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  • 1.
    Abbas, Azhar
    Karlstad University, Faculty of Technology and Science.
    GPIB- kommunikation och PID reglering med LabVIEW2009Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    LabVIEW ger en snabb och enkel tillgång till att styra instrument och en mycket stor databas med drivrutiner för DAQ-kort och olika datorgränssnitt (GPIB, serie, osv.).

    Många instrument och datorer kan anslutas till GPIB-bussen.  Detta kan ge en praktisk modell för utveckling av instrumentets styrprogram i LabVIEW med hjälp av GPIB-gränssnittet.

    Ett program i LabVIEW 8.2 med hjälp av GPIB-bussen kan kopplas till t.ex. multimetern (HP-34401A) för att mäta och visa multimeters noggrannhet. Men på grund av fel i drivrutiner för GPIB-gränssnittet kunde jag inte köra programmet med GPIB-bussen.

    Genom att använda LabVIEW 8.2 med hjälp av DAQ-kort kan en PID-regleringsalgoritm simuleras. PID konstrueras med virtuella instrument som innehåller alla nödvändiga komponenter och utrustning som krävs för att reglera någon linjär eller olinjär process exempelvis att nivåreglera två tankar i serie. Här stöter vi på alla de grundläggande regulatorer och får möjlighet att bygga PID med LabVIEW på ett enkelt sätt. Det finns två metoder för att bygga PID. Den första är med matematiska funktioner och den andra är med ’’Simulations functions control’’. Arbetet visar att bägge metoderna fungerar bra för att lösa uppgiften jämfört med färdiga PID-controls på LabVIEW.

  • 2.
    Abbas, Muhammad Tahir
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Eklund, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Grinnemo, Karl-Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Impact of Tunable Parameters in NB-IoT Stack onthe Energy Consumption2019In: Proceedings of Fifteenth Swedish National Computer Networking Workshop (SNCNW), 2019Conference paper (Refereed)
    Abstract [en]

    This paper studies the impact of tunable parametersin the NB-IoT stack on the energy consumption of a user equipment(UE), e.g., a wireless sensor. NB-IoT is designed to enablemassive machine-type communications for UE while providing abattery lifetime of up to 10 years. To save battery power, most oftime the UE is in dormant state and unreachable. Still, duringthe CONNECTED and IDLE state, correct tuning of criticalparameters, like Discontinuous reception (DRX), and extendedDiscontinuous reception (eDRX), respectively, are essential to savebattery power. Moreover, the DRX and eDRX actions relate tovarious parameters which are needed to be tuned in order toachieve a required UE battery lifetime. The objective of thispaper is to observe the influence of an appropriate tuning ofthese parameters to reduce the risk of an early battery drainage

  • 3.
    Abdulhadi, Sami
    Karlstad University, Faculty of Technology and Science.
    ARM i inbyggt system: med prototyp2009Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Embedded systems has become more and more common in today's society. The embedded systems are included in almost everything today, from various vehicles to children's toys.

    Today's technology means that yesterday's solutions can be realised on a fraction of the area. More and more become surface mounted with smaller and more complex circuits. This is not always an advantage for the developers when assembling and soldering prototype circuit boards become a more difficult and/or an expensive process.

    The goal is to create an embedded system with an ARM-processor. The system will consist of USB-OTG, ethernet, various memory like FRAM and microSD and a display with touchscreen for user interface. The project includes everything from choice of components to test and verification with program code.

    The time was too short to include all the parts that was planned. The result of the project was a prototype card and two small program sequences, one that blinks the two light diodes on the card and one that writes a picture on the display.

    This embedded system is intended for evaluating ARM-processors by Mikrododakt AB.

  • 4.
    Ahlgren, Bengt
    et al.
    RISE SICS.
    Grinnemo, Karl-Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Arahamsson, Henrik
    RISE SICS.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Latency-aware Multipath Scheduling inInformation-centric Networks2019In: Proceedings of the Fifteenth Swedish National Computer Networking Workshop (SNCNW), Luleå, Sweden. 4-5 June 2019., 2019Conference paper (Refereed)
    Abstract [en]

    We present the latency-aware multipath schedulerZQTRTT that takes advantage of the multipath opportunities ininformation-centric networking. The goal of the scheduler is touse the (single) lowest latency path for transaction-oriented flows,and use multiple paths for bulk data flows. A new estimatorcalled zero queue time ratio is used for scheduling over multiplepaths. The objective is to distribute the flow over the paths sothat the zero queue time ratio is equal on the paths, that is,so that each path is ‘pushed’ equally hard by the flow withoutcreating unwanted queueing. We make an initial evaluation usingsimulation that shows that the scheduler meets our objectives.

  • 5.
    Ahlgren, Bengt
    et al.
    RISE SICS.
    Hurtig, Per
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Abrahamsson, Henrik
    RISE SICS.
    Grinnemo, Karl-Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Are MIRCC and Rate-based Congestion Control in ICN READY for Variable Link Capacity?2017Conference paper (Other academic)
    Abstract [en]

    Information-centric networking (ICN) has been introduced as a potential future networking architecture. ICN promises an architecture that makes information independent from lo- cation, application, storage, and transportation. Still, it is not without challenges. Notably, there are several outstanding issues regarding congestion control: Since ICN is more or less oblivious to the location of information, it opens up for a single application flow to have several sources, something which blurs the notion of transport flows, and makes it very difficult to employ traditional end-to-end congestion control schemes in these networks. Instead, ICN networks often make use of hop-by-hop congestion control schemes. How- ever, these schemes are also tainted with problems, e.g., several of the proposed ICN congestion controls assume fixed link capacities that are known beforehand. Since this seldom is the case, this paper evaluates the consequences in terms of latency, throughput, and link usage, variable link capacities have on a hop-by-hop congestion control scheme, such as the one employed by the Multipath-aware ICN Rate-based Congestion Control (MIRCC). The evaluation was carried out in the OMNeT++ simulator, and demonstrates how seemingly small variations in link capacity significantly deterio- rate both latency and throughput, and often result in inefficient network link usage. 

  • 6.
    Ahlgren, Bengt
    et al.
    RISE SICS.
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Abrahamsson, Henrik
    RISE SICS.
    Grinnemo, Karl-Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    ICN Congestion Control for Wireless Links2018In: IEEE WCNC 2018 Conference Proceedings / [ed] IEEE, New York: IEEE, 2018Conference paper (Refereed)
    Abstract [en]

    Information-centric networking (ICN) with its design around named-based forwarding and in-network caching holds great promises to become a key architecture for the future Internet. Still, despite its attractiveness, there are many open questions that need to be answered before wireless ICN becomes a reality, not least about its congestion control: Many of the proposed hop-by-hop congestion control schemes assume a fixed and known link capacity, something that rarely – if ever – holds true for wireless links. As a first step, this paper demonstrates that although these congestion control schemes are able to fairly well utilise the available wireless link capacity, they greatly fail to keep the link delay down. In fact, they essentially offer the same link delay as in the case with no hop-by-hop, only end- to-end, congestion control. Secondly, the paper shows that by complementing these congestion control schemes with an easy- to-implement, packet-train link estimator, we reduce the link delay to a level significantly lower than what is obtained with only end-to-end congestion control, while still being able to keep the link utilisation at a high level. 

  • 7.
    Ahlquist, Ulrika
    Karlstad University, Division for Information Technology.
    Trådlöst elektriskt lås2007Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med examensarbetet är att göra en trådlös version av det elektriska lås som tillverkas av Electec System AB.

    För att göra ett trådlöst elektriskt lås måste ett batteri monteras i låset. Batteriet måste hållas uppladdat hela tiden för att kunna driva motorn och ge strömförsörjning till elektroniken i låset. Alla signaler mellan låset och styrenheten ska dessutom överföras trådlöst istället för med kabel. Signalerna måste kodas innan sändning så att ingen obehörig kan läsa signalen och sedan öppna dörren.

    Det svåraste i ett trådlöst elektriskt lås är att överföra effekt från dörrkarmen till låset eftersom utrymmet är begränsat och avståndet mellan låsblecket i karmen och låset i dörren kan uppgå till 10 mm. För att överföra effekt från dörrkarmen till låset konstruerades en transformator. Förlusterna i transformatorn ökar kraftigt då luftgapet ökas.

    Det visar sig att motor och övriga kretsar kan drivas med ett avstånd mellan kärnorna på upp till 7 mm. Luftgapet kan sannolikt ökas när andra transformatorkärnor används. Dessa fanns dock inte tillgängliga under examensarbetets gång på grund av lång leveranstid. I jämförelse med överföring av effekt är problemet att koda och överföra signaler mellan styrenheten och låset enklare och kan lösas med hjälp av färdiga kretsar.

  • 8.
    ahmad, waqas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Development of algorithm for li-ion batteries in electric vehicles, taking into account SOC, charge control, cell balancing and SOF.2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 9.
    Ahmadi, Fatemeh
    et al.
    Karlstad University.
    Dahlgren, Kim
    Karlstad University.
    Karlsson Solaiman, Ari
    Karlstad University.
    Rabitsch, Alexander
    Karlstad University.
    Adding support for NEAT to iperf32018Report (Other academic)
    Abstract [en]

    NEAT is an ongoing project which aims to re-enable the evolution ofthe transport layer of the Internet while at the same time providing aneasy to use API for developers of networked software. Researchers behindthe NEAT project has expressed an interest in a trac generator whichutilizes the NEAT framework in order to more easily conduct experiments,however, no such trac generator has previously been available. The goalof this project was to deliver a working implementation of NEAT in iperf3.This report covers the overall design, implementation and design decisionsmade during the project.

  • 10.
    Ahmed, Faisal Mahmood
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Estimated Droop Control for Parallel Connected Voltage Source Inverters: Stability Enhancement2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Renewable Energy Sources (RES) are considered as the replacement of conventionalenergy sources. These RES can use wind energy, solar light, bio waste and can alsobe in the form of small hydro power units. These RES has very poor power qualityand contains voltage uctuations and variable frequency. These factors make RES astability risk for the main utility grid. As a solution, currently inverters with dierentdesign techniques are being used as an interface between RES and main utility grid. Thecurrent study proposed a new technique "estimated droop control" for inverter design.The conventional droop control technique which was already used in inverter design, hasdiculty in synchronizing parallel connected inverters with dierent droop gains and lineimpedances. The proposed "estimated droop control" does not use any predened droopvalues for inverters and all inverters are responsible for the estimation of their own droopvalues with respect to their output power. Therefore, inverters are not bound to usesame and static droop values which are considered as a vital communication link. Theproposed design methodology has made inverters independent from this only virtual linkof communication due to which the reliability of a system has increased. The proposeddesign technique has given very good results in a simulation run. When the Simulinkmodel was run in parallel connected inverter with dierent line impedances, it was asuccess as both inverters started operating with same droop values as they were sharingan equal load. The most important test was with dierent line impedances because inconventional droop control it is dicult for inverters to keep their synchronism withdierent line impedances and an unequal load sharing make inverters to deviate fromtheir nominal values and to generate dierent tracking signals for each set. This problemhas been successfully solved with estimated droop control as in this method each inverterset its droop gains according to its output power, which helps an inverter to operate atnominal values with dierent droop gains and line impedance.

  • 11.
    Ahmed, Naeem
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Cooperative Spectrum Sensing for Cognitive Radio Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The great developments in the field of wireless communications that has been accelerated by the commercial need for better services has led to the application of wireless systems in many fields of life. The effect of wireless technology is much widened, like for safety applications, home automation, smart grid control, medical wearable, embedded wireless devices, entertainment systems etc.

    Direct and indirect surveillance of spectrum treatment has acknowledged the sequential and spatial accessibility of spectrum inside allocated frequency bands. This implies that spectrum deficiency is becoming a main problem. Therefore, spectrum deficiency problem arises here in terms of that most of the licensed primary users are not using their spectrum due to any reason of either geographical variation or temporal basis, and lot of allotted spectrum is unused and under-utilized. Moreover, along with spectrum deficiency problem, other issues are also linked like interference caused by secondary unlicensed users to primary licensed users while sharing the work load among each others, and problem of vacating the spectrum band in less fewer time frames after primary users detection.

    Cognitive networks assure to tackle these spectrum deficiency and other associated problems by accommodating secondary (unlicensed) users, in the spectrum region which is under-utilized. Spectrum Sensing is the prime motivation for cognitive radio and ensures that secondary (unlicensed) users do not propose unbearable levels of interference to primary (licensed) users.

    Cooperative Spectrum Sensing methodologies are still an open window of research. This work is related to cope up the problem of spectrum deficiency and associated problems, by developing an approach for establishment of grouping/clustering between secondary users in a cooperative spectral environment. This approach ensures that members within a group are highly correlated. As a result, the workload on each sensing node within a group is reduced. The effectiveness of this approach depends upon the accuracy of fused decision related to the presence or absence of primary (licensed) user at a particular band (50MHZ to 100MHZ). This approach also depends on the factor that time taken in sensing the primary (licensed) users should be less enough so that decision in vacating the band by the Cognitive Radio secondary users could be taken in fewer time frames. This latter metric is known to be ‘agility’, which eventually comes with the outcome of minimum interference to primary users via their early recognition.

  • 12.
    Ahmed, Umair
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Racing Driver Model in Dymola Vehicle Dynamics Library (VDL): Steering Controller Design2012Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Racing drivers always want to traverse path at vehicle’s maximum performance limits while keeping the vehicle at its ideal trajectory. The main objective of this report is to elaborate strategy for the path following problem in which driver has to follow the predefined 2D roads. New steering controller design for closed loop racing driver model in Dymola vehicle dynamics library is developed. The methodology proposed by Sharp et al. [2] is followed with the optimal velocity profile that tries to mimic the actions of the real drivers in real time scenarios. Vehicle handling limits i.e. longitudinal and lateral limits are defined before simulation. While travelling in the neighbourhood of optimal velocity on the straight road as well as during the curves, the performance of the steering controller is tested by conducting the test on J turn, Clothoid, Extended chicane and the closing curve path and also tested during the different environment effects e.g. when there is a side wind affecting the vehicle. Performance of existing and new steering controllers discussed and compared in result chapter. It is ensured that the drawbacks in the existing steering controller are eliminated by using the proposed methodology in new implemented steering controller.

    Key Words: Driver Model, Steering Controller, Path following, Velocity profile

  • 13.
    Aimal, Pir
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Mohsin, Main
    Analyzing Voltage control and reactive power support from full power converter wind turbine2011Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
  • 14.
    Alay, Özgü
    et al.
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    García, Rafael
    IMDEA Networks Institute, Spain.
    Peón Quirós, Miguel
    IMDEA Networks Institute, Spain.
    Mancuso, Vincenzo
    IMDEA Networks Institute, Spain.
    Hirsch, Thomas
    Celerway AS, Norway.
    Dely, Tobias
    Celerway AS, Norway.
    Werme, Jonas
    Celerway AS, Norway.
    Evensen, Kristian
    Celerway AS, Norway.
    Hansen, Audun
    Celerway AS, Norway.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Safari Khatouni, Ali
    Politecnico di Torino.
    Mellia, Marco
    Politecnico di Torino.
    Ajmone Marsan, Marco
    Politecnico di Torino.
    Monno, Roberto
    Nextworks, Italy.
    Lønsethagen, Håkon
    Telenor R&D, Norway.
    MONROE, a distributed platform to measure and assess mobile broadband networks: demo2016In: Proceedings of the Tenth ACM International Workshop on Wireless Network Testbeds, Experimental Evaluation, and Characterization, New York, NY, USA: Association for Computing Machinery (ACM), 2016, p. 85-86Conference paper (Refereed)
    Abstract [en]

    This demo presents the MONROE distributed platform and how it can be used to implement measurement and assessment experiments with operational mobile broadband networks (MBBs). MONROE provides registered experimenters with open access to hundreds of nodes, distributed over several European countries and equipped with multiple MBB connections, and a backend system that collects the measurement results. Experiments are scheduled through a user-friendly web client, with no need to directly access the nodes. The platform further embeds tools for real-time traffic flow analysis and a powerful visualization tool.

  • 15.
    Alay, Özgü
    et al.
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    Peón-Quirós, Miguel
    IMDEA Networks Institute, Spain.
    Mancuso, Vincenzo
    IMDEA Networks Institute, Spain.
    Hirsch, Thomas
    Celerway Communications, Norway.
    Evensen, Kristian
    Celerway Communications, Norway.
    Hansen, Audun
    Celerway Communications, Norway.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Safari Khatouni, Ali
    Politecnico di Torino, Italy.
    Mellia, Marco
    Politecnico di Torino, Italy.
    Ajmone Marsan, Marco
    IMDEA Networks Institute, Spain and Politecnico di Torino, Italy.
    Experience: An open platform for experimentation with commercial mobile broadband networks2017In: MobiCom '17 Proceedings of the 23rd Annual International Conference on Mobile Computing and Networking, New York: ACM Digital Library, 2017, p. 70-78Conference paper (Refereed)
    Abstract [en]

    Open experimentation with operational Mobile Broadband (MBB) networks in the wild is currently a fundamental requirement of the research community in its endeavor to address the need of innovative solutions for mobile communications. Even more, there is a strong need for objective data about stability and performance of MBB (e.g., 3G/4G) networks, and for tools that rigorously and scientifically assess their status. In this paper, we introduce the MONROE measurement platform: an open access and flexible hardware-based platform for measurements and custom experimentation on operational MBB networks. The MONROE platform enables accurate, realistic and meaningful assessment of the performance and reliability of 11 MBB networks in Europe. We report on our experience designing, implementing and testing the solution we propose for the platform. We detail the challenges we overcame while building and testing the MONROE testbed and argue our design and implementation choices accordingly. We describe and exemplify the capabilities of the platform and the wide variety of experiments that external users already perform using the system

  • 16.
    Alay, Özgü
    et al.
    Simula Research Laboratory, Norway.
    Lutu, Andra
    Simula Research Laboratory, Norway.
    Rafael, García
    IMDEA Networks Institute, Spain.
    Peón Quirós, Miguel
    IMDEA Networks Institute, Spain.
    Mancuso, Vincenzo
    IMDEA Networks Institute, Spain.
    Hirsch, Thomas
    Celerway AS, Norway.
    Tobias, Dély
    Celerway AS, Norway.
    Werme, Jonas
    Celerway AS, Norway.
    Evensen, Kristian
    Celerway AS, Norway.
    Fosselie Hansen, Audun
    Celerway AS, Norway.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Karlsson, Jonas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Brunström, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Safari Khatouni, Ali
    Politecnico di Torino, Italy.
    Mellia, Marco
    Politecnico di Torino, Italy.
    Ajmone Marsan, Marco
    Politecnico di Torino & IMDEA Networks, Italy.
    Monno, Roberto
    Nextworks, Italy.
    Lønsethagen, Håkon
    Telenor R&D, Norway.
    Measuring and Assessing Mobile Broadband Networks with MONROE2016In: 2016 IEEE International Symposium on a World of Wireless, Mobile, and Multimedia Networks (WoWMoM), Red Hook: IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    Mobile broadband (MBB) networks underpin numerous vital operations of the society and are arguably becoming the most important piece of the communications infrastructure. In this demo paper, our goal is to showcase the potential of a novel multi-homed MBB platform for measuring, monitoring and assessing the performance of MBB services in an objective manner. Our platform, MONROE, is composed of hundreds of nodes scattered over four European countries and a backend system that collects the measurement results. Through a user-friendly web client, the experimenters can schedule and deploy their experiments. The platform further embeds traffic analysis tools for real-time traffic flow analysis and a powerful visualization tool.

  • 17.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    A Case Study of Recent Mifare Classic Field Deployments From an (In-)Security Perspective2013In: Proceedings of the 21st International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2013), Split, Croatia: FESB, University of Split , 2013Conference paper (Refereed)
    Abstract [en]

    Mifare Classic is a very popular near-field communication technology that provides a shared-key, access-controlled, storage. Although the authentication protocol of Mifare Classic is compromised since half a decade, systems are still being deployed based on this technology, e.g. for access control systems and for public transport ticketing. By using commodity hardware, such as NFC enabled smartphones, by passing the security measures in some cases only require the installation and operation of a smartphone app. To this end, we present case studies of a number of recent Mifare Classic systems deployed during the last year, to serve as an illustration of practical security problems and to raise awareness thereof among NFC technology buyers and system implementors.

  • 18.
    Alfredsson, Stefan
    Karlstad University, Division for Information Technology.
    TCP in Wireless Networks: Challenges, Optimizations and Evaluations2005Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents research on transport layer behavior in wireless networks. As the Internet is expanding its reach to include mobile devices, it has become apparent that some of the original design assumptions for the dominant transport protocol, TCP, are approaching their limits. A key feature of TCP is the congestion control algorithm, constructed with the assumption that packet loss is normally very low, and that packet loss therefore is a sign of network congestion. This holds true for wired networks, but for mobile wireless networks non-congestion related packet loss may appear. The varying signal power inherent with mobility and handover between base-stations are two example causes of such packet loss. This thesis provides an overview of the challenges for TCP in wireless networks together with a compilation of a number of suggested TCP optimizations for these environments. A TCP modification called TCP-L is proposed. It allows an application to increase its performance, in environments where residual bit errors normally give a degraded throughput, by making a reliability tradeoff. The performance of TCP-L is experimentally evaluated with an implementation in the Linux kernel. The transport layer performance in a 4G scenario is also experimentally investigated, focusing on the impact of the link layer design and its parameterization. Further, for emulation-based protocol evaluations, controlled packet loss and bit error generation is shown to be an important aspect.

  • 19.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Bit Error Tolerant Multimedia Transport2004In: Perspectives on Multimedia: Communication, Media and Information Technology, Chichester: John Wiley & Sons, 2004, p. 175-191Chapter in book (Other academic)
  • 20.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    TCP-L: Allowing Bit Errors in Wireless TCP2003In: Proceedings of the 12th IST Summit on Mobile and Wireless Communications: Enabling a Pervasive Wireless World / [ed] Atílio Gameiro, Institute for Operations Research and the Management Sciences (INFORMS), 2003, p. 149-154Conference paper (Refereed)
    Abstract [en]

    This paper presents a technique to improve the performance of TCP and the utilization of wireless networks.Wireless links exhibit high rates of bit errors, compared to communication over wireline or fiber. Since TCP cannotseparate packet losses due to bit errors versus congestion,all losses are treated as signs of congestion and congestionavoidance is initiated. This paper explores the possibility of accepting TCP packets with an erroneous checksum, toimprove network performance for those applications that can tolerate bit errors. Since errors may be in the TCP header aswell as the payload, the possibility of recovering the headeris discussed. An algorithm for this recovery is also presented.Experiments with an implementation have been performed,which show that large improvements in throughput can beachieved, depending on link and error characteristics.

  • 21.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    A 4G Link Level Emulator for Transport Protocol Evaluation2004In: Proceedings of The Second Swedish National Computer Networking Workshop (SNCNW), 2004, p. 19-23Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and networkemulator, based upon the "Wireless IP" 4G system proposalfrom Uppsala University and partners. In wireless fading down-links (base to terminals) link-level frames are scheduled andthe transmission is adapted on a fast time scale. With fastlink adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteractedat the physical and link layers. A purpose of the emulatoris to investigate the resulting interaction with transport layer protocols. The emulator is built on Internet technologies, andis installed as a gateway between communicating hosts. The paper gives an overview of the emulator design, and presentspreliminary experiments with three different TCP variants. The results illustrate the functionality of the emulator by showing theeffect of changing link layer parameters on the different TCP variants.

  • 22.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Cross-layer analysis of TCP performance in a 4G system2007In: Proceedings of the 15th International Conference on Software, Telecommunications and Computer Networks, IEEE Computer Society, 2007Conference paper (Refereed)
    Abstract [en]

    This paper presents results from an experimental study of TCP in a wireless 4G evaluation system. Test-bed results on transport layer performance are presented and analyzed in relation to several link layer aspects. The aspects investigated are the impact of channel prediction errors, channel scheduling, delay, and adaptive modulation switch level, on TCP performance. The paper contributes a cross-layer analysis of the interaction between symbol modulation levels, different scheduling strategies, channel prediction errors and the resulting frame retransmissions effect on TCP. The paper also shows that highly persistent ARQ with fast link retransmissions do not interact negatively with the TCP retransmission timer even for short round trip delays.

  • 23.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Emulation and Validation of a 4G System Proposal2005In: Proceedings of RadioVetenskap och Kommunikation 2005: Volume II, 2005, p. 357-362Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and network emulator,along with experiments and validation against the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at thephysical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the link layer. The paper gives an overview of the emulator design, and presents experimental results with three different TCP variants in combination with various link layer characteristics.

  • 24.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Impact of 4G Wireless Link Configurations on VoIP Network Performance2008In: Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems, IEEE Communications Society, 2008, p. 708-712Conference paper (Refereed)
    Abstract [en]

    The performance of applications in wireless networks is partly dependent upon the link configuration. Link characteristics varies with frame retransmission persistency, link frame retransmission delay, adaptive modulation strategies, coding, and more. The link configuration and channel conditions can lead to packet loss, delay and delay variations, which impact different applications in different ways. A bulk transfer application may tolerate delays to a large extent, while packet loss is undesirable. On the other hand, real-time interactive applications are sensitive to delay and delay variations, but may tolerate packet loss to a certain extent. This paper contributes a study of the effect of link frame retransmission persistency and delay on packet loss and latency for real-time interactive applications. The results indicate that a reliable retransmission mechanism with fast link retransmissions in the range of 2-8 ms is sufficient to provide an upper delay bound of 50 ms over the wireless link, which is well within the delay budget of voice over IP applications.

  • 25.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Transport Protocol Performance over 4G Links: Emulation Methodology and Results2006In: Proceedings of the International Symposium on Wireless Communication Systems (ISWCS), IEEE Computer Society, 2006, p. 327-332Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and network emulator for the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at the physical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the physical/link layer in such a downlink. The paper introduces the Wireless IP system, describes the emulator design and implementation, and presents experimental results with TCP in combination with various physical/link layer parameters. The impact of link layer ARQ persistency, adaptive modulation, prediction errors and simple scheduling are all considered.

  • 26.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Impact of TCP Congestion Control on Bufferbloat in Cellular Networks2013In: Proceedings of the 14th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2013) / [ed] Angelos Lazaris, Balaji Rengarajan, IEEE Press, 2013Conference paper (Refereed)
    Abstract [en]

    The existence of excessively large and too filled network buffers, known as bufferbloat, has recently gained attention as a major performance problem for delay-sensitive applications. One important network scenario where bufferbloat may occur is cellular networks.

    This paper investigates the interaction between TCP congestion control and buffering in cellular networks. Extensive measurements have been performed in commercial 3G, 3.5G and 4G cellular networks, with a mix of long and short TCP flows using the CUBIC, NewReno and Westwood+ congestion control algorithms. The results show that the completion times of short flows increase significantly when concurrent long flow traffic is introduced. This is caused by increased buffer occupancy from the long flows. In addition, for 3G and 3.5G the completion times are shown to depend significantly on the congestion control algorithms used for the background flows, with CUBIC leading to significantly larger completion times.

  • 27.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Observations of Bufferbloat in Swedish Cellular Networks2013In: Proceedings of the 9th Swedish National Computer Networking Workshop (SNCNW 2013) / [ed] Bengt Ahlgren, 2013Conference paper (Refereed)
  • 28. Ali, A
    et al.
    Hoagg, J. B
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bernstein, D. S
    Growing window recursive quadratic optimization with variable regularization2010Conference paper (Refereed)
  • 29.
    Ali, Asad A.
    et al.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    Hoagg, Jesse B.
    Univ Kentucky, Dept Mech Engn, 151 Ralph G Anderson Bldg, Lexington, KY 40507 USA..
    Mossberg, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Bernstein, Dennis S.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    On the stability and convergence of a sliding-window variable-regularization recursive-least-squares algorithm2016In: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 30, no 5, p. 715-735Article in journal (Refereed)
    Abstract [en]

    A sliding-window variable-regularization recursive-least-squares algorithm is derived, and its convergence properties, computational complexity, and numerical stability are analyzed. The algorithm operates on a finite data window and allows for time-varying regularization in the weighting and the difference between estimates. Numerical examples are provided to compare the performance of this technique with the least mean squares and affine projection algorithms. Copyright (c) 2015 John Wiley & Sons, Ltd.

  • 30.
    Ali, Nour
    et al.
    Brunel University, London, UK.
    Baker, Sean
    University of Limerick, Ireland.
    O'Crowley, Ross
    Red Orkid Limited, Dublin, Ireland.
    Herold, Sebastian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Buckley, Jim
    University of Limerick, Ireland.
    Architecture consistency: State of the practice, challenges and requirements (vol 23, pg 224, 2018)2018In: Journal of Empirical Software Engineering, ISSN 1382-3256, E-ISSN 1573-7616, Vol. 23, no 3, p. 1868-1869Article in journal (Refereed)
  • 31.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    SDN Enhanced Ethernet VPN for Data Center Interconnect2017In: 2017 IEEE 6th International Conference on Cloud Networking (CloudNet) / [ed] Maga, D, IEEE, 2017, p. 77-82Conference paper (Refereed)
    Abstract [en]

    Ethernet Virtual Private Network (EVPN) is an emerging technology that addresses the networking challenges presented by geo-distributed Data Centers (DCs). One of the major advantages of EVPN over legacy layer 2 VPN solutions is providing All-Active (A-A) mode of operation so that the traffic can truly be multi-homed on Provider Edge (PE) routers. However, A-A mode of operation introduces new challenges. In the case where the Customer Edge (CE) router is multi-homed to one or more PE routers, it is necessary that only one of the PE routers should forward Broadcast, Unknown unicast, and Multicast (BUM) traffic into the DC. The PE router that assumes the primary role for forwarding BUM traffic to the CE device is called the Designated Forwarder (DF). The proposed solution to select the DF in the EVPN standard is based on a distributed algorithm which has a number of drawbacks such as unfairness and intermittent behavior. In this paper, we introduce a Software-Defined Networking (SDN) based architecture for EVPN support, where the SDN controller interacts with EVPN control plane. We demonstrate how our solution mitigates existing problems for DF selection which leads to improved EVPN performance.

  • 32. Alm, Magnus
    et al.
    Fauhlér, Robert
    Nätplanering på Fortum Distribution2012Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
  • 33.
    Alpmarken, Ia
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Studie av tekniska och ekonomiska fördelar av olika lösningar vid instrumentinstallation2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Inom industrin är tendensen att allt mer arbete automatiseras för snabbare, mer kostnadseffektiv samt exaktare tillverkning eller bearbetning. Vid automatisering av en processindustri möts konstruktören av ett flertal utmaningar, i minst att välja vilken installationsmetod som skall användas i det aktuella fallet.Vid en ombyggnation eller tillbyggnad av en existerande processindustri finns ofta begränsningar som styr vilken installationsmetod som kan användas, kunden kan exempelvis önska att den nya installationen utförs på liknande sätt som den tidigare.En nyinstallation kan däremot ge att konstruktören har möjlighet att själv påverka installationsmetod.

    I samarbete med Sweco Industry, ett konsultbolag som bland annat ägnar sig åt att konstruera system för processtyrning åt kunder, samt Valmet, ett företag som konstruerar anläggningar för tillverkning av mjukpapper, har därför en studie utförts för att studera vilken typ av installation som är mest kostnadseffektiv för ett uppbyggt typfall.

    Detta har utförts genom att planera fem installationer för det uppbyggda fallet och jämföra dess delkostnader samt totalkostnader.

    Den installationsmetod som påvisat lägst totalkostnad är en installation med distribuerade I/O-moduler anslutna till styrsystemet via PROFIBUS DP fältbuss.

    Trots en något högre totalkostnad rekommenderas dock en installation medelst fältinstrument anslutna till en fältbuss av lägre nivå då detta medför en störningssäker kommunikation och ger en tidseffektiv installation.

  • 34.
    Anderson, Collin
    et al.
    University of Pennsylvania, USA.
    Winter, Philipp
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    -, Roya
    Global Network Interference Detection over the RIPE Atlas Network2014Conference paper (Refereed)
    Abstract [en]

    Existing censorship measurement platforms frequentlysuffer from poor adoption, insufficient geographic coverage, and scalability problems. In order to outline ananalytical framework and data collection needs for futureubiquitous measurements initiatives, we build on top ofthe existent and widely-deployed RIPE Atlas platform.In particular, we propose methods for monitoring thereachability of vital services through an algorithm thatbalances timeliness, diversity, and cost. We then use Atlas to investigate blocking events in Turkey and Russia.Our measurements identify under-examined forms of interference and provide evidence of cooperation betweena well-known blogging platform and government authorities for purposes of blocking hosted content.

  • 35.
    Andersson, Gustaf
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Karlstad Business School.
    En Kvalitativ studie om förändringsarbete vid ett IT-projekt: En fallstudie på en segelflygklubb2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Organisationer och ledare saknar ofta en förståelse om kärnan i ett förändringsarbete, förståelsen om hur människor fungerar. Förändring leder ofta till starka känslor och vissa drabbas hårdare än andra, medarbetare kan lätt omvandlas till motståndare om ledningen inte möter personalen rätt.

     

    Syftet med denna uppsats är att ge en kunskapsbas i hur en projektgrupp ska arbeta mot användare för att motivera dem till en positiv inställning inför förändringen. Den ger en förståelse för människors behov, drivkrafter och olika orsaker till varför motstånd till förändring kan uppstå hos de berörda.

    Datainsamlingen har skett genom en litteraturstudie inom området för att sedan samla in empiri genom halvstrukturerade intervjuer. Samtliga respondenter kommer från en segelflygsförening och syftet med det var att ta reda på hur föreningen hanterat olika förändringsarbeten. Dels ett redan avslutat förändringsarbete då de övergick till ett system för internetbokning av flygplan och även ett förändringsarbete som inte realiserats än, en digital lösning till deras tidsrapportering.

     

    Det finns flera olika alternativ som en ledare kan applicera för att motivera sina anställda vid ett förändringsarbete. Dessa tillvägagångssätt kan vara effektiva på sina egna vis, mycket beroende på sammanhanget och det specifika fallet. För att effektivisera momentet motivation gäller det att välja rätt tillvägagångssätt vid rätt tillfälle. Något som förutsätter att ledare har en förståelse för individen och de reaktioner denne har gentemot förändringen.

  • 36.
    Andersson, Göran
    Karlstad University, Division for Information Technology.
    Synchronized Clock2007Independent thesis Basic level (professional degree), 10 points / 15 hpStudent thesis
    Abstract [en]

    For this project I was planning to construct a clock that could be synchronized with an external source. The clock should be able to keep the time between synchronizations as these may be sparse. It also needed to be able to store the current time in a memory and keep a register of stored times. The current time and the register must be viewable by the user and the clock must also have the ability to count down the last five seconds prior to a minute selected by the user. I have performed this work at home with my own equipments.

    As an external source for the synchronization I have chosen the DCF-77 clock signal broadcasted from Germany. To receive this signal I used a cheap AM receiver built specifically for this purpose. For the actual clock I used a PIC microcontroller which I programmed in C. The chip had all I needed including an oscillator and a RAM memory. I also connected a 3x16 character LCD display to the clock as well as 4 1-pole buttons for the user interface.

    The program is built upon an interrupt routine that with help of an internal timer is set to execute once every hundreds of a second. During this interrupt routine all other functions are executed. These functions include a DCF decoder, an internal clock to keep the time, an LCD driver and a user interface.

    I have managed to read the clock signal from the receiver but due to interferences from the computer I used to program the PIC chip, I have not been able to get any good reception close to the computer. Apart from this setback the clock works as it should and it meets all other criteria.

  • 37.
    Andersson, Jan-Olof
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Larsson, Samuel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Tobias, Sjöholm
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Implementation of the NEAT Policy Manager2019Report (Refereed)
    Abstract [en]

    The NEAT system was developed in 2017 to increase flexibility in the choice of network transport protocol being used. One of the most important components of the NEAT system is the Policy Manager (PM), which determines what protocol is to be utilized by the application. The PM is written in Python while the rest of the NEAT system is C-based, so a natural evolution of the PM is to perform a functional translation of it to C. While the main goal was solely to develop a fully functional C-based PM, the difference in programming languages in the end also brought a performance increase of 28 times compared with the Python-based PM. There are still a few improvements left to do in the PM, but it is already a notable improvement for the NEAT system as a whole.

  • 38.
    Andersson, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Jansson, Ulf
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Analys av solcellsanläggningar påverkan på elnätet2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Sammanfattning

    Examensarbetet handlar om vilka effekter mikroproduktion i form av solcellsenheter har och kommer att ha på Karlstads elnät. Via flera mätserier har här sammanställts vad som händer med elkvaliteten i nätet och vilka krav som ställs på elnätsbolag och framtida mikroproducenter. Genom bred teoretisk kunskap och praktiskt arbete med ett antal dataprogram har denna rapport arbetats fram och sammanställts. Vid ett flertal tillfällen har upphovsmännen bakom denna rapport gett sig ut i fält för att på plats ta del utav dagens former av solkraft samt också iakttagit arbetet bakom och inför elkvalitetsundersökningar.Syftet har i grunden varit att ge kunskap inför ökande volymer av mikroproduktion och att förbereda för framtida förändringar och ombyggnationer i det lokala elnätet. Arbetet har resulterat i en tydlig bild av att dagens elnät har goda möjligheter att möta en ökning av producenter med låga produktionsnivåer. Det har konstaterats att försiktighet bör tas vid inkoppling av anläggningar vad gäller enfas och trefas. Eftersträvansvärt är att använda trefasinkoppling för att undvika snedbelastningar i nätet.

  • 39.
    Andersson, Marcus
    et al.
    Karlstad University.
    Arvidsson Nordgård, Elias
    Karlstad University.
    Statisk ljudtryckssensor: Att konstruera ett mobilt mätsystem för vapenindustrin2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Bofors Test Center has during recent years gained increased critiques concerning loud sound levels associated with their daily activities, which mainly comprises test firing of newly developed weapons and ammunition. The noise that occurs sometimes result in discomfort for the public, with complaints as a consequence. In the long run this could lead to the county administrative board establishing limits or demanding the company to control the noise levels they cause. If the company could prevent the authority’s eventual demands by registering the sound levels overtime, then this will be seen as a guarantee for the company to continue with the same activities they do today.The purpose with this thesis is to produce a mobile unit to measure and log all values that exceed the threshold set at 80 dBC. Bofors Test Center should later have the opportunity to produce more copies of this unit to be placed permanently or mobile within Bofors Test Centers neighboring if desired.To achieve this we had to investigate controller, power supply, sensor and logging. Communication between the unit and a server was excluded since the project would become too big.The final product is a unit that saves its measured peak-values on a USB-stick and types out the highest and latest measured value on a display.

  • 40.
    Andersson Nyrén, Martina
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Karlstad Business School.
    Pilotstudier avanvändargränssnitt till app för smärtpatienter2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Experio Lab i Landstinget i Värmland, Karolinska Institutet och Kungliga TekniskaHögskolan håller i dag på med att utveckla en digital tjänst i form av en app försmärtpatienter. Målet är att genom en digital tjänst kunna lära sig mer om hur patienter kankartlägga sina besvär inför ett möte med sjukvården.

    Uppsatsen syftar till att inför kommande användbarhetstester på riktiga patienterundersöka hur väl prototypen fungerar när det kommer till gränssnittet och ge förslag somskulle kunna förbättra appen inför de kommande användbarhetstesterna.

    Undersökningen genomfördes i två steg: Först testades appen som en pappersprototyp.Därefter genomfördes användbarhetstester med hjälp av studenter och experter inomtjänstedesign på en ipad-platta, där både intervjuer och observationer gjordes. Resultatetvisade att flera av testpersonerna hade samma sorts svårigheter när det kom till att interageramed appen. Svårast var att rita sina besvär på besvärsteckningen samt att veta var i processenman befann sig. Efter genomförande av studien uppgav de flesta testpersonerna att de skullerekommendera appen till någon de kände. Majoriteten såg även behov av att appensanvändargränssnitt blir tydligare för användaren.

  • 41.
    Andersson, Stefan
    et al.
    Karlstad University, Faculty of Technology and Science.
    Johansson, Andreas
    Karlstad University, Faculty of Technology and Science.
    Tillämpning av effektstabilisering i PLC2008Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of the degree project is to make a digital realization of a stabilizer for oscillations in the active power from a hydropower synchronous generator, connected to a power network.

    The implementation is supposed to be done in a PLC which already handles part of the excitation system.

    The power stabilization is achieved by sending a counteracting reference signal to the excitation system which controls the generator’s output power. This counteracting signal can be achieved in several ways.

    Two existing models, standardized by IEEE, for power system stabilizing will be examined, PSS1A and PSS2B.

    A Simulink-model of a distribution net with a generator is constructed to test the stabilizers.

    To perform a digital implementation a discrete transformation of one continuous model is done. This discrete model is also tested to verify the function in comparison to the continuous one.

    The discrete model is reorganized in a form possible to implement in the PLC.

    Comparison between the simulated and the implemented model is made by measurement.

  • 42.
    Angulo, Julio
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Karlstad Business School.
    Designing for Usable Privacy and Transparency in Digital Transactions2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    People engage with multiple online services and carry out a range of different digital transactions with these services. Registering an account, sharing content in social networks, or requesting products or services online are a few examples of such digital transactions. With every transaction, people take decisions and make disclosures of personal data. Despite the possible benefits of collecting data about a person or a group of people, massive collection and aggregation of personal data carries a series of privacy and security implications which can ultimately result in a threat to people's dignity, their finances, and many other aspects of their lives. For this reason, privacy and transparency enhancing technologies are being developed to help people protect their privacy and personal data online. However, some of these technologies are usually hard to understand, difficult to use, and get in the way of people's momentary goals.

    The objective of this thesis is to explore, and iteratively improve, the usability and user experience provided by novel privacy and transparency technologies. To this end, it compiles a series of case studies that address identified issues of usable privacy and transparency at four stages of a digital transaction, namely the information, agreement, fulfilment and after-sales stages. These studies contribute with a better understanding of the human-factors and design requirements that are necessary for creating user-friendly tools that can help people to protect their privacy and to control their personal information on the Internet.

  • 43.
    Angulo, Julio
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Information Systems and Project Management. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Usable Transparency through network representations and analyses2015In: The Future of Networked Privacy: Challenges and opportunities, 2015Conference paper (Refereed)
    Abstract [en]

    We explore how concepts from the field of network science can be employed to inform Internet users about the way their personal identifiable information (PII) is being used and shared by online services. We argue that presenting users with graphical interfaces that display information about the network structures that are formed by PII exchanges can have an impact on the decisions users take online, such as the services they choose to interact with and the information they decide release.

  • 44.
    Angulo, Julio
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Information Systems and Project Management.
    Fischer-Hübner, Simone
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Pulls, Tobias
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Ulrich, König
    HCI for Policy Display and Administration2011In: Privacy and Identity Management for Life / [ed] Jan Camenish, Simone Fischer-Hübner and Kai Rannenberg, Berlin: Springer Berlin/Heidelberg, 2011, 1, p. 261-277Chapter in book (Refereed)
    Abstract [en]

    The PrimeLife Policy Language (PPL) has the objective of helping end users make the data handling practices of data controllers more transparent, allowing them to make well-informed decisions about the release of personal data in exchange for services. In this chapter, we present our work on user interfaces for the PPL policy engine, which aims at displaying the core elements of a data controller's privacy policy in an easily understandable way as well as displaying how far it corresponds with the user's privacy preferences. We also show how privacy preference management can be simplified for end users.

  • 45.
    Angulo, Julio
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Fischer-Hübner, Simone
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Wästlund, Erik
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Psychology. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Economic Sciences, Communication and IT, Service Research Center.
    Pulls, Tobias
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Towards Usable Privacy Policy Display & Management: The PrimeLife Approach2011In: Proceedings of 5th International Symposium on Human Aspects of Information Security & Assurance / [ed] Steven Furnell, Plymouth: University of Plymouth , 2011, p. 108-118Conference paper (Refereed)
  • 46.
    Angulo, Julio
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Wästlund, Erik
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Social and Psychological Studies.
    Identity Management through “Profiles”: Prototyping an Online Information Segregation Service2013In: Human-Computer Interaction. Users and Contexts of Use: 15th International Conference, HCI International 2013, Las Vegas, NV, USA, July 21-26, 2013, Proceedings, Part III / [ed] Masaaki Kurosu, Springer Berlin/Heidelberg, 2013, Vol. 8006, p. 10-19Conference paper (Refereed)
    Abstract [en]

    Whereas in real everyday life individuals have an intuitive approach at deciding which information to disseminate to others, in the digital world it becomes difficult to keep control over the information that is distributed to different online services. In this paper we present the design of a user interface for a system that can help users decide which pieces of information to distribute to which type of service providers by allowing them to segregate their information attributes into various personalized profiles. Iterative usability evaluations showed that users understand and appreciate the possibility to segregate information, and revealed possible improvements, implications and limitations of such an interface.

  • 47.
    Arntsson, Timmy
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Elnätet och dess anpassning för elektriska fordon: En studie av hur ett lokalnät påverkas av ett ökat antal elektriska fordon2015Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The availability of non-renewable fuels is decreasing and therefore the prices of both petrol and diesel has increased in recent years. As a result more and more chooses to invest in cars powered by alternative fuels and the focus has long been on electric vehicles. However, this means greater weight on utility companies around the world which now have to adjust to a higher demand. The purpose of this study is to investigate how a local network are affected by electric car chargers and be able to describe the degree to which a low-voltage can be loaded with electric car chargers for commercial and private use, in order to provide recommendations for the future dimension of the local networks. Few studies have been conducted regarding electric cars from a network and supply perspective, but have instead been focused on energy storage in the actual vehicle. Therefore, this study has been processed with an electricity grid perspective.

    The intent of the study has been answered by both a measurement and several simulations. The study is based on Karlstad’s local electrical network and the commercial charging station Tesla in Våxnäs, Karlstad. The parameters of power quality for which this study has taken into account are load of the transformers, load loss, power factor, efficiency, voltage levels, voltage drop and asymmetry.

    The methodological conditions have led to a result that can be used as a basis for an expansion of electric cars, big or small. The measurement was of great support to get an overall view of how the characteristics of a charging session appeared and how the quality parameters were affected during high as well as low power charging. Limitations within the simulation program have led to the calculations to carry out in a more extreme scenario when it comes to the load. A result since the simulation time for constant power was minimum one hour.

    Based on the measurement and simulations of the charging station for commercial use is dimensioned well to cope with the current use of electric vehicle charging. More municipalities should follow Karlstad’s example for the development of commercial charging stations. In the countryside great problems occurred, especially with voltage drop at an increased use of home chargers for electric cars. The same problems emerged in the city part of the network. The study also showed serious problems with asymmetry in the city. The report concluded, therefore, several recommendations for the future dimension of local networks for private homes, for example that the local network should be divided into multiple trails.

  • 48.
    Arvidsson, Åke
    et al.
    Kristianstad University, Kristianstad, Sweden..
    Grinnemo, Karl-Johan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Chen, Eric
    Kristianstad University, Kristianstad, Sweden..
    Qinghua, Wang
    Kristianstad University, Kristianstad, Sweden..
    Brunström, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Web Metrics for the Next Generation PerformanceEnhancing ProxiesA°2019Conference paper (Refereed)
    Abstract [en]

    The fast growth of Internet traffic, the growingimportance of cellular accesses and the escalating competitionbetween content providers and network operators result in agrowing interest in improving network performance and userexperience. In terms of network transport, different solutionsranging from tuning TCP to installing middleboxes are applied.It turns out, however, that the practical results sometimes aredisappointing and we believe that poor testing is one of thereasons for this. Indeed, many cases in the literature limittesting to the simple and rare use case of a single file download,while common and complex use cases like web browsing oftenare ignored or modelled only by considering smaller files. Tofacilitate better testing, we present a set of metrics by whichthe complexity around web pages can be characterised andthe potential for different optimisations can be estimated. Wealso derive numerical values of these metrics for a small set ofpopular web pages and study similarities and differences betweenpages with the same kind of content (newspapers, e-commerceand video) and between pages designed for the same platform(computer and smartphone).

  • 49.
    Asplund, Katarina
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Partially Reliable Multimedia Transport2004Report (Other academic)
  • 50.
    Asplund, Katarina
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    The trade-off Between Latency and Image Quality: A User PerspectiveManuscript (preprint) (Other (popular science, discussion, etc.))
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