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  • 151.
    Axelsson, Jakob
    et al.
    Swedish Institute of Computer Science, SICS, Sweden.
    Franke, Ulrik
    Swedish Institute of Computer Science, SICS, Sweden.
    Carlson, Jan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Sentilles, Séverine
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Cicchetti, Antonio
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Towards the Architecture of a Decision Support Ecosystem for System Component Selection2017Ingår i: 11th Annual IEEE International Systems conference SysCon17, 2017, s. 371-377Konferensbidrag (Refereegranskat)
    Abstract [en]

    When developing complex software-intensive systems, it is nowadays common practice to base the solution partly on existing software components. Selecting which components to use becomes a critical decision in development, but it is currently not well supported through methods and tools. This paper discusses how a decision support system for this problem could benefit from a software ecosystem approach, where participants share knowledge across organizations both through reuse of analysis models, and through partially disclosed past decision cases. It is shown how the architecture of this ecosystem becomes fundamental to deal with efficient knowledge sharing, while respecting constraints on integrity of intellectual property. A concrete proposal for an architecture is outlined, which is a distributed system-of-systems using web technologies. Experiences of a proof-of-concept implementation are also described.

  • 152.
    Axelsson, Jakob
    et al.
    Swedish Institute of Computer Science (SICS), Sweden.
    Kobetski, Avenir
    Swedish Institute of Computer Science (SICS), Sweden.
    Architectural Concepts for Federated Embedded Systems2014Ingår i: ACM International Conference Proceeding Series, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Federated embedded systems (FES) is an approach for systems-of-systems engineering in the domain of cyber-physical systems. It is based on the idea to allow dynamic addition of plug-in software in the embedded system of a product, and through communication between the plug-ins in different products, it becomes possible to build services on the level of a federation of products. In this paper, architectural concerns for FES are elicited, and are used as rationale for a number of decisions in the architecture of products that are enabled for FES, as well as in the application architecture of a federation. A concrete implementation of a FES from the automotive domain is also described, as a validation of the architectural concepts presented.

  • 153.
    Axelsson, Jakob
    et al.
    Swedish Institute of Computer Science (SICS) Kista, Sweden .
    Kobetski, Avenir
    Swedish Institute of Computer Science (SICS) Kista, Sweden .
    Ni, Ze
    Swedish Institute of Computer Science (SICS) Kista, Sweden .
    Zhang, Shuzhou
    Swedish Institute of Computer Science (SICS) Kista, Sweden .
    Johansson, Eilert
    Swedish Institute of Computer Science (SICS) Kista, Sweden .
    MOPED: A Mobile Open Platform for Experimental Design of Cyber-Physical Systems2014Ingår i: The 40th Euromicro Conference on Software Engineering and Advanced Applications SEAA 2014, 2014, s. 423-430Konferensbidrag (Refereegranskat)
    Abstract [en]

    Due to the increasing importance of cyber-physical and embedded systems in industry, there is a strong demand for engineers with an updated knowledge on contemporary technology and methods in the area. This is a challenge for educators, in particular when it comes to creating hands-on experiences of real systems, due to their complexity and the fact that they are usually proprietary. Therefore, a laboratory environment that is representative of the industrial solutions is needed, with a focus on software and systems engineering issues. This paper describes such an environment, called the Mobile Open Platform for Experimental Design (MOPED). It consists of a model car chassis, equipped with a network of three control units based on standard hardware, and running the automotive software standard AUTOSAR, which consists of operating system, middleware, and application software structures. It is equipped with various sensors and actuators, and is open to extensions both in hardware and software. It also contains elements of future systems, since it allows connectivity to cloud services, development of federated embedded systems, and continuous deployment of new functionality. In this way, the platform provides a very relevant learning environment for cyber-physical systems, today and in the future.

  • 154.
    Axelsson, Jakob
    et al.
    RISE SICS AB, Kista, Sweden.
    Nylander, Stina
    RISE SICS AB, Kista, Sweden.
    An Analysis of Systems-of-Systems Opportunities and Challenges Related to Mobility in Smart Cities2018Ingår i: System of Systems Engineering Conference SoSE 2018, 2018, s. 132-137Konferensbidrag (Refereegranskat)
    Abstract [en]

    Urbanization is one of the major current trends in society. Cities around the world are looking into 'smart'  solutions based on information and communication technology to deal with the challenges that result from this development. Mobility is one of the most important areas to address, and system-of-systems solutions where vehicles and infrastructure are connected have a potential to improve urban transportation in many aspects. In this paper, current initiatives related to mobility in smart cities around the world are surveyed, and this is complemented with input from focus groups of transportation stakeholders to identify the important aspects of the problem. Based on this, challenges related to the application of systems-of-systems in urban mobility are identified.

  • 155.
    Axelsson, Jakob
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Papatheocharous, E.
    Swedish Institute of Computer Science (SICS), Sweden.
    Andersson, J.
    Linneaus University, Sweden.
    Characteristics of software ecosystems for Federated Embedded Systems: A case study2014Ingår i: Information and Software Technology, ISSN 0950-5849, E-ISSN 1873-6025, Vol. 56, nr 11, s. 1457-1475Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Context Traditionally, Embedded Systems (ES) are tightly linked to physical products, and closed both for communication to the surrounding world and to additions or modifications by third parties. New technical solutions are however emerging that allow addition of plug-in software, as well as external communication for both software installation and data exchange. These mechanisms in combination will allow for the construction of Federated Embedded Systems (FES). Expected benefits include the possibility of third-party actors developing add-on functionality; a shorter time to market for new functions; and the ability to upgrade existing products in the field. This will however require not only new technical solutions, but also a transformation of the software ecosystems for ES. Objective This paper aims at providing an initial characterization of the mechanisms that need to be present to make a FES ecosystem successful. This includes identification of the actors, the possible business models, the effects on product development processes, methods and tools, as well as on the product architecture. Method The research was carried out as an explorative case study based on interviews with 15 senior staff members at 9 companies related to ES that represent different roles in a future ecosystem for FES. The interview data was analyzed and the findings were mapped according to the Business Model Canvas (BMC). Results The findings from the study describe the main characteristics of a FES ecosystem, and identify the challenges for future research and practice. Conclusions The case study indicates that new actors exist in the FES ecosystem compared to a traditional supply chain, and that their roles and relations are redefined. The business models include new revenue streams and services, but also create the need for trade-offs between, e.g., openness and dependability in the architecture, as well as new ways of working. © 2014 The Authors. Published by Elsevier B.V.

  • 156.
    Axelsson, Jakob
    et al.
    SICS Swedish ICT, Sweden.
    Papatheocharous, Efi
    SICS Swedish ICT, Sweden.
    Nyfjord, Jaana
    SICS Swedish ICT, Sweden.
    Törngren, Martin
    KTH Royal Institute of Technology, Sweden.
    Notes On Agile and Safety-Critical Development2016Ingår i: Software Engineering Notes: an Informal Newsletter of The Specia, ISSN 0163-5948, E-ISSN 1943-5843, Vol. 41, nr 2, s. 23-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Agile approaches have been highly influential to the software engineering practices in many organizations, and are increasingly being applied in larger companies, and for developing systems outside the pure software domain. To understand more about the current state of agile, its applications to safety-critical systems, and the consequences on innovation and large organizations, a seminar was organized in Stockholm in 2014. This paper gives an overview of the topics discussed at that seminar, a summary of the main results and suggestions for future work as input to a research agenda for agile development of safety-critical software.

  • 157.
    Ayala, Inmaculada
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Gallina, Barbara
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Towards Tool-based Security-informed Safety Oriented Process Line Engineering2016Ingår i: 1st International workshop on Interplay of Security, Safety and System/Software Architecture ISSA-2016, 2016, artikel-id 38Konferensbidrag (Refereegranskat)
    Abstract [en]

    For the purpose of certification, manufactures of nowadays highly connected safety-critical systems are expected to en- gineer their systems according to well-defined engineering processes in compliance with safety and security standards. Certification is an extremely expensive and time-consuming process. Since safety and security standards exhibit a certain degree of commonality, certification-related artifacts (e.g., process models) should to some extent be reusable. To en- able systematic reuse and customization of process infor- mation, in this paper we further develop security-informed safety-oriented process line engineering (i.e., engineering of sets of processes including security and safety concerns). More specifically, first we consider three tool-supported ap- proaches for process-related commonality and variability man- agement and we apply them to limited but meaningful por- tions of safety and security standards within airworthiness. Then, we discuss our findings. Finally, we draw our conclu- sions and sketch future work.

  • 158.
    Ayoub, Ayoub
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Berg, Carl Martin
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Design of a Dynamic Boom Suspension System in a Hybrid Wheel Loader2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Wheel loaders are under the influence of low frequency vibrations that may be harmful for the health of the operator, and for the productivity of the machine. The strong vibrations can significantly impact the operation of the machine since they are not equipped with wheel suspension systems and due to their work environment in rough terrains with uneven surfaces. The risk of spilling or dropping the load is also increased and they can introduce higher mechanical stress that can wear out parts faster. The focus of this thesis work is to develop an approach for damping these vibrations dynamically by improving the functionality of the electrohydraulic system in Volvo's prototype wheel loader LX1. The dynamic damping system controls the cylinder of the lift framework to make it behave as a damper. The system utilizes the lift cylinder pressure and piston position as feedback to adjust the oil flow in the cylinder using the proposed control system. Results indicate that the proposed technique is capable of attenuation that is comparable with the existing boom suspension system based on accumulators through simulations and experimental tests.

  • 159.
    Aysan, Huseyin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Dobrin, Radu
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Punnekkat, Susikumar
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Schedulability guarantees for dependable distributed real-time systems under error bursts2013Ingår i: Advances in Intelligent Systems and Computing, Springer Verlag , 2013, Vol. 187, s. 393-406Konferensbidrag (Refereegranskat)
    Abstract [en]

    In dependable embedded real-time systems, typically built of computing nodes exchanging messages over reliability-constrained networks, the provision of schedulability guarantees for task and message sets under realistic fault and error assumptions is an essential requirement, though complex and tricky to achieve. An important factor to be considered in this context is the random nature of occurrences of faults and errors, which, if addressed in the traditional schedulability analysis by assuming a rigid worst-case occurrence scenario, may lead to inaccurate results. In this work we propose a framework for end-to-end probabilistic schedulability analysis for real-time tasks exchanging messages over Controller Area Network under stochastic errors.

  • 160.
    Aysan, Hüseyin
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Fault-Tolerance Strategies and Probabilistic Guarantees for Real-Time Systems2012Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Ubiquitous deployment of embedded systems is having a substantial impact on our society, since they interact with our lives in many critical real-time applications. Typically, embedded systems used in safety or mission critical applications (e.g., aerospace, avionics, automotive or nuclear domains) work in harsh environments where they are exposed to frequent transient faults such as power supply jitter, network noise and radiation. They are also susceptible to errors originating from design and production faults. Hence, they have the design objective to maintain the properties of timeliness and functional correctness even under error occurrences.

    Fault-tolerance plays a crucial role towards achieving dependability, and the fundamental requirement for the design of effective and efficient fault-tolerance mechanisms is a realistic and applicable model of potential faults and their manifestations. An important factor to be considered in this context is the random nature of faults and errors, which, if addressed in the timing analysis by assuming a rigid worst-case occurrence scenario, may lead to inaccurate results. It is also important that the power, weight, space and cost constraints of embedded systems are addressed by efficiently using the available resources for fault-tolerance.

    This thesis presents a framework for designing predictably dependable embedded real-time systems by jointly addressing the timeliness and the reliability properties. It proposes a spectrum of fault-tolerance strategies particularly targeting embedded real-time systems. Efficient resource usage is attained by considering the diverse criticality levels of the systems' building blocks. The fault-tolerance strategies are complemented with the proposed probabilistic schedulability analysis techniques, which are based on a comprehensive stochastic fault and error model.

  • 161.
    Aysan, Hüseyin
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Dobrin, Radu
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Punnekkat, Sasikumar
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    A Generalized Task Allocation Framework for Dependable Real-Time Systems2007Ingår i: Proceedings of the Work-In-Progress (WIP) session of the 19th Euromicro Conference on Real-Time Systems (ECRTS 07), 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we present a general framework which allows the designer to specify a wide range of criteria for allocation. Major factors considered as part of our framework are mixed criticalities of tasks, schedulability, power consumption, fault-tolerance, and dependability requirements in addition to typical functional aspects such as memory constraints. This being a global optimization problem, we are forced to use meta-heuristic algorithms, and we were able to represent these requirements in a very intuitive manner by the usage of energy functions in simulated annealing. We envision the proposed methodology as a quite simple, scalable, as well as computationally effective solution covering a wide range of system architectures and solution spaces. 

  • 162.
    Aysan, Hüseyin
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Dobrin, Radu
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Punnekkat, Sasikumar
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    FT-Feasibility in Fixed Priority Real-Time Scheduling2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    Real-time systems typically have to satisfy complex requirements mapped to the timing attributes of the tasks that are eventually guaranteed by the underlying scheduler. These systems consist of a mix of hard and soft tasks with varying criticalities as well as associated fault tolerance (FT) requirements. Often time redundancy techniques are preferred in many embedded applications and hence it is extremely important to devise appropriate methodologies for scheduling real-time tasks under fault assumptions. Additionally, the relative criticality of tasks could undergo changes during the evolution of the system. Hence scheduling decisions under fault assumptions have to reflect all these important factors in addition to the resource constraints.

    In this paper we propose a framework for 'FTfeasibility', i.e., to provide a priori guarantees that all critical tasks in the system will meet their deadlines even in case of faults. Our main objective here is to ensure FTfeasibility of all critical tasks in the system and do so with minimal costs and without any fundamental changes in the scheduling paradigm. We demonstrate its applicability in scenarios where the FT strategy employed is re-execution of the affected tasks or an alternate action upon occurrence of transient faults or software design faults. We analyse a feasible set of tasks and propose methods to adapt it to varying FT requirements without modifications to the underlying scheduler. We do so by reassigning task attributes to achieve FT-feasibility while keeping the costs minimised.

  • 163.
    Aysan, Hüseyin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Punnekkat, Sasikumar
    Mälardalens högskola, Akademin för innovation, design och teknik.
    A Generalised Error Model and Schedulability Guarantees for Dependable Real-Time Systems2011Ingår i: Proceedings of the 1st International Workshop on Dependable and Secure Industrial and Embedded Systems (WORDS), 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The fundamental requirement for the design of effective and efficient fault-tolerance mechanisms in dependable real-time systems is a realistic and applicable model of potential faults, their manifestations and consequences. Fault and error models also need to be evolved based on the changes in the environments of usage or even based on technological advances. In this paper we propose a novel probabilistic burst error model in lieu of the commonly used simplistic fault assumptions. We introduce an approach to reason about real-time systems schedulability under the proposed error model in a probabilistic manner. We first present a sufficient analysis that accounts for the worst case interference caused by error bursts on the response times of tasks scheduled under the fixed priority scheduling (FPS) policy. Further, we identify potential sources of pessimism in the calculations and propose an algorithm that refines the results.

  • 164.
    Azhar, Muhammad
    Mälardalens högskola, Akademin för innovation, design och teknik.
    A Stochastic Analysis Framework for Real-Time Systems under Preemptive Priority-Driven Scheduling2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis work describes how to apply the stochastic analysis framework, presented in [1] for general priority-driven periodic real-time systems. The proposed framework is applicable to compute the response time distribution, the worst-case response time, and the deadline miss probability of the task under analysis in the fixed-priority driven scheduling system. To be specific, we modeled the task execution time by using the beta distribution. Moreover, we have evaluated the existing stochastic framework on a wide range of periodic systems with the help of defined evaluation parameters.

    In addition we have refined the notations used in system model and also developed new mathematics in order to facilitate the understanding with the concept. We have also introduced new concepts to obtain and validate the exact probabilistic task response time distribution.   

    Another contribution of this thesis is that we have extended the existing system model in order to deal with stochastic release time of a job. Moreover, a new algorithm is developed and validated using our extended framework where the stochastic dependencies exist due to stochastic release time patterns.

  • 165.
    Azimoh, Chukwuma Leonard
    Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, Framtidens energi.
    Sustainability and development impacts of off-grid electrification in developing countries: An assessment of South Africa's rural electrification program2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Previous studies have shown that provision of sustainable electricity supply to rural households is essential to bring development to off-grid populations. For this reason, most developing countries put large efforts into rural electrification programs to stimulate development and reduce poverty. However, to be sustainable these programs need to recover costs, which poses a challenge to remote low income populations.  This often forces governments and other institutions involved in rural electrification to subsidize the electricity production. It also affects the choice of technology and places a barrier on the level of energy provided in line with the ability to pay for services. As a result of this, most programs have failed to achieve the desired objectives, as the technologies used often do not support income generating activities that could increase the payment capabilities of the beneficiaries and contribute to development.

    This thesis is focused on the rural electrification program of South Africa, the country in sub-Saharan Africa that has the highest access to electricity. It investigates the success elements that influence the sustainability of rural electrification programs and their contributions to socio-economic development. This was achieved by evaluating the South African program that provides solar home systems to off-grid communities, and a hybrid solar-wind mini-grid project in South Africa. The study also draw lessons from other rural electrification programs in neighbouring countries, i.e. an evaluation of a hybrid solar-diesel mini-grid system in Namibia, and a review of two systems, a hybrid solar-biomass mini-grid project in Botswana and a hydro mini-grid program in Lesotho. The study revealed that hydro based hybrid mini-grid systems provide the most cost effective way of bringing energy services to rural settlements. Regardless of technology, successful programs depend on adequate support from the government, implementation of a progressive tariff system that allows the high consuming high income earners and businesses, to cross subsidize the low consuming , low income users. It shows that it is more likely for rural electrification programs to survive if the design considers the existing businesses, population growth and the corresponding load increase. The thesis further shows that provision of sufficient energy to induce income generating activities is essential to decrease the need for subsidies and to ensure the sustainability of programs. In addition, availability of spare parts and a capable management team is essential for the successful operations and maintenance of these systems.

  • 166.
    Back, Ralph-Johan
    et al.
    Turku Centre for Computer Science .
    Cerschi (Seceleanu), Cristina
    Turku Centre for Computer Science .
    Modeling and Verifying a Temperature Control System using Continuous Action Systems2000Konferensbidrag (Refereegranskat)
    Abstract [en]

    We formally describe and verify a real-time temperature control system for a nuclear reactor tank, using a generalization of action systems to hybrid systems (based on weakest precondition predicate transformer semantics) as our formal framework. The analyzed control system is a linear hybrid system, combining discrete control with continuous dynamics. Our work can be seen as a case study on the applicability of the hybrid action system formalism to study the reachability problem, i.e., to prove that an unsafe state can not be reached by executing the system.

  • 167.
    Back, Ralph-Johan
    et al.
    Turku Centre for Computer Science, Finland.
    Seceleanu, Cristina
    Turku Centre for Computer Science, Finland.
    Westerholm, Jan
    Turku Centre for Computer Science, Finland.
    Symbolic Simulation of Hybrid Systems2002Konferensbidrag (Refereegranskat)
    Abstract [en]

    Continuous action systems (CAS) is a formalism intended for modeling hybrid systems (systems that combine discrete control with continuous behavior), and proving properties about the model within refinement calculus. In this paper we use a symbolic manipulation program to build a tool for simulating CAS models by calculating symbolically the time evolution of the discrete and continuous CAS model functions, as explicit and exact expressions of a continuous time variable. We may then study the time behavior and general properties of the model by plotting these functions with respect to time. For certain models our tool eliminates the need for introducing tolerances into the model structure. The tool is useful for checking that the model behaves correctly, and we can sometimes study the behavior of CAS models with in principle infinite precision.

  • 168.
    Bagheri, M.
    et al.
    Sharif University of Technology, Tehran, Iran.
    Khamespanah, E.
    Sharif University of Technology, Tehran, Iran.
    Sirjani, Marjan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Reykjavik University, Reykjavik, Iceland.
    Movaghar, A.
    Sharif University of Technology, Tehran, Iran.
    Lee, A. E.
    University of California at Berkeley.
    Runtime compositional analysis of track-based traffic control systems2017Ingår i: ACM SIGBED Review, ISSN 1551-3688, Vol. 14, nr 3, s. 38-39Artikel i tidskrift (Refereegranskat)
  • 169.
    Bagheri, M.
    et al.
    Sharif University of Technology, Tehran, Iran.
    Sirjani, Marjan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Reykjavik University, Reykjavik, Iceland.
    Khamespanah, E.
    Reykjavik University, Reykjavik, Iceland.
    Khakpour, N.
    Linnaeus University, Växjö Campus, Sweden.
    Akkaya, I.
    University of California at Berkeley, CA, United States.
    Movaghar, A.
    Sharif University of Technology, Tehran, Iran.
    Lee, E. A.
    University of California at Berkeley, CA, United States.
    Coordinated actor model of self-adaptive track-based traffic control systems2018Ingår i: Journal of Systems and Software, ISSN 0164-1212, E-ISSN 1873-1228, Vol. 143, s. 116-139Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Self-adaptation is a well-known technique to handle growing complexities of software systems, where a system autonomously adapts itself in response to changes in a dynamic and unpredictable environment. With the increasing need for developing self-adaptive systems, providing a model and an implementation platform to facilitate integration of adaptation mechanisms into the systems and assuring their safety and quality is crucial. In this paper, we target Track-based Traffic Control Systems (TTCSs) in which the traffic flows through pre-specified sub-tracks and is coordinated by a traffic controller. We introduce a coordinated actor model to design self-adaptive TTCSs and provide a general mapping between various TTCSs and the coordinated actor model. The coordinated actor model is extended to build large-scale self-adaptive TTCSs in a decentralized setting. We also discuss the benefits of using Ptolemy II as a framework for model-based development of large-scale self-adaptive systems that supports designing multiple hierarchical MAPE-K feedback loops interacting with each other. We propose a template based on the coordinated actor model to design a self-adaptive TTCS in Ptolemy II that can be instantiated for various TTCSs. We enhance the proposed template with a predictive adaptation feature. We illustrate applicability of the coordinated actor model and consequently the proposed template by designing two real-life case studies in the domains of air traffic control systems and railway traffic control systems in Ptolemy II. 

  • 170.
    Bagheri, Maryam
    et al.
    Sharif University of Technology, Iran.
    Akkaya, Ilge
    University of California at Berkley, US.
    Khamespanah, Ehsan
    Reykjavik University, Iceland.
    Khakpour, Narges
    Linnaeus University, Sweden.
    Sirjani, Marjan
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Movaghar, Ali
    Sharif University of Technology, Iran.
    Lee, Edward
    University of California at Berkley, US.
    Coordinated Actors for Reliable Self-Adaptive Systems2017Ingår i: The 13th International Conference on Formal Aspects of Component Software FACS 2016, 2017, Vol. 10231, s. 241-259Konferensbidrag (Refereegranskat)
    Abstract [en]

    Self-adaptive systems are systems that automatically adapt in response to environmental and internal changes, such as possible failures and variations in resource availability. Such systems are often realized by a MAPE-K feedback loop, where Monitor, Analyze, Plan and Execute components have access to a runtime model of the system and environment which is kept in the Knowledge component. In order to provide guarantees on the correctness of a self-adaptive system at runtime, the MAPE-K feedback loop needs to be extended with assurance techniques. To address this issue, we propose a coordinated actor-based approach to build a reusable and scalable model@runtime for self-adaptive systems in the domain of track-based traffic control systems. We demonstrate the approach by implementing an automated Air Traffic Control system (ATC) using Ptolemy tool.We compare different adaptation policies on the ATC model based on performance metrics and analyze combination of policies in different configurations of the model. We enriched our framework with runtime performance analysis such that for any unexpected change, subsequent behavior of the model is predicted and results are used for adaptation at the change-point. Moreover, the developed framework enables checking safety properties at runtime.

  • 171.
    Baig, Aftab
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Ahmad, Iftikhar
    Mälardalens högskola, Akademin för innovation, design och teknik.
    A web store based on reusable .NET components2011Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The thesis project describes  the analysis, process and major factors in development of a simple component oriented Web Shop in ASP.NET. It addresses to the concepts used in  the application as  well  as  derivation  of  technical  design  and  development  from  the  concepts  acquired  by studying existing approaches.

    The report  describes  a  brief  summary of  existing  approaches  and related  technologies.  It also lays  the foundation  of  goal  oriented  approach  by  providing  an  overview  of  component  based  software engineering. The  basic  concepts for modularization  were  barrowed from  entities  identification,  object models and component models pplication’s architecture is set to be a layered app roach combining the software layered  architecture  approach  with  multi  tier  architecture  of  web  applications. Class models explaining the inner structure of each component have been provided and an overview of user interface pages is given to explain the application outer flow. The application sets out to prove the significance of component oriented approach as well as  the  support  provided for it by ASP.Net. The resulting package proves  to  have  scalable  components  that could be scaled for  or  reused in another  application or  in  a later version of the same application. 

  • 172.
    Bakhshi Valojerdi, Zeinab
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Balador, Ali
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    An Overview on Security and Privacy Challenges and TheirSolutions in Fog-Based Vehicular Application2019Ingår i: An Overview on Security and Privacy Challenges and TheirSolutions in Fog-Based Vehicular Application, Istanbul, 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fog computing is an emerging computing paradigm that extends cloud services to the edge of the network by moving computation tasks from cloud to network edges to reduce response latency in a wireless network. Fog computing inherits the principle of peer-to-peer networking, decentralization, and geographical distribution from clouds. Hence, fog computing becomes an ideal platform for readily supporting vehicular applications due to its dynamic support for mobility of client-devices and low latent heterogeneous communication capabilities. Despite many advantages, a multitude of security and privacy issues affects the platforms and renders it as a target for unknown adversaries. This has significant implication in the development of safety critical applications, such as vehicular cloud and intelligent transportation system. This paper presents, an overview of existing security and privacy vulnerabilities in fog computing, particularly in vehicular networks. Moreover, state-of-the-art security and privacy solutions for fog based vehicular networks are analyzed. In conclusion, open challenges and future research directions are discussed.

  • 173.
    Bakhshi Valojerdi, Zeinab
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Rodriguez-Navas, Guillermo
    Nokia Bell Labs, Israel.
    A Preliminary Roadmap for Dependability Research in Fog Computing2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Fog computing aims to support novel real-time applications byextending cloud resources to the network edge. This technologyis highly heterogeneous and comprises a wide variety of devicesinterconnected through the so-called fog layer. Compared to tra-ditional cloud infrastructure, fog presents more varied reliabilitychallenges, due to its constrained resources and mobility of nodes.This paper summarizes current research efforts on fault toleranceand dependability in fog computing and identifies less investigatedopen problems, which constitute interesting research directions tomake fogs more dependable.

  • 174.
    Bakhshi Valojerdi, Zeinab
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Rodriguez-Navas, Guillermo
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Hansson, Hans
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Dependable Fog Computing: A Systematic Literature Review2019Konferensbidrag (Refereegranskat)
    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.

  • 175.
    Bakhshi, Zeynab
    et al.
    RighTel, Iran.
    Balador, Ali
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. RISE SICS, Västerås, Sweden.
    Mustafa, Jawad
    RISE SICS, Västerås, Sweden.
    Industrial IoT Security Threats and Concerns by Considering CISCO and Microsoft IoT reference Models2018Ingår i: IEEE WCNCW 2018 IEEE WCNCW 2018: 2018 IEEE Wireless Communications and Networking Conference Workshops, 2018, s. 173-178Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper investigates security concerns and issues for Industrial Internet of Things (IIoT). The IIoT is an emerging transformation, bringing great values to every industry. Although this rapid alter in industries create values, but there are concerns about security issues, most of which would be still unknown due to the novelty of this platform. In order to provide a guideline for those who want to investigate IoT security and contribute to its improvement, this paper attempts to provide a list of security threats and issues on the cloud-side layer of IoT, which consists of data accumulation and abstraction levels. For this reason, we choose Cisco and Microsoft Azure IoT Architecture as reference models. Then, two layers of Cisco reference architecture model have been chosen to be investigated for their security issues. Finally, consideration of security issues has been briefly explained.

  • 176.
    Balador, Ali
    SICS Swedish ICT Västerås AB, Sweden.
    A Token-Based MAC Protocol for Achieving High Reliability in VANET2016Ingår i: BMW Summer School 2016 BMWSS 2016, Bad Wörishofen, Bavaria, Germany, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Safety applications developed for vehicular environments require every vehicle to periodically broadcast its status information (beacon) to all other vehicles, thereby avoiding the risk of car accidents in the road. Due to the high requirements on timing and reliability posed by traffic safety applications, the current IEEE 802.11p standard, which uses a random access Medium Access Control (MAC) protocol, faces difficulties to support timely and reliable data dissemination in vehicular environments where no acknowledgement or RTS/CTS (Request-to-Send/Clear-to-Send) mechanisms are adopted. In this paper, we propose the Dynamic Token-Based MAC (DTB-MAC) protocol. It implements a token passing approach on top of a random access MAC protocol to prevent channel contention as much as possible, thereby improving the reliability of safety message transmissions. Our proposed protocol selects one of the neighbouring nodes as the next transmitter; this selection accounts for the need to avoid beacon lifetime expiration. Therefore, it automatically offers retransmission opportunities to allow vehicles to successfully transmit their beacons before the next beacon is generated whenever time and bandwidth are available. Based on simulation experiments, we show that the DTB-MAC protocol can achieve better performance than IEEE 802.11p in terms of channel utilization and beacon delivery ratio for urban scenarios.

  • 177.
    Balador, Ali
    et al.
    SICS Swedish ICT Västerås AB, Sweden.
    Böhm, Annette
    Halmstad University, Sweden.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    A Reliable Token-Based MAC Protocol for V2V Communication in Urban VANET2016Ingår i: IEEE International Symposium on Personal, Indoor and Mobile Radio Communications PIMRC 16, Valencia, Spain, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Safety applications developed for vehicular environments require every vehicle to periodically broadcast its status information (beacon) to all other vehicles, thereby avoiding the risk of car accidents in the road. Due to the high requirements on timing and reliability posed by traffic safety applications, the current IEEE 802.11p standard, which uses a random access Medium Access Control (MAC) protocol, faces difficulties to support timely and reliable data dissemination in vehicular environments where no acknowledgement or RTS/CTS (Request-to-Send/Clear-to-Send) mechanisms are adopted. In this paper, we propose the Dynamic Token-Based MAC (DTB-MAC) protocol. It implements a token passing approach on top of a random access MAC protocol to prevent channel contention as much as possible, thereby improving the reliability of safety message transmissions. Our proposed protocol selects one of the neighbouring nodes as the next transmitter; this selection accounts for the need to avoid beacon lifetime expiration. Therefore, it automatically offers retransmission opportunities to allow vehicles to successfully transmit their beacons before the next beacon is generated whenever time and bandwidth are available. Based on simulation experiments, we show that the DTB-MAC protocol can achieve better performance than IEEE 802.11p in terms of channel utilization and beacon delivery ratio for urban scenarios.

  • 178.
    Balador, Ali
    et al.
    SICS Swedish ICT Västerås AB, Sweden.
    Böhm, Annette
    Halmstad University, Sweden.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    A Reliable and Efficient Token-Based MAC Protocol for Platooning Applications2016Ingår i: 12th Swedish National Computer Networking Workshop SNCNW 2016, 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    Platooning is both a challenging and rewarding application. Challenging since strict timing and reliability requirements are imposed by the distributed control system required to operate the platoon. Rewarding since considerable fuel reductions are possible. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However, TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if retransmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability compared to pure 802.11p.

  • 179.
    Balador, Ali
    et al.
    Polytechnic University of Valencia, Valencia, Spain.
    Böhm, Annette
    Halmstad Universit, Sweden.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Calafate, Carlos T.
    Polytechnic University of Valencia, Valencia, Spain.
    Ji, Yusheng
    National Institute of Informatics, Tokyo, Japan.
    Cano, Juan-Carlos
    Polytechnic University of Valencia, Valencia, Spain.
    Manzoni, Pietro
    Polytechnic University of Valencia, Valencia, Spain.
    An Efficient MAC Protocol for vehicle platooning in automated highway systems2015Ingår i: Jornadas Sarteco 2015 JS 2015, Cordoba, Spain, 2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Lately, all the top truck manufacturers are investing considerable resources in the research and development of platooning systems which would allow vehicles to save fuel and improve safety by travelling in a close-following manner. The platoon-ing system requires frequent and reliable vehicle-to-vehicle communications. As platooning takes place in a vehicular ad hoc network, the use of IEEE 802.11p is close to mandatory. However, the 802.11p medium access method suffers from packet collisions and random delays. Most ongoing research suggests using TDMA on top of 802.11p as a potential remedy. However , TDMA requires synchronization and is not very flexible if the beacon frequency needs to be updated, the number of platoon members changes, or if re-transmissions for increased reliability are required. We therefore suggest a token-passing medium access method where the next token holder is selected based on beacon data age. This has the advantage of allowing beacons to be re-broadcasted in each beacon interval whenever time and bandwidth are available. We show that our token-based method is able to reduce the data age and considerably increase reliability considerably compared to pure 802.11p.

  • 180.
    Balador, Ali
    et al.
    Universitat Politecnica de Valencia, Spain.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    Manzoni, Pietro
    Universitat Politecnica de Valencia, Spain.
    A Density-Based Contention Window Control Scheme for Unicast Communications in Vehicular Ad Hoc Networks2015Ingår i: International Journal of Ad Hoc and Ubiquitous Computing, ISSN 1743-8225, E-ISSN 1743-8233, Vol. 24, s. 65-75Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Achieving a well-designed medium access control MAC protocol is a challenging issue to improve communications efficiency due to the dynamic nature of vehicular ad hoc networks VANETs. IEEE 802.11p standard was selected as the best choice for vehicular environments considering its availability, maturity, and cost. The common problem in all IEEE 802.11 based protocols is scalability, exhibiting performance degradation in highly variable network scenarios. Experimental results for the IEEE 802.11-based MAC protocol show the importance of contention window adjustment on communications performance; however the vehicular communications community has not yet addressed this issue in unicast communication environments. This paper proposes a novel contention window control scheme for VANET environments based on estimating the network density, which is then used to dynamically adapt the CW size. Analysis and simulation results show that our proposal provides better overall performance compared with previous proposals, even in high network density scenarios.

  • 181. Balador, Ali
    et al.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    Manzoni, Pietro
    Universitat Politecnica de Valencia, Spain.
    A Novel 802.11 Contention Window Control Scheme for Vehicular Environments2013Ingår i: Jornadas Sarteco 2013 JS 2013, 2013, s. 98-103Konferensbidrag (Refereegranskat)
    Abstract [en]

    Intelligent Transportation Systems (ITS) have attractive potential in order to decrease the ordi- nary traffic jams and avoid transportation disasters. Also, they are able to provide various infotainment services like browsing, reading e-mail or using social networks that makes a trip more interesting. In or- der to make it more efficient in real vehicular envi- ronments, achieving a well-designed Medium Access Control (MAC) protocol is a challenging issue due to the dynamic nature of VANETs, scalability issues, and the variety of application requirements. Differ- ent standardization organizations have selected IEEE 802.11 as the first choice for VANET environments considering its availability, maturity, and cost. The research results for IEEE 802.11 MAC protocol show the importance of contention window adjustment on the communications performance. The impact of ad- justing the contention window has been studied in MANETs, but the vehicular communication commu- nity has not yet addressed this issue thoroughly. This paper proposes e-HBCWC, a new contention window control scheme for VANET environments based on estimating the network condition. Analy- sis and simulation results using OMNeT++ in urban scenarios show that e-HBCWC clearly outperforms 802.11 DCF, even in very high network density, by increasing the packet delivery rate while decreasing the number of collisions and the end-to-end delay for unicast applications.

  • 182.
    Balador, Ali
    et al.
    Universitat Politecnica de Valencia, Spain.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    Manzoni, Pietro
    Universitat Politecnica de Valencia, Spain.
    Congestion Control for Vehicular Environments by Adjusting IEEE 802.11 Contention Window Size2013Ingår i: 13th International Conference on Algorithms and Architectures for Parallel Processing ICA3PP-2013, 2013, s. 259-266Konferensbidrag (Refereegranskat)
    Abstract [en]

    Medium access control protocols should manage the highly dynamic nature of Vehicular Ad Hoc Networks (VANETs) and the variety of application requirements. Therefore, achieving a well-designed MAC protocol in VANETs is a challenging issue. The contention window is a critical element for handling medium access collisions in IEEE 802.11, and it highly affects the communications performance. This paper proposes a new contention window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in urban scenarios show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.

  • 183.
    Balador, Ali
    et al.
    Universitat Politecnica de Valencia, Spain.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    Manzoni, Pietro
    Universitat Politecnica de Valencia, Spain.
    DTB-MAC: Dynamic Token-Based MAC Protocol for Reliable and Efficient Beacon Broadcasting in VANETs2016Ingår i: The 13th Annual IEEE Consumer Communications & Networking Conference CCNC 2016, 2016, s. 109-114Konferensbidrag (Refereegranskat)
    Abstract [en]

    Most applications developed for vehicular environments rely on broadcasting as the main mechanism to disseminate their messages. However, in IEEE 802.11p, which is the most widely accepted Medium Access Control (MAC) protocol for vehicular communications, all transmissions remain unacknowledged if broadcasting is used. Furthermore, safety message transmission requires a strict delay limit and a high reliability, which is an issue for random access MAC protocols like IEEE 802.11p. Therefore, transmission reliability becomes the most important issue for broadcast-based services in vehicular environments. In this paper, we propose a hybrid MAC protocol, referred as Dynamic Token-Based MAC Protocol (DTB-MAC). DTB-MAC uses both a token passing mechanism and a random access MAC protocol to prevent channel contention as much as possible, and to improve the reliability of safety message transmissions. Our proposed protocol tries to select the best neighbouring node as the next transmitter, and when it is not possible, or when it causes a high overhead, the random access MAC protocol is used instead. Based on simulation experiments, we show that the DTB-MAC protocol can achieve better performance compared with IEEE 802.11p in terms of channel utilization and beacon delivery ratio.

  • 184. Balador, Ali
    et al.
    Calafate, Carlos T.
    Universitat Politecnica de Valencia, Spain.
    Cano, Juan-Carlos
    Universitat Politecnica de Valencia, Spain.
    Manzoni, Pietro
    Performance Evaluation of Realistic Vehicular Networks: A MAC Layer Perspective2014Ingår i: Simulation Technologies in Networking and Communications: Selecting the Best Tool for the Test / [ed] Al-Sakib Khan Pathan, Muhammad Mostafa Monowar, Shafiullah Khan, CRC Press, Taylor & Francis Group , 2014Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 185.
    Balador, Ali
    et al.
    Univ. Politec. de Valencia, Valencia, Spain.
    Calafate, Carlos T.
    Univ. Politec. de Valencia, Valencia, Spain.
    Cano, Juan-Carlos
    Univ. Politec. de Valencia, Valencia, Spain.
    Manzoni, Pietro
    Univ. Politec. de Valencia, Valencia, Spain.
    Reducing Channel Contention in Vehicular Environments Through an Adaptive Contention Window Solution2013Ingår i: IFIP Wireless Days WD 2013, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Intelligent Transportation Systems (ITS) are attracting growing attention both in industry and academia due to the advances in wireless communication technologies, and a significant demand for a wide variety of applications targeting this kind of environments are expected. In order to make it usable in real vehicular environments, achieving a well-designed Medium Access Control (MAC) protocol is a challenging issue due to the dynamic nature of Vehicular Ad Hoc Networks (VANETs), scalability issues, and the variety of application requirements. Different standardization organizations have selected IEEE 802.11 as the first choice for VANET environments considering its availability, maturity, and cost. The contention window is a critical parameter for handling medium access collisions by the IEEE 802.11 MAC protocol, and it highly affects the communications performance. The impact of adjusting the contention window has been studied in Mobile Ad-Hoc Networks (MANETs), but the vehicular communications community has not yet addressed this issue thoroughly. This paper proposes a new contention window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in a highway scenario show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.

  • 186.
    Balador, Ali
    et al.
    RISE SICS Västerås, Sweden.
    Ericsson, Niclas
    RISE SICS Västerås, Sweden.
    Bakhshi, Zeynab
    RighTel, Iran.
    Communication Middleware Technologies for Industrial Distributed Control Systems: A Literature Review2018Ingår i: International Conference on Emerging Technologies And Factory Automation ETFA'17, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Industry 4.0 is the German vision for the future of manufacturing, where smart factories use information and communication technologies to digitise their processes to achieve improved quality, lower costs, and increased efficiency. It is likely to bring a massive change to the way control systems function today. Future distributed control systems are expected to have an increased connectivity to the Internet, in order to capitalize on new offers and research findings related to digitalization, such as cloud, big data, and machine learning. A key technology in the realization of distributed control systems is middleware, which is usually described as a reusable software layer between operating system and distributed applications. Various middleware technologies have been proposed to facilitate communication in industrial control systems and hide the heterogeneity amongst the subsystems, such as OPC UA, DDS, and RT-CORBA. These technologies can significantly simplify the system design and integration of devices despite their heterogeneity. However, each of these technologies has its own characteristics that may work better for particular applications. Selection of the best middleware for a specific application is a critical issue for system designers. In this paper, we conduct a survey on available standard middleware technologies, including OPC UA, DDS, and RT-CORBA, and show new trends for different industrial domains.

  • 187.
    Balador, Ali
    et al.
    Islamic Azad University, Tehran, Iran.
    Movaghar, Ali
    Sharif University of Technology, Tehran, Iran.
    Jabbehdari, Sam
    North Tehran Branch, Islamic Azad University, Tehran, Iran.
    History Based Contention Window Control (HBCWC) in IEEE 802.11 Mac Protocol in Error Prone Channel2010Ingår i: Journal of Computer Science, ISSN 1549-3636, E-ISSN 1552-6607, Vol. 6, nr 2, s. 205-209Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Problem statement: IEEE 802.11 Medium Access Control (MAC) protocol is one of the most implemented protocols in this network. The IEEE 802.11 controls the access to the share wireless channel within competing stations. The IEEE 802.11 DCF doubles the Contention Window (CW) size for decreasing the collision within contending stations and to improve the network performances but it is not good for error prone channel because the sudden CW rest to CWmin may cause several collisions. Approach: The research to date has tended to focus on the current number of active stations that needs complex computations. A novel backoff algorithm is presented that optimizes the CW size with take into account the history of packet lost. Results: Finally, we compare the HBCWC with IEEE 802.11 DCF. The simulation results have shown 24.14, 56.71 and 25.33% improvement in Packet Delivery Ratio (PDR), average end to end delay and throughput compared to the IEEE 802.11 DCF. Conclusion: This study showed that monitoring the last three channel statuses achieve better delay and throughput that can be used for multimedia communications.

  • 188.
    Balador, Ali
    et al.
    Universitat Pompeu Fabra, Barcelona, Spain.
    Movaghar, Ali
    Sharif University of Technology, Tehran, Iran.
    Jabbehdari, Sam
    North Tehran Branch, Islamic Azad University, Tehran, Iran.
    Kanellopoulos, Dimitris
    University of Patras, Greece.
    A novel contention window control scheme for IEEE 802.11 WLANs2012Ingår i: IETE Technical Review, ISSN 0256-4602, E-ISSN 0974-5971, Vol. 30, nr 4, s. 202-212Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the IEEE 802.11 standard, network nodes experiencing collisions on the shared medium need a mechanism that can prevent collisions and improve the throughput. Furthermore, a backoff mechanism is used that uniformly selects a random period of time from the contention window (cw) that is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. Prior research has proved that the BEB scheme suffers from a fairness problem and low throughput, especially under high traffic load. In this paper, we present a new backoff control mechanism that is used with the IEEE 802.11 distributed coordination function (DCF). In particular, we propose a dynamic, deterministic contention window control (DDCWC) scheme, in which the backoff range is divided into several small backoff sub-ranges. In the proposed scheme, several network levels are introduced, based on an introduced channel state vector that keeps network history. After successful transmissions and collisions, network nodes change their cw based on their network levels. Our extensive simulation studies show that the DDCWC scheme outperforms four other well-known schemes: Multiplicative Increase and Linear Decrease, Double Increment Double Decrement, Exponential Increase Exponential Decrease, and Linear/Multiplicative Increase and Linear Decrease. Moreover, the proposed scheme, compared with the IEEE 802.11 DCF, gives 30.77% improvement in packet delivery ratio, 31.76% in delay, and 30.81% in throughput.

  • 189.
    Balador, Ali
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Calafate, C. T.
    Universitat Politècnica de València, València, Spain.
    Cano, J. -C
    Universitat Politècnica de València, València, Spain.
    Supporting beacon and event-driven messages in vehicular platoons through token-based strategies2018Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, nr 4, artikel-id 955Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Timely and reliable inter-vehicle communications is a critical requirement to support traffic safety applications, such as vehicle platooning. Furthermore, low-delay communications allow the platoon to react quickly to unexpected events. In this scope, having a predictable and highly effective medium access control (MAC) method is of utmost importance. However, the currently available IEEE 802.11p technology is unable to adequately address these challenges. In this paper, we propose a MAC method especially adapted to platoons, able to transmit beacons within the required time constraints, but with a higher reliability level than IEEE 802.11p, while concurrently enabling efficient dissemination of event-driven messages. The protocol circulates the token within the platoon not in a round-robin fashion, but based on beacon data age, i.e., the time that has passed since the previous collection of status information, thereby automatically offering repeated beacon transmission opportunities for increased reliability. In addition, we propose three different methods for supporting event-driven messages co-existing with beacons. Analysis and simulation results in single and multi-hop scenarios showed that, by providing non-competitive channel access and frequent retransmission opportunities, our protocol can offer beacon delivery within one beacon generation interval while fulfilling the requirements on low-delay dissemination of event-driven messages for traffic safety applications. 

  • 190.
    Balasubramanian, S. M. N.
    et al.
    Technische Universiteit Eindhoven, Eindhoven, Netherlands.
    Afshar, Sara
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Gai, P.
    Evidence Srl, Pisa, Italy.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    J. Bril, Reinder
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Practical challenges for FSLM2019Ingår i: 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, s. 238-239, artikel-id 8607257Konferensbidrag (Refereegranskat)
    Abstract [en]

    The flexible spin-lock model (FSLM) unifies suspension-based and spin-based resource access protocols for partitioned fixed-priority preemptive scheduling based real-time multi-core platforms. Recent work has been done in defining the protocol for FSLM, providing schedulability analysis, and investigating the practical consequences of the theoretical model. FSLM complies to the AUTOSAR standard for the automotive industry, and prototype implementations of FSLM in the OSEK/VDX-complaint Erika Enterprise Real-Time Operating System have been realized. In this paper, we briefly describe some practical challenges to improve efficiency and generality. 

  • 191.
    Balasubramanian, S.M.N
    et al.
    Technische Universiteit Eindhoven, Eindhoven, Netherlands.
    Afshar, Sara Zargari
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Gai, Paolo
    Evidence Srl, Pisa, Italy.
    Bril, Reinder J.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Technische Universiteit Eindhoven, Eindhoven, Netherlands.
    A dual shared stack for FSLM in Erika enterprise2017Ingår i: The 23rd IEEE International Conference on Embedded and Real-Time Computing Systems and Applications - WiP Session RTCSA'17, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Recently, the flexible spin-lock model (FSLM) has been introduced, unifying spin-based and suspension-based resource sharing protocols for real-time multi-core platforms. Unlike the multiprocessor stack resource policy (MSRP), FSLM doesn’t allow tasks on a core to share a single stack, however. In this paper, we present a hypothesis claiming that for a restricted range of spin-lock priorities, FSLM requires only two stacks. We briefly describe our implementation of a dual stack for FSLM in the Erika Enterprise RTOS as instantiated on an Altera Nios II platform using 4 soft-core processors.

  • 192.
    Balasubramanian, S.M.N
    et al.
    Tech Univ Eindhoven, Eindhoven, Netherlands.
    Afshar, Sara Zargari
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Gai, Paolo
    Evidence Srl, Pisa, Italy.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    J. Bril, Reinder
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Tech Univ Eindhoven, Eindhoven, Netherlands.
    Incorporating implementation overheads in the analysis for the flexible spin-lock model2017Ingår i: IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, 2017, s. 411-8418Konferensbidrag (Refereegranskat)
    Abstract [en]

    The flexible spin-lock model (FSLM) unifies suspension-based and spin-based resource sharing protocols for partitioned fixed-priority preemptive scheduling based real-time multiprocessor platforms. Recent work has been done in defining the protocol for FSLM and providing a schedulability analysis without accounting for the implementation overheads. In this paper, we extend the analysis for FSLM with implementation overheads. Utilizing an initial implementation of FSLM in the OSEK/VDX-compliant Erika Enterprise RTOS on an Altera Nios II platform using 4 soft-core processors, we present an improved implementation. Given the design of the implementation, the overheads are characterized and incorporated in specific terms of the existing analysis. The paper also supplements the analysis with measurement results, enabling an analytical comparison of FSLM with the natively provided multiprocessor stack resource policy (MSRP), which may serve as a guideline for the choice of FSLM or MSRP for a specific application.

  • 193.
    Balatinac, Ivan
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Radosevic, Iva
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Architecting for the cloud2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Cloud Computing is an emerging new computing paradigm which is developed out of service-orientation, grid computing, parallel computing, utility computing, autonomic computing, and virtualization paradigms. Both industry and academia have experienced its rapid growth and are exploring full usage of its potentials to maintain their services provided to customers and partners. In this context, a key aspect to investigate is how to architect or design cloud-based application that meet various system requirements of customers’ needs. In this thesis, we have applied the systematic literature review method to explore the main concerns when architecting for the cloud. We have identified, classified, and extracted existing approaches and solutions for specific concerns based on the existing research articles that focus on planning and providing cloud architecture or design for different concerns and needs. The main contribution of the thesis is a catalogued architecture solutions for managing specific concerns when architecting for the cloud.

  • 194.
    Ballesteros, A.
    et al.
    DMI, Universitat de les Illes Balears, Spain.
    Proenza, J.
    DMI, Universitat de les Illes Balears, Spain.
    Gessner, D.
    DMI, Universitat de les Illes Balears, Spain.
    Rodriguez-Navas, Guillermo
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Sauter, T.
    Danube University Krems, Austria.
    Achieving elementary cycle synchronization between masters in the flexible time-triggered replicated star for ethernet2014Ingår i: 19th IEEE International Conference on Emerging Technologies and Factory Automation, ETFA 2014, 2014, s. Article number 7005335-Konferensbidrag (Refereegranskat)
    Abstract [en]

    For a distributed embedded system (DES) to operate continuously in a dynamic environment, it must be flexible and highly reliable. This applies in particular to its communication subsystem. The Flexible Time-Triggered Replicated Star for Ethernet (FTTRS) aims at providing such a subsystem by means of a highly-reliable switched-Ethernet architecture based on the Flexible Time-Triggered paradigm (FTT), a master/slave communication paradigm where the master periodically polls the slaves using so-called trigger messages (TMs). In particular, FTTRS interconnects nodes by redundant communication paths provided by two switches, each embedding an FTT master that manages the communication. This allows FTTRS to tolerate the failure of one switch without interrupting the communication as long as the masters are replica determinate, i.e., provide identical service to the slaves. The master replica determinism entails the masters broadcasting their TMs in a lockstep fashion: when one master broadcasts a TM, the other should do the same quasi-simultaneously. In this paper we present a solution inspired by the Precision Time Protocol (PTP) for achieving this lockstep transmission and preliminary results showing the precision with which we can synchronize the masters on a software prototype.

  • 195.
    Ballesteros, Joaquin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Tudela, A.
    Department of Electronic Technology, University of Malaga, Malaga, Spain.
    Caro-Romero, J. R.
    Department of Electronic Technology, University of Malaga, Malaga, Spain.
    Urdiales, C.
    Department of Electronic Technology, University of Malaga, Malaga, Spain.
    A cane-based low cost sensor to implement attention mechanisms in telecare robots2019Ingår i: 2019 International Conference on Robotics and Automation (ICRA), Institute of Electrical and Electronics Engineers Inc. , 2019, s. 1473-1478Konferensbidrag (Refereegranskat)
    Abstract [en]

    Telepresence robots have been recently used for Comprehensive Geriatric Assessment (CGA). Since the robot can not track a person continuously, there are several strategies to decide when to check them, from cyclic checks to simple requests from users and/or caregivers. In order to adapt to the user needs and condition, it is preferable to perform CGA as soon as regularities appear. However, this requires detection of potential issues in users to offer immediate service. In this work we propose a new low cost force sensor system to detect user's condition and attract attention of CGA robots, so they can perform a full examination on a need basis. The main advantages of this system are: i) it can be attached to any standard commercial cane; ii) its power consumption is very reduced; and iii) it provides continuous information as long as the user walks. It has been tested with several elderly volunteers in care facilities. Results have proven that the sensor readings are indeed correlated with the users' condition. 

  • 196.
    Ballesteros, Joaquin
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Tudela, Alberto J.
    University of Malaga, Malaga, Spain.
    Caro-Romero, J. R.
    University of Malaga, Malaga, Spain.
    Urdiales, C.
    University of Malaga, Malaga, Spain.
    Weight-Bearing Estimation for Cane Users by Using Onboard Sensors2019Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 19, nr 3Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mobility is a fundamental requirement for a healthy, active lifestyle. Gait analysis is widely acknowledged as a clinically useful tool for identifying problems with mobility, as identifying abnormalities within the gait profile is essential to correct them via training, drugs, or surgical intervention. However, continuous gait analysis is difficult to achieve due to technical limitations, namely the need for specific hardware and constraints on time and test environment to acquire reliable data. Wearables may provide a solution if users carry them most of the time they are walking. We propose to add sensors to walking canes to assess user's mobility. Canes are frequently used by people who cannot completely support their own weight due to pain or balance issues. Furthermore, in absence of neurological disorders, the load on the cane is correlated with the user condition. Sensorized canes already exist, but often rely on expensive sensors and major device modifications are required. Thus, the number of potential users is severely limited. In this work, we propose an affordable module for load monitoring so that it can be widely used as a screening tool. The main advantages of our module are: (i) it can be deployed in any standard cane with minimal changes that do not affect ergonomics; (ii) it can be used every day, anywhere for long-term monitoring. We have validated our prototype with 10 different elderly volunteers that required a cane to walk, either for balance or partial weight bearing. Volunteers were asked to complete a 10 m test and, then, to move freely for an extra minute. The load peaks on the cane, corresponding to maximum support instants during the gait cycle, were measured while they moved. For validation, we calculated their gait speed using a chronometer during the 10 m test, as it is reportedly related to their condition. The correlation between speed (condition) and load results proves that our module provides meaningful information for screening. In conclusion, our module monitors support in a continuous, unsupervised, nonintrusive way during users' daily routines, plus only mechanical adjustment (cane height) is needed to change from one user to another.

  • 197.
    Banaee, Hadi
    et al.
    Örebro University, Sweden.
    Ahmed, Mobyen Uddin
    Örebro University, Sweden.
    Loutfi, Amy
    Örebro University, Sweden.
    A framework for automatic text generation of trends in physiological time series data2013Ingår i: Proceedings - 2013 IEEE International Conference on Systems, Man, and Cybernetics, SMC 2013, 2013, s. 3876-3881Konferensbidrag (Refereegranskat)
    Abstract [en]

    Health monitoring systems using wearable sensors have rapidly grown in the biomedical community. The main challenges in physiological data monitoring are to analyse large volumes of health measurements and to represent the acquired information. Natural language generation is an effective method to create summaries for both clinicians and patients as it can describe useful information extracted from sensor data in textual format. This paper presents a framework of a natural language generation system that provides a text-based representation of the extracted numeric information from physiological sensor signals. More specifically, a new partial trend detection algorithm is introduced to capture the particular changes and events of health parameters. The extracted information is then represented considering linguistic characterisation of numeric features. Experimental analysis was performed using a wearable sensor and demonstrates a possible output in natural language text.

  • 198.
    Banaee, Hadi
    et al.
    Örebro University, Sweden.
    Ahmed, Mobyen Uddin
    Örebro University, Sweden.
    Loutfi, Amy
    Örebro University, Sweden.
    Data mining for wearable sensors in health monitoring systems: a review of recent trends and challenges2013Ingår i: Sensors, ISSN 1424-8220, Vol. 13, nr 12, s. 17472-17500Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The past few years have witnessed an increase in the development of wearable sensors for health monitoring systems. This increase has been due to several factors such as development in sensor technology as well as directed efforts on political and stakeholder levels to promote projects which address the need for providing new methods for care given increasing challenges with an aging population. An important aspect of study in such system is how the data is treated and processed. This paper provides a recent review of the latest methods and algorithms used to analyze data from wearable sensors used for physiological monitoring of vital signs in healthcare services. In particular, the paper outlines the more common data mining tasks that have been applied such as anomaly detection, prediction and decision making when considering in particular continuous time series measurements. Moreover, the paper further details the suitability of particular data mining and machine learning methods used to process the physiological data and provides an overview of the properties of the data sets used in experimental validation. Finally, based on this literature review, a number of key challenges have been outlined for data mining methods in health monitoring systems.

  • 199.
    Banaee, Hadi
    et al.
    Örebro University, Sweden.
    Ahmed, Mobyen Uddin
    Örebro University, Sweden.
    Loutfi, Amy
    Örebro University, Sweden.
    Towards NLG for Physiological Data Monitoring with Body Area Networks2013Ingår i: 14th European Workshop on Natural Language Generation ENLG, London, United Kingdom, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    This position paper presents an on-going work on a natural language generation framework that is particularly tailored for summary text generation from body area networks. We present an overview of the main challenges when considering this type of sensor devices used for at home monitoring of health parameters. This pa- per describes the first steps towards the im- plementation of a system which collects information from heart rate and respira- tion rate using a wearable sensor. The pa- per further outlines the direction for future work and in particular the challenges for NLG in this application domain

  • 200.
    Bankarusamy, Sudhangathan
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Towards hardware accelerated rectification of high speed stereo image streams2017Självständigt arbete på avancerad nivå (masterexamen), 80 poäng / 120 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The process of combining two views of a scene in order to obtain depth information is called stereo vision. When the same is done using a computer it is then called computer stereo vision. Stereo vision is used in robotic application where depth of an object plays a role. Two cameras mounted on a rig is called a stereo camera system. Such a system is able to capture two views and enable robotic application to use the depth information to complete tasks. Anomalies are bound to occur in such a stereo rig, when both the cameras are not parallel to each other. Mounting of the cameras on a rig accurately has physical alignment limitations. Images taken from such a rig has inaccurate depth information and has to be rectified. Therefore rectification is a pre-requisite to computer stereo vision. One such a stereo rig used in this thesis is the GIMME2 stereo camera system. The system has two 10 mega-pixel cameras with on-board FPGA, RAM, processor running Linux operating system, multiple Ethernet ports and an SD card feature amongst others. Stereo rectification on memory constrained hardware is a challenging task as the process itself requires both the images to be stored in the memory. The FPGA on the GIMME2 systems must be used in order to achieve the best possible speed. Programming a system that does not have a display and for used for a specific purpose is called embedded programming. The purpose of this system is distance estimation and working with such a system falls in the Embedded Systems program. This thesis presents a method that makes rectification a step ahead for this particular system. The functionality of the algorithm is shown in MATLAB and using VHDL and is compared to available tools and systems.

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