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  • 2951. Weyres, Marco
    et al.
    Gross, James
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Effective Service Capacity Analysis of Interference-Limited Multi-Carrier Wireless Systems2013In: Proceedings of the 2013 19th European Wireless Conference (EW), VDE Verlag GmbH, 2013, 1-7 p.Conference paper (Refereed)
    Abstract [en]

    A good utilization of a wireless network while still ensuring QoS-constraints for all users is a hard challenge for service providers. Especially for admission control or handover decisions it is important to have a good approximation of the possible rate a user can achieve with respect to QoS parameters like delay or outage probabilities. Since fourth generation cellular networks utilize a frequency reuse of one, especially terminals at the cell edge suffer from inter-cell interference. In order to provide them with rates that guarantee specific QoS parameters without reserving too much resources, a good prediction of their possible rates is needed. Unfortunately, the prediction of the rates in an interference-limited cell is a complex and hard problem. Hence, it is a common way to simplify calculations by treating interference as additional noise in the used system models. In this paper we derive closed-form solutions for the delay distribution of interference-limited cells with respect to an OFDMA and a round robin scheduling approach. These distributions can be used to predict the possible rates of users given their average received transmitter gains, interferer gains and their QoS-constraints in a very accurate way. We validate our derivations and show that a simplification by treating interference as noise leads to an underestimation of rates which lowers the cell throughput. Furthermore, we show that due to the resulting equations, there is no way to derive the rates for interference limited cells in a linear way from easier solutions given by noise-limited cells.

  • 2952. Wiatr, P.
    et al.
    Forchheimer, R.
    Furdek, Marija
    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).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Yuan, D.
    Hierarchical optical interconnects saving spectrum resources in data center networks2017In: Optics InfoBase Conference Papers, Optics Info Base, Optical Society of America, 2017, Vol. Part F53Conference paper (Refereed)
    Abstract [en]

    This paper presents a hierarchical interconnect architecture for optical data center networks composed of specially designed couplers allowing for significant reduction of required spectral resources.

  • 2953.
    Wiatr, Pawel
    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).
    Wosinska, Lena
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Green WDM-PONs: Exploiting traffic diversity to guarantee packet delay limitation2013In: 2013 17th International Conference On Optical Networking Design And Modeling (ONDM), IEEE , 2013, 229-234 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we propose a scheme tailored for WDM-PONs, which employs dozing mode in transceivers not only at the user side but also at the central office. The objective is to reduce the energy consumption while minimizing the impact on the total packet delay. The proposed scheme is able to take into account the diverse delay requirement of multiple traffic classes by adapting the wakeup time of the transmitter. Simulation results confirm that the proposed scheme can significantly improve the power efficiency in WDM-PONs while maintaining the maximum packet delay at an acceptable level, in particular in cases where multiple traffic classes are considered.

  • 2954.
    Wiberg, Niklas
    KTH, Superseded Departments, Teleinformatics.
    Profile Handling Gateway/Proxy2000Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When home users surf the Internet (i.e. use the World Wide Web) today, be it by dial-up or by other means, they are virtually anonymous to the sites they visit. Many sites would, according to Iquity Systems’ experience, like to know more about their visitors in order to target the advertisements (e.g. banners) displayed, services offered, etc. It is also likely that site owners are interested in the type of people that visit their site.

    Iquity Systems would like to provide a system that is capable of providing Internet site owners with profile data of the visitors, as well as sharing usage accounts with Iquity’s telephony products. The system should also be supportive of a rating model that lets an access provider running the system charge a user differently for the access, depending on whether the user is presented with targeted advertisements or not. This solution shall be able to be integrated with other parts of the company’s IQ platform. One of these parts is a system for accounting, while another is a user profile handling database.

    This paper discusses the design of such a system.

  • 2955.
    Wiberg, Per-Arne
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS). Free2move AB.
    Bilstrup, Urban
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS). Free2move AB.
    Wireless Technology in Industry – Applications and User Scenarios2001In: 2001 8th IEEE International Conference on Emerging Technologies and Factory Automation: Proceedings: ETFA 2001, October 15-18, 2001, Antibes-Juan les Pins, France, vol. 1, Piscataway, NJ: IEEE Press, 2001, 123-131 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we draw a map of the wireless technology landscape, and place different industrial applications in this context. It is clear that in order to implement wireless communication in safety critical applications more research is needed. We describe one approach aiming at the very low bit error rates of these applications.

  • 2956.
    Wickbom, Carl
    KTH, Superseded Departments, Teleinformatics.
    SIP and payments: a way of controlling the price2000Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    IP-telephony is said to be the future of telephony, reducing infrastructure investments and enabling new services. IP-telephony solutions exist already in some business buildings as a replacement for PSTN or on the Internet as IP-to-IP telephony. However, before IP-telephony will be a realistic replacement for PSTN two major problems must be solved though; billing and guarantee of the expected QoS. Without the possibility of revenue no company would like to invest money and without QoS no customer will want to replace PSTN with IP-telephony. IP-to-IP telephony exists with best effort traffic for free today, and it will not be possible to charge for it in the future. By introducing value-added features such as PSTN gateway connection, bandwidth reservation and services such as call screening and redirecting, a way of charging the customer is presented in this report.

    The payment solution developed in this thesis is based on SIP and Jalda. The system is built in modules, all with a specific task, hence creating a distributed system, which does not depend on a central part, and following existing standards, avoiding a proprietary solution. It is also general enough to support other types of media than speech, enabling several business ideas including video on demand.

    Security has to be considered seriously when dealing with Internet payments. The solution presented contains both the advantages of SIP with authentication and message encryption, as well as authentication and accounting by Jalda. Authorization is not a problem, as no one will get access to the services without paying, and anyone willing to pay will be granted access. It ends up being a distributed payment solution.

    SIP has the necessary characteristics for constructing billing solutions. As payment seems to be a solvable problem there remains one major difficulty with IP-telephony. Until QoS can be guaranteed or the interference reduced to a minimum, it is not reasonable to imagine IP-telephony replacing PSTN except in well managed intranets where the network can be over dimensioned in such a way as to provide the necessary QoS.

  • 2957.
    Wickman, Tomas
    KTH, School of Information and Communication Technology (ICT).
    Evaluation of communication protocols between vehicle and server: Evaluation of data transmission overhead by communication protocols2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis project has studied a number of protocols that could be used to communicate between a vehicle and a remote server in the context of Scania’s connected services. While there are many factors that are of interest to Scania (such as response time, transmission speed, and amount of data overhead for each message), this thesis will evaluate each protocol in terms of how much data overhead is introduced and how packet loss affects this overhead. The thesis begins by giving an overview of how a number of alternative protocols work and what they offer with regards to Scania’s needs. Next these protocols are compared based on previous studies and each protocol’s specifications to determine which protocol would be the best choice for realizing Scania’s connected services. Finally, a test framework was set up using a virtual environment to simulate different networking conditions. Each of the candidate protocols were deployed in this environment and setup to send sample data. The behaviour of each protocol during these tests served as the basis for the analysis of all of these protocols. The thesis draws the conclusion that to reduce the data transmission overhead between vehicles and Scania’s servers the most suitable protocol is the UDP based MQTT SN.

  • 2958.
    Widfeldt, Fredrik
    KTH, Superseded Departments, Teleinformatics.
    sage of LDAP for managing users and resources in a computer network1997Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today most organizations keep several separated information directories in which for example computer passwords, e-mail addresses, telephone numbers etc. are stored. A big problem is that much of the information is stored in more than one of the directories and thus it is easy for inconsistencies to develop between the directories. A solution to the problem is to store the information only once - in a central directory server where client applications could access it. LDAP is a protocol used by clients to retrieve information from a directory server.

    This report describes how an LDAP directory may be used to share user data in a computer network. First the concept of distributed directory information is presented. Then LDAP is carefully described and compared with X.500, a larger and more complex service. After that we look at the possibility to implement LDAP when developing own systems. Deployment issues and available LDAP products are discussed. A project demo system is presented and described. The demo system shows how different systems can share user information stored in an LDAP directory and how operating systems may be migrated with the directory. One of the more important parts of the system is a gateway server, forwarding NIS requests to the LDAP directory.

    The goal of the report is to make the reader aware of distributed directory services and what important role they probably will have in the near future.

  • 2959.
    Wiese, Moritz
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Johansson, Karl H.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Oechtering, Tobias J.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Papadimitratos, Panos
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Sandberg, Henrik
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Uncertain wiretap channels and secure estimation2016In: 2016 IEEE International Symposium on Information Theory, Institute of Electrical and Electronics Engineers (IEEE), 2016, 2004-2008 p.Conference paper (Refereed)
    Abstract [en]

    The zero-error secrecy capacity of uncertain wiretap channels is defined. If the sensor-estimator channel is perfect, it is also calculated. Further properties are discussed. The problem of estimating a dynamical system with nonstochastic disturbances is studied where the sensor is connected to the estimator and an eavesdropper via an uncertain wiretap channel. The estimator should obtain a uniformly bounded estimation error whereas the eavesdropper's error should tend to infinity. It is proved that the system can be estimated securely if the zero-error capacity of the sensor-estimator channel is strictly larger than the logarithm of the system's unstable pole and the zero-error secrecy capacity of the uncertain wiretap channel is positive.

  • 2960.
    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, 1971-1976 p.Article in journal (Refereed)
  • 2961.
    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, 3199-3209 p.Article in journal (Refereed)
  • 2962.
    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, 10- p.Conference paper (Refereed)
  • 2963.
    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, 1329-1349 p.Article in journal (Refereed)
  • 2964.
    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, 10- p.Conference paper (Refereed)
  • 2965.
    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)
  • 2966.
    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, 502-513 p.Article in journal (Refereed)
  • 2967.
    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, 346-353 p.Article in journal (Refereed)
  • 2968.
    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, 1539-1546 p.Article in journal (Refereed)
  • 2969.
    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, 4655-4660 p.Conference paper (Refereed)
  • 2970.
    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)
  • 2971.
    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, 1499-1503 p.Conference paper (Refereed)
  • 2972.
    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)
  • 2973.
    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. 5Article in journal (Refereed)
  • 2974.
    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, 4670-4675 p.Article in journal (Refereed)
  • 2975.
    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, 303-308 p.Conference paper (Refereed)
  • 2976.
    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.

  • 2977.
    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, 73-88 p.Article 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.

  • 2978.
    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, 73-88 p.Article 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.

  • 2979.
    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, 191-200 p.Conference 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.

  • 2980.
    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, 191-200 p., 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.

  • 2981. 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, 1-6 p.Conference 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.

  • 2982.
    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.

  • 2983.
    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.

  • 2984.
    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, 5456311- p.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.

  • 2985.
    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, 2712-2722 p.Article 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.

  • 2986. 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, 365-371 p., 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.

  • 2987.
    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, 126-129 p.Conference 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.

  • 2988.
    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.

  • 2989.
    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)
  • 2990.
    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)
  • 2991.
    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)
  • 2992.
    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, 206-209 p.Conference 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.

  • 2993.
    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, 6782818- p.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.

  • 2994. 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.

  • 2995.
    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, 213-226 p.Conference paper (Refereed)
  • 2996. 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, 225-225 p.Article in journal (Other academic)
  • 2997. 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, 1-2 p.Article in journal (Other academic)
  • 2998. 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, 14-15 p.Article in journal (Refereed)
  • 2999.
    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%.

  • 3000. 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, 1301-1304 p., 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.

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