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  • 1.
    Abrahamsson, Henrik
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Internet Traffic Management2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 2.
    Abrahamsson, Henrik
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Network overload avoidance by traffic engineering and content caching2012Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 3.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Caching for IPTV distribution with time-shift2013Ingår i: 2013 International Conference on Computing, Networking and Communications, ICNC 2013, IEEE , 2013, s. 916-921Konferensbidrag (Refereegranskat)
    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

  • 4.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Simulation of IPTV caching strategies2010Ingår i: Proceedings of the 2010 International Symposium on Performance Evaluation of Computer and Telecommunication Systems, 2010, s. 187-193Konferensbidrag (Refereegranskat)
    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.

  • 5.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Nordmark, Mattias
    TeliaSonera AB, Stockholm, Sweden .
    Program popularity and viewer behaviour in a large TV-on-Demand system2012Ingår i: IMC '12 Proceedings of the 2012 ACM conference on Internet measurement conference, New York: ACM , 2012, s. 199-210Konferensbidrag (Refereegranskat)
    Abstract [en]

    Today increasingly large volumes of TV and video are distributed over IP-networks and over the Internet. It is therefore essential for traffic and cache management to understand TV program popularity and access patterns in real networks.

    In this paper we study access patterns in a large TV-on-Demand system over four months. We study user behaviour and program popularity and its impact on caching. The demand varies a lot in daily and weekly cycles. There are large peaks in demand, especially on Friday and Saturday evenings, that need to be handled.

    We see that the cacheability, the share of requests that are not first-time requests, is very high. Furthermore, there is a small set of programs that account for a large fraction of the requests. We also find that the share of requests for the top most popular programs grows during prime time, and the change rate among them decreases. This is important for caching. The cache hit ratio increases during prime time when the demand is the highest, and aching makes the biggest difference when it matters most.

    We also study the popularity (in terms of number of requests and rank) of individual programs and how that changes over time. Also, we see that the type of programs offered determines what the access pattern will look like.

  • 6.
    Afshar, Sara
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Bril, Reinder J.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Technische Universiteit Eindhoven, Eindhoven, Netherlands.
    Nolte, Thomas
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Resource Sharing Under Global Scheduling with Partial Processor Bandwidth2015Ingår i: 2015 10th IEEE International Symposium on Industrial Embedded Systems, SIES 2015 - Proceedings, 2015, s. 195-206Konferensbidrag (Refereegranskat)
    Abstract [en]

    Resource efficient approaches are of great importance for resource constrained embedded systems. In this paper, we present an approach targeting systems where tasks of a critical application are partitioned on a multi-core platform and by using resource reservation techniques, the remaining bandwidth capacity on each core is utilized for one or a set of non-critical application(s). To provide a resource efficient solution and to exploit the potential parallelism of the extra applications on the multi-core processor, global scheduling is used to schedule the tasks of the non-critical applications. Recently a specific instantiation of such a system has been studied where tasks do not share resources other than the processor. In this paper, we enable semaphore-based resource sharing among tasks within critical and non-critical applications using a suspension-based synchronization protocol. Tasks of non-critical applications have partial access to the processor bandwidth. The paper provides the systems schedulability analysis where blocking due to resource sharing is bounded. Further, we perform experimental evaluations under balanced and unbalanced allocation of tasks of a critical application to cores.

  • 7.
    Asplund, Lars
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Johnson, B.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Lundqvist, Kristina
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Burns, Alan
    Session Summary: The Ravenscar Profile and Implementation Issues1999Ingår i: ACM SIGAda Ada Letters, Vol. XIX, nr 2, s. 12-14Artikel i tidskrift (Övrigt vetenskapligt)
  • 8.
    Avritzer, A
    et al.
    Siemens Corporate Research, USA.
    Tanikella, R
    Siemens Corporate Research, USA.
    James, K
    Siemens Corporate Research, USA.
    Cole, R
    JHU, Applied Physics Laboratory, USA.
    weyuker, elaine
    AT and T Labs, USA.
    Monitoring for Security Intrusion using Performance Signatures2010Ingår i: WOSP/SIPEW'10 - Proceedings of the 1st Joint WOSP/SIPEW International Conference on Performance Engineering, 2010, s. 93-103Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new approach for detecting security attacks on software systems by monitoring the software system performance signatures is introduced. We present a proposed architecture for security intrusion detection using off-the-shelf security monitoring tools and performance signatures. Our approach relies on the assumption that the performance signature of the well-behaved system can be measured and that the performancesignature of several types of attacks can be identified. This assumption has been validated for operations support systems that are used to monitor large infrastructures and receive aggregated traffic that is periodic in nature. Examples of such infrastructures include telecommunications systems, transportation systems and power generation systems. In addition, significant deviation from well-behaved system performance signatures can be used to trigger alerts about new types of security attacks. We used a custom performance benchmark and five types of security attacks to deriveperformance signatures for the normal mode of operation and the security attack mode of operation. We observed that one of the types of thesecurity attacks went undetected by the off-the-shelf security monitoring tools but was detected by our approach of monitoring performance signatures. We conclude that an architecture for security intrusion detection can be effectively complemented by monitoring of performance signatures.

  • 9.
    Balador, Ali
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Kouba, A.
    Polytechnic Institute of Porto, Porto 4249-015, Portugal.
    Cassioli, D.
    University of L'Aquila, L'Aquila, 67100, Italy.
    Foukalas, F.
    Technical University of Denmark, Kongens Lyngby, 2800, Denmark.
    Severino, R.
    Polytechnic Institute of Porto, Porto 4249-015, Portugal.
    Stepanova, D.
    Finnish Meteorological Institute, 99600 Sodankylä, Finland.
    Agosta, G.
    Politecnico di Milano ,Via G. Ponzio 32, Milano, I-20133, Italy.
    Xie, J.
    Group Technology & Research, DNV GL, Veritasveien 1, Norway.
    Pomante, L.
    University of L'Aquila, L'Aquila, 67100, Italy.
    Mongelli, M.
    CNR-IEIIT ,via De Marini 6, Genova, 16149, Italy.
    Pierini, P.
    Intecs S.p.A., Pisa, 56121, Italy.
    Petersen, S.
    SINTEF ICT, Trondheim, 7465, Norway.
    Sukuvaara, T.
    Finnish Meteorological Institute, 99600 Sodankylä, Finland.
    Wireless Communication Technologies for Safe Cooperative Cyber Physical Systems2018Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, nr 11, artikel-id 4075Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cooperative Cyber-Physical Systems (Co-CPSs) can be enabled using wireless communication technologies, which in principle should address reliability and safety challenges. Safety for Co-CPS enabled by wireless communication technologies is a crucial aspect and requires new dedicated design approaches. In this paper, we provide an overview of five Co-CPS use cases, as introduced in our SafeCOP EU project, and analyze their safety design requirements. Next, we provide a comprehensive analysis of the main existing wireless communication technologies giving details about the protocols developed within particular standardization bodies. We also investigate to what extent they address the non-functional requirements in terms of safety, security and real time, in the different application domains of each use case. Finally, we discuss general recommendations about the use of different wireless communication technologies showing their potentials in the selected real-world use cases. The discussion is provided under consideration in the 5G standardization process within 3GPP, whose current efforts are inline to current gaps in wireless communications protocols for Co-CPSs including many future use cases.

  • 10.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Hierarchical Real Time Scheduling and Synchronization2008Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

     

    The Hierarchical Scheduling Framework (HSF) has been introduced to enable compositional schedulability analysis and execution of embedded software systems with real-time constraints. In this thesis, we consider a system consisting of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF provides CPU-time to the subsystems and it guarantees that the individual subsystems respect their allocated CPU budgets. However, if subsystems are allowed to share logical resources, extra complexity with respect to analysis and run-time mechanisms is introduced. In this thesis we address three issues related to hierarchical scheduling of semi-independent subsystems. In the first part, we investigate the feasibility of implementing the hierarchical scheduling framework in a commercial operating system, and we present the detailed figures of various key properties with respect to the overhead of the implementation.

    In the second part, we studied the problem of supporting shared resources in a hierarchical scheduling framework and we propose two different solutions to support resource sharing. The first proposed solution is called SIRAP, a synchronization protocol for resource sharing in hierarchically scheduled open real-time systems, and the second solution is an enhanced overrun mechanism.

    In the third part, we present a resource efficient approach to minimize system load (i.e., the collective CPU requirements to guarantee the schedulability of hierarchically scheduled subsystems). Our work is motivated from a tradeoff between reducing resource locking times and reducing system load. We formulate an optimization problem that determines the resource locking times of each individual subsystem with the goal of minimizing the system load subject to system schedulability. We present linear complexity algorithms to find an optimal solution to the problem, and we prove their correctness

     

     

     

     

     

     

     

  • 11.
    Behnam, Moris
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Nolte, Thomas
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Shin, Insik
    Åsberg, Mikael
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Bril, Reinder
    Technische Universiteit Eindhoven.
    Towards Hierarchical Scheduling in VxWorks2008Ingår i: OSPERT 2008, Proceedings of the Fourth International Workshop on Operating Systems Platforms for Embedded Real-Time Applications, 2008, s. 63-72Konferensbidrag (Refereegranskat)
    Abstract [en]

    Over the years, we have worked on hierarchical schedulingframeworks from a theoretical point of view. In thispaper we present our initial results of the implementationof our hierarchical scheduling framework in a commercialoperating system VxWorks. The purpose of the implementationis twofold: (1) we would like to demonstrate feasibilityof its implementation in a commercial operating system,without having to modify the kernel source code, and (2) wewould like to present detailed figures of various key propertieswith respect to the overhead of the implementation.During the implementation of the hierarchical scheduler,we have also developed a number of simple task schedulers.We present details of the implementation of Rate-Monotonic(RM) and Earliest Deadline First (EDF) schedulers. Finally,we present the design of our hierarchical schedulingframework, and we discuss our current status in the project.

  • 12.
    Behnam, Moris
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Shin, Insik
    Nolte, Thomas
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Nolin, Mikael
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Scheduling of Semi-Independent Real-Time Components: Overrun Methods and Resource Holding Times2008Ingår i: Proceedings of the 13th IEEE International Conference on Emerging echnologies and Factory Automation (ETFA’08), 2008, s. 575-582Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Hierarchical Scheduling Framework (HSF) has been introduced as a design-time framework enabling compositional schedulability analysis of embedded software systems with real-time properties. In this paper a system consists of a number of semi-independent components called subsystems. Subsystems are developed independently and later integrated to form a system. To support this design process, our proposed methods allow nonintrusive configuration and tuning of subsystem timing behaviour via subsystem interfaces for selecting scheduling parameters. This paper considers two methods to handle overruns due to resource sharing between subsystems in the HSF. We present the scheduling algorithms for overruns and their associated schedulability analysis, together with analysis that shows under what circumstances one or the other overrun method is preferred. Furthermore, we show how to calculate resource-holding times within our framework.

  • 13.
    Björnhager, Jens
    Mälardalens högskola, Akademin för innovation, design och teknik.
    CRL2ALF: En översättare från PowerPC till ALF2011Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Realtidssystem ställer hårda krav på dess ingående mjukvaras temporala beteende. Programmen måste bete sig deterministiskt och ge svar inom satta tidsgränser. Med hårda krav följer större behov av verktyg att testa koden med. WCET (Worst Case Execution Time)-analys har som mål att finna en övre gräns för ett programs exekveringstid. SWEET (SWEdish Execution Time) är ett verktyg för WCET-analys utvecklat av en forskargrupp vid Mälardalens Högskola.

    PowerPC är en klassisk processorarkitektur som utvecklades av Apple, Motorola och IBM och släpptes 1991. Den har bland annat använts av Apple i äldre versioner av deras Macintosh-datorer och i TV-spelskonsoler såsom Nintendo GameCube och är stor inom inbyggda system.

    Tidigare har endast analys av källkod, C, varit möjlig i SWEET. Målet för detta examensarbete var att möjliggöra analys av körbara program för vilka källkoden ej är tillgänglig, Detta gjordes genom att konstruera en översättare från PowerPC-binärer till det programformat som SWEET använder för sina statiska analyser, ALF, med hjälp av tredjepartsverktyget aiT från AbsInt GmbH.

    Resultatet blev en med undantag för flyttalsinstruktioner komplett översättare av PowerPC-program till ALF-kod. De flesta genererade programfiler som har testats i SWEET har gett lyckat resultat. 

  • 14.
    Daneryd, Oscar
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Congestion Management at the Network Edge2014Självständigt arbete på grundnivå (högskoleexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the Internet of today there is a demand for both high bandwidth and low delays. Bandwidth-heavy applications such as large downloads or video streaming compete with more delay-sensitive applications; web-browsing, VoIP and video games. These applications represent a growing share of Internet traffic.

    Buffers are an essential part of network equipment. They prevent packet loss and help maintain hight throughput. As bandwidths have increased so have the buffer sizes. In some cases way to much. This, and the fact that Active Queue Management (AQM) is seldom implemented, has given rise to a phenomenon called Bufferbloat.

    Bufferbloat is manifested at the bottleneck of the network path by large flows creating standing queues that choke out smaller, and usually delay-sensitive, flows. Since the bottleneck is often located at the consumer edge, this is where the focus of this thesis lies.

    This work evaluates three different AQM solutions that lower delays without requiring complicated configuration; CoDel, FQ_CoDel and PIE. FQ_CoDel had the best performance in the tests, with the lowest consistent delays and high throughput. This thesis recommends that AQM is implemented at the network edge, preferably FQ_CoDel.

  • 15.
    Degerfält, Per
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Strömberg, Niklas
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Programmering av styrning av tvättarm på tvättrobot.2008Självständigt arbete på avancerad nivå (magisterexamen), 20 poäng / 30 hpStudentuppsats
    Abstract [en]

    Ramsta Robotics är ett företag som ligger i Uppsala. Företaget grundades 1999 av tre uppfinnare. Man har utvecklat en robot, som används för att göra rent i djurstallar. Tvättarbetet har hittills gjorts helt manuellt med högtryckstvätt. I framför allt svinhus är

    arbetsmiljön direkt hälsovådlig – bland annat på grund av alla de kväveföreningar som löses ut när vattnet blöter upp anläggningen. Principen för roboten är att man lär den genom att med en styrpanel styra en arm så att alla ytor i boxen blir besprutad med högtryckstvätten minst en gång. Hela förloppet spelas in, och sedan kan roboten spela upp programmet flera gånger, och på det sättet kan roboten på egen hand göra rent i ett antal boxar, som står efter varandra.

    Affärsidén har varit att utveckla en prisvärd robot där datastödet utgörs av ett enkelt styr- och reglersystem för industrin, en s.k. PLC. Den styr via ett drivkort 5-6 motorer, dock bara en motor i taget. Den traditionella robotteknikens komplexa mekanik och höga prisnivåer gör det direkt omöjligt att sätta in denna teknikplattform i jordbrukssammanhang. Kraven på en tvättrobot när det gäller mikrometerprecision och hastighet är heller inte lika hög som hos mer traditionella robotar.

    Idag säljs detta system i ett flertal länder i Europa och också i Kanada. Hittills har c:a 150 robotar sålts, de flesta för att användas i svinproduktion men även fågel produktion och annan

    industri har visat sig vara en marknad. C:a 100 maskiner är sålda i Sverige som representerar c:a 0,3 % av världens produktion av fläskkött. Eftersom Sverige är en så liten marknad i agrara sammanhang är verksamheten idag främst inriktad på export. Verksamheten är expanderande och företaget sysselsätter idag 4 personer på kontoret i Uppsala förutom tillverkning och service som köps externt. Omsättningen 2005 var c:a 8 milj. kronor och beräknas för 2006 närma sig 15 milj.

    I samarbete med Robotdalen kommer fem olika examensarbeten på Mälardalens högskola att ge ett ökat tekniskt innehåll i företagets olika lösningar.

    Projektbeskrivning:

    Med individuella styrkort på respektive motor är det möjligt att använda en helt annan teknik för styrningen av motorerna på robotarmen. Man kan gå från att styra respektive led till att

    utnyttja invers kinematik, och användaren styr var munstycket ska vara beläget, och styrprogrammet omvandlar den önskade positionen till vinklar och lägen för respektive led.

    Att bygga ett komplett styrsystem kan vara ganska omfattande, men avsikten med detta examensarbete är att göra en första version av styrprogram, där användaren kanske kör fram armen till en punkt på en yta som ska tvättas, och sedan till en andra punkt, till en tredje.

    Dessa tre punkter definierar en triangel på samma sätt som man bygger upp ytor i OpenGL.

    En fjärde punkt ger med punkterna två och tre ytterligare en triangel. När sedan en hel yta har ’ritats upp’ (för en rak rektangel är det endast två trianglar) ska programmet kunna styra ut

    robotarmens rörelsemönster.

  • 16.
    Dunkels, Adam
    Swedish Institute of Computer Science.
    Full TCP/IP for 8-bit Architectures2003Ingår i: MobiSys '03 Proceedings of the 1st international conference on Mobile systems, applications and services, 2003, s. 85-98Konferensbidrag (Refereegranskat)
    Abstract [en]

    We describe two small and portable TCP/IP implementations fulfilling the subset of RFC1122 requirements needed for full host-to-host interoperability. Our TCP/IP implementations do not sacrifice any of TCP's mechanisms such as urgent data or congestion control. They support IP fragment reassembly and the number of multiple simultaneous connections is limited only by the available RAM. Despite being small and simple, our implementations do not require their peers to have complex, full-size stacks, but can communicate with peers running a similarly light-weight stack. The code size is on the order of 10 kilobytes and RAM usage can be configured to be as low as a few hundred bytes.

  • 17.
    Dunkels, Adam
    et al.
    Swedish Institute of Computer Science, Sweden.
    Schmidt, Oliver
    Voigt, Thiemo
    Swedish Institute of Computer Science, Sweden.
    Using Protothreads for Sensor Node Programming2005Ingår i: Proceedings of the REALWSN 2005 Workshop on Real-World Wireless Sensor Networks (2005), 2005Konferensbidrag (Refereegranskat)
  • 18.
    Dunkels, Adam
    et al.
    Swedish Institute of Computer Science, Sweden.
    Voigt, Thiemo
    Swedish Institute of Computer Science, Sweden.
    Alonso, Juan
    Swedish Institute of Computer Science, Sweden.
    Making TCP/IP viable for wireless sensor networks2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    The TCP/IP protocol suite, which has proven itself highly successful in wired networks, is often claimed to be unsuited for wireless micro-sensor networks. In this work, we question this conventional wisdom and present a number of mechanisms that are intended to enable the use of TCP/IP for wireless sensor networks: spatial IP address assignment, shared context header compression, application overlay routing, and distributed TCP caching (DTC). Sensor networks based on TCP/IP have the advantage of being able to directly communicate with an infrastructure consisting either of a wired IP network or of IP-based wireless technology such as GPRS. We have implemented parts of our mechanisms both in a simulator environment and on actual sensor nodes. Our preliminary results are promising.

  • 19.
    Elgström, Dennis
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Implementation of secure network solutions for Project Area2014Självständigt arbete på grundnivå (högskoleexamen), 180 hpStudentuppsats (Examensarbete)
  • 20.
    Fernandez, Z.
    et al.
    Information and Communication Technologies Area, Ikerlan Technology Research Centre, Mondragón, Spain.
    Val, I.
    Information and Communication Technologies Area, Ikerlan Technology Research Centre, Mondragón, Spain.
    Mendicute, M.
    Signal Theory and Communications Area, Mondragon University, Mondragón, Spain.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Analysis and Evaluation of Self-Organizing TDMA for Industrial Applications2019Ingår i: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS, Institute of Electrical and Electronics Engineers Inc. , 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    With the Industry 4.0 revolution, the inclusion of wireless communications with real-time requirements has been gaining popularity in industrial applications. As existing wireless technologies do not fully satisfy the stringent requirements of the most critical industrial applications, wired, centralized networks are often used. However, when the application requires mobility, there is no other way than to use wireless communications. Further, in applications where the topology changes dynamically and a large number of devices are mobile, centralized protocols are less suitable. Unfortunately, most decentralized medium access protocols are not predictable, and thereby not able to fulfil the real-time requirements. To address these challenges, in this paper Self-Organizing Time Division Multiple Access (STDMA) is analysed to assess its suitability for use in industrial applications. The analysis has been carried out through simulations under a multipath dispersed time-variant industrial channel while subject to a variable Doppler shift. To this end, several metrics such as channel access delay, slot occupation distribution (SOD), packet losses and packet inter-arrival time (PIAT) have been evaluated, using OMNeT++ in combination with the VEINS framework. 

  • 21.
    Fersman, Elena
    et al.
    Uppsala University, Sweden.
    Krcal, Pavel
    Uppsala University, Sweden.
    Pettersson, Paul
    Mälardalens högskola, Institutionen för datavetenskap och elektronik. Uppsala University, Sweden.
    Yi, Wang
    Uppsala University, Sweden.
    Task Automata: Schedulability, Decidability and Undecidability2007Ingår i: International Journal of Information and Computation, ISSN 0890-5401, Vol. 205, s. 1149-1172Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a model, task automata, for real time systems with non-uniformly recurring computation tasks. It is an extended version of timed automata with asynchronous processes that are computation tasks generated (or triggered) by timed events. Compared with classical task models for real time systems, task automata may be used to describe tasks (1) that are generated non-deterministically according to timing constraints in timed automata, (2) that may have interval execution times representing the best case and the worst case execution times, and (3) whose completion times may influence the releases of task instances. We generalize the classical notion of schedulability to task automata. A task automaton is schedulable if there exists a scheduling strategy such that all possible sequences of events generated by the automaton are schedulable in the sense that all associated tasks can be computed within their deadlines. Our first technical result is that the schedulability for a given scheduling strategy can be checked algorithmically for the class of task automata when the best case and the worst case execution times of tasks are equal. The proof is based on a decidable class of suspension automata: timed automata with bounded subtraction in which clocks may be updated by subtractions within a bounded zone. We shall also study the borderline between decidable and undecidable cases. Our second technical result shows that the schedulability checking problem will be undecidable if the following three conditions hold: (1) the execution times of tasks are intervals, (2) the precise finishing time of a task instance may influence new task releases, and (3) a task is allowed to preempt another running task.

  • 22.
    Fersman, Elena
    et al.
    Uppsala University, Sweden.
    Mokrushin, Leonid
    Uppsala University, Sweden.
    Pettersson, Paul
    Uppsala University, Sweden.
    Yi, Wang
    Uppsala University, Sweden.
    Schedulability Analysis of Fixed Priority Systems using Timed Automata2006Ingår i: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 354, nr 2, s. 301-317Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In classic scheduling theory, real-time tasks are usually assumed to be periodic, i.e. tasks are released and computed with fixed rates periodically. To relax the stringent constraints on task arrival times, we propose to use timed automata to describe task arrival patterns. In a previous work, it is shown that the general schedulability checking problem for such models is a reachability problem for a decidable class of timed automata extended with subtraction. Unfortunately, the number of clocks needed in the analysis is proportional to the maximal number of schedulable task instances associated with a model, which is in many cases huge. In this paper, we show that for fixed-priority scheduling strategy, the schedulability checking problem can be solved using standard timed automata with two extra clocks in addition to the clocks used in the original model to describe task arrival times. The analysis can be done in a similar manner to response time analysis in classic Rate-Monotonic Analysis (RMA). The result is further extended to systems with data-dependent control, in which the release time of a task may depend on the time-point at which other tasks finish their execution. For the case when the execution times of tasks are constants, we show that the schedulability problem can be solved using n+1 extra clocks, where n is the number of tasks. The presented analysis techniques have been implemented in the Times tool. For systems with only periodic tasks, the performance of the tool is comparable with tools implementing the classic RMA technique based on equation-solving, without suffering from the exponential explosion in the number of tasks.

  • 23.
    Fogel, Johan
    Mälardalens högskola. Mälardalens högskola, Akademin för innovation, design och teknik.
    IP version 6 in larger city networks and at Internet service providers2009Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Since the 90ies a bunch of problems and flaws in the old Internet Protocol version four has occurred.The biggest problem is the extinction of addresses which will come soon, soon in the matter of theclassic “wolf is coming” matter, but as in the fairy tale the wolf will finally come. When this will happenis unknown, but not many believes it won’t. Carl-Henrik Swanberg CEO for Ericsson once said that year2020 there will be 50 billion mobile units connected to internet. Considering there is maximum 4 billionaddresses in IPv4 the needs for more addresses will be significant. The solution of this is the version sixof Internet Protocol released in middle of the 90ies. This thesis mentions a lot of the problems with theold version and tries to make a good explanation of the benefits and possibilities that lies within thenew. It also contains a larger amount of information on the protocols that lies within this, like newversion of OSPF, the extensions of BGPv4 called multiprotocol BGP (MP-BGP) and new things likenetwork discovery protocol (NDP). The later chapter is about the planning of an implementation atMälarenergi City Network and the implementation at the internet service provider MDFnet whichnowadays runs IPv6 in their core and office network.

  • 24.
    Forsberg, Andreas
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Larsson, Christoffer
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Vidareutveckling av PROFIBUS-modul2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Denna rapport beskriver ett examensarbete som gjordes på företaget Motion Control i Västerås AB. Rapporten följer projektets utvecklingssteg och beskriver hur arbetet med att ta fram elektronik och inbyggd programvara för en kommunikationsmodul har framskridit. Kommunikationsmodulen ska fungera som en länk mellan en styrenhet och en I/O-enhet.

     

    De inledande delarna av rapporten tar upp undersökningar på kommunikationsprotokollen PROFIBUS och PROFINET som är vanliga kommunikationsmetoder inom industrin. Undersökningarna låg till grund för vilket protokoll som skulle användas i modulen. PROFIBUS valdes och en sådan modul togs fram utifrån de krav som ställdes. Vidare beskriver rapporten hur hårdvara samt den inbyggda programvaran har utvecklats. Vid testerna av modulen verifierades om alla krav och önskemål var uppfyllda.

     

    Projektet som helhet var lyckat och efter några mindre hårdvaruförändringar skulle modulen kunna användas i produkter som företaget säljer där PROFIBUS-kommunikation önskas.

  • 25.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Ashjaei, Seyed Mohammad Hossein
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Designing a Bandwidth Management Scheme for Heterogeneous Virtualized Networks2018Ingår i: 2018 IEEE 23RD INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION (ETFA), IEEE , 2018, s. 1079-1082Konferensbidrag (Refereegranskat)
    Abstract [en]

    With envisioned increased density and complexity of future industrial networks, software defined networking (SDN) and network virtualization are considered to be promising techniques for network organization and management. Thus, in this paper we look at heterogeneous software defined networks consisting of several virtual slices and present a bandwidth control algorithm, which is designed to provide control over shared bandwidth both in wired and wireless parts of the network. The designed algorithm has been implemented in real hardware and in this paper we present the initial test results.

  • 26.
    Girs, Svetlana
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Björkman, Mats
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Adopting FEC and Packet Combining to Increase the Performance of IWSNs Using Relaying2015Ingår i: International Conference on Computing and Network Communications CoCoNet'15, 2015, s. 90-97Konferensbidrag (Refereegranskat)
    Abstract [en]

    Industrial networks can benefit significantly from introduction of wireless communication. However, wireless systems suffer from much higher packet error rates than wired networks do, making it difficult to obtain sufficient reliability within application deadlines. One promising approach to increase the reliability of wireless communication systems without causing excessive additional delays is to exploit spatial diversity. However, often in industrial networks it is not possible to place the relay nodes optimally. Due to this not even relay nodes located close to the source are able to receive the source packets missing at the destination correctly and consequently they cannot assist by relaying. Therefore, to benefit even further from relaying, additional measures should be taken both to increase the number of the correct packets at the relay nodes and to allow the destination to recover more correct packets. Consequently, the focus of this work is schemes enabling relaying, forward-error-correction (FEC) and packet combining without causing additional delays or complexity such that it is possible to use off the shelf transceivers. The results show that the introduction of FEC and packet combining does improve performance by enabling relay nodes to help more often. However, the exact gain depends on the specific FEC scheme used and, in particular, the size of the preamble and other fields that must be left uncoded, but still be received correctly, to be able to use FEC on the received packet.

  • 27.
    Hansen, Ewa
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Neander, Jonas
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Nolin, Mikel
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Björkman, Mats
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Energy-Efficient Cluster Formation for Large Sensor Networks using a Minimum Separation Distance2006Ingår i: In proceedings of the Fifth Annual Mediterranean Ad Hoc Networking Workshop, 2006Konferensbidrag (Refereegranskat)
  • 28.
    Hansen, Ewa
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Neander, Jonas
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Sjödin, Mikael
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Björkman, Mats
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Energy-Efficient Cluster Formation for Large Sensor Networks using a Minimum Separation Distance2006Ingår i: Proceedings of The Fifth Annual Mediterranean Ad Hoc Networking Workshop (Med-Hoc-Net 2006), 2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we investigate the usefulness of enforcing a minimum separation distance between cluster heads in a cluster based sensor network, thereby prolonging network lifetime by spreading the cluster heads, thus lowering the average communication energy consumption.

    We have performed initial simulations in order to determine how much we can lower the energy consumption in the sensor network by separating the cluster heads. We have also investigated how the number of clusters affect the energy consumption for a given minimum separation distance.

    The results show that our sensor network performs up to 150% better when introducing a minimum separation distance between cluster heads, comparing the number of messages received at the base station.

    The simulations also show that the minimum separation distance resulting in the lowest energy consumption in our network varies with the number of clusters.

  • 29.
    Hoang, Le-Nam
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Uhlemann, Elisabeth
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Jonsson, M.
    School of Information Technology, Halmstad University, Halmstad, Sweden.
    Relay Grouping to Guarantee Timeliness and Reliability in Wireless Networks2019Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, nr 9, s. 1661-1664, artikel-id 8737952Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Relaying can increase reliability, range, or throughput. In many cyber-physical systems (CPS), relaying is used to maximize reliability before a given deadline. Since concurrent transmissions are not supported by most CPS, time-division multiple access (TDMA) is typically used. However, a major drawback of relaying in TDMA is that pre-allocated time-slots are wasted if their respective transmitters do not have any correctly received packet to relay. Therefore, in this letter, we propose a novel relay grouping scheme to overcome this drawback. Numerical results show that the proposed scheme significantly enhances the reliability while guaranteeing the deadline for each message. 

  • 30.
    Holmqvist, Johan
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Karlsson, Tord
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Enhanced Automotive Real-Time Testing Through Increased Development Process Quality2010Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The purpose of this master thesis is to improve the quality of software testing in a large company developing real-time embedded systems. Software testing is a very important part of software development. By performing comprehensive software testing the quality and validity of a software system can be assured. One of the main issues with software testing is to be sure that the tests are correct. Knowing what to test, but also how to perform testing, is of utmost importance.

    In this thesis, we explore different ways to increase the quality of real-time testing by introducing new techniques in several stages of the software development model. Four complementary methods are suggested. The proposed methods are validated by implementing them in an existing and completed project on a subset of the software development process. The original output from the completed project is compared with the new output.

    The presented results from the validation are positive in the sense that it is shown that the test stage was more qualitative, mostly due to a higher level of quality on input from earlier stages.

  • 31.
    Hosseini, Seyed Morteza
    Mälardalens högskola, Akademin för innovation, design och teknik.
    A Model for Estimating the ExecutionCost of Test Cases2015Självständigt arbete på avancerad nivå (masterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
  • 32.
    Huu, Tung Pham
    et al.
    NUCE, Fac Informat Technol, 55 Giai Phong Rd, Hanoi, Vietnam.
    Quach, Truong Xuan
    TNU Univ Informat & Commun Technol, Ho Chi Minh City, Vietnam.
    Tran, Hung Vinh
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Zepernick, Hans-Jurgen
    Blekinge Inst Technol, Karlskrona, Sweden..
    Sibomana, Louis
    Univ Rwanda, Kigali, Rwanda..
    On Proactive Attacks for Coping With Cooperative Attacks in Relay Networks2017Ingår i: 2017 23RD ASIA-PACIFIC CONFERENCE ON COMMUNICATIONS (APCC): BRIDGING THE METROPOLITAN AND THE REMOTE, IEEE , 2017, s. 220-225Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cooperative communications in which relays assist the transmission of signals from source to destination offer extended radio coverage and improved link reliable. However, transmitting signals with the help of a relay network may also open additional avenues for eavesdropper to overhear confidential information. Further, as jammers and eavesdroppers may cooperate to attack the relay network, offering secure communications becomes a challenging problem. To cope and reduce the effect of such cooperative attacks, we propose a proactive attack scheme in which the legitimate users generate jamming signals in an attempt to counteract such hostile cooperative attacks. In order to assess the security performance of the proactive attack scheme compared to a non-protection scheme, an analytical expression of the secrecy outage probability is derived. Numerical results for different system settings are provided showing that the proactive attack scheme can indeed significantly improve the security performance of the considered relay networks.

  • 33.
    Inam, Rafia
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Cederman, Daniel
    Department of Computing Science and Engineering, Chalmers University.
    Tsigas, Philippas
    Department of Computing Science and Engineering, Chalmers University.
    A* Algorithm for Graphics Processors2010Ingår i: THIRD SWEDISH WORKSHOP ON MULTI-CORE COMPUTING - MCC'10, Chalmers University of Technology, Sweden, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Today's computer games have thousands of agents moving at the same time in areas inhabited by a large number of obstacles. In such an environment it is important to be able to calculate multiple shortest paths concurrently in an efficient manner. The highly parallel nature of the graphics processor suits this scenario perfectly. We have implemented a graphics processor based version of the A* path finding algorithm together with three algorithmic improvements that allow it to work faster and on bigger maps. The first makes use of pre-calculated paths for commonly used paths. The second use multiple threads that work concurrently on the same path. The third improvement makes use of a scheme that hierarchically breaks down large search spaces. In the latter the algorithm first calculates the path on a high level abstraction of the map, lowering the amount of nodes that needs to be visited. This algorithmic technique makes it possible to calculate more paths concurrently on large map settings compared to what was possible using the standard A* algorithm. Experimental results comparing the efficiency of the algorithmic techniques on a NVIDIA GeForce GTX 260 with 24 multi-processors are also presented in the paper.

  • 34.
    Jagemar, Marcus
    et al.
    Ericsson AB, Stockholm, Sweden..
    Ermedahl, Andreas
    Ericsson AB, Stockholm, Sweden..
    Eldh, Sigrid
    Ericsson AB, Stockholm, Sweden..
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Lisper, Björn
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Malardalen Univ, Vasteras, Sweden..
    Enforcing Quality of Service Through Hardware Resource Aware Process Scheduling2018Ingår i: 2018 IEEE 23RD INTERNATIONAL CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION (ETFA), IEEE , 2018, s. 329-336Konferensbidrag (Refereegranskat)
    Abstract [en]

    Hardware manufacturers are forced to improve system performance continuously due to advanced and computationally demanding system functions. Unfortunately - more powerful hardware leads to increased costs. Instead, companies attempt to improve performance by consolidating multiple functions to share the same hardware to exploit existing performance instead. In legacy systems, each function had individual execution environment that guaranteed HW resource isolation and therefore the Quality of Service (QoS). Consolidation of multiple functions increases the risk of shared resource congestion. Current process schedulers focus on time quanta and do not consider shared resources. We present a novel process scheduler that complements current process schedulers by enforcing QoS though Shared Resource Aware (SRA) process scheduling. The SRA scheduler programs the Performance Monitoring Unit (PMU) to generate an overflow interrupt when reaching the assigned process resource quota. The scheduler has the possibility to swap out the process when receiving the interrupt allowing it to enforce the QoS for the scheduled process. We have implemented our scheduling policy as a new scheduling class in Linux. Our experiments show that it efficiently enforces QoS without seriously affect the shared resource usage of other processes executing on the same HW.

  • 35.
    Johansson, Henrik
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Evaluating Vivado High-Level Synthesis on OpenCV Functions for the Zynq-7000 FPGA2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    More complex and intricate Computer Vision algorithms combined with higher resolution image streams put bigger and bigger demands on processing power. CPU clock frequencies are now pushing the limits of possible speeds, and have instead started growing in number of cores. Most Computer Vision algorithms' performance respond well to parallel solutions. Dividing the algorithm over 4-8 CPU cores can give a good speed-up, but using chips with Programmable Logic (PL) such as FPGA's can give even more.

    An interesting recent addition to the FPGA family is a System on Chip (SoC) that combines a CPU and an FPGA in one chip, such as the Zynq-7000 series from Xilinx. This tight integration between the Programmable Logic and Processing System (PS) opens up for designs where C programs can use the programmable logic to accelerate selected parts of the algorithm, while still behaving like a C program.

    On that subject, Xilinx has introduced a new High-Level Synthesis Tool (HLST) called Vivado HLS, which has the power to accelerate C code by synthesizing it to Hardware Description Language (HDL) code. This potentially bridges two otherwise very separate worlds; the ever popular OpenCV library and FPGAs.

    This thesis will focus on evaluating Vivado HLS from Xilinx primarily with image processing in mind for potential use on GIMME-2; a system with a Zynq-7020 SoC and two high resolution image sensors, tailored for stereo vision.

  • 36.
    Johnsson, Andreas
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Björkman, Mats
    Measuring the Impact of Active Probing on TCP2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Available bandwidth measurement methods have be- ome more and more a epted to be used when seeking the status of a network path. To measure the end-toend available bandwidth without a ess to the path routers, these methods inje t UDP based probe pa kets into the network path. The probe-pa ket load an transiently be high and thus it is important to study the impa t on the existing network ows. In this paper, we show and dis uss our simulation results on how the TCP ows are ae ted when inje ting probe pa kets with dierent ight patterns into the network path. We investigate the relation between the amount of inje ted probe pa kets and the redu tion in TCP performan e. Further, we suggest a quantitative denition of the term network friendly probing.

  • 37.
    Johnsson, Andreas
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Björkman, Mats
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Measuring the Impact of Active Probing on TCP2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    Available bandwidth measurement methods have become more and more accepted to be

    used when seeking the status of a network path. To measure the end-to-end available bandwidth without access to the path routers, these methods inject probe packets into the network path. The probe-packet load can transiently be high and thus it is important to study the impact on the existing TCP flows.

    In this paper, we show and discuss our simulation results on how the TCP flows are affected when injecting probe packets with different flight patterns into the network path. We also investigate the relation between the amount of injected probe packets and the reduction in TCP performance. Finally we suggest and discuss a quantitative definition of the term ``network friendly probing''.

  • 38.
    Johnsson, Andreas
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Björkman, Mats
    On measuring the available bandwidth in wireless 802.11b networksManuskript (Övrigt vetenskapligt)
  • 39.
    Johnsson, Andreas
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Melander, Bob
    Björkman, Mats
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    On the Analysis of Packet-Train Probing Schemes2004Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    With a better understanding of how probe packets and cross-traffic packets interact with each other, more accurate measurement methods based on active probing can be developed. Several existing measurement methods rely on packet-train probing schemes. In this article, we study and describe the interactions between probe packets and cross-traffic packets. When one packet within a packet train is delayed, the dispersion (i.e. packet separation) of at least two (and possibly more) probe packets will change. Furthermore, the dispersions are not independent, which may bias calculations based on statistical operations. Many methods use dispersion averages, such as the mean, in the calculation of bandwidth estimates and predictions. We describe cross traffic effects on packet trains. The interaction results in mirror, chain and quantifi- cation patterns. Experiments have been performed in a testbed to explore these patterns. In histograms of delay variations for adjacent probe packets, these patterns are manifested as different identifiable signatures. Finally, we also discuss the effect of these patterns on the mean and median operations.

  • 40.
    Jägemar, Marcus
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Ericsson, Sweden.
    Utilizing Hardware Monitoring to Improve the Performance of Industrial Systems2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The drastically increasing use of Information and Communications Technology has resulted in a growing demand for network capacity. In this Licentiate thesis, we show how to monitor, model and finally improve network performance for large industrial systems. We also show how to use modeling techniques to move performance testing to an earlier design phase, with the aim to reduce the total development time of large systems. Our first contribution is a low-intrusive method for long-term hardware characteristic measurements of production nodes located at customer sites. Our second contribution is a technique to mimic the hardware usage of a production environment by creating a characteristics model. The cloned environment makes function test suites more realistic. The goal when creating the model is to reduce the system development time by moving late-stage performance testing to early design phases thereby improving the quality of the test environment. The third and final contribution is a network performance improvement where we dynamically trade computational capacity for a message round-trip time reduction when there are CPU cycles to spare. We have implemented an automatic feedback controlled mechanism for transparent message compression resulting in improved messaging performance between interconnected network nodes. Our mechanism continuously evaluates eleven compression algorithms on message stream content and network congestion level. The message subsystem will use the compression algorithm that provides the lowest messaging time. If the message content or network load change, a new evaluation is performed. We have conducted several case studies in an industrial environment and verified all contributions on a large telecommunication system manufactured by Ericsson. System engineers frequently use the monitoring and modeling functionality for debugging purposes in production environments. We have deployed all techniques in a complicated industrial legacy system with minimal impact. We show that we can provide not only a solution but a cost-effective solution, which is an important requirement for industrial systems.

  • 41.
    Jägemar, Marcus
    et al.
    Ericsson, Stockholm, Sweden.
    Eldh, Sigrid
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Ermedahl, Andreas
    Ericsson, Stockholm, Sweden.
    Lisper, Björn
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Automatic Message Compression with Overload Protection2016Ingår i: Journal of Systems and Software, ISSN 0164-1212, E-ISSN 1873-1228, Vol. 121, nr 1 nov, s. 209-222Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we show that it is possible to increase the message throughput of a large-scale industrial system by selectively compress messages. The demand for new high-performance message processing systems conflicts with the cost effectiveness of legacy systems. The result is often a mixed environment with several concurrent system generations. Such a mixed environment does not allow a complete replacement of the communication backbone to provide the increased messaging performance. Thus, performance-enhancing software solutions are highly attractive. Our contribution is 1) an online compression mechanism that automatically selects the most appropriate compression algorithm to minimize the message round trip time; 2) a compression overload mechanism that ensures ample resources for other processes sharing the same CPU. We have integrated 11 well-known compression algorithms/configurations and tested them with production node traffic. In our target system, automatic message compression results is a 9.6% reduction of message round trip time. The selection procedure is fully automatic and does not require any manual intervention. The automatic behavior makes it particularly suitable for large systems where it is difficult to predict future system behavior.

  • 42.
    Jägemar, Marcus
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. Ericsson, Stockholm, Sweden.
    Lisper, Björn
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Eldh, Sigrid
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Ermedahl, Andreas
    Ericsson, Stockholm, Sweden.
    Andai, Gabor
    Automatic Benchmarking for Early-Stage Performance Verification of Industrial Systems2016Manuskript (preprint) (Övrigt vetenskapligt)
  • 43.
    Karlström, Daniel
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Implementation of data-collection tools using NetFlow for statistical analysis at the ISP level2012Självständigt arbete på grundnivå (yrkesexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Att försvara sig mot DoS-och DDoS-attacker är svårt att åstadkomma; att hitta och filtrera ut illegitim trafik från det legitima flödet är nästan omöjligt. Att vidta åtgärder när en sådan attack upptäcks kan endast göras när IP-adresserna från angriparna är kända. Detta kan uppnås genom att man övervakar trafikflödet mellan målet för attacken och angriparna och ser vilka som sänder mest data och på så sätt identifierar angriparna.. Detta tillåter företaget eller dess ISP att blockera trafiken ifrån dessa IP-adresser genom att sända trafiken vidare till ingenstans. Detta kallas blackhole-routing eller null-routing.

    Genom att använda redovisnings- och övervakningsprogrammet pmacct syftar denna uppsats på att undersöka hurvida pmacct-sviten är lämpad för större installationer när det gäller att spåra och förhindra DDoS-attacker, såsom hos en Internetleverantör eller dylikt. Potentialla problem som kan uppstå är att mängden trafik som måste analyserar blir för stor och för krävande. Denna avhandling går även igenom pmacct-verktyget i sig.

    Slutsatserna är lovande, vilket indikerar att den har potential av att kunna hantera sådana stora miljöer med noggrann planering.

  • 44.
    Khalilzad, Nima
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Adaptive and Flexible Scheduling Frameworks for Component-Based Real-Time Systems2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Moderna datasystem är ofta utformade för att spela en mångsidig roll. De är därför kapabla till att köra flera mjukvarukomponenter (programvaror) samtidigt. Dessa mjukvarukomponenter delar systemresurser (t.ex. processorn och nätverket) under körning. Målet med mjukvarukomponentens körning är att avsluta sina beräkningar som förväntat. Vissa mjukvarukomponenter har även tidskrav vilket innebär att de inte bara kräver tillgång till systemresurser för att köra sina beräkningar, utan de har även krav på när denna tillgång sker för att mjukvarukomponenterna ska för rätt funktion kunna garantera att beräkningar utförs i rätt tid. Således finns det ett behov av att snabbt dela resurser mellan olika mjukvarukomponenter. Den tids-delning realiseras ofta genom att reservera en tidslucka för komponenten då denna är tänkt att och får använda resursen. Reservationen måste vara tillräcklig för att mjukvarukomponenten ska kunna köra som förväntat. Reservationen måste även tilldelas resurseffektivt dvs resurstid får inte slösas bort i onödan. Genom en resurseffektiv reservation av resurserminskar komponentens fotavtryck på resursen som i sin tur möjliggör integration av flera programvarukomponenter på samma resurs. Denna avhandling fokuserar främst på resurseffektivitet i samband med reservationerna. Två fall behandlas. (I) Komponenter som tål att missa vissa enstaka tidskrav (så kallade mjuka realtidskomponenter): i det här fallet anpassas reservationerna under körning enligt komponenternas ständigt föränderliga önskemål på reservationsstorlek. (II) Komponenter som inte kan hantera att tidskrav överträds (så kallade hårda realtidskomponenter): i det här fallet används flexibla strategier som möjliggör  förbättrad resurseffektiviteten redan vid design av systemet.

  • 45.
    Khalilzad, Nima
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Ashjaei, Mohammad
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Almeida, Luis
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system. IT/DEEC/University of Porto, Portugal.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Nolte, Thomas
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Adaptive Multi-Resource End-to-End Reservations for Component-Based Distributed Real-Time Systems2015Ingår i: ESTIMedia 2015 - 13th IEEE Symposium on Embedded Systems for Real-Time Multimedia, 2015, s. Article number 7351772-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Complexity in the real-time embedded softwaredomain has been growing rapidly. The component-based softwaredevelopment approach facilitates the development process of suchsoftware systems by dividing a complex system into a numberof simpler components. Resource reservation techniques havebeen widely used for providing resources to real-time softwarecomponents. In this paper we target real-time components operatingon a distributed resource infrastructure. Furthermore,we target a class of software components which demonstratedynamic resource consumption behavior. A prime example ofsuch components is a multimedia software component. In thepaper, we present a framework supporting multi-resource endto-end resource reservations. We reserve resource bandwidths onboth processor resources as well as on the network resources. Theproposed framework utilizes a Multiple Input Multiple Output(MIMO) controller which adjusts the sizes of reservations trackingthe dynamic resource demands of the software components. Finally, we present a case study using a multimedia component todemonstrate the performance and efficiency of our framework.

  • 46.
    Khalilzad, Nima
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Nolte, Thomas
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    An Adaptive Scheduling Framework for Component-Based Real-Time Systems2015Rapport (Övrigt vetenskapligt)
  • 47.
    Khalilzad, Nima
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Behnam, Moris
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    Nolte, Thomas
    Mälardalens högskola, Akademin för innovation, design och teknik, Inbyggda system.
    On Component-Based Software Development for Multiprocessor Real-Time Systems2015Ingår i: Proceedings - IEEE 21st International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2015, 2015, s. 132-140Konferensbidrag (Refereegranskat)
    Abstract [en]

    Component-based software development providesa modular approach to develop complex software systems. In the context of real-time systems, it is desirable to abstract the timing properties of software components using an interface foreach component. The timing properties of the whole system, composed of multiple components, is studied using the component interfaces. In this paper we focus on periodic interface models. In the case of components developed for single processor platforms, for examining the system schedulability, the interfaces can be regarded as periodic tasks. Thus, making it possible to use the conventional schedulability analyses for the system level schedulability test. In the case of components developed formultiprocessors, since interfaces may have utilization larger than 100 % of a single processor, it is not possible to directly use the component interfaces for the system schedulability test. There-fore, the interfaces have to be decomposed before performing thesystem level schedulability test. In this paper, we target the special case of partitioned EDF for scheduling the components integrated on a multiprocessor. Therefore, the system level schedulability test is equivalent to finding a feasible allocation of component interfaces on the multiprocessor. We propose two algorithms for allocating the multiprocessor periodic interfaces. In addition, we propose anorthogonal approach for developing component-based real-timesystems on multiprocessors in which components with utilizationmore than 100 % of a single processor are divided into smaller subcomponents before abstracting their interfaces. We show, through extensive evaluations, that our alternative approach significantly reduces the interface overhead.

  • 48.
    Kristoffersson, Annica
    et al.
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Coradeschi, Silvia
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Severinson Eklundh, Kerstin
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Loutfi, Amy
    Örebro universitet, Institutionen för naturvetenskap och teknik.
    Towards measuring quality of interaction in mobile robotic telepresence using sociometric badges2013Ingår i: Paladyn - Journal of Behavioral Robotics, ISSN 2080-9778, E-ISSN 2081-4836, Vol. 4, nr 1, s. 34-48Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The field of mobile robotic telepresence for social communication is in rapid expansion and it is of interest to understand what promotes good interaction. In this paper, we present the results of an experiment where novice users working in health care were given a guided tour while maneuvering a mobile robotic telepresence system for the first time. In a previous study, it was found that subjective presence questionnaires and observations of spatial configurations based on Kendon’s F-formations were useful to evaluate quality of interaction in mobile robotic telepresence. In an effort to find more automated methods to assess the quality of interaction, the study in this paper used the same measures, with the addition of objective sociometric measures. Experimental results show that the quantitative analysis of the sociometric data correlates with a number of parameters gathered via qualitative analysis, e.g. different dimensions of presence and observed problems in maneuvering the robot.

  • 49.
    Larsson, Thomas
    et al.
    Mälardalens högskola, Institutionen för datavetenskap och elektronik.
    Akenine-Möller, Tomas
    Lund University, Sweden.
    Lengyel, Eric
    Terathon Software.
    On Faster Sphere-Box Overlap Testing2007Ingår i: Journal of graphics tools, ISSN 2165-347X, Vol. 12, nr 1, s. 3-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present faster overlap tests between spheres and either axis-aligned or oriented boxes. By utilizing quick rejection tests, faster execution times are observed compared to previous techniques. In addition, we present alternative vectorized overlap tests, which are compared to the sequential algorithms. Source code is available online.

  • 50.
    Lenander, Per
    et al.
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Fosselius, Anton
    Mälardalens högskola, Akademin för innovation, design och teknik.
    ORGFX: a Wishbone compatible Graphics Accelerator for the OpenRISC processor2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Modern embedded systems such as cellphones or medical instrumentation use increasingly complex graph-ical interfaces. Currently there are no widely used open hardware solutions to accelerate embedded graphicalapplications. This thesis presents the ORSoC graphics accelerator (ORGFX), an open hardware graphics ac-celerator that can be used with programmable hardware. A standalone software implementation is providedto help for a quick development of accelerated applications.The accelerator is able to render 2D, 3D and vector graphics. The example implementation of theORGFX is integrated with the OpenRISC Reference Platform System on Chip version 2 (ORPSoCv2). Thenal implementation runs on a Xilinx FPGA at 50 MHz, and provides accelerated graphics output froman HDMI port. An extensive software driver and a set of utilities to ease development for the graphicsaccelerator are provided along with the hardware. The software implementation of the accelerator uses thesame API as the hardware drivers, making it possible to quickly develop applications for the acceleratorwithout access to a physical platform.The nal implementation trades performance against platform independence and generality. The com-ponent can be integrated with any CPU or memory chip and works alongside a custom display core thatrenders the output to an external screen. The software drivers can be run bare metal or modied to run onan operating system.All of the hardware and software developed in this project is provided as open source under the GNULesser General Public License (LGPL), and can be downloaded from www.opencores.com. The authorshope that future releases will be integrated as a standard component into the OpenRISC Reference PlatformSystem on Chip.

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