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  • 401.
    Engholm, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norin, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Preventing Photodarkening in Ytterbium-Doped High Power Fiber Lasers; Correlation to the UV-Transparency of the Core Glass2008In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 16, no 2, p. 1260-1268Article in journal (Refereed)
    Abstract [en]

     

    Photodarkening experiments are performed on ytterbium-doped silicate glass

    samples. A strong charge-transfer (CT) absorption band near 230nm in

    aluminosilicate glass is found to be correlated to the mechanism of induced

    color center formation. Excitation into the CT-absorption band generates

    similar color centers as observed in ytterbium-doped fiber lasers under

    915nm high power diode pumping. The position of the CT-absorption band is

    compositional dependent and is shifted to shorter wavelengths in ytterbium

    doped phosphosilicate glass. Very low levels of photodarkening is observed

    for the ytterbium doped phosphosilicate glass composition under 915nm high

    power diode pumping. Possible excitation routes to reach the CT-absorption

    band under 915nm pumping are discussed.

     

  • 402.
    Engholm, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media. Acreo FiberLab, Sweden.
    Norin, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Reduction of photodarkening in Yb/Al-doped fiber lasers2008In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2008, p. U269-U276Conference paper (Refereed)
    Abstract [en]

    A strong charge-transfer band at UV-wavelengths is found to play a major role for the observed induced optical losses (photodarkening) in ytterbium doped high-power fiber lasers. This is correlated to the valence stability of the ytterbium ion in the silicate glass matrix, which we believe is the origin of photodarkening. We have performed UV-irradiation experiments on ytterbium-doped preform samples and accelerated photodarkening experiments on Yb-doped fibers, by using 915nm high power diodes. Our results show that photodarkening can be reduced, to low levels, either by preparing the preform glass in a reducing atmosphere or by hydrogen loading the fiber in a pressure chamber at room temperature.

  • 403.
    Engholm, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norin, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Strong UV absorption and visible luminescence in ytterbium-doped aluminosilicate glass under UV excitation2007In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 32, no 22, p. 3352-3354Article in journal (Refereed)
    Abstract [en]

    A broad visible luminescence band and characteristic IR luminescence of Yb3+ ions are observed under UV excitation in ytterbium-doped aluminosilicate glass. Samples made under both oxidizing and reducing conditions are analyzed. A strong charge-transfer absorption band in the UV range is observed for glass samples containing ytterbium. Additional absorption bands are observed for the sample made under reducing conditions, which are associated with f�d transitions of divalent ytterbium. The visible luminescence band is attributed to 5d�4f emission from Yb2+ ions, and the IR luminescence is concluded to originate from a relaxed charge-transfer transition. The findings are important to explain induced optical losses (photodarkening) in high-power fiber lasers.

  • 404.
    Engholm, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norin, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Edvardsson, Sverker
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lashgari, K.
    Uppsala University.
    Westin, G.
    Uppsala University.
    A structural investigation of a synthesized precursor for fiber optical applications; the heterobimetallic ErNb_2(OPr^i)_132006In: Optical materials (Amsterdam), ISSN 0925-3467, E-ISSN 1873-1252, Vol. 29, no 4, p. 386-391Article in journal (Refereed)
    Abstract [en]

    A structural investigation of a synthesized precursor in a silica glass matrix is performed. Silica soot samples are doped with the heterobimetallic precursor ErNb2(OPri)13 by using a conventional solution doping technique and heat treatments to different temperatures. The precursor has also been introduced into a silica fiber preform by using the modified chemical vapor deposition technique. Analyses are made by using ultraviolet–visible–near infrared absorption spectroscopy, scanning electron microscopy, energy dispersive spectroscopy and powder X-ray diffraction. It is concluded that an immiscible system of ErNbO4 crystallites and Nb2O5 is formed in the silica soot samples at high temperatures. Colloidal particles of ErNbO4 are also formed in the silica glass fiber preform showing interesting features.

  • 405.
    Engholm, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Rydberg, Sara
    Hammarling, Krister
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Strong excited state absorption (ESA) in Yb-doped fiber lasers2013In: FIBER LASERS X: TECHNOLOGY, SYSTEMS, AND APPLICATIONS, SPIE - International Society for Optical Engineering, 2013, p. Art. no. 86010P-Conference paper (Refereed)
    Abstract [en]

    Excited state absorption (ESA) measurements performed on Yb-doped silica bers show the onset of a strong absorption band in the visible range. In this work, we perform experiments to investigate the possibility for ESA to be part of the induced optical losses (photodarkening) observed in Yb-doped ber lasers. Our results indicate that an ESA process, from the 2F5/2 excited state manifold in the Yb3+ ion to the charge-transfer state with absorption bands in the UV range, may constitute a transfer route for pump- and laser photons in the near-infrared range. © 2013 Copyright SPIE.

  • 406.
    Engholm, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Vanin, E
    Norin, Lars
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Characterization of Erbiuim Crystallites Embedded in Silica GlassManuscript (Other (popular science, discussion, etc.))
  • 407. Ericsson, A.
    et al.
    Norell, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Comparison of Noise Reduction and MPEG-2 Compression Efficiency for Pre-Processing Video Filters2004In: IWSSIP'04 : international workshop on systems, signals and image processing :   ( Poznan, 13-15 September 2004 ), Poznan, Poland: Polish Society for Theoretical and Applied Electrical Engineering , 2004Conference paper (Refereed)
    Abstract [en]

    Video information that is input in digital video recorders or distributed over the Internet comes in various different qualities. One possibility to improve the video quality and also to improve the efficiency of the video encoder is to use different types of spatial or temporal video filters. This paper presents a comparison of the noise reduction efficiency for three different video filters. Additionally, the improvement of MPEG-2 encoding efficiency is compared. The results provide an efficiency function that can be used to select an appropriate filter type for a special situation.

  • 408.
    Eriksson, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Packet and Resource Plan Scheduling (PARPS) - with Application to Mobile IP over DVB-T2000In: Proceedings of The 2000 International Conference on Broadband Wireless Access Systems (WAS2000), 4-6 December 2000, San Francisco, U.S.A. / [ed] Willie W. LU, 2000Conference paper (Other academic)
    Abstract [en]

    The Terrestrial Digital Video Broadcasting system (DVB-T) can be utilized as a supplemental broadband downlink to today´s cellular systems. Thus, mobile Internet access with downstream peek bit rates of 10 to 30 Mbit/s can be achieved. To make this concept competitive in comparison to for example UMTS, efficient Radio Resource Management (RRM) is essential. Schemes for downlink dynamic RRM on a packet-by-packet basis are suggested and evaluated for a simplified packet data model. Packet and Resource Plan Scheduling (PARPS) schemes reduce the problem of finding an optimized combination of several RRM parameters to a scheduling problem. Dynamic Single Frequency Networks (DSFN) and Virtual Cellular Networks (VCN) exploits the macro-diversity capability of the OFDM modulation scheme by dynamically forming groups of transmitters that send the same information on the same frequency channel simultaneously. Dynamic Packet Assignment (DPA) is a combination of Dynamic Channel Assignment (DCA) and packet scheduling. The Fairly Shared Spectrum Efficiency (FSSE), in bit/s/Hz/transmitter site, is improved by up to 370% for a certain test cases, by the DSFN scheme in comparison to DPA.

  • 409.
    Eriksson, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Mahmud, Arif
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Transmitter Macrodiversity in Multihopping: SFN based algorithm for improved node reachability and robust routing2010In: World Academy of Science, Engineering and Technology (WASET) International Conference on Computer Science and Technology (ICCST’10), Rome, Italy, 28-30 April 2010, Rome, Italy, 2010, p. 404-408Conference paper (Refereed)
    Abstract [en]

    A novel idea presented in this paper is to combine multihop routing with single-frequency networks (SFNs) for a broadcasting scenario. An SFN is a set of multiple nodes that transmit the same data simultaneously, resulting in transmitter macrodiversity. Two of the most important performance factors of multihop networks, node reachability and routing robustness, are analyzed. Simulation results show that our proposed SFN-D routing algorithm improves the node reachability by 37 percentage points as compared to non-SFN multihop routing. It shows a diversity gain of 3.7 dB, meaning that 3.7 dB lower transmission powers are required for the same reachability. Even better results are possible for larger networks. If an important node becomes inactive, this algorithm can find new routes that a non-SFN scheme would not be able to find. Thus, two of the major problems in multihopping are addressed; achieving robust routing as well as improving node reachability or reducing transmission power.

  • 410.
    Eriksson, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Rahman, S. M. Hasibur
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Fraile, Francisco
    Universitat Politècnica de València, Spain .
    Sjöström, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Efficient Interactive Multicast over DVB-T2: Utilizing Dynamic SFNs and PARPS2013In: IEEE International Symposium on Broadband Multimedia Systems and Broadcasting, BMSB, IEEE conference proceedings, 2013, p. Art. no. 6621700-Conference paper (Refereed)
    Abstract [en]

    In the terrestrial digital TV systems DVB-T/H/T2, broadcasting is employed, meaning that all TV programs are sent over all transmitters, also where there are no viewers. This is inefficient utilization of spectrum and transmitter equipment. Applying interactive multicasting over DVB-T2 is a novel approach that would substantially reduce the spectrum required to deliver a certain amount of TV programs. Further gain would be achieved by Dynamic single-frequency network (DSFN) formations, which can be implemented using the concept of PARPS (Packet and Resource Plan Scheduling). A Zipf-law heterogeneous program selection model is suggested. For a system of four coordinated transmitters, and certain assumptions, IP multicasting over non-continuous transmission DSFN gives 1740% increase in multiuser system spectral efficiency (MSSE) in (users∙bit/s)/Hz/site as compared to broadcasting over SFN.

  • 411.
    Eriksson, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Xu, Youzhi
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Packet-by-packet Radio Resource Management by means of Dynamic Single Frequency Networks: The 2000 International Conference on Broadband Wireless Access Systems (WAS'00), San Fransisco, U.S.A., December 4-6, 20002000Conference paper (Other academic)
    Abstract [en]

    By combining a cellular system with the terrestrial digital video broadcasting system (DVB-T), wide-area asymmetric Internet access can be achieved, with a downlink peak bit rate of 10-20Mbps. In this paper, we study dynamic resource management on a packet-by-packet basis for this broadband downlink. A model for best-effort traffic is proposed, which simplifies the evaluation of maximum throughput and fairness. Dynamic Single Frequency Networks (DSFN) are evaluated, which exploits the macrodiversity capability of the OFDM modulation scheme. The transmitters are divided into single frequency networks (SFNs), i.e. groups of transmitters that send the same information at the same channel frequency simultaneously. An algorithm changes the SFN grouping from timeslot to timeslot, and schedules the packets. DSFN is a way of introducing timeslots and Dynamic Channel Allocation into DVB-T, without keying of the transmitter power. Thus, receiver and transmitter circuits existing on the market today can be used, and only software modifications are required. A spectrum efficiency of 0.45 bit/s/Hz/site is achieved with omni-directional antennas under certain conditions. This is a capacity improvement of 170% in comparison to a Fixed Channel Allocation solution with static handover.

  • 412.
    Eriksson, Oskar
    et al.
    Uppsala University.
    Björnemo, Erik
    Uppsala University.
    Ahlén, Anders
    Uppsala University.
    Gidlund, Mikael
    ABB Corporate Research.
    On Hybrid ARQ Adaptive Forward Error Correction in Wireless Sensor Networks2011In: IECON 2011 - 37th Annual Conference on IEEE Industrial Electronics Society, IEEE conference proceedings, 2011, p. 3004-3010Conference paper (Refereed)
    Abstract [en]

    The use of wireless technology in the process industry is becoming increasingly important to obtain fast deployment at low cost. However, poor channel quality often leads to retransmissions, which are governed by Automatic Repeat Request (ARQ) schemes. While ARQ is a simple and useful tool to alleviate packet errors, it has considerable disadvantages: retransmissions lead to an increase in energy expenditure and latency. The use of Forward Error Correction (FEC) however offers several advantages. We consider a Hybrid-ARQ-Adaptive-FEC scheme (HAF) based on BCH codes and Channel State Information. This scheme is evaluated on AWGN and fading channels. It is shown that HAF offers significantly improved performance both in terms of energy efficiency and latency, as compared to ARQ.

  • 413.
    Esebamen, Omeime
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    N+P photodetector characterization using the quasi-steady state photoconductance decay method2012In: Journal of Semiconductors, ISSN 1674-4926, Vol. 33, no 12, p. Art. no. 123002-Article in journal (Refereed)
    Abstract [en]

    When a material is irradiated, it becomes more electrically conductive due to the absorption of the electromagnetic radiation. As a result, the number of free electrons and holes changes and raises its electrical conductivity. A simple but interesting phenomenon to characterise a fabricated n+p photodetector in order to determine its linearity (photoresponse) and photoconductance was employed. Using the transient decay when the irradiation source is switched off, the minority carrier concentration, effective lifetime and surface recombination velocity present at the surface of the detector were measured. © 2012 Chinese Institute of Electronics.

  • 414.
    Esebamen, Omeime
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Norlin, Börje
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Spectral Performance of Photon Counting Pixel Detector Using Attenuation Spectra for Test Samples2009In: AIP Conference Proceedings Volume 1204, New York: American Institute of Physics (AIP), 2009, p. 177-179Conference paper (Refereed)
    Abstract [en]

    When a material is placed along the path of an X-ray beam using a broad range of energy X-ray source, the energy dependence of the attenuation for the X-ray photons will be substantially dissimilar for different materials. The process at which X-ray radiation loses its penetrating strength as it travels through a material will be significantly larger for photons with energy above k-edge energy of that material than for those with slightly lower energy. Hence energy resolved X-ray imaging can be used to achieve colour images revealing the material content of the test sample. The attenuation of the spectrum done by scanning an energy window through the spectrum was measured for a number of samples of different materials. The test samples include Sn, Gd and I with K-edge energy at 29 keV, 50 keV and 33 keV, respectively, using a Feinfocus microfocus X-ray source (FTP-105.02) with Medipix2 photon counting chip.

  • 415.
    Esebamen, Omeime X.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Effect of UV radiation surface damage on silicon position sensitive photodetector2016In: Optik (Stuttgart), ISSN 0030-4026, E-ISSN 1618-1336, Vol. 127, no 2, p. 599-602Article in journal (Refereed)
    Abstract [en]

    As a result of the ever increasing energetic UV radiation doses and the need for more radiation hard devices, damage and degradation testing of optical sensors have become very imperative. In this report, results describing the effect of prolonged UV beam irradiation on the performance of a p+n duo-lateral position sensitive detector (lPSD) are reported. The results include the use of a simple method to visualize in 3-dimensional graphs, the effect of radiation damage on the lPSD sensitivity and position detection deviation over the entire active area. The results also show that the ionization damage effects at the Silicon-Silicon oxide interface result in decrease in sensitivity, increase in position detection deviation, and increase in leakage and shot noise current.

  • 416.
    Esebamen, Omeime X.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Krapohl, David
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    High resolution, low energy electron detector2011In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 6, no 1, p. Art. no. P01001-Article in journal (Refereed)
    Abstract [en]

    Electron detection at low energy range for scanning electron microscope (SEM), electron capture detector and electron probe micro-analysis (EPMA) applications, require detectors with high sensitivity and accuracy for low energy range. Such detectors must therefore have a thin entrance window and low recombination at the Si-SiO2 interface. An electron detector with 100 photons to electron-hole pair production rate having a 10 nm SiO2 passivating layer reveals a responsivity of approximately 0.25 A/W when irradiated. Simulations results showing the responsivity of electron interaction between detectors of varied interface fixed oxide charge density Qf show that there is an appreciable difference with the responsivity of a p +n detector and that of an n+p. The simulation results also show the significance of the effect of the minority carriers transport velocity Sn,p on the responsivity of the detector. © 2011 IOP Publishing Ltd and SISSA.

  • 417.
    Esebamen, Omeime Xerviar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Characterization of interface states & radiation damage effects in duo-lateral PSDs: Using SEM microscopy and UV beam profiling techniques2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There has been an increase in the use of duo‐lateral position sensitive detectors inpractically every radiation and beam detection application. These devices unlike other light detection system utilize the effect of the lateral division of the generated photocurrent to measure the position of the integral focus of an incoming lightsignal. The performance of a PSD is impaired or strengthened by a number of events caused by parameters such as interface states and recombination introduced during the fabrication of the detector and/or its absorption of ionizing particles. This thesis show the results from the successful implementation of alternative characterization methods of these effects and parameters using scanning electronmicroscopy and UV beam profiling techniques on duo‐lateral position sensitive detectors (LPSDs). To help create the groundwork for the research content of this thesis, different technical reviews of previous studies on interface states, surface recombination velocity and radiation damage due to continuous absorption of ionizing irradiation on detectors are investigated. The thesis also examines published theoretical and measurement techniques used to characterize these surface/interface phenomena. The PSDs used in this research were developed using silicon technology and the various methodologies put into the fabrication of the detectors (n+p and p+n structures) were fashioned after the simulated models. The various steps associated with the clean room fabrication and the prior simulation steps are highlighted in the content of the thesis. Also discussed are the measurement techniques used incharacterizing the fixed oxide charge, surface recombination and the position deviation error of the LPSDs in a high vacuum environment of a scanning electron microscope SEM chamber. Using this method, the effects of interface states and surface recombination velocity on the responsivity of differently doped LPSDs were investigated. By lithographically patterning grid‐like structures used as scaleon n+p doped LPSD and using sweeping electrons from the SEM microscope, a very high linearity over the two‐dimensions of the LPSD total active area was observed. An improved responsivity for low energetic electrons was also achievedby the introduced n+p structure. The lithographically patterned grids helped eliminate further external measurement errors and uncertainties from the use of other typical movable measurement devices such as actuators and two dimensional adjusters which would normally be difficult to install in a remote vacuum chamber. In a similar vein, field plate and field rings were patterned around an array ofthe PSDs used as pixel detector(s). By studying the interpixel resistance and breakdown characteristics, the most effective structural arrangement of the field plate and field rings used to curb induced inversion channel between the n+ doped regions of the pixel‐detector is observed. By using UV beam profiling after the irradiation of UV (193 nm or 253 nm) beam on n+p and p+n doped PSDs, the degree of radiation damage was also investigated. The results obtained help to illustrate how prolonged UV radiation can impact on the linearity and the position deviation/error of UV detectors. The results in this thesis are most relevant in spectroscopic and microscopic applications where low energy electrons and medium UV (MUV) radiation are used.

  • 418.
    Esebamen, Omeime Xerviar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Simulation, Measurement and Analysis of the Response of Electron- and Position Sensitive Detector2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Different methods exist in relation to probing and investigating thephysical and structural composition of materials especially detectors whoseusage have become an integral part of radiation detection. The use of thescanning electron microscopy is just one of such exploratory methods. Thistechnique uses a focused beam of high-energy electrons to generate a varietyof signals at the surface of the device under investigationThis thesis presents the results derived from signals from electron beamsampleinteractions, revealing information about the different cleanroomfabricated electron detectors used. This information includes the detector’sexternal morphology and texture, surface recombination, fixed oxide chargeand the behavioral characteristic in the form of its position detection accuracyand linearity.An electron detector with a high ionization factor and which has a 10nmSilicon Oxide passivating layer was fabricated. Results from using the scanningelectron microscopy showed that its maximum responsivity wasapproximately 0.25 A/W from a possible 0.27 A/W. In conjunction withsimulations, results also showed the significance of the effect of the minoritycarrier's surface recombination velocity on the responsivity of the detectors.In addition, measurements were conducted to ascertain the performancevariance of these electron detectors with respect to their surfacerecombination velocity and fixed oxide charge when the doping profile isaltered.By incorporating special features on a fabricated duo-lateral positionsensitive detector (PSD), a position sensing resolution of the PSD using theelectron microscopic method was also evaluated. The evaluation showed avery high linearity over two-dimensions for 77% of the PSD’s active area.The results in this thesis offer a significant improvement in electrondetectors for applications such as gas chromatography detection of traceamounts of chemical compounds in a sample as well as applications involvingposition sensitive detection.

  • 419.
    Esebamen, Omeime Xerviar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Lundgren, A
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    An n+p Duo-lateral Position Sensitivity Detector with High Sensitivity to Low Energetic ElectronsManuscript (preprint) (Other academic)
  • 420.
    Esebamen, Omeime Xerviar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A Different Approach of Determining the Responsivity of n+p Detectors Using Scanning Electron Microscopy2012In: Journal of semiconductors, ISSN 1674-4926, Vol. 33, no 7, p. 074002-Article in journal (Refereed)
    Abstract [en]

    This paper explores an alternative to the standard method of studying the responsivities (the input—output gain) and other behaviours of detectors at low electron energy. The research does not aim to compare the results of differently doped n+p detectors; its purpose is to provide an alternative characterization method (using scanning electron microscopy) to those used in previous studies on the responsivity of n+p doped detectors as a function of the electron radiation energy and other interface parameters.

  • 421.
    Esebamen, Omeime Xerviar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lundgren, Anders
    SiTek Electro Opt, SE-43330 Partille, Sweden.
    Comparative Study of UV Radiation Hardness of n+p and p+n Duo-Lateral Position Sensitive Detectors2014In: European Physical Journal: Applied physics, ISSN 1286-0042, E-ISSN 1286-0050, Vol. 68, no 2, p. Art. no. 21301-Article in journal (Refereed)
    Abstract [en]

    We report experimental results on the degree of radiation damage in two duo-lateral position sensitive detectors (LPSDs) exposed to 193 nm and253 nm ultraviolet (UV) beam. One of the detectors was an in-house fabricated n(+) p LPSD and the other was a commercially available p(+) n LPSD. We report that at both wavelengths, the degradation damage from the UV photons absorption caused a much more significant deterioration in responsivity in the p(+) n LPSD than in the n(+) p LPSD. By employing a simple method, we were able to visualize the radiation damage on the active area of the LPSDs using 3-dimensional graphs. We were also able to characterize the impact of radiation damage on the linearity and position error of the detectors.

  • 422.
    Esebamen, Omeime Xerviar
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thungström, Göran
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Nilsson, Hans-Erik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lundgren, Anders
    SiTek Electro Optics AB, Ögärdesvägen 13A, SE-433 30 Partille, Sweden .
    Gridded Duo-lateral Position Sensitivity Detector with High Linearity to Low Energetic Electrons in Vacuum Environment2014In: IET Optoelectronics, ISSN 1751-8768, E-ISSN 1751-8776, Vol. 8, no 6, p. 217-225Article in journal (Refereed)
    Abstract [en]

    Characterizing a position sensitive detector in a vacuum environment without beam position monitoring devices can bechallenging and expensive. With this in mind, we have designed and fabricated a duo-lateral position sensitive detector (PSD) incorporatedwith simple and inexpensive surface features. It was evaluated using scanning electron microscopy. To assist in pinpointing precise positioningas well as acting as path guide during the sweeping of electrons, multiple grids were lithographically patterned on the top layer of the duolateralPSD. By sweeping electrons along two axes of the detector, the position detection error of both axes was determined from the signalsrecorded using a transimpedance amplification circuit. We were able to characterize the linearity over the x- and y-axis of the PSD and theresults show a very high linearity over two-dimensions of the PSD’s active area and that accurate beam monitoring for spectroscopic measurement without additional beam position monitoring devices is possible.

  • 423.
    Fabre, Arthur
    et al.
    Electronics and Computer Science University of Southampton, UK.
    Martinez, Kirk
    Electronics and Computer Science University of Southampton, UK.
    Bragg, Graeme
    Electronics and Computer Science University of Southampton, UK.
    Basford, Philip
    Electronics and Computer Science University of Southampton, UK.
    Hart, Jane
    Geography and Environment University of Southampton, UK.
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bragg, Olivia
    Environment University of Dundee, UK.
    Deploying a 6LoWPAN, CoAP, low power, wireless sensor network: Poster Abstract2016In: Proceedings of the 14th ACM Conference on Embedded Network Sensor Systems CD-ROM, 2016, p. 362-363Conference paper (Refereed)
    Abstract [en]

    In order to integrate equipment from different vendors, wireless sensor networks need to become more standardized. Using IP as the basis of low power radio networks, together with application layer standards designed for this purpose is one way forward. This research focuses on implementing and deploying a system using Contiki, 6LoWPAN over an 868 MHz radio network, together with CoAP as a standard application layer protocol. A system was deployed in the Cairngorm mountains in Scotland as an environmental sensor network, measuring streams, temperature profiles in peat and periglacial features. It was found that RPL provided an effective routing algorithm, and that the use of UDP packets with CoAP proved to be an energy efficient application layer. This combination of technologies can be very effective in large area sensor networks.

  • 424.
    Farag, Hossam
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Enabling Time- and Mission-Critical Applications in Industrial Wireless Sensor Networks2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nowadays, Wireless Sensor Networks (WSNs) have gained importance as aflexible, easier deployment/maintenance and cost-effective alternative to wired networks,e.g., Fieldbus and Wired-HART, in a wide-range of applications. Initially,WSNs were mostly designed for military and environmental monitoringapplications where energy efficiency is the main design goal. The nodes in the network were expected to have a long lifetime with minimum maintenance while providing best-effort data delivery which is acceptable in such scenarios. With recent advances in the industrial domain, WSNs have been subsequently extended to support industrial automation applications such as process automation and control scenarios. However, these emerging applications are characterized by stringent requirements regarding reliability and real-time communications that impose challenges in the design of Industrial Wireless Sensor Networks (IWSNs) to effectively support time- and mission-critical applications.

    Typically, time- and mission-critical applications support different traffic categories ranging from relaxed requirements, such as monitoring traffic to firm requirements, such as critical safety and emergency traffic. The critical traffic is mostly acyclic in nature and occasionally occurs at unpredictable time instants. Once it is generated, it must be delivered within strict deadlines. Exceeding the delay bound could lead to system instability, economic loss, or even endanger human life in the working area. The situation becomes even more challenging when an emergency event triggers multiple sensor nodes to transmit critical traffic to the controller simultaneously. The unpredictability of the arrival of such a type of traffic introduces difficulties with regard to making a suitable scheduling that guarantees data delivery within deadline bounds. Existing industrial standards and related research work have thus far not presented a satisfactory solution to the issue. Therefore, providing deterministic and timely delivery for critical traffic and its prioritization over regular traffic is a vital research topic.

    Motivated by the aforementioned challenges, this work aims to enable real-timecommunication for time- and mission-critical applications in IWSNs. In this context, improved Medium Access Control (MAC) protocols are proposed to enablea priority-based channel access that provides a timely delivery for acyclic critical traffic. The proposed framework starts with a stochastic modelling of the network delay performance under a priority-oriented transmission scheme, followed by two MAC approaches. The first approach proposes a random Clear Channel Assessment (CCA) mechanism to improve the transmission efficiency of acyclic control traffic that is generated occasionally as a result of observations of an established tendency, such as closed-loop supervisory traffic. A Discrete-Time Markov Chain (DTMC) model is provided to evaluate the performance of the proposed protocol analytically in terms of the expected delay and throughput. Numerical results show that the proposed random CCA mechanism improves the shared slots approach in WirelessHART in terms of delay and throughput along with better transmission reliability.

    The second approach introduces a slot-stealing MAC protocol based on a dynamic deadline-aware scheduling to provide deterministic channel access in emergency and event-based situations, where multiple sensor nodes are triggered simultaneously to transmit time-critical data to the controller. The proposed protocol is evaluated mathematically to provide the worst-case delay bound for the time-critical traffic and the numerical results show that the proposed approach outperforms TDMA-based WSNs in terms of delay and channel utilization.

  • 425.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    A Delay-Bounded MAC Protocol for Mission- and Time-Critical Applications in Industrial Wireless Sensor Networks2018In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 18, no 6, p. 2607-2616Article in journal (Refereed)
    Abstract [en]

    Industrial Wireless Sensor Networks (IWSNs) designedfor mission- and time-critical applications require timelyand deterministic data delivery within stringent deadline bounds.Exceeding delay limits for such applications can lead to system malfunction or ultimately dangerous situations that can threaten human safety. In this paper, we propose SS-MAC, an efficient slot stealing MAC protocol to guarantee predictable and timely channel access for time-critical data in IWSNs. In the proposed SS-MAC, aperiodic time-critical traffic opportunistically steals time slots assigned to periodic non-critical traffic. Additionally, a dynamic deadline-based scheduling is introduced to provide guaranteed channel access in emergency and event-based situations where multiple sensor nodes are triggered simultaneously to transmit time-critical data to the controller. The proposed protocol is evaluated mathematically to provide the worst-case delay bound for the time-critical traffic. Performance comparisons are carried out between the proposed SS-MAC and WirelessHARTstandard and they show that, for the time-critical traffic, theproposed SS-MAC can achieve, at least, a reduction of almost 30% in the worst-case delay with a significant channel utilization efficiency.

  • 426.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    DeP-D: A Decentralized Primal-Dual Optimization Algorithm for Industrial Wireless Sensor Networks2019In: 2019 15th IEEE International Workshop on Factory Communication Systems (WFCS), IEEE, 2019, article id 8757934Conference paper (Refereed)
    Abstract [en]

    Industrial Wireless Sensor Networks (IWSNs) are emerged as flexible and cost-efficient alternatives to the traditional wired networks in various monitoring and control applications within the industrial domain. Low delay is a key feature of delay-sensitive applications as the data is typically valid for a short interval of time. If data arrives too late it is of limited use which may lead to performance drops or even system outages which can create significant economical losses. In this paper, we propose a decentralized optimization algorithm to minimize the End-to-End (E2E) delay of multi-hop IWSNs. Firstly, we formulate the optimization problem by considering the objective function as the network delay where the constraint is the stability criteria based on the total arrival rate and the total service rate. The objective function is proved to be strictly convex for the entire network, then a Decentralized Primal-Dual (DeP-D) algorithm is proposed based on the sub-gradient method to solve the formulated optimization problem. The performance of the proposed DeP-D is evaluated through simulations and compared with WirelessHART network and the results show that the proposed DeP-D can achieve at least 40% reduction in the average E2E delay.

  • 427.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Mahmood, Aamir
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    PR-CCA MAC: A Prioritized Random CCA MAC Protocol for Mission-Critical IoT Applications2018In: 2018 IEEE International Conference on Communications (ICC), IEEE, 2018, article id 8423018Conference paper (Refereed)
    Abstract [en]

    A fundamental challenge in Mission-Critical Internetof Things (MC-IoT) is to provide reliable and timely deliveryof the unpredictable critical traffic. In this paper, we propose an efficient prioritized Medium Access Control (MAC) protocol for Wireless Sensor Networks (WSNs) in MC-IoT control applications. The proposed protocol utilizes a random Clear Channel Assessment (CCA)-based channel access mechanism to handlethe simultaneous transmissions of critical data and to reduce thecollision probability between the contending nodes, which in turn decreases the transmission latency. We develop a Discrete-Time Markov Chain (DTMC) model to evaluate the performance of the proposed protocol analytically in terms of the expected delay and throughput. The obtained results show that the proposed protocolcan enhance the performance of the WirelessHART standard by 80% and 190% in terms of latency and throughput, respectively along with better transmission reliability.

  • 428.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab
    Osaka University, Japan.
    An Efficient Dynamic Thresholds Energy Detection Technique for Cognitive Radio Spectrum Sensing2014In: 10th International Computer Engineering Conference: Today Information Society What's Next?, ICENCO 2014, IEEE, 2014, p. 1623-1628Conference paper (Refereed)
    Abstract [en]

    Cognitive Radio (CR) is an intelligent technique for opportunistic access of idle resources. In CR, Spectrum sensing is one of its important key functionalities. It is used to sense the unused spectrumin an opportunistic manner. Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio due to its simplicity and applicability. The conventional energy detection technique, which is based upon fixed threshold, is sensitive to noise uncertainty which is unavoidable in practical cases. This noise uncertainty gets the fixed threshold energy detector un-optimized in its performance. In this paper, an efficient energy detector is proposed for optimal CR performance. The proposed scheme is based upon a dynamic threshold energy detection algorithm, in which, the decision threshold is toggled between two levels based upon the average energy received from the primary user (PU) during a specified period of observation. Thresholds evaluations are based upon estimating the noise uncertainty factor. These thresholds are used to maximize the probability of detection (Pd) and minimize the probability of false alarm (Pfa). Theoretical analysis and simulation results show the effectiveness of the proposed scheme in comparison to the conventional energy detection method with less increase in complexity.

  • 429.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Aswan University, Egypt.
    Dynamic Threshold Hard Decision Cooperative Spectrum Sensing Using Two-Stage Censoring2016In: 23rd International Conference on Telecommunications, ICT 2016, IEEE, 2016, p. 38-42Conference paper (Refereed)
    Abstract [en]

    In hard decision cooperative spectrum sensing (CSS), each secondary user (SU) or simply cognitive radio user (CR) senses the primary user (PU) activity via a Sensing channel (S-channel) and forwards its own binary decision to a fusion center (FC) via a Reporting channel (R-channel) to make a final decision regarding PU existence. In practical scenarios, both S-channels and R-channels are contaminated with noise, fading and shadowing effects. Thus, the FC may receive faulty decisions from the CRs, which in turn degrades the overall sensing performance of the cognitive radio networks (CRNs). In this paper, an efficient hard decision CSS with two-stage censoring is proposed for boosting the sensing performance of CRNs against noise uncertainty inherent in the S-channels and erroneous inherent in the R-channels. In the first stage, CRs with low quality R-channels are censored by the FC, hence only CRs with high quality R-channels are selected for the next stage of censoring. In the second stage, the low confident CRs with high noise uncertainty factors of their S-channels are censored by the FC, i.e., the FC selects the candidate CRs with the highest quality R-channels and the lowest noisy S-channels. For boosting the sensing decisions made by the CRs, a double dynamic threshold (DDT) is utilized by each CR based on an estimated value of the noise uncertainty factor of its S-channel. The new detection and false alarm probabilities are evaluated mathematically for the proposed scheme. Moreover, numerical analysis is used to confirm the high potency of the proposed scheme over some existing hard decision CSS schemes.

  • 430.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Osaka University, Japan.
    Hard Decision Cooperative Spectrum Sensing Based on Estimating the Noise Uncertainty Factor2015In: Proceedings - 2015 10th International Conference on Computer Engineering and Systems, ICCES 2015, IEEE, 2015, p. 217-222Conference paper (Refereed)
    Abstract [en]

    Spectrum Sensing (SS) comprises the most important component in Cognitive Radio (CR) systems. Cooperative Spectrum Sensing (CSS) is proposed as an effective approach to improve detection performance in fading environments. This paper introduces an efficient energy detection based hard decision CSS algorithm to alleviate the noise uncertainty effect. In the proposed algorithm, the decision threshold is dynamically switched between two levels based on a prior prediction of the Primary User (PU) activity. The two threshold levels are evaluated using an estimated value of the noise uncertainty factor to maximize the probability of detection and minimize the probability of false alarm. The proposed algorithm is studied theoretically to deduce the enhanced detection and false alarm probabilities. Moreover, simulation analysis is used to confirm the theoretical claims and prove the high potency of the proposed scheme compared to the conventional CSS using different fusion rules.

  • 431.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Osaka University, Japan.
    Improved Cognitive Radio Energy Detection Algorithm Based upon Noise Uncertainty Estimation2014In: National Radio Science Conference, NRSC, Proceedings, IEEE, 2014, p. 107-115Conference paper (Refereed)
    Abstract [en]

    Cognitive Radio (CR) is a regulated technique for opportunistic access of idle resources. In CR, Spectrum sensing is one of its important key functionalities. It is used to sense the unused spectrum in an opportunistic manner. Energy detection constitutes a preferred approach for spectrum sensing in cognitive radio due to its simplicity and applicability. The traditional energy detection technique, which is based upon fixed threshold, is sensitive to noise uncertainty which is unavoidable in practical cases. This noise uncertainty gets the fixed threshold energy detector un-optimized in its performance. In this paper, an efficient energy detector is proposed for optimal CR performance. The proposed scheme is a dynamic threshold energy detection algorithm, in which, two threshold levels are utilized based upon the average energy received from the primary user (PU) during a specified period of observation. Thresholds evaluations are based upon estimating the noise uncertainty factor. These thresholds are used to maximize the probability of detection (Pd) and minimize the probability of false alarm (Pfa). Theoretical analysis and simulation results show the effectiveness of the proposed scheme in comparison to the traditional energy detection method with less increase in complexity.

  • 432.
    Farag, Hossam
    et al.
    Aswan University, Egypt.
    Mohamed, Ehab M.
    Osaka University, Japan.
    Soft Decision Cooperative Spectrum Sensing Based Upon Noise Uncertainty Estimation2015In: 2015 IEEE International Conference on Communication Workshop, ICCW 2015, IEEE, 2015, p. 1623-1628Conference paper (Refereed)
    Abstract [en]

    Spectrum Sensing (SS) constitutes the most critical task in Cognitive Radio ( CR) systems for Primary User (PU) detection. Cooperative Spectrum Sensing (CSS) is introduced to enhance the detection reliability of the PU in fading environments. In this paper, we propose a soft decision based CSS algorithm using energy detection by taking into account the noise uncertainty effect. In the proposed algorithm, two threshold levels are utilized based on predicting the current PU activity, which can be successfully expected using a simple successive averaging process with time. The two threshold levels are evaluated based on estimating the noise uncertainty factor. In addition, they are toggled in a dynamic manner to compensate the noise uncertainty effect and to increase the probability of detection and decrease the probability of false alarm. Theoretical analysis is performed on the proposed algorithm to evaluate its enhanced false alarm and detection probabilities over the conventional soft decision CSS using different combining schemes. In addition, simulation results show the high efficiency of the proposed scheme compared to the conventional soft decision CSS, with high computational complexity enhancements.

  • 433.
    Farag, Hossam
    et al.
    Aswan University, Aswan, Egypt.
    Mohamed, Ehab M.
    Aswan University, Egypt; Osaka University, Japan.
    Soft Decision Cooperative Spectrum Sensing with Noise Uncertainty Reduction2017In: Pervasive and Mobile Computing, ISSN 1574-1192, E-ISSN 1873-1589, Vol. 35, p. 146-164Article in journal (Refereed)
    Abstract [en]

    Cognitive radio (CR) is a potential strategy for opportunistic access of idle resources to solve the conflicts between spectrum scarcity and underutilization. Spectrum sensing (SS) constitutes the most critical part in CR systems since the CR needs to detect the presence of primary signals reliably and quickly. Energy detection (ED) based SS is considered as the most preferable SS technique due to its simplicity and applicability. However, it is influenced by the effect of noise uncertainty which highly degrades its sensing performance. Cooperative spectrum sensing (CSS) is also introduced to mitigate some sensing problems such as multipath fading, shadowing, and hidden node problems. In this paper, we propose an enhanced fusion center (FC) rule for soft decision CSS using ED, which highly alleviates the noise uncertainty effect and enhances the sensing performance of cognitive radio networks (CRNs). In the proposed fusion rule, to increase the probability of detection and decrease the probability of false alarm, two dynamic thresholds are utilized by the FC. These thresholds are toggled based on predicting the current activity of the primary user (PU), and their values are dynamically changed based on estimating the noise uncertainty factor of the collected energy measurements from the CRs. To effectively predict (estimate) the current PU activity (the noise uncertainty factor), simple successive averaging processes over the collected energy measurements (the estimated noise variances) are performed by the FC, respectively. Theoretical analysis is performed on the proposed fusion rule for soft decision CSS to evaluate its enhanced false alarm and detection probabilities using different data combining schemes. Performance evaluations are also investigated to confirm the theoretical claims and to prove the effectiveness of the proposed scheme over the conventional ED based soft decision CSS.

  • 434.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Sisinni, Emiliano
    Brescia University, Brescia, Italy.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Priority-Aware Wireless Fieldbus Protocol for Mixed-Criticality Industrial Wireless Sensor Networks2019In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 19, no 7, p. 2767-2780Article in journal (Refereed)
    Abstract [en]

    Industrial wireless sensor networks are becoming popular for critical monitoring and control applications in industrial automation systems. For such type of applications, providing reliable real-time performance regarding data delivery is considered as a fundamental challenge. The problem becomes more prominent with mixed-criticality systems, where different data flow with different levels of criticality (importance) coexist and characterized by different requirements regarding delay and reliability. In this paper, we propose a wireless fieldbus protocol to enable real-time communication and service differentiation for cluster-based mixed-criticality networks. A process monitoring scenario of plastic extrusion is used to define the protocol requirements and elaborate the working principle of the proposed work. In our proposed protocol, each data flow is scheduled for channel access based on its criticality level using a distributed prioritized medium access mechanism that ensures a guaranteed channel access for the most critical traffic over other traffic types. The performance of the proposed protocol is analyzed analytically using a discrete-time Markov chain model to evaluate the performance in terms of delay and throughput. Moreover, the extensive simulations are conducted to prove the analytical claims and different performance assessments are provided, which also demonstrate the effectiveness of the proposed approach compared with the related existing work.

  • 435.
    Farag, Hossam
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Österberg, Patrik
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    RMA-RP: A Reliable Mobility-Aware Routing Protocol for Industrial IoT Networks2019Conference paper (Refereed)
    Abstract [en]

    Many emerging Industrial Internet of Things (IIoT) applications involve the use of mobile devices, such as sensors and robots in industrial automation scenarios. Movement of mobile sensor nodes causes intermittent connectivity which in turn deteriorates the network performance in terms of packet loss and delay. The Routing Protocol for Low Power and Lossy Networks (RPL) is introduced as the standard routing protocol for IIoT networks. Although RPL constitutes a reliable and energy-efficient solution for static networks, there is no mechanism defined in the RPL standard of how to support routing in mobile IIoT networks. This paper introduces RMA-RP, a reliable mobility-aware routing protocol to support mobile IIoT networks. RMA-RP utilizes a dynamic motion detection mechanism based on the link quality to cope with topology changes by updating next-hop nodes. Moreover, an adaptive timer is introduced to manage the transmission rate of control messages in order to decrease the network overhead and in turn the energy consumption. We evaluate the performance of RMA-RP through extensive simulations in comparison to existing works and the results demonstrate that RMA-RP has at least 17% higher packet delivery ratio and achieves a reduction of 34% and 51% in terms of delay and network overhead, respectively.

  • 436.
    Faria, Gregorio Couto
    et al.
    Stanford University, Instituto de Física de São Carlos (IFSC).
    Duong, Duc Trong
    Stanford University.
    Dahlström, Christina
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Rivnay, Jonathan
    École Nationale Supérieure des Mines de Saint Étienne.
    Malliaras, George
    École Nationale Supérieure des Mines de Saint Étienne.
    Owens, Roisin
    École Nationale Supérieure des Mines de Saint Étienne.
    Salleo, Alberto
    Stanford University.
    Modeling Transient Drain Current Response in Biofunctionalized Organic Electrochemical Transistors2015Conference paper (Other academic)
  • 437.
    Fasth, Tobias
    et al.
    Dept. of Computer and Systems Sciences, Stockholm University, Sweden.
    Larsson, Aron
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Sensitivity Analysis in Portfolio Interval Decision Analysis2013In: FLAIRS 2013 - Proceedings of the 26th International Florida Artificial Intelligence Research Society Conference, 2013, p. 609-614Conference paper (Refereed)
    Abstract [en]

    Techniques enabling decision makers to identify a set ofnon-mutually exclusive projects (or alternatives) constituting a portfolio, while allowing for imprecise information with respect to projects’ benefits, costs, andoverall resource constraints, have emerged as an areaof great applicability. To reach applicability, reasonable and computationally meaningful decision evaluation methods are needed. In this paper, we propose anembedded form of sensitivity analysis for portfolio interval decision analysis building upon the concept of interval contraction. Both a priori sensitivity analysis anda posteriori sensitivity analysis for portfolio interval decision analysis are supported by the approach.

  • 438.
    Fedorov, Igor
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Alqaysi, Hiba
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Placement Strategy of Multi-Camera Volumetric Surveillance System for Activities Monitoring2017In: ICDSC 2017 Proceedings of the 11th International Conference on Distributed Smart Cameras, New York, NY, USA: Association for Computing Machinery (ACM), 2017, Vol. F132201, p. 113-118Conference paper (Refereed)
    Abstract [en]

    The design of multi-camera surveillance system comes with many advantages, for example it facilitates as understanding how flying objects act in a given volume. One possible application is for the observation interaction of birds and calculate their trajectories around wind turbines to create promising systems for preventing bird collisions with turbine blades. However, there are also challenges, such as finding the optimal node placement and camera calibration. To address these challenges we investigated a trade-off between calibration accuracy and node requirements, including resolution, modulation transfer function, field of view and angle baseline. We developed a strategy for camera placement to achieve improved coverage for golden eagle monitoring and tracking. This strategy based on the modified resolution criterion taking into account the contrast function of the camera and the estimation of the base angle between the cameras.

  • 439.
    Fedorov, Igor
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Lawal, Najeem
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Thörnberg, Benny
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Alqaysi, Hiba
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    O'Nils, Mattias
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Towards calibration of outdoor multi-camera visual monitoring system2018In: ACM International Conference Proceeding Series, New York, NY, US: ACM Digital Library, 2018, , p. 6Conference paper (Refereed)
    Abstract [en]

    This paper proposes a method for calibrating of multi-camera systems where no natural reference points exist in the surrounding environment. Monitoring the air space at wind farms is our test case. The goal is to monitor the trajectories of flying birds to prevent them from colliding with rotor blades. Our camera calibration method is based on the observation of a portable artificial reference marker made out of a pulsed light source and a navigation satellite sensor module. The reference marker can determine and communicate its position in the world coordinate system at centimeter precision using navigartion sensors. Our results showed that simultaneous detection of the same marker in several cameras having overlapping field of views allowed us to determine the markers position in 3D world coordinate space with an accuracy of 3-4 cm. These experiments were made in the volume around a wind turbine at distances from cameras to marker within a range of 70 to 90 m.

  • 440.
    Feng, Yuan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Improve Data Quality By Using Dependencies And Regular Expressions2018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The objective of this study has been to answer the question of finding ways to improve the quality of database. There exists a lot of problems of the data stored in the database, like missing or spelling errors. To deal with the dirty data in the database, this study adopts the conditional functional dependencies and regular expressions to detect and correct data. Based on the former studies of data cleaning methods, this study considers the more complex conditions of database and combines the efficient algorithms to deal with the data. The study shows that by using these methods, the database’s quality can be improved and considering the complexity of time and space, there still has a lot of things to do to make the data cleaning process more efficiency.

  • 441.
    Ferrari, P.
    et al.
    University of Brescia, Italy.
    Flammini, A.
    University of Brescia, Italy.
    Rizzi, M.
    University of Brescia, Italy.
    Sisinni, Emiliano
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. University of Brescia, Italy.
    Gidlund, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    On the evaluation of LoRaWAN virtual channels orthogonality for dense distributed systems2017In: 2017 IEEE International Workshop on Measurement and Network (M&N), IEEE, 2017, p. 85-90, article id 8078371Conference paper (Refereed)
    Abstract [en]

    Internet of Things (IoT) aims at collecting data from billions of devices connected altogether. Despite there is no one technology able to cope with all possible scenarios, LPWAN solutions are emerging as viable technologies for implementing private, low-cost cellular like wireless networks. Distributed systems could leverage this approach as a driving technology for services as smart environment sensing, pervasive sensing and soon. In the considered scenario, the capacity of the network is of main importance; even if communication is sporadic for most of the time, an event observed by many nodes results in a huge amount of simultaneous transmissions. Are the IoT technologies usable to this end? In this paper LoRaWAN technology is investigated, with the aim of evaluating the orthogonality of virtual channels permitted by the LoRa physical layer. In particular, measurements demonstrated that overlapping transmissions having the same power at the receiver can be correctly decoded if occurring with different spreading factors, whereas co-spread messages require at least 4ms spacing.

  • 442.
    Ferrari, P.
    et al.
    University of Brescia, Brescia, Italy.
    Sisinni, Emiliano
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. University of Brescia, Brescia, Italy.
    Brandão, D.
    University of São Paulo, São Carlos, Brazil.
    Rocha, M.
    University of São Paulo, São Carlos, Brazil.
    Evaluation of communication latency in industrial IoT applications2017In: 2017 IEEE International Workshop on Measurement and Networking, M and N 2017 - Proceedings, 2017, article id 8078359Conference paper (Refereed)
    Abstract [en]

    The idea of Industry 4.0 includes the concept of Industrial Internet of Things (IIoT) that is the possibility for industrial devices to have Internet connection and share data. Huge amount of data are stored and analyzed in the Cloud to extract meaningful information to be sold as 'services'. Today, many Industry 4.0 scenarios do not require a short latency between data collection and output reaction, but it is expected that short latency services would be seen by the market as a distinctive quality. This paper deals with the estimation of latency in transferring data from the field (where the production takes place) to the Cloud and then back to field. Since IIoT natively refers to worldwide applications, the paper analyzes some cases where interacting nodes are deployed in different continents. The experimental results show that simple solutions based on widely accepted lightweight protocols (e.g. MQTT) and inexpensive industrial grade IoT devices are feasible. From the performance point of view, when using free access Cloud servers, they can achieve round trip latency down to 300 ms with standard deviation of about 20 ms over one-week observation time. 

  • 443.
    Ferrari, Paolo
    et al.
    University of Brescia, Brescia, Italy.
    Flammini, Alessandra
    University of Brescia, Brescia, Italy.
    Rinaldi, Stefano
    University of Brescia, Brescia, Italy.
    Rizzi, Mattia
    University of Brescia, Brescia, Italy.
    Sisinni, Emiliano
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. University of Brescia, Brescia, Italy.
    On the use of LPWAN for EVehicle to grid communication2017In: 2017 AEIT International Annual Conference, IEEE, 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    The expected diffusion of EVehicles (EVs) to limit the impact of fossil fuel on mobility is going to cause severe issues to the management of electric grid. A large number of charging stations is going to be installed on the power grid to support EVs. Each of the charging station could require more than 100 kW from the grid. The grid consumption is unpredictable and it depends from the need of EVs in the neighborhood. The impact of the EV on the power grid can be limited by the proper exploitation of Vehicle to Grid communication (V2G). The advent of Low Power Wide Area Network (LPWAN) promoted by Internet Of Things applications offers new opportunity for wireless communications. In this work, an example of such a technology (the LoRaWAN solution) is tested in a real-world scenario as a candidate for EV to grid communications. The experimental results highlight as LoRaWAN technology can be used to cover an area with a radius under 2 km, in an urban environment. At this distance, the Received Signal Strength Indicator (RSSI) is about -117 dBm. Such a result demonstrates the feasibility of the proposed approach.

  • 444.
    Flammini, Alessandro
    et al.
    University of Brescia, Italy.
    Sisinni, Emiliano
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology. University of Brescia, Italy.
    Tramarin, Federico
    National Research Council of Italy.
    IEEE 802.11s performance assessment: From simulations to real-world experiments2017In: 2017 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), IEEE, 2017, p. 1-6Conference paper (Refereed)
    Abstract [en]

    In this work we aim at providing an initial analysis of the IEEE802.11s amendment that introduced support for mesh networking to Wireless LAN specifications. Indeed, there has been an increasing interest in the adoption of IEEE 802.11-based wireless systems also in the field of Distributed Measurement Systems (DMSs). Nonetheless, in such a scenario it is necessary to investigate the obtainable performance, in terms of latency, reliability and throughput. Toward this goal, we firstly considered the public available ns-3 IEEE 802.11s model, highlighting some details of the implemented design and also showing some of the unsupported features and open issues. Subsequently, we also leveraged on the mac80211 network emulation features embedded within the Linux kernel to test the mesh extensions included in Linux systems. Finally, using low-cost COTS hardware, exploiting the same mesh stack, we developed a real-world test bench allowing an experimental performance assessment. Results obtained from the presented setups are thus compared, and some open issues are finally discussed.

  • 445.
    Flodin, Anton
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Leerec: A scalable product recommendation engine suitable for transaction data.2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    We are currently living in the Internet of Things (IoT) era, which involves devices that are connected to Internet and are communicating with each other. Each year, the number of devices increases rapidly, which result in rapid growth of data that is generated. This large amount of data is sometimes titled as Big Data, which is generated from different sources, such as log data of user behavior. These log files can be collected and analyzed in different ways, such as creating product recommendations. Product recommendations have been around since the late 90s, when the amount of data collected were not at the same level as it is today. The aim of this thesis has been to investigating methods to process and create product recommendations to see how well they are adapted for Big Data. This has been accomplished by three theory studies on how to process user events, how to make the product recommendation algorithm called collaborative filtering scalable and finally how to convert implicit feedback to explicit feedback (ratings).

    This resulted in a recommendation engine consisting of Apache Spark as the data processing system, which had three functions: read multiple log files and concatenate log files for each month, parsing the log files of the user events to create explicit ratings from the transactions and create four types of recommendations. The NoSQL database MongoDB was chosen as the database to store the different types of product recommendations that was created. To be able to get the recommendations from the recommendation engine and the database, a REST API was implemented which can be used by any third-party. What can be concluded from the results of this thesis work is that the system that was implemented is partial scalable. This means that Apache Spark was scalable for both concatenating files, parse and create ratings and also create the recommendations using the ALS method. However, MongoDB was shown to be not scalable when managing more than 100 concurrent requests. Future work involves making the recommendation engine distributed in a multi-node cluster to utilize the parallelization of Apache Spark. Other recommendations include considering other NoSQL databases that might be more scalable than MongoDB.

  • 446.
    Forsberg, Viviane
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. KTH, Stockholm; Wallenberg Wood Science Centre, Stockholm.
    Mašlík, Jan
    Tomas Bata University in Zlín, Zlín, Czech Republic.
    Norgren, Magnus
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Electronic performance of printed PEDOT:PSS lines correlated to the physical and chemical properties of coated inkjet papers2019In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 9, no 41, p. 23925-23938Article in journal (Refereed)
    Abstract [en]

    PEDOT:PSS organic printed electronics chemical interactions with the ink-receiving layer (IRL) of monopolar inkjet paper substrates and coating color composition were evaluated through Raman spectroscopy mapping in Z (depth) and (XY) direction, Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray spectroscopy (EDS). Other evaluated properties of the IRLs were pore size distribution (PSD), surface roughness, ink de-wetting, surface energy and the impact of such characteristics on the electronics performance of the printed layers. Resin-coated inkjet papers were compared to a multilayer coated paper substrate that also contained an IRL but did not contain the plastic polyethylene (PE) resin layer. This substrate showed better electronic performance (i.e., lower sheet resistance), which we attributed to the inert coating composition, higher surface roughness and higher polarity of the surface which influenced the de-wetting of the ink. The novelty is that this substrate was rougher and with somewhat lower printing quality but with better electronic performance and the advantage of not having PE in their composite structure, which favors recycling. © 2019 The Royal Society of Chemistry.

  • 447.
    Forsman, Björn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Zhang, Wennan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Alkali Metal Release During Rapid Pyrolysis of Fuel Blends Containing 2005In: Proceedings. 14th European conference and technology exhibition biomass for energy industry and climate protection, Paris, Oct. 2005, 2005Conference paper (Other scientific)
    Abstract [en]

    In the present study the influence of different fuel blends and additives on the release of gaseous alkali metals during rapid pyrolysis of biomass has been investigated. A single particle reactor has been used together with a molecular beam mass spectrometer (MBMS) to study the release of gaseous alkali-containing emissions during pyrolysis. A hot platinum filament was used as the ionization source and alkali-containing compounds that hit the hot filament dissociate and alkali ions leave the Pt -filament and are detected in the MBMS. The fuels used were wood (spruce) and wood waste. The additives included peat, different sewage sludge samples, sludge from the pulp and paper industry and fly ash from co-combusted wood and sewage sludge. Experimental results show time resolved mass loss curves of biomass particles during rapid pyrolysis combined with released amounts of sodium (Na) and potassium (K). The results indicate that the new combined instrument successfully detects gaseous alkali metals, and a difference in the release of Na and K during pyrolysis due to the use of the additives is observed. Additives consisting of sewage sludge ash reduced the release of alkali, probably due to the presence of mullite in the ash together with the sorption effect of fine particles.

  • 448.
    Forsman, Björn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Zhang, Wennan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Svenson, J.
    Pettersson, J.B.C.
    ALKALI METAL RELEASE DURING RAPID PYROLYSIS OF FUEL BLENDS CONTAINING BIOMASS AND DIFFERENT ADDITIVES.2005In: Proceedings of the 14th European Biomass Conference: Biomass for Energy, Industry and Climate Protection, 2005Conference paper (Other academic)
  • 449.
    Forsström, Stefan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Enabling fully distributed global services on the Internet-of Things2014Doctoral thesis, comprehensive summary (Other academic)
  • 450.
    Forsström, Stefan
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Kanter, Theo
    Department of Computer and System Sciences, Stockholm University, Kista, SE-164 40, Sweden .
    Continuously Changing Information on a Global Scale and its Impact for the Internet-of-Things2014In: Mobile Networks and Applications , ISSN 1383-469X, E-ISSN 1572-8153, Vol. 19, no 1, p. 33-44Article in journal (Refereed)
    Abstract [en]

    This article analyzes the challenges of supportingcontinual changes of context information in Internetof-Things applications. These applications require aconstant flow of continuously changing information fromsensor based sources in order to ensure a high quality-ofexperience.However, an uncontrolled flow between sourcesand sinks on a global scale wastes resources, such ascomputational power, communication bandwidth, andbattery time. In response to these challenges we presenta general approach which focuses on four layers wherewe provide a proposed solution to each layer. We haverealized the general model into a proof-of-concept implementationrunning on devices with limited resources,where we can moderate the information exchange basedon relevance and sought after quality-of-experience bythe applications. In conclusion, we evaluate our solutionand present a summary of our experiences regardingthe impact of continuously changing information on theInternet-of-Things.

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