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  • 1.
    Ahgren, Per
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology.
    Jakobsson, Andreas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology.
    A study of doubletalk detection performance in the presence of acoustic echo path changes2006In: IEEE transactions on consumer electronics, ISSN 0098-3063, E-ISSN 1558-4127, Vol. 52, no 2, p. 515-522Article in journal (Refereed)
    Abstract [en]

    An efficient and well-performing double-talk detection (DTD) algorithm is a vital part of a practically working acoustic echo canceller. However, recent algorithms are typically evaluated using a static time-invariant room acoustic impulse response, omitting a proper treatment of the case when the acoustic path is changing. In this work, we introduce a common framework to objectively evaluate how path changes affect the DTD performance. Via extensive numerical simulations, we conclude that the main factor in acoustic path changes affecting the DTD performance for some of the more common DTD algorithms is variations in the damping of the acoustic path.

  • 2. Ahlgren, Bengt
    et al.
    Hidell, Markus
    Ngai, Edith C.-H.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Internet of Things for smart cities: Interoperability and open data2016In: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 20, no 6, p. 52-56Article in journal (Refereed)
  • 3. Alonso, Juan M.
    et al.
    Nordhamn, Amanda
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Olofsson, Simon
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Bounds on the lifetime of wireless sensor networks with lossy links and directional antennas2016In: Wireless Network Performance Enhancement via Directional Antennas: Models, Protocols, and Systems, Boca Raton, FL: CRC Press, 2016, p. 329-361Chapter in book (Refereed)
  • 4.
    Andersson, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Toft, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Data communication and power supply on a two conductor system2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis aimed to develop a prototype of a hardware platform which allowed digital communication as well as DC power to be transmitted over one pair of wires. The prototype was used as a pre-study for Axis Communications AB that wanted a bit rate high enough to transmit digital audio, as well as enough power to supply a set of speakers.

    The prototype included one circuit to send power and data (master), as well as two receivers (slaves). With this configuration data rates of up to 17 Mbps were achieved as well as an output power of 90 W from master. The data was transmitted on a RS-485 bus type, which was AC coupled to a 48 V DC bias. Because of the AC coupling, the bit stream needed to alternate, therefore Manchester encoded data, or similar, was recommended.

    The receiver cards included a buck converter to supply the circuits with a stable 5 V DC. The converters needed at least 10 V supply voltage to function, which gave a theoretical max range in cabling when accounting for voltage drop in the cables. For a 0.75 mm² power cord at max allowed current, this range was 500 metres per wire.

  • 5. Andreou, Charalambos
    et al.
    Paccagnella, A.
    González-Castaño, D.M.
    Gómez, F.
    Liberali, V.
    Prokofiev, Alexander V.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Calligaro, C.
    Javanainen, A.
    Virtanen, A.
    Nahmad, D.
    Georgiou, J.
    A Subthreshold, Low-Power, RHBD Reference Circuit, for Earth Observation and Communication Satellites2015In: Circuits and Systems (ISCAS), 2015 IEEE International Symposium on, 2015, p. 2245-2248Conference paper (Refereed)
    Abstract [en]

    A low-power, wide temperature range, radiation tolerant CMOS voltage reference is presented. The proposed reference circuit exhibits a voltage deviation of 0.8mV for 3-MeV protons total ionization dose of 2Mrad and a voltage deviation of 3.8mV for 10-keV X-rays total ionization dose of 4Mrad while being biased at the nominal supply voltage of 0.75V during X-ray irradiation. In addition, the circuit consumes only 4 mu W and exhibits a measured Temperature Drift of 15ppm/degrees C for a temperature range of 190 degrees C (-60 degrees C to 130 degrees C) at the supply voltage of 0.75V. It utilizes only CMOS transistors, operating in the subthreshold regime, and poly-silicon resistors without using any diodes or external components such as compensating capacitors. The circuit is radiation hardened by design (RHBD), it was fabricated using TowerJazz Semiconductor's 0.18 mu m standard CMOS technology and occupies a silicon area of 0.039mm(2). The proposed voltage reference is suitable for high-precision and low-power space applications.

  • 6.
    Appelgren, Filiph
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Power System Software Development: with possible SCADA System Integration2014Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order for power system operators (such as TRANSCO) to maintain and operatethe transmission grid in a safe, secure and effcient way, automatic tools such asSCADA systems is necessary to meet demand at all times. The main purpose of thisthesis was to develop a software/prototype at the load despatch centre at TRANSCOwith the ability to monitor and communicate with power plants. The software issupposed to work in a real-time electronic market. The power plant operators candeclare their availability and capability parameters of their generating and producingunits to TRANSCO and LDC operators can send load despatch instructions to thepower plants (such as load changes and other ancillary instructions). The prototypealso has a compliance monitoring application that validates unit outputs againstdespatched instructions. If the output is outside a specific interval, a transgressionwarning is sent to the power plant informing them that they should adjust their unitoutput against the target load. If further transgression is continued, the operator atLDC can re-declare the units availability on the power plants behalf and issue a newload despatch instruction to the unit. The re-declared availability level will be valid allthe way back to when the unit issued the last availability declaration.The software was successfully developed and could perform all tasks that it wassupposed to in a satisfactory way. In order to make the development as sufficient andeffective as possible, a "dummy" power plant was created and was used to simulateunit outputs and plant operator behaviour. As the time was too short, the SCADAintegration was never investigated and was left to whom is taken over after this thesishas ended.

  • 7. Arvidsson, Åke
    et al.
    Rydén, Tobias
    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.
    Load transients in pooled cellular core network nodes2015In: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 90, p. 18-35Article in journal (Refereed)
  • 8.
    Augustine, Robin
    Uppsala University.
    BAN Antenna Design Using Ferrite Polymer Composite2009Conference paper (Refereed)
  • 9.
    Augustine, Robin
    Uppsala University.
    Biocompatibility study of biphasic-chitosan-soyameal composite Bioceramic Implants and their use as Phantoms for Medical Imaging. Applications2008Conference paper (Refereed)
  • 10. Augustine, Robin
    Biocompatibility study of hydroxy apatite and chitosan composites for applications at microwave frequencies2010In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 46, no 3, p. 197-199Article in journal (Refereed)
    Abstract [en]

    Hydroxyapatite (HAp, Ca10(PO4)6(OH)2) bioceramic and chitosan (poly [(β-1-4) d-glucosamine]) biopolymer show good biocompatibility in vivo. They have biological origin and show excellent interactions with microwave. Microwave study of HAp made using different drying techniques and their composites with chitosan in the ISM band is presented. Pastes are made using HAp and chitosan with different ratios of mixing. The dielectric properties of this composites match with that of human fat, collagen tissues. Some of the compositions exhibit dielectric property close to that of natural bone. This makes them more biocompatible and better substitutes for natural bone. Thus composite bioceramics can be considered as phantom model constituents for imaging purposes. Their dielectric properties prove that they are biocompatible. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2931–2934, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23806

  • 11.
    Augustine, Robin
    Uppsala University.
    Dielectric Studies of Calcium Hydroxyapatite at Microwave Frequency2005Conference paper (Refereed)
  • 12. Augustine, Robin
    Développement d’un modèle humain dans la bande millimétrique pour les applications2011Conference paper (Refereed)
  • 13.
    Augustine, Robin
    Université Paris-Est.
    Electromagnetic modelling of human tissues and its application on the interaction between antenna and human body in the BAN context2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this age of wireless technology, Body Area networks (BAN) is revolutionising the concept of patient care and health monitoring. BAN provides people good assessment of their health status at any time, wherever they are physically. The increased interest in developing effective body (in, on & off) communication systems made phantoms which can mimic the electrical properties of an actual human body necessary. Wearable antennas which are the indispensable part of BAN got to be low pro file and above all influences that human body can make. There should also be a way to reduce the effect of antennas on human body namely specific absorption rate (SAR). In this work effort has been made to develop phantoms suitable for both On body and In body communications. The base materials which are selected for the study are of biological origin (bio ceramics and biopolymers) whose behaviour is closer to that of human tissues. As these phantoms are biocompatible they are essentially non toxic where the conventionally available phantoms are toxic in nature. Different kinds of low profile conformal wearable antennas working at 2.4GHz ISM band were developed and studied in the BAN perspective. Antennas suffer much in terms of matching and efficiency when they are in contact or in the premises of human body. This is a major hurdle in the way to setting up a good body communication network. This work encompasses various techniques adopted to limit the body interferences to an acceptable level. The techniques adopted (Such as Backing Ground Plane, High Impedance Surface & Polymeric Ferrite Sheets) proved to be effective in reducing the sway in antenna characteristics when they are mounted on body. Specific absorption rate is also brought to acceptable levels and thus avoiding the formation of hot spots due to microwave absorption. A safer and cost effective BAN can be set up using this work which will lead to a safer, mobile and healthy future.

  • 14. Augustine, Robin
    Permittivity Spectra of Biological Solutions in the Millimeter-Wave Range at Room andHuman Body Temperatures2011Conference paper (Refereed)
  • 15.
    Augustine, Robin
    Uppsala University.
    SAR reduction of wearable antennas using polymeric ferrite sheets2010Conference paper (Refereed)
  • 16.
    Augustine, Robin
    Uppsala University.
    Topology Optimization of Wideband Directive Antennas2015In: Progress in Electromagnetics Research, Vol. 2A1, no SC4, p. 636-639Article in journal (Refereed)
  • 17.
    Augustine, Robin
    Uppsala University.
    Wide Band Impedance matching For Transducers2005Conference paper (Refereed)
  • 18. Augustine, Robin
    et al.
    Thierry, Alves
    Sarrebourse, T.
    Poussot, B.
    Mathew, K. T.
    Laheurte, J. -M.
    Polymeric ferrite sheats for SAR reduction of Wearable ANtennas2010In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, no 3, p. 197-198Article in journal (Refereed)
    Abstract [en]

    Reduction of specific absorption rate (SAR) has now become a buzz word because of the growing health concerns over microwave exposure. Ferrites are found to be effective in diminishing electromagnetic influence. In this reported work, flexible polymeric ferrite sheets are characterised on the basis of their shielding efficiencies. SAR measurements are carried out with a planar wearable antenna and polymeric ferrite shielding to confirm its competence.

  • 19.
    Bagci, Ibrahim
    et al.
    Lancaster University.
    Raza, Shahid
    SICS.
    Chung, Antony
    Univ. of Lancaster.
    Roedig, Utz
    Univ. of Lancaster.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Combined Secure Storage and Communication for the Internet of Things2013In: IEEE International Conference on Sensing, Communication and Networking (IEEE SECON), 2013Conference paper (Refereed)
  • 20.
    Bastani, Saeed
    et al.
    The University of Sydney.
    Landfeldt, Björn
    Lund University.
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Gunningberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    A social node model for realising information dissemination strategies in delay tolerant networks2012In: Proceedings of the 15th ACM international conference on Modeling, analysis and simulation of wireless and mobile systems, New york: ACM Press, 2012, p. 79-88Conference paper (Refereed)
    Abstract [en]

    In Delay Tolerant Networks (DTNs) as an emerging content dissemination platform, mobile nodes opportunistically exchange content as they meet, with the intent of disseminating content among nodes that share common interests. During a meeting, nodes can exchange both content of direct interest to themselves as well as content that is of interest to a larger set of nodes that may be encountered in the future. The utility of DTN is governed by the content exchange opportunity (the amount of content that can be exchanged during a meeting) as well as the selection of content to be exchanged in order to maximise the interest nodes will have in information they are exposed to. Considering that there is a cost associated with the content exchange (e.g. battery usage, buffer occupancy or consumed transmission opportunity) the aim for nodes participating in content dissemination should be to maximise their payoff. In this paper, we contribute a generic framework for describing the characteristics of content exchange among participating nodes in a network. We incorporate a distributed information popularity measurement and the pairwise interaction of nodes modelled as a bargaining problem. The outcome of this process is the fair split up of dwelling time as a network resource and the selection of which content objects to exchange in order to maximise the nodes’ payoff. The framework is generally intended to be used as a capstone for investigation of content dissemination properties and various content exchange strategies in a DTN, a topic addressed in this paper and experiments conducted to validate the function and correctness of the proposed framework. 

  • 21.
    Berglund, Emil
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Informatics and Media.
    Facklam, Alexander
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Informatics and Media.
    Framgång eller förfall?: Utvecklingen, riskerna och potentialen av BYOD2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Uppsatsen undersöker fenomenet Bring Your Own Device (BYOD), dess för- och nackdelar samt hur riskerna BYOD medför kan hanteras. För att uppnå detta har en litteraturstudie genomförts. Denna kompletteras av en enkätstudie på Stockholms Läns Landsting och tre intervjuer på Uppsala Kommun med målet att se hur dessa organisationer hanterar BYOD. Arbetet ger en djup insikt i BYOD olika aspekter och visar även på hur de risker som uppkommer kan hanteras.

  • 22.
    Berglund, Martin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Palmer, Kristoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Lotfi, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kratz, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Dynamic characterization and modelling of a dual-axis beam steering device for performance understanding, optimization, and control design2013In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, no 4, p. 045020-Article in journal (Refereed)
    Abstract [en]

    This paper presents a lumped thermal model of a dual-axis laser micromirror device for beam steering in a free-space optical (FSO) communication system, designed for fractionated spacecraft. An FSO communication system provides several advantages, such as larger bandwidth, smaller size and weight of the communication payload and less power consumption. A dual-axis mirror device is designed and realized using microelectromechanical systems technology. The fabrication is based on a double-sided, bulk micromachining process, where the mirror actuates thermally by joints consisting of v-grooves filled with the SU-8 polymer. The size of the device, consisting of a mirror, which is deflectable versus its frame in one direction, and through deflection of the frame in the other, is 15.4 × 10.4 × 0.3 mm3. In order to further characterize and understand the micromirror device, a Simulink state-space model of the actuator is set up using thermal and mechanical properties from a realized actuator. A deviation of less than 2% between the modelled and measured devices was obtained in an actuating temperature range of 20–200 °C. The model of the physical device was examined by evaluating its performance in vacuum, and by changing physical parameters, such as thickness and material composition. By this, design parameters were evaluated for performance gain and usability. For example, the crosstalk between the two actuators deflecting the mirror along its two axes in atmospheric pressure is projected to go down from 97% to 6% when changing the frame material from silicon to silicon dioxide. A feedback control system was also designed around the model in order to examine the possibility to make a robust control system for the physical device. In conclusion, the model of the actuator presented in this paper can be used for further understanding and development of the actuator system.

  • 23.
    Bjurefors, Fredrik
    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.
    Measurements in opportunistic networks2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Opportunistic networks are a subset of delay tolerant networks where the contacts are unscheduled. Such networks can be formed ad hoc by wireless devices, such as mobile phones and laptops. In this work we use a data-centric architecture for opportunistic networks to evaluate data dissemination overhead, congestion in nodes' buffer, and the impact of transfer ordering. Dissemination brings an overhead since data is replicated to be spread in the network and overhead leads to congestion, i.e., overloaded buffers.

    We develop and implement an emulation testbed to experimentally evaluate properties of opportunistic networks. We evaluate the repeatability of experiments in the emulated testbed that is based on virtual computers. We show that the timing variations are on the order of milliseconds.

    The testbed was used to investigate overhead in data dissemination, congestion avoidance, and transfer ordering in opportunistic networks. We show that the overhead can be reduced by informing other nodes in the network about what data a node is carrying. Congestion avoidance was evaluated in terms of buffer management, since that is the available tool in an opportunistic network, to handle congestion. It was shown that replication information of data objects in the buffer yields the best results. We show that in a data-centric architecture were each data item is valued differently, transfer ordering is important to achieve delivery of the most valued data.

  • 24.
    Bjurefors, Fredrik
    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.
    Opportunistic Networking: Congestion, Transfer Ordering and Resilience2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Opportunistic networks are constructed by devices carried by people and vehicles. The devices use short range radio to communicate. Since the network is mobile and often sparse in terms of node contacts, nodes store messages in their buffers, carrying them, and forwarding them upon node encounters. This form of communication leads to a set of challenging issues that we investigate: congestion, transfer ordering, and resilience.

    Congestion occurs in opportunistic networks when a node's buffers becomes full. To be able to receive new messages, old messages have to be evicted. We show that buffer eviction strategies based on replication statistics perform better than strategies that evict messages based on the content of the message.

    We show that transfer ordering has a significant impact on the dissemination of messages during time limited contacts. We find that transfer strategies satisfying global requests yield a higher delivery ratio but a longer delay for the most requested data compared to satisfying the neighboring node's requests.

    Finally, we assess the resilience of opportunistic networks by simulating different types of attacks. Instead of enumerating all possible attack combinations, which would lead to exhaustive evaluations, we introduce a method that use heuristics to approximate the extreme outcomes an attack can have. The method yields a lower and upper bound for the evaluated metric over the different realizations of the attack. We show that some types of attacks are harder to predict the outcome of and other attacks may vary in the impact of the attack due to the properties of the attack, the forwarding protocol, and the mobility pattern.

    List of papers
    1. Haggle Testbed: a Testbed for Opportunistic Networks
    Open this publication in new window or tab >>Haggle Testbed: a Testbed for Opportunistic Networks
    2011 (English)In: In Proceedings of the 7th Swedish National Computer Networking Workshop, 2011Conference paper, Published paper (Refereed)
    Identifiers
    urn:nbn:se:uu:diva-155530 (URN)
    Projects
    Haggle
    Available from: 2011-06-23 Created: 2011-06-23 Last updated: 2014-06-30
    2. Congestion Avoidance in a Data-Centric Opportunistic Network
    Open this publication in new window or tab >>Congestion Avoidance in a Data-Centric Opportunistic Network
    2011 (English)In: Proceedings of the 2011 ACM SIGCOMM Workshop on Information-Centric Networking (ICN-2011), 2011Conference paper, Published paper (Refereed)
    Identifiers
    urn:nbn:se:uu:diva-155528 (URN)
    Projects
    ResumeNet
    Available from: 2011-06-23 Created: 2011-06-23 Last updated: 2014-06-30
    3. Making the Most of Your Contacts: Transfer Ordering in Data-Centric Opportunistic Networks
    Open this publication in new window or tab >>Making the Most of Your Contacts: Transfer Ordering in Data-Centric Opportunistic Networks
    Show others...
    2012 (English)In: Proceedings of the 2012 ACM MobiOpp Workshop on Mobile Opportunistic Networks, Zürich: ACM Press, 2012Conference paper, Published paper (Refereed)
    Abstract [en]

    Opportunistic networks use unpredictable and time-limited con- tacts to disseminate data. Therefore, it is important that protocols transfer useful data when contacts do occur. Specifically, in a data- centric network, nodes benefit from receiving data relevant to their interests. To this end, we study five strategies to select and order the data to be exchanged during a limited contact, and measure their ability to promptly and efficiently deliver highly relevant data.

    Our trace-driven experiments on an emulation testbed suggest that nodes benefit in the short-term from ordering data transfers to satisfy local interests. However, this can lead to suboptimal longterm system performance. Restricting sharing based on matching nodes’ interests can lead to segregation of the network, and limit useful dissemination of data. A non-local understanding of other nodes’ interests is necessary to effectively move data across the network. If ordering of transfers for data relevance is not explicitly considered performance is comparable to random, which limits the delivery of individually relevant data. 

    Place, publisher, year, edition, pages
    Zürich: ACM Press, 2012
    National Category
    Communication Systems
    Identifiers
    urn:nbn:se:uu:diva-171587 (URN)
    Conference
    ACM MobiOpp
    Projects
    ResumeNet
    Available from: 2012-03-22 Created: 2012-03-22 Last updated: 2014-06-30
    4. Resilience and Opportunistic Forwarding: Beyond Average Value Analysis
    Open this publication in new window or tab >>Resilience and Opportunistic Forwarding: Beyond Average Value Analysis
    Show others...
    2014 (English)In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 48, no SI, p. 111-120Article in journal (Refereed) Published
    Abstract [en]

    Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of highly heterogeneous, and not always software and hardware-compatible, user nodes. Moreover, the absence of central coordination and control makes them vulnerable to malicious attacks. In this paper, we study the resilience of popular forwarding protocols to a representative set of challenges to their normal operation. These include jamming locally disturbing message transfer between nodes, hardware/software failures and incompatibility among nodes rendering contact opportunities useless, and free-riding phenomena. We first formulate and promote the metric envelope concept as a tool for assessing the resilience of opportunistic forwarding schemes. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated challenge impact due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. We then propose heuristics to generate worst- and best-case challenge realization scenarios and approximate the lower and upper bounds of the metric envelopes. Finally, we demonstrate the methodology in assessing the resilience of three popular forwarding protocols in the presence of the three challenges, and under a comprehensive range of mobility patterns. The metric envelope approach provides better insights into the level of protection path diversity and message replication provide against different challenges, and enables more informed choices in opportunistic forwarding when network resilience becomes important.

    National Category
    Communication Systems
    Identifiers
    urn:nbn:se:uu:diva-222822 (URN)10.1016/j.comcom.2014.04.004 (DOI)000337883200010 ()
    Projects
    ResumeNet, WISENET
    Funder
    EU, FP7, Seventh Framework Programme, FP7-224619
    Note

    Special Issue

    Available from: 2014-04-17 Created: 2014-04-14 Last updated: 2017-12-05Bibliographically approved
  • 25.
    Bjurefors, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Karaliopoulos, Markourios
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Smith, Paul
    Theodoropoulos, George
    Gunningberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Resilience and Opportunistic Forwarding: Beyond Average Value Analysis2014In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 48, no SI, p. 111-120Article in journal (Refereed)
    Abstract [en]

    Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of highly heterogeneous, and not always software and hardware-compatible, user nodes. Moreover, the absence of central coordination and control makes them vulnerable to malicious attacks. In this paper, we study the resilience of popular forwarding protocols to a representative set of challenges to their normal operation. These include jamming locally disturbing message transfer between nodes, hardware/software failures and incompatibility among nodes rendering contact opportunities useless, and free-riding phenomena. We first formulate and promote the metric envelope concept as a tool for assessing the resilience of opportunistic forwarding schemes. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated challenge impact due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. We then propose heuristics to generate worst- and best-case challenge realization scenarios and approximate the lower and upper bounds of the metric envelopes. Finally, we demonstrate the methodology in assessing the resilience of three popular forwarding protocols in the presence of the three challenges, and under a comprehensive range of mobility patterns. The metric envelope approach provides better insights into the level of protection path diversity and message replication provide against different challenges, and enables more informed choices in opportunistic forwarding when network resilience becomes important.

  • 26.
    Bjurefors, Fredrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Karaliopoulos, Merkourios
    Rohner, Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Smith, Paul
    Theodoropoulos, George
    Gunningberg, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Resilience and Opportunistic Forwarding: Beyond Average Value Analysis2013In: CHANTS '13 Proceedings of the 8th ACM MobiCom workshop on Challenged networks, 2013Conference paper (Refereed)
    Abstract [en]

    Opportunistic networks are systems with highly distributed operation, relying on the altruistic cooperation of heterogeneous, and not always software- and hardware-compatible user nodes. Moreover, the absence of central control makes them vulnerable to malicious attacks. In this paper, we take a fresh look at the resilience of opportunistic forwarding to these challenges. In particular, we introduce and promote the use of metric envelopes as a resilience assessment tool. Metric envelopes depart from the standard practice of average value analysis and explicitly account for the differentiated impact that a challenge may have on the forwarding performance due to node heterogeneity (device capabilities, mobility) and attackers’ intelligence. The use of metric envelopes is demonstrated in the case of three challenges: jamming, hardware/software failures and incompatibilities, and free-riding phenomena. For each challenge, we first devise heuristics to generate worst- and best-case realization scenarios that can approximate the metric envelopes. Then we derive the envelopes of common performance metrics for three popular forwarding protocols under a comprehensive range of mobility patterns. The metric envelope approach enables more informed choices in opportunistic forwarding whenever network resilience considerations become important. 

  • 27. Boano, Carlo Alberto
    et al.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Noda, Claro
    Römer, Kay
    Zuniga, Marco
    JamLab: Augmenting sensornet testbeds with realistic and controlled interference generation2011In: IPSN, 2011, p. 175-186Conference paper (Refereed)
  • 28.
    Boano, Carlo Alberto
    et al.
    University of Lübeck.
    Wennerström, Hjalmar
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Zúñiga, Marco Antonio
    TU Delft.
    Brown, James
    Lancaster University.
    Keppitiyagama, Chamath
    Swedish Institute of Computer Science.
    Oppermann, Felix Jonathan
    University of Lübeck.
    Roedig, Utz
    Lancaster University.
    Nordén, Lars-Åke
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Römer, Kay
    University of Lübeck.
    Hot Packets: A systematic evaluation of the effect of temperature on low power wireless transceivers2013In: Proc. 5th Extreme Conference on Communication, New York: ACM Press, 2013, p. 7-12Conference paper (Refereed)
    Abstract [en]

    Temperature is known to have a significant effect on the performance of radio transceivers: the higher the temperature, the lower the quality of links. Analysing this effect is particularly important in sensor networks because several applications are exposed to harsh environmental conditions. Daily or hourly changes in temperature can dramatically reduce the throughput, increase the delay, or even lead to network partitions. A few studies have quantified the impact of temperature on low-power wireless links, but only for a limited temperature range and on a single radio transceiver. Building on top of these preliminary observations, we design a low-cost experimental infrastructure to vary the onboard temperature of sensor nodes in a repeatable fashion, and we study systematically the impact of temperature on various sensornet platforms. We show that temperature affects transmitting and receiving nodes differently, and that all platforms follow a similar trend that can be captured in a simple first-order model. This work represents an initial stepping stone aimed at predicting the performance of a network considering the particular temperature profile of a given environment.

  • 29.
    Borgh, Joakim
    et al.
    Ericsson Res, Stockholm, Sweden.
    Ngai, Edith
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Ohlman, Börje
    Ericsson Res, Stockholm, Sweden.
    Malik, Adeel Mohammad
    Ericsson Res, Stockholm, Sweden.
    Employing attribute-based encryption in systems with resource constrained devices in an information-centric networking context2017In: 2017 Global Internet of Things Summit (GIoTS), IEEE, 2017, p. 397-402Conference paper (Other academic)
    Abstract [en]

    Attribute-Based Encryption (ABE) is considered to be one of the most promising ways to be enforce access control in Information-Centric Networking (ICN). As the Internet of Things (IoT) is being considered as one of the primary use cases for ICN it raises the question of the compatibility between IoT and ABE. An important part of the IoT is the resource constrained devices, for them there is a challenge to perform the computationally expensive operations required for ABE. In this paper we consider ABE in sensor networks and discuss the strengths and weaknesses of a system solution where the ABE operations are performed on the sensors. To properly discuss these concerns we have implemented two ABE schemes, a Single-authority ABE (SA-CP-ABE) scheme and a Multi-authority ABE (MA-CP-ABE) scheme. Results regarding the execution time, RAM usage, data overhead and battery consumption of these implementations on a sensor are presented. We conclude that it is possible, already today, to perform ABE on sensors for smaller policies. The main limitation in deploying ABE in sensors is the RAM size of the sensors.

  • 30.
    Bratel, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Bernestrå, Christopher
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Industrial Engineering & Management.
    Internet of Things i Hyresfastigheter: Förutsättningar för implementering av ny teknik2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this report is to review the current conditions exsisting for the implementation of Internet of Things in apartment buildings and how insight can be accomplished for these conditions in real estate companies. Internet of Things is a technology which has increased in popularity in later years and builds on objects connecting to each other or the internet. In conjunction with the reduction of implementation costs for the technology and the increase of possible applications, an interest has grown in many different business sectors. This study concerns the real estate company FinaHem, where the conditions for measurement of different values using connected sensors is analyzed. To answer the formulated questions regarding technological efficiency, financial factors and how a potential solution using Internet of Things would be recieved by tenants, this paper is designed as a case study. The case study evaluates the operations of FinaHem and utilizes both qualitative and quantitative methods, as well as a business case method. The result and the analysis from the study indicates important factors for the company’s conditions to implement Internet of Things. Technological solutions regarding energy savings, detections of water damage, and visualisation has exhibited business value. Furthermore, the importance of evaluating opinions from residents, and creating a positive experience for them, is established.

  • 31. Brown, J.
    et al.
    Roedig, U.
    O'Donovan, T.
    Sreenan, C. J.
    He, Z.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Pottner, B.
    Wolf, L.
    Klein, A.
    Silva, J. Sa
    Vassiliou, V.
    doO, J.
    GINSENG: Performance Control in Wireless Sensor Networks2011In: 8th European Conference on Wireless Sensor Networks (EWSN’11), 2011Conference paper (Refereed)
  • 32. Brown, James
    et al.
    McCarthy, Ben
    Roedig, Utz
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Sreenan, Cormac J.
    BurstProbe: Debugging Time-Critical Data Delivery in Wireless Sensor Networks2011In: 8th European Conference on Wireless Sensor Networks (EWSN’11), 2011Conference paper (Refereed)
  • 33.
    Cambazoglu, Volkan
    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.
    Protocol, mobility and adversary models for the verification of security2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increasing heterogeneity of communicating devices, ranging from resource constrained battery driven sensor nodes to multi-core processor computers, challenges protocol design. We examine security and privacy protocols with respect to exterior factors such as users, adversaries, and computing and communication resources; and also interior factors such as the operations, the interactions and the parameters of a protocol.

    Users and adversaries interact with security and privacy protocols, and even affect the outcome of the protocols. We propose user mobility and adversary models to examine how the location privacy of users is affected when they move relative to each other in specific patterns while adversaries with varying strengths try to identify the users based on their historical locations. The location privacy of the users are simulated with the support of the K-Anonymity protection mechanism, the Distortion-based metric, and our models of users' mobility patterns and adversaries' knowledge about users.

    Security and privacy protocols need to operate on various computing and communication resources. Some of these protocols can be adjusted for different situations by changing parameters. A common example is to use longer secret keys in encryption for stronger security. We experiment with the trade-off between the security and the performance of the Fiat–Shamir identification protocol. We pipeline the protocol to increase its utilisation as the communication delay outweighs the computation.

    A mathematical specification based on a formal method leads to a strong proof of security. We use three formal languages with their tool supports in order to model and verify the Secure Hierarchical In-Network Aggregation (SHIA) protocol for Wireless Sensor Networks (WSNs). The three formal languages specialise on cryptographic operations, distributed systems and mobile processes. Finding an appropriate level of abstraction to represent the essential features of the protocol in three formal languages was central.

    List of papers
    1. The impact of trace and adversary models on location privacy provided by K-anonymity
    Open this publication in new window or tab >>The impact of trace and adversary models on location privacy provided by K-anonymity
    2012 (English)In: Proc. 1st Workshop on Measurement, Privacy, and Mobility, New York: ACM Press, 2012, article id 6Conference paper, Published paper (Refereed)
    Place, publisher, year, edition, pages
    New York: ACM Press, 2012
    National Category
    Computer Sciences
    Research subject
    Computer Science with specialization in Computer Communication
    Identifiers
    urn:nbn:se:uu:diva-171581 (URN)10.1145/2181196.2181202 (DOI)978-1-4503-1163-2 (ISBN)
    Conference
    MPM 2012
    Projects
    ProFuNWISENET
    Available from: 2012-04-10 Created: 2012-03-22 Last updated: 2018-01-12Bibliographically approved
    2. Towards adaptive zero-knowledge protocols: A case study with Fiat–Shamir identification protocol
    Open this publication in new window or tab >>Towards adaptive zero-knowledge protocols: A case study with Fiat–Shamir identification protocol
    2013 (English)In: Proc. 9th Swedish National Computer Networking Workshop, 2013, p. 67-70Conference paper, Published paper (Refereed)
    Abstract [en]

    Interactive zero-knowledge protocols are used as identification protocols. The protocols are executed in rounds, with security being increased with every round. This allows for a trade-off between security and performance to adapt the protocol to the requirements of the scenario. We experimentally investigate the Fiat–Shamir identification protocol on machines and networks with different performance characteristics. We find that the delay of the protocol highly depends on network latency and upload bandwidth. Computation time becomes more visible, when the protocol transmits little amount of data via a low latency network. We also experience that the impact of the sizes of the variables on the delay of the protocol is less than the number of rounds', which are interior factors in the protocol.

    National Category
    Computer Sciences
    Research subject
    Computer Science with specialization in Computer Communication
    Identifiers
    urn:nbn:se:uu:diva-201070 (URN)
    Conference
    SNCNW 2013
    Projects
    WISENETProFuN
    Available from: 2013-06-05 Created: 2013-06-05 Last updated: 2018-01-11Bibliographically approved
    3. Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support
    Open this publication in new window or tab >>Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support
    2015 (English)Report (Other academic)
    Series
    Technical report / Department of Information Technology, Uppsala University, ISSN 1404-3203 ; 2015-033
    National Category
    Computer Sciences Communication Systems
    Research subject
    Computer Science with specialization in Computer Communication
    Identifiers
    urn:nbn:se:uu:diva-268453 (URN)
    Projects
    ProFuN
    Funder
    Swedish Foundation for Strategic Research , RIT08-0065
    Available from: 2015-12-03 Created: 2015-12-04 Last updated: 2018-01-10Bibliographically approved
  • 34.
    Cambazoglu, Volkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Gutkovas, Ramunas
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Åman Pohjola, Johannes
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Victor, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support2015Report (Other academic)
  • 35.
    Carlos, Perez Penichet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Varshney, Ambuj
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Augmenting IoT networks with backscatter-enabled passive sensor tags2016In: Proceedings of the 3rd Workshop on Hot Topics in Wireless, 2016, p. 23-27Conference paper (Refereed)
    Abstract [en]

    The sensing modalities available in an Internet-of-Things (IoT) network are usually fixed before deployment, when the operator selects a suitable IoT platform. Retrofitting a deployment with additional sensors can be cumbersome, because it requires either modifying the deployed hardware or adding new devices that then have to be maintained. In this paper, we present our vision and work towards passive sensor tags: battery-free devices that allow to augment existing IoT deployments with additional sensing capabilities without the need to modify the existing deployment. Our passive sensor tags use backscatter transmissions to communicate with the deployed network. Crucially, they do this in a way that is compatible with the deployed network's radio protocol, and without the need for additional infrastructure. We present an FPGA-based prototype of a passive sensor tag that can communicate with unmodified 802.15.4 IoT devices. Our initial experiments with the prototype support the feasibility of our approach. We also lay out the next steps towards fully realizing the vision of passive sensor tags.

  • 36.
    Carlos, Pérez Penichet
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Hermans, Frederik
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Architecture and Computer Communication.
    On Limits of Constructive Interference in Backscatter Systems2017In: Global Internet of Things Summit (GIoTS), 2017, IEEE, 2017, p. 178-182Conference paper (Other academic)
    Abstract [en]

    Backscatter communication reduces the energy consumption of resource-constrained sensors and actuators by several orders of magnitude as it avoids the resource-consuming need to generate a radio wave. Many backscatter systems and applications suffer from low communication range. By exploiting the collective power of several tags that transmit the same data simultaneously, constructive interference may help to remedy this problem and increase the communication range. When several tags backscatter the same signal simultaneously it is not necessarily true that constructive interference occurs. As our theoretical results and previous work indicate the interference might also be destructive. Our experimental results on real hardware suggest that exploiting constructive interference to increase the communication range requires careful coordination which is difficult in decentralized settings.

  • 37. Casati, Fabio
    et al.
    Daniel, Florian
    Dantchev, Guenadi
    Eriksson, Joakim
    Finne, Niclas
    Karnouskos, Stamatis
    Montera, Patricio Moreno
    Mottola, Luca
    Oppermann, Felix Jonathan
    Picco, Gian Pietro
    Quartulli, Antonio
    Römer, Kay
    Spiess, Patrik
    Tranquillini, Stefano
    Voigt, Thiemo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Towards business processes orchestrating the physical enterprise with wireless sensor networks2012In: ICSE, 2012, p. 1357-1360Conference paper (Refereed)
  • 38. Cea, Mauricio G.
    et al.
    Goodwin, Graham C.
    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.
    Model predictive zooming power control in future cellular systems under coarse quantization2012In: Proc. 76th Vehicular Technology Conference, Piscataway, NJ: IEEE, 2012Conference paper (Refereed)
  • 39.
    Charalambous, Themistoklis
    et al.
    Aalto Univ, Sch Elect Engn, Dept Elect Engn & Automat, Espoo, Finland..
    Özcelikkale, Ayca
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Signals and Systems Group.
    Zanon, Mario
    Chalmers Univ Technol, Dept Signals & Syst, Gothenburg, Sweden..
    Falcone, Paolo
    Chalmers Univ Technol, Dept Signals & Syst, Gothenburg, Sweden..
    Wymeersch, Henk
    Chalmers Univ Technol, Dept Signals & Syst, Gothenburg, Sweden..
    On the Resource Allocation Problem in Wireless Networked Control Systems2017In: 2017 IEEE 56Th Annual Conference On Decision And Control (Cdc), IEEE, 2017, p. 4147-4154Conference paper (Refereed)
    Abstract [en]

    This paper considers the scheduling problem of a decentralized system where a number of dynamical subsystems with no computational power are scheduled to transmit their measurements via a resource-limited communication network to a remote decision maker who acts as an estimator, controller and scheduler for the subsystems. We propose a new approach for communication resource allocation for a wide class of objective functions, for both coupled and decoupled systems, and for both scheduling observations as well as control commands. This framework facilitates scheduling over a finite horizon and can explicitly deal with stochastic channels. For decoupled subsystems, we propose the notion of cost of information loss (CoIL) and we demonstrate that the communications resource allocation problem can be directly expressed in terms of CoIL functions as an assignment-type optimization problem. Illustrative examples demonstrate how communication resources affect the performance of the system.

  • 40.
    Cooray, Vernon
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Fernando, M.
    Univ Colombo, Dept Phys, Colombo 03, Sri Lanka.
    Gunasekara, L.
    Univ Colombo, Dept Phys, Colombo 03, Sri Lanka.
    Nanayakkara, S.
    Univ Colombo, Dept Phys, Colombo 03, Sri Lanka.
    Effects of Propagation of Narrow Bipolar Pulses, Generated by Compact Cloud Discharges, over Finitely Conducting Ground2018In: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 9, no 5, article id 193Article in journal (Refereed)
    Abstract [en]

    Propagation effects on the narrow bipolar pulses (NBPs) or the radiation fields generated by compact cloud discharges as they propagate over finitely conducting ground are presented. The results were obtained using a sample of NBPs recorded with high time resolution from close thunderstorms in Sri Lanka. The results show that the peak amplitude and the temporal features such as the full width at half maximum (FWHM), zero-crossing time, and the time derivative of NBPs can be significantly distorted by propagation effects. For this reason, the study of peak amplitudes and temporal features of NBPs and the remote sensing of current parameters of compact cloud discharges should be conducted using NBPs recorded under conditions where the propagation effects are minimal.

  • 41. Crovella, Mark
    et al.
    Feeney, Laura MarieUppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.Rubenstein, DanRaghavan, S. V.
    NETWORKING 20102010Conference proceedings (editor) (Other academic)
  • 42.
    Dancila, Dragos
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Monolithically Integrated RF-MEMS Actuated Patch-Slot Element for X-Band Reconfigurable Reflectarrays2013Conference paper (Refereed)
  • 43.
    Dancila, Dragos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Cavallo, Daniele
    Lager, Ioan E.
    Neto, Andrea
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Analytical model for patch-slot elements of reconfigurable reflectarray2014Conference paper (Refereed)
  • 44.
    Dancila, Dragos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics.
    Hoang Duc, Long
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jobs, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Holmberg, Måns
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Hjort, Adam
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ruber, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, High Energy Physics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    A compact 10 kW solid-state RF power amplifier at 352 MHz2017Conference paper (Refereed)
  • 45.
    Dancila, Dragos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rottenberg, X.
    Tilmans, H.A.C.
    De Raedt, W.
    Huynen, I.
    Rydberg, A.
    High-Q parallel plate resonator for V-band in MCM-D technology2012Conference paper (Refereed)
  • 46.
    Dancila, Dragos
    et al.
    Catholic Univ Louvain, ICTEAM Div, B-1348 Louvain, Belgium.
    Rottenberg, Xavier
    IMEC, B-3001 Leuven, Belgium.
    Tilmans, Harriet A C
    IMEC, B-3001 Leuven, Belgium.
    De Raedt, Walter
    IMEC, B-3001 Leuven, Belgium.
    Huynen, Isabelle
    Catholic Univ Louvain, ICTEAM Div, B-1348 Louvain, Belgium.
    Low Phase Noise Oscillator at 60 GHz Stabilized bya Substrate Integrated Cavity Resonator in LTCC2014In: IEEE Microwave and Wireless Components Letters, ISSN 1531-1309, E-ISSN 1558-1764, Vol. 24, no 12, p. 887-889Article in journal (Refereed)
    Abstract [en]

    In this letter, we report a low phase noise oscillatorexhibiting state-of-the-art phase noise characteristics at 60 GHz.The oscillator is stabilized by an off-chip substrate integratedwaveguide (SIW) cavity resonator, manufactured in LTCC technology.The area on top of the cavity resonator is used to flip-chipmount the MMIC, realized in SiGe technology. Measured oscillatorsdiscussed in this paper operate at frequencies of 59.91,59.97, and 59.98 GHz. The measured phase noise at 1 MHzoffset is 115.76 dBc/Hz, 115.92 dBc/Hz and 116.41 dBc/Hz,respectively. To our knowledge, the present hybrid oscillator hasthe lowest phase noise and highest figure of merit of integratedoscillators at V-band. The simulations are in very good agreementwith the measured oscillation frequencies.

  • 47.
    Dancila, Dragos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Valenta, Vaclav
    European Space Agcy, Noordwijk, Netherlands.
    Bunea, Alina-Cristina
    Univ Politehn Bucuresti, Bucharest, Romania.
    Dan, Neculoiu
    Natl Inst R&D Microtechnol IMT, Bucharest, Romania.; Univ Politehn Bucuresti, Bucharest, Romania.
    Schumacher, Hermann
    Natl Inst R&D Microtechnol IMT, Bucharest, Romania.; Univ Ulm, Inst Elect Devices & Circuits, Ulm, Germany.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Differential Microstrip Patch Antenna as Feeder of a Hyper-Hemispherical Lens for F-Band MIMO Radars2016In: 2016 GLOBAL SYMPOSIUM ON MILLIMETER WAVES (GSMM) & ESA WORKSHOP ON MILLIMETRE-WAVE TECHNOLOGY AND APPLICATIONS, 2016, p. 103-106Conference paper (Refereed)
    Abstract [en]

    In this paper, a novel differential microstrip patch antenna (DMPA) is designed and used to feed a lens antenna for short range F-band MIMO radars. The DMPA is fed differentially by a pair of coupled lines. The antenna is connected via a differential impedance matching network to the differential output of the modules, eliminating this way the need of a balun in the RF frontend. The simulated antenna gain is about 8 dBi and bandwidth (S11 < -10 dB) is between 125 - 137 GHz. Preliminary experimental measurements are shown using Transmit/Receive modules in 0.13 μm SiGe:C BiCMOS technology, hybrid connected using wirebonding to off chip DMPAs. It is shown by the transmission link evaluation that the gain is increased by about 15 dBi adding a 10 mm radius 3D printed polyamide lens in the near field of the DMPA.

  • 48. Delgado, Ramón A.
    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.
    Lau, Katrina
    Middleton, Richard H.
    Stability properties of a MIMO data flow controller2017Report (Other academic)
  • 49.
    Deng, Tao
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu, Sichuan, Peoples R China.
    Ahani, Ghafour
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Fan, Pingzhi
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu, Sichuan, Peoples R China.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Cost-Optimal Caching for D2D Networks With User Mobility: Modeling, Analysis, and Computational Approaches2018In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 5, p. 3082-3094Article in journal (Refereed)
    Abstract [en]

    Caching popular files at the user equipments (UEs) provides an effective way to alleviate the burden of the backhaul networks. Generally, popularity-based caching is not a system-wide optimal strategy, especially for user mobility scenarios. Motivated by this observation, we consider optimal caching with the presence of mobility. A cost-optimal caching problem (COCP) for device-to-device (D2D) networks is modeled, in which the impact of user mobility, cache size, and total number of encoded segments are all taken into account. The hardness of the problem is proved via a reduction from the satisfiability problem. Next, a lower-bounding function of the objective function is derived. By the function, an approximation of COCP (ACOCP) achieving linearization is obtained, which features two advantages. First, the ACOCP approach can use an off-the-shelf integer linear programming algorithm to obtain the global optimal solution, and it can effectively deliver solutions for small-scale and medium-scale system scenarios. Second, and more importantly, based on the ACOCP approach, one can derive a lower bound of global optimum of COCP, thus enabling performance benchmarking of any sub-optimal algorithm. To tackle large scenarios with low complexity, we first prove that the optimal caching placement of one user, giving other users' caching placements, can be derived in polynomial time. Then, based on this proof, a mobility aware multi-user algorithm is developed. Simulation results verify the effectivenesses of the two approaches by comparing them to the lower bound of global optimum and conventional caching algorithms.

  • 50.
    Deng, Tao
    et al.
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China.
    You, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Fan, Pingzhi
    Southwest Jiaotong Univ, Sch Informat Sci & Technol, Chengdu 610031, Sichuan, Peoples R China.
    Yuan, Di
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computing Science.
    Device Caching for Network Offloading: Delay Minimization With Presence of User Mobility2018In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 7, no 4, p. 558-561Article in journal (Refereed)
    Abstract [en]

    A delay-optimal caching problem in device-to-device networks with mobility is modeled. The problem arises in the context of offloading using device caching, and the offloading effect is represented by the expected network load ratio (NLR) which is the percentage of data that has to be downloaded from the network. Compared with the related studies, this letter considers minimizing delay with NLR guarantee in mobility scenarios. A lower bound of global optimum is derived, thus enabling performance benchmarking of any sub-optimal algorithm. For problem-solving, an effective search algorithm (ESA) is proposed based on the bound. Simulations are conducted to evaluate the effectiveness of the ESA algorithm.

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