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  • 1.
    Abbas, Syed Muhammad
    et al.
    Jönköping University, School of Engineering, JTH, Computer and Electrical Engineering. Jönköping University, School of Engineering. Jönköping University.
    Henricsson, Christopher
    Jönköping University, School of Engineering, JTH, Computer and Electrical Engineering. Jönköping University, School of Engineering. Jönköping University.
    A Simulation Framework for Efficient Search in P2P Networks with 8-Point HyperCircles2008Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report concerns the implementation of a simulation framework to evaluate an emerging peer-to-peer network topology scheme using 8-point hypercircles, entitled HyperCircle. This topology was proposed in order to alleviate some of the drawbacks of current P2P systems evolving in an uncontrolled manner, such as scalability issues, network overload and long search times. The framework is supposed to be used to evaluate the advantages of this new topology. The framework has been built on top of an existing simulator software solution, the selection of which was an important part of the development. Weighing different variables such as scalability and API usability, the selection fell on OverSim, an open-source discreet-event simulator based on OMNET++.

    After formalizing the protocol for easier implementation, as well as extending it for better performance, implementation followed using C++ with OverSim’s API and simulation library. Implemented as a module (alongside other stock modules providing their own protocols such as Chord and Kademlia), it can be used in OverSim to simulate a user-defined network using one of the simulation routine applications provided (or using a custom application written by the user). For the purposes of this thesis, the standard application KBRTestApp was used; an application sending test messages between randomly selected nodes, while adding and removing nodes at specific time intervals. The adding and removing of nodes can be configured with probability parameters.

    Tentative testing shows that this implementation of the HyperCircle protocol has a certain performance gain over the OverSim implementations of the Chord and Kademlia protocols, measurable in the time it takes a message to get from sender to recipient. Further testing is outside the scope of this thesis.

  • 2.
    Abdulla, PA
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Computer Systems. DEPARTMENT OF COMPUTER SYSTEMS.
    Boasson, L
    Bouajjani, A
    Effective Lossy Queue Languages.2001In: ICALP'2001, 28th Int. Colloquium on Automata, Languages and Programmming., 2001Conference paper (Refereed)
  • 3.
    Abdulla, PA
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. DEPARTMENT OF COMPUTER SYSTEMS.
    Jonsson, B
    Channel Abstractions in Protocol Verification2001In: CONCUR'2001, 12th Int. Conf. on Concurrency Theory, 2001Conference paper (Refereed)
  • 4.
    Abdulla, Parosh A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Univ Genoa, DIBRIS, Genoa, Italy..
    Parameterized verification2016In: International Journal on Software Tools for Technology Transfer (STTT), ISSN 1433-2779, E-ISSN 1433-2787, Vol. 18, no 5, 469-473 p.Article in journal (Other academic)
    Abstract [en]

    The goal of parameterized verification is to prove the correctness of a system specification regardless of the number of its components. The problem is of interest in several different areas: verification of hardware design, multithreaded programs, distributed systems, and communication protocols. The problem is undecidable in general. Solutions for restricted classes of systems and properties have been studied in areas like theorem proving, model checking, automata and logic, process algebra, and constraint solving. In this introduction to the special issue, dedicated to a selection of works from the Parameterized Verification workshop PV '14 and PV '15, we survey some of the works developed in this research area.

  • 5.
    Abdulla, Parosh A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Univ Genoa, Genoa, Italy..
    Montali, Marco
    Free Univ Bolzano, Bolzano, Italy..
    Well Structured Transition Systems with History2015In: Electronic Proceedings in Theoretical Computer Science, ISSN 2075-2180, E-ISSN 2075-2180, no 193, 115-128 p.Article in journal (Refereed)
    Abstract [en]

    We propose a formal model of concurrent systems in which the history of a computation is explicitly represented as a collection of events that provide a view of a sequence of configurations. In our model events generated by transitions become part of the system configurations leading to operational semantics with historical data. This model allows us to formalize what is usually done in symbolic verification algorithms. Indeed, search algorithms often use meta-information, e.g., names of fired transitions, selected processes, etc., to reconstruct (error) traces from symbolic state exploration. The other interesting point of the proposed model is related to a possible new application of the theory of well-structured transition systems (wsts). In our setting wsts theory can be applied to formally extend the class of properties that can be verified using coverability to take into consideration (ordered and unordered) historical data. This can be done by using different types of representation of collections of events and by combining them with wsts by using closure properties of well-quasi orderings.

  • 6. Abdulla, Parosh Aziz
    Carrying Probabilities to the Infinite World2011In: CONCUR'2011, 22nd International Conference on Concurrency Theory., 2011Conference paper (Refereed)
  • 7.
    Abdulla, Parosh Aziz
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. DEPARTMENT OF COMPUTER SYSTEMS.
    Using (Timed) Petri Nets for Verification of Parametrized (Timed) Systems2001In: VEPAS'2001, Verification of Parameterized Systems, 2001Conference paper (Refereed)
  • 8.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Atig, Mohamed Faouzi
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Kaxiras, Stefanos
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Leonardsson, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Ros, Alberto
    Zhu, Yunyun
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Fencing programs with self-invalidation and self-downgrade2016In: Formal Techniques for Distributed Objects, Components, and Systems, Springer, 2016, 19-35 p.Conference paper (Refereed)
  • 9.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Chen, Yu-Fang
    Clemente, Lorenzo
    Holík, Lukás
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Hong, Chih-Duo
    Mayr, Richard
    Vojnar, Tomás
    Advanced Ramsey-based Büchi automata inclusion testing2011In: CONCUR 2011 — Concurrency Theory, Springer Berlin/Heidelberg, 2011, 187-202 p.Conference paper (Refereed)
  • 10.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Delzanno, Giorgio
    Univ Genoa, I-16126 Genoa, Italy..
    Rezine, Othmane
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Uppsala Univ, Uppsala, Sweden..
    Sangnier, Arnaud
    Univ Paris Diderot, CNRS, LIAFA, Paris, France..
    Traverso, Riccardo
    FBK, Trento, Italy..
    Parameterized verification of time-sensitive models of ad hoc network protocols2016In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 612, 1-22 p.Article in journal (Refereed)
    Abstract [en]

    We study decidability and undecidability results for parameterized verification of a formal model of timed Ad Hoc network protocols. The communication topology is defined by an undirected graph and the behaviour of each node is defined by a timed automaton communicating with its neighbours via broadcast messages. We consider parameterized verification problems formulated in terms of reachability. In particular we are interested in searching for an initial configuration from which an individual node can reach an error state. We study the problem for dense and discrete time and compare the results with those obtained for (fully connected) networks of timed automata.

  • 11.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology.
    Delzanno, Giorgio
    Van Begin, Laurent
    A classification of the expressive power of well-structured transition systems2011In: Information and Computation, ISSN 0890-5401, E-ISSN 1090-2651, Vol. 209, no 3, 248-279 p.Article in journal (Refereed)
    Abstract [en]

    We compare the expressive power of a class of well-structured transition systems that includes relational automata (extensions of), Petri nets, lossy channel systems, constrained multiset rewriting systems, and data nets. For each one of these models we study the class of languages generated by labeled transition systems describing their semantics. We consider here two types of accepting conditions: coverability and reachability of a fixed a priori configuration. In both cases we obtain a strict hierarchy in which constrained multiset rewriting systems is the most expressive model.

  • 12.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Datorteknik.
    Jonsson, Bengt
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Datorteknik.
    Model checking of systems with many identical timed processes2003In: Theoretical Computer Science, ISSN 0304-3975, Vol. 290, no 1, 241-264 p.Article in journal (Refereed)
  • 13. Abdulla, Parosh Aziz
    et al.
    Leino, Rustan
    TACAS'2011, 17th International ConferenceTools and Algorithms for the Construction and Analysis of Systems.2011Conference proceedings (editor) (Refereed)
  • 14.
    Abdulla, Parosh Aziz
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Richard, Mayr
    Computing Optimal Coverability Costs in Priced Timed Petri Nets2011In: LICS'2011, Proceedings of the 26th Annual IEEE Symposium on Logic in Computer Science, 2011, 399-408 p.Conference paper (Refereed)
    Abstract [en]

    We consider timed Petri nets, i.e., unbounded Petri nets where each token carries a real-valued clock. Transition arcs are labeled with time intervals, which specify constraints on the ages of tokens. Our cost model assigns token storage costs per time unit to places, and firing costs to transitions. We study the cost to reach a given control-state. In general, a cost-optimal run may not exist. However, we show that the infimum of the costs is computable.

  • 15.
    Abdulla, Parosh
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Computer Systems. DoCS.
    Ben Henda, Noomene
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Computer Systems. DoCS.
    Mayr, Richard
    Sandberg, Sven
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Mathematics and Computer Science, Department of Information Technology, Computer Systems. Datalogi.
    Limiting Behavior of Markov Chains with Eager Attractors2006In: Third International Conference on the Quantitative Evaluation of Systems (QEST), 2006, 253-262 p.Conference paper (Refereed)
  • 16.
    Abrahamsson, Björn
    Linköping University, Department of Electrical Engineering.
    Architectures for Multiplication in Galois Rings2004Independent thesis Basic level (professional degree)Student thesis
    Abstract [en]

    This thesis investigates architectures for multiplying elements in Galois rings of the size 4^m, where m is an integer.

    The main question is whether known architectures for multiplying in Galois fields can be used for Galois rings also, with small modifications, and the answer to that question is that they can.

    Different representations for elements in Galois rings are also explored, and the performance of multipliers for the different representations is investigated.

  • 17.
    Abrahamsson, Henrik
    Mälardalen University, School of Innovation, Design and Engineering.
    Internet Traffic Management2008Licentiate thesis, comprehensive summary (Other scientific)
  • 18.
    Abrahamsson, Henrik
    Mälardalen University, School of Innovation, Design and Engineering.
    Network overload avoidance by traffic engineering and content caching2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Internet traffic volume continues to grow at a great rate, now driven by video and TV distribution. For network operators it is important to avoid congestion in the network, and to meet service level agreements with their customers.  This thesis presents work on two methods operators can use to reduce links loads in their networks: traffic engineering and content caching.

    This thesis studies access patterns for TV and video and the potential for caching.  The investigation is done both using simulation and by analysis of logs from a large TV-on-Demand system over four months.

    The results show that there is a small set of programs that account for a large fraction of the requests and that a comparatively small local cache can be used to significantly reduce the peak link loads during prime time. The investigation also demonstrates how the popularity of programs changes over time and shows that the access pattern in a TV-on-Demand system very much depends on the content type.

    For traffic engineering the objective is to avoid congestion in the network and to make better use of available resources by adapting the routing to the current traffic situation. The main challenge for traffic engineering in IP networks is to cope with the dynamics of Internet traffic demands.

    This thesis proposes L-balanced routings that route the traffic on the shortest paths possible but make sure that no link is utilised to more than a given level L. L-balanced routing gives efficient routing of traffic and controlled spare capacity to handle unpredictable changes in traffic.  We present an L-balanced routing algorithm and a heuristic search method for finding L-balanced weight settings for the legacy routing protocols OSPF and IS-IS. We show that the search and the resulting weight settings work well in real network scenarios.

  • 19.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Caching for IPTV distribution with time-shift2013In: 2013 International Conference on Computing, Networking and Communications, ICNC 2013, IEEE , 2013, 916-921 p.Conference paper (Refereed)
    Abstract [en]

    Today video and TV distribution dominate Internet traffic and the increasing demand for high-bandwidth multimedia services puts pressure on Internet service providers. In this paper we simulate TV distribution with time-shift and investigate the effect of introducing a local cache close to the viewers. We study what impact TV program popularity, program set size, cache replacement policy and other factors have on the caching efficiency. The simulation results show that introducing a local cache close to the viewers significantly reduces the network load from TV-on-Demand services. By caching 4% of the program volume we can decrease the peak load during prime time by almost 50%. We also show that the TV program type and how program popularity changes over time can have a big influence on cache hit ratios and the resulting link loads

  • 20.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science.
    Björkman, Mats
    Mälardalen University, School of Innovation, Design and Engineering.
    Simulation of IPTV caching strategies2010In: Proceedings of the 2010 International Symposium on Performance Evaluation of Computer and Telecommunication Systems, 2010, 187-193 p.Conference paper (Refereed)
    Abstract [en]

    IPTV, where television is distributed over the Internet Protocol in a single operator network, has become popular and widespread. Many telecom and broadband companies have become TV providers and distribute TV channels using multicast over their backbone networks. IPTV also means an evolution to time-shifted television where viewers now often can choose to watch the programs at any time. However, distributing individual TV streams to each viewer requires a lot of bandwidth and is a big challenge for TV operators. In this paper we present an empirical IPTV workload model, simulate IPTV distribution with time-shift, and show that local caching can limit the bandwidth requirements significantly.

  • 21.
    Abrahamsson, Henrik
    et al.
    Swedish Institute of Computer Science, Kista, Sweden.
    Nordmark, Mattias
    TeliaSonera AB, Stockholm, Sweden .
    Program popularity and viewer behaviour in a large TV-on-Demand system2012In: IMC '12 Proceedings of the 2012 ACM conference on Internet measurement conference, New York: ACM , 2012, 199-210 p.Conference paper (Refereed)
    Abstract [en]

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

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

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

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

  • 22.
    Abrahamsson, Lars
    Linköping University, Department of Electrical Engineering.
    A portal based system for indoor environs2006Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    The purpose of this thesis is to document the development of the graphics part of an extremely pluggable game engine/lab environment for a course in advanced game programming. This thesis is one out of five, and concerns indoor, realtime computer 3D graphics. It covers state-of-the-art techniques such as GLSL - the OpenGL Shading Language - and more well known techniques such as portal based rendering.

  • 23.
    Abrahamsson, Marcus
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    A platform for third-party applications on the web2013Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    A trend seen on the web today is to create a platform where externally developed applications can run inside some kind of main application. This is often done by providing an API to access data and business logic of your service and a sandbox environment in which third-party applications can run. By providing this, it is made possible for external developers to come up with new ideas based on your service. Some good examples on this are Spotify Apps, Apps on Facebook and SalesForce.com.

    Ipendo Systems AB is a company that develops a web platform for intellectual properties. Currently most things on this platform are developed by developers at Ipendo Systems AB. Some interest has though risen to enable external developers to create applications that will in some way run inside the main platform.

    In this thesis an analysis of already existing solutions has been done. These solutions were Spotify Apps and Apps on Facebook. The two have different approaches on how to enable third-party applications to run inside their own service. Facebook’s solution builds mainly on iframe embedded web pages where data access is provided through a web API. Spotify on the other hand hosts the third-party applications themselves but the applications may only consist of HTML5, CSS3 and JavaScript.

    In addition to the analysis a prototype was developed. The purpose of the prototype was to show possible ways to enable third-party applications to run inside your own service. Two solutions showing this were developed. The first one was based on Facebook’s approach with iframing of external web pages. The second was a slightly modified version of Spotify’s solution with only client-side code hosted by the main application. To safely embed the client side code in the main application a sandboxing tool for JavaScript called Caja was used.

    Of the two versions implemented in the prototype was the Iframe solution considered more ready to be utilized in a production environment than Caja. Caja could be seen as an interesting technique for the future but might not be ready to use today. The reason behind this conclusion was that Caja decreased the performance of the written JavaScript as well as adding complexity while developing the third-party applications.

  • 24.
    Abrahamsson, Robin
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Berntsen, David
    Linköping University, Department of Computer and Information Science, Software and Systems.
    Comparing modifiability of React Native and two native codebases2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Creating native mobile application on multiple platforms generate a lot of duplicate code. This thesis has evaluated if the code quality attribute modifiability improves when migrating to React Native. One Android and one iOS codebase existed for an application and a third codebase was developed with React Native. The measurements of the codebases were based on the SQMMA-model. The metrics for the model were collected with static analyzers created specifically for this project. The results created consists of graphs that show the modifiability for some specific components over time and graphs that show the stability of the platforms. These graphs show that when measuring code metrics on applications over time it is better to do this on a large codebase that has been developed for some time. When calculating a modifiability value the sum of the metrics and the average value of the metrics between files should be used and it is shown that the React Native platform seems to be more stable than native.

  • 25.
    Adolfsson, Klas
    Linköping University, Department of Electrical Engineering.
    TCP performance in an EGPRS system2003Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    The most widely used protocol for providing reliable service and congestion control in the Internet is the Transmission Control Protocol (TCP). When the Internet is moving towards more use in mobile applications it is getting more important to know how TCP works for this purpose.

    One of the technologies used for mobile Internet is the Enhanced General Packet Radio Service (EGPRS) extension to the popular GSM system. This thesis presents a low-level analysis of TCP performance in an EGPRS system and an overview of existing TCP, GSM and EGPRS technologies.

    The bottleneck in an EGPRS system is the wireless link – the connection between the mobile phone and the GSM base station. The data transfer over the wireless link is mainly managed by the complex RLC/MAC protocol.

    In this thesis, simulations were made to identify some problems with running TCP and RLC/MAC together. The simulations were made using existing EGPRS testing software together with a new TCP module. The simulation software is also briefly described in the thesis.

    Additionaly, some suggestions are given in order to enhance performance, both by changing the EGPRS system and by modifying the TCP algorithms and parameters.

  • 26.
    Afshar, Sara
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bril, Reinder J.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. Technische Universiteit Eindhoven, Eindhoven, Netherlands.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Resource Sharing Under Global Scheduling with Partial Processor Bandwidth2015In: 2015 10th IEEE International Symposium on Industrial Embedded Systems, SIES 2015 - Proceedings, 2015, 195-206 p.Conference paper (Refereed)
    Abstract [en]

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

  • 27.
    Agelis, Sacki
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Jacobsson, Sofia
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Jonsson, Magnus
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Alping, Arne
    Ericsson Microwave Systems, Mölndal, Sweden.
    Ligander, Per
    Ericsson Microwave Systems, Mölndal, Sweden.
    Modular interconnection system for optical PCB and backplane communication2002In: Parallel and Distributed Processing Symposium., Proceedings International, IPDPS 2002, Abstracts and CD-ROM, Los Alamitos, Calif.: IEEE Press, 2002, 245-250 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a way of building modular systems with a powerful optical interconnection network. Each module, placed on a Printed Circuit Board (PCB), has a generic optical communication interface with a simple electronic router. Together with optical switching using micro-electromechanical system (MEMS) technology, packet switching over reconfigurable topologies is possible. The interconnection system gives the possibility to integrate electronics with optics without changing existing PCB technology. Great interest from industry is therefore expected and the cost advantages are several: reuse of module designs, module upgrades without changing the PCB, low-cost conventional PCB technology, etc. In the version described in this paper, the interconnection system has 48 bidirectional optical channels for intra-PCB communication on each board. For inter-PCB communication, a backplane with 192 bidirectional optical channels supports communication between twelve PCBs. With 2.5 Gbit/s per optical channel in each direction, the aggregated intra-PCB bit rate is 120 Gbit/s full duplex (on each PCB) while the aggregated inter-PCB bit rate is 480 Gbit/s full duplex. A case study shows the feasibility of the interconnection system in a parallel processing system for radar signal processing.

  • 28.
    Agelis, Sacki
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Jonsson, Magnus
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Optoelectronic router with MOEMS–based reconfigurable shuffle network2004Conference paper (Refereed)
  • 29.
    Agrawal, P.
    et al.
    Uppsala Universitet.
    Ahlén, Anders
    Uppsala Universitet.
    Olofsson, Tomas
    Uppsala Universitet.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Long Term Channel Characterization for Energy Efficient Transmission in Industrial Environments2014In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 62, no 8, 3004-3014 p.Article in journal (Refereed)
    Abstract [en]

    One of the challenges for a successful use of wireless sensor networks in process industries is to design networks with energy efficient transmission, to increase the lifetime of the deployed network while maintaining the required latency and bit-error rate. The design of such transmission schemes depend on the radio channel characteristics of the region. This paper presents an investigation of the statistical properties of the radio channel in a typical process industry, particularly when the network is meant to be deployed for a long time duration, e.g., days, weeks, and even months. Using 17–20-h-long extensive measurement campaigns in a rolling mill and a paper mill, we highlight the non-stationarity in the environment and quantify the ability of various distributions, given in the literature, to describe the variations on the links. Finally, we analyze the design of an optimal received signal-to-noise ratio (SNR) for the deployed nodes and show that improper selection of the distribution for modeling of the variations in the channel can lead to an overuse of energy by a factor of four or even higher.

  • 30.
    Agrawal, Piyush
    et al.
    Uppsala University.
    Ahlén, Anders
    Uppsala University.
    Olofsson, Tomas
    Uppsala University.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Characterization of Long Term Channel Variations in Industrial Wireless Sensor Networks2014In: IEEE International Conference on Communications (ICC'14), IEEE conference proceedings, 2014Conference paper (Refereed)
  • 31.
    Ahlberg, Tobias
    et al.
    University of Kalmar, School of Communication and Design.
    Södergren, Marcus
    University of Kalmar, School of Communication and Design.
    Voss, Martin
    University of Kalmar, School of Communication and Design.
    Microsoft Windows Server 2008 Terminal Services vs. Citrix XenApp2008Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Den här rapporten undersöker om gränsen mellan Terminal Services och Citrix XenApp har börjat suddas ut eller om man ännu kan dra en tydlig linje mellan dessa. Detta för att avgöra om organisationer som idag kör Windows Server 2003 med Citrix XenApp enbart klarar sig med de nya funktionerna i Windows Server 2008 Terminal Services och ändå uppfylla de krav och behov en organisation har. Arbetet genomfördes rent teoretiskt. För att avgöra likheter och skillnader mellan applikationerna, så användes till största delen ett ramverk. För att kunna få en bild av hur applikationerna tillämpas rent praktiskt, användes tidigare testar samt analyser. Resultatet visar att Terminal Services tagit ett större steg inom marknaden för applikationsvirtualisering. Slutsatsen antyder att Windows Server 2008 Terminal Services är lämplig för organisationer utan komplexa behov.

  • 32.
    Ahlgren, Bengt
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Computer Systems. Swedish Institute of Computer Science.
    Improving Computer Communication Performance by Reducing Memory Bandwidth Consumption1997Doctoral thesis, comprehensive summary (Other academic)
  • 33.
    Ahlström, Daniel
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Minimizing memory requirements for deterministic test data in embedded testing2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Embedded and automated tests reduce maintenance costs for embedded systems installed in remote locations. Testing multiple components of an embedded system, connected on a scan chain, using deterministic test patterns stored in a system provide high fault coverage but require large system memory. This thesis presents an approach to reduce test data memory requirements by the use of a test controller program, utilizing the observation of that there are multiple components of the same type in a system. The program use deterministic test patterns specific to every component type, which is stored in system memory, to create fully defined test patterns when needed. By storing deterministic test patterns specific to every component type, the program can use the test patterns for multiple tests and several times within the same test. The program also has the ability to test parts of a system without affecting the normal functional operation of the rest of the components in the system and without an increase of test data memory requirements. Two experiments were conducted to determine how much test data memory requirements are reduced using the approach presented in this thesis. The results for the experiments show up to 26.4% reduction of test data memory requirements for ITC´02 SOC test benchmarks and in average 60% reduction of test data memory requirements for designs generated to gain statistical data.

  • 34.
    Ahmed, Iftikhar
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Farooq, Muhammad
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Switched Multi-hop Priority Queued Networks-Influence of priority levels on Soft Real-time Performance2010Independent thesis Advanced level (degree of Master (One Year)), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    In the last few years, the number of real-time applications has increased. These applications are sensitive and require the methods to utilize existing network capacity efficiently to meet performance requirements and achieve the maximum throughput to overcome delay, jitter and packet loss. In such cases, when the network needs to support highly interactive traffic like packet-switched voice, the network congestion is an issue that can lead to various problems. If the level of congestion is high enough, the users may not be able to complete their calls and have existing calls dropped or may experience a variety of delays that make it difficult to participate smooth conversation.

    In this paper, we investigate the effect of priority levels on soft real-time performance. We use the priority queues to help us manage the congestion, handle the interactive traffic and improve the over all performance of the system. We consider switched multi-hop network with priority queues. All the switches and end-nodes control the real-time traffic with “Earlier Deadline First” scheduling. The performance of the network is characterized in terms of the average delay, the deadline missing ratio and the throughput.

    We will analyze these parameters with both the bursty traffic and evenly distributed traffic. We will analyze different priority levels and will see how the increase in priority level increases the performance of the soft real-time system.

  • 35.
    Ahmed, Olfet
    et al.
    KTH, School of Technology and Health (STH), Data- och elektroteknik.
    Saman, Nawar
    KTH, School of Technology and Health (STH), Data- och elektroteknik.
    Utvärdering av nätverkssäkerheten på J Bil AB2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this project is to evaluate the network security at J Bil AB. The focus will be on both social and technical issues. For the employees to be able to con-nect to remote servers and external services and perform their daily work tasks, secure connections is needed. J Bil Ab has no IT manager who actively maintains and monitors the network; rather they consult a computer company when changes and implementations are required. The projects’ goal is to identify gaps, come up with suggestions for improvement and to some extent implement so-lutions. To do this, an observation of the employees hav been made, an inter-view have been held, and several attacks on the network have been performed. Based on the data collected, it was concluded that the company has shortcom-ings in IT security. Above all, the social security appeared to have major gaps in it and that is mainly because the lack of knowledge among the employees and they have never been informed of how to manage their passwords, computers and IT issues in general. Suggestions for improvement have been given and some implementations have been performed to eliminate the deficiencies.

  • 36.
    Ahmed, Tanvir
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Garrido, Mario
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Gustafsson, Oscar
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A 512-point 8-parallel pipelined feedforward FFT for WPAN2011In: 2011 Conference Record of the Forty Fifth Asilomar Conference on Signals, Systems and Computers (ASILOMAR), IEEE , 2011, 981-984 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a 512-point feedforward FFT architecture for wireless personal area network (WPAN). The architecture processes a continuous flow of 8 samples in parallel, leading to a throughput of 2.64 GSamples/s. The FFT is computed in three stages that use radix-8 butterflies. This radix reduces significantly the number of rotators with respect to previous approaches based on radix-2. Besides, the proposed architecture uses the minimum memory that is required for a 512-point 8-parallel FFT. Experimental results show that besides its high throughput, the design is efficient in area and power consumption, improving the results of previous approaches. Specifically, for a wordlength of 16 bits, the proposed design consumes 61.5 mW and its area is 1.43 mm2.

  • 37.
    Ahmed, Tanvir Saif
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Markovic, Bratislav
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Distribuerade datalagringssystem för tjänsteleverantörer: Undersökning av olika användningsfall för distribuerade datalagringssystem2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this thesis, a study of three different uses cases has been made within the field of data storage, which are as following: Cold Storage, High Performance Storage and Virtual Machine Storage. The purpose of the survey is to give an overview of commercial distributed file systems and a deeper study of open source codes distributed file systems in order to find the most optimal solution for these use cases. Within the study, previous works concerning performance, data protection and costs were an-alyzed and compared in means to find different functionalities (snapshotting, multi-tenancy, data duplication and data replication) which distinguish modern distributed file systems. Both commercial and open distributed file systems were examined. A cost estimation for commercial and open distrib-uted file systems were made in means to find out the profitability for these two types of distributed file systems.After comparing and analyzing previous works, it was clear that the open source distributed file sys-tem Ceph was proper as a solution in accordance to the objectives that were set for High Performance Storage and Virtual Machine Storage. The cost estimation showed that it was more profitable to im-plement an open distributed file system. This study can be used as guidance to choose between different distributed file systems.

  • 38.
    Ahrengart, Hugo
    et al.
    Linköping University, Department of Computer and Information Science.
    Borg, Therese
    Linköping University, Department of Computer and Information Science.
    Magnuson, David
    Linköping University, Department of Computer and Information Science.
    Nilsson, Victor
    Linköping University, Department of Computer and Information Science.
    Partain, Beatrice
    Linköping University, Department of Computer and Information Science.
    Voss-Lagerlund, Carl
    Linköping University, Department of Computer and Information Science.
    Wagner, Mattias
    Linköping University, Department of Computer and Information Science.
    Awesome Fragrance Company: Utveckling av en e-butik för parfymprover2016Independent thesis Basic level (degree of Bachelor), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    This bachelor's thesis accounts for the results and takeaways from the process of developing the web application for Awesome Fragrance Company. The goal of this thesis is to provide an increased understanding of how a usable web application can be designed, by studying the development of an online store with the purpose of selling fragrance samples. The agile method Scrum has been the foundation of the development, and based on this, the focus has been to develop a continuously deliverable product, where functionality is added in increments. By starting with a rough prototype and then gradually adjusting the final vision for the product based on feedback, the group has developed an online store which, according to users, is usable and intuitive. Thus, the group has created a foundation for further research on usable web applications, which was the goal of the project.

  • 39.
    Akbar, Adnan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Influencing Factors on Quality of Experience (QoE) in Mobile Computing2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Applications that can change their behaviour based on the user’s contextual appearance are called context-aware applications. Applications developed for smart phones, which carry a multitude of different sensors, and actuators have gained a huge penetration within the market. Frequent usage of mobile applications such as home automation, friend finder, car accident notification and tracking etc; have seen an increased growth from the user’s perspective. However, for such applications, it is necessary to have knowledge of the performance and cost parameters, which directly affect the QoE of the application users.  This thesis investigates possible context aware behaviours in real time situations and measures the Quality of Experience (QoE) as well as identifying the Packet Delay Variation (PDV). The background and some state-of-the-art technologies are studied, and based on these studies, three scenarios are designed and implemented and based on their QoE, results and conclusions are presented, with the  results obtained  shown by means of   graphical representations of the QoE and PDV values. 

  • 40.
    Alazawi, Salah
    et al.
    ISY, DATORSYSTEM, DI.
    Alilovic, Bojan
    ISY, DATORSSYTEM, DI.
    Konstruktion av Ethernet-baserad Qbussförlängare2008Independent thesis Basic level (degree of Bachelor), 10 points / 15 hpStudent thesis
    Abstract [sv]

     

    Syftet med var att konstruera ett bussförlängartkort till Qbussen som gör Ethernet-baserad kommunikation med I/O:t möjlig. Kortet ska kunna anslutas till standard 100 Mbits nätverksutrustning och klara autoförhandling och låsning av hastighet och duplex. Detta minskar på många ställen kabeldragningen väsentligt och det är därför önskvärt att SSAB:s egna I/O ska kunna köras så över Ethernet, antingen över vanliga nätverket eller på dedikerad kabel.

  • 41.
    Albertson, Philip
    Växjö University, Faculty of Mathematics/Science/Technology, School of Mathematics and Systems Engineering.
    WBD – Web Based Diagnostics: Identifierande av parametrar på CAN-bussen2007Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This abstract describes the bachelor degree thesis in computer technology at Växjö University written by Philip Albertson during the spring term of 2007. At the company BSR in Växjö, Sweden there is a new project under development called WBD – Web based diagnostics. The aim of the project is to make car diagnostics available to ordinary people at a decent cost. The system consists of three parts; a module to plug in the car, a server to handle the information and a client to allow the customers to reach the information about their car. My part in this project was to specify how to reach certain parameters on the CAN-bus in cars from VAG (Volkswagen Auto Group) and Saab. The company was satisfied with the results since they provided a good basis to further develop the module prototype built by the company EDAB (Elektronik Design AB) in Sundsvall, Sweden.

  • 42.
    Alekic, Anis
    et al.
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Carmvall, Andreas
    Linnaeus University, Faculty of Science and Engineering, School of Computer Science, Physics and Mathematics.
    Displayintegrering2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This abstract describes the Bachelor of Science in engineering thesis for computer science at Linnaeus University. Arcoma AB in Växjö is a company that constructs and develops complete x-ray systems. The goal of the company is to improve the usability of the system with the help of a LED display. Arcoma can improve the system by exchange the unit that controls the x-ray generator with the LED display instead. This will give the user the ability to have better overview and control of the system, while treating the patient.

    This report describes the implementation of both the software and the hardware for the display, but also the technical background for some standards like HDMI and the LED technologic. The software has been tested directly to the display, and therefore made the testing interesting. We have used the Arcoma system and the development tools to solve the problem. The programming language that was used to solve the problem was mainly C++.

    The result was a system that is build up by the Arcoma hardware platform, our surrounding electronics and the display where the last ones were built in a box. Aside the display a demo application was developed for controlling the generator. This applications is controlled by a USB mouse. Arcoma is pleased with the result of the main problem with the display, and they are also pleased with us solving the additional problems that existed. Arcoma wants to create a demand of this solution in their new products.

  • 43. Alesii, Roberto
    et al.
    Congiu, Roberto
    Santucci, Fortunato
    Di Marco, Piergiuseppe
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Architectures and protocols for fast identification in large-scale RFID systems2014In: ISCCSP 2014 - 2014 6th International Symposium on Communications, Control and Signal Processing, Proceedings, 2014, 243-246 p.Conference paper (Refereed)
    Abstract [en]

    Passive tags based on backscattered signals yield low energy consumption for large-scale applications of RFIDs. In this paper, system architectures and protocol enhancements for fast identifications in ISO/IEC 18000-6C systems that integrate UWB technology are investigated. The anti-collision protocol is studied by considering various tag populations. A novel algorithm is proposed to adapt the UHF air interface parameters with the use of UWB ranging information. The results show that the proposed algorithm yields up to 25% potential performance improvement compared to the ISO/IEC 18000-6C standard.

  • 44.
    Alfredsson, Erik
    Linköping University, Department of Electrical Engineering.
    Design and implementation of a hardware unit for complex division2005Independent thesis Basic level (professional degree), 20 points / 30 hpStudent thesis
    Abstract [en]

    The purpose of the thesis was to investigate and evaluate existing algorithms for division of complex numbers. The investigation should include implementation of a few suitable algorithms in VHDL. The main application for the divider is compensation for fading in a baseband processor.

    Since not much public research is done within the area of complex division in hardware, a divider based on real valued division was designed. The design only implements inversion of complex numbers instead of complete division because it is simpler and the application does not need full division, thus the required chip size is reduced.

    An examination of the different kinds of algorithms that exists for real valued division was done and two of the methods were found suitable for implementation, digit recurrence and functional iteration. From each of the two classes of algorithms one algorithm was chosen and implemented in VHDL. Two different versions of the inverter were designed for each method, one with full throughput and one with half throughput. The implementations show very similar results in terms of speed, size and performance. For most cases however, the digit recurrence implementation has a slight advantage.

  • 45.
    Alfredsson, Jonas
    Linköping University, Department of Electrical Engineering.
    Portning av ett plugin till 3d-modelleringsprogram2008Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report describes the work and the results found when comparing three different 3d modeler applications. The programs are 3ds Max, Maya and Cinema 4D. The comparisons focus on the possibilities/the amount of freedom these programs interface offer to its plugins. The comparisons are made from the point of view of a tool for creating animations developed as a plugin for these modelers. This plugins demands on the system it is loaded into have been analyzed and from the results of this analysis a template have been created. This template is to be used when porting the plugin to other modeler programs in order to be able to tell at an early stage if it’s possible, or not. This template is appended as an appendix. The plugin described above is in it self a system with a plugin architecture and is described on a higher level in the report.

  • 46.
    Al-Ghareeb, Meelad
    et al.
    Jönköping University, School of Engineering, JTH, Computer Science and Informatics.
    Antranik, Sevag
    Riktlinjer för grafiska användargränssnitt för lagersystem2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Syftet med denna rapport är att undersöka och sammanställa riktlinjer för att utveckla ett grafiskt användargränssnitt för ett lagersystem. För att uppnå syftet med rapporten litteraturstudier, intervjuer, observationer och en prototyputveckling utfördes. Utifrån litteraturstudier visade det sig att det inte fanns specifika designriktlinjer för utveckling av lagersystem fast det fanns allmänna riktlinjer som kan användas för design av olika system. Intervjuer med utvecklare och en utvecklingschef på företaget Qsys hjälpte till att hitta befintliga riktlinjer som företaget använder. Det visade sig att de använder allmänna riktlinjer som inte är specifika för lagersystem. För att hitta mer specifika riktlinjer observerade vi några lagerarbetare för att bättre förstå hur de integrerar med det befintliga systemet som de använder. Utifrån analysen av observationerna, upptäcktes det nya riktlinjer. Med hjälp av de allmänna riktlinjer som hittades i litteraturen och riktlinjer som upptäckes efter analysen av observationer, utvecklade vi en prototyp som sedan testades. Resultatet vi fick utifrån analysen av intervjuerna med lagerarbetarna efter prototyptestning, hjälpte med att hitta ytterligare specifika riktlinjer.För att utveckla ett användarvänligt lagersystem, behöver man ett användarvänligt gränssnitt. I denna rapport presenterar vi några riktlinjer som man kan använda sig av för att utveckla ett användarvänligt gränssnitt för lagersystem.

  • 47.
    Ali Arslan, Mehmet
    et al.
    Lund University, Sweden.
    Gruian, Flavius
    Lund University, Sweden.
    Kuchcinski, Krzysztof
    Lund University, Sweden.
    Karlsson, Andreas
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Code Generation for a SIMD Architecture with Custom Memory Organisation2016In: PROCEEDINGS OF THE 2016 CONFERENCE ON DESIGN AND ARCHITECTURES FOR SIGNAL and IMAGE PROCESSING, IEEE , 2016, 90-97 p.Conference paper (Refereed)
    Abstract [en]

    Todays multimedia and DSP applications impose requirements on performance and power consumption that only custom processor architectures with SIMD capabilities can satisfy. However, the specific features of such architectures, including vector operations and high-bandwidth complex memory organization, make them notoriously complicated and time consuming to program. In this paper we present an automated code generation approach that dramatically reduces the effort of programming such architectures, by carrying out instruction scheduling and memory allocation based on a constraint programming formulation. Furthermore, the quality of the generated code is close to that of hand-written code by an experienced programmer with knowledge of the architecture. We demonstrate the viability of our approach on an existing custom heterogeneous DSP architecture, by compiling and running a number of typical DSP kernels, and comparing the results to hand-optimized code.

  • 48.
    Ali, Hayder
    et al.
    Kristianstad University, School of Health and Society.
    Spets, Rasmus
    Kristianstad University, School of Health and Society.
    Virtualisering av skrivbordsmiljöer: en teknisk jämförelse2016Independent thesis Basic level (university diploma), 10 HE creditsStudent thesis
    Abstract [sv]

    Detta arbete syftar till en jämförelse av olika skrivbordsvirtualiserings produkter och hur respektive miljö ser ut. I utredandeavsnittet presenteras information om skrivbordsvirtualiserings olika lösningar och hur de fungerar. Arbetet redogör för de två stora aktörerna inom detta område, Citrix och VMware. Utredandeavsnittet presenterar även lite information om Nvidias grafiklösningar i de olika miljöerna. Genomförandeavsnittet presenterar information från intervjuer med representanter från de två stora aktörerna. Arbetet presenterar även information från en representant från Nvidia, USA. Intervjuerna har skett via e-mail eftersom personligt möte varit väldigt svårt att lösa. Intervjuerna behandlar frågor om respektive lösning om hur de fungerar och även om användarvänlighet och åtkomst för användare. Fokus ligger på användarvänlighet och åtkomst för användare i respektive lösning. Efter arbetet kan det dras några slutsatser. Främst att de två miljöerna som undersökts är ganska lika när det gäller virtualisering av skrivbord. De är uppbyggda på liknande sätt och fungerar på nästan samma sätt när det gäller åtkomst för användare.

  • 49.
    Ali, Hazem
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Patoary, Mohammad Nazrul Ishlam
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Design and Implementation of an Audio Codec (AMR-WB) using Dataflow Programming Language CAL in the OpenDF Environment2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    Over the last three decades, computer architects have been able to achieve an increase in performance for single processors by, e.g., increasing clock speed, introducing cache memories and using instruction level parallelism. However, because of power consumption and heat dissipation constraints, this trend is going to cease. In recent times, hardware engineers have instead moved to new chip architectures with multiple processor cores on a single chip. With multi-core processors, applications can complete more total work than with one core alone. To take advantage of multi-core processors, we have to develop parallel applications that assign tasks to different cores. On each core, pipeline, data and task parallelization can be used to achieve higher performance. Dataflow programming languages are attractive for achieving parallelism because of their high-level, machine-independent, implicitly parallel notation and because of their fine-grain parallelism. These features are essential for obtaining effective, scalable utilization of multi-core processors.

    In this thesis work we have parallelized an existing audio codec - Adaptive Multi-Rate Wide Band (AMR-WB) - written in the C language for single core processor. The target platform is a multi-core AMR11 MP developer board. The final result of the efforts is a working AMR-WB encoder implemented in CAL and running in the OpenDF simulator. The C specification of the AMR-WB encoder was analysed with respect to dataflow and parallelism. The final implementation was developed in the CAL Actor Language, with the goal of exposing available parallelism - different dataflows - as well as removing unwanted data dependencies. Our thesis work discusses mapping techniques and guidelines that we followed and which can be used in any future work regarding mapping C based applications to CAL. We also propose solutions for some specific dependencies that were revealed in the AMR-WB encoder analysis and suggest further investigation of possible modifications to the encoder to enable more efficient implementation on a multi-core target system.

  • 50.
    Ali, Wajid
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Mohammed, Shahzaan
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Analyzing Wavelength Conversion and Traffic Grooming in Optical WDM Networks2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wavelength conversion and traffic grooming have been among the most researched areas and technologies of importance in optical networking. Network performance improves significantly by relaxing the wavelength continuity constraint using wavelength converters and by improving the wavelength utilization using traffic grooming. We have done a literature review that compares the performance of wavelength conversion devices with different traffic grooming devices. This thesis work analyzes the impact of increasing the number of wavelength conversion devices and grooming capable devices using different placement schemes for our proposed network model, traffic loads and link capacities. Deciding the number and location of these devices to be used in a network is equally important. This work has been done through the simulation of different device placement scenarios and the results have been analyzed using connection blocking probability as the performance metric. Our reviews and work, correctly predict the behavior of results as demonstrated by the results of other referred literatures relating to wavelength conversion and traffic grooming.

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