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  • 1.
    Aarons, Gregory
    et al.
    Univ Calif San Diego, La Jolla, CA 92093 USA.;Child & Adolescent Serv Res Ctr, San Diego, CA USA..
    Green, Amy
    Univ Calif San Diego, La Jolla, CA 92093 USA..
    Moullin, Joanna
    Univ Calif San Diego, La Jolla, CA 92093 USA.;Univ Technol Sydney, Sydney, NSW, Australia..
    Ehrhart, Mark
    San Diego State Univ, San Diego, CA 92182 USA.;Univ Cent Florida, Orlando, FL 32816 USA..
    Ducarroz, Simon
    Ctr Reg Prevent Canc, Ctr Hygee, St Priest En Jarez, France..
    Sevdalis, Nick
    Kings Coll London, London, England..
    Hasson, Henna
    Karolinska Inst, Stockholm, Sweden.;Stockholm Cty Council, Ctr Epidemiol & Community Med, Stockholm, Sweden..
    von Thiele Schwarz, Ulrica
    Mälardalen University, School of Health, Care and Social Welfare. Karolinska Inst, Stockholm, Sweden.
    James, Sigrid
    Univ Kassel, Kassel, Germany..
    Willging, Cathleen
    Pacific Inst Res & Evaluat, Behav Hlth Res Ctr Southwest, Albuquerque, NM USA..
    Fostering international collaborations in implementation science2018In: Implementation Science, ISSN 1748-5908, E-ISSN 1748-5908, Vol. 13Article in journal (Other academic)
  • 2.
    Abbas, M.
    et al.
    University Pretoria, South Africa.
    De La Sen, M.
    University of the Basque Country, Spain.
    Nazir, Talat
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Common Fixed Points of Generalized Rational Type Cocyclic Mappings in Multiplicative Metric Spaces2015In: Discrete dynamics in nature and society, ISSN 1026-0226, E-ISSN 1607-887X, Vol. 2015, article id 532725Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to present fixed point result of mappings satisfying a generalized rational contractive condition in the setup of multiplicative metric spaces. As an application, we obtain a common fixed point of a pair of weakly compatible mappings. Some common fixed point results of pair of rational contractive types mappings involved in cocyclic representation of a nonempty subset of a multiplicative metric space are also obtained. Some examples are presented to support the results proved herein. Our results generalize and extend various results in the existing literature.

  • 3.
    Abbas, M.
    et al.
    Ton Duc Thang University, Ho Chi Minh City, Viet Nam.
    Nazir, Talat
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Popović, B.
    University of Kragujevac, Serbia.
    Radenović, S.
    University of Belgrade, Belgrade.
    On Weakly Commuting Set-Valued Mappings on a Domain of Sets Endowed with Directed Graph2017In: Results in Mathematics, ISSN 1422-6383, Vol. 71, no 3-4, p. 1277-1295Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to present coincidence and common fixed point results of set-valued mappings satisfying certain generalized graphic F-contractive conditions on a family of sets endowed with a graph. It is worth mentioning that these results are obtained without appealing to any form of continuity of mappings involved herein. Some examples are presented to support the results proved in this paper. Our results unify, generalize and extend various comparable results in the existing literature. © 2016, Springer International Publishing.

  • 4.
    Abbas, Mujahid
    et al.
    Ton Duc Thang Univ, Ho Chi Minh City, Vietnam..
    Nazir, Talat
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Lampert, Tatjana Aleksic
    Fac Sci, Dept Math, Radoja Domanovica 12, Kragujevac 34000, Serbia.
    Radenovic, Stojan
    State Univ Novi Pazar, Serbia..
    Common fixed points of set-valued F-contraction mappings on domain of sets endowed with directed graph2017In: Computational and Applied Mathemathics, ISSN 0101-8205, Vol. 36, no 4, p. 1607-1622Article in journal (Refereed)
    Abstract [en]

    The aim of this paper is to present common fixed point results of set-valued graphic F-contraction mappings on a family of sets endowed with a graph. Some examples are presented to support the results proved herein. Our results unify, generalize and extend various results in the existing literature.

  • 5.
    Abbaspour Asadollah, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bugs and Debugging of Concurrent and Multicore Software2016Licentiate thesis, comprehensive summary (Other academic)
  • 6.
    Abbaspour Asadollah, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Concurrency Bugs: Characterization, Debugging and Runtime Verification2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Concurrent software has been increasingly adopted in recent years, mainly due to the introduction of multicore platforms. However, concurrency bugs are still difficult to test and debug due to their complex interactions involving multiple threads (or tasks). Typically, real world concurrent software has huge state spaces. Thus, testing techniques and handling of concurrency bugs need to focus on exposing the bugs in this large space. However, existing solutions typically do not provide debugging information to developers (and testers) for understanding the bugs.

    Our work focuses on improving concurrent software reliability via three contributions: 1) An investigation of concurrent software challenges with the aim to help developers (and testers) to better understand concurrency bugs. We propose a classification of concurrency bugs and discuss observable properties of each type of bug. In addition, we identify a number of gaps in the body of knowledge on concurrent software bugs and their debugging. 2) Exploring concurrency related bugs in real-world software with respect to the reproducibility of bugs, severity of their consequence and effort required to fix them. Our findings here is that concurrency bugs are different from other bugs in terms of their fixing time and severity, while they are similar in terms of reproducibility. 3) A model for monitoring concurrency bugs and the implementation and evaluation of a related runtime verification tool to detect the bugs. In general, runtime verification techniques are used to (a) dynamically verify that the observed behaviour matches specified properties and (b) explicitly recognize understandable behaviors in the considered software. Our implemented tool is used to detect concurrency bugs in embedded software and is in its current form tailored for the FreeRTOS operating system. It helps developers and testers to automatically identify concurrency bugs and subsequently helps to reduce their finding and fixing time.

  • 7.
    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. 

  • 8.
    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.

  • 9.
    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. 

  • 10.
    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)
  • 11.
    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.

  • 12.
    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.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    Abbaspour, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Electromyogram Signal Enhancement and Upper-Limb Myoelectric Pattern Recognition2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Losing a limb causes difficulties in our daily life. To regain the ability to live an independent life, artificial limbs have been developed. Hand prostheses belong to a group of artificial limbs that can be controlled by the user through the activity of the remnant muscles above the amputation. Electromyogram (EMG) is one of the sources that can be used for control methods for hand prostheses. Surface EMGs are powerful, non-invasive tools that provide information about neuromuscular activity of the subjected muscle, which has been essential to its use as a source of control for prosthetic limbs. However, the complexity of this signal introduces a big challenge to its applications. EMG pattern recognition to decode different limb movements is an important advancement regarding the control of powered prostheses. It has the potential to enable the control of powered prostheses using the generated EMG by muscular contractions as an input. However, its use has yet to be transitioned into wide clinical use. Different algorithms have been developed in state of the art to decode different movements; however, the challenge still lies in different stages of a successful hand gesture recognition and improvements in these areas could potentially increase the functionality of powered prostheses. This thesis firstly focuses on improving the EMG signal’s quality by proposing novel and advanced filtering techniques. Four efficient approaches (adaptive neuro-fuzzy inference system-wavelet, artificial neural network-wavelet, adaptive subtraction and automated independent component analysis-wavelet) are proposed to improve the filtering process of surface EMG signals and effectively eliminate ECG interferences. Then, the offline performance of different EMG-based recognition algorithms for classifying different hand movements are evaluated with the aim of obtaining new myoelectric control configurations that improves the recognition stage. Afterwards, to gain proper insight on the implementation of myoelectric pattern recognition, a wide range of myoelectric pattern recognition algorithms are investigated in real time. The experimental result on 15 healthy volunteers suggests that linear discriminant analysis (LDA) and maximum likelihood estimation (MLE) outperform other classifiers. The real-time investigation illustrates that in addition to the LDA and MLE, multilayer perceptron also outperforms the other algorithms when compared using classification accuracy and completion rate.

  • 17.
    Abbaspour, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Evaluation of surface EMG-based recognition algorithms for decoding hand movementsManuscript (preprint) (Other academic)
  • 18.
    Abbaspour, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Proposing Combined Approaches to Remove ECG Artifacts from Surface EMG Signals2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Electromyography (EMG) is a tool routinely used for a variety of applications in a very large breadth of disciplines. However, this signal is inevitably contaminated by various artifacts originated from different sources. Electrical activity of heart muscles, electrocardiogram (ECG), is one of sources which affects the EMG signals due to the proximity of the collection sites to the heart and makes its analysis non-reliable. Different methods have been proposed to remove ECG artifacts from surface EMG signals; however, in spite of numerous attempts to eliminate or reduce this artifact, the problem of accurate and effective de-noising of EMG still remains a challenge. In this study common methods such as high pass filter (HPF), gating method, spike clipping, hybrid technique, template subtraction, independent component analysis (ICA), wavelet transform, wavelet-ICA, artificial neural network (ANN), and adaptive noise canceller (ANC) and adaptive neuro-fuzzy inference system (ANFIS) are used to remove ECG artifacts from surface EMG signals and their accuracy and effectiveness is investigated. HPF, gating method and spike clipping are fast; however they remove useful information from EMG signals. Hybrid technique and ANC are time consuming. Template subtraction requires predetermined QRS pattern. Using wavelet transform some artifacts remain in the original signal and part of the desired signal is removed. ICA requires multi-channel signals. Wavelet-ICA approach does not require multi-channel signals; however, it is user-dependent. ANN and ANFIS have good performance, but it is possible to improve their results by combining them with other techniques. For some applications of EMG signals such as rehabilitation, motion control and motion prediction, the quality of EMG signals is very important. Furthermore, the artifact removal methods need to be online and automatic. Hence, efficient methods such as ANN-wavelet, adaptive subtraction and automated wavelet-ICA are proposed to effectively eliminate ECG artifacts from surface EMG signals. To compare the results of the investigated methods and the proposed methods in this study, clean EMG signals from biceps and deltoid muscles and ECG artifacts from pectoralis major muscle are recorded from five healthy subjects to create 10 channels of contaminated EMG signals by adding the recorded ECG artifacts to the clean EMG signals. The artifact removal methods are also applied to the 10 channels of real contaminated EMG signals from pectoralis major muscle of the left side. Evaluation criteria such as signal to noise ratio, relative error, correlation coefficient, elapsed time and power spectrum density are used to evaluate the performance of the proposed methods. It is found that the performance of the proposed ANN-wavelet method is superior to the other methods with a signal to noise ratio, relative error and correlation coefficient of 15.53, 0.01 and 0.98 respectively.

  • 19.
    Abbaspour, Sara
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Surface EMG signal processing: Removing ECG interferences and classifying hand movements2017In: Medicinteknikdagarna 2017 MTD 2017, Västerås, Sweden, 2017Conference paper (Refereed)
  • 20.
    Abbaspour, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Chiew, Thiam Kian
    University of Malaya, Kuala Lumpur, Malaysia .
    Web Service Response Time Monitoring: Architecture and Validation2011In: Communications in Computer and Information Science Volume 164 CCIS, 2011, 2011, p. 276-282Conference paper (Refereed)
    Abstract [en]

    Web services are used in many Web applications in order to save time and cost during software development process. To peruse Web service response time, a suitable tool is needed to automate the measurement of the response time. However, not many suitable tools are available for automatic measurement of response time. This research is carried out in the context of quality of Web services in order to measure and visualize Web service response time. The method proposed in this research for accomplishing this goal is based on creating a proxy for connecting to the required Web service, and then calculating the Web services response time via the proxy. A software tool is designed based on the proposed method in order to guide the implementation that is still in progress. The tool can be validated through empirical validation using three test cases for three different Web service access situations.

  • 21.
    Abbaspour, Sara
    et al.
    Amirkabir University of Technology, Tehran, Iran.
    Fallah, Ali
    Amirkabir University of Technology, Tehran, Iran.
    A Combination Method for Electrocardiogram Rejection from Surface Electromyogram2014In: Open Biomedical Engineering Journal, ISSN 1874-1207, E-ISSN 1874-1207, Vol. 8, no 1, p. 13-19Article in journal (Refereed)
    Abstract [en]

    The electrocardiogram signal which represents the electrical activity of the heart provides interference in the recording of the electromyogram signal, when the electromyogram signal is recorded from muscles close to the heart. Therefore, due to impurities, electromyogram signals recorded from this area cannot be used. In this paper, a new method was developed using a combination of artificial neural network and wavelet transform approaches, to eliminate the electrocardiogram artifact from electromyogram signals and improve results. For this purpose, contaminated signal is initially cleaned using the neural network. With this process, a large amount of noise can be removed. However, low-frequency noise components remain in the signal that can be removed using wavelet. Finally, the result of the proposed method is compared with other methods that were used in different papers to remove electrocardiogram from electromyogram. In this paper in order to compare methods, qualitative and quantitative criteria such as signal to noise ratio, relative error, power spectrum density and coherence have been investigated for evaluation and comparison. The results of signal to noise ratio and relative error are equal to 15.6015 and 0.0139, respectively.

  • 22.
    Abbaspour, Sara
    et al.
    Amirkabir University of technology,Tehran, Iran.
    Fallah, Ali
    Amirkabir University of technology,Tehran, Iran.
    Removing ECG Artifact from the Surface EMG Signal Using Adaptive Subtraction Technique2014In: Biomedical Physics and Engineering, ISSN 2251-7200, Vol. 4, no 1, p. 33-38Article in journal (Refereed)
    Abstract [en]

    Background: The electrocardiogram artifact is a major contamination in the electromyogram signals when electromyogram signal is recorded from upper trunk muscles and because of that the contaminated electromyogram is not useful. Objective: Removing electrocardiogram contamination from electromyogram signals. Methods: In this paper, the clean electromyogram signal, electrocardiogram artifact and electrocardiogram signal were recorded from leg muscles, the pectoralis major muscle of the left side and V4, respectively. After the pre-processing, contaminated electromyogram signal is simulated with a combination of clean electromyogram and electrocardiogram artifact. Then, contaminated electromyogram is cleaned using adaptive subtraction method. This method contains some steps; (1) QRS detection, (2) formation of electrocardiogram template by averaging the electrocardiogram complexes, (3) using low pass filter to remove undesirable artifacts, (4) subtraction. Results: Performance of our method is evaluated using qualitative criteria, power spectrum density and coherence and quantitative criteria signal to noise ratio, relative error and cross correlation. The result of signal to noise ratio, relative error and cross correlation is equal to 10.493, 0.04 and %97 respectively. Finally, there is a comparison between proposed method and some existing methods. Conclusion: The result indicates that adaptive subtraction method is somewhat effective to remove electrocardiogram artifact from contaminated electromyogram signal and has an acceptable result.

  • 23.
    Abbaspour, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Fallah, Ali
    Amirkabir University of Technology, Tehran, Iran.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gholamhosseini, Hamid
    Auckland University of Technology, Auckland, New Zealand.
    A Novel Approach for Removing ECG Interferences from Surface EMG signals Using a Combined ANFIS and Wavelet2016In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 26, p. 52-59Article in journal (Refereed)
    Abstract [en]

    In recent years, the removal of electrocardiogram (ECG) interferences from electromyogram (EMG) signals has been given large consideration. Where the quality of EMG signal is of interest, it is important to remove ECG interferences from EMG signals. In this paper, an efficient method based on a combination of adaptive neuro-fuzzy inference system (ANFIS) and wavelet transform is proposed to effectively eliminate ECG interferences from surface EMG signals. The proposed approach is compared with other common methods such as high-pass filter, artificial neural network, adaptive noise canceller, wavelet transform, subtraction method and ANFIS. It is found that the performance of the proposed ANFIS-wavelet method is superior to the other methods with the signal to noise ratio and relative error of 14.97 dB and 0.02 respectively and a significantly higher correlation coefficient (p < 0.05).

  • 24.
    Abbaspour, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gholamhosseini, H.
    School of Engineering, Auckland University of TechnologyAuckland, New Zealand .
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Evaluation of wavelet based methods in removing motion artifact from ECG signal2015In: IFMBE Proceedings, 2015, p. 1-4Conference paper (Refereed)
    Abstract [en]

    Accurate recording and precise analysis of the electrocardiogram (ECG) signals are crucial in the pathophysiological study and clinical treatment. These recordings are often corrupted by different artifacts. The aim of this study is to propose two different methods, wavelet transform based on nonlinear thresholding and a combination method using wavelet and independent component analysis (ICA), to remove motion artifact from ECG signals. To evaluate the performance of the proposed methods, the developed techniques are applied to the real and simulated ECG data. The results of this evaluation are presented using quantitative and qualitative criteria. The results show that the proposed methods are able to reduce motion artifacts in ECG signals. Signal to noise ratio (SNR) of the wavelet technique is equal to 13.85. The wavelet-ICA method performed better with SNR of 14.23.

  • 25.
    Abbaspour, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Electromyography signal analysis: Electrocardiogram artifact removal and classifying hand movements2018In: World Congress on Medical Physics and Biomedical Engineering IUPESM, 2018Conference paper (Refereed)
  • 26.
    Abbaspour, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gholamhosseini, Hamid
    Auckland University of Technology, New Zealand.
    ECG Artifact Removal from Surface EMG Signal Using an Automated Method Based on Wavelet-ICA2015In: Studies in Health Technology and Informatics, Volume 211, 2015, p. 91-97Conference paper (Refereed)
    Abstract [en]

    This study aims at proposing an efficient method for automated electrocardiography (ECG) artifact removal from surface electromyography (EMG) signals recorded from upper trunk muscles. Wavelet transform is applied to the simulated data set of corrupted surface EMG signals to create multidimensional signal. Afterward, independent component analysis (ICA) is used to separate ECG artifact components from the original EMG signal. Components that correspond to the ECG artifact are then identified by an automated detection algorithm and are subsequently removed using a conventional high pass filter. Finally, the results of the proposed method are compared with wavelet transform, ICA, adaptive filter and empirical mode decomposition-ICA methods. The automated artifact removal method proposed in this study successfully removes the ECG artifacts from EMG signals with a signal to noise ratio value of 9.38 while keeping the distortion of original EMG to a minimum.

  • 27.
    Abdul-Ahad, Amir Stefan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Cürüklü, Baran
    Mälardalen University, School of Innovation, Design and Engineering.
    Mahmoud, W. A.
    Al-Isra Private University, Amman, Jordan.
    Robust distance-based watermarking for digital image2008In: Proceedings of the 2008 International Conference on Security and Management, SAM 2008, 2008, p. 404-409Conference paper (Refereed)
    Abstract [en]

    In this paper, an algorithm is developed to invisibly watermark a cover object (color image) using watermark object (iconic image). The algorithm is based on the distances among the addresses of values of the cover object. These distances use to make the embedding. The order of manipulating these distances are specified by the values of the watermark data which is dealt with serially. The algorithm serves and achieves self encryption key. Each watermark object has its unique pattern of distances at different possible lengths of distance bits. This enhances the complexity of sequential embedding. The algorithm is tested using direct and single level and double level of Two-Dimensional Discrete Wavelet Transform (2D DWT) embeddings. Two important issues are addressed. Firstly is to achieve a high Peak Signal to Noise Ratio (PSNR). The ratio was found to increase with an increasing of distance bits. Secondly is that the watermarked object retains the same properties of cover object. The algorithm shows resisting and withstanding against the most important attacks. Some of these include the lossy compression, blurring, resize and some types of Noise.

  • 28. Abdul-Ahad, Amir Stefan
    et al.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering.
    Larsson, Thomas
    Mälardalen University, School of Innovation, Design and Engineering.
    Mahmoud, Waleed A.
    Robust Distance-Based Watermarking for Digital Video2008In: Proceedings of The Annual SIGRAD Conference, Stockholm, 2008Conference paper (Refereed)
  • 29.
    Abdul-Ahad, Amir Stefan
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Çürüklü, Baran
    Mälardalen University, School of Innovation, Design and Engineering.
    Folke, Mia
    Mälardalen University, School of Innovation, Design and Engineering.
    Lindén, Maria
    Mälardalen University, School of Innovation, Design and Engineering.
    Indirect Wavelet-Based Cardio Arrhythmia Detection Algorithm2008In: Medicinteknikdagarna, Gothenburg, Sweden, 2008, p. 14-15Conference paper (Refereed)
  • 30.
    Abdullah, Syed Md Jakaria
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Moghaddami Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Towards Implementation of Virtual-Clustered Multiprocessor Scheduling in Linux2013In: Proceedings of the 8th IEEE International Symposium on Industrial Embedded Systems, SIES 2013, 2013, p. 97-100Conference paper (Refereed)
    Abstract [en]

    Cluster based multiprocessor scheduling can be seen as a hybrid approach combining benefits of both partitioned and global scheduling. Virtual clustering further enhances it by providing dynamic cluster resource allocation and applying hierarchical scheduling techniques. Over the years, the study of virtual cluster scheduling has been limited to theoretical analysis. In this paper, we present our initial ideas about implementing virtual cluster scheduling in Linux. The purpose of this implementation is twofold: (i) we would like to demonstrate the feasibility of its implementation in an operating system, without modifying the kernel source code, (ii) we present practical insights on the overhead of implementing this framework.

  • 31.
    Abecassis-Moedas, Celine
    et al.
    Univ Catolica Portuguesa, Catolica Lisbon Sch Business & Econ, Lisbon, Portugal.
    Ben Mahmoud-Jouini, Sihem
    HEC Paris, Innovat & Entrepreneurship Ctr, Paris, France.
    Dell'Era, Claudio
    Politecn Milan, Dept Management Econ & Ind Engn, Milan, Italy.
    Manceau, Delphine
    Univ Penn, Wharton Sch, Philadelphia.
    Verganti, Roberto
    Politecnico di Milano.
    Key resources and internationalization modes of creative knowledge-intensive business services: The case of design consultancies2012In: Creativity and Innovation Management, ISSN 0963-1690, E-ISSN 1467-8691, Vol. 21, no 3, p. 315-331Article in journal (Refereed)
    Abstract [en]

    In the knowledge economy, knowledge-intensive business services (KIBS) are a key driver for innovation and competitiveness. The internationalization of these businesses raises challenges given their specificities such as knowledge intensity, the importance of customer interaction and intimacy in service delivery. This paper focuses on design consultancies as a specific type of creative KIBS for which these characteristics are emphasized. The objective of this research is to analyse the resources leveraged by the firms to compete internationally. It is based on 11 case studies of design consultancies located in five different countries (France, Italy, Portugal, Spain and the UK) that were selected for their capacity to perform at the international level for several years. The paper advances three internationalization modes depending on contingent variables and focusing on specific resources that enable international competitiveness: star-based, process-based and glocality-based. In star-based creative KIBS, the individual designer has developed a reputation that attracts customers internationally, operating as a brand. In process-based creative KIBS, the reputation of a collective creative process attracts clients from other countries. In glocality-based creative KIBS, the geographical proximity obtained by opening international offices helps to develop a close understanding of the client through frequent interactions, and also to know the client's market well and to better understand local codes and signs. These modes complement those presented in the existing internationalization literature which takes the peculiarities of creative KIBS into consideration.

  • 32.
    Abedini, M.
    et al.
    Department of Industrial Engineering, Iran University of Science and Technology, Tehran, Iran.
    Ahmadzadeh, Farzaneh
    Mälardalen University, School of Innovation, Design and Engineering, Innovation and Product Realisation.
    Noorossana, R.
    Department of Industrial Engineering, Iran University of Science and Technology, Tehran, Iran.
    Customer credit scoring using a hybrid data mining approach2016In: Kybernetes, ISSN 0368-492X, E-ISSN 1758-7883, Vol. 45, no 10, p. 1576-1588Article in journal (Refereed)
    Abstract [en]

    Purpose: A crucial decision in financial services is how to classify credit or loan applicants into good and bad applicants. The purpose of this paper is to propose a four-stage hybrid data mining approach to support the decision-making process. Design/methodology/approach: The approach is inspired by the bagging ensemble learning method and proposes a new voting method, namely two-level majority voting in the last stage. First some training subsets are generated. Then some different base classifiers are tuned and afterward some ensemble methods are applied to strengthen tuned classifiers. Finally, two-level majority voting schemes help the approach to achieve more accuracy. Findings: A comparison of results shows the proposed model outperforms powerful single classifiers such as multilayer perceptron (MLP), support vector machine, logistic regression (LR). In addition, it is more accurate than ensemble learning methods such as bagging-LR or rotation forest (RF)-MLP. The model outperforms single classifiers in terms of type I and II errors; it is close to some ensemble approaches such as bagging-LR and RF-MLP but fails to outperform them in terms of type I and II errors. Moreover, majority voting in the final stage provides more reliable results. Practical implications: The study concludes the approach would be beneficial for banks, credit card companies and other credit provider organisations. Originality/value: A novel four stages hybrid approach inspired by bagging ensemble method proposed. Moreover the two-level majority voting in two different schemes in the last stage provides more accuracy. An integrated evaluation criterion for classification errors provides an enhanced insight for error comparisons.

  • 33.
    Abelli, Björn
    Mälardalen University, School of Business.
    Directing and Enacting the Information System2007In: Advances in Information Systems Development: New Methods and Practice for the Networked Society, Volume 2, Issue PART 2, 2007, p. 13-23Conference paper (Refereed)
  • 34.
    Abelli, Björn
    Mälardalen University, School of Business.
    Enacting the e-Society2006In: Proceedings of the IADIS International Conference e-Society 2006, 2006, p. 285-298Conference paper (Refereed)
  • 35.
    Abelli, Björn
    Mälardalen University, School of Business.
    On Stage!: Playwriting, Directing and Enacting the Informing Processes.2007Doctoral thesis, monograph (Other scientific)
    Abstract [en]

    Within the discipline of information systems sometimes the conception of the main object is that the information system must be computer based. An example of an information system that is non-computer based is the scenic theatre performance. Input is the message or knowledge the participants of the theatre production want to pass over to the audience; output is the information and experiences the performance in itself mediates to the audience. This has been produced through a system development process; although the developers not always have been aware about what development model has been used.

    The dissertation combines some of the concepts found in theatre production with traditional system development concepts, and hence introduces new perspectives into the area of information systems. Some of the main findings in the study of theatre productions were the triplicity of a theatre production as a development process, an information system and an organization at the same time; the integrated relations of context, developers and users, which leads to spontaneous changes and overlaps of development roles; and the narrative and dramaturgical approach in the practical use of methods and techniques.

    These aspects should be useful also in development of other types of information systems, whether computer based or using other information technologies. The triplicity gives arguments to redefine each of these concepts.

    The generalizability of this approach has been validated through a second study, at a folk high school, which showed that models and concepts from theatre productions are possible to generalize to other information system areas than theatre, and that the borders of the organization coincides with the borders of the information system. Especially temporary organizations must be seen as ongoing, continuous development processes.

  • 36.
    Abelli, Björn
    Mälardalen University, School of Business.
    Programmeringens grunder - med exempel i C#2004Book (Other (popular science, discussion, etc.))
    Abstract [en]

    Detta är en lärobok i grundläggande programmering. Den fokuserar på att lära ut det som är gemensamt för de flesta programmeringsspråk – de grundläggande elementen och programkonstruktionerna och hur dessa relaterar till varandra, oberoende av språket. Vilket språk programmet skrivs i måste vara underordnat den uppgift programmet skall lösa. Boken går därför igenom grunderna i strukturerad programmering och visar otaliga exempel i såväl flödesdiagram, strukturdiagram, pseudokod som i källkod. I slutet av boken finns kapitel som går igenom grunderna även i objektorienterad programmering.

    Boken tonar ner inlärningen av ett specifikt programmeringsspråk, men i slutändan måste program ändå skrivas i något språk. Exemplen är skrivna i C# som har slagit igenom som ett praktiskt programmeringsspråk på mycket kort tid och redan börjat göra sitt intåg i högskolekurser i programmering.

    I första hand är boken avsedd för nybörjare i programmering på högskolenivå, som vill lära sig programmeringens grunder.

  • 37.
    Abelli, Björn
    Mälardalen University, School of Business.
    Theatre production : a system development process 2004Licentiate thesis, monograph (Other scientific)
  • 38.
    Abelli, Björn
    et al.
    Mälardalen University, School of Business.
    Révay, Péter
    Mälardalen University, School of Business.
    To Be or Not To Be Computer Based2004In: Proceedings of microCAD 2004, 2004, p. 1-8Conference paper (Refereed)
  • 39.
    Abola, Benard
    et al.
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Department of Mathematics, School of Physical Sciences, Makerere University, Kampala, Uganda.
    Biganda, Pitos
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics. Department of Mathematics, College of Natural and Applied Sciences, University of Dar es Salaam,Tanzania.
    Engström, Christopher
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    Mango, J. M.
    Department of Mathematics, School of Physical Sciences, Makerere University, Kampala, Uganda.
    Kakuba, G.
    Department of Mathematics, School of Physical Sciences, Makerere University, Kampala, Uganda.
    Silvestrov, Sergei
    Mälardalen University, School of Education, Culture and Communication, Educational Sciences and Mathematics.
    PageRank in evolving tree graphs2018In: Stochastic Processes and Applications: SPAS2017, Västerås and Stockholm, Sweden, October 4-6, 2017 / [ed] Sergei Silvestrov, Anatoliy Malyarenko, Milica Rančić, Springer, 2018, Vol. 271, p. 375-390Chapter in book (Refereed)
    Abstract [en]

    In this article, we study how PageRank can be updated in an evolving tree graph. We are interested in finding how ranks of the graph can be updated simultaneously and effectively using previous ranks without resorting to iterative methods such as the Jacobi or Power method. We demonstrate and discuss how PageRank can be updated when a leaf is added to a tree, at least one leaf is added to a vertex with at least one outgoing edge, an edge added to vertices at the same level and forward edge is added in a tree graph. The results of this paper provide new insights and applications of standard partitioning of vertices of the graph into levels using breadth-first search algorithm. Then, one determines PageRanks as the expected numbers of random walk starting from any vertex in the graph. We noted that time complexity of the proposed method is linear, which is quite good. Also, it is important to point out that the types of vertex play essential role in updating of PageRank.

  • 40.
    Abrahamsson, H.
    et al.
    RISE, SICS, Germany.
    Abdesslem, F. B.
    RISE, SICS, Germany.
    Ahlgren, B.
    RISE, SICS, Germany.
    Brunstrom, A.
    Karlstad University, Sweden.
    Marsh, I.
    RISE, SICS, Germany.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Connected Vehicles in Cellular Networks: Multi-Access Versus Single-Access Performance2018In: TMA 2018 - Proceedings of the 2nd Network Traffic Measurement and Analysis Conference, Institute of Electrical and Electronics Engineers Inc. , 2018Conference paper (Refereed)
    Abstract [en]

    Connected vehicles can make roads traffic safer and more efficient, but require the mobile networks to handle time-critical applications. Using the MONROE mobile broadband measurement testbed we conduct a multi-access measurement study on buses. The objective is to understand what network performance connected vehicles can expect in today's mobile networks, in terms of transaction times and availability. The goal is also to understand to what extent access to several operators in parallel can improve communication performance. In our measurement experiments we repeatedly transfer warning messages from moving buses to a stationary server. We triplicate the messages and always perform three transactions in parallel over three different cellular operators. This creates a dataset with which we can compare the operators in an objective way and with which we can study the potential for multi-access. In this paper we use the triple-access dataset to evaluate single-access selection strategies, where one operator is chosen for each transaction. We show that if we have access to three operators and for each transaction choose the operator with best access technology and best signal quality then we can significantly improve availability and transaction times compared to the individual operators. The median transaction time improves with 6% compared to the best single operator and with 61% compared to the worst single operator. The 90-percentile transaction time improves with 23% compared to the best single operator and with 65% compared to the worst single operator.

  • 41.
    Abrahamsson, Henrik
    Mälardalen University, School of Innovation, Design and Engineering.
    Internet Traffic Management2008Licentiate thesis, comprehensive summary (Other scientific)
  • 42.
    Abrahamsson, Henrik
    Mälardalen University, School of Innovation, Design and Engineering.
    Network overload avoidance by traffic engineering and content caching2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Internet traffic volume continues to grow at a great rate, now driven by video and TV distribution. For network operators it is important to avoid congestion in the network, and to meet service level agreements with their customers.  This thesis presents work on two methods operators can use to reduce links loads in their networks: traffic engineering and content caching.

    This thesis studies access patterns for TV and video and the potential for caching.  The investigation is done both using simulation and by analysis of logs from a large TV-on-Demand system over four months.

    The results show that there is a small set of programs that account for a large fraction of the requests and that a comparatively small local cache can be used to significantly reduce the peak link loads during prime time. The investigation also demonstrates how the popularity of programs changes over time and shows that the access pattern in a TV-on-Demand system very much depends on the content type.

    For traffic engineering the objective is to avoid congestion in the network and to make better use of available resources by adapting the routing to the current traffic situation. The main challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands.

    This thesis proposes L-balanced routings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level L. L-balanced routing gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic.  We present an L-balanced routing algorithm and a heuristic search method for finding L-balanced weight settings for the legacy routing protocols OSPF and IS-IS. We show that the search and the resulting weight settings work well in real network scenarios.

  • 43.
    Abrahamsson, Henrik
    et al.
    Swedish Inst of Computer Science, Kista, Sweden .
    Ahlgren, Bengt
    Swedish Inst of Computer Science, Kista, Sweden .
    Using Empirical Distributions to Characterize Web Client Traffic and to Generate Synthetic Traffic2000In: Conference Record / IEEE Global Telecommunications ConferenceVolume 1, 2000, 2000, p. 428-433Conference paper (Refereed)
    Abstract [en]

    We model a web client using empirical probability distributions for user clicks and transferred data sizes. By using a heuristic threshold value to distinguish user clicks in a packet trace we get a simple method for analyzing large packet traces in order to get information about user OFF times and amount of data transferred due to a user click. We derive the empirical probability distributions from the analysis of the packet trace. The heuristic is not perfect, but we believe it is good enough to produce a useful web client model. We use the empirical model to implement a web client traffic generator. The characteristics of the generated traffic is very close to the original packet trace, including self-similar properties.

  • 44.
    Abrahamsson, Henrik
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Ahlgren, Bengt
    SICS.
    Alonso, Juan
    Andersson, Anders
    SICS.
    Kreuger, Per
    SICS.
    A Multi Path Routing Algorithm for IP Networks Based on Flow Optimisation2002In: Proceedings of the Third International Workshop on Quality of Future Internet Services / [ed] Burkhard Stiller, Springer Berlin/Heidelberg, 2002, p. 135-144Conference paper (Refereed)
  • 45.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Caching for IPTV distribution with time-shift2013In: 2013 International Conference on Computing, Networking and Communications, ICNC 2013, IEEE , 2013, p. 916-921Conference paper (Refereed)
    Abstract [en]

    Today video and TV distribution dominate Internet traffic and the increasing demand for high-bandwidth multimedia services puts pressure on Internet service providers. In this paper we simulate TV distribution with time-shift and investigate the effect of introducing a local cache close to the viewers. We study what impact TV program popularity, program set size, cache replacement policy and other factors have on the caching efficiency. The simulation results show that introducing a local cache close to the viewers significantly reduces the network load from TV-on-Demand services. By caching 4% of the program volume we can decrease the peak load during prime time by almost 50%. We also show that the TV program type and how program popularity changes over time can have a big influence on cache hit ratios and the resulting link loads

  • 46.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Robust Traffic Engineering using L-balanced Weight-Settings in OSPF/IS-IS2009In: Proceedings of the 2009 6th International Conference on Broadband Communications, Networks and Systems, BROADNETS 2009, 2009Conference paper (Refereed)
    Abstract [en]

    Internet traffic volumes continue to grow at a great rate, now pushed by video and TV distribution in the networks. This brings up the need for traffic engineering mechanisms to better control the traffic. The objective of traffic engineering is to avoid congestion in the network and make good use of available resources by controlling and optimising the routing function. The challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands. Today, the main alternative for intra-domain traffic engineering in IP networks is to use different methods for setting the weights in the routing protocols OSPF and IS-IS. In this paper we revisit the weight setting approach to traffic engineering but with focus on robustness. We propose I-balanced weight settings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level I. This gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic. We present a heuristic search method for finding I-balanced weight settings and show that it works well in real network scenarios

  • 47.
    Abrahamsson, Henrik
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Robust Traffic Engineering using L-balanced Weight-Settings in OSPF/IS-IS2008Other (Other academic)
  • 48.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Simulation of IPTV caching strategies2010In: Proceedings of the 2010 International Symposium on Performance Evaluation of Computer and Telecommunication Systems, 2010, p. 187-193Conference paper (Refereed)
    Abstract [en]

    IPTV, where television is distributed over the Internet Protocol in a single operator network, has become popular and widespread. Many telecom and broadband companies have become TV providers and distribute TV channels using multicast over their backbone networks. IPTV also means an evolution to time-shifted television where viewers now often can choose to watch the programs at any time. However, distributing individual TV streams to each viewer requires a lot of bandwidth and is a big challenge for TV operators. In this paper we present an empirical IPTV workload model, simulate IPTV distribution with time-shift, and show that local caching can limit the bandwidth requirements significantly.

  • 49.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Gunnar, Anders
    Swedish Institute of Computer Science, Kista, Sweden.
    Traffic Engineering in Ambient Networks: Challenges and Approaches2004Conference paper (Refereed)
  • 50.
    Abrahamsson, Henrik
    et al.
    SICS AB, Kista, Sweden .
    Hagsand, Olof
    Dynarc AB, Kista, Sweden .
    Marsh, Ian
    SICS AB, Kista, Sweden .
    TCP over High Speed Variable Capacity Links: A Simulation Study for Bandwidth Allocation2002In: Protocols for High Speed Networks Workshop, 2002, p. 117-129Conference paper (Refereed)
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