh, Sigrid
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Brandt, Joachim
    Ericsson Ltd.
    Street, Mark
    Ericsson Ltd.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering.
    Towards Fully Automated Test Management for Large Complex Systems2010In: ICST 2010 - 3rd International Conference on Software Testing, Verification and Validation, Paris, 2010, p. 412-420Conference paper (Refereed)
    Abstract [en]

    Development of large and complex software intensive systems with continuous builds typically generates large volumes of information with complex patterns and relations. Systematic and automated approaches are needed for efficient handling of such large quantities of data in a comprehensible way. In this paper we present an approach and tool enabling autonomous behavior in an automated test management tool to gain efficiency in concurrent software development and test. By capturing the required quality criteria in the test specifications and automating the test execution, test management can potentially be performed to a great extent without manual intervention. This work contributes towards a more autonomous behavior within a distributed remote test strategy based on metrics for decision making in automated testing. These metrics optimize management of fault corrections and retest, giving consideration to the impact of the identified weaknesses, such as fault-prone areas in software.

  • 13.
    Eldh, Sigrid
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering.
    Analysis of Mistakes as a Method to Improve Test Case Design2011In: International Conference on Software Testing, Verification and Validation(ICST), Berlin, 2011, p. 70-79Conference paper (Refereed)
    Abstract [en]

    Test Design - how test specifications and test cases are created - inherently determines the success of testing. However, test design techniques are not always properly applied, leading to poor testing. We have developed an analysis method based on identifying mistakes made when designing the test cases. Using an extended test case template and an expert review, the method provides a systematic categorization of mistakes in the test design. The two main classes of identified mistakes are (1) lack of comprehension (of the employed test design technique, target of test etc.) and (2) incomplete test case construction (due to lack of detail, missing clean-up, ambiguities, etc.). The detailed categorization of mistakes provides a basis for improvement of the Test Case Design, resulting in better tests. In developing our method we have investigated over 700 test cases created by novice testers. In a comparison with industrial test cases we could confirm that many of our mistake categories remain relevant also in an industrial context. Our contribution is a new method to improve the effectiveness of test case construction through proper application of test design techniques, leading to an improved coverage without loss of efficiency.

  • 14.
    Eldh, Sigrid
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Punnekkat, Sasikumar
    Mälardalen University, Department of Computer Science and Electronics.
    Pettersson, Anders
    Mälardalen University, Department of Computer Science and Electronics.
    Sundmark, Daniel
    Mälardalen University, Department of Computer Science and Electronics.
    Framework for Comparing Efficiency, Effectiveness and Applicability of Software Testing Techniques2006In: Proceedings - Testing: Academic and Industrial Conference - Practice and Research Techniques, TAIC PART 2006, 2006, p. 159-170, article id 1691683Conference paper (Refereed)
    Abstract [en]

    Software testing is expensive for the industry, and always constrained by time and effort. Although there is a multitude of test techniques, there are currently no scientifically based guidelines for the selection of appropriate techniques of different domains and contexts. For large complex systems, some techniques are more efficient in finding failures than others and some are easier to apply than others are. From an industrial perspective, it is important to find the most effective and efficient test design technique that is possible to automate and apply. In this paper, we propose an experimental framework for comparison of test techniques with respect to efficiency, effectiveness and applicability. We also plan to evaluate ease of automation, which has not been addressed by previous studies. We highlight some of the problems of evaluating or comparingtest techniques in an objective manner. We describe our planned process for this multi-phase experimental study. This includes presentation of some of the important measurements to be collected with the dual goals of analyzing the properties of the test technique, as well as validating our experimental framework.

  • 15.
    Eldh, Sigrid
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Punnekkat, Sasikumar
    Hansson, Hans
    Experiments with Component Test to Improve Software QualityManuscript (preprint) (Other academic)
  • 16.
    Eldh, Sigrid
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Punnekkat, Sasikumar
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Experiments with Component Tests to Improve Software Quality2007Conference paper (Refereed)
    Abstract [en]

    In commercial systems, time to market pressure often result in short cuts in the design phase where component test is most vulnerable. It is hard to define how much testing is cost effective by the individual developers, and hard to judge when testing is enough. Verification activities constitute a major part of the product cost. Failures unearthed during later phases of product development escalate the cost substantially. To reduce cost in later stages of testing by reducing failures is important not only for Ericsson, but for any software producer. At Ericsson, we created a scheme, Software Quality Rank (SQR). SQR is a way to improve quality on components. SQR consists of five steps, where the first is where the actual "ranking" of components takes place. Then a selection of components is targeted for improvement in five levels. Most components are targeted for rank 3, which is the cost-efficient quality level. Rank 5 is the target for safety-critical code. The goal of SQR was to provide developers with a tool that prioritizes what to do before delivery to next system test phase. SQR defines a stepwise plan, which describes how much and what to test on component level for each rank. It gives the process for how to prioritize components; re-introduces reviews; requires usage of static analysis tools and defines what coverage to be achieved. The scheme has been used with great success at different design organizations within and outside Ericsson and we believe it supports industry in defining what cost-efficient component test in a time to market situation.

  • 17.
    Eldh, Sigrid
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Punnekkat, Sasikumar
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Jönsson, Peter
    Combitech., Ericsson AB.
    Component Testing is Not Enough - A Study of Software Faults in Telecom Middleware2007In: Lecture Notes in Computer Science, vol. 4581, Springer, 2007, p. 74-89Chapter in book (Refereed)
    Abstract [en]

    The interrelationship between software faults and failures is quite intricate and obtaining a meaningful characterization of it would definitely help the testing community in deciding on efficient and effective test strategies. Towards this objective, we have investigated and classified failures observed in a large complex telecommunication industry middleware system during 2003-2006. In this paper, we describe the process used in our study for tracking faults from failures along with the details of failure data. We present the distribution and frequency of the failures along with some interesting findings unravelled while analyzing the origins of these failures. Firstly, though "simple" faults happen, together they account for only less than 10%. The majority of faults come from either missing code or path, or superfluous code, which are all faults that manifest themselves for the first time at integration/system level; not at component level. These faults are more frequent in the early versions of the software, and could very well be attributed to the difficulties in comprehending and specifying the context (and adjacent code) and its dependencies well enough, in a large complex system with time to market pressures. This exposes the limitations of component testing in such complex systems and underlines the need for allocating more resources for higher level integration and system testing.

  • 18.
    Eldh, Sigrid
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Punnekkat, Sasikumar
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Jönsson, Peter
    Mälardalen University, Department of Computer Science and Electronics.
    Component Testing is not Enough - A Study of Software Faults in Telecom Middleware2007In: Lecture Notes in Computer Science, vol. 4581, 2007, p. 74-89Conference paper (Refereed)
    Abstract [en]

    The interrelationship between software faults and failures is quite intricate and obtaining a meaningful characterization of it would definitely help the testing community in deciding on efficient and effective test strategies. Towards this objective, we have investigated and classified failures observed in a large complex telecommunication industry middleware system during 2003- 2006. In this paper, we describe the process used in our study for tracking faults from failures along with the details of failure data. We present the distribution and frequency of the failures along with some interesting findings unravelled while analyzing the origins of these failures. Firstly, though "simple" faults happen, together they account for only less than 10%. The majority of faults come from either missing code or path, or superfluous code, which are all faults that manifest themselves for the first time at integration/system level; not at component level. These faults are more frequent in the early versions of the software, and could very well be attributed to the difficulties in comprehending and specifying the context (and adjacent code) and its dependencies well enough, in a large complex system with time to market pressures. This exposes the limitations of component testing in such complex systems and underlines the need for allocating more resources for higher level integration and system testing.

  • 19.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    ARTES - A network for Real-Time research and graduate Education in Sweden 1997-20062006Collection (editor) (Other academic)
    Abstract [en]

    This book summarizes the results of the Swedish national real-time systems research initiative ARTES and provides a few representative examples of the science and scientific results that have emerged from ARTES.

    ARTES was supported by the Swedish Foundation for Strategic Research (SSF), with a total of 95 MSEK between 1998 and 2006. ARTES has unified and given strength to the Swedish real-time and embedded systems research community, and contributed substantially to advancing Sweden's international position in this area. ARTES has had a catalytic and coordinating effect for a total research effort extending far beyond the funding provided by SSF. It has created important synergies between disciplines, ensured industrial relevance in research, and facilitated important academic and industrial networking for approximately 100 senior researchers and some 200 post-graduate students.

  • 20.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Message from the ICST 2018 General Chair2018In: 11th IEEE International Conference on Software Testing, Verification and Validation, ICST 2018, p. xii-xiiiArticle in journal (Refereed)
  • 21.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering.
    Towards Composable Safety (Invited talk)2012In: Lecture Notes in Computer Science, vol. 7612 / [ed] Frank Ortmeier, Peter Daniel, Springer, 2012Chapter in book (Other academic)
  • 22.
    Hansson, Hans
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Carlson, Jan
    Mälardalen University, School of Innovation, Design and Engineering.
    Isovic, Damir
    Mälardalen University, School of Innovation, Design and Engineering.
    Lundqvist, Kristina
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Ouimet, Martin
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering.
    Seceleanu, Cristina
    Mälardalen University, School of Innovation, Design and Engineering.
    Real-Time Systems2010Book (Other academic)
    Abstract [en]

    This is a textbook developed for use in the Master Programme Module E-M.6 "Real-Time Systems" as part of the Postgraduate Distance studies organized by Fraunhofer IESE and the Distance and International Studies Center at the Technical University of Kaiserslauten, Germany.

  • 23.
    Hansson, Hans
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolin, Mikael
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Real-time in embedded systems2017In: Systems, Controls, Embedded Systems, Energy, and Machines, CRC Press , 2017, p. 16-26-16-58Chapter in book (Other academic)
  • 24.
    Hansson, Hans
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Axelsson, Jakob
    Mälardalen University, School of Innovation, Design and Engineering.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Carlson, Jan
    Mälardalen University, School of Innovation, Design and Engineering.
    Crnkovic, Ivica
    Mälardalen University, School of Innovation, Design and Engineering.
    Lisper, Björn
    Mälardalen University, School of Innovation, Design and Engineering.
    Lundqvist, Kristina
    Mälardalen University, School of Innovation, Design and Engineering.
    Norström, Christer
    Mälardalen University, School of Innovation, Design and Engineering.
    Pettersson, Paul
    Mälardalen University, School of Innovation, Design and Engineering.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering.
    Sjödin, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    The PROGRESS Centre for Predictable Embedded Software Systems - Half-time report (edited version)2010Report (Other academic)
    Abstract [en]

    Presentation of the achievements and activities within the PROGRESS national strategic research centre 2006-2008

  • 25.
    Hansson, Hans
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Norström, Christer
    Mälardalen University, School of Innovation, Design and Engineering.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering.
    2 + 10 > 1 + 50 !2000In: Lecture Notes in Computer Science, vol 1800, Springer Berlin/Heidelberg, 2000, Vol. 1800 LNCS, p. 734-737Chapter in book (Refereed)
    Abstract [en]

    In traditional design of computer based systems some effort, say 1, is spent on the early modeling phases, and some very high effort, say 50, is spent on the later implementation and testing phases. It is the conjecture of this paper that the total effort can be substantially reduced if an increased effort, say 2, is spent on the early modeling phases. Such a shift in focus of efforts will also greatly improve the overall effects (both quality and cost-wise) of the systems dev eloped, there by leading to a better (denoted by "≻") design process. In this paper, w e specifically consider the design of safety-critical distributed real-time systems. © 2000 Springer-Verlag Berlin Heidelberg.

  • 26.
    Hansson, Hans
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Sjödin, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Beating the Automotive Code Complexity Challenge2008Conference paper (Refereed)
  • 27.
    Hansson, Hans
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Sjödin, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Sundmark, Daniel
    Mälardalen University, School of Innovation, Design and Engineering.
    Real-Time in Networked Embedded Systems2009In: Networked Embedded Systems, CRC Press, Taylor & Francis Group , 2009Chapter in book (Other academic)
  • 28.
    Hansson, Hans
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Åkerholm, Mikael
    Mälardalen University, Department of Computer Science and Electronics.
    Crnkovic, Ivica
    Mälardalen University, Department of Computer Science and Electronics.
    Törngren, Matrin
    KTH, Stockholm, Sweden .
    SaveCCM - a component model for safety-critical real-time systems2004In: Conference Proceedings of the EUROMICRO, Volume 30, 2004, 2004, p. 627-635Conference paper (Other academic)
    Abstract [en]

    Component-based development has proven effective in many engineering domains, and several general component technologies are available. Most of these are focused on providing an efficient software-engineering process. However for the majority of embedded systems, run-time efficiency and prediction of system behaviour are as important as process efficiency. This calls for specialized technologies. There is even a need for further specialized technologies adapted to different types of embedded systems, due to the heterogeneity of the domain and the close relation between the software and the often very application specific system. This paper presents the SaveCCM component model, intended for embedded control applications in vehicular systems. SaveCCM is a simple model in which flexibility is limited to facilitate analysis of real-time and dependability. We present and motivate the model, and provide examples of its use.

  • 29.
    Huselius, Joel
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Andersson, Johan
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Punnekkat, Sasikumar
    Mälardalen University, Department of Computer Science and Electronics.
    Automatic Generation and Validation of Models of Legacy Software2006In: Proceedings of the 12:th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA), Sydney, Australia, 2006, p. 342-349Conference paper (Refereed)
    Abstract [en]

    The modeling approach is not used to its full potential in maintenance of legacy systems. Often, models do not even exist. The main reasons being that the economic implications and practical hurdles in manually maintaining models of in-use legacy systems are considered too high by the industry. In this paper, we present a method for automated validation of models automatically generated from recordings of executing real-time embedded systems. This forms an essential constituent of a unified process for the automatic modeling of legacy software. We also present a study in which we automatically model a state-of-practice industrial robot control system, the results of which are clearly positive indicators of the viability of our approach.

  • 30.
    Huselius, Joel
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Kraft, Johan
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Punnekkat, Sasikumar
    Mälardalen University, Department of Computer Science and Electronics.
    Evaluating the Quality of Models Extracted from Embedded Real-Time Software2007In: Proceedings of the International Symposium and Workshop on Engineering of Computer Based Systems, 2007, p. 577-585Conference paper (Refereed)
    Abstract [en]

    Due to the high cost of modeling, model-based techniques are yet to make their impact in the embedded systems industry, which still persist on maintaining code-oriented legacy systems. Re-engineering existing code-oriented systems to fit model-based development is a risky endeavor due to the cost and efforts required to maintain correspondence between the code and model. We aim to reduce the cost of modeling and model maintenance by automating the process, thus facilitating model-based techniques. We have previously proposed the use of automatic model extraction from recordings of existing embedded real-time systems. To estimate the quality of the extracted models of timing behavior, we need a framework for objective evaluation. In this paper, we present such a framework to empirically test and compare extracted models, and hence obtain an implicit evaluation of methods for automatic model extraction. We present a set of synthetic benchmarks to be used as test cases for emulating timing behaviors of diverse systems with varying architectural styles, and extract automatic models out of them. We discuss the difficulties in comparing response time distributions, and present an intuitive and novel approach along with associated algorithms for performing such a comparison. Using our empirical framework, and the comparison algorithms, one could objectively determine the correspondence between the model and the system being modeled.

  • 31.
    Hänninen, Kaj
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. SICS, Swedish ICT, Västerås, Sweden.
    Thane, Henrik
    Safety integrity AB, Sweden.
    Saadatmand, Mehrdad
    SICS, Swedish ICT, Västerås, Sweden.
    Inadequate risk analysis might jeopardize the functional safety of modern systemsManuscript (preprint) (Other academic)
    Abstract [en]

    In the early 90s, researchers began to focus on security as an important property to address in combination with safety. Over the years, researchers have proposed approaches to harmonize activities within the safety and security disciplines. Despite the academic efforts to identify interdependencies and to propose combined approaches for safety and security, there is still a lack of integration between safety and security practices in the industrial context, as they have separate standards and independent processes often addressed and assessed by different organizational teams and authorities. Specifically, security concerns are generally not covered in any detail in safety standards potentially resulting in successfully safety-certified systems that still are open for security threats from e.g., malicious intents from internal and external personnel and hackers that may jeopardize safety. In recent years security has again received an increasing attention of being an important issue also in safety assurance, as the open interconnected nature of emerging systems makes them susceptible to security threats at a much higher degree than existing more confined products.

    This article presents initial ideas on how to extend safety work to include aspects of security during the context establishment and initial risk assessment procedures. The ambition of our proposal is to improve safety and increase efficiency and effectiveness of the safety work within the frames of the current safety standards, i.e., raised security awareness in compliance with the current safety standards. We believe that our proposal is useful to raise the security awareness in industrial contexts, although it is not a complete harmonization of safety and security disciplines, as it merely provides applicable guidance to increase security awareness in a safety context

  • 32.
    Kraft, Johan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Kienle, Holger
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Crnkovic, Ivica
    Mälardalen University, School of Innovation, Design and Engineering.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering.
    Software Maintenance Research in the PROGRESS Project for Predictable Embedded Software Systems2011In: 15th European Conference on Software Maintenance and Reengineering (CSMR'11) / [ed] Mens, T; Kanellopoulos, Y; Winter, A, Los Alamitos: IEEE Computer Society, 2011, p. 335-338Conference paper (Refereed)
    Abstract [en]

    PROGRESS is a project and strategic research centre at Malardalen University in Sweden that is funded for 2006-2010 by the Swedish Foundation for Strategic Research (SSF). PROGRESS research targets embedded software in the vehicular, automation, and telecom domains, focusing on the areas of component technology, verification and analysis for predictability, predictable execution, as well as reuse and maintenance of legacy embedded software. We first describe the funding, organization and research areas of PROGRESS, and then give several examples of PROGRESS research that addresses maintenance of legacy embedded software with the goal to improve program comprehension, quality assurance, and debugging. Specifically, we describe research in tracing and trace visualization, impact analysis of temporal behavior, slicing, and system-specific static analyses.

  • 33.
    Lisova, Elena
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Causevic, Aida
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hänninen, Kaj
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Thane, Henrik
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A Systematic Way to Incorporate Security in Safety Analysis2018In: Proceedings - 48th Annual IEEE/IFIP International Conference on Dependable Systems and Networks Workshops, DSN-W 2018, Luxembourg, Luxemburg, 2018, p. 166-171Conference paper (Refereed)
    Abstract [en]

    Today's systems are being built to connect to public or semi-public networks, are able to communicate with other systems, e.g., in the context of Internet-of-Things (IoT), involve multiple stakeholders, have dynamic system reconfigurations, and operate in increasingly unpredictable environments. In such complex systems, assuring safety and security in a continuous and joint effort is a major challenge, not the least due to the increasing number of attack surfaces arising from the increased connectivity. In this paper we present an approach that aims to bridge the gap between safety and security engineering. The potential of the approach is illustrated on the example of E-gas system, discussing the cases when unintentional faults as well as malicious attacks are taken into consideration when assuring safety of the described system. 

  • 34.
    Nolte, Thomas
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Lo Bello, Lucia
    University of Catania, Catania, Italy .
    Integration of networked subsystems in a resource constrained environment2006In: Proceedings of 11th IEEE International Conference on Emerging Technologies and Factory Automation (ETFA'06), Prague, Czech Republic, 2006, p. 905-912Conference paper (Refereed)
    Abstract [en]

    When developing embedded systems, there is currently a trend to move from a traditional federated approach, where computer systems are developed for their own dedicated hardware architecture, to an integrated approach, where computer systems are encapsulated as subsystems and later integrated on a shared hardware architecture. The task of integrating subsystems is complex, and in resource constrained systems efficient techniques and methods are required. In this paper the issue of subsystem integration is thoroughly discussed, and it is shown how to use Server-CAN, a network scheduler for the Controller Area Network, in the context of subsystem integration. As the network is a resource shared by all subsystems in adistributed architecture, its role in the integration process is particularly important. Here, the usage of an efficient and flexible network scheduler is essential.

  • 35.
    Nolte, Thomas
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering.
    Nolin, Mikael
    Mälardalen University, School of Innovation, Design and Engineering.
    Punnekkat, Sasikumar
    Mälardalen University, School of Innovation, Design and Engineering.
    Timing Analysis of CAN-Based Automotive Communication Systems2008In: Automotive Embedded Systems Handbook, CRC Press, 2008Chapter in book (Other academic)
  • 36.
    Nolte, Thomas
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Lo Bello, Lucia
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, Hans
    Mälardalen University, Department of Computer Science and Electronics.
    Facilitating subsystem integration by decoupling priority and identifier in CAN messages2006In: Proceedings of the 5th International Workshop on Real-Time Networks (RTN'06) in conjunction with the 18th Euromicro International Conference on Real-Time Systems (ECRTS'06), Dresden, Germany, 2006Conference paper (Refereed)
  • 37.
    Nolte, Thomas
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Nolin, M.
    Hansson, H. A.
    Mälardalen University, Department of Computer Science and Electronics.
    Real-time server-based communication with CAN2005In: IEEE transactions on industrial electronics (1982. Print), ISSN 0278-0046, E-ISSN 1557-9948, Vol. 1, no 3, p. 192-200Article in journal (Refereed)
    Abstract [en]

    This paper investigates the concept of share-driven scheduling of networks using servers with real-time properties. Share-driven scheduling provides fairness and bandwidth isolation between predictable as well as unpredictable streams of messages on the network. The need for this kind of scheduled real-time communication network is high in applications that have requirements on flexibility, both during development for assigning communication bandwidth to different applications, and during run-time to facilitate dynamic addition and removal of system components. We illustrate the share-driven scheduling concept by applying it to the popular controller area network (CAN). We propose a scheduling mechanism that we call simple server-scheduled CAN (S-3-CAN), for which we also present an associated timing analysis. Additionally, we present a variant of S'-CAN called periodic server-scheduled CAN (PS2-CAN), which for some network configurations gives lower worst-case response-times than S-3-CAN. Also for this improvement, a timing analysis is presented. Moreover, we use simulation to evaluate the timing performance of both S-3-CAN and PS2-CAN, comparing them with other scheduling mechanisms.

  • 38.
    Norström, Christer
    et al.
    Mälardalen University, Department of Computer Science and Electronics.
    Hansson, H. A.
    Mälardalen University, Department of Computer Science and Electronics.
    Special section on factory communication systems2005In: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050, Vol. 1, no 3, p. 149-150Article in journal (Other academic)
  • 39.
    Packalén, Sture
    et al.
    Uppsala universitet.
    Daniels, Mats
    Uppsala universitet.
    Hansson, Hans
    Uppsala universitet.
    MÄTNING OCH STYRNING1985 (ed. 1)Book (Other (popular science, discussion, etc.))
  • 40.
    Pop, P.
    et al.
    Technical University of Denmark, Kgs. Lyngby, Denmark.
    Scholle, D.
    Alten Sverige AB, Kista, Sweden.
    Šljivo, Irfan
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Widforss, Gunnar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rosqvist, Malin
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Safe cooperating cyber-physical systems using wireless communication: The SafeCOP approach2017In: Microprocessors and microsystems, ISSN 0141-9331, E-ISSN 1872-9436, Vol. 53, p. 42-50Article in journal (Refereed)
    Abstract [en]

    This paper presents an overview of the ECSEL project entitled “Safe Cooperating Cyber-Physical Systems using Wireless Communication” (SafeCOP), which runs during the period 2016–2019. SafeCOP targets safety-related Cooperating Cyber-Physical Systems (CO-CPS) characterised by use of wireless communication, multiple stakeholders, dynamic system definitions (openness), and unpredictable operating environments. SafeCOP will provide an approach to the safety assurance of CO-CPS, enabling thus their certification and development. The project will define a runtime manager architecture for runtime detection of abnormal behaviour, triggering if needed a safe degraded mode. SafeCOP will also develop methods and tools, which will be used to produce safety assurance evidence needed to certify cooperative functions. SafeCOP will extend current wireless technologies to ensure safe and secure cooperation, and also contribute to new standards and regulations, by providing certification authorities and standardization committees with the scientifically validated solutions needed to craft effective standards extended to also address cooperation and system-of-systems issues. The project has 28 partners from 6 European countries, and a budget of about 11 million Euros corresponding to about 1,300 person-months. 

  • 41.
    Pop, Paul
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Scholle, Detlef
    Alten Sverige AB.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Widforss, Gunnar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rosqvist, Malin
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IS (Embedded Systems).
    The SafeCOP ECSEL Project: Safe Cooperating Cyber-Physical Systems using Wireless Communication2016In: Proceedings - 19th Euromicro Conference on Digital System Design, DSD 2016, Institute of Electrical and Electronics Engineers Inc. , 2016, p. 532-538, article id 7723596Conference paper (Refereed)
    Abstract [en]

    This paper presents an overview of the ECSEL project entitled 'Safe Cooperating Cyber-Physical Systems using Wireless Communication' (SafeCOP), which runs during the period 2016 - 2019. SafeCOP targets safety-related Cooperating Cyber-Physical Systems (CO-CPS) characterised by use of wireless communication, multiple stakeholders, dynamic system definitions (openness), and unpredictable operating environments. SafeCOP will provide an approach to the safety assurance of CO-CPS, enabling thus their certification and development. The project will define a runtime manager architecture for runtime detection of abnormal behaviour, triggering if needed a safe degraded mode. SafeCOP will also develop methods and tools, which will be used to produce safety assurance evidence needed to certify cooperative functions. SafeCOP will extend current wireless technologies to ensure safe and secure cooperation. SafeCOP will also contribute to new standards and regulations, by providing certification authorities and standardization committees with the scientifically validated solutions needed to craft effective standards extended to also address cooperation and system-of-systems issues. The project has 28 partners from 6 European countries, and a budget of about 11 million Euros corresponding to about 1,300 person-months.

  • 42.
    Pozo, Francisco
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, G.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IS (Embedded Systems).
    Hansson, Hans A
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IS (Embedded Systems).
    Steiner, Wilfried
    TTTech Computertechnik AG.
    Schedule Synthesis for Next Generation Time-Triggered Networks2017Report (Other academic)
    Abstract [en]

    For handling frame transmissions in highly deterministic real-time networks, i.e. networks requiring low communication latency and minimal jitter, an offline time-triggered schedule indicating the dispatch times of all frames can be used. Generation of such an offline schedule is known to be a NPcomplete problem, with complexity driven by the size of the network, the number and complexity of the traffic temporal constraints, and link diversity (for instance, coexistence of wired and wireless links). As embedded applications become more complex and extend over larger geographical areas, there is a need to deploy larger real-time networks, but existing schedule synthesis mechanisms do not scale satisfactorily to the sizes of these networks, constituting a potential bottleneck for system designers. In this paper, we present an offline synthesis tool that overcomes this limitation and is capable of generating time-triggered schedules for networks with hundreds of nodes and thousands of temporal constraints, also for systems where wired and wireless links are combined. This tool models the problem with linear arithmetic constraints and solves them using a Satisfiability Modulo Theory (SMT) solver, a powerful general purpose tool successfully used in the past for synthesizing time-triggered schedules. To cope with complexity, our algorithm implements a segmented approach that divides the total problem into easily solvable smaller-size scheduling problems, whose solutions can be combined for achieving the final schedule. The paper also discusses a number of optimizations that increase the size and compactness of the solvable schedules. We evaluate our approach on a set of realistic large-size multi-hop networks, significantly bigger than those in the existing literature. The results show that our segmentation reduces the synthesis time dramatically, allowing generation of extremely large compact schedules.

  • 43.
    Pozo, Francisco
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Self-Healing Protocol: Repairing Scheduels Online after Link Failures in Time-Triggered NetworksIn: IEEE Transactions on Industrial Informatics, ISSN 1551-3203, E-ISSN 1941-0050Article in journal (Refereed)
    Abstract [en]

    The time-triggered paradigm is not adaptive, a static schedule determines the time-triggered communication and, then, any unpredicted change, like a link failure, might result in the loss of frames. Using spatial redundancy or recomputing a new schedule for replacement achieves fault tolerance only in moderate-size networks. With the increase in size and complexity of cyber-physical systems, more scalable and cost-efficient mechanisms are needed in order to complement conventional solutions. We propose a distributed Self-Healing Protocol that instead of recomputing the whole schedule, repairs the existent schedule at runtime. The basis of our protocol is the collaboration of nodes in the network to individually adjust their local schedules for rerouting the frames affected by link failures. Our protocol exhibits a high success rate compared to full rescheduling, as well as remarkable scalability; it repairs the schedule in milliseconds, whereas rescheduling requires minutes.

  • 44.
    Pozo, Francisco
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Work-in-Progress: A Hot-Patching Protocol for Repairing Time-Triggered Network Schedules2018In: 24TH IEEE REAL-TIME AND EMBEDDED TECHNOLOGY AND APPLICATIONS SYMPOSIUM (RTAS 2018) / [ed] Pellizzoni, R, 2018, p. 89-92Conference paper (Refereed)
    Abstract [en]

    Time-Triggered communication is based on generating an offfine static schedule that guarantees frame transmissions with reduced latency and low jitter. However, static schedules are not adaptive: if some unpredicted event happens, like a link failure, the schedule is not valid anymore and a new one needs to be synthesized from scratch. This paper presents a novel hot-patching protocol which seeks, after a link failure disconnecting two nodes, to find a new path to reconnect both nodes and restore during run-time the affected part of the schedule. We also introduce the concept of reparability as a desired property of the schedule, which increases the probability of our protocol to succeed. The first evaluation shows that our hot-patching protocol can recover from a link failure consistently in less than 25ms.

  • 45.
    Pozo, Francisco
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, W.
    TTTech Computertechnik AG, Vienna, Austria .
    SMT-based synthesis of TTEthernet schedules: A performance study2015In: 2015 10th IEEE International Symposium on Industrial Embedded Systems, SIES 2015 - Proceedings, 2015, p. 162-165Conference paper (Refereed)
    Abstract [en]

    Time-triggered networks, like TTEthernet, require adoption of a predefined schedule to guarantee low communication latency and minimal jitter. The synthesis of such schedules is a problem known to be NP-complete. In the past, specialized solvers have been used for synthesizing time-triggered schedules, but more recently general-purpose tools like Satisfiability Modulo Theories (SMT) solvers have reported synthesis of large network schedules in reasonable time for industrial purposes. An interesting characteristic of any general-purpose tool is that its configuration parameters can be tuned in order to fit specific problems and achieve increased performance. This paper presents a study identifying and assessing which SMT solver parameters have the highest impact on the performance when synthesizing schedules for time-triggered networks. The results show that with appropriate values of certain parameters, the time can be reduced significantly, up to 75% in the best cases compared to previous work. © 2015 IEEE.

  • 46.
    Pozo, Francisco
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, W.
    TTTech Computertechnik AG, Vienna, Austria.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Period-Aware Segmented Synthesis of Schedules for Multi-Hop Time-Triggered Networks2016In: 22nd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA 2016), IEEE, 2016, p. 170-175Conference paper (Refereed)
    Abstract [en]

    Time-triggered offline scheduling is a cost-efficien way to guarantee low communication end-to-end latency and minimal jitter for communication networks in real-time systems. The schedule is generated pre-runtime and indicates the transmission times of time-triggered frames such that contention is prevented. The synthesis of such offline schedules is a bin-packing problem, known to be NP-complete, with complexity driven by the constraints on frame transmissions, and the number of frames in the schedule. Satisfiability Modulo Theories combined with segmented approaches have been successfully used for synthesizing schedules of large networks. However, such synthesis did not take into account frames periods that are much shorter than the time to execute the schedule cycle. This paper presents a periodaware segmented approach that takes into account the frame periods in order to allocate various instances of a frame within a single cycle. We describe three different synthesis strategies and evaluate them with different synthetic experiments. The results show better performance for one of the strategies, which can synthesize schedules of large networks with high communication loads in less than one hour. We also report how the synthesis time and the schedule quality can change with different parameter configurations.

  • 47.
    Pozo, Francisco
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Steiner, W.
    TTTech Computertechnik AG, Vienna, Austria.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    A decomposition approach for SMT-based schedule synthesis for time-triggered networks2015In: 2015 IEEE 20th Conference on Emerging Technologies & Factory Automation (ETFA), 2015, p. Article number 7301436-Conference paper (Refereed)
    Abstract [en]

    Real-time networks have tight communication latency and minimal jitter requirements. One way to ensure these requirements is the implementation of a static schedule, which defines the transmission points in time of time-triggered frames. Synthesizing such static schedules is known to be an NP-complete problem where the complexity is driven by the large number of constraints imposed by the network. Satisfiabily Modulo Theories (SMT) have been proven powerful tools to synthesize schedules of medium-to-large industrial networks. However, the schedules of new extremely large networks, such as integrated multi-machine factory networks, are defined by an extremely large number of constraints exceeding the capabilities of being synthesized by the tool alone. This paper presents a decomposition approach that will allow us to improve to synthesize schedules with up to two orders of magnitude in terms of the number of constraints that can be handled. We also present an implementation of a dependency tree on top of the decomposition approach to address application-imposed constraints between frames.

  • 48.
    Pozo Pérez, Francisco Manuel
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Methods for large-scale time-triggered network scheduling2019In: Electronics (Switzerland), ISSN 2079-9292, Vol. 8, no 7, article id 738Article in journal (Refereed)
    Abstract [en]

    Future cyber–physical systems may extend over broad geographical areas, like cities or regions, thus, requiring the deployment of large real-time networks. A strategy to guarantee predictable communication over such networks is to synthesize an offline time-triggered communication schedule. However, this synthesis problem is computationally hard (NP-complete), and existing approaches do not scale satisfactorily to the required network sizes. This article presents a segmented offline synthesis method which substantially reduces this limitation, being able to generate time-triggered schedules for large hybrid (wired and wireless) networks. We also present a series of algorithms and optimizations that increase the performance and compactness of the obtained schedules while solving some of the problems inherent to segmented approaches. We evaluate our approach on a set of realistic large-size multi-hop networks, significantly larger than those considered in the existing literature. The results show that our segmentation reduces the synthesis time by up to two orders of magnitude.

  • 49.
    Pozo Pérez, Francisco Manuel
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Schedule reparability: Enhancing time-triggered network recovery upon link failures2019In: Proceedings - 2018 IEEE 24th International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2018, Institute of Electrical and Electronics Engineers Inc. , 2019, p. 147-156Conference paper (Refereed)
    Abstract [en]

    The time-triggered communication paradigm has been shown to satisfy temporal isolation while providing end to end delay guarantees through the synthesis of an offline schedule. However, this paradigm has severe flexibility limitations as any unpredicted change not anticipated by the schedule, such as a component failure, might result in a loss of frames. A typical solution is to use redundancy or replace and update the schedule offline anew. With the ever increase in size of networks and the need to reduce costs, supplementary solutions that enhance the reliability of such networks are also desired. In this paper, we introduce a repair algorithm capable of reacting to unpredicted link failures. The algorithm quickly modifies the schedule such that all frames are transmitted again within their timing guarantees. We found that the success of our algorithm increases significantly with the existence of empty slots spread over the schedule, an opposite approach compared to packing frames, commonly used in the literature. We propose a new ILP formulation that includes a maximization of frame and link intermissions to stretch empty slots over the schedule. Our results show that we can repair with 90% success rate within milliseconds to a valid schedule compared to a few minutes needed to re-schedule the whole network. 

  • 50.
    Pozo Pérez, Francisco Manuel
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Rodriguez-Navas, Guillermo
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Hansson, Hans
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Semi-Distributed Self-Healing Protocol for Online Schedule Repair after Network Failures2019Report (Other academic)
    Abstract [en]

    Adaptive requirements for networks with strict timing restrictions do challenge the static nature of the time-triggered communication paradigm. Continuous changes in the network topology during operation require frequent rescheduling, followed by schedule distribution, a process that is excessively time-consuming as it was intended to be performed only during the design phase. The fully-distributed Self-Healing Protocol introduced a collaborative method to quickly modify the local schedules of the nodes during runtime, after link failures. This protocol gets the network back to correct operation in milliseconds, but it assumes that only the nodes are able to modify their local schedules, which limited the achieved improvement. This paper proposes to shift to a semi-distributed strategy, where high-performance nodes are responsible for the nodes and links within a small network segment. These nodes rely on their privileged view of the system in order to reduce the response time, increase the healing success rate, and extend the fault model to include switch failures. 

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