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  • 3501.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    A polygon to ellipse transformation enabling fingerprinting and emergency localization in GSM2011In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 60, no 4, p. 1971-1976Article in journal (Refereed)
  • 3502.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Adaptive enhanced cell-ID fingerprinting localization by clustering of precise position measurements2007In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 56, no 5, p. 3199-3209Article in journal (Refereed)
  • 3503.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Clustering and polygon merging algorithms for fingerprinting positioning in LTE2011In: Proc. 5th International Conference on Signal Processing and Communication Systems, Piscataway, NJ: IEEE , 2011, p. 10-Conference paper (Refereed)
  • 3504.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Loop-shaping feedback and feedforward control for networked systems with saturation and delay2017In: Asian journal of control, ISSN 1561-8625, E-ISSN 1561-8625, Vol. 19, no 4, p. 1329-1349Article in journal (Refereed)
  • 3505.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Low complexity Kalman filtering for inter-cell interference and power based load estimation in the WCDMA uplink2011In: Proc. 5th International Conference on Signal Processing and Communication Systems, Piscataway, NJ: IEEE , 2011, p. 10-Conference paper (Refereed)
  • 3506.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    LTE fingerprinting localization with altitude2012In: Proc. 76th Vehicular Technology Conference, Piscataway, NJ: IEEE, 2012Conference paper (Refereed)
  • 3507.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Robust L2 stable networked control of wireless packet queues in delayed Internet connections2016In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 24, no 2, p. 502-513Article in journal (Refereed)
  • 3508.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Wireless feedback and feedforward data flow control subject to rate saturation and uncertain delay2016In: IET Control Theory & Applications, ISSN 1751-8644, E-ISSN 1751-8652, Vol. 10, no 3, p. 346-353Article in journal (Refereed)
  • 3509.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Wireless hybrid positioning based on surface modeling with polygon support2018In: Proc. 87th Vehicular Technology Conference, Piscataway, NJ: IEEE, 2018Conference paper (Refereed)
  • 3510.
    Wigren, Torbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Wireless interference power estimation for inter-cell interference coordination2015In: IET Communications, ISSN 1751-8628, E-ISSN 1751-8636, Vol. 9, no 12, p. 1539-1546Article in journal (Refereed)
  • 3511.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Anderson, Michael
    Kangas, Ari
    Emergency call delivery standards impair cellular positioning accuracy2010In: Proc. International Conference on Communications: ICC 2010, Piscataway, NJ: IEEE, 2010, p. 4655-4660Conference paper (Refereed)
  • 3512.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Colombi, Davide
    Thors, Björn
    Berg, Jan-Erik
    Implication of RF EMF exposure limitations on 5G data rates above 6 GHz2015In: Proc. 82nd Vehicular Technology Conference, Piscataway, NJ: IEEE , 2015Conference paper (Refereed)
  • 3513.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Hellqvist, Per
    Estimation of uplink WCDMA load in a single RBS2007In: Proc. 66th Vehicular Technology Conference, Piscataway, NJ: IEEE, 2007, p. 1499-1503Conference paper (Refereed)
  • 3514.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Jading, Ylva
    Siomina, Iana
    Kangas, Ari
    Tidestav, Claes
    Enhanced WCDMA fingerprinting localization using OTDOA positioning measurements from LTE2012In: Proc. 76th Vehicular Technology Conference, Piscataway, NJ: IEEE, 2012Conference paper (Refereed)
  • 3515.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Karaki, Reem
    Globally stable wireless data flow control2018In: IEEE Transactions on Control of Network Systems, ISSN 2325-5870, Vol. 5, no 1, p. 469-478Article in journal (Refereed)
  • 3516.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Lau, Katrina
    Delgado, Ramón A.
    Middleton, Richard H.
    Delay skew packet flow control in wireless systems with dual connectivity2018In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 67, no 6, p. 5357-5371Article in journal (Refereed)
  • 3517.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Palenius, Torgny
    Optimized search window alignment for A-GPS2009In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 58, no 8, p. 4670-4675Article in journal (Refereed)
  • 3518.
    Wigren, Torbjörn
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Systems and Control. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Automatic control.
    Wennervirta, Jenni
    RTT positioning in WCDMA2009In: Proc. 5th International Conference on Wireless and Mobile Communications, IEEE Computer Society, 2009, p. 303-308Conference paper (Refereed)
  • 3519.
    Wiklander, Erik
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Mobile Resource Awareness2001Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    New types of cellular networks are appearing on the market, such as GPRS and UMTS. In addition to this, an increasing number of places are being equipped with wireless LAN extensions to the Internet. Simultaneously, new mobile devices are becoming available that can perform complex computations based on events from various input devices and/or information sources. The combination of extended network connectivity and new mobile devices creates new opportunities for network computing.

    This paper presents a scenario where network enabled applications can interact with mobile devices to create a smart space. The ambition is to create a system where mobile devices can be aware of what resources are present at a specific location. The prototype solution in this paper uses an XML-based protocol and a tuple space architecture as a message passing mechanism.

  • 3520.
    Willig, Andreas
    et al.
    Department of Computer Science and Software Engineering, University of Canterbury, Christchurch, New Zealand.
    Uhlemann, Elisabeth
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Embedded Systems (CERES).
    Deadline-Aware Scheduling of Cooperative Relayers in TDMA-Based Wireless Industrial Networks2014In: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 20, no 1, p. 73-88Article in journal (Refereed)
    Abstract [en]

    In this paper we consider a scenario in which a set of source nodes wishes to transmit real-time data packets periodically to a central controller over lossy wireless links, while using a TDMA-based medium access control protocol. Furthermore, a number of relay nodes are present which can help the source nodes with packet retransmissions. The key question we consider in this paper is how to schedule the TDMA slots for retransmissions while taking advantage of the relay nodes, so that the average number of packets missing their deadlines is minimized. We provide a problem formulation for the general deadline-aware TDMA relay scheduling problem. Since the design space of the general problem is large, we also present one particular class of restricted TDMA relay scheduling problems. We suggest and numerically investigate a range of algorithms and heuristics, both optimal and suboptimal, of the restricted scheduling problem, which represent different trade-offs between achievable performance and computational complexity. Specifically, we introduce two different Markov Decision Process (MDP) based formulations for schedule computation of the restricted TDMA relay scheduling problem. One MDP formulation gives an optimal schedule, another (approximate) formulation gives a sub-optimal schedule which, however, comes very close to the optimal performance at much more modest computational and memory costs. © 2013 Springer Science+Business Media New York.

  • 3521.
    Willig, Andreas
    et al.
    University of Canterbury, Christchurch, New Zealand.
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    Deadline-Aware Scheduling of Cooperative Relayers in TDMA-Based Wireless Industrial Networks2014In: Wireless networks, ISSN 1022-0038, E-ISSN 1572-8196, Vol. 20, no 1, p. 73-88Article in journal (Refereed)
    Abstract [en]

    In this paper we consider a scenario in which a set of source nodes wishes to transmit real-time data packets periodically to a central controller over lossy wireless links, while using a TDMA-based medium access control protocol. Furthermore, a number of relay nodes are present which can help the source nodes with packet retransmissions. The key question we consider in this paper is how to schedule the TDMA slots for retransmissions while taking advantage of the relay nodes, so that the average number of packets missing their deadlines is minimized. We provide a problem formulation for the general deadline-aware TDMA relay scheduling problem. Since the design space of the general problem is large, we also present one particular class of restricted TDMA relay scheduling problems. We suggest and numerically investigate a range of algorithms and heuristics, both optimal and suboptimal, of the restricted scheduling problem, which represent different trade-offs between achievable performance and computational complexity. Specifically, we introduce two different Markov Decision Process (MDP) based formulations for schedule computation of the restricted TDMA relay scheduling problem. One MDP formulation gives an optimal schedule, another (approximate) formulation gives a sub-optimal schedule which, however, comes very close to the optimal performance at much more modest computational and memory costs.

  • 3522.
    Willig, Andreas
    et al.
    University of Canterbury.
    Uhlemann, Elisabeth
    Högskolan i Halmstad, Inbyggda system (CERES).
    On relaying for wireless industrial communications: Is careful placement of relayers strictly necessary?2012In: IEEE International Workshop on Factory Communication Systems, 2012, p. 191-200Conference paper (Refereed)
    Abstract [en]

    Relaying is a very promising technique to improve the reliability of data transmission in wireless (industrial) networks. With relaying, relay nodes support source nodes in carrying out retransmissions. A common assumption is that relayers should be placed at “good” positions (e.g. in the middle between source and destination) to achieve benefits. In this paper we tackle the question of whether it is strictly necessary to place relayers at “good” positions (which often requires extensive measurements). We present results indicating that the benefits of relaying are achievable even with randomly placed relayers, as long as enough of them are deployed. Specifically, we present results suggesting that with a sufficient (and still not too high) number of randomly deployed relayers, the probability that all packets, sent by source nodes to a central controller in a TDMA round, reach the controller is larger than for the case with source-only retransmissions. This finding holds true both in the absence and the presence of feedback.

  • 3523.
    Willig, Andreas
    et al.
    University of Canterbury, Christchurch, New Zealand.
    Uhlemann, Elisabeth
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Embedded Systems (CERES).
    On relaying for wireless industrial communications: Is careful placement of relayers strictly necessary?2012In: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS, Piscataway, NJ: IEEE Press, 2012, p. 191-200, article id 6242567Conference paper (Refereed)
    Abstract [en]

    Relaying is a very promising technique to improve the reliability of data transmission in wireless (industrial) networks. With relaying, relay nodes support source nodes in carrying out retransmissions. A common assumption is that relayers should be placed at “good” positions (e.g. in the middle between source and destination) to achieve benefits. In this paper we tackle the question of whether it is strictly necessary to place relayers at “good” positions (which often requires extensive measurements). We present results indicating that the benefits of relaying are achievable even with randomly placed relayers, as long as enough of them are deployed. Specifically, we present results suggesting that with a sufficient (and still not too high) number of randomly deployed relayers, the probability that all packets, sent by source nodes to a central controller in a TDMA round, reach the controller is larger than for the case with source-only retransmissions. This finding holds true both in the absence and the presence of feedback. © 2012 IEEE.

  • 3524. Willkomm, Daniel
    et al.
    Hollos, Daniel
    Bohge, Mathias
    Gross, James
    Wolisz, Adam
    Double Hopping: A new Approach for Dynamic Frequency Hopping in Cognitive Radio Networks2008In: IEEE 19th International Symposium on Personal, Indoor and Mobile Radio Communications, 2008. PIMRC 2008, IEEE conference proceedings, 2008, p. 1-6Conference paper (Refereed)
    Abstract [en]

    One of the major challenges in designing cellular cognitive radio (CR) networks is the avoidance of secondary user (SU) interference to so called primary users (PUs) operating in the licensed bands. Usually, SU operation has to be interrupted periodically in order to detect PU activity and avoid the respective frequencies. Recently, dynamic frequency hopping (DFH) mechanisms have been suggested to enable reliable PU detection and continuous SU operation at the same time. Applying DFH in a multi-cell environment adds the challenge of mitigating co-channel interference (CCI). In this paper, we introduce a new DFH approach for cellular CR networks to allow reliable PU detection and continuous SU operation while avoiding CCI: double hopping (DH). We present a distributed frequency assignment heuristic for DH and compare it to the optimal assignment. We show that the performance of the sub-optimal distributed assignment is only slightly worse than the optimal performance, and, thus, outperforms existing distributed approaches by far.

  • 3525.
    Winter, Philipp
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    How China Is Blocking Tor2012Report (Other academic)
    Abstract [en]

    Not only the free web is victim to China’s excessive censorship, but also the Tor anonymity network: the Great Firewall of China prevents thousands of potential Tor users from accessing the network. In this paper, we investigate how the blocking mechanism is implemented, we conjecture how China’s Tor blocking infrastructure is designed and we propose countermeasures. Our work bolsters the understanding of China’s censorship capabilities and thus paves the way towards more effective evasion techniques.

  • 3526.
    Winter, Philipp
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Lindskog, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    How the Great Firewall of China is Blocking Tor2012Conference paper (Refereed)
    Abstract [en]

    Internet censorship in China is not just limited to the web: the Great Firewall of China prevents thousands of potential Tor users from accessing the network. In this paper, we investigate how the blocking mechanism is implemented, we conjecture how China's Tor blocking infrastructure is designed and we propose circumvention techniques. Our work bolsters the understanding of China's censorship capabilities and thus paves the way towards more effective circumvention techniques.

  • 3527.
    Wiren, Jakob
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Data Storage Cost Optimization Based on Electricity Price Forecasting with Machine Learning in a Multi-Geographical Cloud Environment2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As increased demand of cloud computing leads to increased electricity costs for cloud providers, there is an incentive to investigate in new methods to lower electricity costs in data centers. Electricity price markets suffer from sudden price spikes as well as irregularities between different geographical electricity markets.

    This thesis investigates in whether it is possible to leverage these volatilities and irregularities between different electricity price markets, to offload or move storage in order to reduce electricity price costs for data storage.

    By forecasting four different electricity price markets it was possible to predict sudden price spikes and leverage these forecasts in a simple optimization model to offload storage of data in data centers and successfully reduce electricity costs for data storage.

  • 3528.
    Wisell, David
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gavle, Sweden.
    Isaksson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Gavle, Sweden.
    Keskitalo, N.
    A general evaluation criteria for behavioral power amplifier modeling2007In: 69th ARFTG Microwave Measurements Conference - Addressing Metrology Needs for Future High-Speed Information and Communications Systems, 2007, p. 5456311-Conference paper (Refereed)
    Abstract [en]

    In this paper a new goodness measure for behavioral complex envelope power amplifier models is defined in the frequency domain. The measure can be calculated for any input signal using the same formulas, which makes it general and easy to use. The results will however be dependent on the input signal. The total model error, or normalized mean-square error, for power amplifier models are normally dominated by the in-band error, often mainly caused by the linear distortion. The new measure is aimed at capturing the nonlinear modeling performance of the amplifier model. This is of interest since it is most often the nonlinear, rather than the linear, distortion that causes most harm in real-life power amplifier applications.

  • 3529.
    Wolkerstorfer, Martin
    et al.
    FTW Telecommunications Research Center Vienna, Vienna, Austria.
    Jaldén, Joakim
    ACCESS Linnaeus Center, Signal Processing Lab, KTH Royal Institute of Technology, Stockholm, Sweden.
    Nordström, Tomas
    Halmstad University, School of Information Technology, Halmstad Embedded and Intelligent Systems Research (EIS), Centre for Research on Embedded Systems (CERES). FTW Telecommunications Research Center Vienna, Vienna, Austria.
    Column Generation for Discrete-Rate Multi-User and Multi-Carrier Power Control2012In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 60, no 9, p. 2712-2722Article in journal (Refereed)
    Abstract [en]

    We consider a constrained multi-carrier power allocation problem in interference-limited multi-user systems with a finite set of transmission rates. The Lagrange relaxation is a common technique for decomposing such problems into independently solvable per-subcarrier problems. Deviating from this approach our main contribution is the proposal of a novel spectrum management framework based on a Nonlinear Dantzig-Wolfe problem decomposition. It allows for suboptimal initialization and suboptimal power allocation methods with low complexity. While we show that the combinatorial per-subcarrier problems have polynomial complexity in the number of users, we find that such suboptimal methods are indispensable in large systems. Thus we give an overview of various basic dual heuristics and provide simulation results on a set of thousand digital subscriber line (DSL) networks which show the superior performance of our framework compared to previous power control algorithms. © 2012 IEEE.

  • 3530. Wong, E.
    et al.
    Machuca, C. M.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Survivable architectures for power-savings capable converged access networks2016In: 2016 IEEE International Conference on Communications, ICC 2016, IEEE conference proceedings, 2016, p. 365-371, article id 7510719Conference paper (Refereed)
    Abstract [en]

    The reliance on the loss-of-signal (LOS) of upstream transmissions to indicate fiber/component failure is potentially unsuitable in networks that implement sleep/doze mode operation. In such networks, the transition into sleep/doze mode would result in no signal transmission, and when used in conjunction with conventional LOS to indicate network failure, would result in erroneous triggering of false alarm and subsequently protection switching. Recently, converged access networks using a hybrid passive optical architecture, have been favored as a low-cost and high-bandwidth solution to deliver high-bandwidth applications to both fixed access and mobile users. These networks are referred to as Hybrid PON Converged Access Networks. Protection against fiber/equipment failures in these networks is critical considering the customer base, network span, and traffic supported. This paper proposes four survivable architectures for such converged access networks. These architectures combine rapid fault detection and protection switching against high impact failures but without the need to rely on upstream transmissions for LOS detection. A comparison of the four architectures across three different area densities under three deployment scenarios, is presented. Guidance for selecting the best protection architecture to be deployed, considering area densities and deployment scenarios, is provided.

  • 3531.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Connection availability in WDM mesh networks with multiple failures2006In: ICTON 2006: 8th International Conference on Transparent Optical Networks, Vol 3, Proceedings / [ed] Marciniak, M, 2006, p. 126-129Conference paper (Refereed)
    Abstract [en]

    Wavelength Division Multiplexed (WDM) technology has revolutionized wide-area networks. As the amount of traffic carried is very large, any single failure can be catastrophic. Thus, survivability of a network that refers to a network's capability to provide continuous service in the presence of failures has become crucial in such networks. Communication networks are usually designed to survive single failure. However, in large networks the occurrence of multiple concurrent failures cannot be neglected. Therefore, in this paper we study connection availability in WDM networks assuming failures of any multiplicity. Shared Path Protection (SPP) scheme is an efficient network recovery mechanism in terms of network resource utilization and in many related works the SPP scheme has been studied to solve a single failure problem. We apply SPP scheme and propose an analytical model for calculation of connection unavailability in WDM mesh networks with multiple failure assumption. We have evaluated our model by simulations and show that the connection unavailability obtained by simulations is very close to the theoretical value obtained by our algorithm, which proves the accuracy of our model.

  • 3532.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Optical network architectures for datacenters2017In: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2017, Vol. Part F53Conference paper (Refereed)
    Abstract [en]

    The talk will highlight challenges related to dramatically growing datacenter traffic. The advantages of using photonic technology in intra-datacenter networks will be discussed and a crosslayer view of network architecture design will be presented.

  • 3533.
    Wosinska, Lena
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Chen, Jiajia
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Next Generation Optical Access Network Architectures: What is the Best Option?2013Conference paper (Other academic)
  • 3534.
    Wosinska, Lena
    et al.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Haralson, Joanna
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Thylén, Lars
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Öberg, Johnny
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Hessmo, Björn
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Benefit of Implementing Novel Optical Buffers in an Asynchronous Photonic Packet Switch2004In: Proceedings of ECOC-04, 2004Conference paper (Refereed)
  • 3535.
    Wosinska, Lena
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Fiorani, Matteo
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Dreier, Dennis
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    ICT Infrastructure for Smart Cities: Curitiba, Brazil2015Conference paper (Other academic)
  • 3536.
    Wosinski, Lech
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nanophotonic devices based on silicon-on-insulator nanowire waveguides2006In: ICTON 2006: 8th International Conference on Transparent Optical Networks, Vol 1, Proceedings: ICTON, MPM, INDUSTRIAL, PICAW, GOWN / [ed] Marciniak, M, 2006, p. 206-209Conference paper (Refereed)
    Abstract [en]

    While silica-on-silicon is recognized as one of the dominant platforms for microphotonics today, silicon-on-insulator nanowire waveguides appear to be the technology for next generation of super compact integrated devices. Due to very high refractive index contrast and strong light confinement in the core, the waveguide bend radius can be reduced to a few micrometers and the size reduction of the functional integrated circuits can reach several orders of magnitude. An array waveguide grating multi/demultiplexer that usually occupies several square centimetres in silica-on-silicon technology can be reduced to the size of 50 x 50 mu m(2). The performance of such miniaturized devices with submicrometer-size waveguides strongly depends on the fabrication accuracy: high resolution patterning and low roughness etching. High quality and high precision optimized processing is necessary to obtain satisfactory results. We discuss here the technology issues as well as present some fabricated devices based on silicon nanowire waveguides.

  • 3537.
    Wu, Chia-Lung
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Chen, P. -N
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Ming, Xiao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Shin-Lin, S.
    A two-phase maximum-likelihood sequence estimation for receivers with partial CSI2013In: 9th International Conference on Information, Communications and Signal Processing, ICICS 2013, IEEE Computer Society, 2013, p. 6782818-Conference paper (Refereed)
    Abstract [en]

    The optimality of the conventional maximum-likelihood sequence estimation (MLSE), also known as the Viterbi Algorithm (VA), relies on the assumption that the receiver has perfect knowledge of the channel coefficients or channel state information (CSI). However, in practical situations that fail the assumption, the MLSE method becomes suboptimal and then exhaustive checking is the only way to obtain the ML sequence. At this background, considering directly the ML criterion for partial CSI, we propose a two-phase low-complexity MLSE algorithm, in which the first phase performs the conventional MLSE algorithm in order to retain necessary information for the backward VA performed in the second phase. Simulations show that when the training sequence is moderately long in comparison with the entire data block such as 1/3 of the block, the proposed two-phase MLSE can approach the performance of the optimal exhaustive checking. In a normal case, where the training sequence consumes only 0.14 of the bandwidth, our proposed method still outperforms evidently the conventional MLSE.

  • 3538.
    Wu, Hanwei
    et al.
    KTH, School of Electrical Engineering (EES).
    Wang, Qiwen
    KTH, School of Electrical Engineering (EES).
    Flierl, Markus
    KTH, School of Electrical Engineering (EES).
    Tree-Structured Vector Quantization for Similarity Queries2017In: 2017 Data Compression Conference (DCC) / [ed] Bilgin, A Marcellin, MW SerraSagrista, J Storer, JA, IEEE Computer Society, 2017, p. 467-467Conference paper (Refereed)
  • 3539. Wu, J.
    et al.
    Zhou, S.
    Niu, Z.
    Liu, C.
    Yang, P.
    Miao, Guowang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Traffic-Aware Data and Signaling Resource Management for Green Cellular Networks2014Conference paper (Refereed)
    Abstract [en]

    The increasing traffic demands bring heavy load toboth the data and control planes of cellular networks, along withsubstantial energy consumption. To solve the issue, new networkarchitecture that separates signaling and data has been proposedin literature for future green cellular networks. In this paper, weanalyze the data and signaling resource configuration problemin this new network architecture. We find the optimal resourcepartitioning parameters to optimize the blocking performanceand to minimize the overall network power consumption witha blocking probability constraint. More specifically, we adopttraffic-aware resource allocation between the data and signalingbase stations (BSs) to improve network access capability whilereducing the overall network power consumption. Two typesof resource partitioning patterns, complete partitioning andpartial partitioning, are studied. Numerical results show thatgreat energy-saving gain can be achieved compared with thetraditional fixed and traffic-proportional resource partitioningpatterns. Moreover, power consumption and blocking performancetradeoffs are explored, based on which the appropriateresource partitioning pattern can be chosen according to differentquality of service (QoS) requirements.

  • 3540.
    Wu, Jiang
    et al.
    KTH, Superseded Departments, Teleinformatics.
    Maguire Jr., Gerald Q.
    KTH, Superseded Departments, Teleinformatics.
    Agent Based Seamless IP Multicast Receiver Handover2000In: Proceedings of the IFIP TC6/WG6.8 Working Conference on Personal Wireless Communications, Deventer, The Netherlands: Kluwer, B.V. , 2000, p. 213-226Conference paper (Refereed)
  • 3541. Wu, Jing
    et al.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics, Photonics.
    Jin, Yaohui
    Araki, Soichiro
    Special Issue on Optical Network Architectures and Management2011In: Optical Switching and Networkning Journal, ISSN 1573-4277, E-ISSN 1872-9770, Vol. 8, no 4, p. 225-225Article in journal (Other academic)
  • 3542. Wu, Jing
    et al.
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Shen, Gangxiang
    Spadaro, Salvatore
    Advances in optical networks control and management2013In: Optical Switching and Networkning Journal, ISSN 1573-4277, E-ISSN 1872-9770, Vol. 10, no 1, p. 1-2Article in journal (Other academic)
  • 3543. Wu, Jinsong
    et al.
    Bisio, Igor
    Gniady, Chris
    Hossain, Ekram
    Valla, Massimo
    Li, Haibo
    KTH, School of Computer Science and Communication (CSC), Media Technology and Interaction Design, MID.
    Context-aware networking and communications: Part 12014In: IEEE Communications Magazine, ISSN 0163-6804, E-ISSN 1558-1896, Vol. 52, no 6, p. 14-15Article in journal (Refereed)
  • 3544.
    Wu, Jun
    KTH, School of Information and Communication Technology (ICT).
    Signal Collecting Platform and "Handprint" Positioning System2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile computing is an emerging research field in recent years. Although the computation capability of main stream smartphones are several orders of magnitude better than computers twenty years ago, the capacity of battery does not increase at same speed. To save energy, some recent work tries to schedule network traffic according to signal strength variations. To achieve this goal, a database that is used for storing signal strength distribution is essential.We first design and implement a platform to collect cellular network information, including Cell-ID and signal strength information. The platform is designed as a distributed system that supports collecting signal strength data by using crowdsourcing approach.We then deploy the platform and collect signal strength information in Otaniemi area (Finland). After analysing the collected data, we observe several interesting phenomenons. (1) the density of base stations is out of expectation; (2) cells is becoming smaller; (3) in most places a device may connect to different base stations. Based on these observations, we design a new energy-efficient positioning system called “handprint”, which utilises signal strength information from neighbouring smartphones to assist positioning. Compared with Google Geolocation API and other existing work, our “handprint” system can improve positioning accuracy by more than 20%.

  • 3545.
    Wu, Junfeng
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Yang, Tao
    Univ North Texas, Dept Elect Engn, Denton, TX 75203 USA..
    Wu, Di
    Pacific Northwest Natl Lab, Richland, WA 99352 USA..
    Kalsi, Karanjit
    Pacific Northwest Natl Lab, Richland, WA 99352 USA..
    Johansson, Karl Henrik
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Distributed Optimal Dispatch of Distributed Energy Resources Over Lossy Communication Networks2017In: IEEE Transactions on Smart Grid, ISSN 1949-3053, E-ISSN 1949-3061, Vol. 8, no 6, p. 3125-3137Article in journal (Refereed)
    Abstract [en]

    Driven by smart grid technologies, a great effort has been made in developing distributed energy resources (DERs) in recent years for improving reliability and efficiency of distribution systems. Emerging DERs require effective and efficient control and coordination in order to harvest their potential benefits. In this paper, we consider optimal DER coordination problem, where the goal is to minimize the total generation cost while meeting total demand and satisfying individual generator output limit. This paper develops a distributed algorithm for solving the optimal DER coordination problem over lossy communication networks with packet-dropping communication links. Under the assumption that the underlying communication network is strongly connected with a positive probability and the packet drops are independent and identically distributed, we show that the proposed algorithm is able to solve the optimal DER coordination problem even in the presence of packet drops. Numerical simulation results are used to validate and illustrate the proposed algorithm.

  • 3546. Wu, L.
    et al.
    Sun, P.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Information Science and Engineering.
    Hu, Y.
    Wang, Z.
    Sparse Signal Aloha: A Compressive Sensing-Based Method for Uncoordinated Multiple Access2017In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 21, no 6, p. 1301-1304, article id 7849200Article in journal (Refereed)
    Abstract [en]

    We investigate the problem of sparse signal medium access control in the wireless sensor networks. The proposed sparse signal Aloha (SSA) transmits sampled compressive data to the fusion center using Aloha random access protocol. In order to maximize the overall data transmission rate in the presence of packet collision, redundant data are randomly subsampled at individual sensor nodes according to an optimal subsampling rate before transmission. Data loss due to random subsampling and collision in the wireless channel are compensated using compressive sensing recovery method at the fusion center. Simulation results verify the theoretical analysis and show the significant improvement of SSA compared with existing CS-based random access method.

  • 3547.
    Wu, Xiao
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    SIP on an Overlay Network2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the development of mobile (specifically: wide area cellular telephony) technology, users’ requirements have changed from the basic voice service based on circuit switch technology to a desire for high speed packet based data transmission services. Voice over IP (VoIP), a packet based service, is gaining increasing attention due to its high performance and low cost. However, VoIP does not work well in every situation. Today Network address translation (NAT) traversal has become the main obstruction for future VoIP deployment.

    In this thesis we analyze and compare the existing NAT traversal solutions. Following this, we introduce a VoIP over IPSec (VOIPSec) solution (i.e., a VoIP over IPSec virtual private network (VPN) scheme) and an extended VOIPSec solution mechanism. These two solutions were tested and compared to measure their performance in comparison to a version of the same Session Initiation Protocol (SIP) user agent running without IPSec.

    In the proposed VOIPSec solution, the IPSec VPN tunnel connects each of the SIP clients to a SIP server, thus making all of the potential SIP participants reachable, i.e., solving the NAT traversal problem. All SIP signaling and media traffic for VoIP calls are transmitted through this prior established tunnel. This VPN tunnel provides the desired universal means for VoIP traffic to traverse NAT equipment. Additionally, the IPSec VPN also guarantees the security of VoIP calls at the IP level.

    In order to improve the security level of media streams for the VOIPSec solution, we deployed and evaluated an extended VOIPSec solution which provides end-to-end protection of the real time media traffic. In this extended VOIPSec solution, we used SRTP instead of RTP to carry the media content. This extended method was shown to provide all of the advantages of VOIPSec and SRTP without any additional delay for the media traffic (as compared to the VoIPSec solution).

    Note that the solution proposed in this thesis may be of limited practical importance in the future as more NATs become VoIP capable; but the solution is currently essential for facilitating the increasing deployment of VoIP systems in practice. For VoIP calls that do not need end-to-end security, we recommend the use of the VOIPSec solution as a means to solve the NAT traversal problem and to protect traffic at the IP level. When application to application security is not needed we prefer the VOIPSec solution to the extended VOIPSec solution for the following reasons: (1) our test results show that the time for call setup for the extended VOIPSec solution is twice time the time needed for the VOIPSec solution and the extended VOIPSec solution requires the use of user agents that support SRTP. While, the VOIPSec solution does not require a special user agent and all VoIP clients in the market are compatible with this solution. However, when more SIP user agents add support for SRTP, the extended VOIPSec solution will be applicable for users of these SIP user agents.

  • 3548.
    Wu, Yiming
    et al.
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Honeth, Nicholas
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Shi, Zhanpeng
    ABB AB, Substn Automat Prod, Vasteras, Sweden.
    Software Merging Unit based IED Functional Test Platform2015Conference paper (Refereed)
    Abstract [en]

    In Substation Automation Systems, application functions such as monitoring, control, and protection are deployed in intelligent electronic devices (IEDs). Before the IEDs are installed in the substation, functions are tested by the manufactures to ensure that the functions operate properly as designed. A conventional function test platform is made of amplifiers with copper wire connection to the IEDs. It has drawbacks such as high cost, limited flexibility, and limited number of signal channels. With the introduction of the IEC61850 standard, IEDs are able to obtain measurement from merging units (MU) via the process bus. Consequently, using MUs to replace the amplifier for IED function testing has been studied by several research groups. All of them use hardware MUs or power system simulator embedded MUs. These MUs based test platforms have weakness such as limitation of the number of MUs and lower flexibility in MU performance modification, This paper proposes a novel IED functional test platform using software MU (sMU), which mitigates the above limitations. Thanks to the software approach, different MU performance scenarios can be easily configured instead of using a complicated communications simulator. The sMU based test platform concept has been proved by performing accuracy and operate-time tests with transformer differential protection. Comparing with conventional test platform, sMU based test platform has better results in the accuracy tests and similar performance in the operate-time tests. Therefore, it is feasible to use sMU based platform for IED functional tests.

  • 3549.
    Wu, Yiming
    et al.
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Saleem, Arshad
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Nordström, Lars
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    IEC61850 Logical Node Lookup Service Using Distributed Hash Tables2014In: 2014 IEEE PES Innovative Smart Grid Technologies Conference, ISGT 2014, IEEE Computer Society, 2014, p. 6816443-Conference paper (Refereed)
    Abstract [en]

    Development of Information and Communication Technology (ICT) increases the communication capability of equipment in power system and also creates large number of data sources. In order to reliably share these data sources with applications is a new challenge for power system. This paper presents an alternate data delivery system solution using IEC61850 standard Manufactory Messaging Specification (MMS) across wide area networks, utilizing Distributed Hash Table (DHT) for look-up of Logical Nodes addresses.  Result of the proposed scheme is a flexible, autonomous, scalable, and robust method to address Logical Nodes across a Wide Area Network. In comparison with IEC61850-90-2 solution, this solution can help reduce the manual work in configuration of each link, and enables greater flexibility for adding new data points. The presented platform also opens door of providing adaptive data acquisition for power system applications by implementing a filtering function in the ISG.

  • 3550.
    Wu, Yongliang
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Aggregating product reviews for the Chinese market2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As of December 2007, the number of Internet users in China had increased to 210 million people. The annual growth rate reached 53.3 percent in 2008, with the average number of Internet users increasing every day by 200,000 people. Currently, China's Internet population is slightly lower than the 215 million internet users in the United States. [1]

    Despite the rapid growth of the Chinese economy in the global Internet market, China’s e-commerce is not following the traditional pattern of commerce, but instead has developed based on user demand. This growth has extended into every area of the Internet.

    In the west, expert product reviews have been shown to be an important element in a user’s purchase decision. The higher the quality of product reviews that customers received, the more products they buy from on-line shops. As the number of products and options increase, Chinese customers need impersonal, impartial, and detailed products reviews. This thesis focuses on on-line product reviews and how they affect Chinese customer’s purchase decisions.

    E-commerce is a complex system. As a typical model of e-commerce, we examine a Business to Consumer (B2C) on-line retail site and consider a number of factors; including some seemingly subtitle factors that may influence a customer’s eventually decision to shop on website. Specifically this thesis project will examine aggregated product reviews from different on-line sources by analyzing some existing western companies. Following this the thesis demonstrates how to aggregate product reviews for an e-business website.

    During this thesis project we found that existing data mining techniques made it straight forward to collect reviews. These reviews were stored in a database and web applications can query this database to provide a user with a set of relevant product reviews. One of the important issues, just as with search engines is providing the relevant product reviews and determining what order they should be presented in. In our work we selected the reviews based upon matching the product (although in some cases there are ambiguities concerning if two products are actually identical or not) and ordering the matching reviews by date - with the most recent reviews present first.

    Some of the open questions that remain for the future are: (1) improving the matching - to avoid the ambiguity concerning if the reviews are about the same product or not and (2) determining if the availability of product reviews actually affect a Chinese user's decision to purchase a product.

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