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  • 251.
    Bäckström, David
    Linköpings universitet, Institutionen för datavetenskap.
    Boundary-Scan in the ATCA standard2005Independent thesis Basic level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Larger systems today, like telephone and optical switches, are usually based on a multiboard architecture where a set of printed-circuit boards are connected to a backplane board. These systems are also equipped with Boundary-Scan to enable testing, however, the backplane in a multi-board system has a limited wiring capability, which makes the additional backplane Boundary-Scan wiring highly costly. The problem is to access the Boundary-Scan enabled boards with the Boundary-Scan controller located at a central board. In this MSc. thesis project we propose an approach suitable for the Advanced Telecommunication Computing Architecture (ATCA) standard where we make use of the existing Intelligent Platform Management Bus (IPMB) and expands its protocol for application of Boundary-Scan tests. We have also defined a command set as well as a test data format for storing embedded test data on the boards to support the remote execution of Boundary-Scan tests. For validation of the proposed approach we have developed demonstrator.

  • 252.
    Bäckström, David
    Växjö universitet, Fakulteten för matematik/naturvetenskap/teknik, Matematiska och systemtekniska institutionen.
    Pulstågsmodul2006Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
  • 253.
    Bäckström, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Limitations of Azure in GIS Scalability: A performance and migration study2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this study, the cloud platform Windows Azure has been targeted for test implementations of Geographical Information System (GIS) software in the form of map servers and tile caches. The map servers included were GeoServer, MapNik, MapServer and SharpMap, which together with the tile caches, GeoWebCache, MapCache and TileCache, were installed on Windows Azures three different virtual machine roles (Web, Worker and VM). Furthermore, different techniques for scalingapplications and internal role communication are presented, followed by four sets of performance tests. The performance tests attempt to highlight the differences in request times, how the different role sizes handle the load from the incoming requests, how the different role sizes handle many concurrent TCP-connections and how well the incoming requests are load balanced in between the worker roles. The test implementations showed that all map servers and tile caches were successfully installed in Azure, which leads to the conclusion that Windows Azure is suitable for hosting GIS software with similar installation requirements to the previously mentioned software. Four different approaches (Direct mapping, Public Internal Endpoints, Queue and Worker Role Request Broker) are presented showing how Azure allows different methods in order to scale the internal role communication as well as the external client requests. The performance tests provided somewhat inconclusive test results due to hardware limitations in the test setup. This made it difficult to draw concluding parallels between the final results and the expected values. Minor tendencies in performance gain can be seen when scaling the VM size as well as the number of VMs.

  • 254.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Inbyggda system (CERES).
    Handover in IEEE 802.11p-based delay-sensitive vehicle-to-infrastructure communication2009Rapport (Annet vitenskapelig)
    Abstract [en]

    Based on communication and cooperation between vehicles and roadside infrastructure, Intelligent Transport Systems (ITS) safety applications offer great potential to avoid traffic accidents or at least reduce their impact. As these applications usually are delay-sensitive, the delay introduced by waiting for access to the wireless communication channel should both be reduced and provided with an upper bound. The proposed IEEE 802.11p standard for short to medium range vehicular communication does not offer these guarantees. In previous work, we presented a MAC (Medium Access Control) enhancement supporting delay-sensitive, safety-critical V2I (Vehicle-to-Infrastructure) applications. Since the proposed enhancement requires a deterministic and fast mechanism to associate a vehicle to a roadside unit (RSU) so that it can be integrated into the centralized polling schedule, we now target the handover and connection setup between a vehicle and an RSU. Although the first connection setup with an RSU still underlies the randomness of the original 802.11p MAC method, we provide a deterministic solution to further enhance the handover procedures by introducing a fast, proactive handover mechanism. We show that the overhead of our solution is limited and still allows our MAC protocol to support safety-critical V2I applications in a densely trafficked highway scenario.

  • 255.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Jonsson, Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Position-based data traffic prioritization in safety-critical, real-time vehicle-to-infrastructure communication2009Inngår i: IEEE International Conference on Communications Workshops, 2009. ICC Workshops 2009 / [ed] IEEE, Piscataway, N.J.: IEEE Press, 2009, s. 205-210Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Future active-safety applications in vehicular networks rely heavily on the support for real-time inter-vehicle communication. The Medium Access Control (MAC) mechanism proposed for the upcoming IEEE 802.11p standard intended for Intelligent Transport Systems (ITS) applications does not offer deterministic real-time support, i.e., the channel access delay is not upper bounded. We therefore propose a vehicle-to-infrastructure (V2I) communication solution extending IEEE 802.11p, by introducing a collision-free MAC phase with an enhanced prioritization mechanism based on vehicle positions and the overall road traffic density. A road side unit using a polling mechanism is then able to provide real-time support such that it can guarantee collision-free channel access within its transmission range. Part of the bandwidth remains unchanged such that best-effort services like ongoing vehicle-to-vehicle (V2V) applications may continue. Our solution guarantees that all communication deadlines of the V2I applications are met, while minimizing the required length of the collision-free phase. This in turn maximizes the amount of bandwidth available for best-effort services and ongoing V2V applications. The position-based prioritization mechanism further improves the throughput of both real-time and best-effort data traffic by focusing the communication resources to the most hazardous areas. The concept is evaluated analytically based on a realistic task set from a V2I merge assistance scenario.

  • 256.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Jonsson, Magnus
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Kunert, Kristina
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    A fibre-optic AWG-based real-time network for high-performance embedded computing2004Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, an architecture and a Medium Access Control (MAC) protocol for a multiwavelength optical communication network, applicable in short range communication systems like System Area Networks (SANs), are proposed. The main focus lies on guaranteed support for hard and soft real-time traffic. The network is based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) at its center. Traffic scheduling is centralized in one node (residing together with the AWG in a hub), which communicates through a physical control channel. The AWG’s property of spatial wavelength reuse and the combination of fixedtuned and tunable transceivers in the nodes enable simultaneous control and data transmission. A case study with defined real-time communication requirements in the field of Radar Signal Processing (RSP) was carried out and indicates that the proposed system is very suitable for this kind of application.

  • 257.
    Böhm, Annette
    et al.
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Kunert, Kristina
    Högskolan i Halmstad, Akademin för informationsteknologi, Halmstad Embedded and Intelligent Systems Research (EIS), Centrum för forskning om inbyggda system (CERES).
    Data age based MAC scheme for fast and reliable communication within and between platoons of vehicles2016Inngår i: International Conference on Wireless and Mobile Computing, Networking and Communications, Piscataway: IEEE, 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Heavy vehicles driving as platoon with highly reduced inter-vehicle gaps has shown considerable fuel saving potential, but put high timing and reliability requirements on the underlying control data exchange. The recently standardized IEEE 802.11p protocol suite for Vehicular Ad-Hoc Networks (VANETs) and its message types do neither support the demands of a platooning application nor take advantage of its properties. We therefore propose a framework for centralized channel access with retransmission capabilities for safety critical control data exchange based on the data age of earlier received messages, DA-RE (Data Age based REtransmission scheme). A simulation comparison to the 802.11p random access Medium Access Control (MAC) protocol shows that the intelligent assignment of retransmission opportunities considerably improves the reliability of platooning control data. We also propose a power control based scheme for early platoon detection allowing several platoons to temporarily share a channel and show that the safe and reliable operation of their vehicles is not compromised. © 2016 IEEE.

  • 258. Calandriello, Giorgio
    et al.
    Papadimitratos, Panos
    Hubaux, Jean-Pierre
    Lioy, Antonio
    Efficient and Robust Pseudonymous Authentication in VANET2007Inngår i: VANET'07: PROCEEDINGS OF THE FOURTH ACM INTERNATIONAL WORKSHOP ON VEHICULAR AD HOC NETWORKS, 2007, s. 19-27Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Effective and robust operations, as well as security and privacy are critical for the deployment of vehicular ad hoc networks (VANETs). Efficient and easy-to-manage security and privacy-enhancing mechanisms axe essential for the wide-spread adoption of the VANET technology. In this paper, we are concerned with this problem; and in particular, how to achieve efficient and robust pseudonym-based authentication. We design mechanisms that reduce the security overhead for safety beaconing, and retain robustness for transportation safety, even in adverse network settings. Moreover, we show how to enhance the availability and usability of privacy-enhancing VANET mechanisms: Our proposal enables vehicle on-board units to generate their own pseudonyms, without affecting the system security.

  • 259.
    Carbone, Marco
    et al.
    IT Univ Copenhagen, Rued Langgaards Vej 7, DK-2300 Copenhagen, Denmark..
    Hildebrandt, Thomas
    IT Univ Copenhagen, Rued Langgaards Vej 7, DK-2300 Copenhagen, Denmark..
    Parrow, Joachim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Weidlich, Matthias
    Humboldt Univ, Unter Linden 6, D-10099 Berlin, Germany..
    Extended versions of papers presented at WS-FM 2014 and Beat 20142016Inngår i: Formal Aspects of Computing, ISSN 0934-5043, E-ISSN 1433-299X, Vol. 28, nr 4, s. 529-530Artikkel i tidsskrift (Annet vitenskapelig)
  • 260.
    Carlson, Trevor E.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Heirman, Wim
    Intel, ExaSci Lab, Santa Clara, CA USA..
    Allam, Osman
    Univ Ghent, B-9000 Ghent, Belgium..
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Eeckhout, Lieven
    Univ Ghent, B-9000 Ghent, Belgium..
    The Load Slice Core Microarchitecture2015Inngår i: 2015 ACM/IEEE 42Nd Annual International Symposium On Computer Architecture (ISCA), 2015, s. 272-284Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Driven by the motivation to expose instruction-level parallelism (ILP), microprocessor cores have evolved from simple, in-order pipelines into complex, superscalar out-of-order designs. By extracting ILP, these processors also enable parallel cache and memory operations as a useful side-effect. Today, however, the growing off-chip memory wall and complex cache hierarchies of many-core processors make cache and memory accesses ever more costly. This increases the importance of extracting memory hierarchy parallelism (MHP), while reducing the net impact of more general, yet complex and power-hungry ILP-extraction techniques. In addition, for multi-core processors operating in power- and energy-constrained environments, energy-efficiency has largely replaced single-thread performance as the primary concern. Based on this observation, we propose a core microarchitecture that is aimed squarely at generating parallel accesses to the memory hierarchy while maximizing energy efficiency. The Load Slice Core extends the efficient in-order, stall-on-use core with a second in-order pipeline that enables memory accesses and address-generating instructions to bypass stalled instructions in the main pipeline. Backward program slices containing address-generating instructions leading up to loads and stores are extracted automatically by the hardware, using a novel iterative algorithm that requires no software support or recompilation. On average, the Load Slice Core improves performance over a baseline in-order processor by 53% with overheads of only 15% in area and 22% in power, leading to an increase in energy efficiency (MIPS/Watt) over in-order and out-of-order designs by 43% and over 4.7x, respectively. In addition, for a power- and area-constrained many-core design, the Load Slice Core outperforms both in-order and out-of-order designs, achieving a 53% and 95% higher performance, respectively, thus providing an alternative direction for future many-core processors.

  • 261.
    Carlsson, Arthur
    Linköpings universitet, Institutionen för datavetenskap.
    Integration av AJAX i JDP: En studie i hur WM-data kan utveckla modelleringsstödet i ett webbramverk2008Independent thesis Advanced level (degree of Magister), 20 poäng / 30 hpOppgave
    Abstract [sv]

    På WM-data har man utvecklat ett ramverk som heter Java Development Platform med avsikt att modellera större delar av ett system och därmed minska mängden kod som måste skrivas för hand. Ramverket baseras helt på existerande öppna lösningar och används vid utveckling av webbaserade system och skapar en skiktat lösning med en webbapplikation som presentationslager. Problemet är att webbapplikationen har kommit att bli väldigt svår att modellera i enhet med resten av systemet framför allt på grund av den hårda kopplingen till Struts-ramverket. Samtidigt har man börjat få upp ögonen för AJAX och vad det skulle kunna tillföra ramverket.

    Examensarbetet fokuserar på att utreda de problem som existerar i ramverket samt undersöka integrationen av AJAX ur en synvinkel som gynnar dagens lösning. Detta görs genom litteraturstudier, laborationer och genom att undersöka existerande ramverk och plattformar som löser liknande problem. Fokus ligger även på hur AJAX kan användas för att lösa problemen i modelleringen.

    Resultatet av arbetet mynnar ut i en analys som behandlar de aspekter som krävs för att AJAX ska kunna bli en del av JDP-ramverket. Analysen innefattar också synen på hur AJAX skulle kunna användas för att underlätta modelleringen av webbapplikationen utan att införa något nytt modelleringsverktyg, det vill säga att UML fortfarande kan användas.

  • 262.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    BGP oscillations when peering with loopback addresses2006Inngår i: 20th International Conference on Advanced Information Networking and Applications, Vol 2, Proceedings / [ed] Martin DC, LOS ALAMITOS, USA: IEEE COMPUTER SOC , 2006, s. 712-716Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An oscillating routing protocol will result in increased protocol activity and may lead to increased router CPU activity and memory consumption.  This case study shows that BGP peering using loopback addresses when peering EBGP between two dualhomed ASes will cause BGP to oscillate. It includes a detailed lab report in which several possible setups that will cause BGP to oscillate are presented. It also includes an oscillation event from one of the world's largest production networks that was caused by such a setup.

  • 263.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Improving BGP convergence properties and web content blocking using BGP2006Licentiatavhandling, med artikler (Annet vitenskapelig)
  • 264.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Perceived problems with BGP: a survey2006Rapport (Annet vitenskapelig)
  • 265.
    Carlzon, Malin
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Resetting a damped out route in BGP2006Rapport (Annet vitenskapelig)
  • 266.
    Carlzon, Malin
    et al.
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Hagsand, Olof
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Widell, Fredrik
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Danielsson, Björn
    KTH, Skolan för datavetenskap och kommunikation (CSC), Numerisk Analys och Datalogi, NADA.
    Blocking web contents using BGP: measurements and observations2006Rapport (Annet vitenskapelig)
  • 267. Casoni, E.
    et al.
    Jerusalem, A.
    Samaniego, C.
    Eguzkitza, B.
    Lafortune, P.
    Tjahjanto, Denny
    KTH, Skolan för teknikvetenskap (SCI), Hållfasthetslära (Inst.). IMDEA Materials Institute, Spain .
    Saez, X.
    Houzeaux, G.
    Vazquez, M.
    Alya: Computational Solid Mechanics for Supercomputers2015Inngår i: Archives of Computational Methods in Engineering, ISSN 1134-3060, E-ISSN 1886-1784, Vol. 22, nr 4, s. 557-576Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    While solid mechanics codes are now conventional tools both in industry and research, the increasingly more exigent requirements of both sectors are fuelling the need for more computational power and more advanced algorithms. For obvious reasons, commercial codes are lagging behind academic codes often dedicated either to the implementation of one new technique, or the upscaling of current conventional codes to tackle massively large scale computational problems. Only in a few cases, both approaches have been followed simultaneously. In this article, a solid mechanics simulation strategy for parallel supercomputers based on a hybrid approach is presented. Hybrid parallelization exploits the thread-level parallelism of multicore architectures, combining MPI tasks with OpenMP threads. This paper describes the proposed strategy, programmed in Alya, a parallel multi-physics code. Hybrid parallelization is specially well suited for the current trend of supercomputers, namely large clusters of multicores. The strategy is assessed through transient non-linear solid mechanics problems, both for explicit and implicit schemes, running on thousands of cores. In order to demonstrate the flexibility of the proposed strategy under advance algorithmic evolution of computational mechanics, a non-local parallel overset meshes method (Chimera-like) is implemented and the conservation of the scalability is demonstrated.

  • 268.
    Castberg, Miro
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Adaptor Development: An insight to interfacing with electrical energy meters2011Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Since energy meters became more advanced and able to send data remotely, energy suppliers have had a need to keep their data managed. This gave birth to energy management systems which gather data from energy meters. However, for every type of meter there needs to be a specialization in the management system.

    Smart Metering Language (SML) is a protocol which was created to transfer meter data in as simple way as possible. Implementing the protocol would result in simpler and less vendor-specific solutions for energy management systems.

    This report follows the process of developing an adaptor between a device using the SML protocol and a system that manages energy meters. The thesis uses different parts of the development process in able to show specializations which were needed by the test device and its vendor. 

    The result sums up the experience of developing an adaptor and the specializations which are needed in the SML protocol.

  • 269.
    Ceballos, Germán
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Grass, Thomas
    Barcelona Supercomputing Center, Spain.
    Hugo, Andra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Analyzing performance variation of task schedulers with TaskInsight2018Inngår i: Parallel Computing, ISSN 0167-8191, E-ISSN 1872-7336, Vol. 75, s. 11-27Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Recent scheduling heuristics for task-based applications have managed to improve performance by taking into account memory-related properties such as data locality and cache sharing. However, there is still a general lack of tools that can provide insights into why, and where, different schedulers result in different memory behavior, and how this is related to the applications’ performance.

    To address this we present TaskInsight, a technique to characterize the memory behavior of different task schedulers through the analysis of data reuse across tasks. TaskInsight provides high-level, quantitative information that can be correlated with tasks’ performance variation over time to understand data reuse through the caches due to scheduling choices. TaskInsight is useful to diagnose and identify which scheduling decisions affected performance, when were they taken, and why the performance changed, both in single and multi-threaded executions.

    We demonstrate how TaskInsight can diagnose cases where poor scheduling caused over 40% difference on average (and up to 7x slowdowns) across the Montblanc benchmarks due to changes in the tasks’ data reuse through the private and shared caches. This flexible insight is key for optimization in many contexts, including data locality, throughput, memory footprint or even energy efficiency.

  • 270.
    Ceballos, Germán
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Grass, Thomas
    Hugo, Andra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    TaskInsight: Understanding task schedules effects on memory and performance2017Inngår i: Proc. 8th International Workshop on Programming Models and Applications for Multicores and Manycores, New York: ACM Press, 2017, s. 11-20Konferansepaper (Fagfellevurdert)
  • 271.
    Ceballos, Germán
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Sembrant, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Carlson, Trevor E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Analyzing Graphics Workloads on Tile-based GPUs2017Inngår i: Proc. 20th International Symposium on Workload Characterization, IEEE, 2017, s. 108-109Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Graphics rendering is a complex, multi-step process whose data demands typically dominate memory system design in SoCs. GPUs create images by merging many, simpler scenes for each frame. For performance, scenes are tiled into parallel tasks, each of which produces different parts of the final output. This execution model results in complex memory behavior, whose bandwidth demands, reuse and sharing characteristics depend heavily on the structure and complexity of each application, frame, scene, and task, and vary over time. To design systems that can efficiently accommodate and schedule these workloads, we need to understand their behavior and diversity. In this work, we explore the data demands of modern graphics rendering quantitatively, using an architecturally-independent analysis that identifies the different types of data sharing present in the applications.

  • 272. Cebrian, Juan M.
    et al.
    Sanchez, Daniel
    Aragon, Juan L.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Efficient inter-core power and thermal balancing for multicore processors2013Inngår i: Computing, ISSN 0010-485X, E-ISSN 1436-5057, Vol. 95, nr 7, s. 537-566Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nowadays the market is dominated by processor architectures that employ multiple cores per chip. These architectures have different behavior depending on the applications running on the processor (parallel, multiprogrammed, sequential), but all happen to meet what is called the power and temperature wall. For future technologies (less than 22 nm) and a fixed die size, it is still uncertain the percentage of processor that can be simultaneously powered on. Power saving and power budget mechanisms can be useful to precisely control the amount of power been dissipated by the processor. After an initial analysis we discover that legacy power saving techniques work properly for matching a power budget in thread-independent and multi-programmed workloads, but not in parallel workloads. When running parallel shared-memory applications sacrificing some performance in a single core (thread) in order to be more energy-efficient can unintentionally delay the rest of cores (threads) due to synchronization points (locks/barriers), having a negative impact on global performance. In order to solve this problem we propose power token balancing (PTB) aimed at accurately matching an external power constraint by balancing the power consumed among the different cores. Experimental results show that PTB matches more accurately a predefined power budget (50 % of the original peak power) than other mechanisms like DVFS. The total energy consumed over the budget is reduced to only 8 % for a 16-core CMP with only a 3 % energy increase (overhead). We also introduce a novel mechanism named "Nitro". Nitro will overclock the core that enters a critical section (delimited by locks) in order to free the lock as soon as possible. Experimental results have shown that Nitro is able to reduce the execution time of lock-intensive applications in more than 4 % by overclocking the frequency by 15 % in selected program phases over a period of time that represents a 22 % of the total execution time. We conclude the work with an analysis of the thermal effects of PTB in different CMP configurations using realistic power numbers and heatsink/fan configurations. Results show how PTB not only balances temperature between the different cores, reducing temperature gradient and increasing signal reliability, but also allows a reduction of 28-30 % of both average and peak temperatures for the studied benchmarks when a peak power budget of 50 % is exceeded.

  • 273. Cebrian, Juan M.
    et al.
    Sanchez, Daniel
    Aragon, Juan L.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Managing power constraints in a single-core scenario through power tokens2014Inngår i: Journal of Supercomputing, ISSN 0920-8542, E-ISSN 1573-0484, Vol. 68, nr 1, s. 414-442Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Current microprocessors face constant thermal and power-related problems during their everyday use, usually solved by applying a power budget to the processor/core. Dynamic voltage and frequency scaling (DVFS) has been an effective technique that allowed microprocessors to match a predefined power budget. However, the continuous increase of leakage power due to technology scaling along with low resolution of DVFS makes it less attractive as a technique to match a predefined power budget as technology goes to deep-submicron. In this paper, we propose the use of microarchitectural techniques to accurately match a power constraint while maximizing the energy-efficiency of the processor. We will predict the processor power dissipation at cycle level (power token throttling) or at a basic block level (basic block level mechanism), using the dissipated power translated into tokens to select between different power-saving microarchitectural techniques. We also introduce a two-level approach in which DVFS acts as a coarse-grain technique to lower the average power dissipation towards the power budget, while microarchitectural techniques focus on removing the numerous power spikes. Experimental results show that the use of power-saving microarchitectural techniques in conjunction with DVFS is up to six times more precise, in terms of total energy consumed over the power budget, than only using DVFS to match a predefined power budget.

  • 274. Cebrián, Juan M.
    et al.
    Aragón, Juan L.
    García, José M.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Leakage-efficient design of value predictors through state and non-state preserving techniques2011Inngår i: Journal of Supercomputing, ISSN 0920-8542, E-ISSN 1573-0484, Vol. 55, nr 1, s. 28-50Artikkel i tidsskrift (Fagfellevurdert)
  • 275. Cebrián, Juan M.
    et al.
    Aragón, Juan L.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Power Token Balancing: Adapting CMPs to power constraints for parallel multithreaded workloads2011Inngår i: Proc. 25th International Parallel and Distributed Processing Symposium, Piscataway, NJ: IEEE , 2011, s. 431-442Konferansepaper (Fagfellevurdert)
  • 276. Cebrián, Juan M.
    et al.
    Fernández-Pascual, Ricardo
    Jimborean, Alexandra
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Acacio, Manuel E.
    Ros, Alberto
    A dedicated private-shared cache design for scalable multiprocessors2017Inngår i: Concurrency and Computation, ISSN 1532-0626, E-ISSN 1532-0634, Vol. 29, nr 2, artikkel-id e3871Artikkel i tidsskrift (Fagfellevurdert)
  • 277.
    Cenanovic, Mirza
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Finite element methods for surface problems2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this thesis is to further develop numerical methods for solving surface problems by utilizing tangential calculus and the trace finite element method. Direct computation on the surface is possible by the use of tangential calculus, in contrast to the classical approach of mapping 2D parametric surfaces to 3D surfaces by means of differential geometry operators. Using tangential calculus, the problem formulation is only dependent on the position and normal vectors of the 3D surface. Tangential calculus thus enables a clean, simple and inexpensive formulation and implementation of finite element methods for surface problems. Meshing techniques are greatly simplified from the end-user perspective by utilizing an unfitted finite element method called the Trace Finite Element Method, in which the basic idea is to embed the surface in a higher dimensional mesh and use the shape functions of this background mesh for the discretization of the partial differential equation. This method makes it possible to model surfaces implicitly and solve surface problems without the need for expensive meshing/re-meshing techniques especially for moving surfaces or surfaces embedded in 3D solids, so called embedded interface problems. Using these two approaches, numerical methods for solving three surface problems are proposed: 1) minimal surface problems, in which the form that minimizes the mean curvature was computed by iterative update of a level-set function discretized using TraceFEM and driven by advection, for which the velocity field was given by the mean curvature flow, 2) elastic membrane problems discretized using linear and higher order TraceFEM, which makes it straightforward to embed complex geometries of membrane models into an elastic bulk for reinforcement and 3) stabilized, accurate vertex normal and mean curvature estimation with local refinement on triangulated surfaces. In this thesis the basics of the two main approaches are presented, some aspects such as stabilization and surface reconstruction are further developed, evaluated and numerically analyzed, details on implementations are provided and the current state of work is presented.

  • 278.
    Cenanovic, Mirza
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Finite element methods on surfaces2015Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The purpose of this thesis is to improve numerical simulations of surface problems. Two novel computational concepts are analyzed and applied on two surface problems; minimal surface problems and elastic membrane problems. The concept of tangential projection implies that direct computation on the surface is made possible compared to the classical approach of mapping 2D parametric surfaces to 3D surfaces by means of differential geometry operators. The second concept presented is the cut finite element method, in which the basic idea of discretization is to embed the d- 1-dimensional surface in a d-dimensional mesh and use the basis functions of a higher dimensional mesh but integrate over the surface. The aim of this thesis is to present the basics of the two main approaches and to provide details on the implementation.

  • 279.
    Cenanovic, Mirza
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Numerical error estimation for a TraceFEM membrane and distance function on P1 and P2 tetrahedraManuskript (preprint) (Annet vitenskapelig)
  • 280.
    Cenanovic, Mirza
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Hansbo, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Larsson, Mats G.
    Umeå University.
    Cut finite element modeling of linear membranes2016Inngår i: Computer Methods in Applied Mechanics and Engineering, ISSN 0045-7825, E-ISSN 1879-2138, Vol. 310, s. 98-111Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We construct a cut finite element method for the membrane elasticity problem on an embedded mesh using tangential differential calculus, i.e., with the equilibrium equations pointwise projected onto the tangent plane of the surface to create a pointwise planar problem in the tangential direction. Both free membranes and membranes coupled to 3D elasticity are considered. The discretization of the membrane comes from a Galerkin method using the restriction of 3D basis functions (linear or trilinear) to the surface representing the membrane. In the case of coupling to 3D elasticity, we view the membrane as giving additional stiffness contributions to the standard stiffness matrix resulting from the discretization of the three-dimensional continuum.

  • 281.
    Cenanovic, Mirza
    et al.
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Hansbo, Peter
    Högskolan i Jönköping, Tekniska Högskolan, JTH, Produktutveckling. Högskolan i Jönköping, Tekniska Högskolan, JTH. Forskningsmiljö Produktutveckling - Simulering och optimering.
    Larsson, Mats G.
    Finite element procedures for computing normals and mean curvature on triangulated surfaces and their use for mesh refinementManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    In this paper we consider finite element approaches to computing the mean curvature vector and normal at the vertices of piecewise linear triangulated surfaces. In particular, we adopt a stabilization technique which allows for first order L2-convergence of the mean curvature vector and apply this stabilization technique also to the computation of continuous, recovered, normals using L2-projections of the piecewise constant face normals. Finally, we use our projected normals to define an adaptive mesh refinement approach to geometry resolution where we also employ spline techniques to reconstruct the surface before refinement. We compare or results to previously proposed approaches.

  • 282.
    Chabloz, Jean-Michel
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Hemani, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektroniksystem.
    Lowering the Latency of Interfaces for Rationally-Related Frequencies2010Inngår i: 2010 IEEE INTERNATIONAL CONFERENCE ON COMPUTER DESIGN, 2010, s. 23-30Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We have introduced the Globally-Ratiochronous, Locally-Synchronous (GRLS) design paradigm, a design style based on rationally-related frequencies, with the objective to overcome the limitations of traditional multi-frequency systems by providing a flexibility close that of Globally-Asynchronous, Locally-Synchronous (GALS) systems but introducing performance penalties and overheads close to those of mesochronous systems. In this paper we focus on performances and improve the latency figures of our original GRLS interfaces by introducing two new interfaces, called GRLS-F and GRLS-noF, the first suitable for blocks with long computation time and the second for blocks with short computation time. The latency figures of the original GRLS interfaces are improved up to 50% without increasing complexity. The average latency figures of the resulting interfaces are lower than 1 Receiver clock cycle, the latency of a synchronous interface.

  • 283.
    Chavez Alcarraz, Erick
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Data- och elektroteknik.
    Moraga, Manuel
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Data- och elektroteknik.
    Linked data performance in different databases: Comparison between SQL and NoSQL databases2014Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [en]

    Meepo AB was investigating the possibility of developing a social rating and recommendation service. In a recommendation service, the user ratings are collected in a database, this data is then used in recommendation algorithms to create individual user recommendations.

    The purpose of this study was to find out which  demands are put on a DBMS, database management system, powering a recommendation service, what impact the NoSQL databases have on the performance of recommendation services compared to traditional relational databases, and which DBMS is most suited for storing the data needed to host a recommendation service.

    Five distinct NoSQL and Relational DBMS were examined, from these three candidates were chosen for a closer comparison.

    Following a study of recommendation algorithms and services, a test suite was created to compare DBMS performance in different areas using a data set of 100 million ratings.

    The results show that MongoDB had the best performance in most use cases, while Neo4j and MySQL struggled with queries spanning the whole data set.

    This paper however never compared performance for real production code. To get a better comparison, more research is needed. We recommend new performance tests for MongoDB and Neo4j using implementations of recommendation algorithms, a larger data set, and more powerful hardware.

  • 284.
    Cheema, Ansar Zaman
    et al.
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Saqib, Imran Ullah
    Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE).
    Collaborating ISPs Supporting Various Real-Time Services2010Independent thesis Advanced level (degree of Master (One Year)), 15 poäng / 22,5 hpOppgave
    Abstract [en]

    These days, internet service providers (ISPs) face the challenge about how to increase profitability while hey must ensure a good quality service at the same time and scale up their network. The study involves previous research papers. On the bases of those papers,the comparison is made between different alternatives. The purpose on this study is to find a solution that combines different methods and configurations about how several ISPs could cooperate. Its implementation includes how different ISPs can configure their networks to cooperate on service provision supporting various real-time services.

  • 285.
    Chehrazi, Golriz
    Linköpings universitet, Institutionen för systemteknik.
    Workflow management systems, their security and access control mechanisms2007Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This paper gives an overview of workflow management systems (WfMSs) and their security requirements with focus on access mechanisms. It is a descriptive paper in which we examine the state of the art of workflow systems, describe what security risks affect WfMSs in particular, and how these can be diminiuished.

    WfMSs manage, illustrate and support business processes. They contribute to the performance, automation and optimization of processes, which is important in the global economy today. The security of process flows is important, since the sensitive business data need to be protected to inhibit illegal activities, such as blackmailing, imitation and fraud and to provide for good customer service.

    This paper focuses on access mechanisms, because they are basic security mechanisms used by WfMSs assuring that only authorized users are provided access to data and resources. Also because of the unsecurity of the Internet, which is commonly used as infrastructure of Workflow systems, additional security mechanisms, such as PKIs, digital signatures and SSL have to be used to provide secure workflows.

    Depending on the particular requirements in workflow systems, different extensional access control (AC) mechanisms have been developed to maintain security. But when it comes to commercially used WfMSs, the availability of the system is of utmost importance. It is the prerequisite for the system to be employed by companies. The problem is that there is always a trade-off between availability of the system and security. Because this trade off is generally solved in favor of availability, a major part of the developed AC mechanisms are not used in commercially used WfMS.

    After the first part of this paper which is rather theoretical, we examine a commercial WfMS, namely IBM's MQ Workflow , and its security mechanisms. We show vulnerabilities of the system that could be abused by attackers. Afterwards, we show which security mechanisms, in particular, AC mechanisms are provided to secure against threats. We conclude with a summary, which highlights the difference between security concepts developed in the research area and those really implemented by the commercially used WfMS.

  • 286.
    Chen, Kairang
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    Energy-Efficient Data Converters for Low-Power Sensors2016Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Wireless sensor networks (WSNs) are employed in many applications, such as for monitoring bio-potential signals and environmental information. These applications require high-resolution (> 12-bit) analog-to-digital converters (ADCs) at low-sampling rates (several kS/s). Such sensor nodes are usually powered by batteries or energy-harvesting sources hence low power consumption is primary for such ADCs. Normally, tens or hundreds of autonomously powered sensor nodes are utilized to capture and transmit data to the central processor. Hence it is profitable to fabricate the relevant electronics, such as the ADCs, in a low-cost standard complementary metal-oxide-semiconductor (CMOS) process. The two-stage pipelined successive approximation register (SAR) ADC has shown to be an energy-efficient architecture for high resolution. This thesis further studies and explores the design limitations of the pipelined SAR ADC for high-resolution and low-speed applications.

    The first work is a 15-bit, 1 kS/s two-stage pipelined SAR ADC that has been implemented in 0.35-μm CMOS process. The use of aggressive gain reduction in the residue amplifier combined with a suitable capacitive array digital-to-analog converter (DAC) topology in the second-stage simplifies the design of the operational transconductance amplifier (OTA) while eliminating excessive capacitive load and consequent power consumption. A comprehensive power consumption analysis of the entire ADC is performed to determine the number of bits in each stage of the pipeline. Choice of a segmented capacitive array DAC and attenuation capacitorbased DAC for the first and second stages respectively enable significant reduction in power consumption and area. Fabricated in a low-cost 0.35-μm CMOS process, the prototype ADC achieves a peak signal-to-noise-and-distortion ratio (SNDR) of 78.9 dB corresponding to an effective number of bits (ENOB) of 12.8-bit at a sampling frequency of 1 kS/s and provides a Schreier figure-of-merit (FoM) of 157.6 dB. Without any form of calibration, the ADC maintains an ENOB > 12.1-bit up to the Nyquist bandwidth of 500 Hz while consuming 6.7 μW. Core area of the ADC is 0.679 mm2.

    The second work is a 14-bit, tunable bandwidth two-stage pipelined SAR ADC which is suitable for low-power, cost-effective sensor readout circuits. To overcome the high open-loop DC gain requirement of the OTA in the gain-stage, a 3-stage capacitive charge pump (CCP) is utilized to achieve the gain-stage instead of using the switch capacitor (SC) amplifier. Unity-gain OTAs have been used as the analog buffers to prevent the charge sharing between the CCP stages. The detailed design considerations are given in this work. The prototype ADC, designed and fabricated in a low-cost 0.35-μm CMOS process, achieves a peak SNDR of 75.6 dB at a sampling rate of 20 kS/s and 76.1 dB at 200 kS/s while consuming 7.68 μW and 96 μW, respectively. The corresponding Schreier FoM are 166.7 dB and 166.3 dB. Since the bandwidth of CCP is tunable, the ADC maintains a SNDR > 75 dB up

    to 260 kHz. The core area occupied by the ADC is 0.589 mm2.

    As the low-power sensors might be active only for very short time triggered by an external pulse to acquire the data, the third work is a 14-bit asynchronous two-stage pipelined SAR ADC which has been designed and simulated in 0.18-μm CMOS process. A self-synchronous loop based on an edge detector is utilized to generate an internal clock with variable phase. A tunable delay element enables to allocate the available time for the switch capacitor DACs and the gain-stage. Three separate asynchronous clock generators are implemented to create the control signals for two sub-ADCs and the gain-stage between. Aiming to reduce the power consumption of the gain-stage, simple source followers as the analog buffers are implemented in the 3-stage CCP gain-stage. Post-layout simulation results show that the ADC achieves a SNDR of 83.5 dB while consuming 2.39 μW with a sampling rate of 10 kS/s. The corresponding Schreier FoM is 176.7 dB.

  • 287.
    Chen, Kairang
    et al.
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    Alvandpour, Atila
    Linköpings universitet, Institutionen för systemteknik, Elektroniska Kretsar och System. Linköpings universitet, Tekniska fakulteten.
    A pipelined SAR ADC with gain-stage based on capacitive charge pump2017Inngår i: Analog Integrated Circuits and Signal Processing, ISSN 0925-1030, E-ISSN 1573-1979, Vol. 90, nr 1, s. 43-53Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper presents a 14-bit, tunable bandwidth two-stage pipelined successive approximation analog to digital converter which is suitable for low-power, cost-effective sensor readout circuits. To overcome the high DC gain requirement of operational transconductance amplifier in the gain-stage, the multi-stage capacitive charge pump (CCP) was utilized to achieve the gain-stage instead of using the switch capacitor integrator. The detailed design considerations are given in this work. Thereafter, the 14-bit ADC was designed and fabricated in a low-cost 0.35-µm CMOS process. The prototype ADC achieves a peak SNDR of 75.6 dB at a sampling rate of 20 kS/s and 76.1 dB at 200 kS/s while consuming 7.68 and 96 µW, respectively. The corresponding FoM are 166.7 and 166.3 dB. Since the bandwidth of CCP is tunable, the ADC maintains a SNDR >75 dB upto 260 kHz. The core area occupied by the ADC is 0.589 mm2.

  • 288.
    Chen, Nan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    An IEEE 802.15.4 Packet Error Classification Algorithm: Discriminating Between Multipath Fading and Attenuation and WLAN2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In wireless sensor networks, communications are usually destroyed by signal attenuation, multipath fading and different kinds of interferences like WLAN and microwave oven interference. In order to build a stable wireless communication system, reactions like retransmission mechanisms are necessary. Since the way we must react to interference is different from the way we react to multipathfading and attenuation, the retransmission mechanism should be adjusted in different ways under those different cicumstances. Under this condition, channel diagnostics for discriminating the causes that corrupt the packets between multipath fading and attenuation (MFA) and WLAN interference are imperative. This paper presents a frame bit error rate (F-BER) regulated algorithm based on a joint RSSI-LQI classifier that may correctly diagnose the channel status. This discriminator is implemented on MicaZ sensor devices equipped with CC2420 transceivers. This discriminator is able to improve the accuracy to 91%. Although we need to wait for 2 or 3 necessary packets to make a decision, higher stability and reliability are presented when operating this discriminator.

  • 289.
    Chen, Wei
    Linköpings universitet, Institutionen för systemteknik.
    RTL implementation of Viterbi Decoder2006Student paper first term, 20 poäng / 30 hpOppgave
    Abstract [en]

    A forward error correction technique known as convolutional coding with Viterbi decoding was explored in this final thesis. This Viterbi project is part of the baseband Error control project at electrical engineering department, Linköping University.

    In this project, the basic Viterbi decoder behavior model was built and simulated. The convolutional encoder, puncturing, 3 bit soft decision, BPSK and AWGN channel were implemented in MATLAB code. The BER was tested to evaluate the decoding performance.

    The main issue of this thesis is to implement the RTL level model of Viterbi decoder. With the testing results of behavior model, with minimizing the data path, register size and butterflies in the design, we try to achieve a low silicon cost design. The RTL Viterbi decoder model includes the Branch Metric block, the Add-Compare-Select block, the trace-back block, the decoding block and next state block. With all done, we further understand about the Viterbi decoding algorithm and the DSP implementation methods.

  • 290.
    Chen, Xiaowen
    et al.
    KTH, Skolan för elektro- och systemteknik (EES).
    Lu, Zhonghai
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, VinnExcellence Center for Intelligence in Paper and Packaging, iPACK. KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik.
    Liu, S.
    Chen, S.
    Round-trip DRAM access fairness in 3D NoC-based many-core systems2017Inngår i: ACM Transactions on Embedded Computing Systems, ISSN 1539-9087, E-ISSN 1558-3465, Vol. 16, nr 5s, artikkel-id 162Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In 3D NoC-based many-core systems, DRAM accesses behave differently due to their different communication distances and the latency gap of different DRAM accesses becomes bigger as the network size increases, which leads to unfair DRAM access performance among different nodes. This phenomenon may lead to high latencies for some DRAM accesses that become the performance bottleneck of the system. The paper addresses the DRAM access fairness problem in 3D NoC-based many-core systems by narrowing the latency difference of DRAM accesses as well as reducing the maximum latency. Firstly, the latency of a round-trip DRAM access is modeled and the factors causing DRAM access latency difference are discussed in detail. Secondly, the DRAM access fairness is further quantitatively analyzed through experiments. Thirdly, we propose to predict the network latency of round-trip DRAM accesses and use the predicted round-trip DRAM access time as the basis to prioritize the DRAM accesses in DRAM interfaces so that the DRAM accesses with potential high latencies can be transferred as early and fast as possible, thus achieving fair DRAM access. Experiments with synthetic and application workloads validate that our approach can achieve fair DRAM access and outperform the traditional First-Come-First-Serve (FCFS) scheduling policy and the scheduling policies proposed by reference [7] and [24] in terms of maximum latency, Latency Standard Deviation (LSD)1 and speedup. In the experiments, the maximum improvement of the maximum latency, LSD, and speedup are 12.8%, 6.57%, and 8.3% respectively. Besides, our proposal brings very small extra hardware overhead (<0.6%) in comparison to the three counterparts.

  • 291.
    Chen, Zongzhe
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Privacy Preserving Implementation in the E-health System2013Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    E-health systems are widely used in today’s world, and have a stillbrighter future with the rapid development of smart phones. A fewyears ago, e-health system could only be carried out on computers.But recently, people are using this as a phone application, so thatthey can get information at any time and anywhere. In addition,some smart phones can already measure heart rate and bloodpressure, for example, ‚Instant Heart Rate‛ and ‚Blood PressureMonitor‛. By using these kinds of applications, users can easilymeasure their health data and store them in their mobile phones.However, the problem of privacy has been attracting people’sattention. After uploading their data to the database, users do havethe right to protect their privacy. For instance, even the doctor hasthe authority to obtain the health record; the user's name can behidden, so that the doctor does not know who the owner of this datais. This problem also includes anonymization, pseudonymity,unlinkability, unobservability and many other aspects.In this thesis work, an android application is proposed to solve thisproblem. Users can set their own rules, and all data requests shouldbe dealt with by calling the rules. In addition, a module in the serveris to be developed to carry out the whole process of privacypreserving and the users’ data should be stored in the database.A standard for users to set rules is determined, which is bothdynamical and flexible. The application realizes some additional rulechecking functions to determine whether users have set a valid rule.Privacy rules can be created, deleted, or uploaded. In addition, userscan update their health record and upload it to the database. Theserver will call different protocols to deal with different requests, andthe data which obtains the requests is responded to by calling theusers’ own privacy rules.

  • 292.
    Cheng, Hei Victor
    Linköpings universitet, Institutionen för systemteknik, Kommunikationssystem. Linköpings universitet, Tekniska fakulteten.
    Aspects of Power Allocation in Massive MIMO2016Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The past decades have seen a rapid growth of mobile data trac, both in terms of connected devices and data rate. To satisfy the ever growing data trac demand in wireless communication systems, the current cellular systems have to be redesigned to increase both spectral eciency and energy eciency. Massive MIMO (Multiple-Input-Multiple-Output) is one solution that satisfy both requirements. In massive MIMO systems, hundreds of antennas are employed at the base station to provide service to many users at the same time and frequency. This enables the system to serve the users with uniformly good quality of service simultaneously, with low-cost hardware and without using extra bandwidth and energy. To achieve this, proper resource allocation is needed. Among the available resources, transmit power is one of the most important degree of freedom to control the spectral eciency and energy eciency. Due to the use of excessive number of antennas and low-end hardware at the base station, new aspects of power allocation compared to current systems arises. In the rst part of the thesis, a new uplink power allocation schemes that based on long term channel statistics is proposed. Since quality of the channel estimates is crucial in massive MIMO, in addition to data power allocation, joint power allocation that includes the pilot power as additional variable should be considered. Therefore a new framework for power allocation that matches practical systems is developed, as the methods developed in the literature cannot be applied directly to massive MIMO systems. Simulation results conrm the advantages brought by the the proposed new framework. In the second part of the thesis, we investigate the eects of using low-end ampliers at the base stations. The non-linear behavior of power consumption in these ampliers changes the power consumption model at the base station, thereby changes the power allocation. Two dierent scenarios are investigated and both results show that a certain number of antennas can be turned o in low load scenarios.

  • 293.
    Chivi, Daniel
    et al.
    KTH, Skolan för kemi, bioteknologi och hälsa (CBH).
    Östling Gran, Joakim
    KTH, Skolan för elektroteknik och datavetenskap (EECS).
    Administration av API-drivna enheter och tjänster för slutanvändare: En fallstudie av API-tjänster2018Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    I dagsläget tenderar många att använda tjänster som hanteras separat. Arbetet undersöker om det är möjligt att sammankoppla ett fåtal tjänster i en gemensam webbapplikation för att underlätta kommunicering mellan tjänsterna samt att förbättra användarvänligheten.

    Företaget A Great Thing har i åtanke att skapa en webbapplikation som tillåter användare att med hjälp av deras applikation skapa agenter som sköter händelser från användarens begäran, exempelvis “spela upp en låt vid en viss tid”.

    Metodiken som tillämpats har dels varit en fallstudie och dels användarbaserade metoder i form av enkätundersökning samt ett användartest. Ytterligare undersöktes hur kommunikationen går mellan tjänsters API, och de nödvändiga parametrar som utbyter data. Slutligen evalueras den framtagna prototypen enligt vissa riktlinjer inom användarvänlighet.

    Examensarbetets resultat är i form av en webbprototyp med fokus på användarvänlighet, implementering av API:er, användartest på faktiska användare samt statistik på efterfrågan av tjänster. Vidare har även en marknadsundersökning utförts för att belysa ekonomiska vinstmöjligheter genom API-distribution.

    Slutsatsen dras att det är möjligt att sammankoppla API:er och dess tjänster för att uppnå ett användarvänligt gränssnitt samt hur nödvändiga parametrar disponeras på ett effektivt vis. Vidare är förhoppningen att utomstående läsare skapar en förståelse om hur sammankopplingen går till på ett strukturerat och informativt tillvägagångssätt. Även hur olika tekniska metoder inom användarvänlighet kan tillämpas vid konstruktion av prototyper. 

  • 294.
    Christensen, Jens
    et al.
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Ekstedt, Jonatan
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Evaluation of Plugin Frameworks for the Jenkins Continuous Integration Build Server2012Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Begreppet Continuous Integration (CI) är idag centralt för många företag i deras produktutveckling. Kraven dessa företag ställer på denna programvara skiljer sig, beroende på vad de använder den till och hur deras miljö ser ut. Jenkins är en programvara som används för CI, det är öppen källkod och har ett brett stöd för pluginer. Det finns ett stort urval av pluginer redan idag, men det är inte säkert att specifika önskemål från företag uppfylls av dessa. Därför är det intressant att på ett snabbt sätt ta fram specifika pluginer för dessa företag.

    Vi har i denna rapport utrett möjligheterna att utveckla pluginer till Jenkins i Ruby. Det senaste året har utveckling av pluginer i Ruby vuxit fram för Jenkins. Ramverket är fortfarande i ett tidigt stadium, men är utformat för att kunna falla tillbaka på det programmeringsspråk som Jenkins är skrivet i; Java. Det är på så sätt fullt möjligt att nu skriva pluginer i Ruby. Ruby är ett expressivt språk som är lätt att ta till sig, och den komplexitet som följer pluginutveckling i Java är till stor del gömd i Rubys ramverk.

    Vår slutsats är att Ruby är tillräckligt moget för att användas till pluginutveckling för Jenkins.

    Examensarbetet är uppdelat i två delar: en utvärdering av ramverken och deras verktyg för Ruby och Java, och en utvecklingsfas där vi fastställer vår analys. Den Rubyplugin som utvecklats kan ses som ett ‘proof-of-concept’, denna kan även användas som en slags mall vid framtida pluginutveckling vid Autoliv.

  • 295.
    Christoffersson, Jessica
    Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Evaluation of Systematic&Colour Print Mottle2005Independent thesis Basic level (professional degree)Oppgave
    Abstract [en]

    Print mottle is a problem that has been hassling the printing business for a long time. Along with sharpness and correct colour reproduction, absence of print mottle is one of the most important factors of print quality. The possibility to measure the amount of print mottle (reflectance variation) may in many ways facilitate the development of printing methods. Such a measurement model should preferably follow the functions and abilities of the Human Visual System (HVS).

    The traditional model that STFI-Packforsk has developed to measure print mottle uses frequency analysis to find variations in reflectance. However, this model suffers some limitations since is does not perfectly agree with the functions of the HVS and does only measure variations in lightness. A new model that better follows the functions of the HVS has thus been developed. The new model does not only consider variations in lightness (monochromatic) but also variations in colour (chromatic). The new model also puts a higher weight on systematic variations than on random variations since the human eye is more sensitive to ordered structures. Furthermore, the new model uses a contrast sensitivity function that weights the importance of variations in different frequencies.

    To compare the new model with the traditional STFI model, two tests were carried out. Each test consisted of a group of test patches that were evaluated by the traditional STFI model and the new model. The first test consisted of 15 greyscale test patches that originated from conventional flexo and offset presses. The second test consisted of 24 digitally simulated test patches containing colour mottle and systematic mottle.

    The evaluation results in both the traditional and the new model were compared to the results of a visual evaluation carried out using a panel of test persons. The new model produced a result that correlated considerably better with the visual estimation than what the traditional model did.

  • 296.
    Chukala, Sileshi
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    A Move Towards Practicability: Context Information and User Profile Management for the SensibleThings Platform2016Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Achievements in academia and industry indicate a move towards the creation of a giant smart system including objects of different sizes, shapes, and purposes where the Internet will be so diverse and more resourceful with the incorporation of different smart devices. Mid Swe-den University took a first step towards providing an appropriate plat-form for Internet of Things applications known as SensibleThings for the emerging intercommunication of “objects”, called Internet of Things. The SensibleThings platform has produced components for sharing sensor-based context information on the Internet, in order to enable Internet of Things applications. In this thesis the plan was to contribute to filling the gap between the IoT and developers in academia as well as in the industries. The aim of the project was to create basic functionality to enable users to find new interesting users on the IoT and prioritize existing users. To this end context information and user profile man-agement is proposed and presented. Furthermore, a comparison be-tween the platform with the proposed extension as well as without was compared and examined.

  • 297.
    Ciobanu, Alexandru
    et al.
    McGill University, Canada .
    Hemati, Saied
    Linköpings universitet, Institutionen för systemteknik, Elektroniksystem. Linköpings universitet, Tekniska högskolan.
    Gross, Warren J.
    McGill University, Canada .
    Adaptive Multiset Stochastic Decoding of Non-Binary LDPC Codes2013Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 61, nr 16, s. 4100-4113Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We propose a non-binary stochastic decoding algorithm for low-density parity-check (LDPC) codes over GF(q) with degree two variable nodes, called Adaptive Multiset Stochastic Algorithm (AMSA). The algorithm uses multisets, an extension of sets that allows multiple occurrences of an element, to represent probability mass functions that simplifies the structure of the variable nodes. The run-time complexity of one decoding cycle using AMSA is O(q) for conventional memory architectures, and O(1) if a custom memory architecture is used. Two fully-parallel AMSA decoders are implemented on FPGA for two (192,96) (2,4)-regular codes over GF(64) and GF(256), both achieving a maximum clock frequency of 108 MHz. The GF(64) decoder has a coded throughput of 65 Mb/s at E-b/N-0 = 2.4 dB when using conventional memory, while a decoder using the custom memory version can achieve 698 Mb/s at the same E-b/N-0. At a frame error rate (FER) of 2 x 10(-6) the GF(64) version of the algorithm is only 0.04 dB away from the floating-point SPA performance, and for the GF(256) code the difference is 0.2 dB. To the best of our knowledge, this is the first fully parallel non-binary LDPC decoder over GF(256) reported in the literature.

  • 298.
    Ciobanu Morogan, Matei
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Data- och systemvetenskap, DSV.
    Security system for ad-hoc wireless networks based on generic secure objects2005Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    As computing devices and wireless connectivity become ubiquitous, new usage scenarios emerge, where wireless communication links between mobile devices are established in an ad-hoc manner. The resulting wireless ad-hoc networks differ from classical computer networks in a number of ways, lack of permanent access to the global network and heterogeneous structure being some of them. Therefore, security services and mechanisms that have been designed for classical computer networks are not always the optimal solution in an ad-hoc network environment.

    The research is focused on analyzing how standard security services that are available in classical networks can be provided in an ad-hoc wireless network environment. The goal is to design a security system optimized for operation in ad-hoc wireless networks that provides the same security services – authentication, access control, data confidentiality and integrity, non-repudiation – currently available in classic wired networks.

    The first part of the thesis is the design and implementation of a security platform based on generic secure objects. The flexible and modular nature of this platform makes it suitable for deployment on devices that form ad-hoc networks – ranging from Java-enabled phones to PDAs and laptops.

    We then investigate the problems that appear when implementing in ad-hoc networks some of the security technologies that are standard building blocks of secure systems in classical computer networks. Two such technologies have been found to present problems, namely the areas of certification and access control. In a series of articles, we have described the problems that appear and devised solutions to them by designing protocols, techniques and extensions to standards that are optimized for usage in the ad-hoc network environment.

    These techniques, together with the functionality provided by the underlying security platform, are used to implement all standard security services – confidentiality, authentication, access control, non repudiation and integrity, allowing to integrate ad-hoc networks into the existing security infrastructure.

  • 299.
    Claug, Erik
    Linköpings universitet, Institutionen för datavetenskap. Linköpings universitet, Tekniska högskolan.
    Web Design for Multiple Platforms in Microsoft SharePoint 20132013Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    As mobile devices become more common when surfing the web there is an increasing demand of making web sites adjusted to other devices than computers. One common platform on the web is Microsoft SharePoint. In this report I look into one method of how to develop web sites that work on multiple devices in Microsoft SharePoint. I will be looking into different techniques as separate web sites compared to responsive web design. By exploring the approach of mobile first I try to find a working solution of techniques. I also look into another method that is suggested in a book and look into how Bootstrap could be used in the process.

    I will also look into content to identify what content need to be adjusted between different devices. I find that navigation is an important part of a web site and look into different methods of handling navigation on mobile devices.

    By analyzing different techniques and looking into what content is going to be adjusted a solution is proposed where the navigation is adjusted in a responsive design. The design is converted into a SharePoint masterpage and then fixed using stylesheets and JavaScript. The solution works on a web site with a complex site structure since it focuses on how to adjust the navigation.

  • 300.
    Clear, Tony
    et al.
    Auckland Univ Technol, Sch Engn Comp & Math Sci, Auckland, New Zealand..
    Beecham, Sarah
    Univ Limerick, Lero, Limerick, Ireland..
    Barr, John
    Ithaca Coll, Ithaca, NY 14850 USA..
    Daniels, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Oudshoorn, Michael
    Wentworth Inst Technol, Dept Comp Sci & Comp Networking, Boston, MA USA..
    Noll, John
    Univ Limerick, Lero, Limerick, Ireland..
    Developments in Global Software Engineering Education2016Inngår i: 2016 IEEE FRONTIERS IN EDUCATION CONFERENCE (FIE), 2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    An ITiCSE 2015 conference working group report has recently delivered a comprehensive systematic review of the literature addressing the challenges and solutions in teaching global software engineering courses. In this panel session, a group of authors of that report will review the findings, and present their own views on teaching such courses, the pros and cons and their own motivations and experiences, together with strategies that have proven effective. We argue that these courses are critical for preparing students for practice as software engineers in today's global settings, but they are certainly not for the faint-hearted. After the review and presentation of position statements by panelists there will be a question and answer session with the audience and a discussion elaborating on the next frontiers in research and practice for global software engineering education.

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