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  • 3101.
    Wase, Ulrika
    KTH, Superseded Departments, Teleinformatics.
    Integration av Orbix och distributionen av objekt inom Ericsson Broadband System1996Independent thesis Advanced level (degree of Master (Two Years)), 12 credits / 18 HE creditsStudent thesis
    Abstract [en]

    Distributed-object computing is distributed computing where objects, instead of processes, are the components of distribution. The most important part of distributed-object computing is an Object Request Broker (ORB) which handles all the practical things of communication.

    The most influential standardspecification of ORBs is CORBA (Common Object Request Broker Architecture). In CORBA an Interface Definition Language (IDL-language) is included. In this language one writes interfaces to objects. In that way the user of the object does not have to know the implementation, only the interface. On the market there are several implementations of CORBA and one of these is Orbix. Within the work with Ericsson Broadband System (EBS) an IDL-language and a kind of an ORB have been developed.

    In this master's thesis presentation a theoretical description of the above will be made. A proposal of how to implement a dialogue, the one that is described in the EBS dialogue concept, between one object in EBS and one in Orbix, will also be presented.

    The implementation proposal is described by the included files and their assignment, however the necessary code will not be presented.

  • 3102.
    Wazir, Omerjan
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Frantsalis, Ioannis
    KTH, School of Technology and Health (STH), Medical Engineering, Computer and Electronic Engineering.
    Prestandautvärdering av Bluetooth och Wi-Fi för en smart hubb2017Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis has been carried out on behalf of the consulting company Seavus to re-duce cable usage in their office. Smart hubs (i.e. a central control unit) are made tomake usage of devices more effective.One problem is to decide between Bluetooth and Wi-Fi for communication betweenthe user and the smart hub. The choice may depend upon several factors such asbandwidth (throughput), jitter (variation in delay) and packet loss, which are im-portant parameters for assessing the quality of the communication channel.The HW-platform Raspberry Pi and compatible software was used as a measure-ment tool to test Bluetooth and Wi-Fi in different environments.The result showed that Wi-Fi is best suited for communication systems that requirehigh bandwidth and low jitter, and where high amount of packet loss is tolerable.Bluetooth is best suited for communication systems where low bandwidth and highjitter is tolerable, and minimal packet losses preferred.

  • 3103. Weeraddana, P. C.
    et al.
    Fischione, Carlo
    KTH, School of Electrical Engineering (EES), Network and Systems engineering.
    On the Privacy of Optimization2017In: IFAC-PapersOnLine, ISSN 2405-8963, Vol. 50, no 1, p. 9502-9508Article in journal (Refereed)
    Abstract [en]

    In distributed or multiparty computations, optimization theory methods offer appealing privacy properties compared to cryptography and differential privacy methods. However, unlike cryptography and differential privacy, optimization methods currently lack a formal quantification of the privacy they can provide. The main contribution of this paper is to propose a quantification of the privacy of a broad class of optimization approaches. The optimization procedures generate a problem's data ambiguity for an adversarial observer, which thus observes the problem's data within an uncertainty set. We formally define a one-to-many relation between a given adversarial observed message and an uncertainty set of the problem's data. Based on the uncertainty set, a privacy measure is then formalized. The properties of the proposed privacy measure are analyzed. The key ideas are illustrated with examples, including localization and average consensus.

  • 3104.
    Wei, Li
    KTH, Superseded Departments, Teleinformatics.
    Gateway between Packet and Switched Networks for Speech Communication1994Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This report is a result of a six month thesis work which was carried out and completed with the support of Ericsson Radio Systems AB in Kista, Stockholm. The purpose of this work was to connect the ordinary telephone world and the computer world by building a gateway between them. Since the hardware today is already qualified for such an idea, sofware construction including programming in Erland and C became the major task of the thesis. The system consists of an Ericsson MD110, an embedded computer as the gateway, programs supporting speech communication between workstations over an Ethernet LAN, speech communication between telephones attached to the MD110, and the speech communication between obe telephone and one workstation via the gateway.

  • 3105.
    Weltz, Max
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Dial over Data solution2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The increased use of computer networks has lead to the adoption of Internet-based solutions for reducing telephony costs. This has proved to be a boon to callers who can reach the other party directly via the Internet. Unfortunately numerous business persons still need to call to and from mobile phones which are currently a domain where the customers are generally tightly bound to their operators.

    To provide a simple solution to this problem for companies, Opticall AB has designed an integrated system called the Dial over Data solution, coupling a mobile interface with a low-rate communication channel, which allows calls to be originated remotely at the best price, exploiting the customer company's existing network. This scheme allows the customer company to easily control telecommunications costs, to monitor their employees' efficiency, and more generally speaking to claim a central role in the communications of their employees. The proposed solution allows distant callers (usually employees of the customer company) to benefit from the company's internal network, which is usually more cost effective and offering connectivity to more networks than a cell phone. The Dial over Data solution enables communication between any phone accessible from the customer company's telephony network (such as SIP clients, landline phones, and mobile phones) at a lower cost.</p> This thesis project analyzes existing technologies and compares them to the pre-existing prototype to ascertain the validity of the method and of the components used. This project also explains the improvements brought to the features offered by the DoD solution: the initial prototype has been developed into a stable and functional product, and has been tested internally. Prompted by a need for scalability and additional features, the replacement of Asterisk for the handling of SIP calls by other SIP servers has also been considered and tested.

  • 3106.
    Wen, Daliang
    KTH, Superseded Departments, Teleinformatics.
    MPLS Label Distribution in an Edge Router1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The rapid growth of the Internet has increased the demand for higher bandwidth and better performance. One of the alternatives to satisfy such demands MPLS, (Multi-Protocol Label Switching). The key feature of MPLS is IP switching. It maps the destination address to a locally defined label. The packets can then be forwarded through the network by only examining the label value and no further routing table lookups are needed. One of the key components of MPLS’s is Label Distribution. The goal of Label Distribution is to negotiate labels with the neighbor MPLS nodes using a signaling protocol LDP (Label Distribution Protocol) and update the label information in a local database called LIB (Label Information Base).

    In this thesis, the author will present an overview of the MPLS network and the MPLS system components within an Label Edge Router (LER), which is a router located at the edge of an MPLS network. Furthermore, the implementation of the Label Distribution component in a Label Edge Router of an MPLS system is described and evaluated.

  • 3107.
    Wen, Wei
    et al.
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    Khatibi, Siamak
    Blekinge Institute of Technology, Faculty of Computing, Department of Communication Systems.
    A Software Method to Extend Tonal Levels and Widen Tonal Range of CCD Sensor Images2015In: 2015 9TH INTERNATIONAL CONFERENCE ON SIGNAL PROCESSING AND COMMUNICATION SYSTEMS (ICSPCS), IEEE Communications Society, 2015Conference paper (Refereed)
    Abstract [en]

    As one of important outcomes of the past decades of researches on sensor arrays for digital cameras, the manufacturers of sensor array technology have responded to the necessity and importance of obtaining an optimal fill factor, which has great impact on collection of incident photons on the sensor, with hardware solution e.g. by introducing microlenses. However it is still impossible to make a fill factor of 100% due to the physical limitations in practical development and manufacturing of digital camera. This has been a bottle neck problem for improving dynamic range and tonal levels for digital cameras e.g. CCD cameras. In this paper we propose a software method to not only widen the recordable dynamic range of a captured image by a CCD camera but also extend its tonal levels. In the method we estimate the fill factor and by a resampling process a virtual fill factor of 100% is achieved where a CCD image is rearranged to a new grid of virtual subpixels. A statistical framework including local learning model and Bayesian inference is used for estimating new sub-pixel intensity values. The highest probability of sub-pixels intensity values in each resampled pixel area is used to estimate the pixel intensity values of the new image. The results show that in comparison to the methods of histogram equalization and image contrast enhancement, which are generally used for improving the displayable dynamic range on only one image, the tonal levels and dynamic range of the image is extended and widen significantly and respectively.

  • 3108.
    Wendelin, Kurt Kristoffer
    KTH, Superseded Departments, Teleinformatics.
    Platform Independent Software for Remote Control of a GPS Receiver1998Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With all of the excitement over the World Wide Web on the desktop, the benefits of applying the same technology to embedded devices were fully realized only recently. A device attached to the Internet with an HTTP server running on it can provide for remote access to documentation, monitoring, and configuration of the device from a Web browser on any platform.

    In this project, the Jupiter GPS receiver is used as a prototype device to explore this concept. A client-server system gives access to the full functionality of the GPS attached to a remote host. The client is written in Java and documented in HTML, and the GPS receiver is connected to a Motorola PowerPC board running the VxWorks real-time operating system. This integrates important Web technologies into an embedded environment.

  • 3109.
    Wennerström, Hjalmar
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    A Node-Link Perspective on the Impact of Local Conditions in Sensor Networks2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sensor networks are made up of small battery-powered sensing devices with wireless communication capabilities, enabling the network to monitor the environment in which it is deployed. Through their flexible and cable-free design these networks open up for new deployment scenarios that were previously not plausible such as during a natural disaster. Motivated by scenarios where centralized oversight is not possible the focus of this thesis is to equip nodes with further adaptability to changes in the links it has with other nodes. This is achieved through contributions in three areas focusing on observations from a node-link perspective.

    First, the impact the local environment has on the nodes is explored by deploying a sensor network outdoors next to a meteorological station to correlate the variations in link quality to the changes in the environment. The work identifies temperature as the main factor, where through further investigations in a controlled setting, a linear relationship between the decrease in signal quality and the increase in temperature is described.

    Secondly, the thesis address how nodes in a sensor network can be motivated to exchange data by modeling it as a game. The game theoretic design is motivated by the absence of any centralized control and focus on the nodes as individual users in the network. The presented design motivates the selfish nodes to participate in the exchange of sensor data, showing that it is the best strategy.

    Lastly, by exploring and understanding how connections in a mobile sensor network occur, nodes are given more flexibility to determine how to send and sample sensor data. This adaptability to contact occurrences is shown to provide better ways of sending data by selecting higher quality links as well as making sampling more energy preserving by reducing the rate in the vicinity of other nodes.

  • 3110.
    Wennerström, Hjalmar
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Division of Computer Systems. Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Meteorological impact and transmission errors in outdoor wireless sensor networks2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Wireless sensor networks have been deployed outdoors ever since their inception. They have been used in areas such as precision farming, tracking wildlife, and monitoring glaciers. These diverse application areas all have different requirements and constraints, shaping the way in which the sensor network communicates. Yet something they all share is the exposure to an outdoor environment, which at times can be harsh, uncontrolled and difficult to predict. Therefore, understanding the implications of an outdoor environment is an essential step towards reliable wireless sensor network operations.

    In this thesis we consider aspects of how the environment influence outdoor wireless sensor networks. Specifically, we experimentally study how meteorological factors impact radio links, and find that temperature is most significant. This motivates us to further study and propose a first order model describing the impact of temperature on wireless sensor nodes. We also analyze transmission errors in an outdoor wireless sensor networks, identifying and explaining patterns in the way data gets corrupted. The findings lead to a design and evaluation of an approach for probabilistic recover of corrupt data in outdoor wireless sensor networks. Apart from the experimental findings we have conducted two different outdoor deployments for which large data sets has been collected, containing both link and meteorological measurements.

  • 3111.
    Wennerström, Hjalmar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rensfelt, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Nordén, Lars-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A long-term study of correlations between meteorological conditions and 802.15.4 link performance2013In: Proc. 10th International Conference on Sensing, Communications, and Networking, IEEE Communications Society, 2013, p. 221-229Conference paper (Refereed)
  • 3112.
    Wennerström, Hjalmar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rensfelt, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Nordén, Lars-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A Long-Term Study on the Effects of Meteorological Conditions on 802.15.4 Links2012In: 8th Swedish National Computer Networking Workshop, Stockholm, June 7-8, 2012Conference paper (Refereed)
    Abstract [en]

    Remote monitoring of natural phenomena using wireless sensor networks requires these networks to successfully operate while being exposed to the surrounding environment. Weather conditions are an essential aspect of the environment, therefore it is important to understand the effects of weather on sensor networks. This understanding is especially important since weather varies strongly over time and affects the communication between sensor nodes. In our ongoing work we study how different meteorological conditions influence radio links in outdoor wireless sensor networks that use IEEE 802.15.4 for communication. We deploy an experimental setup next to a meteorological research station and aim to run experiments over several months in order to capture both short- and long-term changes in the link characteristics. We show some initial measurements of the deployment, highlighting influences on packet reception rate and signal strength.

  • 3113.
    Wennerström, Hjalmar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    McNamara, Liam
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Nordén, Lars-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A Study of Packet Errors on Outdoor 802.15.4 Links2013In: The 9th Swedish National Computer Networking Workshop 2013, 2013Conference paper (Refereed)
  • 3114.
    Wennerström, Hjalmar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    McNamara, Liam
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Nordén, Lars-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Transmission errors in a sensor network at the edge of the world2013In: Proc. 5th Extreme Conference on Communication, New York: ACM Press, 2013Conference paper (Refereed)
    Abstract [en]

    The performance of an outdoor wireless sensor network for remote monitoring is dictated by its ability to deliver sensed data to a sink. The often isolated location means that radio interference is typically low and with different patterns in transmission errors compared to an indoor deployment. To better understand these processes, we investigate packet errors in such a network. Specically, we study characteristics of decoding errors within 802.15.4 transmissions.

    We describe the experimental deployment of an outdoor sensor network, located above the Arctic circle, where we log both successfully received and broken packets. Results indicate that a substantial amount of received packets contain errors, where the errors in each packet are typically few. We distinguish between transmission errors and payload errors, and find that transmission errors are equally probable over all positions of a packet, whereas bit errors in the payload are not. This results in some bits having a 25% higher risk of being corrupted than others.

  • 3115.
    Wennerström, Hjalmar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Towards even coverage monitoring with opportunistic sensor networks2016In: Proc. 11th ACM MobiCom Workshop on Challenged Networks, New York: ACM Press, 2016, p. 81-86Conference paper (Refereed)
  • 3116.
    Wennerström, Hjalmar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Smith, David
    NICTA.
    Considering Multi-Contact Encounters in Opportunistic Networks2015In: Proceedings of the 10th ACM MobiCom Workshop on Challenged Networks, ACM Digital Library, 2015Conference paper (Refereed)
    Abstract [en]

    Opportunistic networks, often characterized by their intermittent connectivity and sparsity of nodes, has sparked routing in these networks to focus on isolated contact opportunities. Routing has predominantly been viewed as an exchange of messages between a pair of nodes. In this paper, we take a new look at contact opportunities, specifically focusing on the occurrence of having multiple simultaneous node contacts. Multi-contact encounters warrants a more holistic view of routing decisions, where more factors than just the features of a message-node tuple can be considered. We discuss these aspects and propose a protocol addition to leverage multi-contact opportunities with the notion of heterogeneous link quality, in order to limit energy consumption. The approach, implemented for the Epidemic, Spray-and-Wait and PRoPHETv2 protocols, re-evaluates routing decisions, weighting the routing metrics value against the estimated cost of the relay. Results indicate a two to three fold decrease in the number of messages lost, as well as a reduction in message relays, while maintaining a high delivery ratio for all three protocols.

  • 3117. Wennervirta, Jenni
    et al.
    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.
    RTT positioning field performance2010In: IEEE Transactions on Vehicular Technology, ISSN 0018-9545, E-ISSN 1939-9359, Vol. 59, no 7, p. 3656-3661Article in journal (Refereed)
  • 3118.
    Wennlund, Andreas
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    Context-aware Wearable Device for Reconfigurable Application Networks2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Context information available in wearable devices is believed to be useful in many ways. It allows for hiding much of the complexity from the user, thus enabling simpler user interfaces and less user interaction when carrying out tasks on behalf of a user, as well as enabling network operators to provide a better interface to thirdparty service providers who will provide and deliver wireless services. Using the available context information from the wearable device, optimization of service delivery in wireless networks, such as setting up optimal delivery paths between two wearable devices, may be possible without using a third party to do negotiations. In order to fully enable context-awareness, a clear model for how to sense, manage, derive, store, and exchange context information must be defined. This will then provide the platform needed to enable development of context-aware applications that can exploit the possibilities of context-aware computing. The model must take into consideration parameters such as memory usage and power and bandwidth consumption, in order to be efficient on all types of platforms and in all types of networks. It must also be modular enough to survive replacing and upgrading of internal parts.

    Today little research is available about sensing context information, sensor management, APIs towards other applications, and how and how often to present context information to applications. Since context aware computing relies heavily on the ability to obtain and represent context information, sensing strategies greatly affect efficiency and performance. It is therefore of great interest to develop and evaluate models for carrying out these tasks in order to exploit the results of context awareness research. This thesis will identify and design several components of such a model, as well as test and evaluate the design, in order to be able to make conclusions to whether is lives up to the expectations stated.

    In order to make the proper design decisions, a full understanding of the context-awareness research area and the goals and purposes of context-aware computing are required. To understand the entire picture is crucial to find a suitable solution. Therefore, determining an efficient sensor input and management strategy, along with a powerful and flexible API for applications, which are the goals of this thesis, fully qualifies as a significant master thesis assignment.

  • 3119.
    Wennström, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Kontinuerlig temperaturmätning i bädden på gratevagnar2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Luossavaara-Kiirunavaara Aktiebolag (LKAB) is a mining group with iron ore mining as the main business. One of the products is produced by refining iron ore to iron pellets, which is a quality and environmentally clever product  in steel production.

                                       

    When iron pellets are produced by roasting green pellets the temperature is very important. The goal is to get as much oxidation as possible from hematite to magnetite and to get correct mechanical properties. To control the process it’s important to know the temperature of the green pellets specifically and not the surrounding mechanical structure, ceramics lining in the furnace and the influence from radiation.

     

    The goal of the project is to examine possibilities to measure temperature with a permanent measurement system of green pellets which are transported on grate cars trough pellet plant. The measurement system has to meet some requirements of environment, portability and operating time.

    Analysis of the environment has been made to get specification of what a measurement system has to withstand. Proposition about assembly location has been investigated by analysis of the environment. A thermal analysis has been made of electronic components, especially electronic components that can be used in a measurement system. A analysis has also been made of which electronic components that are suited for a measurement system and can withstand the heat. A development measurement system has been developed from the results of the analysis. The system has been constructed to measure the temperature of what a system can be exposed of on a grate car. This with wireless and data-logging support and future measurements possibilities with three thermocouples of type S.

     

    Wireless data transfer was examined to see what type is most suited for the task with knowledge of environment, transmission range, radiation and power consumption. Power sources was examined to find a power source with longest working time and highest functionality. Heat insulation and reflective materials has been investigated with the goal to get the temperature in the system enclosure as low as possible. Some different types of temperature sensors that can measure temperatures up to 1500°C and which can be mounted on a grate car has been evaluated.

  • 3120.
    Westergren, Urban
    et al.
    KTH, School of Information and Communication Technology (ICT), Optics and Photonics. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Yu, Yichuan
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Jänes, Peter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Holmström, Petter
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Thylén, Lars
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT. KTH, School of Information and Communication Technology (ICT), Centres, Kista Photonics Research Center, KPRC.
    Efficient and compact light-intensity modulators for high frequencies and high bitrates2006In: ICTON 2006: 8th International Conference on Transparent Optical Networks, Vol 2, Proceedings: ESPC, NAON / [ed] Marciniak, M, 2006, p. 142-145Conference paper (Refereed)
    Abstract [en]

    Electroabsorption modulators (EAM) based on quantum-confined Stark effect (QCSE) in multiple-quantum wells (MQW) have been demonstrated to provide high-speed, low drive voltage, and high extinction ratio. They are compact in size and can be monolithically integrated with source lasers. In order to achieve both high speed and low drive-voltage operation, travelling-wave (TW) electrode structures can be used for EAMs. Modulation bandwidths of 100 GHz (-3 dBe) have been accomplished and transmission at 80 Gbit/s with non-return-to-zero (NRZ) code has been demonstrated for InP-based TWEAMs, indicating the possibility of reaching speeds of IOOGbit/s and beyond. In order to further increase the efficiency and reduce the drive voltage, MQW structures using intersubband (IS) instead of interband (QCSE) absorption are being investigated. Materials systems with large conduction band offset, such as GaN/Al(Ga)N or InGaAs/AlAsSb, are required for IS modulators. Critical for the performance of IS modulators is the linewidth of the absorption peak, hence IS modulators have the potential to outperform interband modulators given that a sufficiently high material quality can be achieved.

  • 3121.
    Westermark, Christian
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Mobile Multiplayer Gaming2007Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The last ten years, online multiplayer games have become very popular. During the same time period mobile terminals and cellular networks have undergone a tremendous technical evolution. Therefore it is natural to wonder why we have not seen an online mobile multiplayer gaming revolution yet. The answer to this question is of great value for companies selling mobile systems. This answer is important in order to understand how to fill up today’s empty networks with traffic and what kind of traffic these games will generate.

    This thesis is a continuation of Mattias Åkervik’s thesis. It gives the reader an understanding of what kind of wireless technologies are on the market today and how they perform. Given this performance background, some suitable games were chosen to examine how they perform over a particular cellular network and to determine the perceived gaming quality that a user experience. The thesis also examines the particular packet traffic characteristics generated by these games to gain a better understanding of how to better adapt cellular networks towards gaming.

    Finally the market will be analyzed. Not only how large this potential market is, but to examine if there are some market issues preventing the revolution in network cellular on-line multiplayer games.

  • 3122.
    Westin, Ola
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Information Technology, IMIT.
    TCP Performance in Wireless Mobile Multi-hop Ad Hoc Networks2003Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    There are many issues that limit the performance of wireless mobile multi-hop ad hoc networks (MANETs). One of them is that TCP is not well adapted to networks where routes can change or disappear often. In this paper the behaviour of a standard TCP implementation is studied in situations typical for MANETs and compared to the behaviour of a partial implementation of a ATCP, a TCP modification that is intended to increase performance in MANETs.

    Simulations with simple scenarios show that TCP easily creates a full network load which causes send failures and decreased throughput performance. In some cases the partial ATCP implementation increases throughput but more often it causes an increased amount of duplicate retransmissions. In these scenarios it is unlikely that even a complete ATCP implementation would increase throughput performance.

    A few modifications to ATCP and TCP are analysed. Especially a limit of the congestion window size shows a large throughput increase. The results are inconclusive, the simulations are too simple to show if the results are applicable in more complex scenarios. It is not clear if ATCP actually is useful in a MANET.

  • 3123. 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, p. 1-7Conference 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.

  • 3124. Wiatr, P
    et al.
    Chen, Jiajia
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Monti, Paolo
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Wosinska, Lena
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS, Optical Network Laboratory (ON Lab).
    Yuan, D.
    Device reliability performance awareness: Impact of RWA on EDFA failure reparation cost in optical networks2017In: Proceedings of 2017 9th International Workshop on Resilient Networks Design and Modeling, RNDM 2017, Institute of Electrical and Electronics Engineers Inc. , 2017Conference paper (Refereed)
    Abstract [en]

    High reliability performance of network is essential to minimize the possible network service interruption time, particularly in optical backbone networks where a large amount of data can be affected by a single failure. The existing studies on improvement of network reliability performance assume that failures of network devices are not related to the traffic load, which on the other hand, is not always true. For example, the lifetime of erbium doped fiber amplifier (EDFA) depends on the number of amplified lightpaths passing through. Encouraged by this observation, in this paper, we investigate the impact of used routing and wavelength assignment (RWA) algorithm on the number of failures in the network, and as a consequence on the network operational cost related to the failure reparation. We propose and evaluate a novel RWA approach, referred to as reliability performance aware RWA (RA-RWA), taking into account particular EDFA reliability performance characteristics with the goal of reducing the number of EDFA failures. The assessment results show that the operational cost related to EDFA failure reparation is impacted by the chosen RWA. The proposed RA-RWA provides 6% reduction, while other analyzed RWA algorithm, i.e., least loaded path (LLP), causes significant rise (up to 27%) of EDFA related failure reparation cost compared to the classical shortest path (SP) approach. In addition, RA-RWA offers further benefits in terms of reduced blocking probability compared to the SP. Concluding, we show that considering device reliability performance characteristics in RWA is important for the optical network operators as it can impact the network operational cost related to EDFA failure reparation.

  • 3125. 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.

  • 3126.
    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, p. 229-234Conference 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.

  • 3127.
    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.

  • 3128.
    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, p. 123-131Conference 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.

  • 3129.
    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.

  • 3130.
    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.

  • 3131.
    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.

  • 3132.
    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, p. 2004-2008Conference 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.

  • 3133.
    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)
  • 3134.
    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)
  • 3135.
    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)
  • 3136.
    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)
  • 3137.
    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)
  • 3138.
    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)
  • 3139.
    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)
  • 3140.
    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)
  • 3141.
    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)
  • 3142.
    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)
  • 3143.
    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)
  • 3144.
    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)
  • 3145.
    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)
  • 3146.
    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)
  • 3147.
    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)
  • 3148.
    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)
  • 3149.
    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.

  • 3150.
    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.

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