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  • 46401.
    Varela, Martin
    et al.
    RISE., Swedish ICT, SICS.
    Marsh, Ian
    RISE - Research Institutes of Sweden, ICT, SICS.
    Grönvall, Björn
    RISE., Swedish ICT, SICS.
    A Systematic Study of PESQ's Performance (from a Networking Perspective)2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we study, in a systematic way, how the behavior of PESQ estimations varies with the network loss process. We assess the variability of the estimations with respect to the network conditions and the speech content, and also their accuracy, by comparing the estimates with subjective assessments.

  • 46402.
    Vargas Chevez, Norman Antonio
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Johannesson, Paul
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Rusu, Lazar
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    A unified strategic business and IT alignment model: A study in the public universities of Nicaragua2010Ingår i: 16th Americas Conference on Information Systems (AMCIS 2010), AISeL , 2010Konferensbidrag (Övrigt vetenskapligt)
  • 46403.
    Vargas Chevez, Norman
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    A unified strategic business and IT alignment model: A study in the public universities of Nicaragua2010Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    A number of attempts have been made to define strategic business and information technology (IT) alignment; several representations of what it is are available in academic and practitioners’ fields. The literature suggests that firms need to achieve strategic business and IT alignment to be competitive. Strategic business and IT alignment impact business performance and IT effectiveness. We propose a unified strategic business and IT alignment model based on four strategic business and IT alignment models: Strategic Alignment Model (SAM), Strategic Alignment Maturity Model (SAMM), information system strategic alignment model and an operational model of strategic alignment. I argue that such a unified model will provide a better understanding of the nature and key aspects of strategic business and IT alignment from different, and sometimes complementary, theories. The unified model represents the concepts and instruments used in these four strategic businesses and IT alignment models. Our principal research goal is to pave the way to develop a common understanding between the different models. The components of the unified strategic business and IT alignment model were ranked with a group of IT experts and business experts from four public universities in Nicaragua. The result can be used as a basis for improving strategic business and IT alignment.

  • 46404.
    Vargas Chevez, Norman Antonio
    et al.
    Stockholms universitet, Samhällsvetenskapliga fakulteten, Institutionen för data- och systemvetenskap.
    Plazaola, Leonel
    Una representación consolidada del alineamiento estratégico de los negocios y las tecnologías de la información2007Ingår i: Nexo, ISSN 1818-6742, E-ISSN 1995-9516, Nexo, Vol. 20Artikel i tidskrift (Övrigt vetenskapligt)
  • 46405.
    Vargas Vargas, Fernando
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Cloudlet for the Internet-of- Things2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Med en befolkning som ökar i urbana områden, står många av världens städer inför utmaningar som ökande avgaser och trafikstockning. I ett försök att tackla sådana utmaningar, formulerar regeringar och stadsfullmäktige nya och innovativa strategier. Integrationen av ICT med dessa strategier bildar konceptet smart cities.

    Internet of Things (IoT) är en drivande faktor för smart city initiativ, vilket gör det nödvändigt för en IT infrastruktur som kan ta till vara på de många fördelar som IoT bidrar med. Cloudlet är en ny infrastrukturell modell som erbjuder datormolnskompetens i mobilnätverkets edge. Denna miljö karakteriseras av låg latens och hög bandbredd, utgörande ett nytt ekosystem där nätverksoperatörer kan hålla deras nätverks-edge öppet för utomstående, vilket tillåter att flexibelt och snabbt utveckla innovativa applikationer och tjänster för mobila subskribenter.

    I denna avhandling presenterar vi en cloudlet-arkitektur som framhäver edge computing, för att förse en plattform för IoT utrustning där många smart city applikationer kan utvecklas. Vi förser er först med en överblick av existerande utmaningar och krav i IoT systemutveckling. Sedan analyserar vi existerande cloudlet lösningar. Slutligen presenteras vår cloudlet arkitektur för IoT, inklusive design och en prototyplösning. För vår cloudlet-prototyp har vi fokuserat på en modell av mikroskala för att räkna ut CO2 emissioner per enskild resa med fordon, och implementerat en funktion som tillåter oss att läsa CO2 data från CO2 sensorer. Platsdata är inhämtad med hjälp av en Android smartphone och behandlas i cloudlet. Det hela sammanfattas med en prestandaevaluering.

  • 46406.
    Varghese, Benoy
    et al.
    NICTA and University of New South Wales (UNSW), Australia.
    Carlsson, Niklas
    Linköpings universitet, Institutionen för datavetenskap, Databas och informationsteknik. Linköpings universitet, Tekniska högskolan.
    Jourjon, Guillaume
    NICTA, Sydney, Australia.
    Mahanti, Anirban
    NICTA, Sydney, Australia.
    Shenoy, Prashant
    University of Massachusetts, USA.
    Greening Web Servers: A Case for Ultra Low-power Web Servers2014Ingår i: Proc. International Green Computing Conference (IGCC), IEEE Press, 2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the feasibility of running web servers on low-power micro-computing boards, with emphasis on analysing the tradeoffs between power and performance. Today, small-to-medium scale enterprises, NGOs, universities typically deploy an architecture where frontend servers deliver static content and backend servers the dynamic content.   Experimentation using an ARM-based Raspberry Pi system shows that, for static content, Raspberry Pi achieves similar response times to that of a typical tower server running on standard hardware.   Although, the Raspberry Pi is found unsuitable for serving dynamic content, our findings show that many of these small-to-medium scale organisations can achieve large energy savings by using low-power servers for serving the static content.

  • 46407. Vari, A
    et al.
    Linneroth-Bayer, J
    Brouwer, L
    Ekenberg, L
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Ferencz, Z
    The 1998 Upper Tisza Flood2003Rapport (Övrigt vetenskapligt)
  • 46408.
    Varisetty, Tilak
    et al.
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Edara, Praveen
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Systematic Overview of Savings versus Quality for H.264/SVC2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Efterfrågan på effektiva video kodningstekniker har ökat under de senaste åren, vilket resulterar i utvecklingen av olika tekniker videokomprimering. SVC (Scalable Video Coding) är den senaste ändringen av H.264/AVC (Advanced Video Coding), vilket ger en ny dimension genom att möjligheten att koda en videoström till en kombination av olika sub strömmar som är skalbara i områden som motsvarar rumslig upplösning, tidsupplösning och kvalitet. Introduktion av skalbarhet aspekten är en effektiv video kodningsteknik i ett nätverk scenario där kunden kan avkoda sub strömmen beroende på den tillgängliga bandbredden i nätverket. En elegant nedbrytning i videokvaliteten förväntas när någon av den rumsliga, tidsmässiga eller kvaliteten skiktet avlägsnas. Fortfarande mängden nedbrytning i videokvalitet måste mätas i termer "Quality of Experience" (QoE) från användarens perspektiv. För att mäta försämring i video-kvalitet, har videoströmmar består av olika rumsliga och tidsmässiga skikt hämtats och ansträngningar har lagts för att ta bort varje lager från ett högre beroende lager eller förbättrande lagret och slutar upp med den lägsta beroendet lagret eller basen skikt. Extraktion av ett tidsmässigt nedsamplas lager hade problem med ram interpolation och för att övervinna detta, var temporal interpolering används. På liknande sätt har en rumslig nedsamplas skikt har uppsamplas i rumsdomänen för att jämföra med den ursprungliga strömmen. Senare har en objektiv videokvalitet bedömning gjorts genom att jämföra den extraherade underströmmen med färre lager som nedsamplade både rumsligt och tidsmässigt med den ursprungliga strömmen innehållande alla lager. De genomsnittliga yttrande poäng (MOS) erhölls från objektivt verktyg som heter Perceptuell utvärdering av Videokvalitet (PEVQ). Experimentet utförs för varje skikt och även för olika test video. Subjektiva tester utfördes också för att utvärdera användarupplevelsen. Resultaten ger rekommendationer till SVC kapabel router om videokvaliteten för varje lager och därmed nätverket kodomvandlaren kan överföra ett visst lager beroende på nätverksförhållanden och kapacitet avkodnings anordningen.

  • 46409.
    Varisteas, Georgios
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    A compiler front-end for the WOOL Parallelization library2010Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    WOOL is a C parallelization library developed at SICS by Karl-Filip Faxén. It provides the tools for developing fine grained independent task based parallel applications. This library is distinguished from other similar projects by being really fast and light; it manages to spawn and synchronize tasks in under 20 cycles.

    However, all software development frameworks which expose radically new functionality to a programming language, gain a lot by having a compiler to encapsulate and implement them. WOOL does not differ from this category. This project is about the development of a source-to-source compiler for the WOOL parallelization library, supporting an extension of the C language with new syntax that implements the WOOL API, transforming it and eventually outputting GNU C code. Additionally, this compiler is augmented with a wrapper script that performs compilation to machine code by using GCC. This script is configurable and fully automatic.

    The main advantage gained from this project is to satisfy the need for less overhead in software development with WOOL. The simplified syntax results in faster and more economical code writing while being less errorprone. Moreover, this compiler enables the future addition of many more features not applicable with the current state of WOOL as a library.

  • 46410.
    Varisteas, Georgios
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Automatic Adaptation of Resources to Workload requirements in Nested Fork-join Programming Model2012Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We provide a work-stealing scheduling method for nested fork/join parallelism that is mathematically proven to self- adapt multiprogrammed applications resource allocation to the current workloads’ individual needs while it takes avail- able resources into account. The scheduling method both scales up the allocated resources when needed and down, when possible.The theoretical model has been implemented in the Bar- relfish distributed multikernel operating system and demon- strated to function on a simulated x86 64 multicore plat- form.The work presented here is the first step towards a com- plete framework for the system-wide scheduling and load balancing of multiprogrammed many-core systems, assum- ing a variety of workload types and guaranteeing at least av- erage execution for each running program.

  • 46411.
    Varisteas, Georgios
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    DVS: Deterministic Victim Selection to ImprovePerformance in Work-Stealing Schedulers2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Task-centric programming models offer a versatile method for exposing parallelism. Such programs are popularly deployed using work-stealing scheduling runtimes. Work-stealers have traditionally employed randomness dependent techniques, considered optimal for several execution configurations. We have identified certain inefficiencies and leeway for improvement on emerging parallel architectures and workloads of fluctuating parallelism. Our deterministic victim selection (DVS) for work-stealing schedulers was designed to provide controllable and predictable uniform distribution of tasks without degrading performance; stealing is restricted between specific pairs of workers. We experimentally show that DVS offers improved scalability and performance for irregular workloads. We demonstrate DVS on Linux and Barrelfish operating systems, using an 48 core Opteron system and a simulated ideal platform respectively. On real hardware, we observed better scaling and 13% average performance gains, up to 55% for specific irregular workloads.

  • 46412.
    Varisteas, Georgios
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Palirria: Accurate on-line parallelism estimation for adaptive work-stealing2014Ingår i: PMAM'14 Proceedings of Programming Models and Applications on Multicores and Manycore, ACM Press, 2014, s. 120-130Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present Palirria, a self-adapting work-stealing scheduling method for nested fork/join parallelism that can be used to estimate the number of utilizable workers and self-adapt accordingly. The estimation mechanism is optimized for accuracy, minimizing the requested resources without degrading performance. We implemented Palirria for both the Linux and Barrelfish operating systems and evaluated it on two platforms: a 48-core NUMA multiprocessor and a simulated 32-core system. Compared to state-of-the-art, we observed higher accuracy in estimating resource requirements. This leads to improved resource utilization and performance on par or better to executing with fixed resource allotments.

  • 46413.
    Varisteas, Georgios
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Towards automatic adaptation of resource requirements to actual workload for task-based programming models2012Konferensbidrag (Refereegranskat)
    Abstract [en]

    Given the considerate amounts of research on task-based parallel programming models for maximizing performance, this project tries to go one step further and investigate mul- tiprogrammed many-core systems. We provide a mathemat- ical model for a parallel runtime that automatically adapts the need for resources to the workload actually produced. The programming model developed is based on other well established models like Cilk++ and Wool.

    The paper concludes with two conditions that guarantee over-utilization and under-utilization of of the existing work- ers without having to capture eciency metrics periodically.

    The work presented here is the rst step towards a com- plete framework for the system-wide scheduling and load balancing of multiprogrammed many-core system, assuming a variety of workload types and guaranteeing at least average execution for each running program.

  • 46414.
    Varisteas, Georgios
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikation: Infrastruktur och tjänster, Programvaru- och datorsystem, SCS.
    Faxén, Karl-Filip
    SICS.
    Dynamic Inter-core Scheduling in Barrelfish: avoiding contention with malleable process domains2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Trying to attack the problem of resource contention, created by multiple parallel applications running simultaneously, we propose a space-sharing, two-level, adaptive scheduler for the Barrelfish operating system. The first level is system-wide, existing inside the OS, and has knowledge of the available resources, while the second level is aware of the parallelism in the application. Feedback on efficiency from the second-level to the first-level, allows the latter to adaptively modify the allotment of cores (domain) thus intelligently avoiding time-sharing. In order to avoid excess inter-core communication, the first-level scheduler is designed as a distributed service, taking advantage of the message-passing nature of Barrelfish. The processor topology is partitioned so that each instance of the scheduler handles an appropriately sized subset of cores. Malleability is achieved by suspending worker-threads. Two different methodologies are introduced and explained, each ideal for different situations.

  • 46415.
    Varisteas, Georgios
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Brorsson, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Faxén, Karl-Filip
    Resource management for task-based parallel programs over a multi-kernel.: BIAS: Barrelfish Inter-core Adaptive Scheduling2012Ingår i: Proceedings of the 2012 workshop on Runtime Environments, Systems, Layering and Virtualized Environments (RESoLVE’12), Association for Computing Machinery (ACM), 2012, s. 32-36Konferensbidrag (Refereegranskat)
    Abstract [en]

    Trying to attack the problem of resource contention, created by multiple parallel applications running simultaneously, we propose a space-sharing, two-level, adaptive scheduler for the Barrelfish operating system.The first level is system-wide, running close to the OS’ kernel, and has knowledge of the available resources, while the second level, integrated into the application’s runtime, is aware of its type and amount of parallelism. Feedback on efficiency from the second-level to the first-level, allows the latter to adaptively modify the allotment of cores (domain), intelligently promoting space-sharing of resources while still allowing time-sharing when needed.In order to avoid excess inter-core communication, the system-level scheduler is designed as a distributed service, taking advantage of the message-passing nature of Barrelfish. The processor topology is partitioned so that each instance of the scheduler handles an appropriately sized subset of cores.Malleability is achieved by suspending worker-threads. Two different methodologies are introduced and explained, each suitable for distinct programming models and applications.Preliminary results are quite promising and show minimal added overhead. In specific multiprogramming configurations, initial experiments proved significant performance improvement by avoiding contention.

  • 46416.
    Varland, Marcus
    et al.
    Linnéuniversitetet, Fakultetsnämnden för naturvetenskap och teknik, Institutionen för datavetenskap, fysik och matematik, DFM.
    Nygren, Caroline
    Motiv, möjligheter och framgångsfaktorer med RFID på lastbärare: Införande på Brunskoggruppen AB2012Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Gapet mellan större och mindre lokala aktörer på transportmarknaden ökar vilket leder till krav på kostnadseffektiva och differentierade verksamheter. Detta bidrar i allt högre grad till effektivisering och automatisering av verk­samhetens processer. Ett problem för verksamheter i logistiska samman­hang kan vara att lastbärare försvinner i leveransflödet vilket kan vara både kostsamt och reducera kundnöjdheten. RFID, Radio Frequency Identificat­ion är en teknik som kan användas i logistikprocesser för att ge en ökad synlighet på både lager-och logistik­aktiviteter i flödet från leverantör till kund. För att kunna driftsätta en sådan lösning och få tillgång till den tänkta nyttan bör de invol­verade aktörerna engageras i ett gemensamt system som kräver uppsättningen av en lämplig infrastruktur.

     Brunskoggruppen AB är ett mindre logistikföretag beläget i Ljungby som upplever ökade kostnader för förlorade lastbärare i leveransflödet och ett be­hov av effektivisering av informationsflödet gällande densamma.

    Syftet med denna studie var att genom litteraturstudier, intervjuer och inslag av aktionsforskning undersöka och ge ett exempel på hur Brunskoggruppen AB kan införa en automatiserad lösning för spårbarhet på lastbärare. Under­sök­ningen skulle även visa vilka motiv som fanns för ett införande av RFID, vilka framgångskritiska faktorer som kan påverka ett införande och vilka förändringar som kan åstadkommas jämfört med dagens system i verksamheten.Resultatet visar hur förväntningar och motiv kan påverka att en teknik antas och hur den införs i verksamheten. Motiv för införande är en ökad effekti­vitet vid automatisering av de interna processerna tillsammans med att tek­niken skapar affärsmöjligheter för unika kundlösningar. De riktlinjer som tagits fram för införandeprocessen på Brunskoggruppen AB sammanfattas i åtta steg.

  • 46417.
    Varland, Viktor
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för för interaktion och systemdesign.
    Karlsson, Mikael
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för för interaktion och systemdesign.
    Utvärdering av Near Field Communication och Certified Wireless USB: Säkerhet vid utveckling av applikationer2008Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Today’s society is one where technological advances are made daily, which increases the need to stop and assess the risks against users’ integrity when integrating new technology in contemporary systems all the greater. We have taken two technologies, Near Field Communication and Certified Wireless USB, whose envisioned area of use is to be integrated into mobile phones, and evaluated what security threats are revealed for the respective technologies. The threats against security have been identified through research of the standards and existing reports for each technology. Practical experiments have not been conducted on account of us not having access to any equipment to run such trials. The result of our studies is indecisive; pitched against Certified Wireless USB’s rigorous and robust security measures, implemented on hardware level, Near Field Communication’s lack of any such security implementations shines all the brighter. The real difference can be traced to the philosophy behind the technologies – Certified Wireless USB can be perceived as a complete product, while Near Field Communication bears more resemblance to a tool. In order to safely use a tool, knowledge about its use is required, thus in order to securely use Near Field Communication we propose two solutions; secure channel and secure identification, which developers can implement on a software level. Furthermore, we suggest that the implementation of security should be based on an incremental model where the security measures are scaled up in direct correlation with the sensitivity of the information managed. Our results imply that Near Field Communication does not have the inherent security that it should have in order to be safely and securely integrated into any system as it is. Therefore, measures have to be taken in order to implement this technology securely on a software level. For Certified Wireless USB it implies that nothing further is needed to achieve a secure implementation as the only weakness it displays is against Side Channel attacks, which are so complicated (and require direct access to the system) that we have deemed them unlikely to be attempted.

  • 46418. Varni, Giovanna
    et al.
    Dubus, Gaël
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Musikakustik.
    Oksanen, Sami
    Volpe, Gualtiero
    Fabiani, Marco
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Musikakustik.
    Bresin, Roberto
    KTH, Skolan för datavetenskap och kommunikation (CSC), Tal, musik och hörsel, TMH, Musikakustik.
    Kleimola, Jari
    Välimäki, Vesa
    Camurri, Antonio
    Interactive sonification of synchronisation of motoric behaviour in social active listening to music with mobile devices2012Ingår i: Journal on Multimodal User Interfaces, ISSN 1783-7677, E-ISSN 1783-8738, Vol. 5, nr 3-4, s. 157-173Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper evaluates three different interactive sonifications of dyadic coordinated human rhythmic activity. An index of phase synchronisation of gestures was chosen as coordination metric. The sonifications are implemented as three prototype applications exploiting mobile devices: Sync’n’Moog, Sync’n’Move, and Sync’n’Mood. Sync’n’Moog sonifies the phase synchronisation index by acting directly on the audio signal and applying a nonlinear time-varying filtering technique. Sync’n’Move intervenes on the multi-track music content by making the single instruments emerge and hide. Sync’n’Mood manipulates the affective features of the music performance. The three sonifications were also tested against a condition without sonification.

  • 46419.
    Varpstuen, Johan
    Högskolan i Skövde, Institutionen för datavetenskap.
    Heuristisk Utvärdering och Användartestning av ett Verktyg för Web-based Training: Korrespondensen mellan Predicerade och Observerade Användbarhetsproblem2000Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats
    Abstract [sv]

    Ett verktyg för datorstödd interaktiv utbildning, Web-based Training, har utvecklats på Sigma Information Design. Två olika utvärderingsmetoder har använts för att öka dess användbarhet: heuristisk utvärdering och användartestning. Heuristisk utvärdering är en analytisk metod där expertutvärderare inspekterar gränssnittet för att predicera (förutse) användbarhetsproblem. Användartestning är en empirisk metod där tänkbara reella användare deltar och användbarhetsproblem observeras. Föreliggande studie fokuserar på användbarhets-

    problem som både prediceras med den analytiska metoden och observeras med den empiriska, så kallade ”träffar”.

    Analytiska metoder predicerar användbarhetsproblem genom att utpeka bristande ”intrinsic features”

    (gränssnittsegenskaper). Empiriska metoder observerar istället ”payoff features”, för att kunna identifiera användbarhetsproblem och sedan relatera dessa till bristande gränssnitts-egenskaper. Frågeställningen är om analytiska- respektive empiriska metoder utpekar samma bristande ”intrinsic feature” vid identifiering av en ”träff”. Utvärdering av verktyget med respektive utvärderingsmetod har genomförts. Under användartesterna påträffades endast ett fåtal användbarhetsproblem, vilket har medfört att ett litet antal ”träffar” identifierats för att kunna ge svar på frågeställningen. Det finns dock indikationer på en oklar korrespondens mellan metoderna.

  • 46420.
    Varshney, Ambu
    et al.
    Uppsala university, Sweden.
    Soleiman, Andreas
    Uppsala university, Sweden.
    Mottola, Luca
    RISE - Research Institutes of Sweden, ICT, SICS. Politecnico di Milano, Italy.
    Voigt, Thiemo
    RISE - Research Institutes of Sweden, ICT, SICS. Uppsala university, Sweden.
    Battery-free VisibleLight Sensing2017Ingår i: Proceeding VLCS '17 Proceedings of the 4th ACM Workshop on Visible Light Communication Systems. Snowbird, Utah, USA — October 16 - 16, 2017, 2017, s. 3-8Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present the design of the first Visible Light Sensing (VLS) system that consumes only tens of μWs of power to sense and communicate. Unlike most existing VLS systems, we require no modification to the existing light infrastructure since we use unmodulated light as a sensing medium. We achieve this by designing a novel mechanism that uses solar cells to achieve a sub-μW power consumption for sensing. Further, we devise an ultra-low power transmission mechanism that backscatters sensor readings and avoids the processing and computational overhead of existing sensor systems. Our initial results show the ability to detect and transmit hand gestures or presence of people up to distances of 330m at a peak power of μWs. Further, we demonstrate that our system can operate in diverse light conditions (100 lx to 80 klx) where existing VLS designs fail due to saturation of the transimpedance amplifier (TIA).

  • 46421.
    Varshney, Ambuj
    et al.
    Uppsala University, Sweden.
    Harms, Oliver
    Uppsala University, Sweden.
    Perez-Penichet, Carlos
    Uppsala University, Sweden.
    Hermans, Frederik
    Uppsala University, Sweden.
    Rohner, Christian
    Uppsala University, Sweden.
    Voigt, Thiemo
    RISE - Research Institutes of Sweden, ICT, SICS. Uppsala University, Sweden.
    LoRea: A Backscatter Architecture that Achieves a Long Communication Range2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    There is the long-standing assumption that radio communication inthe range of hundreds of meters needs to consume mWs of powerat the transmitting device. In this paper, we demonstrate that this isnot necessarily the case for some devices equipped with backscatterradios. We present LoRea an architecture consisting of a tag, areader and multiple carrier generators that overcomes the power,cost and range limitations of existing systems such as ComputationalRadio Frequency Identication (CRFID). LoRea achieves thisby: First, generating narrow-band backscatter transmissions thatimprove receiver sensitivity. Second, mitigating self-interferencewithout the complex designs employed on RFID readers by keepingcarrier signal and backscattered signal apart in frequency. Finally,decoupling carrier generation from the reader and using devicessuch as WiFi routers and sensor nodes as a source of the carriersignal. An o-the-shelf implementation of LoRea costs 70 USD,a drastic reduction in price considering commercial RFID readerscost 2000 USD. LoRea’s range scales with the carrier strength, andproximity to the carrier source and achieves a maximum range of3:4 km when the tag is located at 1m distance from a 28 dBm carriersource while consuming 70 µW at the tag. When the tag is equidistantfrom the carrier source and the receiver, we can communicateupto 75m, a signicant improvement over existing RFID readers.

  • 46422.
    Varshney, Ambuj
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Harms, Oliver
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Pérez Penichet, Carlos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Hermans, Frederik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    LoRea: A backscatter architecture that achieves a long communication range2017Ingår i: Proc. 15th ACM Conference on Embedded Network Sensor Systems, New York: ACM Press, 2017Konferensbidrag (Refereegranskat)
  • 46423. Varshney, Ambuj
    et al.
    Mottola, Luca
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Carlsson, Mats
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Voigt, Thiemo
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Directional Transmissions and Receptions for High-throughput Bulk Forwarding in Wireless Sensor Networks2015Konferensbidrag (Refereegranskat)
  • 46424. Varshney, Ambuj
    et al.
    Mottola, Luca
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Voigt, Thiemo
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Poster: Coordination of Wireless Sensor Networks using Visible Light2015Konferensbidrag (Refereegranskat)
  • 46425.
    Varshney, Ambuj
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Pérez Penichet, Carlos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Demo: LoRea: A backscatter architecture that achieves a long communication range2017Ingår i: Proc. 15th ACM Conference on Embedded Network Sensor Systems, New York: ACM Press, 2017Konferensbidrag (Refereegranskat)
  • 46426.
    Varshney, Ambuj
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Pérez Penichet, Carlos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Towards wide-area backscatter networks2017Ingår i: Proc. 4th ACM Workshop on Hot Topics in Wireless, New York: ACM Press, 2017, s. 49-53Konferensbidrag (Refereegranskat)
  • 46427.
    Varshney, Ambuj
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Soleiman, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Mottola, Luca
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Battery-free Visible Light Sensing2017Ingår i: Proc. 4th ACM Workshop on Visible Light Communication Systems, New York: ACM Press, 2017, s. 3-8Konferensbidrag (Refereegranskat)
  • 46428.
    Varshney, Ambuj
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Mottola, Luca
    Directional Transmissions and Receptions for Burst Forwarding using Disjoint Paths2014Ingår i: Proc. 13th International Symposium on Information Processing in Sensor Networks, Piscataway, NJ: IEEE Press, 2014, s. 307-308Konferensbidrag (Refereegranskat)
    Abstract [en]

    Bulk data transmission is an important traffic pattern of many sensor network applications. These applications deliver large amounts of sensed data to a sink node for further processing. Most of the existing bulk data transmission protocols use a single flow of communication. This is inefficient as the radio at the source node is transmitting and the sink node is receiving packets for only half of the duration of the burst. We show in this paper that reduced contention because of directional communication enables us to construct node disjoint paths from the source to the sink node using only one wireless channel. This allows us to forward subsequent packets in the burst on the disjoint paths which maximises the radio transmit and receive time at the source and the sink node respectively. We demonstrate that this doubles the sink throughput as compared to a single flow of communication.

  • 46429. Varshney, Ambuj
    et al.
    Voigt, Thiemo
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Mottola, Luca
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Poster Abstract: Directional Transmissions and Receptions for Burst Forwarding using Disjoint Paths2014Konferensbidrag (Refereegranskat)
  • 46430. Varshney, Ambuj
    et al.
    Voigt, Thiemo
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Mottola, Luca
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Poster Abstract: Directional Transmissions and Receptions for High Throughput Burst Forwarding2013Konferensbidrag (Refereegranskat)
  • 46431.
    Varshney, Ambuj
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. SICS Swedish ICT.
    Mottola, Luca
    SICS Swedish ICT.
    Using Directional Transmissions and Receptions to Reduce Contention in Wireless Sensor Networks2014Ingår i: Real-World Wireless Sensor Networks, 2014, s. 205-213Konferensbidrag (Refereegranskat)
    Abstract [en]

    Electronically Switched Directional (ESD) antennas allow software-based control of the direction of maximum antenna gain. ESD antennas are feasible for wireless sensor network. Existing studies with these antennas focus only on controllable directional transmissions. These studies demonstrate reduced contention and increased range of communication with no energy penalty. Unlike existing literature, in this chapter we experimentally explore controllable antenna directionality at both sender and receiver. One key outcome of our experiments is that directional transmissions and receptions together considerably reduce channel contention. As a result, we can significantly reduce intra-path interference.

  • 46432. Varshney, Ambuj
    et al.
    Voigt, Thiemo
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Mottola, Luca
    RISE., Swedish ICT, SICS, Computer Systems Laboratory.
    Using Directional Transmissions and Receptions to Reduce Contention in Wireless Sensor Networks2013Konferensbidrag (Refereegranskat)
  • 46433.
    Varshosaz, Mahsa
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Beohar, Harsh
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Mousavi, Mohammad Reza
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Delta-Oriented FSM-Based Testing2015Ingår i: Formal Methods and Software Engineering: 17th International Conference on Formal Engineering Methods, ICFEM 2015, Paris, France, November 3-5, 2015, Proceedings / [ed] Michael Butler, Sylvain Conchon & Fatiha Zaïdi, Cham: Springer, 2015, Vol. 9407, s. 366-381Konferensbidrag (Refereegranskat)
    Abstract [en]

    We use the concept of delta-oriented programming to organize FSM-based test models in an incremental structure. We then exploit incremental FSM-based testing to make efficient use of this high-level structure in generating test cases. We show how our approach can lead to more efficient test-case generation, both by analyzing the complexity of the test-case generation algorithm and by applying the technique to a case study. © Springer International Publishing Switzerland 2015

  • 46434.
    Vasconcelos Jansson, Erik Sven
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Analysis of Test Coverage Data on a Large-Scale Industrial System2016Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Software testing verifies the program's functional behavior, one important process when engineering critical software. Measuring the degree of testing is done with code coverage, describing the amount of production code affected by tests. Both concepts are extensively used for industrial systems. Previous research has shown that gathering and analyzing test coverages becomes problematic on large-scale systems. Here, development experience, implementation feasibility, coverage measurements and analysis method are explored; providing potential solutions and insights into these issues.

    Outlined are methods for constructing and integrating such gathering and analysis system in a large-scale project, along with the problems encountered and given remedies. Instrumentations for gathering coverage information affect performance negatively, these measurements are provided. Since large-scale test suite measurements are quite lacking, the line, branch, and function criteria are presented here. Finally, an analysis method is proposed, by using coverage set operations and Jaccard indices, to find test similarities.

    Results gathered imply execution time was significantly affected when gathering coverage, [2.656, 2.911] hours for instrumented software, originally between [2.075, 2.260] on the system under test, given under the alpha = 5% and n = 4, while both processor & memory usages were inconclusive. Measured criteria were (59.3, 70.7, 24.6)% for these suites. Analysis method shows potential areas of test redundancy.

  • 46435. Vasconcelos, V. T.
    et al.
    Haller, Philipp
    KTH, Skolan för datavetenskap och kommunikation (CSC), Teoretisk datalogi, TCS.
    Preface2017Ingår i: Electronic Proceedings in Theoretical Computer Science, ISSN 2075-2180, E-ISSN 2075-2180, Vol. 246Artikel i tidskrift (Refereegranskat)
  • 46436.
    Vascós Palacios, Fidel
    Linköpings universitet, Institutionen för datavetenskap, EISLAB - Economic Information Systems. Linköpings universitet, Tekniska högskolan.
    On the information exchange between physicians and social insurance officers in the sick leave process: an activity theoretical perspective2005Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In Sweden, there has been a substantial increase in the number of people on long-term sick leave. This phenomenon has awakened the interest of researchers for understanding its causes. So far, no simple and unambiguous reason explaining this phenomenon has been found. However, previous studies indicate that it may be caused by a combination of different aspects such as the state of the national economy, an ageing labour force in Sweden, and inefficiencies in the information exchange and cooperation among the participants in the sick leave process. This thesis deals with the information exchange between two of these participants, namely physicians from district health care centres and insurance officers from the Social Insurance Office.

    The information exchange between these two parties constitutes a critical aspect in the sick leave process and has been reported in the scientific literature as having problems. Nevertheless, most of earlier studies dealing with the interaction between physicians and officers have been purely descriptive, of quantitative nature and lack a common theoretical basis for analysing it.

    In this thesis, a philosophical theoretical framework, namely Activity Theory (AT), is applied to gain understanding into the interconnection between physicians and insurance officers and the problems of their information exchange. Based on concepts from AT, the elements that form the structure of these players' work actions are identified and used to provide a picture of the interconnection between these parties and to uncover some reasons for the failure in their information exchange. Additionally, an activity theoretical perspective about how to see the participation of these players in the sick leave process is provided.

    The analysis in this thesis shows that physicians and insurance officers form a fragmented division of labour of a common collective activity: the sick leave process. In this process physicians provide the officers with a tool of their work: information for decision-making. Physicians provide this information through the sickness certificate, which sometimes does not carry the information necessary for the officers to do their work. This failure is partly a result of the complexity of the physicians' task to issue sickness certificates. This complexity lies in the characteristics of the elements forming the structure of the physicians' actions of issuing these documents and in contradictions that exist among these elements.

    Additional aspects that affect the information exchange between physicians and officers are that (1) these parties have different perceptions about how to approach their object of work in their joint activity, (2) the lack of resources in district health care centres and local social insurance offices, and (3) the lack of shared artifacts for making the communicative actions between physicians and officers more efficient.

  • 46437.
    Vashi, Priyanki
    Mälardalens högskola, Akademin för innovation, design och teknik.
    Migration of a Mobile Core Application to a Simplified Infrastructure - In-Service Performance Analysis2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Ericsson has always strived for the technology leadership in its offering by designing products based on the latest technology. Going ahead with a similar thought it started exploring an idea of running a mobile core application using a Simplified Infrastructure (SI) to eventually enable the Cloud based solutions. But in order to run these type of applications in the Cloud, the in-service performance provided by such a SI should be the same as the native infrastructure in order to maintain the mobile core application’s QoS. "High availability" of the infrastructure is one of the measure of the ISP and from the ISP point of view, such a migration would be considered feasible only if the SI is able to maintain the same level of availability as provided by the native infrastructure solution without bringing in any major architecture changes within the SI. Hence this master thesis project investigates the feasibility of achieving the same availability as before if the mobile core application is to be migrated from the native infrastructure to the SI. Such a feasibility exploration was the very first attempt with respect to the SI within Ericsson, which was executed through this master thesis project. In order to achieve the goal of this thesis project a detailed system study was carried out, which focused on the native infrastructure architecture, how it was maintaining the "high availability" and how it differed from the SI.

    In the end, it was possible to confirm that the level of availability of infrastructure services as provided through the SI will be higher than the native infrastructure after the migration if the proposed suggestions of this master thesis project are implemented successfully. These implementations also do not change the architecture of the SI in any major way. The end results of this thesis project were also highly appreciated by Ericsson and are now part of thedevelopment plan for next mobile core infrastructure solution at Ericsson.

  • 46438. Vasic, Nedeljko
    et al.
    Barisits, Martin
    Salzgeber, Vincent
    Kostic, Dejan
    EPFL.
    Making Cluster Applications Energy-Aware2009Ingår i: Proceedings of The First Workshop on Automated Control for Datacenters and Clouds (ACDC), Association for Computing Machinery (ACM), 2009, s. -42Konferensbidrag (Refereegranskat)
    Abstract [en]

    Power consumption has become a critical issue in large scale clusters. Existing solutions for addressing the servers’ energy consumption suggest “shrinking” the set of active machines, at least until the more power-proport-ional hardware devices become available. This paper demonstrates that leveraging the sleeping state, however, may lead to unacceptably poor performance and low data availability if the distributed services are not aware of the power management’s actions. Therefore, we present an architecture for cluster services in which the deployed services overcome this problem by actively participating in any action taken by the power management. We propose, implement, and evaluate modifications for the Hadoop Distributed File System and the MapReduce clone that make them capable of operating efficiently under limited power budgets.

  • 46439. Vasic, Nedeljko
    et al.
    Kostic, Dejan
    EPFL.
    Energy-Aware Traffic Engineering2010Ingår i: Proceedings of the 1st Int’l Conf. on Energy-Efficient Computing and Networking (E-ENERGY), Association for Computing Machinery (ACM), 2010, s. -178Konferensbidrag (Refereegranskat)
    Abstract [en]

    Energy consumption of the Internet is already substantial and it is likely to increase as operators deploy faster equipment to handle popular bandwidth-intensive services, such as streaming and video-on-demand. Existing work on energy saving considers local adaptation relying primarily on hardware-based techniques, such as sleeping and rate adaptation. We argue that a complete solution requires a network-wide approach that works in conjunction with local measures. However, traditional traffic engineering objectives do not include energy. This paper presents Energy-Aware Traffic engineering (EATe), a technique that takes energy consumption into account while optimizing for low link utilization and high end-host sending rates. EATe uses a scalable, online technique to spread the load among multiple paths so as to increase energy savings. Our extensive ns-2 simulations over realistic topologies show that EATe succeeds in moving 21% of the links to the sleep state, while keeping the same sending rates and being close to the optimal energy-aware solution. Further, we demonstrate that EATe successfully handles changes in traffic load and quickly restores a low overall energy state. Alternatively, EATe can move links to lower energy levels, resulting in energy savings of 8%. Finally, EATe can succeed in making 16% of active routers sleep.

  • 46440. Vasic, Nedeljko
    et al.
    Kuntimaddi, Srinidhi
    Kostic, Dejan
    EPFL.
    One Bit Is Enough: a Framework for Deploying Explicit Feedback Congestion Control Protocols2009Ingår i: Proceedings of The First International Conference on COMmunication Systems and NETworkS (COMSNETS), IEEE conference proceedings, 2009, s. -9Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since the bandwidth-delay products of Internet links keep increasing, issues with TCP’s convergence time, throughput, and amount of queuing in these environments are becoming more pressing. As we move toward the next-generation Internet, it is important to start experimenting with congestion control protocols for high BDP networks as soon as possible. Load-factor based congestion control approach holds great promise as it requires moderate changes in routers (only to monitor and insert current load into packets) and endpoints (to use a congestion controller that uses router feedback). However, existing proposals either require substantial changes in the IP header (XCP and most recently, MLCP) that make deployment difficult, or have slow convergence time and fairness issues (VCP). In this paper we describe UNO, a framework for fine-grain explicit feedback congestion control protocols that uses only 1 or 2 existing ECN bits, thus making algorithms that use more than 2 bits for encoding the load factor and the RTT immediately deployable. UNO accomplishes this task by changing the way load and RTT information is encoded in packets. UNO takes advantage of the IP identification field and trades-off small amount of time (to send several packets) for space to emulate the existence of several extra bits within the IP header. The results from extensive ns2 simulations over various bandwidth and delay scenarios are encouraging. By using only one ECN bit we achieve substantially lower convergence times and better link utilization than the existing deployable protocols, with similar low queue size and negligible packet loss. With 2 ECN bits, we achieve very good fairness for flows with different RTTs, while keeping all the good characteristics of the 1-bit protocol.

  • 46441. Vasic, Nedeljko
    et al.
    Novakovic, Dejan
    Miucin, Svetozar
    Kostic, Dejan
    EPFL.
    Bianchini, Ricardo
    DejaVu: Accelerating Resource Allocation in Virtualized Environments2012Ingår i: Proceedings of the Seventeenth International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS), Association for Computing Machinery (ACM), 2012, s. -436Konferensbidrag (Refereegranskat)
    Abstract [en]

    Effective resource management of virtualized environments is a challenging task. State-of-the-art management systems either rely on analytical models or evaluate resource allocations by running actual experiments. However, both approaches incur a significant overhead once the workload changes. The former needs to recalibrate and re-validate models, whereas the latter has to run a new set of experiments to select a new resource allocation. During the adaptation period, the system may run with an inefficient configuration.

  • 46442. Vasic, Nedeljko
    et al.
    Novakovic, Dejan
    Shekhar, Satyam
    Bhurat, Prateek
    Canini, Marco
    Kostic, Dejan
    EPFL.
    Identifying and Using Energy-Critical Paths2011Ingår i: Proceedings of The 7th International Conference on emerging Networking EXperiments and Technologies (ACM CoNEXT), Association for Computing Machinery (ACM), 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The power consumption of the Internet and datacenter networks is already significant, and threatens to shortly hit the power delivery limits while the hardware is trying to sustain ever-increasing traffic requirements. Existing energy-reduction approaches in this domain advocate recomputing network configuration with each substantial change in demand. Unfortunately, computing the minimum network subset is computationally hard and does not scale. Thus, the network is forced to operate with diminished performance during the recomputation periods. In this paper, we propose REsPoNse, a framework which overcomes the optimality-scalability trade-off. The insight in REsPoNse is to identify a few energy-critical paths off-line, install them into network elements, and use a simple online element to redirect the traffic in a way that enables large parts of the network to enter a low-power state. We evaluate REsPoNse with real network data and demonstrate that it achieves the same energy savings as the existing approaches, with marginal impact on network scalability and application performance.

  • 46443.
    Vasilakos, Athanasios
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Duan, Qiang
    Pennsylvania State University.
    Federated selection of network and cloud services for high-performance software-defined cloud computing2016Ingår i: International Journal of High Performance Computing and Networking, ISSN 1740-0562, E-ISSN 1740-0570, Vol. 9, nr 4, s. 316-327Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The crucial role of networking in cloud service provisioning calls for federated selection of network and cloud services in order to guarantee the service performance required by diverse applications. In order to address the new challenges brought in by the software-defined cloud environment (SDCE) to service selection, we develop an approach for performance-based federated selection of network and cloud services in this paper. The main contributions we make in this paper include an abstract profile for network/cloud service capability that is agnostic to service implementations, a general demand profile applicable to diverse applications, an analysis technique for evaluating achievable performance of composite network-cloud services, and a scheme for federated selection of network and cloud services based on performance evaluation. The technique and method developed in this paper enable service selection with a holistic vision across the networking and computing domains, which may greatly facilitate high-performance cloud service provisioning

  • 46444.
    Vasilakos, Athanasios
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Li, Zhe
    Institut Mine Telecom - Telecom Bretagne, France.
    Simon, Gwendal
    Institut Mine Telecom - Telecom Bretagne, France.
    You, Wei
    Orange, France.
    Information centric network: Research challenges and opportunities2015Ingår i: Journal of Network and Computer Applications, ISSN 1084-8045, E-ISSN 1095-8592, Vol. 52, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    For more than a decade, the inherent drawbacks of current Internet have been calling for its revolutionary designs. The end-to-end model, which was designed for special data transmission in the early age of Internet, is causing troubles everywhere in nowadays content based web services. Consequently, Information Centric Network (ICN) is proposed to solve these problems. As the most permanent clean-slate approach for next generation Internet, ICN has attracted much attention from network researchers in the passed few years. This survey focuses on the current progress of the research work in ICN. It investigates various key aspects such as naming and routing schemes, in-network caching policies, etc., and highlights the benefit of implementing ICN, open research issues and new interests in this domain.

  • 46445. Vasile, C. -I
    et al.
    Tumova, Jana
    KTH, Skolan för datavetenskap och kommunikation (CSC), Robotik, perception och lärande, RPL.
    Karaman, S.
    Belta, C.
    Rus, D.
    Minimum-violation scLTL motion planning for mobility-on-demand2017Ingår i: 2017 IEEE International Conference on Robotics and Automation (ICRA), Institute of Electrical and Electronics Engineers (IEEE), 2017, s. 1481-1488, artikel-id 7989177Konferensbidrag (Refereegranskat)
    Abstract [en]

    This work focuses on integrated routing and motion planning for an autonomous vehicle in a road network. We consider a problem in which customer demands need to be met within desired deadlines, and the rules of the road need to be satisfied. The vehicle might not, however, be able to satisfy these two goals at the same time. We propose a systematic way to compromise between delaying the satisfaction of the given demand and violating the road rules. We utilize scLTL formulas to specify desired behavior and develop a receding horizon approach including a periodically interacting routing algorithm and a RRT<-based motion planner. The proposed solution yields a provably minimum-violation trajectory. An illustrative case study is included.

  • 46446.
    Vasilevskaya, Maria
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Designing Security-enhanced Embedded Systems: Bridging Two Islands of Expertise2013Licentiatavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The increasing prevalence of embedded devices and a boost in sophisticated attacks against them make embedded system security an intricate and pressing issue. New approaches to support the development of security-enhanced systems need to be explored. We realise that efficient transfer of knowledge from security experts to embedded system engineers is vitally important, but hardly achievable in current practice.This thesis proposes a Security-Enhanced Embedded system Design (SEED) approach, which is a set of concepts, methods, and tools that together aim at addressing this challenge of bridging the gap between the two areas of expertise.

    First, we introduce the concept of a Domain-Specific Security Model (DSSM) as a suitable abstraction to capture the knowledge of security experts in a way that this knowledge can be later reused by embedded system engineers. Each DSSM characterises common security issues of a specific application domain in a form of security properties, which are further linked to a range of solutions.

    As a next step, we complement a DSSM with the concept of a Performance Evaluation Record (PER) to account for the resource-constrained nature of embedded systems. Each PER characterises the resource overhead created by a security solution, a provided level of security, and the evaluation technique applied.

    Finally, we define a process that assists an embedded system engineer in selecting a relevant set of security solutions. The process couples together (i) the use of the security knowledge accumulated in DSSMs and PERs, (ii) the identification of security issues in a system design, and (iii) the analysis of resource constraints of a system and available security solutions. The approach is supported by a set of tools that automate its certain steps.

    We use a case study from a smart metering domain to demonstrate how the SEED approach can be applied. We show that our approach adequately supports security experts in description of knowledge about security solutions in the form of formalised ontologies and embedded system engineers in integration of an appropriate set of security solutions based on that knowledge.

  • 46447.
    Vasilevskaya, Maria
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska fakulteten.
    Security in Embedded Systems: A Model-Based Approach with Risk Metrics2015Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    The increasing prevalence of embedded devices and a boost in sophisticated attacks against them make embedded system security an intricate and pressing issue. New approaches to support the development of security-enhanced systems need to be explored. We realise that efficient transfer of knowledge from security experts to embedded system engineers is vitally important, but hardly achievable in current practice. This thesis proposes a Security-Enhanced Embedded system Design (SEED) approach, which is a set of concepts, methods, and processes that together aim at addressing this challenge of bridging the gap between the two areas of expertise. 

    We introduce the concept of a Domain-Specific Security Model (DSSM) as a suitable abstraction to capture the knowledge of security experts in a way that this knowledge can be later reused by embedded system engineers. Each DSSM characterises common security issues of a specific application domain in a form of security properties linked to a range of solutions. Next, we complement a DSSM with the concept of a Performance Evaluation Record (PER) to account for the resource-constrained nature of embedded systems. Each PER characterises the resource overhead created by a security solution, a provided level of security, and other relevant information. 

    We define a process that assists an embedded system engineer in selecting a suitable set of security solutions. The process couples together (i) the use of the security knowledge accumulated in DSSMs and PERs, (ii) the identification of security issues in a system design, (iii) the analysis of resource constraints of a system and available security solutions, and (iv) model-based quantification of security risks to data assets associated with a design model. The approach is supported by a set of tools that automate certain steps.

    We use scenarios from a smart metering domain to demonstrate how the SEED approach can be applied. We show that our artefacts are rich enough to support security experts in description of knowledge about security solutions, and to support embedded system engineers in integration of an appropriate set of security solutions based on that knowledge. We demonstrate the effectiveness of the proposed method for quantification of security risks by applying it to a metering device. This shows its usage for visualising of and reasoning about security risks inherent in a system design.

  • 46448.
    Vasilevskaya, Maria
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Ariani Gunawan, Linda
    Norwegian University of Science and Technology, NTNU.
    Nadjm-Tehrani, Simin
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för datavetenskap, Programvara och system.
    Herrmann, Peter
    Norwegian University of Science and Technology, NTNU.
    Integrating security mechanisms into embedded systems by domain-specific modelling2014Ingår i: Security and Communication Networks, ISSN 1939-0114, E-ISSN 1939-0122, Vol. 7, nr 12, s. 2815-2832Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Embedded devices are crucial enablers of the Internet of Things and become increasingly common in our daily life. They store, manipulate and transmit sensitive information and, therefore, must be protected against security threats. Due to the security and also resource constraint concerns, designing secure networked embedded systems is a difficult task. Model-based development (MBD) is promoted to address complexity and ease the design of software intensive systems. We leverage MBD and domain-specific modelling to characterise common issues related to security and embedded systems that are specific to a given application domain. Security-specific knowledge relevant for a certain application domain is represented in the form of an adapted information security ontology. Further, the elements of the ontology are associated with security building blocks modelled with the MBD method SPACE. The selection of relevant security building blocks is based on (i) assets automatically elicited from the functional models, (ii) domain security knowledge captured by the security expert and (iii) the platform adopted by the embedded system engineer. A tool is developed to support the steps supporting this methodology and help to bridge between the security and embedded systems domains. We illustrate our approach with a case study from the smart metering domain.

  • 46449.
    Vasilevskaya, Maria
    et al.
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Broman, David
    KTH Royal Institute of Technology, Stockholm, Sweden; University of California, Berkeley, USA.
    Sandahl, Kristian
    Linköpings universitet, Institutionen för datavetenskap, Programvara och system. Linköpings universitet, Tekniska fakulteten.
    Assessing Large Project Courses: Model, Activities, and Lessons Learned2015Ingår i: ACM Transactions on Computing Education, ISSN 1946-6226, E-ISSN 1946-6226, Vol. 15, nr 4, s. 20:1-20:30Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In a modern computing curriculum, large project courses are essential to give students hands-on experience of working in a realistic software engineering project. Assessing such projects is, however, extremely challenging. There are various aspects and tradeoffs of assessments that can affect the course quality. Individual assessments can give fair grading of individuals, but may loose focus of the project as a group activity. Extensive teacher involvement is necessary for objective assessment, but may affect the way students are working. Continuous feedback to students can enhance learning, but may be hard to combine with fair assessment. Most previous work is focusing on some specific assessment aspect, whereas we in this paper present an assessment model that consists of a collection of assessment activities, each covering different aspects. We have applied, developed, and improved these activities during a seven-year period. To evaluate the usefulness of the model, we perform questionnaire-based surveys over a two-years period. Furthermore, we design and execute an experiment that studies to what extent students can perform fair peer assessment and to what degree the assessments of students and teachers agree. We analyze the results, discuss findings, and summarize lessons learned.

  • 46450.
    Vasilevskaya, Maria
    et al.
    Linköping University.
    Broman, David
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Programvaruteknik och Datorsystem, SCS.
    Sandahl, Kristian
    Linköping University.
    Assessing Large Project Courses: Model, Activities, and Lessons LearnedIngår i: ACM Transactions on Computing Education, ISSN 1946-6226, E-ISSN 1946-6226Artikel i tidskrift (Refereegranskat)
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