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  • 1.
    Adolfsson, Stefan
    et al.
    Luleå tekniska universitet.
    Ericsson, Klas
    Luleå tekniska universitet.
    Grennberg, Anders
    Automatic detection of burn-through in GMA welding using a parametric model1996In: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 10, no 5, 633-651 p.Article in journal (Refereed)
    Abstract [en]

    This paper addresses the problem of automatic detection of burn-through in weld joints. Gas metal arc (GMA) welding with pulsed current is used, and welding voltage and current are recorded. As short-circuitings are common between the welding electrode and the work piece during burn-through, a short-circuit detector is developed to detect these events. To detect another specific characteristic of burn-through - this detector is combined with a square-law detector. This second detector is based on a non-linear modification of an autoregressive model with extra input (ARX-model) of the welding process. The results obtained from this compound detector indicate that it is possible to detect burn-through in the welds automatically. The work also indicates that it is possible to design an on-line monitoring system for robotic GMA welding.

  • 2.
    Almquist, Lars-Olov
    et al.
    Lunds universitet.
    Olsson, Lennart
    Luleå tekniska universitet.
    Grennberg, Anders
    Holmner, Nils-Gunnar
    Lunds universitet.
    Registration and analysis of sound from the disintegration of kidney stones with acoustic shock waves1991In: WFUMB Symposium on Safety and Standardisation in Medical Ultrasound: issues and recommendations regarding thermal mechanisms for biological effects of ultrasound ; Hornbaek, Denmark, 30 August-1 September 1991 / [ed] Stan B. Barnett, New York: Pergamon Press, 1991Conference paper (Refereed)
  • 3. Andersson, Tobias
    et al.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Minimizing profile error when estimating the sieve-size distribution of iron ore pellets using ordinal logistic regression2011In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 206, no 3, 218-226 p.Article in journal (Refereed)
    Abstract [en]

    Size measurement of pellets in industry is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of pellet size based on image analysis techniques would allow non-invasive, frequent and consistent measurement. We evaluate the statistical significance of the ability of commonly used size and shape measurement methods to discriminate among different sieve-size classes using multivariate techniques. Literature review indicates that earlier works did not perform this analysis and selected a sizing method without evaluating its statistical significance. Backward elimination and forward selection of features are used to select two feature sets that are statistically significant for discriminating among different sieve-size classes of pellets. The diameter of a circle of equivalent area is shown to be the most effective feature based on the forward selection strategy, but an unexpected five-feature classifier is the result using the backward elimination strategy. The discrepancy between the two selected feature sets can be explained by how the selection procedures calculate a feature's significance and that the property of the 3D data provides an orientational bias that favours combination of Feret-box measurements. Size estimates of the surface of a pellet pile using the two feature sets show that the estimated sieve-size distribution follows the known sieve-size distribution.

  • 4.
    Andersson, Tobias
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Visibility classification of rocks in piles2008In: Digital Image Computing: Techniques and Applications: DICTA 2008 ; [Conference on Digital Image Computing: Techniques and Applications] ; 1 - 3 December 2008, Canberra, Australia ; proceedings, IEEE Communications Society, 2008, 207-213 p.Conference paper (Refereed)
    Abstract [en]

    Size measurement of rocks is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of rock size based on image analysis techniques would allow non-invasive, frequent and consistent measurement. In practical measurement systems based on image analysis techniques, the surface of rock piles will be sampled and therefore contain overlapping rock fragments. It is critical to identify partially visible rock fragments for accurate size measurements. In this research, statistical classification methods are used to discriminate rocks on the surface of a pile between entirely visible and partially visible rocks. The feature visibility ratio is combined with commonly used 2D shape features to evaluate whether 2D shape features can improve classification accuracies to minimize overlapped particle error.

  • 5. Andersson, Tobias
    et al.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Carlson, Johan E.
    A machine vision system for estimation of size distributions by weight of limestone particles during ship loading2012In: Minerals Engineering, ISSN 0892-6875, E-ISSN 1872-9444, Vol. 25, no 1, 38-46 p.Article in journal (Refereed)
    Abstract [en]

    The size distribution as a function of weight of particles is an important measure of product quality in the mining and aggregates industries. When using manual sampling and sieving, the weight of particles is readily available. However, when using a machine vision system, the particle size distributions are determined as a function of the number of particles. In this paper we first show that there can be a significant weight-transformation error when transforming from one type of size distribution to another. We also show how the problem can be overcome by training a classifier and scaling the results according to calibrated average weights of rocks. The performance of the algorithm is demonstrated with results of measurements of limestone particles on conveyor belts.

  • 6. Andersson, Tobias
    et al.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Marklund, Olov
    Pellet size estimation using spherical fitting2007In: 2007 IEEE Instrumentation and Measurement Technology Conference Proceedings: Warsaw, Poland, 1 - 3 May 2007, Piscataway, NJ: IEEE Communications Society, 2007, 1-5 p.Conference paper (Refereed)
    Abstract [en]

    Evaluation of Spherical Fitting as a technique for sizing iron ore pellets is performed. Size measurement of pellet in industry is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of pellet size would allow non-invasive, frequent and consistent measurement. Previous work has used an assumption that pellets are spherical to estimate pellet sizes. In this research we use a 3D laser camera system in a laboratory environment to capture 3D surface data of pellets and steel balls. Validation of the 3D data against a spherical model has been performed and demonstrates that pellets are not spherical and have physical structures that a spherical model cannot capture.

  • 7. Andersson, Tobias
    et al.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Marklund, Olov
    Visibility classification of pellets in piles for sizing without overlapped particle error2008In: 9th Biennial Conference of the Australian Pattern Recognition Society on Digital Image Computing Techniques and Applications: DICTA 2007 ; 3 - 5 Dec. 2007, Glenelg, [Adelaide], South Australia ; pPiscataway, NJ oceedings / [ed] Murk J. Bottema, IEEE Communications Society, 2008, 508-514 p.Conference paper (Refereed)
    Abstract [en]

    Size measurement of pellets in industry is usually performed by manual sampling and sieving techniques. Automatic on-line analysis of pellet size based on image analysis techniques would allow non-invasive, frequent and consistent measurement. We make a distinction between entirely visible and partially visible pellets. This is a significant distinction as the size of partially visible pellets cannot be correctly estimated with existing size measures and would bias any size estimate. Literature review indicates that other image analysis techniques fail to make this distinction. Statistical classification methods are used to discriminate pellets on the surface of a pile between entirely visible and partially visible pellets. Size estimates of the surface of a pellet pile show that the overlapped particle error is overcome by only estimating the surface size distribution with entirely visible pellets.

  • 8.
    Arenas, Julia Martinez
    et al.
    Ecole National Superieure de Telecommunications, Site de Toulouse.
    Landström, Daniel
    Department of Electrosciences, Lund Institute of Technology, Luleå tekniska universitet, Department of Applied Electronics, Lund University.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Börjesson, Per Ola
    Lund Institute of Technology, Department of Applied Electronics.
    Boucheret, Marie-Laure
    Ecole Nationale Supérieure des Télécommunications.
    Ödling, Per
    Department of Electrosciences, Lund Institute of Technology.
    Synchronization in OFDM systems: Sensitivity to the choice of pulse shape1997Conference paper (Refereed)
  • 9.
    Asplund, Teo
    et al.
    Uppsala University.
    Hendriks, Cris Luengo
    Centre for Image Analysis, Uppsala University and Swedish University of Agricultural Sciences.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Strand, Robin
    Uppsala University.
    A new approach to mathematical morphology on one dimensional sampled signals2016In: Proceedings of the 23rd International Conference on Pattern Recognition ICPR 2016, Piscataway, NJ: IEEE Communications Society, 2016, 3904-3909 p.Conference paper (Refereed)
    Abstract [en]

    We present a new approach to approximate continuous-domain mathematical morphology operators. The approach is applicable to irregularly sampled signals. We define a dilation under this new approach, where samples are duplicated and shifted according to the flat, continuous structuring element. We define the erosion by adjunction, and the opening and closing by composition. These new operators will significantly increase precision in image measurements. Experiments show that these operators indeed approximate continuous-domain operators better than the standard operators on sampled one-dimensional signals, and that they may be applied to signals using structuring elements smaller than the distance between samples. We also show that we can apply the operators to scan lines of a two-dimensional image to filter horizontal and vertical linear structures.

  • 10.
    Asplund, Teo
    et al.
    Uppsala University.
    Luengo Hendriks, Cris
    Flagship Biosciences Inc, Colorado, USA.
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems. Innovative Machine Vision Pty Ltd.
    Strand, Robin
    Uppsala University.
    Mathematical Morphology on Irregularly Sampled Data in One Dimension2017In: Mathematical Morphology : Theory and Applications, ISSN 2353-3390Article in journal (Refereed)
    Abstract [en]

    Mathematical morphology (MM) on grayscale images is commonly performed in the discretedomain on regularly sampled data. However, if the intention is to characterize or quantify continuousdomainobjects, then the discrete-domain morphology is affected by discretization errors that may bealleviated by considering the underlying continuous signal, given a correctly sampled bandlimited image.Additionally, there are a number of applications where MM would be useful and the data is irregularlysampled. A common way to deal with this is to resample the data onto a regular grid. Often this createsproblems where data is interpolated in areas with too few samples. In this paper, an alternative way ofthinking about the morphological operators is presented. This leads to a new type of discrete operatorsthat work on irregularly sampled data. These operators are shown to be morphological operators thatare consistent with the regular, morphological operators under the same conditions, and yield accurateresults under certain conditions where traditional morphology performs poorly

  • 11.
    Asplund, Teo
    et al.
    Centre for Image Analysis, Uppsala University.
    Luengo Hendriks, Cris
    Flagship Biosciences Inc..
    Thurley, Matthew
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Strand, Robin
    Centre for Image Analysis, Uppsala University.
    Mathematical Morphology on Irregularly Sampled Signals2017In: Computer Vision – ACCV 2016 Workshops: ACCV 2016 International Workshops, Taipei, Taiwan, November 20-24, 2016, Revised Selected Papers, Part II / [ed] Chu-Song Chen, Jiwen Lu, Kai-Kuang Ma, Cham: Springer, 2017, 506-520 p.Conference paper (Refereed)
    Abstract [en]

    This paper introduces a new operator that can be used to ap-proximate continuous-domain mathematical morphology on irregularly sampled surfaces. We define a new way of approximating the continuous domain dilation by duplicating and shifting samples according to a flat continuous structuring element. We show that the proposed algorithm can better approximate continuous dilation, and that dilations may be sampled irregularly to achieve a smaller sampling without greatly com-promising the accuracy of the result.

  • 12.
    Atta, Khalid
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Birk, Wolfgang
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hostettler, Roland
    Department of Electrical Engineering and Automation, Aalto University.
    Johansson, Andreas
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Phasor extremum seeking control with adaptive perturbation amplitude2016In: 2016 IEEE 55th Conference on Decision and Control, CDC 2016, Piscataway, NJ: Institute of Electrical and Electronics Engineers (IEEE), 2016, 7069-7074 p., 7799358Conference paper (Refereed)
    Abstract [en]

    In this paper, we propose a perturbation amplitude adaption scheme for phasor extremum seeking control based on the plant's estimated gradient. By using phasor extremum seeking instead of classical extremum seeking, the problem of algebraic loops in the controller formulation is avoided. Furthermore, a stability analysis for the proposed method is provided, which is the first stability analysis for extremum seeking controllers using adaptive amplitudes. The proposed method is illustrated using numerical examples and it is found that changes in optimum can be tracked accurately while the steady-state perturbations can be reduced significantly.

  • 13.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Akos, Dennis
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Nordenvaad, Magnus Lundberg
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Post-processing dynamic GNSS antenna array calibration and deterministic beamforming2008In: Proceedings of the 21th International Technical Meeting of the Satellite Division of the Institute of Navigation: ION GNSS 2008, 2008, Vol. 3, 1311-1319 p.Conference paper (Refereed)
    Abstract [en]

    An array processing GNSS (Global Navigation Satellite System) receiver may provide increased accuracy, reliability and integrity by forming beams towards satellites and nulls towards interference or reflective surfaces. Also, software defined receivers have proven themselves versatile and provide a convenient environment to implement novel algorithms.This paper first describes the gain/phase calibration of a seven element custom array antenna and proceeds to compare the single antenna performance to that of the performance attained by forming beams towards the satellites. IF (Intermediate Frequency) data, high rate samples representing the received signal in a narrow band around the GPS L1 frequency, from an array antenna have been recorded both in an environment with open sky conditions and also in more challenging areas (central Boulder, Colorado). Simultaneously, data from a high quality GPS based INS was recorded in order to obtain accurate estimates of position/ orientation. Calibration of the system (including antennas and front-ends) was performed using data from the benign environment, and based on this information, deterministic beams were formed towards the satellites using data from the semi-urban dataset. The single antenna accuracy was then compared to the position obtained by processing after forming beams.

  • 14.
    Backén, Staffan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Nordenvaad, Magnus Lundberg
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Akos, Dennis
    A novel software defined research receiver architecture2009In: Proceedings of the 13th IAIN World Congress: Stockholm, 27-30 October 2009, Nordic Institute of Navigation , 2009Conference paper (Refereed)
    Abstract [en]

    Software defined receivers (SDR) are an increasingly important tool within the GNSS research community as the high level of flexibility offer a significant advantage over traditional hardware implementations. Over the last decade, software receivers have been used to investigate techniques as diverse as bi-static radar (additional correlators), multipath mitigation techniques, GPS/INS integration and array processing.Mentioned above are only a few examples of features that could be required of an SDR, other include support for new signals (Galileo, GPS L5), multiple data file formats, high sensitivity and support for very long data sets. The large number of available features should ideally be coupled with program simplicity (such that other people can understand the program) and efficiency. This paper discusses these issues and proposes several solutions such asgeneralized data buffers (that is trivial to extend for new data formats) and a unified tracking structure (regardless of signal modulation). Examples are given using a Matlab implementation based on the Borre/Akos book Ä Software-Defined GPS and Galileo Receiver", however with significant modifications. Where critical, Java is used to increase performance while maintaining cross platform compatibility. Near real-time operation is available under optimal circumstances and the receiver currently supports GPS C/A- and GPS P-code signals.

  • 15. Barracó, Marc
    et al.
    Fernández, Enrique
    Torres, Ricardo
    López, José
    Bosch, Ricard
    Carlson, Johan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ultrasound monitoring of the setting of injectable bone cement biomaterials for spinal surgery applications2005In: Proceedings 2nd Annual European Rheology Conference, 2005, 133-133 p.Conference paper (Refereed)
  • 16.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Channel quality feedback schemes for 3GPP's Evolved-UTRA downlink2006In: IEEE GLOBECOM 2006: 2006 Global Telecommunications Conference; San Francisco, CA, USA, 27 November - 1 December 2006, Piscataway, NJ: IEEE Communications Society, 2006, 4151293Conference paper (Refereed)
    Abstract [en]

    Today's packet-based cellular systems typically are equipped with a channel quality reporting mechanism that supports scheduling and adaptive modulation/coding. When resources are scheduled not only In time but also In frequency the design of the return channel becomes intricate. The feedback signalling must balance improved cell-throughput with deteriorated spectral efficiency In the return link due to excessive signalling. In this contribution we examine system simulation results for the downlink of 3GPP's long-term evolution system equipped with various signalling schemes. The simulations results show that for a certain uplink load In bits/s/Hz, emphasizing the quality of the mobile's best channel instants (assigning these with more signalling bits) provides about 12% higher downlink throughput than capturing the quality of all channel Instants equally well. Moreover, about 95% of the throughput provided by an ideal reference feedback scheme Is obtained.

  • 17.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Estimation of synchronization parameters1996Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with the estimation of synchronization parameters in {Orthogonal Frequency Division Multiplexing} (OFDM) communication systems and in active ultrasonic measuring systems. Estimation methods for the timing and frequency offset and for the attenuation taps of the frequency selective channel are presented and investigated.In OFDM communication systems the estimation of the timing offset of the transmitted data frame is one important parameter. This offset provides the receiver with a means of synchronizing its sampling clock to that of the transmitter. A second important parameter is the offset in the carrier frequency used by the receiver to demodulate the received signal.For OFDM systems using a cyclic prefix, the joint {Maximum Likelihood} (ML) estimation of the timing and carrier frequency offset is introduced. The redundancy introduced by the prefix is exploited optimally. This novel method is derived for a non-dispersive channel. Its performance, however, is also evaluated for a frequency-selective Rayleigh-fading radio channel. Time dispersion causes an irreducible error floor in this estimator's performance. This error floor is the limiting factor for the applicability of the timing estimator. Depending on the requirements, it may be used in either an acquisition or a tracking mode. For the frequency estimator the error floor is low enough to allow for stable frequency tracking.A low-complex variant of the timing offset estimator is presented allowing a simple implementation. This is the ML estimator, given a 2-bit representation of the received signal as the sufficient statistics. Its performance is evaluated for a frequency-selective Rayleigh-fading radio channel and for a twisted-pair copper channel. Simulations show this estimator to have a similar error floor as the full resolution ML estimator.The problem of estimating the propagation time of a signal is also of interest in active pulse echo systems, such as are used in, {\it e.g.}, radar, medical imaging, and geophysics. The {Minimum Mean Squared Error} (MMSE) estimator of arrival time is derived and investigated for an active airborne ultrasound measurement system. Besides performing better than the conventional {\it Maximum a Posteriori} (MAP) estimator, this method can be used to develop different estimators in situations where the system Signal to Noise Ratio (SNR) is unknown.Coherent multi-amplitude OFDM receivers generally need to compensate for a frequency selective channel in order to detect transmitted data symbols reliably. For this purpose, a channel equalizer needs to be fed estimates of the subchannel attenuations.The linear MMSE estimator of these attenuations is presented. Of all linear estimators, this estimator optimally makes use of the frequency correlation between the subchannel attenuations. Low-complex modified estimators are proposed and investigated. The proposed modifications cause an irreducible error floor for this estimator's performance, but simulations show that for SNR values up to 20~dB, the improvement of a modified estimator compared to the Least Squares (LS) estimator is at least 3~dB.

  • 18.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    OFDM Spectral Precoding with Protected Subcarriers2013In: IEEE Communications Letters, ISSN 1089-7798, E-ISSN 1558-2558, Vol. 17, no 12, 2209-2212 p.Article in journal (Refereed)
    Abstract [en]

    A new precoder structure reduces an OFDM signal's out-of-band emission by tens of decibels while allowing a receiver to employ a classical OFDM channel estimator.

  • 19.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Synchronization and channel estimation in OFDM systems1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis addresses synchronization and channel estimation in OFDM communication systems. The joint maximum likliehood estimator of symbol time and carrier frequency offsets for OFDM systems using a cyclic prefix is presented. This estimator exploits the redundancy introduced by the prefix and does not require extra pilot information. Signal models, accounting for pulse shaping, channel dispersion, or slowly changing synchronization errors and the associated maximum likliehood estimators are presented. Tracking synchronization of a multiuser OFDM system, which often has been questioned, is feasible using a scheme incorporating the above estimator concept. Furthermore, this thesis analyzes channel estimators based on the discrete Fourier transform. The symbol error rate of systems employing these estimators may experience an irreducible error floor. A novel channel estimation concept using singular-value decomposition of the channel attenuations is presented. These channel estimators, designed with suitably chosen fixed design parameters, combine low-complexity and high performance.

  • 20.
    Beek, Jaap van de
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    White Paper for Research Beyond 5G2015Report (Other academic)
  • 21.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Berggren, Fredrik
    Huawei Technologies Sweden.
    EVM-constrained OFDM precoding for reduction of out-of-band emission2009In: 2009 IEEE 70th Vehicular Technology Conference - Fall: VTC 2009-Fall; Anchorage, Alaska, USA, 20 - 23 September 2009, Piscataway, NJ: IEEE Communications Society, 2009, 5378740Conference paper (Refereed)
    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

  • 22.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Bollen, Math
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Larsson, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Energy Science.
    Eriksson, Mats
    Arctos Labs Scandinavia AB.
    Can Solar Power Help Providing Broadband Cellular Coverage in Extreme-Rural Sweden?2016Report (Other academic)
  • 23.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 OFDM1998Report (Refereed)
  • 24.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 OFDM1999In: IEEE Journal on Selected Areas in Communications, ISSN 0733-8716, E-ISSN 1558-0008, Vol. 17, no 11, 1900-1914 p.Article in journal (Refereed)
    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).

  • 25.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 proposal1997In: Emerging techniques for communication terminals: proceedings of COST 254 Workshop, Toulouse, France, 07-09 July 1997., Toulouse: INP-ENSEEIHT , 1997, 315-320 p.Conference paper (Other academic)
    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.

  • 26.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 OFDM1998Report (Other academic)
    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.

  • 27.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 system1998In: 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, 1290-1294 p.Conference paper (Refereed)
    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.

  • 28.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 signals1993Report (Other academic)
    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.

  • 29.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 offset1996Report (Other academic)
    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.

  • 30.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 uplink1996Report (Other academic)
    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.

  • 31.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 system1996Report (Other academic)
    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.

  • 32.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 system1996In: Proceedings of Nordic Radio Symposium: NRS '96, Lund, Sweden, August 1996, 1996, 32-35 p.Conference paper (Refereed)
    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.

  • 33.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 systems1995In: 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, 815-819 p.Conference paper (Refereed)
    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

  • 34. 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 band2012In: 2012 IEEE International Symposium on Dynamic Spectrum Access Networks (DYSPAN 2012): Bellevue, Washington, USA, 16 - 19 October 2012, Piscataway, NJ: IEEE Communications Society, 2012, 272-273 p.Conference paper (Refereed)
    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.

  • 35.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Popović, Branislav M.
    Huawei Technologies Sweden.
    Benefits of modulation diversity in turbo-coded OFDM systems2004In: IEEE Vehicular Technology Conference (VTC) Proceedings, ISSN 1550-2252, Vol. 59, no 2, 929-933 p.Article in journal (Refereed)
    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

  • 36.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Popović, Branislav M.
    Huawei Technologies Sweden.
    Multiple access with low-density signatures2009In: GLOBECOM 2009: 2009 IEEE Global Telecommunications Conference; Honolulu, Hawaii, USA, 30 November - 4 December 2009, Piscataway, NJ: IEEE Communications Society, 2009, 5425243Conference paper (Refereed)
    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.

  • 37. 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 Europe2012In: IEEE Transactions on Mobile Computing, ISSN 1536-1233, E-ISSN 1558-0660, Vol. 11, no 2, 178-188 p.Article in journal (Refereed)
    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.

  • 38.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    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 band2011In: 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, 1-9 p., 5936207Conference paper (Refereed)
    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

  • 39. 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 spaces2012In: 2012 Future Network & Mobile Summit (FutureNetw 2012): Berlin, Germany, 4 - 6 July 2012, Piscataway, NJ: IEEE Communications Society, 2012, 6294241Conference paper (Refereed)
    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

  • 40.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    ML estimation of time and frequency offset in OFDM systems1997In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 45, no 7, 1800-1805 p.Article in journal (Refereed)
    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.

  • 41.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    ML estimation of timing and frequency offset in multicarrier systems1996Report (Other academic)
    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.

  • 42.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    On synchronization in OFDM systems using the cyclic prefix1996In: 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, 663-667 p.Conference paper (Refereed)
    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.

  • 43.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sandell, Magnus
    Luleå tekniska universitet.
    Börjesson, Per-Ola
    Luleå tekniska universitet.
    ML estimation of time and frequecy offset in OFDM systems1998In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 45, no 7, 1800-1805 p.Article in journal (Refereed)
  • 44.
    Beek, Jaap van de
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Sandell, Magnus
    Luleå tekniska universitet.
    Isaksson, Mikael
    Telia Research AB.
    Börjesson, Per Ola
    Luleå tekniska universitet.
    Low-complex frame synchronization in OFDM systems1995In: 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, 982-986 p.Conference paper (Refereed)
    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

  • 45. 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 networks2012In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 19, no 4, 17-24 p.Article in journal (Refereed)
    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.

  • 46. Bengtsson, Daniel
    et al.
    Deutgren, Petra
    Grip, Niklas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    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 capacity1997Report (Other academic)
    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).

  • 47.
    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 system1996In: 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, 668-672 p.Conference paper (Refereed)
    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.

  • 48.
    Bergquist, Bjarne
    et al.
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Vanhatalo, Erik
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences.
    Nordenvaad, Magnus Lundberg
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A Bayesian analysis of unreplicated two-level factorials using effects sparsity, hierarchy, and heredity2011In: Quality Engineering, ISSN 0898-2112, E-ISSN 1532-4222, Vol. 23, no 2, 152-166 p.Article in journal (Refereed)
    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.

  • 49.
    Berrebi, Jonathan
    et al.
    Luleå tekniska universitet.
    Martinsson, Pär-Erik
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Willatzen, M.
    University of Southern Denmark.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Ultrasonic flow metering errors due to pulsating flow2004In: Flow Measurement and Instrumentation, ISSN 0955-5986, E-ISSN 1873-6998, Vol. 15, no 3, 179-185 p.Article in journal (Refereed)
    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.

  • 50.
    Birk, Wolfgang
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hostettler, Roland
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Distance- Spanning Technology.
    Lundberg Nordenvaad, Magnus
    Luleå University of Technology, Department of Business Administration, Technology and Social Sciences, Business Administration and Industrial Engineering.
    Eliasson, Jens
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Gylling, Arne
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Distance- Spanning Technology.
    Delsing, Jerker
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Osipov, Evgeny
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Embedded Internet Systems Lab.
    Mäkitaavola, Henrik
    Project: iRoad2011Other (Other (popular science, discussion, etc.))
1234567 1 - 50 of 486
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