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  • 101.
    Belyakhina, Tamara
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Zaslavsky, Arkady
    CSIRO, Melbourne.
    Mitra, Karan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Saguna, Saguna
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Jayaraman, Prem Prakash
    Swinburne University of Technology, Melbourne.
    DisCPAQ: Distributed Context Acquisition and Reasoning for Personalized Indoor Air Quality Monitoring in IoT-Based Systems2017In: Internet of Things, Smart Spaces, and Next Generation Networks and Systems: 17th International Conference, NEW2AN 2017, 10th Conference, ruSMART 2017, Third Workshop NsCC 2017, St. Petersburg, Russia, August 28–30, 2017, Proceedings / [ed] Galinina O., Andreev S., Balandin S., Koucheryavy Y., Cham: Springer, 2017, p. 75-86Conference paper (Refereed)
    Abstract [en]

    The rapidly emerging Internet of Things supports many diverse applications including environmental monitoring. Air quality, both indoors and outdoors, proved to be a significant comfort and health factor for people. This paper proposes a smart context-aware system for indoor air quality monitoring and prediction called DisCPAQ. The system uses data streams from air quality measurement sensors to provide real-time personalised air quality service to users through a mobile app. The proposed system is agnostic to sensor infrastructure. The paper proposes a context model based on Context Spaces Theory, presents the architecture of the system and identifies challenges in developing large scale IoT applications. DisCPAQ implementation, evaluation and lessons learned are all discussed in the paper.

  • 102.
    Belyakov, Stanislav Leonidovich
    et al.
    Southern Federal University, Department of Applied Information Science Taganrog.
    Savelyeva, Marina
    Southern Federal University, Department of Applied Information Science Taganrog.
    Yan, Jeffrey
    Department of Electrical and Computer System Engineering, University of Auckland, University of Auckland.
    Vyatkin, Valeriy
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Adaptation of Material Flows in Mechanical Transportation Systems Based on Observation Experience2015In: IEEE TrustCom-BigDataSE-ISPA 2015: Helsinki, 20-22 Aug. 2015, Piscataway, NJ: IEEE Communications Society, 2015, p. 269-274, article id 7345659Conference paper (Refereed)
    Abstract [en]

    This paper investigates adaptation of material flows in mechanical transportation systems to the appearance of local overloads. The adaptation mechanism is based on the deflection of the forecast of experts who oversee the behavior of flows in the network. We propose a modified version of case-based reasoning, which uses the concept of imagination of situations. Unlike known methods, imaginative description of cases increases the reliability of decision-making. We provide a modification of the algorithm for dynamically building routing tables in distributed controllers of a transportation network. Analytic evaluation of the adaptation method's effectiveness is provided. The paper is concluded with outline of the implementation mechanism using a network of distributed controllers

  • 103.
    Belyakov, Stanislav Leonidovich
    et al.
    Southern Federal University, Department of Applied Information Science Taganrog.
    Savelyeva, Marina
    Southern Federal University, Department of Applied Information Science Taganrog.
    Yan, Jeffrey
    Department of Electrical and Computer System Engineering, University of Auckland, University of Auckland.
    Vyatkin, Valeriy
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Knowledge-based routing in mechanical transportation systems2014In: 12th IEEE International Conference on Industrial Informatics, INDIN 2014: Porto Alegre, Brazil, 27 - 30 July 2014, Piscataway, NJ: IEEE Communications Society, 2014, p. 48-53Conference paper (Refereed)
    Abstract [en]

    This paper presents the ways of constructing routing algorithms in mechanical transport systems based on knowledge. It is assumed that the experts observing system behavior applies his experience by designating subsystems with a specific behavior. To create routing tables, a model of fuzzy temporal hypergraph was used. We consider fixed and dynamic routing, given modifications of Dijkstra's algorithm for the case of fuzzy temporal hypergraphs

  • 104. Bengtsson, Daniel
    et al.
    Landström, Daniel
    Coding in a discrete multitone modulation system1996Student paper other, 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Discrete Multitone (DMT) modulation is a multicarrier technique which makes efficient use of the channel, maximizing the htroughput by sending different numbers of bits on different subchannels. The number of bits on each subchannel depends in the Signal-to-Noise Ratio of the subchannel. The performance of a DMT system can be further increased by using powerful coding techniques. This thesis investigates an implementation of coding for a DMT system. The coding techniques considered are Ree-Solomon coding combined with interleaving, and Trellis Coded Modulation. Wei's 4-dimensional 16-state coder combined with trellis shaping is the suggested trellis code. A single encoder is used which codes across the tones of each DMT-symbol. At a bit error probability of 10 -7 the suggested codes gain 3-6 dB over uncoded transmission. Hardware complexity and algorithmic aspects of coding are covered, as well as simulations to verify it.

  • 105.
    Bengtsson, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Algorithms for aggregate information extraction from sequences2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, we propose efficient algorithms for aggregate information extraction from sequences and multidimensional arrays. The algorithms proposed are applicable in several important areas, including large databases and DNA sequence segmentation. We first study the problem of efficiently computing, for a given range, the range-sum in a multidimensional array as well as computing the k maximum values, called the top-k values. We design two efficient data structures for these problems. For the range-sum problem, our structure supports fast update while preserving low complexity of range-sum query. The proposed top-k structure provides fast query computation in linear time proportional to the sum of the sizes of a two-dimensional query region. We also study the k maximum sum subsequences problem and develop several efficient algorithms. In this problem, the k subsegments of consecutive elements with largest sum are to be found. The segments can potentially overlap, which allows for a large number of possible candidate segments. Moreover, we design an optimal algorithm for ranking the k maximum sum subsequences. Our solution does not require the value of k to be known a priori. Furthermore, an optimal linear-time algorithm is developed for the maximum cover problem of finding k subsequences of consecutive elements of maximum total element sum.

  • 106.
    Bengtsson, Fredrik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Efficient aggregate queries on data cubes2004Licentiate thesis, monograph (Other academic)
    Abstract [en]

    As computers are developing rapidly and become more available to the modern information society, the possibility and ability to handle large data sets in database applications increases. The demand for efficient algorithmic solutions to process huge amounts of information increases as the data sets become larger. In this thesis, we study the efficient implementation of aggregate operations on the data cube, a modern and flexible model for data warehouses. In particular, the problem of computing the k largest sum subsequences of a given sequence is investigated. An efficient algorithm for the problem is developed. Our algorithm is optimal for large values of the user-specified parameter k. Moreover, a fast in-place algorithm with good trade-off between update- and query-time, for the multidimensional orthogonal range sum problem, is presented. The problem studied is to compute the sum of the data over an orthogonal range in a multidimensional data cube. Furthermore, a fast algorithmic solution to the problem of maintaining a data structure for computing the k largest values in a requested orthogonal range of the data cube is also proposed.

  • 107.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    A note on ranking k maximum sums2005Report (Other academic)
    Abstract [en]

    In this paper, we design a fast algorithm for ranking the k maximum sum subsequences. Given a sequence of real numbers and an integer parameter k, the problem is to compute k subsequences of consecutive elements with the sums of their elements being the largest, second largest, ..., and the k:th largest among all possible range sums. For any value of k, 1 <= k <= n(n+1)/2, our algorithm takes O(n + k log n) time in the worst case to rank all such subsequences. Our algorithm is optimal for k <= n.

  • 108.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Computing maximum-scoring segments in almost linear time2006Report (Other academic)
    Abstract [en]

    Given a sequence, the problem studied in this paper is to find a set of k disjoint continuous subsequences such that the total sum of all elements in the set is maximized. This problem arises naturally in the analysis of DNA sequences. The previous best known algorithm requires n log n time in the worst case. For a given sequence of length n, we present an almost linear-time algorithm for this problem. Our algorithm uses a disjoint-set data structure and requires O(n a(n, n) ) time in the worst case, where a(n,n) is the inverse Ackermann function.

  • 109.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Computing maximum-scoring segments in almost linear time2006In: Computing and Combinatorics: 12th annual international conference, COCOON 2006, Taipei, Taiwan, August 15 - 18, 2006 ; proceedings / [ed] Danny Z. Chen, Encyclopedia of Global Archaeology/Springer Verlag, 2006, p. 255-264Conference paper (Refereed)
    Abstract [en]

    Given a sequence, the problem studied in this paper is to find a set of k disjoint continuous subsequences such that the total sum of all elements in the set is maximized. This problem arises naturally in the analysis of DNA sequences. The previous best known algorithm requires Θ(n log n) time in the worst case. For a given sequence of length n, we present an almost linear-time algorithm for this problem. Our algorithm uses a disjoint-set data structure and requires O(nα(n, n)) time in the worst case, where α(n, n) is the inverse Ackermann function.

  • 110.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Computing maximum-scoring segments optimally2007Report (Other academic)
    Abstract [en]

    Given a sequence of length n, the problem studied in this report is to find a set of k disjoint subsequences of consecutive elements such that the total sum of all elements in the set is maximized. This problem arises in the analysis of DNA sequences. The previous best known algorithm requires time proportional to n times the inverse Ackermann function of (n,n), in the worst case. We present a linear-time algorithm, which is optimal, for this problem.

  • 111.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Computing the k maximum subarrays fast2004Report (Other academic)
    Abstract [en]

    We study the problem of computing the k maximum sum subarrays. Given an array of real numbers and an integer, k, the problem involves finding the k largest values of the sum from i to j of the array, for any i and j. The problem for fixed k=1, also known as the maximum sum subsequence problem, has received much attention in the literature and is linear-time solvable. In this paper, we develop an algorithm requiring time proportional to n times square root of k for an array of length n. Moreover, for two-dimensional version of the problem, which computes the k largest sums over all rectangular subregions of an m times n array of real numbers, we show that it can be solved efficiently in the worst case as well.

  • 112.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Efficient algorithms for k maximum sums2004In: Algorithms and Computation: 15th International Symposium, ISAAC 2004 / [ed] Rudolf Fleischer; Gerhard Trippen, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2004, p. 137-148Conference paper (Refereed)
    Abstract [en]

    We study the problem of computing the k maximum sum subsequences. Given a sequence of real numbers (x1,x2,⋯,xn) and an integer parameter k, l ≤ k ≤ 1/2n(n -1), the problem involves finding the k largest values of Σl=ij xl for 1 ≤ i ≤ j ≤ n. The problem for fixed k = 1, also known as the maximum sum subsequence problem, has received much attention in the literature and is linear-time solvable. Recently, Bae and Takaoka presented a θ(nk)-time algorithm for the k maximum sum subsequences problem. In this paper, we design efficient algorithms that solve the above problem in O (min{k + n log2 n, n √k}) time in the worst case. Our algorithm is optimal for k ≥ n log2 n and improves over the previously best known result for any value of the user-defined parameter k. Moreover, our results are also extended to the multi-dimensional versions of the k maximum sum subsequences problem; resulting in fast algorithms as well

  • 113.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Efficient algorithms for k maximum sums2006In: Algorithmica, ISSN 0178-4617, E-ISSN 1432-0541, Vol. 46, no 1, p. 27-41Article in journal (Refereed)
    Abstract [en]

    We study the problem of computing the k maximum sum subsequences. Given a sequence of real numbers {x1,x2,...,xn} and an integer parameter k, 1 ≤ k ≤ 1/2n(n-1),the problem involves finding the k largest values of ∑ℓ=ijxℓ for 1 ≤ i ≤ j ≤ n.The problem for fixed k = 1, also known as the maximum sum subsequence problem, has received much attention in the literature and is linear-time solvable. Recently, Bae and Takaoka presented a Θ(nk)-time algorithm for the k maximum sum subsequences problem. In this paper we design an efficient algorithm that solves the above problem in O(min {k+nlog2n,n√k} ) time in the worst case. Our algorithm is optimal for k = Ω(n log 2 n) and improves over the previously best known result for any value of the user-defined parameter k < 1. Moreover, our results are also extended to the multi-dimensional versions of the k maximum sum subsequences problem; resulting in fast algorithms as well

  • 114.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Ranking k maximum sums2007In: Theoretical Computer Science, ISSN 0304-3975, E-ISSN 1879-2294, Vol. 377, no 1-3, p. 229-237Article in journal (Refereed)
    Abstract [en]

    Given a sequence of n real numbers and an integer parameter k, the problem studied in this paper is to compute k subsequences of consecutive elements with the sums of their elements being the largest, the second largest, and the kth largest among all possible range sums of the input sequence. For any value of k, 1 <= k <= n (n + 1)/2, we design a fast algorithm that takes O (n + k log n) time in the worst case to compute and rank all such subsequences. We also prove that our algorithm is optimal for k = O (n) by providing a matching lower bound.Moreover, our algorithm is an improvement over the previous results on the maximum sum subsequences problem (where only the subsequences are requested and no ordering with respect to their relative sums will be determined).Furthermore, given the fact that we have computed the fth largest sums, our algorithm retrieves the (l + 1)th largest sum in O (log n) time, after O (n) time of preprocessing.

  • 115.
    Bengtsson, Fredrik
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Chen, Jingsen
    Space-efficient range-sum queries in OLAP2004In: Data Warehousing and Knowledge Discovery. Proceedings: 6th international conference, DaWaK 2004, Zaragoza, Spain, September 1 - 3, 2004 : proceedings / [ed] Yahiko Kambayashi; Mukesh Mohania; Wolfram Wöß, Encyclopedia of Global Archaeology/Springer Verlag, 2004, p. 87-96Conference paper (Refereed)
    Abstract [en]

    In this paper, we present a fast algorithm to answer range-sum queries in OLAP data cubes. Our algorithm supports constant-time queries while maintaining sub-linear time update and using minimum space. Furthermore, we study the trade-off between query time and update time. The complexity for query is O(2ℓd) and for updates O((2ℓ2ℓ√n)d) on a data cube of nd elements, where ℓ is a trade-off parameter. Our algorithm improve over previous best known results

  • 116. Bengtsson, Johan
    et al.
    Andersson, Karl
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Parnes, Peter
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Nyström, Jimmy
    Nyström, Nicklas
    Project: COnnected Media and Presence from European Institute of Technology2014Other (Other (popular science, discussion, etc.))
  • 117.
    Benko, I.
    et al.
    University of Waterloo.
    Brodnik, Andrej
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Architecture of KRPAN1996In: Elektrotehniski Vestnik, ISSN 0013-5852, Vol. 63, no 2, p. 65-68Article in journal (Refereed)
    Abstract [en]

    In the paper we address the operation of an agency that provides information in a newspaper-like form on the information highway. We describe the software architecture and the physical layout of KRPAN, a kernel that provides the support necessary to operate such an agency. KRPAN is a distributed system which employs intelligent caching to improve space and network utilization. The implementation of KRPAN relies on standardized formats of data which permits usage of commonly available tools. At the end we touch legal and ethical questions and describe how KRPAN helps to solve them.

  • 118.
    Bera, Samaresh
    et al.
    Computer Science and Engineering Department, Indian Institute of Technology, Kharagpur, 721302, India..
    Misra, Sudip
    Computer Science and Engineering Department, Indian Institute of Technology, Kharagpur, 721302, India..
    Vasilakos, Athanasios
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Software-Defined Networking for Internet of Things: a Survey2017In: IEEE Internet of Things Journal, ISSN 2327-4662, Vol. 4, no 6, p. 1994-2008Article in journal (Refereed)
    Abstract [en]

    Internet of things (IoT) facilitates billions of devices to be enabled with network connectivity to collect and exchange real-time information for providing intelligent services. Thus, IoT allows connected devices to be controlled and accessed remotely in the presence of adequate network infrastructure. Unfortunately, traditional network technologies such as enterprise networks and classic timeout-based transport protocols are not capable of handling such requirements of IoT in an efficient, scalable, seamless, and cost-effective manner. Besides, the advent of software-defined networking (SDN) introduces features that allow the network operators and users to control and access the network devices remotely, while leveraging the global view of the network. In this respect, we provide a comprehensive survey of different SDN-based technologies, which are useful to fulfill the requirements of IoT, from different networking aspects – edge, access, core, and data center networking. In these areas, the utility of SDN-based technologies is discussed, while presenting different challenges and requirements of the same in the context of IoT applications. We present a synthesized overview of the current state of IoT development. We also highlight some of the future research directions and open research issues based on the limitations of the existing SDN-based technologies.

  • 119.
    Berg, Louise
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Lindh, Rebecca
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Kommunikation med hjälp av sociala nätverkssidor: En kvalitativ studie om nyblivna pensionärers uppfattning av social närvaro på sociala nätverkssidor2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Behovet av kommunikation har alltid varit en viktig del av människans sociala liv. Den tekniska utvecklingen har möjliggjort nya kommunikationsvägar och sättet att kommunicera har därför förändrats. Syftet med studien är att kartlägga hur yngre pensionärer upplever social närvaro och tillhörighet på sociala nätverkssidor. Målsättningen med studien är att identifiera hur tekniken upplevs möjliggöra eller begränsa graden av social närvaro för yngre pensionärer vid kommunikation över sociala nätverkssidor. 

    Studien tillämpade en kvalitativ metod där semistrukturerade intervjuer användes för att samla in data. Intervjuerna transkriberades enskilt för att i en helhetsanalys tolkas och bilda en samlad bild över det empiriska materialet. Urvalet bestod av yngre pensionärer mellan 66–75 år som använder sociala nätverkssidor. Totalt deltog åtta respondenter. 

    Den insamlade empirin visar att samtliga respondenter är aktiva användare av Facebook men orsakerna till användningen samt vilken typ av aktiviteter som utförs skiljer sig mellan deltagarna. Samtliga respondenter uppger att de använder sociala nätverkssidor för att följa och ta del av familjens- och vännernas liv samt som informationskälla. Respondenternas upplevelse är att sociala nätverkssidor utgör ett komplement till annan kommunikation där den sociala närvaron är lägre på sociala nätverkssidor jämfört med fysiska möten eller telefonsamtal. Empirin visar också att sociala nätverkssidor för yngre pensionärer ger en lägre grad av social närvaro och tillhörighetskänsla än annan kommunikation i textform som SMS eller e-post. Den generella bild som respondenterna uppvisar är att sociala nätverkssidor möjliggör för snabb och flexibel kommunikation men där den lägre graden av social närvaro utgör en begränsning som gör att sociala nätverkssidor inte kan likställas vid fysiska möten. 

    Slutsatsen är att sociala nätverkssidor upplevs ha en lägre grad av social närvaro än annan kommunikation vilket empirin uppvisar med stöd av den teoretiska referensramen. Tekniken som komplement till annan kommunikation erbjuder en upplevelse av tillhörighet och gemenskap och skapar möjligheter för yngre pensionärer att vara sociala. Tekniken som ersättning för alternativ kommunikation skapar istället en begränsning i vad sociala nätverkssidor kan erbjuda för upplevelsen av social närvaro.

  • 120.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Brodnik, Andrej
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Mrozek, Kent
    Staffansson, Mats
    Luleå tekniska universitet.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Minimum curvature variation B-splines: validation of a path-planning model2004Report (Other academic)
  • 121.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Brodnik, Andrej
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science. University of Primorska, Slovenia. .
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Staffansson, Mats
    Luleå tekniska universitet.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Planning smooth and obstacle-avoiding b-spline paths for autonomous mining vehicles2010In: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, Vol. 7, no 1, p. 167-172Article in journal (Refereed)
    Abstract [en]

    We study the problem of automatic generation of smooth and obstacle-avoiding planar paths for efficient guidance of autonomous mining vehicles. Fast traversal of a path is of special interest. We consider four-wheel four-gear articulated vehicles and assume that we have an a priori knowledge of the mine wall environment in the form of polygonal chains. Computing quartic uniform B-spline curves, minimizing curvature variation, staying at least at a proposed safety margin distance from the mine walls, we plan high speed paths.

  • 122.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Erikson, Ulf
    Luleå tekniska universitet.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Mrozek, Kent
    Navigator AB.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Automatic generation of smooth paths bounded by polygonal chains2001In: CIMCA 2001: 2001 international conference on computational intelligence for modelling, control & automation : 9-11 July 2001, Las Vegas, Nevada, USA : proceedings / [ed] M. Mohammadian, CIMCA , 2001, p. 528-535Conference paper (Refereed)
  • 123.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Greppe, Anders
    Thorén, Johan
    Papp, John
    Curve and surface fitting to measured data with a B-spline approach1999Report (Other academic)
    Abstract [en]

    Report in the Project course in Mathematics, MAM088, 1998/1999. Department of Mathematics, Luleå University of Technology, Sweden

  • 124. Berglund, Tomas
    et al.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    An obstacle-avoiding minimum variation B-spline problem2003In: Proceedings: 2003 International Conference on Geometric Modeling and Graphics, GMAG 2003 ; 16 - 18 July 2003, London, England, Los Alamitos, Calif: IEEE Communications Society, 2003, p. 156-161Conference paper (Refereed)
    Abstract [en]

    We study the problem of computing a planar curve, restricted to lie between two given polygonal chains, such that the integral of the square of arc-length derivative of curvature along the curve is minimized. We introduce the minimum variation B-spline problem, which is a linearly constrained optimization problem over curves, defined by B-spline functions only. An empirical investigation indicates that this problem has one unique solution among all uniform quartic B-spline functions. Furthermore, we prove that, for any B-spline function, the convexity properties of the problem are preserved subject to a scaling and translation of the knot sequence defining the B-spline.

  • 125.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    The problem of computing an obstacle-avoiding minimum variation B-spline2003Report (Other academic)
    Abstract [en]

    We study the problem of computing a planar curve restricted to lie between two given polygonal chains such that the integral of the square of arc- length derivative of curvature along the curve is minimized. We introduce the Minimum Variation B-spline problem which is a linearly constrained optimization problem over curves defined by B-spline functions only. An empirical investigation indicates that this problem has one unique solution among all uniform quartic B-spline functions. Furthermore, we prove that, for any B-spline function, the convexity properties of the problem are preserved subject to a scaling and translation of the knot sequence defining the B-spline.

  • 126.
    Berglund, Tomas
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Strömberg, Thomas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Jonsson, Håkan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Söderkvist, Inge
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Epi-convergence of minimum curvature variation B-splines2003Report (Other academic)
    Abstract [en]

    We study the curvature variation functional, i.e., the integral over the square of arc-length derivative of curvature, along a planar curve. With no other constraints than prescribed position, slope angle, and curvature at the endpoints of the curve, the minimizer of this functional is known as a cubic spiral. It remains a challenge to effectively compute minimizers or approximations to minimizers of this functional subject to additional constraints such as, for example, for the curve to avoid obstacles such as other curves. In this paper, we consider the set of smooth curves that can be written as graphs of three times continuously differentiable functions on an interval, and, in particular, we consider approximations using quartic uniform B- spline functions. We show that if quartic uniform B-spline minimizers of the curvature variation functional converge to a curve, as the number of B-spline basis functions tends to infinity, then this curve is in fact a minimizer of the curvature variation functional. In order to illustrate this result, we present an example of sequences of B-spline minimizers that converge to a cubic spiral.

  • 127.
    Bergvall-Kåreborn, Birgitta
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Broberg, Anders
    Umeå universitet.
    Lassinantti, Josefin
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Davoli, Lorenzo
    Umeå universitet.
    Kuenen, Stoffel
    Umeå universitet.
    Palmquist, Lena
    Umeå universitet.
    Parnes, Peter
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Ståhlbröst, Anna
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Innovation and Design.
    Synnes, Kåre
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Wennberg, Paula
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Distance- Spanning Technology.
    User toolkits for citizen-centric mobild service innovation2012In: eChallenges e-2012 Conference Proceedings / [ed] Paul Cunningham; Miriam Cunningham, IIMC International Information Management Corporation , 2012Conference paper (Refereed)
    Abstract [en]

    Around the world, there is an ongoing shift from en economy focusing on product development to an economy with focus on digital service development. An ongoing initiative in Europe to support this shift is the Internet of Services (IoS) which strives for a situation where everything that is needed to use a software is available as a service. The aim of this paper is to present a toolkit that non-programmers can use develop their own innovative mobile services. This environment strives to put forth a situation where technologies are made available as components that easily can be composed into a mobile services by just about anyone. This has tremendous impact on the feasibility of citizen-centric services where citizens create apps based on their current needs in their contemporary situation.

  • 128.
    Berhane, Welderufael Tesfay
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science. Luleå University of Technology.
    Aleksy, Markus
    ABB Corporate Research.
    Andersson, Karl
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science. Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Distance- Spanning Technology.
    Lehtola, Marko
    ABB Corporate Research.
    Mobile computing application for industrial field service engineering: a case for ABB service engineers2013In: Proceedings of the 38th IEEE Conference on Local Computer Networks Workshops (LCN Workshops): 7th IEEE Workshop On User MObility and VEhicular Networks / [ed] Damla Turgut; Nils Aschenbruck; Jens Tölle, Piscataway, NJ: IEEE Computer Society Press , 2013, p. 188-193Conference paper (Refereed)
    Abstract [en]

    The increasing digitalization of our daily lives is gaining a new momentum recently in what is called the post- desktop era of computing. This wide spread in digitalization is made possible by the introduction of handy devices specifically of mobile phones, laptop computers, smartphones, and tablets. This new trend in shaping up technological advancement presents new opportunities for mobile information presentation, processing, and synthesis in different spheres of application such as providing industrial field services engineering support. Industrial field service engineers execute sets of work orders on daily basis plans. These work order executions demand the availability of digital information anywhere anytime to process them faster. This paper presents a scenario where the newly emerging Smartphone features such as augmented reality, audio/video processing, and near field communication sensing can be used to develop a prototype that supports industrial field service engineers in the contemporary field service engineering taskforces. It employs real world use-cases and carrying out quantitative prototype usability test analysis.

  • 129.
    Bezerra, Nibia Souza
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Ferreira Maciel, Tarcisio
    Federal University of Ceará.
    M. Lima, Francisco Rafael
    Federal University of Ceará.
    Sousa Jr., Vicente A.
    Federal University of Rio Grande do Norte.
    Interference Aware Resource Allocation with QoS Guarantees in OFDMA/SC-FDMA2018In: Journal of Communication and Information Systems, ISSN 1980-6604, Vol. 33, no 1, p. 124-128Article in journal (Refereed)
    Abstract [en]

    Efficient Radio Resource Allocation (RRA) is of utmost importance for achieving maximum capacity in mobile networks. However, the performance assessment should take into account the main constraints of these networks. This letter presents important enhancements to RRA algorithms proposed in [1]. Prior work [1] ignores some important system constraints such as the impact of inter-cell interference and granularity of frequency allocation blocks. Here we show the performance degradation when these system constraints are assumed on the algorithms in [1] as well as propose some improvements on these algorithms in order to achieve better performance.

  • 130.
    Bezerra, Nibia Souza
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Wang, Min
    Network Architecture and Protocols Research, Ericsson .
    Åhlund, Christer
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Nordberg, Mats
    Network Architecture and Protocols Research, Ericsson .
    Schelén, Olov
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    RACH performance in massive machine-type communications access scenario2018Conference paper (Refereed)
    Abstract [en]

    With the increasing number of devices performing Machine-Type Communications (MTC), mobile networks are expected to encounter a high load of burst transmissions. One bottleneck in such cases is the Random Access Channel (RACH) procedure, which is responsible for the attachment of devices, among other things. In this paper, we performed a rich-parameter based simulation on RACH to identify the procedure bottlenecks. A finding from the studied scenarios is that the Physical Downlink Control Channel (PDCCH) capacity for the grant allocation is the main limitation for the RACH capacity rather than the number of Physical Random Access Channel (PRACH) preambles. Guided by our simulation results, we proposed improvements to the RACH procedure and to PDCCH.

  • 131.
    Bilal, Mohd
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    A Heuristic Search Algorithm for Asteroid Tour Missions2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Since the discovery of Ceres, asteroids have been of immense scientific interest and intrigue. They hold answers to many of the fundamental questionsabout the formation and evolution of the Solar System. Therefore, a missionsurveying the asteroid belt with close encounter of carefully chosen asteroidswould be of immense scientific benefit. The trajectory of such an asteroidtour mission needs to be designed such that asteroids of a wide range ofcompositions and sizes are encountered; all with an extremely limited ∆Vbudget.This thesis presents a novel heuristic algorithm to optimize trajectoriesfor an asteroid tour mission with close range flybys (≤ 1000 km). The coresearch algorithm efficiently decouples combinatorial (i.e. choosing the asteroids to flyby)and continuous optimization (i.e. optimizing critical maneuversand events) of what is essentially a mixed integer programming problem.Additionally, different methods to generate a healthy initial population forthe combinatorial optimization are presented.The algorithm is used to generate a set of 1800 feasible trajectories withina 2029+ launch frame. A statistical analysis of these set of trajectories isperformed and important metrics for the search are set based on the statistics.Trajectories allowing flybys to prominent families of asteroids like Flora andNysa with ∆V as low as 4.99 km/s are obtained.Two modified implementations of the algorithm are presented. In a firstiteration, a large sample of trajectories is generated with a limited numberof encounters to the most scientifically interesting targets. While, a posteriori, trajectories are filled in with as many small targets as possible. Thisis achieved in two different ways, namely single step extension and multiplestep extension. The former fills in the trajectories with small targets in onestep, while the latter optimizes the trajectory by filling in with one asteroid per step. The thesis also presents detection of asteroids for successfullyperforming flybys. A photometric filter is developed which prunes out badlyilluminated asteroids. The best trajectory is found to perform well againstthis filter such that nine out of the ten planned flybys are feasible.

  • 132.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Eliasson, Jens
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Lindgren, Per
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Osipov, Evgeny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Riliskis, Laurynas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Road surface networks technology enablers for enhanced ITS2010In: 2010 IEEE Vehicular Networking Conference, VNC 2010: Jersey City, NJ ; 13-15 Dec 2010, Piscataway, NJ: IEEE Communications Society, 2010, p. 152-159Conference paper (Refereed)
    Abstract [en]

    The increased need for mobility has led to transportation problems like congestion, accidents and pollution. In order to provide safe and efficient transport systems great efforts are currently being put into developing Intelligent Transport Systems (ITS) and cooperative systems. In this paper we extend proposed solutions with autonomous on-road sensors and actuators forming a wireless Road Surface Network (RSN). We present the RSN architecture and design methodology and demonstrate its applicability to queue-end detection. For the use case we discuss the requirements and technological solutions to sensor technology, data processing and communication. In particular the MAC protocol is detailed and its performance assessed through theoretical verification. The RSN architecture is shown to offer a scalable solution, where increased node density offers more precise sensing as well as increased redundancy for safety critical applications. The use-case demonstrates that RSN solutions may be deployed as standalone systems potentially integrated into current and future ITS. RSN may provide both easily deployable and cost effective alternatives to traditional ITS (with a direct impact independent of penetration rate of other ITS infrastructures - i.e., smart vehicles, safe spots etc.) as well as provide fine grain sensory information directly from the road surface to back-end and cooperative systems, thus enabling a wide range of ITS applications beyond current state of the art.

  • 133.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Osipov, Evgeny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    On the design of cooperative road infrastructure systems2008In: Reglermöte 2008: proceedings / [ed] Thomas Gustafsson; Wolfgang Birk; Andreas Johansson, Luleå: Luleå tekniska universitet, 2008Conference paper (Other academic)
    Abstract [en]

    This paper discusses the design of cooperative road infrastructure systems for infrastructure-based driving support functions. The background of such systems is mapped out and it is shown that there is a need for a cross disciplinary approach. Using an example of a support function, namely the overtaking support, it is shown that such a system is feasible. The different challenges and technological problems that are identified are given and the future work is indicated.

  • 134.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Osipov, Evgeny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Eliasson, Jens
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    iRoad - cooperative road infrastructure systems for driver support2009In: 16th World Congress and Exhibition on Intelligent Transport Systems 2009: 16th ITS World Congress ; Stockholm, Sweden, 21 - 25 September 2009, Red Hook: Curran Associates, Inc., 2009Conference paper (Refereed)
    Abstract [en]

    This paper discusses the design and implementation of a cooperative road infrastructure systems, which uses an intelligent road surface. Using an overtaking assist feature as an example it is shown how such a feature can be designed and implemented on a road infrastructure and integrated with drivers and passengers using IMS. The feasibility of this feature is assessed from a functional and communication perspective. Moreover, first results from real-life tests on the Swedish highway E4 are presented which motivate the next research and development steps.

  • 135.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Osipov, Evgeny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Riliskis, Laurynas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Hesler, Alban
    NEC.
    Modular design and performance ranking of communication protocols2009Report (Other academic)
    Abstract [en]

    In this deliverable we present a systematic approach towards designing modularized protocols and rank a contribution of their components to the overall system performance. In the nutshell, this approach is based onthree steps: 1.) identifying adjustable parameters in existing protocols, 2.) ranking their influence on the system-level performance metrics and 3.) defining protocol modules exposing the parameters of the highest rank. To this end we present the definition of the components for constructing MAC protocols based on ranking of the impact of adjustable parameters on the overall system performance. We also overview a ranking method for functional blocks of protocols on the routing layer.

  • 136.
    Bitar, Hadi
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Jakobsson, Björn
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    GDPR: Securing Personal Data in Compliance with new EU-Regulations2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    New privacy regulations bring new challenges to organizations that are handling and processing personal data regarding persons within the EU. These challenges come mainly in the form of policies and procedures but also with some opportunities to use technology often used in other sectors to solve problems. In this thesis, we look at the new General Data Protection Regulation (GDPR) in the EU that comes into full effect in May of 2018, we analyze what some of the requirements of the regulation means for the industry of processing personal data, and we look at the possible solution of using hardware security modules (HSMs) to reach compliance with the regulation. We also conduct an empirical study using the Delphi method to ask security professionals what they think the most important aspects of securing personal data, and put that data in relation to the identified compliance requirements of the GDPR to see what organizations should focus on in their quest for compliance with the new regulation. We found that a successful implementation of HSMs based on industry standards and best practices address four of the 35 identified GDPR compliance requirements, mainly the aspects concerning compliance with anonymization through encryption, and access control. We also deduced that the most important aspect of securing personal data according to the experts of the Delphi study is access control followed by data inventory and classification. 

  • 137. Bittencourt, Roberto Almeida
    et al.
    Carr, David
    Luleå tekniska universitet.
    A method for asynchronous web-based lecture delivery2001In: Impact on engineering and science education: conference proceedings / FIE 2001, 31st Annual Frontiers in Education Conference, IEEE Communications Society, 2001Conference paper (Refereed)
    Abstract [en]

    Computer-based distance education has been growing enormously in recent years due to advances in key technologies: telecommunications, computer technology, graphical user interfaces, and the Internet. Distance education materials can be presented either synchronously, creating the illusion of a classroom on the computer, or asynchronously, allowing the students access-on-demand. We describe the development of a system to solve part of the asynchronous education problem - delivery of pre-recorded multimedia lectures via a web browser. We built a demonstration system using off-the-shelf technology making it possible to make presentations using commercial tools and to display them on standard systems. We designed the system with lectures composed of "slides" accompanied by audio commentary. These presentations can be delivered via lowspeed modem links - an important consideration in places without a well-developed infrastructure. We also believe that computer-based education is often so complicated to use that operation interferes with education. In order to avoid this, we evaluated a prototype system to obtain feedback about difficulties in operation and to correct them.

  • 138.
    Björk, Hanna
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Johnsson, Gustav
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Navigation i komplexa miljöer med hjälp av digitala tjänster och IoT2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Research and implementation of use when it comes to outdoor navigation and GPS systems have come quite far compared to their indoor alternatives. Pedestrian friendly wayfinding solutions for indoor use are still lagging behind, and even more so when it comes to recommendations on implementation of best practice.

    One of our goals during the research process was aimed at finding the most adequate ways of conveying wayfinding solutions to end-users in different situations. In order to perform this task, we used a benchmarking process on a selection of wayfinding alternatives. The goal of this process have been focused on finding out which solutions are available at this moment, what they offer the users in terms of wayfinding support, and where issues might arise based on cognitive user theory, wayfinding best practice and technological limitations concerning mobile devices or different digital platforms.

    During our research we found that there are several different solutions that are available for implementation, but that they all come with their own specific strengths and limitations on both the technological side and for the end-users concerning usability.

    The result of our research has been a collection of qualitative data, and recommendations concerning digital and user limitations connected to our specific case. However, the result of this research should not be limited to our case alone, but rather as a reference point for organizations or developers that wish to implement indoor solutions for users, or for future research within the area of indoor navigation and wayfinding.

  • 139.
    Björklund, Thomas
    et al.
    Luleå tekniska universitet.
    Brodnik, Andrej
    Nordlander, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Formal verification of a trie-based data structure2005Conference paper (Refereed)
  • 140.
    Björkman, Anna
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Nyttan med Internet of Things i Offentliga Verksamheter: Att identifiera nyttor, fördelar och utmaningar2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Internet of Things (IoT) är ett hett ämne i dagens samhälle då inte bara saker utan även människor kan kopplas upp mot nätet. För verksamheter ses stora fördelar med att använda sig av tekniken i syfte att ligga i framkant och bli effektivare i sina arbetsprocesser. Denna studie fördjupar sig i vilka identifierade nyttor, fördelar och utmaningar som finns samt om det verkligen finns behov av Internet of Things i verksamheter.

    Studien utgår ifrån en av Region Skånes förvaltningar, Regionservice, som befinner sig på en omfattande digitaliseringsresa av att implementera en ny systemlösning. De intervjuer som gjorts med anställda inom förvaltningen har varit i huvudsakligt syfte att skapa en förståelse för hur den nya systemlösningen kommer att fungera samt deras tankar om att använda Internet of Things. Tillsammans med studiens teori, som fokuserat på nyttor, fördelar och utmaningar med IoT, avslutas studien med en slutsats som är grundad i teorin och den empiriska undersökningen på Regionservice. I slutsatsen presenteras egna åsikter och tankar om hur IoT kommer att bidra med något behov och nytta inom verksamheterna samt vilken påverkan och utmaningar som kan uppstå.

  • 141.
    Bladh, Thomas
    et al.
    Luleå tekniska universitet.
    Carr, David A
    Luleå tekniska universitet.
    Kljun, Matjaz
    University of Primorska.
    The effect of animated transitions on user navigation in 3D tree-maps2005In: Proceedings: Ninth International Conference on Information Visualisation : 06 - 08 July 2005, London, England / [ed] Ebad Banissi, Los Alamitos, Calif: IEEE Communications Society, 2005, p. 297-305Conference paper (Refereed)
    Abstract [en]

    This paper describes a user study conducted to evaluate the use of smooth animated transitions between directories in a three-dimensional, tree-map visualization. We looked specifically at the task of returning to a previously visited directory after either an animated or instantaneous return to the root location. The results of the study show that animation is a double-edged sword. Even though users take more shortcuts, they also make more severe navigational errors. It seems as though the promise of a more direct route to the target directory, which animation provides, somehow precludes users who navigate incorrectly from applying a successful recovery strategy.

  • 142.
    Bladh, Thomas
    et al.
    Luleå tekniska universitet.
    Carr, David
    Luleå tekniska universitet.
    Scholl, Jeremiah
    Extending tree-maps to three dimensions: a comparative study2004In: Computer Human Interaction: 6th Asia Pacific Conference, APCHI 2004, Rotorua, New Zealand, June 29-July 2, 2004. Proceedings / [ed] M. Masoodian; S. Jones; B. Rogers, Encyclopedia of Global Archaeology/Springer Verlag, 2004, p. 50-59Conference paper (Refereed)
    Abstract [en]

    This paper presents StepTree, an information visualization tool designed for depicting hierarchies, such as directory structures. StepTree is similar to the hierarchy-visualization tool, Treemap, in that it uses a rectangular, space-filling methodology, but differs from Treemap in that it employs three-dimensional space, which is used to more clearly convey the structural relationships of the hierarchy. The paper includes an empirical study comparing typical search and analysis tasks using StepTree and Treemap. The study shows that users perform significantly better on tasks related to interpreting structural relationships when using StepTree. In addition, users achieved the same performance with StepTree and Treemap when doing a range of other common interpretative and navigational tasks.

  • 143.
    Bladh, Thomas
    et al.
    Luleå tekniska universitet.
    Carr, David
    Luleå tekniska universitet.
    Scholl, Jeremiah
    Extending tree-maps to three dimensions: a comparative study2004Report (Other academic)
    Abstract [en]

    This paper presents StepTree, an information visualization tool designed for depicting hierarchies, such as directory structures. StepTree is similar to the hierarchy-visualization tool, Treemap, in that it uses a rectangular, space-filling methodology, but differs from Treemap in that it employs threedimensional space, which is used to more clearly convey the structural relationships of the hierarchy. The paper includes an empirical study comparing typical search and analysis tasks using StepTree and Treemap. The study shows that users perform significantly better on tasks related to interpreting structural relationships when using StepTree. In addition, users achieved the same performance with StepTree and Treemap when doing a range of other common interpretative and navigational tasks.

  • 144.
    Blech, Jan Olaf
    et al.
    RMIT University, Melbourne.
    Lindgren, Per
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Pereira, David
    ISEP, Instituto Superior de Engenharia do Porto.
    Vyatkin, Valeriy
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Zoitl, Alois
    fortiss GmbH, Munich.
    A Comparison of Formal Verification Approaches for IEC 614992016In: 2016 IEEE 21st International Conference on Emerging Technologies and Factory Automation (ETFA): Berlin, 6-9 Sept. 2016, Piscataway, NJ: IEEE conference proceedings, 2016, article id 7733636Conference paper (Refereed)
    Abstract [en]

    Engineering and computer science have come up with a variety of techniques to increase the confidence in systems, increase reliability, facilitate certification, improve reuse and maintainability, improve interoperability and portability. Among them are various techniques based on formal models to enhance testing, validation and verification. In this paper, we are concentrating on formal verification both at runtime and design time of a system. Formal verification of a system property at design time is the process of mathematically proving that the property indeed holds. At runtime, one can check the validity of the property and report deviations by monitoring the system execution. Formal verification relies on semantic models, descriptions of the system and its properties. We report on ongoing verification work and present two different approaches for formal verification of IEC 61499-based programs. We provide two examples of ongoing work to exemplify the design and the runtime verification approaches

  • 145.
    Bodin, Ulf
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Quality issues in Internet packet forwarding2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis addresses quality issues in Internet Protocol (IP) packet forwarding. In IP networks, queue mechanisms and scheduling can be used to construct multiple forwarding behaviors. Thereby, both relative and independent services can be offered to Internet users. Independent services offer forwarding qualities known beforehand. Users are assumed to explicitly request admission to an independent service from their network provider. With relative services, users switch between these services to find one that provides an appealing balance between forwarding quality and cost. The thesis makes contributions to three research areas related to forwarding quality in IP networks; differentiating forwarding mechanisms, admission control for differentiated services, and forwarding quality in radio networks carrying Internet traffic. It contributes to the first research area with definitions of three recommendations related to offering loss-rate differentiation (i.e., multiple drop precedence levels). These recommendations are; (1) the total forwarding quality at congested links should not be degraded due to actions taken to create loss-rate differentiation, (2) traffic at high drop precedence levels should always be given a useful share of available forwarding resources, and (3) users should be able to predict the change in loss-rates when switching between drop precedence levels. We specify and evaluate properties of queue mechanisms following these recommendations. Also, as a contribution to the first research area, a new set of forwarding behaviors is specified and analyzed. These forwarding behaviors are suitable for rate-adaptive and delay-sensitive applications with limited loss-tolerance. Applications needing loss-free forwarding of specific packets can be said to have limited loss tolerance. We define and evaluate a scheduling mechanism creating these forwarding behaviors that can be implemented efficiently. The contribution to the second research area is a mechanism for admission control giving assurances on loss-rates to rate varying applications is defined. With this mechanism, dynamic per-link admission thresholds are used to limit committed aggregate rates. To allow for high link utilization through statistical multiplexing we specify a method to adjust these thresholds using low impact traffic monitoring mechanisms commonly available in legacy routers. In radio networks carrying IP traffic, radio transmissions can be scheduled differently to balance spectrum utilization and the forwarding quality provided. Also, parameters settings can be used to optimize the forwarding quality in radio networks for certain transport protocols and applications. This thesis analyses delay spikes experienced by IP traffic in cellular radio networks. We evaluate two different radio-block scheduling mechanisms’ impact on two versions of the Transmission Control Protocol (TCP) (i.e., TCP Sack and TCP Eifel). The evaluation contributes to the third research area by revealing basic dependencies between scheduling, interference, and congestion control mechanisms implemented by TCP. Finally, the thesis contributes to the third research area by proposing extensions to the Internet architecture for inter-layer communication. These extensions allow applications and transport protocols to exchange information with radio link layers. Such information exchange can be used to improve the forwarding quality and to customize data and transport features for current radio conditions.

  • 146.
    Bodin, Ulf
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Queue mechanisms for differentiation in the Internet2000Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis addresses loss-rate differentiation in the Internet. Loss-rate differentiation can be offered by tagging packets with different levels of drop precedence. Multiple drop precedence levels can be used to provide relative service levels and to assure forwarding capacity in the Internet. Assured services offer forwarding qualities known beforehand. This makes them more predictable than relative services. Users are assumed to explicitly request an assured service from their network provider for traffic up to a specified rate. With relative service levels, users switch between these levels to find one that provides an appealing balance between forwarding quality and cost. The policy for drop precedence probabilities defines the type of loss-rate differentiation pro-vided. Sheltered loss-rate (SLR) differentiation is offered by strictly giving drops to traffic at high drop precedence levels. Sheltering means that traffic at a low drop precedence level is protected from losses caused by traffic at higher levels. Such protection is required for assured services. Relative loss-rate (RLR) differentiation is offered when drop precedence probabilities are rela-tively distributed between drop precedence levels. Offering fixed relations in these probabilities further refines RLR differentiation, resulting in proportional loss-rate (PLR) differentiation. This thesis defines three recommendations associated with providing loss-rate differentiation. Such differentiation can be created with queue mechanisms. We specify and evaluate the proper-ties of differentiating queue mechanisms that make them capable of meeting the recommenda-tions defined. These evaluations are made with simulations. Firstly, the total forwarding quality at congested links should not be degraded due to actions taken to create loss-rate differentiation. The total forwarding quality includes packet loss patterns and delay variations. These quality metrics are high when packet drops are delayed. When pro-viding loss-rate differentiation, drops can be delayed through only dropping packets as they ar-rive. Dropping packets from queues enables immediate drops. This thesis shows that with imme-diate drops less bursty loss patterns and lower delay variations are achieved than with delayed drops. Secondly, traffic at high drop precedence levels should always be given a useful share of avail-able forwarding resources. Such traffic may experience high loss-rates, but should not become starved. Traffic at high levels may become starved due to overloading of traffic at lower levels when creating SLR differentiation. Starvation can be avoided with proper control of low drop precedence traffic. This control may, however, fail due to changes in the network routing topol-ogy, inaccurate admission control, etc. To avoid starvation without relying on proper traffic con-trol, this thesis presents a new queuing mechanism that falls back from offering sheltering to providing RLR differentiation during overloading of low drop precedence traffic. Thirdly, PLR differentiation should be predictable. Users should be able to predict the change in loss-rates when switching between drop precedence levels. PLR differentiation requires relations in loss-rates to be fixed to pre-configured target ratios. Running estimates of loss-rate ratios can be used as feedback to adjust towards these targets if the actual loss-rate ratios deviate from the target ratios. To provide predictable PLR differentiation, these estimates need to be accurate and stable at varying traffic loads. Moreover, they need to detect traffic load variations rapidly. This thesis presents a loss-rate estimator that provides accurate, stable and rapid detection of loss-rate ratios at varying traffic loads.

  • 147.
    Bodin, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Andersson, Ulf
    Dadhich, Siddharth
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Uhlin, Erik
    Volvo Construction Equipment.
    Marklund, Ulf
    Boliden AB.
    Häggström, Derny
    Oryx Simulations AB.
    Remote Controlled Short-Cycle Loading of Bulk Material in Mining Applications2015Article in journal (Refereed)
    Abstract [en]

    High-capacity wireless IP networks with limited delays are nowadays being deployed in both underground and open-pit mines. This allows for advanced remote control of mining machinery with improved feedback to operators and extensive monitoring of machine status, wear and fatigue. Wireless connectivity varies however depending on channel impairments caused by obstacles, multi-path fading and other radio issues. Therefore remote control and monitoring should be capable of adapting their sending rates to handle variations in communications quality. This paper presents key challenges in advanced remote control and monitoring of working machines via high-capacity wireless IP networks in mining environments. We reason about these challenges in context of underground short-cycle load, haul and dump operation with large-volume built wheel-loaders and present a generic communication solution for an operator assistance concept capable of adapting to varying communication properties

  • 148.
    Bodin, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Jonsson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Schelén, Olov
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    On creating proportional loss-rate differentiation: predictability and performance2001In: Quality of Service - IWQoS 2001: 9th International Workshop Karlsruhe, Germany, June 6-8, 2001 Proceedings / [ed] Lars Wolf, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2001, p. 372-386Conference paper (Refereed)
    Abstract [en]

    Recent extensions to the Internet architecture allow assignment of different levels of drop precedence to IP packets. This paper examines differentiation predictability and implementation complexity in creation of proportional lossrate (PLR) differentiation between drop precedence levels. PLR differentiation means that fixed loss-rate ratios between different traffic aggregates are provided independent of traffic loads. To provide such differentiation, running estimates of loss-rates can be used as feedback to keep loss-rate ratios fixed at varying traffic loads. In this paper, we define a loss-rate estimator based on average drop distances (ADDs). The ADD estimator is compared with an estimator that uses a loss history table (LHT) to calculate loss-rates. We show, through simulations, that the ADD estimator gives more predictable PLR differentiation than the LHT estimator. In addition, we show that a PLR dropper using the ADD estimator can be implemented efficiently.

  • 149.
    Bodin, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Schelén, Olov
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Drop strategies and loss-rate differentiation2001In: Proceedings: Ninth International Conference on Network Protocols, ICNP 2001 : 11 - 14 November 2001, Riverside, California, USA, Los Alamitos, Calif: IEEE Communications Society, 2001, p. 146-154Conference paper (Refereed)
    Abstract [en]

    When offering loss-rate differentiation in IP networks, the drop strategy used can have a considerable influence on packet loss and delay. In particular, a strategy of dropping packets only as they arrive can cause bursty loss patterns and high jitter. When only arriving packets are dropped, the router may need to wait for low priority packets to arrive before dropping any packet. This results in larger queue oscillation than if low priority packets were dropped immediately from the queue. Queue oscillation gives bursty loss patterns and delay jitter. We present simulations showing that dropping packets from the queue gives smoother loss patterns and less jitter than if packets are dropped only as they arrive. These simulations cover both TCP Sack and TCP Reno. WRED with and without the gentle modification is used to make drop decisions.

  • 150.
    Bodin, Ulf
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Schelén, Olov
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Pink, Stephen
    Luleå University of Technology.
    Load-tolerant differentiation with active queue management2000In: Computer communication review, ISSN 0146-4833, E-ISSN 1943-5819, Vol. 30, no 3, p. 4-16Article in journal (Refereed)
    Abstract [en]

    Current work in the IETF aims at providing service differentiation on the Internet. One proposal is to provide loss differentiation by assigning levels of drop procedence to IP packets. In this paper, we evaluate the active queue management (AQM) mechanisms RED In and Out (RIO) and Weighted RED (WRED) in providing levels of drop precedence under different loads. For low drop precedence traffic, FIO and WRED can be configured to offer sheltering (i.e., low drop precedence traffic is protected from losses caused by higher drop precedence traffic). However, if traffic control fails or is inaccurate, such configurations can cause starvation of traffic at high drop precedence levels. Configuring WRED to instead offer relative differentiation can eliminate the risk of starvation. However, WRED cannot, without reconfiguration, both offer sheltering when low drop precedence traffic is properly controlled and avoid starvation at overload of low drop precedence traffic. To achieve this, we propose a new AQM mechanism, WRED with Thresholds (WRT). The benefit of WRT is that, without reconfiguration, it offers sheltering when low drop precedence traffic is properly controlled and relative differentiation otherwise. We present simulations showing that WRT has these properties.

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