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  • 251.
    Beek, Jaap van de
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    White Paper for Research Beyond 5G2015Rapport (Annet vitenskapelig)
  • 252.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Berggren, Fredrik
    Huawei Technologies Sweden.
    EVM-constrained OFDM precoding for reduction of out-of-band emission2009Inngår i: 2009 IEEE 70th Vehicular Technology Conference - Fall: VTC 2009-Fall; Anchorage, Alaska, USA, 20 - 23 September 2009, Piscataway, NJ: IEEE Communications Society, 2009, artikkel-id 5378740Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This contribution addresses the potential of N-continuous OFDM signals in systems where the receiver is unaware of the transmitter precoder operation. First, we present a memoryless precoder rendering N-continuous signals. Second, we evaluate the effect on the magnitude of the emitted signal's error-vector. Third, we present three ad hoc precoders designed under a hard constraint on the allowed EVM still significantly suppressing out-of-band power

  • 253.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Bollen, Math
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Larsson, Anders
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Eriksson, Mats
    Arctos Labs Scandinavia AB.
    Can Solar Power Help Providing Broadband Cellular Coverage in Extreme-Rural Sweden?2016Rapport (Annet vitenskapelig)
  • 254.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Luleå tekniska universitet, Lund Institute of Technology, Department of Applied Electronics.
    Boucheret, Marie-Laure
    Ecole Nationale Supérieure des Télécommunications.
    Arenas, Julia Martinez
    Ecole National Superieure de Telecommunications, Site de Toulouse, Ericsson Radio Systems AB.
    Landström, Daniel
    Department of Electrosciences, Lund Institute of Technology, Luleå tekniska universitet, Department of Applied Electronics, Lund University.
    Ödling, Per
    Luleå tekniska universitet.
    Östberg, Christer
    Ericsson Mobile Communication AB, Telia Research AB, Telia Research.
    Wahlqvist, Mattias
    Telia Research AB, Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet, ArrayComm, San Jose.
    A time and frequency synchronization scheme for multiuser OFDM1998Rapport (Fagfellevurdert)
  • 255.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Lunds universitet.
    Boucheret, Marie-Laure
    Landström, Daniel
    Arenas, Julia Martiez
    Ödling, Per
    Östberg, Christer
    Wahlqvist, Mattias
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    A time and frequency synchronization scheme for multiuser OFDM1999Inngår i: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 17, nr 11, s. 1900-1914Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present a multiuser synchronization scheme for tracking the mobile's uplink time and frequency offsets. It uses the redundancy introduced by the cyclic prefix and does not need additional pilots. We show performance results of an orthogonal frequency division multiplexing (OFDM)-based radio interface based on universal mobile telecommunication system (UMTS) parameters. For a UMTS-typical mobile channel environment, the performance of a coherent system employing the scheme is virtually indistinguishable from the performance of a perfectly synchronized system. In a differentially modulated system, synchronization errors decrease the system performance by about 0.7 dB compared to a perfectly synchronized system. Index Terms - Communication system, delay estimation, frequency estimation, multicarrier, multiuser system, orthogonal frequency division multiplexing (OFDM), synchronization, universal mobile telecommunication system (UMTS).

  • 256.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Boucheret, Marie-Laure
    Landström, Daniel
    Luleå tekniska universitet.
    Arenas, Julia Martinez
    Ödling, Per
    Luleå tekniska universitet.
    On synchronization in an OFDM based UMTS proposal1997Inngår i: Emerging techniques for communication terminals: proceedings of COST 254 Workshop, Toulouse, France, 07-09 July 1997., Toulouse: INP-ENSEEIHT , 1997, s. 315-320Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this paper we discuss three signal models and respective Maximum Likelihood estimators of time and frequency osets. We consider implementation structures for these estimators. Furthermore, we discuss the applicability of these estimators and some variants in a proposal for the future UMTS.

  • 257.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Boucheret, Marie-Laure
    Landström, Daniel
    Luleå tekniska universitet.
    Arenas, Julia Martinez
    Ödling, Per
    Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Three non-pilot-based time and frequency estimators for OFDM1998Rapport (Annet vitenskapelig)
    Abstract [en]

    Time-domain Maximum-Likelihood (ML) estimators of time and frequency o¤sets are derived for three Orthogonal Frequency Division Multiplexing (OFDM) signal models: a pulse-shaped one-shot OFDM signal, a stream of multiple OFDM signals and an OFDM signal in a dispersive channel environment. We then develop structures to simplify their implementation. Simulation results show the relative performance and strengths of each of these three estimators.

  • 258.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Boucheret, Marie-Laure
    Ecole National Superieure de Telecommunications, Site de Toulouse.
    Landström, Daniel
    Luleå tekniska universitet.
    Arenas, Julia Martinez
    Ecole National Superieure de Telecommunications, Site de Toulouse.
    Ödling, Per
    Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Östberg, Christer
    Ericsson Mobile Communication AB.
    Wahlqvist, Mattias
    Telia Research AB.
    Synchronization of a TDMA-OFDM frequency hopping system1998Inngår i: Pathway to a global wireless revolution: VTC '98, 48th IEEE Vehicular Technology Conference, Westin Hotel, Ottawa, Canada, 18 - 21 May 1998, Piscataway, NJ: IEEE Communications Society, 1998, Vol. 2, s. 1290-1294Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we present a Time Division Multiple Access-Orthogonal Frequency Division Multiplexing (TDMA-OFDM)-based radio interface proposal for the Universal Mobile Telecommunication System (UMTS). We focus on synchronization and present an implementable algorithm for the tracking of the mobiles' time and frequency offsets at the base station in the uplink. This algorithm is based on recently developed estimation methods that use redundancy introduced by the cyclic prefix. A modified Maximum Likelihood (ML) estimator for the Additive White Gaussian Noise (AWGN) channel is used to meet both implementational requirements and performance requirements for frequency-selective fading multiuser environments. Simulation results for a typical UMTS mobile channel environment show that the uncoded symbol error rate of a coherently modulated system using our synchronization scheme is virtually indistinguishable from that of a system with no time and frequency offset.

  • 259.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Eriksson, Håkan
    Luleå tekniska universitet.
    Gustavsson, Jan-Olov
    Luleå tekniska universitet.
    Olsson, Lennart
    Luleå tekniska universitet.
    MMSE estimation of arrival time with application to ultrasonic signals1993Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper deals with arrival time estimation of a narrow-band signal disturbed by white gaussian noise. In order to estimate the distance between a transmitting source and a reflecting target an estimator, based on the criterion of minimum mean square error (MMSE), is investigated. The MMSE-estimator is implemented in an experimental ultrasound pulse-echo system, and results of comparative simulations between the MAP-estimator and the MMSE-estimator are given. The results are compared to the theoretical Weiss-Weinstein lower bound. As expected, the MMSE-estimator has smaller mean square error than the MAP-estimator. For high SNRs, however, the mean square error obtained by the MAP-estimator manages to approach that of the MMSE-estimator. Other di®erences between the two estimators are revealed in additional experiments in which the range estimates are used to generate 3-dimensional surface pictures.

  • 260.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Landström, Daniel
    Wahlqvist, Mattias
    Telia Research.
    Ödling, Per
    Östberg, Christer
    A conceptual study of OFDM-based multiple access schemes: Part 4: Tracking of time and frequency offset1996Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper is part of a conceptual study of a multiuser OFDM system. In previous reports we have examined requirements for the air interface and presented uncoded performance (in terms of bit error rate) for the uplink of such systems. In this report we adopt the user allocation structure from the previous parts of the study and examine the role of channel coding. We present performance simulations that illustrate the effects of a convolutional code exploiting channel diversity, and channel estimator performance exploiting the channel correlation.

  • 261.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Edfors, Ove
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Wahlqvist, Mattias
    Telia Research.
    Östberg, Christer
    Telia Research.
    A conceptual study of OFDM-based multiple access schemes: Part 2: Channel estimation in the uplink1996Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper deals with the design of channel estimators in the uplink of an OFDM based multi-user system. First, we propose a user allocation scheme that is based on the aim to use the correlation of the radio channel for channel estimation purposes. Further, we present the linear MMSE channel estimator based on a few pilot tones. We present an error analysis that proves valuable in the evaluation of linear channel estimators under mismatch. Finally, we present some results on the design of linear channel estimators and pilot patterns, showing by means of examplesthe importance of careful pilot positioning.

  • 262.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Edfors, Ove
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Wahlqvist, Mattias
    Tellia Research.
    Östberg, Christer
    Telia Research.
    A conceptual study of OFDM-based multiple access schemes: Part 3: Performance evaluation of a coded system1996Rapport (Annet vitenskapelig)
    Abstract [en]

    This paper is part of a conceptual study of a multiuser OFDM system. In previous reports we have examined requirements for the air interface and presented uncoded performance (in terms of bit error rate) for the uplink of such systems. In this report we adopt the user allocation structure from the previous parts of the study and examine the role of channel coding. We present performance simulations that illustrate the effects of a convolutional code exploiting channel diversity, and channel estimator performance exploiting the channel correlation.

  • 263.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Edfors, Ove
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Wahlwvist, Mattias
    Telia Research AB.
    Östberg, Christer
    Telia Research AB.
    Channel estimation in the uplink of an OFDM system1996Inngår i: Proceedings of Nordic Radio Symposium: NRS '96, Lund, Sweden, August 1996, 1996, s. 32-35Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper deals with the design of linear pilot based channel estimators in the uplink of an OFDM-based multiuser system, We evaluate such estimators and pilot patterns, showing by means of examples the importance of careful pilot positioning.

  • 264.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Edfors, Ove
    Luleå tekniska universitet.
    Sandell, Magnus
    Luleå tekniska universitet.
    Wilson, Sarah Kate
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    On channel estimation in OFDM systems1995Inngår i: Countdown to the wireless twenty-first century: 1995 IEEE 45th Vehicular Technology Conference, Chicago, Illinois, USA, July 25 - 28, 1995, Piscataway, NJ: IEEE Communications Society, 1995, Vol. 2, s. 815-819Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The use of multi-amplitude signaling schemes in wireless OFDM systems requires the tracking of the fading radio channel. The paper addresses channel estimation based on time-domain channel statistics. Using a general model for a slowly fading channel, the authors present the MMSE and LS estimators and a method for modifications compromising between complexity and performance. The symbol error rate for a 18-QAM system is presented by means of simulation results. Depending upon estimator complexity, up to 4 dB in SNR can be gained over the LS estimator

  • 265. Beek, Jaap van de
    et al.
    Lidström, Erik
    Huawei Technologies, Stockholm.
    Cai, Tao
    Huawei Technologies, Stockholm.
    Xie, Yong
    Huawei Technologies, Chengdu.
    Rakovic, Valentin
    Ss. Cyril and Methodius University, Skopje.
    Atanasovski, Vladimir M.
    Ss. Cyril and Methodius University, Skopje.
    Gavrilovska, Liljana M.
    Ss. Cyril and Methodius University, Skopje.
    Rihijärvi, Janne
    RWTH Aachen University.
    Mähönen, Petri H.
    RWTH Aachen University.
    Dejonghe, Antoine
    IMEC, Leuven.
    Wesemael, Peter Van
    IMEC, Leuven.
    Desmet, Mattias
    IMEC, Leuven.
    REM-enabled opportunistic LTE in the TV band2012Inngår i: 2012 IEEE International Symposium on Dynamic Spectrum Access Networks (DYSPAN 2012): Bellevue, Washington, USA, 16 - 19 October 2012, Piscataway, NJ: IEEE Communications Society, 2012, s. 272-273Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this demonstration paper we describe a prototype of an LTE system deployment that opportunistically exploits the spectral white spaces in the upper UHF TV bands, intelligently guided in its spectum access by a radio environment map (REM). The architecture is modular in the sense that interfaces are generic and minimal. In the proposed demo we will illustrate how information of primary transmitters and other secondary transmitters as well as estimates of the radio field strength over frequency, time and space can be made available and exploited by a secondary TDD-LTE base station to make judicious decisions on its spectral occupation.

  • 266.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Popović, Branislav M.
    Huawei Technologies Sweden.
    Benefits of modulation diversity in turbo-coded OFDM systems2004Inngår i: IEEE Vehicular Technology Conference (VTC) Proceedings, ISSN 1550-2252, Vol. 59, nr 2, s. 929-933Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper we show that the use of modulation diversity provides gains to punctured, turbo-coded OFDM systems. For an OFDM transmission scenario based on the downlink of the 3GPP standard for mobile communications, we show that the order-2 modulation diversity observed for the raw bit-error rate transfers to the block-error rate in a number of investigated channel environments. We demonstrate gains of up to 2.5 dB depending on the puncturing rate of the scheme and the particular channel characteristics. Alternatively, for schemes with higher puncturing rates, 2 or 3 turbo decoder iterations suffice to achieve the same performance as achieved by 8 decoder iterations in a regular transmission

  • 267.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Popović, Branislav M.
    Huawei Technologies Sweden.
    Multiple access with low-density signatures2009Inngår i: GLOBECOM 2009: 2009 IEEE Global Telecommunications Conference; Honolulu, Hawaii, USA, 30 November - 4 December 2009, Piscataway, NJ: IEEE Communications Society, 2009, artikkel-id 5425243Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present sets of spreading sequences that are specifically designed to suit a belief-propagation multiuser detection structure, recently presented for overloaded system scenarios. On one hand, our sequences are of the low-density type; on the other their distance spectrum properties ensure good performance in AWGN channels. Simulations results for raw and coded bit-error probability indicate that significant performance gain is achieved over random sequences and that the loss compared to the single-user bound can be kept small.

  • 268. Beek, Jaap van de
    et al.
    Rihijärvi, Janne
    Institute for Networked Systems, RWTH Aachen University.
    Achtzehn, Andreas
    Institute for Networked Systems, RWTH Aachen University.
    Mähönen, Petri H.
    Institute for Networked Systems, RWTH Aachen University.
    TV white space in Europe2012Inngår i: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 11, nr 2, s. 178-188Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we study the availability of TV white spaces in Europe. Specifically, we focus on the 470-790 MHz UHF band, which will predominantly remain in use for TV broadcasting after the analog-to-digital switch-over and the assignment of the 800 MHz band to licensed services have been completed. The expected number of unused, available TV channels in any location of the 11 countries we studied is 56 percent when we adopt the statistical channel model of the ITU-R. Similarly, a person residing in these countries can expect to enjoy 49 percent unused TV channels. If, in addition, restrictions apply to the use of adjacent TV channels, these numbers reduce to 25 and 18 percent, respectively. These figures are significantly smaller than those recently reported for the United States. We also study how these results change when we use the Longley-Rice irregular terrain model instead. We show that while the overall expected availability of white spaces is essentially the same, the local variability of the available spectrum shows significant changes. This underlines the importance of using appropriate system models before making far-reaching conclusions.

  • 269.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Rihijärvi, Janne
    RWTH Aachen University.
    Achtzehn, Andreas
    Institute for Networked Systems, RWTH Aachen University.
    Mähönen, Petri H.
    RWTH Aachen University.
    UHF white space in Europe: A quantitative study into the potential of the 470-790 MHz band2011Inngår i: 2011 IEEE Symposium on New Frontiers in Dynamic Spectrum Access Networks (DySPAN 2011): Aachen, Germany, 3 - 6 May, 2011, Piscataway, NJ: IEEE Communications Society, 2011, s. 1-9, artikkel-id 5936207Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper we study the availability of TV white spaces in Europe. We focus specifically on the 470-790 MHz UHF band that is still predominantly used for TV broadcasting also after the digital dividend (frequency reallocation as part of transition to digital TV), which has taken place or is ongoing in several European countries. We find that in the countries used in our studies, approximately 56% of the TV channels are unused, when averaged over the whole geographic area. Considering the average over population instead of geographic area reduced the mean available white space to 49% of the channels. Our results confirm quantitatively the often stated expectation that there are indeed fewer white spaces available in Europe compared to, for example, the United States. We also study the influence of different modeling assumptions on our results, especially focusing on the impact of the choice of propagation model. Our results show that changing from statistical ITU-R model to the Longley-Rice irregular terrain model does not cause a major change in the overall estimated availability of white spaces. However, changing the propagation model can significantly affect especially the local variability of the estimated availability of spectrum. This underlines the importance of using right system models in various studies before making too far-reaching conclusions

  • 270. Beek, Jaap van de
    et al.
    Rihijärvi, Janne
    RWTH Aachen University.
    Mähönen, Petri H.
    RWTH Aachen University.
    Intrinsic challenges (and opportunities) to deploy LTE in Europe's TV white spaces2012Inngår i: 2012 Future Network & Mobile Summit (FutureNetw 2012): Berlin, Germany, 4 - 6 July 2012, Piscataway, NJ: IEEE Communications Society, 2012, artikkel-id 6294241Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This contribution presents four business challenges associated with a potential secondary use of European TV white spaces by LTE networks. Based on a quantitative study for 11 representative European countries, we show that Europe's TV white spaces are relatively scarce, diminishing, spatially scattered and heterogeneous, as well as rural in nature. These intrinsic characteristics of the spectrum have implications for the exploitation scenarios by secondary LTE networks that regularly appear as promising use cases. We discuss these implications relation to three LTE use case scenarios: femtocell deployments, rural coverage deployments, and LTE broadcasting/ multicasting deployments

  • 271.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    ML estimation of time and frequency offset in OFDM systems1997Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 45, nr 7, s. 1800-1805Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We present the joint likelihood (ML) symbol-time and carrier-frequency offset estimator in orthogonal frequency-division multiplexing (OFDM) systems. Redundant information contained within the cyclic prefix enables this estimation without additional pilots. Simulations show that the frequency estimator may be used in tracking mode and the time estimator in an acquisition mode.

  • 272.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    ML estimation of timing and frequency offset in multicarrier systems1996Rapport (Annet vitenskapelig)
    Abstract [en]

    In this paper, we present a novel data-based method for simultaneous Maximum Likelihood (ML) symbol and carrier-frequency offset estimation in Orthogonal frequency division multiplexing (OFDM) systems. Statistical properties introduced by the cyclic (OFDM) systems. Statistical properties introduced by the cyclic prefix, a guard space between OFDM symbols, provide su±cient information about the unknown parameters. It is shown that the redundancy introduced by this cyclic prefix allows the estimation to be performed without additional pilots. Simulations show that the performance of the frequency estimator is applicable in a tracking mode while the timing estimation can be used in an acquisition mode.

  • 273.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    On synchronization in OFDM systems using the cyclic prefix1996Inngår i: Proceedings of the 1996 SNRV and NUTEK Conference on Radio Sciences and Telecommunications in Luleå and Kiruna June 3-6, 1996: RVK 96 / [ed] Lars H. Zetterberg, Luleå: Luleå tekniska universitet, 1996, s. 663-667Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, we present a data-based method for simultaneous Maximum Likelihood (ML) symbol timing and carrier-frequency offset estimation in Orthogonal frequency-division multiplexing (OFDM) systems. The cyclic extension, a guardspace preceding OFDM frames, is of decisive importance for this method. It is shown that the redundancy introduced by this cyclic extension allows the estimation to be performed without additional pilots. Simulations show that the performance of the frequency estimator is usable in a tracking mode while the timing estimation can be used in an acquisition mode.

  • 274.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per-Ola
    Luleå tekniska universitet.
    ML estimation of time and frequecy offset in OFDM systems1998Inngår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 45, nr 7, s. 1800-1805Artikkel i tidsskrift (Fagfellevurdert)
  • 275.
    Beek, Jaap van de
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Sandell, Magnus
    Luleå tekniska universitet.
    Isaksson, Mikael
    Telia Research AB.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Low-complex frame synchronization in OFDM systems1995Inngår i: Gateway to the 21st century : record: 1995 Fourth IEEE International Conference on Universal Personal Communications, Meiji Kinenkan, Tokyo, Japan, November 6 - 10, 1995, Piscataway, NJ: IEEE Communications Society, 1995, s. 982-986Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Orthogonal frequency-division multiplexing (OFDM) systems have gained an increased interest due to their use in wireless applications such as mobile communication systems. A novel data-based frame synchronization method for OFDM-systems is presented. OFDM frames are shown to contain sufficient information to synchronize a system without the use of pilots. The cyclic extension, preceding OFDM frames, is of decisive importance for this method. Based on only the sign bits of the in-phase and the quadrature components of the received OFDM signal, the maximum likelihood solution is derived. This solution basically consists of a correlator, a moving sum and a peak detector. The stability of the generated frame-clock is improved significantly by averaging over a few number of frames. Simulations show that this low-complex, averaging method can be used to synchronize an OFDM system on twisted pair copper wires and in slowly fading radio channels

  • 276. Beek, Jaap van de
    et al.
    Tao, Cai
    Huawei Technologies Sweden.
    Grimoud, Sébastien
    Orange Labs, Telecom R and D, Issy-les-Moulineaux.
    Sayrac, Berna
    Orange Labs, Telecom R and D, Issy-les-Moulineaux.
    Mähönen, Petri H.
    Rheinisch-Westfälische Technische Hochschule Aachen, Institute for Networked.
    Nadreddine, Jad
    Rheinisch-Westfälische Technische Hochschule Aachen, Institute for Networked.
    Rihijärvi, Janne
    Rheinisch-Westfälische Technische Hochschule Aachen, Institute for Networked.
    How a layered rem architecture brings cognition to today's mobile networks2012Inngår i: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 19, nr 4, s. 17-24Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this article, we present a layered radio environment map architecture along with its applications to the self-organizing network functionalities of heterogeneous LTE radio access networks comprising macrocells and femtocells. In this architecture, the functional blocks reappear with different spatial and temporal granularity at different architectural layers. Although the radio environment map is one of the key promising technologies to enable future cognitive radio networks, it can be already applied to provide limited cognitive capabilities to today's commercial networks too. We explain why, and show how, this architecture can support today??s LTE self-organizing network functions like automatic neighbor relation and minimization of drive tests, and also allow the smooth introduction of new radio access technologies through refarming. We also demonstrate some of the quantitative benefits adopting radio environment map technologies can bring using the minimization of drive tests as an example.

  • 277. Bengtsson, Daniel
    et al.
    Deutgren, Petra
    Grip, Niklas
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Isaksson, Mikael
    Olsson, Lennart
    Luleå tekniska universitet.
    Sjöberg, Frank
    Luleå tekniska universitet.
    Öhman, Hans
    Zipper performance when mixing ADSL and VDSL in terms of reach and capacity1997Rapport (Annet vitenskapelig)
    Abstract [en]

    In this contribution we have examined how the maximum reach vary at different bit rates on a VDSL system, when different numbers of ADSL and VDSL systems share the same binder. In this context it is concluded that when using the Zipper duplex scheme, VDSL can coexist with ADSL in the same binder without a significant degradation in reach. Further, it is shown that the Zipper duplex scheme secure that ADSL is not disturbed by NEXT from VDSL The Zipper performance has also been compared with both a TDD proposal and a FDD proposal. The results from this comparison shows that Zipper outperforms FDD and TDD in terms of extended reach at all studied mixes of ADSL and VDSL sharing the same binder. For example with a moderate number (5) of ADSL disturbers, the Zipper reach is 150 meters longer than for TDD, and is 350 meters longer than for FDD when studying the medium range asymmetrical bit rate (26:3.2 Mbps).

  • 278.
    Bengtsson, Daniel
    et al.
    Luleå tekniska universitet.
    Landström, Daniel
    Luleå tekniska universitet.
    Ödlling, Per
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Trellis coding in a discrete multitone modulation system1996Inngår i: Proceedings of the 1996 SNRV and NUTEK Conference on Radio Sciences and Telecommunications in Luleå and Kiruna June 3-6, 1996: RVK 96 / [ed] Lars H. Zetterberg, Luleå: Luleå tekniska universitet, 1996, s. 668-672Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Discrete Multitone (DMT) modulation is a multicarrier technique which makes efficient use of the channel, maximizing the throughput by sending different numbers of bits on different subchannels. The number of bits on each subchannel depends on the Signal-to-Noise Ratio of the subchannel. The performance of a DMT system can be further increased by using powerful coding techniques. This paper investigates an implementation of trellis coded modulation in a DMT system intended for transmission over short copper cables, less than 1000m. We suggested trellis code is Wei's 4-dimensional 16-state coder combined with trellis shaping. A single encoder is used which codes across the tones of each DMT-symbol. At a bit error probability of 10-7, the suggested code gains 4-5 dB over uncoded transmission.

  • 279.
    Berezovskaya, Yulia
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Yang, Chen-Wei
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Mousavi, Arash
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    Zhang, Xiaojing
    Vyatkin, Valeriy
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Datavetenskap.
    A hybrid fault detection and diagnosis method in server rooms’ cooling systems2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Data centers as all complex systems are prone to faults, and cost of them can be very high. This paper is focused on detecting the faults in the cooling systems, in particular on local fans level. In the paper, a hybrid approach is proposed. In the approach a model is used as substitute of the real system to generate dataset containing records of both normal and fault cases. On the generated data, machine learning algorithm or ensemble of algorithms are selected and trained to detect the faults. To demonstrate the approach, the rack model of real data center is created, and reliability of the model is shown. Using the model, the dataset with normal as well as abnormal records of data is generated. To detect faults of local fans, simple classifiers are built for all pairs: a local fan – a processor unit. Classifiers are trained on one part of generated data (training data), and then their accuracy is estimated on another part of generated data (test data). A real-time fault detection system is built based on the classifiers. The rack model is used as the substitute of the real plant to check operability of the system.

  • 280.
    Berg, Sven
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Jonsén, Pär
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Häggblad, Hans-Åke
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Carlson, Johan E.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    High pressure characterization and modelling of CaCO3 powder mix in the Bridgman anvil apparatus2012Inngår i: High Pressure Research, ISSN 0895-7959, E-ISSN 1477-2299, Vol. 32, nr 4, s. 490-508Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    For investigating high pressure sintering processes, numerical models can be used. This will demand material models which give realistic mechanical response throughout the whole parameter space of the actual process. As the pressures become higher, the material density approaches its full theoretical value and the elastic part of the material properties becomes increasingly important. In this investigation, Poisson's ratio was determined using ultrasonic pulse-echo measurements. A new elastic model and an improved plasticity model were implemented into a user-defined material subroutine in a finite element (FE) code. To experimentally investigate the load displacement response and pressure distribution in powder compacts during pressing, a pressure instrumented Bridgman anvil apparatus was used. Validation of the FE model was conducted against experimental data from pressing experiments using two different start densities. The results show that the simulation model is indeed capable of reproducing load–thickness curves and pressure profiles reasonable close to the experimental curves.

  • 281.
    Berglund, Tomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Estimating geometric primitives using 3D range data1999Rapport (Annet vitenskapelig)
    Abstract [en]

    Master's Thesis at the Department of Mathematics and at the Division of Robotics at the Department of Computer Science and Electrical Engineering, Luleå University of Technology, Sweden

  • 282.
    Berglund, Tomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Path-planning with obstacle-avoiding minimum curvature variation B-splines2003Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    We study the general problem of computing an obstacle-avoiding path that, for a prescribed weight, minimizes the weighted sum of a smoothness measure and a safety measure of the path. We consider planar curvature-continuous paths, that are functions on an interval of a room axis, for a point-size vehicle amidst obstacles. The obstacles are two disjoint continuous functions on the same interval. A path is found as a minimizer of the weighted sum of two costs, namely 1) the integral of the square of arc- length derivative of curvature along the path (smoothness), and 2) the distance in L2 norm between the path and the point-wise arithmetic mean of the obstacles (safety). We formulate a variant of this problem in which we restrict the path to be a B-spline function and the obstacles to be piece-wise linear functions. Through implementations, we demonstrate that it is possible to compute paths, for different choices of weights, and use them in practical industrial applications, in our case for use by the ore transport vehicles operated by the Swedish mining company Luossavaara-Kiirunavaara AB (LKAB). Assuming that the constraint set is non-empty, we show that, if only safety is considered, this problem is trivially solved. We also show that properties of the problem, for an arbitrary weight, can be studied by investigating the problem when only smoothness is considered. The uniqueness of the solution is studied by the convexity properties of the problem. We prove that the convexity properties of the problem are preserved due to a scaling and translation of the knot sequence defining the B-spline. Furthermore, we prove that a convexity investigation of the problem amounts to investigating the convexity properties of an unconstrained variant of the problem. An empirical investigation of the problem indicates that it has one unique solution. When only smoothness is considered, the approximation properties of a B-spline solution are investigated. We prove that, if there exists a sequence of B-spline minimizers that converge to a path as the number of B-spline basis functions tends to infinity, then this path is a solution to the general problem. We provide an example of such a converging sequence.

  • 283.
    Bergmann, Matthias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Topography of the Chittagong (Bangladesh)shoreline: a combined approach withremote sensing and in situ observations2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In this thesis I present the algorithms and methods used to extract a shoreline from remote sensing data (i.e. satellite imagery) and the determination of the water level at the time of the data recording, which are both used to generate a DEM (Digital Elevation Model) of the intertidal area. The generation of the DEM is done in multiple steps, with the first one being the shoreline extraction. To find the shoreline, satellite imagery from the PROBA-V satellite is used. The image data consists of four channels (Red, Blue, NIR, SWIR), which are then combined to generate an artificial RGB image. This RGB image is then converted into the HSV colour space. To finally determine the threshold, the hue and value channel are selected, and a simple thresholding is applied to separate water masses from land masses. The final binary image is then cleaned from noise, and reduced to only a pixel-wide line representing the detected shoreline. This process is applied on several images taken at different water levels (i.e. different parts of the tidal cycle). To estimate the altitude level of the waterline, tidal data from tide gauges at Chittagong and Coxs Bazar are used. First, both tidal records are compared to determine the phase and amplitude scaling with respect to the distance of the two gauges. Afterwards, these values are used to inter- and extrapolate the water level along the shoreline. This allows to generate a synthetic tide measurement for every point at any time based on only the tidal records at Chittagong. The synthetic tide measurements are then combined with the shorelines to generate the final DEM. In the end, the generated DEM is compared with nautical charts of the area, as well as a different remotely-sensed DEM of Chittagong to estimate its accuracy. This whole process allows for a simple generation of inter tidal areas without having to make in-situ measurements of the area, and especially without repeating the measurements due to fast changes in the shoreline.

  • 284.
    Bergquist, Bjarne
    et al.
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle, Industriell Ekonomi.
    Vanhatalo, Erik
    Luleå tekniska universitet, Institutionen för ekonomi, teknik och samhälle.
    Nordenvaad, Magnus Lundberg
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    A Bayesian analysis of unreplicated two-level factorials using effects sparsity, hierarchy, and heredity2011Inngår i: Quality Engineering, ISSN 0898-2112, E-ISSN 1532-4222, Vol. 23, nr 2, s. 152-166Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article proposes a Bayesian procedure to calculate posterior probabilities of active effects for unreplicated two-level factorials. The results from a literature survey are used to specify individual prior probabilities for the activity of effects and the posterior probabilities are then calculated in a three-step procedure where the principles of effects sparsity, hierarchy, and heredity are successively considered. We illustrate our approach by reanalyzing experiments found in the literature.

  • 285.
    Bermúdez, Juan
    et al.
    Universidad Simón Bolívar.
    Alvarez, Manuel
    Universidad Simón Bolívar, Caracas.
    Inclusion of ancillary services in a cost-based centralized economic dispatch solution for hydrothermal systems2007Inngår i: LESCOPE'07: 2007 Large Engineering Systems Conference on Power Engineering : conference proceedings : the Delta Centre-Ville Hotel, Montreal, Quebec, Canada, October 10-12, 2007, Piscataway, NJ: IEEE Communications Society, 2007, s. 131-136, artikkel-id 4437366Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a centralized economic dispatch is developed, where some services are included, associated to frequency control and generation outages. The study can consider thermal machines but hydro turbines as well, both of the run-of-river or regulation type, in whose case the objective function is the present and future thermal cost in the context of the stochastic dual dynamic programming (SDDP), simplified for academic purposes [8][6]. In this study the immediate plus future thermal cost is minimized, taking into account the primary reserves requirement in each unit (speed governor primary action), plus the AGC reserve, besides the (tertiary) reserves, associated to the outage of any turbine (n-1 criterion). The problem proposed was resolved using a linear programming commercial package. For the sake of clarifying the results, some didactical cases are solved, where comparisons are discussed between the traditional energy-only dispatch and the model herein proposed. This paper extends in a very simple manner the results of a traditional cost-based centralized economic dispatch, of the hydrothermal case, to include the AGC restrictions and spinning reserves requirements. © 2007 IEEE.

  • 286.
    Bermúdez, Juan
    et al.
    Universidad Simón Bolívar.
    Alvarez, Manuel
    Universidad Simón Bolívar.
    Villasana, R.
    Universidad Simón Bolívar.
    Khodr, H. M.
    GECAD–Knowledge Engineering and Decision-Support Research Group of the Electrical Engineering Institute of Porto.
    Una metodologia para combinar los manteniminentos forzados y preventivos en etapas de panficacion2009Konferansepaper (Fagfellevurdert)
    Abstract [en]

    El Mantenimiento Correctivo (MC) o forzado es clásicamente un evento de naturaleza aleatoria,pero el Mantenimiento Preventivo (MP) o programado puede ser considerado un eventodeterminístico. Ahora bien, estrictamente hablando es imposible predecir cuándo exactamente unequipo será parado por efectos de MP, ni cuánto tiempo durará en ese estado. Por ende, a pesar decualquier programación que pueda realizarse, el MP es en realidad un evento aleatorio, cuyostiempos de permanencia en cada uno de sus vertientes (equipo operativo / equipo no operativo),pueden considerarse exponencialmente distribuidos, si el equipo está dentro de su periodo de deVida Útil. De ser así, la teoría de Markov puede ser utilizada para definir una forma de combinarlos dos procesos aleatorios, a nivel de la tasa de fallas y la duración de las paradas para cadaequipo, para posteriormente extender la aplicación a sistemas complejos, con generación ytransmisión considerados simultáneamente.En este trabajo se desarrolla tal esquema, el cual una vez formulado es aplicado a cálculostradicionales de confiabilidad en sistemas de potencia, tales como LOLE, ELOL, Elementos enSerie/Paralelo y Conjuntos de Corte. Se hacen comparaciones con las consideracionesdeterminísticas tradicionales, que sirvan para ilustrar las bondades de la metodología propuesta.Obviamente esta metodología se adapta perfectamente a las modernas simulaciones de MonteCarlo.

  • 287.
    Bermúdez, Juan
    et al.
    Universidad Simón Bolívar.
    Leanez, F.
    Pontificia Universidad Católica de Chile.
    Alvarez, Manuel
    Universidad Simón Bolívar, Caracas.
    Khodr, H. M.
    GECAD - Knowledge Engineering and Decision-Support Research Center.
    A generalized methodology based on symmetrical components for multiple-fault calculation in power systems2009Inngår i: Electric power components and systems, ISSN 1532-5008, E-ISSN 1532-5016, Vol. 37, nr 10, s. 1081-1101Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents an efficient computational method to solve the problem of simultaneous multiple faults in power systems, using a conventional symmetrical component formulation. The methodology made possible the development of a programming routine, which takes into account a generic set of boundary conditions for almost any type of fault or combination of faults that can occur simultaneously, involving any number of phases. The program was tested with IEEE 14-, 57-, 118-, and 300-busbar benchmark systems facing up to ten simultaneous series and shunt faults. The results were satisfactorily tested against classical three-phase formulation solutions.

  • 288.
    Berndtsson, Magnus
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fault detection in lambda-tuned control loops2006Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Poorly operating control loops cause loss in productivity in almost every industry worldwide. Therefore performance monitoring has been an active area of research for the past decades. In this work, a newly developed fault detection method is applied to the monitoring of lambda-tuned control loops. The lambda-tuning method has, due to its simple use, become very popular in the pulp and paper industry and is now spreading to other industries. A model-based fault detection algorithm assuming uncertain process parameters is used for detecting changes in the process. The algorithm consists of two parts, a residual and a time-varying threshold. The a priori information obtained from lambda-tuning is used to create an observer, which is used as residual generator. Known process inputs are used together with upper bounds for the uncertainties and upper bounds for disturbances when calculating the detection threshold. The observer may have integral action in order to make the threshold tight to the residual. Upper bounds for the uncertainties in the process parameters and upper bounds for disturbances are tuning parameters in the algorithm. Two different methods for finding those parameter values are proposed. The first is an approach based on allowed loss in phase margin and the second consists of solving a nonlinear optimization problem to minimize the difference between the residual and the threshold. The algorithm is tested in a simple water tank system. The threshold handles step changes in reference value without giving any false alarms. A fault is introduced by widening of the output in the water tank which simulates a change in the process parameters. The residual then gets larger than the threshold and the fault is detected.

  • 289. Berndtsson, Magnus
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Design of a dynamic threshold generator for λ-tuned control loops2008Inngår i: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 16, nr 5, s. 623-631Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dynamic threshold generator is employed for detecting faults in λ-tuned control loops. To this end, an optimizationalgorithm for dynamic threshold generators is proposed. The a priori-information from λ-tuning is used in designing astate estimator with integral action. A dynamic threshold generator for the residual of this state estimator is derived and the optimization algorithm is applied. Simulations with measurement data from an experimental water tank setup show that the method is capable of detecting a small fault without generating false alarms.

  • 290. Berndtsson, Magnus
    et al.
    Johansson, Andreas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Fault detection in lambda-tuned control loops using an observer with integral action2006Inngår i: 45th IEEE Conference on Decision and Control, 2006 : 13 - 15 Dec. 2006, [San Diego, CA, USA] / [ed] Pradeep Misra, Piscataway, NJ: IEEE Communications Society, 2006, s. 538-543Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A model-based fault detection algorithm assuming uncertain process parameters is used for detecting poorly operating lambda-tuned control loops. The a priori information obtained from lambda-tuning is used to create an observer as residual generator. The observer has integral action which makes it possible to obtain a tight fault detection threshold. A linear optimization approach is used for finding the parameters in the threshold.

  • 291. Bernhart, Martin
    et al.
    Bonvicino, Valentino
    Boschan, Eva
    Brotzenberger, Heinz
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Dewert, Francis
    Futukawa, Michio
    Rosmalen, Renée Janssen van
    Kapor, Slobodan
    Mounce, Richard
    Serracanta, Francisco
    Vercamer, Pascal
    Approach to the management of contaminated gas sites1997Inngår i: Proceedings World Gas Conference 1997, World Gas Union , 1997Konferansepaper (Fagfellevurdert)
  • 292.
    Berrebi, Jonathan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Improved techniques for self-diagnosis of an ultrasonic flow meter2002Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    For both economical and environmental raisons, accurate measurements of energy consumptions are important. The District Heating Industry supplies buildings and private houses of a whole city in hot water through a network. The energy supplied to a customer is measured by thermometers and by a flow meter inside the district-heating substation present at the customer’s place. The annual cost of the total metering error is approximately estimated at 170 Millions of Swedish Crowns for the Swedish District Industry. Accurate measurements of the flow rate turn out to be essential to a correct estimation of the energy consumption. Ultrasonic flow meters are of particular interest because of their good accuracy for a low cost. The main features of ultrasonic flow meters are studied. The estimation of the mean flow velocity and the calibration of the meter are described. Once installed, any kind of meter provides larger errors than in the facility where it has been calibrated. It is particularly true for ultrasonic flow meters that are very sensitive to installations effects. Installations effects can either be static or dynamic. Special attention is paid to errors generated by velocity profile variations. A diagnosis of the sensitivity of the meter to installations effects would allow for compensations for the errors. It is outlined that the notion of diagnosis comes within the theory of detection. A self-diagnosis is performed by the meter itself. The decision rule has to be modelled and inserted into the meter. Signal analysis allows detection of specific noise characteristic of a particular type of installation effect. An example of self-diagnosis showing the detection of pulsations in a flow is described in details.

  • 293.
    Berrebi, Jonathan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Self-diagnosis techniques and their applications to error reduction for ultrasonic flow measurement2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Flow metering plays a major role in modern life. In the process industry, flow metering is critical in industries ranging from food processing to cosmetics. It is also essential in custody transfer or billing, as flow meters are present in gas pumps and district heating substations. In the district heating industry, the ultrasonic flow meter has become the desired meter in many of its applications because it has a low cost while being accurate. This accuracy is however sensitive to installation effects and other sources of errors. This thesis stems from research that addresses the recognition of these installation effects, informs when they are unacceptable and considers reducing the measurement errors. To present these concepts, the thesis details the estimation of the mean flow velocity, the calibration of the meter and the measurement noise properties. Once installed, any kind of meter provides larger errors than in the facility where it has been calibrated and compensated. It is particularly true for ultrasonic flow meters as they are very sensitive to installation effects. Installation effects can either be static or dynamic. Special attention is paid to errors generated by temperature and velocity profile variations. Velocity profile variations can be due to pipe bends or flow pulsations. Such disturbances often induce a bias error and change the properties of the measurement noise. It is therefore with help of the change in noise that velocity profile disturbances can be detected. The detection of such abnormal behaviour of the measurement process constitutes a diagnosis. A diagnosis of the sensitivity of the meter to installations effects would allow for compensations for the errors. Signal analysis allows detection of specific noise properties, characteristic of installation effects. An example of self-diagnosis showing the detection of real pulsations in a flow is described in details. The detection of the flow pulsations and the estimation of their frequency allow to reduce the error of estimation on the flow rate. This technique is confirmed by the simulations of a pulsating flow. To empower one with the decision whether a flowmeter performance is normal or abnormal, a study of the relative error as a function of flow rate and temperature has been conducted.

  • 294.
    Berrebi, Jonathan
    et al.
    Luleå tekniska universitet.
    Martinsson, Pär-Erik
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Signaler och system.
    Willatzen, M.
    University of Southern Denmark.
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Ultrasonic flow metering errors due to pulsating flow2004Inngår i: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 15, nr 3, s. 179-185Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Transit-time ultrasonic flow meters present some advantages over other flow meters for district heating industries. They are both accurate and non-intrusive. It is well-known that ultrasonic flow meters are sensitive to installation effects. Installation effects could be static or dynamic. Among the possible dynamic installation effects is pulsating flow. The influence of pulsating flow on the prediction and the zero-crossing operations is investigated. Expressions are found for the prediction error and the zero-crossing error. The relative errors due to the prediction and the zero-crossing are plotted. The prediction error can reach dramatic values while the zero-crossing operation is hardly influenced by flow pulsations.

  • 295.
    Berrebi, Jonathan
    et al.
    Luleå tekniska universitet.
    van Deventer, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Detection of dynamic installation effects by an ultrasound flow meter in non-stationary flow2004Inngår i: Proceedings of the 12th International Conference on Flow Measurement: FLOMEKO, 2004, s. 277-279Konferansepaper (Fagfellevurdert)
  • 296. Berrebi, Jonathan
    et al.
    van Deventer, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Delsing, Jerker
    Detection of pulsating flows in an ultrasonic flow meter2002Inngår i: Proceedings of ISA Emerging Technologies Conference, 2002Konferansepaper (Fagfellevurdert)
  • 297. Berrebi, Jonathan
    et al.
    van Deventer, Jan
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Detection of pulsating flows in an ultrasonic flow meter2002Inngår i: Proceedings of the 8th International Symposium on District Heating and Cooling, 2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Transit-time ultrasonic flowmeters present advantages for district heating applications, since they are accurate, non-intrusive, and cheap. However, such flowmeters are sensitive to velocity profile variations since the flow rate is measured in the volume area between two ultrasonic transducers. Ultrasonic flowmeters are therefore sensitive to installation effects. Installation effects could be either static or dynamic. A pulsating flow is a dynamic installation effect. In the field, the diagnostic can only be performed with the measured flow rate. Flow measurements with and without pulsating flow have been recorded in a flow meter calibration facility. The detection of a pulsating flow can be made by using Hinich's harmogram. It is possible to detect harmonics that emerge from the noise by using the harmogram.

  • 298.
    Berrebi, Jonathan
    et al.
    Luleå tekniska universitet.
    van Deventer, Jan
    Delsing, Jerker
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Detection of the error generated by a single elbow on an ultrasonic flow meter2002Inngår i: ISA TECH/EXPO Technology Update Conference Proceedings: ETCON 2002, ISA - Instrumentation, Systems, and Automation Society , 2002, Vol. v 426 II, s. 1268-1279Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Ultrasonic flow meters are accurate and non-intrusive. However, one of their drawbacks is their sensitivity to installation effects especially when elbows or pulsating flows are found in front of the meter's inlet. Depending on the flow rate, such installations can create perturbations on the flow measurement. These perturbations cause an increase of the noise level as well as a possible error on the flow estimation. A technique using the noise level as a criterion for making a diagnostic of the error is presented. The perturbations are examined and compared to gaussian distributed signals. A basic method for detecting gaussian perturbations with equal means is described. The likelihood ratio is first computed in the general case. It is also computed making the assumption of uncorrelated signals. Receiver Operating Characteristics (R.O.C.) are plotted. The assumption of gaussian perturbations is then investigated. Optimal thresholds are proposed for both methods and for a large interval of flow rates (from 0.4 ml/s to 0,75 1/s). Probabilities of detection and of false alarm are evaluated for both methods. It is concluded that correct detection can be performed. The optimal threshold is to be chosen by the operator.

  • 299.
    Berrebi, Jonathan
    et al.
    Luleå tekniska universitet.
    van Deventer, Jan
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Delsing, Jerker
    Reducing the flow measurement error caused by pulsations in flows2004Inngår i: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, nr 5-6, s. 311-315Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Different types of errors are generated by pulsations in flows. Among these errors is the sampling error due to a unadapted time-averaging of the flow rate. An improved model for pulsations in flows including harmonics is derived. The localization of the harmonics is performed by a detector. The period of the pulsations is estimated. It is then possible to reduce the sampling error by performing a correct averaging. The reduction of the sampling error is confirmed by simulations.

  • 300.
    Berrios Moron, Jonathan Glenn
    Luleå tekniska universitet.
    Quality of Experience Provisioning in Mobile Cloud Computing2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
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