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  • 1.
    Ahgren, Per
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Jakobsson, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    A study of doubletalk detection performance in the presence of acoustic echo path changes2006Ingår i: IEEE transactions on consumer electronics, ISSN 0098-3063, E-ISSN 1558-4127, Vol. 52, nr 2, s. 515-522Artikel i tidskrift (Refereegranskat)
    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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Internet of Things for smart cities: Interoperability and open data2016Ingår i: IEEE Internet Computing, ISSN 1089-7801, E-ISSN 1941-0131, Vol. 20, nr 6, s. 52-56Artikel i tidskrift (Refereegranskat)
  • 3. Alonso, Juan M.
    et al.
    Nordhamn, Amanda
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Olofsson, Simon
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Bounds on the lifetime of wireless sensor networks with lossy links and directional antennas2016Ingår i: Wireless Network Performance Enhancement via Directional Antennas: Models, Protocols, and Systems, Boca Raton, FL: CRC Press, 2016, s. 329-361Kapitel i bok, del av antologi (Refereegranskat)
  • 4. Andersson, Hjalmar
    et al.
    Zdansky Cottle, Leo
    Claesson, Melker
    Karlsson, Nils
    Stenhammar, Oscar
    Insamling av drift- och produktionsdata från energiteknik vid Ihus anläggning på Vaksala-Eke2019Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    För att minska den globala uppvärmningen bär utbyggnaden av förnybar energiproduktion en stor vikt i dagens samhälle. Av den anledningen är det av stor betydelse som nya tekniker för energiproduktion testas. För att undersöka huruvida dessa tekniker är effektiva och lönsamma är det viktigt att deras produktionsdata publiceras och görs tillgänglig för allmänheten. Det är anledningen till att det här projektet beställts från Ihus via STUNS energi.

    Projektidén var att samla in högfrekvent uppmätt produktionsdata från en soltracker, ett vindkraftverk och ett batterilager. Dessutom skulle väderdata samlas från en väderstation och solinstrålningsmätare för att sedan offentliggöra datan via STUNS Energiportal.

    För genomförandet av projektet användes en enklare dator för att ta emot information från olika sensorer. För att kommunicera med enheterna användes olika standardiserade kommunikationsprotokoll. Enheterna konfigurerades och kopplades in i datorn. Den insamlade datan bearbetades med en programmerad kod. Programmet sände iväg datan till en molnlagringsplattform för att sedan publicera den.

    Uppkoppling mot soltrackerns växelriktare samt pyranometern lyckades. Den insamlade informationen från de två enheterna publicerades sedan på Energiportalen. Väderstationen producerade data men kommunikation med det ursprungligt tänkta protokollet lyckades inte att upprättas. Genom ett annat protokoll erhölls värden, men inte genom den implementerade koden. Dessutom uppstod problem med batterilagret och vindkraftverket. Ingen information lyckades hämtas från någon av dem.

    I projektets gång har det samlats in mätpunkter var femte sekund för respektive enhet. Utifrån det erhållna resultatet kan de konstateras att vid högfrekvent insamling av väder- och produktionsdata, blir viktig information tydligare för vardera energiproduktionsenhet. Denna information kan gå förlorad vid lågfrekvent datainsamling. Det beror på vädrets hastiga fluktuation. En lågfrekventare datainsamling ger således en sämre uppfattning av hur värdena egentligen ändras med tiden.

  • 5.
    Andersson, Tobias
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Toft, Jonathan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Data communication and power supply on a two conductor system2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 6. Andreou, Charalambos
    et al.
    Paccagnella, A.
    González-Castaño, D.M.
    Gómez, F.
    Liberali, V.
    Prokofiev, Alexander V.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Tillämpad kärnfysik.
    Calligaro, C.
    Javanainen, A.
    Virtanen, A.
    Nahmad, D.
    Georgiou, J.
    A Subthreshold, Low-Power, RHBD Reference Circuit, for Earth Observation and Communication Satellites2015Ingår i: Circuits and Systems (ISCAS), 2015 IEEE International Symposium on, 2015, s. 2245-2248Konferensbidrag (Refereegranskat)
    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.

  • 7.
    Apelfröjd, Rikke
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Zirwas, Wolfgang
    Nokia Bell Labs, D-81541 Munich, Germany.
    Sternad, Mikael
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Low-Overhead Cyclic Reference Signals for Channel Estimation in FDD Massive MIMO2019Ingår i: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 67, nr 5, s. 3279-3291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Massive multiple input multiple output (MIMO) transmission and coordinated multipoint transmission are candidate technologies for increasing data throughput in evolving 5G standards. Frequency division duplex (FDD) is likely to remain predominant in large parts of the spectrum below 6 GHz for future 5G systems. Therefore, it is important to estimate the downlink FDD channels from a very large number of antennas, while avoiding an excessive downlink reference signal overhead. We here propose and investigate a three part solution. First, massive MIMO downlinks use a fixed grid of beams. For each user, only a subset of beams will then be relevant, and require estimation. Second, sets of coded reference signal sequences, with cyclic patterns over time, are used. Third, each terminal estimates its most relevant channels. We here propose and compare a linear mean square estimation and a Kalman estimation. Both utilize frequency and antenna correlation, and the later also utilizes temporal correlation. In extensive simulations, this scheme provides channel estimates that lead to an insignificant beamforming performance degradation as compared to full channel knowledge. The cyclic pattern of coded reference signals is found to be important for reliable channel estimation, without having to adjust the reference signals to specific users.

  • 8.
    Appelgren, Filiph
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    Power System Software Development: with possible SCADA System Integration2014Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 9. Arvidsson, Åke
    et al.
    Rydén, Tobias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Load transients in pooled cellular core network nodes2015Ingår i: Performance evaluation (Print), ISSN 0166-5316, E-ISSN 1872-745X, Vol. 90, s. 18-35Artikel i tidskrift (Refereegranskat)
  • 10.
    Asan, Noor Badariah
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Hassan, Emadeldeen
    Umea Univ, Dept Comp Sci, S-90187 Umea, Sweden;Menoufia Univ, Dept Elect & Elect Commun, Menoufia 32952, Egypt.
    Velander, Jacob
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Redzwan, Syaiful
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Noreland, Daniel
    Umea Univ, Dept Comp Sci, S-90187 Umea, Sweden.
    Blokhuis, Taco J.
    Maastricht Univ, Med Ctr, Dept Surg, NL-6229 HX Maastricht, Netherlands.
    Wadbro, Eddie
    Umea Univ, Dept Comp Sci, S-90187 Umea, Sweden.
    Berggren, Martin
    Umea Univ, Dept Comp Sci, S-90187 Umea, Sweden.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Augustine, Robin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Characterization of the Fat Channel for Intra-Body Communication at R-Band Frequencies2018Ingår i: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, nr 9, artikel-id 2752Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7-2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of similar to 0.7 dB and similar to 1.9 dB per cm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.

  • 11.
    Augustine, Robin
    Uppsala University.
    BAN Antenna Design Using Ferrite Polymer Composite2009Konferensbidrag (Refereegranskat)
  • 12.
    Augustine, Robin
    Uppsala University.
    Biocompatibility study of biphasic-chitosan-soyameal composite Bioceramic Implants and their use as Phantoms for Medical Imaging. Applications2008Konferensbidrag (Refereegranskat)
  • 13. Augustine, Robin
    Biocompatibility study of hydroxy apatite and chitosan composites for applications at microwave frequencies2010Ingår i: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 46, nr 3, s. 197-199Artikel i tidskrift (Refereegranskat)
    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

  • 14.
    Augustine, Robin
    Uppsala University.
    Dielectric Studies of Calcium Hydroxyapatite at Microwave Frequency2005Konferensbidrag (Refereegranskat)
  • 15. Augustine, Robin
    Développement d’un modèle humain dans la bande millimétrique pour les applications2011Konferensbidrag (Refereegranskat)
  • 16.
    Augustine, Robin
    Université Paris-Est.
    Electromagnetic modelling of human tissues and its application on the interaction between antenna and human body in the BAN context2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 17. Augustine, Robin
    Permittivity Spectra of Biological Solutions in the Millimeter-Wave Range at Room andHuman Body Temperatures2011Konferensbidrag (Refereegranskat)
  • 18.
    Augustine, Robin
    Uppsala University.
    SAR reduction of wearable antennas using polymeric ferrite sheets2010Konferensbidrag (Refereegranskat)
  • 19.
    Augustine, Robin
    Uppsala University.
    Topology Optimization of Wideband Directive Antennas2015Ingår i: Progress in Electromagnetics Research, Vol. 2A1, nr SC4, s. 636-639Artikel i tidskrift (Refereegranskat)
  • 20.
    Augustine, Robin
    Uppsala University.
    Wide Band Impedance matching For Transducers2005Konferensbidrag (Refereegranskat)
  • 21. Augustine, Robin
    et al.
    Thierry, Alves
    Sarrebourse, T.
    Poussot, B.
    Mathew, K. T.
    Laheurte, J. -M.
    Polymeric ferrite sheats for SAR reduction of Wearable ANtennas2010Ingår i: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 46, nr 3, s. 197-198Artikel i tidskrift (Refereegranskat)
    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.

  • 22.
    Aziz, Imran
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Dahlback, Robin
    Sivers IMA, S-16440 Kista, Sweden.
    Öjefors, Erik
    Sivers IMA, S-16440 Kista, Sweden.
    Sjogren, Kristoffer
    Sivers IMA, S-16440 Kista, Sweden.
    Rydberg, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Dancila, Dragos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    60 GHz compact broadband antenna arrays with wide-angle beam steering2019Ingår i: The Journal of Engineering, ISSN 1872-3284, E-ISSN 2051-3305, nr 8, s. 5407-5414Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Highly integrated multilayered printed circuit board-based patch antenna arrays are proposed in this study for 60 GHz wireless communications. Electromagnetic coupling between two stacked patches is used to achieve the broadband performance. Different structures of single element antennas, two-element antenna arrays and four-element antenna arrays are presented. The two compact four-element antenna arrays show < -10 dB impedance bandwidth of 13 and 14.6% with 12 dBi peak gain. The arrays have the 3 dB gain bandwidth of 9 and 13%. A single column, four-element sub-array is used to design 4 x 16 antenna array. This array delivers 20.8 dBi peak gain with 13% impedance and gain bandwidth. Furthermore, a two-element series fed array is used to realise a 2 x 16 phased antenna array. This array is fed through a 16 x channel radio frequency IC to achieve the beam steering in +/- 50 degrees range.

  • 23.
    Babaheidarian, Parisa
    et al.
    Boston Univ, Boston, MA 02215 USA.
    Salimi, Somayeh
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Papadimitratos, Panos
    KTH Royal Inst Technol, Stockholm, Sweden.
    Preserving Confidentiality in The Gaussian Broadcast Channel Using Compute-and-Forward2017Ingår i: 2017 51st Annual Conference on Information Sciences and Systems (CISS), IEEE, 2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    We study the transmission of confidential messages across a wireless broadcast channel with K > 2 receivers and K helpers. The goal is to transmit all messages reliably to their intended receivers while keeping them confidential from the unintended receivers. We design a codebook based on nested lattice structure, cooperative jamming, lattice alignment, and i.i.d. coding. Moreover, we exploit the asymmetric compute-and-forward decoding strategy to handle finite SNR regimes. Unlike previous alignment schemes, our achievable rates are attainable at any finite SNR value. Also, we show that our scheme achieves the optimal sum secure degrees of freedom of 1 for the K-receiver Gaussian broadcast channel with K confidential messages and K helpers.

  • 24. Bag, Gargi
    et al.
    Johansson, Morgan
    Lednicki, Luka
    Neander, Jonas
    Eriksson, Linus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Bogati, Rajendra
    Hovila, Petri
    Saarinen, Juha
    Torsner, Johan
    Performance evaluation of IEC 61850-90-5 over a latency optimized 3GPP LTE network2018Ingår i: Proc. 9th International Conference on Smart Grid Communications, IEEE, 2018Konferensbidrag (Refereegranskat)
  • 25.
    Bagci, Ibrahim
    et al.
    Lancaster University.
    Raza, Shahid
    SICS.
    Chung, Antony
    Univ. of Lancaster.
    Roedig, Utz
    Univ. of Lancaster.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Combined Secure Storage and Communication for the Internet of Things2013Ingår i: IEEE International Conference on Sensing, Communication and Networking (IEEE SECON), 2013Konferensbidrag (Refereegranskat)
  • 26.
    Bastani, Saeed
    et al.
    The University of Sydney.
    Landfeldt, Björn
    Lund University.
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    A social node model for realising information dissemination strategies in delay tolerant networks2012Ingår i: Proceedings of the 15th ACM international conference on Modeling, analysis and simulation of wireless and mobile systems, New york: ACM Press, 2012, s. 79-88Konferensbidrag (Refereegranskat)
    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. 

  • 27.
    Berglund, Emil
    et al.
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för informatik och media.
    Facklam, Alexander
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för informatik och media.
    Framgång eller förfall?: Utvecklingen, riskerna och potentialen av BYOD2016Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    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.

  • 28.
    Berglund, Martin
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Palmer, Kristoffer
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Lotfi, Sara
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Kratz, Henrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Thornell, Greger
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Mikrosystemteknik.
    Dynamic characterization and modelling of a dual-axis beam steering device for performance understanding, optimization, and control design2013Ingår i: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 23, nr 4, s. 045020-Artikel i tidskrift (Refereegranskat)
    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.

  • 29.
    Bergman, Jan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutet för rymdfysik, Uppsalaavdelningen.
    Carozzi, Tobia D.
    Onsala Space Observ, S-43882 Onsala, Sweden.
    Robinson, David
    Psi Tran Ltd, 14 Kenton Ave, Sunbury On Thomas TW16 SAR, England.
    Schilling, Klaus
    ZfT, Magdalene Schoch Str 5, D-97074 Wurzburg, Germany.
    Stavrinidis, Constantinos
    IABG mbH, Einsteinstr 20, D-85521 Ottobrunn, Germany.
    DARTS - Distributed Aperture Radio Telescope in Space - First Starlight Explorer2018Ingår i: 2ND URSI ATLANTIC RADIO SCIENCE MEETING (AT-RASC), IEEE , 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    Several studies and proposals have been undertaken in recent years to design a low frequency space radio telescope. However, despite the strong science case for the opening up of a brand-new window on the Universe at a low radio frequency that is largely unexplored, mission proposals have been significantly challenged with the lack of flight proven technologies, to implement a space telescope using low cost small spacecraft formations. In recent years, the advent of CubeSat technologies, interplanetary missions and radio frequency inter-satellite link (ISL) technology, have improved to the point that developing a mission where a space radio telescope is formed using a constellation of small satellites is now viable, to bring unique science offerings.

  • 30.
    Biswas, Sinchan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Dey, Subhrakanti
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    Shirazinia, Amirpasha
    Analyt & AI Grp, S-17062 Stockholm, Sweden.
    Sum Throughput Maximization in a Cognitive Multiple Access Channel With Cooperative Spectrum Sensing and Energy Harvesting2019Ingår i: IEEE TRANSACTIONS ON COGNITIVE COMMUNICATIONS AND NETWORKING, ISSN 2332-7731, Vol. 5, nr 2, s. 382-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper focuses on the problem of sensing throughput optimization in a fading multiple access cognitive radio (CR) network, where the secondary user (SU) transmitters participate in cooperative spectrum sensing and are capable of harvesting energy and sharing energy with each other. We formulate the optimization problem as a maximization of the expected achievable sum-rate over a finite horizon, subject to an average interference constraint at the primary receiver, peak power constraints, and energy causality constraints at the SU transmitters. The optimization problem is a non-convex, mixed integer non-linear program (MINLP) involving the binary action to sense the spectrum or not, and the continuous variables, such as the transmission power, shared energy, and sensing time. The problem is analyzed under two different assumptions on the available information pattern: 1) non-causal channel state information (CSI), energy state information (ESI), and infinite battery capacity and 2) the more realistic scenario of the causal CSI/ESI and finite battery. In the non-casual case, this problem can be solved by an exhaustive search over the decision variable or an MINLP solver for smaller problem dimensions, and a novel heuristic policy for larger problems, combined with an iterative alternative optimization method for the continuous variables. The causal case with finite battery is optimally solved using a dynamic programming (DP) methodology, whereas a number of sub-optimal algorithms are proposed to reduce the computational complexity of DP. Extensive numerical simulations are carried out to illustrate the performance of the proposed algorithms. One of the main findings indicates that the energy sharing is more beneficial when there is a significant asymmetry between average harvested energy levels/channel gains of different SUs.

  • 31.
    Bjurefors, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Measurements in opportunistic networks2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 32.
    Bjurefors, Fredrik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Opportunistic Networking: Congestion, Transfer Ordering and Resilience2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

    Delarbeten
    1. Haggle Testbed: a Testbed for Opportunistic Networks
    Öppna denna publikation i ny flik eller fönster >>Haggle Testbed: a Testbed for Opportunistic Networks
    2011 (Engelska)Ingår i: In Proceedings of the 7th Swedish National Computer Networking Workshop, 2011Konferensbidrag, Publicerat paper (Refereegranskat)
    Identifikatorer
    urn:nbn:se:uu:diva-155530 (URN)
    Projekt
    Haggle
    Tillgänglig från: 2011-06-23 Skapad: 2011-06-23 Senast uppdaterad: 2014-06-30
    2. Congestion Avoidance in a Data-Centric Opportunistic Network
    Öppna denna publikation i ny flik eller fönster >>Congestion Avoidance in a Data-Centric Opportunistic Network
    2011 (Engelska)Ingår i: Proceedings of the 2011 ACM SIGCOMM Workshop on Information-Centric Networking (ICN-2011), 2011Konferensbidrag, Publicerat paper (Refereegranskat)
    Identifikatorer
    urn:nbn:se:uu:diva-155528 (URN)
    Projekt
    ResumeNet
    Tillgänglig från: 2011-06-23 Skapad: 2011-06-23 Senast uppdaterad: 2014-06-30
    3. Making the Most of Your Contacts: Transfer Ordering in Data-Centric Opportunistic Networks
    Öppna denna publikation i ny flik eller fönster >>Making the Most of Your Contacts: Transfer Ordering in Data-Centric Opportunistic Networks
    Visa övriga...
    2012 (Engelska)Ingår i: Proceedings of the 2012 ACM MobiOpp Workshop on Mobile Opportunistic Networks, Zürich: ACM Press, 2012Konferensbidrag, Publicerat paper (Refereegranskat)
    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. 

    Ort, förlag, år, upplaga, sidor
    Zürich: ACM Press, 2012
    Nationell ämneskategori
    Kommunikationssystem
    Identifikatorer
    urn:nbn:se:uu:diva-171587 (URN)
    Konferens
    ACM MobiOpp
    Projekt
    ResumeNet
    Tillgänglig från: 2012-03-22 Skapad: 2012-03-22 Senast uppdaterad: 2014-06-30
    4. Resilience and Opportunistic Forwarding: Beyond Average Value Analysis
    Öppna denna publikation i ny flik eller fönster >>Resilience and Opportunistic Forwarding: Beyond Average Value Analysis
    Visa övriga...
    2014 (Engelska)Ingår i: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 48, nr SI, s. 111-120Artikel i tidskrift (Refereegranskat) 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.

    Nationell ämneskategori
    Kommunikationssystem
    Identifikatorer
    urn:nbn:se:uu:diva-222822 (URN)10.1016/j.comcom.2014.04.004 (DOI)000337883200010 ()
    Projekt
    ResumeNet, WISENET
    Forskningsfinansiär
    EU, FP7, Sjunde ramprogrammet, FP7-224619
    Anmärkning

    Special Issue

    Tillgänglig från: 2014-04-17 Skapad: 2014-04-14 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
  • 33.
    Bjurefors, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Karaliopoulos, Markourios
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Smith, Paul
    Theodoropoulos, George
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Resilience and Opportunistic Forwarding: Beyond Average Value Analysis2014Ingår i: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 48, nr SI, s. 111-120Artikel i tidskrift (Refereegranskat)
    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.

  • 34.
    Bjurefors, Fredrik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Karaliopoulos, Merkourios
    Rohner, Christian
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Smith, Paul
    Theodoropoulos, George
    Gunningberg, Per
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Resilience and Opportunistic Forwarding: Beyond Average Value Analysis2013Ingår i: CHANTS '13 Proceedings of the 8th ACM MobiCom workshop on Challenged networks, 2013Konferensbidrag (Refereegranskat)
    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. 

  • 35. Boano, Carlo Alberto
    et al.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Noda, Claro
    Römer, Kay
    Zuniga, Marco
    JamLab: Augmenting sensornet testbeds with realistic and controlled interference generation2011Ingår i: IPSN, 2011, s. 175-186Konferensbidrag (Refereegranskat)
  • 36.
    Boano, Carlo Alberto
    et al.
    University of Lübeck.
    Wennerström, Hjalmar
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Römer, Kay
    University of Lübeck.
    Hot Packets: A systematic evaluation of the effect of temperature on low power wireless transceivers2013Ingår i: Proc. 5th Extreme Conference on Communication, New York: ACM Press, 2013, s. 7-12Konferensbidrag (Refereegranskat)
    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.

  • 37.
    Borgh, Joakim
    et al.
    Ericsson Res, Stockholm, Sweden.
    Ngai, Edith
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    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 context2017Ingår i: 2017 Global Internet of Things Summit (GIoTS), IEEE, 2017, s. 397-402Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 38.
    Bratel, Daniel
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Industriell teknik.
    Bernestrå, Christopher
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Industriell teknik.
    Internet of Things i Hyresfastigheter: Förutsättningar för implementering av ny teknik2016Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    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.

  • 39. Brown, J.
    et al.
    Roedig, U.
    O'Donovan, T.
    Sreenan, C. J.
    He, Z.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Pottner, B.
    Wolf, L.
    Klein, A.
    Silva, J. Sa
    Vassiliou, V.
    doO, J.
    GINSENG: Performance Control in Wireless Sensor Networks2011Ingår i: 8th European Conference on Wireless Sensor Networks (EWSN’11), 2011Konferensbidrag (Refereegranskat)
  • 40. Brown, James
    et al.
    McCarthy, Ben
    Roedig, Utz
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Sreenan, Cormac J.
    BurstProbe: Debugging Time-Critical Data Delivery in Wireless Sensor Networks2011Ingår i: 8th European Conference on Wireless Sensor Networks (EWSN’11), 2011Konferensbidrag (Refereegranskat)
  • 41.
    Cambazoglu, Volkan
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Protocol, mobility and adversary models for the verification of security2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

    Delarbeten
    1. The impact of trace and adversary models on location privacy provided by K-anonymity
    Öppna denna publikation i ny flik eller fönster >>The impact of trace and adversary models on location privacy provided by K-anonymity
    2012 (Engelska)Ingår i: Proc. 1st Workshop on Measurement, Privacy, and Mobility, New York: ACM Press, 2012, artikel-id 6Konferensbidrag, Publicerat paper (Refereegranskat)
    Ort, förlag, år, upplaga, sidor
    New York: ACM Press, 2012
    Nationell ämneskategori
    Datavetenskap (datalogi)
    Forskningsämne
    Datavetenskap med inriktning mot datorkommunikation
    Identifikatorer
    urn:nbn:se:uu:diva-171581 (URN)10.1145/2181196.2181202 (DOI)978-1-4503-1163-2 (ISBN)
    Konferens
    MPM 2012
    Projekt
    ProFuNWISENET
    Tillgänglig från: 2012-04-10 Skapad: 2012-03-22 Senast uppdaterad: 2018-01-12Bibliografiskt granskad
    2. Towards adaptive zero-knowledge protocols: A case study with Fiat–Shamir identification protocol
    Öppna denna publikation i ny flik eller fönster >>Towards adaptive zero-knowledge protocols: A case study with Fiat–Shamir identification protocol
    2013 (Engelska)Ingår i: Proc. 9th Swedish National Computer Networking Workshop, 2013, s. 67-70Konferensbidrag, Publicerat paper (Refereegranskat)
    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.

    Nationell ämneskategori
    Datavetenskap (datalogi)
    Forskningsämne
    Datavetenskap med inriktning mot datorkommunikation
    Identifikatorer
    urn:nbn:se:uu:diva-201070 (URN)
    Konferens
    SNCNW 2013
    Projekt
    WISENETProFuN
    Tillgänglig från: 2013-06-05 Skapad: 2013-06-05 Senast uppdaterad: 2018-01-11Bibliografiskt granskad
    3. Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support
    Öppna denna publikation i ny flik eller fönster >>Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support
    2015 (Engelska)Rapport (Övrigt vetenskapligt)
    Serie
    Technical report / Department of Information Technology, Uppsala University, ISSN 1404-3203 ; 2015-033
    Nationell ämneskategori
    Datavetenskap (datalogi) Kommunikationssystem
    Forskningsämne
    Datavetenskap med inriktning mot datorkommunikation
    Identifikatorer
    urn:nbn:se:uu:diva-268453 (URN)
    Projekt
    ProFuN
    Forskningsfinansiär
    Stiftelsen för strategisk forskning (SSF), RIT08-0065
    Tillgänglig från: 2015-12-03 Skapad: 2015-12-04 Senast uppdaterad: 2018-01-10Bibliografiskt granskad
  • 42.
    Cambazoglu, Volkan
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Gutkovas, Ramunas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Åman Pohjola, Johannes
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Victor, Björn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Modelling and analysing a WSN secure aggregation protocol: A comparison of languages and tool support2015Rapport (Övrigt vetenskapligt)
  • 43.
    Carlos, Perez Penichet
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Hermans, Frederik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Varshney, Ambuj
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Augmenting IoT networks with backscatter-enabled passive sensor tags2016Ingår i: Proceedings of the 3rd Workshop on Hot Topics in Wireless, 2016, s. 23-27Konferensbidrag (Refereegranskat)
    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.

  • 44.
    Carlos, Perez Penichet
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation. Uppsala Univ, Uppsala, Sweden.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. RISE SICS, Lulea, Sweden.
    Carrier Scheduling in IoT Networks with Interoperable Battery-free Backscatter Tags2019Ingår i: IPSN '19: Proceedings of the 2019 International Conference on Information Processing in Sensor Networks, Association for Computing Machinery (ACM), 2019, s. 329-330Konferensbidrag (Refereegranskat)
    Abstract [en]

    New battery-free backscatter tags that integrate with unmodified standard IoT devices can extend the latter's sensing capabilities in a scalable and cost effective way. Existing IoT nodes can provide the unmodulated carrier needed by the new nodes, avoiding the need for additional infrastructure. This, however, puts extra energetic demands on constrained IoT nodes while increasing interference and contention in the network. We use a slotted MAC protocol to guarantee synchronization between transmitters, receivers and carrier generators. We then express the slot allocation problem as a Constraint Optimization Problem (COP) that parallelizes interrogations to battery-free tags when they do not collide with each other and reuses carriers for multiple tags looking to minimize the total time and the number of carrier generators needed to interrogate a set of tags. In networks with sufficient battery-free nodes we obtain a 25% reduction in the number of necessary carriers and a 50% decrease in interrogation time in most cases; leading to significant energy savings, reduced collisions and improved latency.

  • 45.
    Carlos, Pérez Penichet
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Hermans, Frederik
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    On Limits of Constructive Interference in Backscatter Systems2017Ingår i: Global Internet of Things Summit (GIoTS), 2017, IEEE, 2017, s. 178-182Konferensbidrag (Övrigt vetenskapligt)
    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.

  • 46. 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 universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Towards business processes orchestrating the physical enterprise with wireless sensor networks2012Ingår i: ICSE, 2012, s. 1357-1360Konferensbidrag (Refereegranskat)
  • 47. Cea, Mauricio G.
    et al.
    Goodwin, Graham C.
    Wigren, Torbjörn
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för systemteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Reglerteknik.
    Model predictive zooming power control in future cellular systems under coarse quantization2012Ingår i: Proc. 76th Vehicular Technology Conference, Piscataway, NJ: IEEE, 2012Konferensbidrag (Refereegranskat)
  • 48.
    Charalambous, Themistoklis
    et al.
    Aalto Univ, Sch Elect Engn, Dept Elect Engn & Automat, Espoo, Finland..
    Özcelikkale, Ayca
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Signaler och System.
    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 Systems2017Ingår i: 2017 IEEE 56Th Annual Conference On Decision And Control (Cdc), IEEE, 2017, s. 4147-4154Konferensbidrag (Refereegranskat)
    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.

  • 49.
    Chen, Bolin
    et al.
    Univ Sheffield, Dept Elect & Elect Engn, Sheffield S38AN, S Yorkshire, England.
    You, Lei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Yuan, Di
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Pappas, Nikolaos
    Linkoping Univ, Dept Sci & Technol, S-60174 Norrkoping, Sweden.
    Zhang, Jie
    Univ Sheffield, Dept Elect & Elect Engn, Sheffield S38AN, S Yorkshire, England.
    Resource Optimization for Joint LWA and LTE-U in Load-Coupled and Multi-Cell Networks2019Ingår i: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 23, nr 2, s. 330-333Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider the performance optimization of multi-cell networks with LTE and Wi-Fi aggregation (LWA) and LTE-unlicensed (LTE-U) with sharing of the unlicensed band. Theoretical results are derived to enable an algorithm to approach the optimum. Numerical results show the algorithm's effectiveness and benefits of joint use of LWA and LTE-U.

  • 50.
    Cooray, Vernon
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
    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 Ground2018Ingår i: Atmosphere, ISSN 2073-4433, E-ISSN 2073-4433, Vol. 9, nr 5, artikel-id 193Artikel i tidskrift (Refereegranskat)
    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.

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