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  • 201.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Landin, Per Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van Moer, Wendy
    Vrije Universiteit Brussel, ELEC department.
    Björsell, Niclas
    University of Gävle, Radio center for measurement technology.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Isaksson, Magnus
    University of Gävle, Department of Electronics, Mathematics and Natural Sciences.
    Peak-to-average power ratio reduction versus digital pre-distortion in OFDM based systems2011In: Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International, IEEE , 2011, p. 1-4Conference paper (Refereed)
    Abstract [en]

    In this paper we evaluate the effect of applying peak-to-average power ratio (PAPR) reduction and digital pre-distortion (DPD) on radio frequency power amplifiers when an orthogonal frequency division multiplexing (OFDM) signal is used. The PAPR reduction method, presented as a convex problem, is based on reshaping the time domain signal by redistributing its energy in the frequency domain, with respect to constraints on in-band and out-of-band errors. The DPD method consists of modeling the behavior of the power amplifier using a parallel Hammerstein model, and then extracting its inverse parameters based on the indirect learning approach. The cases where PAPR and DPD are applied separately and combined, are studied and investigated. Power amplifier figures of merit are evaluated. A good performance is shown when combining both pre-processing techniques up to a certain operating point where DPD performance deteriorates. Solutions to improve the DPD performance at strong compression are suggested.

  • 202.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Landin, Per Niklas
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van Moer, Wendy
    Vrije Universiteit Brussel, ELEC department.
    Björsell, Niclas
    University of Gävle, Radio center for measurement technology.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rönnow, Daniel
    University of Gävle, Radio center for measurement technology.
    Peak-power controlling technique for enhancing digital pre-distortion of RF power amplifiers2012In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 60, no 11, p. 3571-3581Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a method to limit the generation of signal peak power at the output of a digital pre-distorter that is applied to a RF power amplifier (PA) operating in strong compression. The method can be considered as a joint crest-factor reduction and digital pre-distortion (DPD). A challenging characteristic of DPD when applied to a PA in strong compression is the generation of relatively high peaks due to the DPD expansion behavior. Such high peaks generation, which may be physically unrealistic, can easily damage the amplification system. Such a phenomenon, referred in this study as DPD-avalanche, is more noticed when the signal exciting the PA is compressed due to crest-factor reduction. The suggested method for controlling such DPD-avalanche is based on shaping the input signal to the DPD in such a way to keep the pre-distorted signal peak power below or near the maximum allowed peak power of the PA. The suggested method is tested experimentally on a Class-AB and a Doherty PA when excited with a wideband orthogonal frequency-division multiplexing (OFDM) signal. Scenarios for an OFDM signal with and without crest-factor reduction are evaluated. Measurement results when using the proposed DPD-avalanche controller show smooth deterioration of the in-band and out-of-band linearity compared to steep deterioration when no controller is used. In addition, the suggested controller offers a higher operating power range of the DPD while fulfilling out-of-band distortion requirements and preserving low in-band error.

  • 203.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van Moer, Wendy
    Vrije Universiteit Brussel, ELEC department.
    Barbé, Kurt
    Vrije Universiteit Brussel, ELEC department.
    Björsell, Niclas
    University of Gävle, Radio center for measurement technology.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Characterizing the out-of-band Nonlinear Behavior of RF Devices: The Key to Success2011In: Conference Record - IEEE Instrumentation and Measurement Technology Conference, IEEE , 2011, p. 790-794Conference paper (Refereed)
    Abstract [en]

    This paper presents a measurement recipe to characterize the out-of-band nonlinear behavior of RF devices when harmonic sampling is used as a digitizing technique. A major challenge to consider when using harmonic sampling is the overlapping of the aliased spectral bins of the digitized waveform. This challenge is more pronounced when using modulated excitation signals. In addition, the excitation signal used should mimic the real behavior of signals used in today's wireless systems. Hence, this paper provides the reader with a tool to select the proper excitation signal, sampling frequency and record length in order to achieve an accurate characterization of the nonlinear behavior of RF devices.

  • 204.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Van Moer, Wendy
    Barbé, Kurt
    Björsell, Niclas
    Center for RF Measurement Technology, University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Evolved Harmonic Sampling: a Tool to Reduce the Digital Bandwidth Requirement of RF Receivers2011In: RFMTC11, 2011Conference paper (Other academic)
  • 205.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle, Sweden; Vrije Universiteit Brussel, Belgium.
    Van Moer, Wendy
    Vrije Universiteit Brussel, Belgium.
    Barbé, Kurt
    Vrije Universiteit Brussel, Belgium.
    Björsell, Niclas
    University of Gävle, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. University of Gävle, Sweden.
    Harmonic Sampling and Reconstruction of Wideband Undersampled Waveforms: Breaking the Code2011In: IEEE transactions on microwave theory and techniques, ISSN 0018-9480, E-ISSN 1557-9670, Vol. 59, no 11, p. 2961-2969Article in journal (Refereed)
    Abstract [en]

    In this paper, a method for measuring wideband waveforms correctly when undersampling is used as a digitizing technique is presented. Two major challenges arise when undersampling wideband waveforms: overlapping of aliased spectral bins of the digitized waveform and ambiguity in spectral bins standing on multiples of the Nyquist frequency. Those challenges are more pronounced when using wideband modulated signals to excite nonlinear devices. The theory behind a correct undersampled measurement is based on the use of an irrational relation between the undersampling frequency and the spectral resolution of the waveform to measure. This is the key to a successful harmonic sampling used today in large-signal network analyzers when wideband modulated waveforms are to be measured. Inverting the problem, such theory is also the solution for reconstructing wideband undersampled waveforms based on a single measurement and with a relatively short record of measured data. It is a solution for RF sampling and cognative radios where the digital processing is moving toward the antenna of the receiver.

  • 206.
    Nader, Charles
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Van Moer, Wendy
    Vrije Universiteit Brussel, ELEC department.
    Björsell, Niclas
    University of Gävle, Radio center for measurement technology.
    Barbé, Kurt
    Vrije Universiteit Brussel, ELEC department.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Reducing the Analog and Digital Bandwidth Requirements of RF Receivers for Measuring Periodic Sparse Waveforms2012In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 61, no 11, p. 2960-2971Article in journal (Refereed)
    Abstract [en]

    In this paper, a prototype setup for measuring wideband periodic waveforms whose bandwidth surpasses the analog bandwidth of a radio-frequency receiver is presented. Three major challenges arise in the analog-to-digital stage when measuring such wideband waveforms: the availability of a high sampling rate based on a good amplitude resolution; the availability of the required analog bandwidth to capture the full waveform; and achieving the previous requirements in a cheap way. Those challenges are more pronounced when using wideband modulated signals to test nonlinear devices and when measuring/sensing wideband spectra for cognitive radio applications. For periodic signals, undersampling techniques based on the evolved harmonic sampling can be used to reduce the sampling rate requirements while satisfying a good amplitude resolution. For sparse signals, a technique based on channelization and signal separation is proposed. This technique splits the spectrum of the waveform into parallel channels, downconverts them to the analog frequency band of the analog-to-digital converter (ADC), spreads the channel information, sums them, and then digitizes with a single ADC. Using reconstruction algorithms based on l(1)-norm minimization, the information of the parallel channels can be separated. The original wideband spectrum can be then reconstructed after de-embedding of the channelization process.

  • 207. Nader, Charles
    et al.
    Van Moer, Wendy
    Björsell, Niclas
    Department of Electronics, Mathematics and Natural Sciences, University of Gävle.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Wideband Radio Frequency Measurements: From instrumentation to sampling theory2013In: IEEE Microwave Magazine, ISSN 1527-3342, E-ISSN 1557-9581, Vol. 14, no 2, p. 85-98Article in journal (Refereed)
    Abstract [en]

    Whether listening to broadcast radio or testing developed wireless devices, for civilian or military applications, based on terrestrial or spatial links, a radio frequency (RF) receiver with good measurement capabilities that preserves the received signal information is required. Todays RF measurement receivers with wideband capabilities are split into two groups based on the measurement strategy they adopt. Both groups produce a time domain waveform with both amplitude and phase information that is constructed either from a transformation of its frequency contents or directly from its time-domain samples.

  • 208.
    Negusse, Senay
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Parameter estimation employing a dual channel sine-wave model under sparse coprime sampling2011In: 18th IMEKO TC4 Symposium on Measurement of Electrical Quantities 2011, Part of Metrologia 2011, IMEKO-International Measurement Federation Secretariat , 2011, p. 290-295Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider a dual channel signal model with common frequency that is appropriate in a plurality of measurement setups, including impedance measurements and imbalance measurement in direct conversion RF receivers. We investigate on new approach and present analysis of parameter estimation, specifically the seven parameter dual channel sine fit in which the signals from both channels are uniformly subsampled with coprime pair of sparse samplers and combined in a signal array. Simulation results shall show acquired improvement in complexity as well as loss in estimation performance compared to that of an estimation from Nyquist sampled signal. 

  • 209.
    Negusse, Senay
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    The Dual Channel Sinewave Model: Co-Prime Sparse Sampling, Parameter Estimation, and the Cramer-Rao Bound2012In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 45, no 9, p. 2254-2263Article in journal (Refereed)
    Abstract [en]

    The seven-parameter sine fit algorithm for a dual channel signal model with common frequency has been considered in a prior work as an accurate procedure for parameter estimation. In this paper, we investigate an approach in the dual channel sine fit where the signals from both channels are uniformly subsampled with coprime pair of sparse samplers and present analysis of the frequency estimation problem from undersampled measurements thereby relaxing the demand on devices and instruments by lowering the required sampling frequency as well as bandwidth. The Cramér–Rao Bound based on the coprime subsampled data set is derived and numerical illustrations are given showing the relation between the cost in performance based on the mean squared error and the employed coprime factors for a given measurement time.

  • 210.
    Negusse, Senay
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    IEEE-STD-1057 Three Parameter Sine Wave Fit for SNR Estimation: Performance Analysis and Alternative Estimators2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, no 6, p. 1514-1523Article in journal (Refereed)
    Abstract [en]

    This paper considers the three-parameter-fit sine wave model. Under a Gaussian noise assumption, it is known that the three-parameter fit given in IEEE Standards 1057 and 1241 coincides with the method of maximum likelihood (ML), which is known for its favorable properties in large samples. Under coherent sampling assumption, the Cramér--Rao Bound of an unbiased estimator (UE) of the signal-to-noise ratio (SNR) is derived followed by an exact finite-sample analysis of the ML estimator of SNR derived from the three-parameter fit, revealing its nonsymmetric F-distribution. Exact expressions for the bias, variance, and the mean squared error (MSE) of the ML estimator are then derived, revealing that the ML estimator in finite samples is far from optimal in terms of precision and accuracy. With the ML estimator as a starting point, several alternative estimators are derived, which outperform the method of ML. In particular, a UE is derived, with lower variance compared with the ML for small sample size. In addition, estimators are derived based on constrained minimization of the MSE. The theoretical findings are illustrated by simulations, showing an excellent agreement between theory and practice. Simulations using quantized data are also used to show the performance of the derived estimators mimicking an analog-to-digital converter (ADC) testing scenario. Furthermore, the derived estimators are applied to coherently and noncoherently sampled measurement data from a 12-bit ADC and, for small number of samples, all are shown to outperform the original estimate, showing the practical relevance of the theoretical findings.

  • 211.
    Negusse, Senay
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing.
    On SNR estimation using IEEE-STD-1057 three-parameter sine wave fit2013In: IEEE International Instrumentation and Measurement Technology Conference (I2MTC), 2013, IEEE conference proceedings, 2013, p. 658-661Conference paper (Refereed)
    Abstract [en]

    In this paper, theoretical properties of a maximum-likelihood (ML) estimator of signal-to-noise ratio (SNR) is discussed. The three-parameter sine fit algorithm is employed on a finite and coherently sampled measurement set corrupted by additive white Gaussian noise. Under the Gaussian noise model, the least squares solution provided by the three-parameter sine fit is also ML estimator. Exact distribution and finite sample properties of the SNR estimate are derived. Moreover, an explicit expression for the mean squared error (MSE) of the estimator is given. Simulation results are shown to verify the underlying theoretical results.

  • 212.
    Negusse, Senay
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zetterberg, Per
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Phase-noise mitigation in OFDM by best match trajectories2015In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 63, no 5, p. 1712-1725Article in journal (Refereed)
    Abstract [en]

    This paper proposes a novel approach to phasenoise compensation. The basic idea is to approximate the phasenoise statistics by a finite number of realizations, i.e., a phasenoise codebook. The receiver then uses an augmented received signal model, where the codebook index is estimated along with other parameters. The realization of the basic idea depends on the details of the air interface, the phase-noise statistics, the propagation scenario and the computational constraints. In this paper, we will focus on a MQAM-OFDM system with pilot subcarriers within each OFDM symbol. The channel is frequency selective, fading and unknown. A decision-feedback method is employed to further enhance performance of the system. Simulation results are shown for uncoded and coded systems to illustrate the performance of the algorithm, which is als o compared with previously employed methods. Our simulation s show that for a 16-QAM coded OFDM system over a frequency selective Rayleigh fading channel affected by phase noise with root-mean-square (RMS) of 14.4 degrees per OFDM symbol, the proposed algorithm is 1.5dB from the ideal phase-noise free case at a BER of 10 − 4 . The performance of the best reference scheme is 2.5dB from the ideal case at BER of 10 − 4 . The proposed scheme is also computationally attractive.

  • 213.
    Nilsson, Jan-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Gupta, A. K.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Foot-mounted inertial navigation made easy2014In: IPIN 2014 - 2014 International Conference on Indoor Positioning and Indoor Navigation, IEEE conference proceedings, 2014, p. 24-29Conference paper (Refereed)
    Abstract [en]

    Despite being around for almost two decades, foot-mounted inertial navigation only has gotten a limited spread. Contributing factors to this are lack of suitable hardware platforms and difficult system integration. As a solution to this, we present an open-source wireless foot-mounted inertial navigation module with an intuitive and significantly simplified dead reckoning interface. The interface is motivated from statistical properties of the underlying aided inertial navigation and argued to give negligible information loss. The module consists of both a hardware platform and embedded software. Details of the platform and the software are described, and a summarizing description of how to reproduce the module are given. System integration of the module is outlined and finally, we provide a basic performance assessment of the module. In summary, the module provides a modularization of the foot-mounted inertial navigation and makes the technology significantly easier to use.

  • 214.
    Nilsson, John Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fast Argument Quantization2013In: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 30, no 6, p. 169-172Article in journal (Refereed)
    Abstract [en]

    Aquantized low-resolution argument of a complex number or two-dimensional vector is required in many digital signal processing algorithms. Examples include APSK code demodulation for which it may be used to evaluate the Voronoi diagram; low-level processing for many computer vision methods that exploit histograms of gradient sample arguments, e.g., SIFT and HOG; and phase tracking/frequency estimation for which it may be used as a low-cost phase approximation. Often, such quantized arguments will have to be computed many times and under real-time constraints. Therefore, efficient solutions to these calculations are of interest.

  • 215.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    De Angelis, Alessio
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Carbone, Paolo
    Department of Electronic and Information Engineering, University of Perugia.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    SIGNAL PROCESSING ISSUES IN INDOOR POSITIONING BY ULTRA WIDE BAND RADIO AIDED INERTIAL NAVIGATION2009In: Proc. EUSIPCO2009, EURASIP , 2009, p. 2161-2165Conference paper (Refereed)
    Abstract [en]

    The difficulties and possibilities connected to indoor positioning suggest using several sources of navigational information. Apart from the signal processing of the individual sources this gives rise to the need for information fusion. This article aims at presenting and describing the signal processing methods and issues faced when constructing a navigation system based on a local ultra wide band (UWB) ranging system and an inertial navigation system (INS). The signal processing methods within the individual systems are described together with techniques for fusing the information from them. Finally, filtering results of experimental data is presented with expected convergence properties and positioning accuracy of below ±4 cm.

  • 216.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Gradient sample argument weighting for robust image region description2013In: Proceedings of the 2013 IEEE International Conference on Electronics, Computing and Communication Technologies (IEEE CONECCT), IEEE conference proceedings, 2013, p. 1-4Conference paper (Refereed)
    Abstract [en]

    The weighting of gradient sample arguments for the creation of descriptors of image regions is studied. The descriptors are interpreted as binned and weighted argument kernel density estimates and thereby their defining attributes are identified as the binning rules and the weighting. The weighting is further studied and four different weighting strategies are analyzed. The naive constant weighting is argued to have a poor robustness to image perturbations. As an answer to this, the customary gradient magnitude weighting is motivated. However, the short-comings of this approach are pointed out and two novel weighting strategies are suggested. The first suggested weighting gives a system parameter determining a distinctiveness to robustness trade-off with the customary magnitude weighting being a special case of it. The second suggested weighting gives a similar robustness as the first one, but at a lower computational cost. Finally, the effects of the different weighting strategies are demonstrated with real imagery data and synthetic perturbations.

  • 217.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Recursive Bayesian Initialization of Localization Based on Ranging and Dead Reckoning2013In: Intelligent Robots and Systems (IROS), 2013 IEEE/RSJ International Conference on, IEEE conference proceedings, 2013, p. 1399-1404Conference paper (Refereed)
    Abstract [en]

    The initialization of the state estimation in a localization scenario based on ranging and dead reckoning is studied. Specifically, we treat a cooperative localization setup and consider the problem of recursively arriving at a unimodal state estimate with sufficiently low covariance such that covariance based filters can be used to estimate an agent's state subsequently. The initialization of the position of an anchor node will be a special case of this. A number of simplifications/assumptions are made such that the estimation problem can be seen as that of estimating the initial agent state given a deterministic surrounding and dead reckoning. This problem is solved by means of a particle filter and it is described how continual states and covariance estimates are derived from the solution. Finally, simulations are used to illustrate the characteristics of the method and experimental data are briefly presented.

  • 218.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Robust recursive network clock synchronization2014In: 2014 IEEE International Conference on Electronics, Computing and Communication Technologies (IEEE CONECCT), IEEE Computer Society, 2014, p. 6740335-Conference paper (Refereed)
    Abstract [en]

    A simple and statistically robust method for passive clock synchronization in sensor networks is presented. The method is not limited to passive (one-way communication) synchronization, but this scenario justifies the method. The recursive nature of the method and the targeted passive setup mean that it adds a minimum of requirements on the system in which it is used. Statistical characteristics of the method are quantified and real measurements are used to illustrate the robustness and performance gain relative to a naive Kalman filter based clock synchronization. Finally, C++ code that implements the suggested clock synchronization method, is provided in this article.

  • 219.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Standing still with inertial navigation2013Conference paper (Refereed)
    Abstract [en]

    The possibility to detect complete standstill sets footmounted inertial navigation aside from other heuristic pedestrian dead reckoning systems. However, traditional zero-velocityupdates (ZUPTs) does not ensure that the system is actually static but a drift will occur. To eliminate the drift we suggest using a modified mechanization which locks certain states under certain conditions. Experimental data is used to demonstrate the effectiveness of the approach.

  • 220.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Time Synchronization and Temporal Ordering of Asynchronous Sensor Measurements of a Multi-sensor Navigation System2010In: 2010 IEEE-ION POSITION LOCATION AND NAVIGATION SYMPOSIUM PLANS, New York: IEEE conference proceedings, 2010, p. 241-246Conference paper (Refereed)
    Abstract [en]

    In this article we propose a filter based method to solve the time synchronization and minimum delay temporal ordering problem of asynchronous sensor measurements. A problem which inevitably arise in the sensor fusion of a multi-sensor navigation system implemented in realtime on a general purpose operation system (OS) without using functionality dedicated to realtime applications. The time synchronization is done up to a constant error by linear filtering of time stamps given to each measurement. The filtered time stamps together with predicted future time stamps are then used in a measurement temporal ordering algorithm to achieve a minimal delay temporal ordering subject to a user specified jitter tolerance. Finally, experimental time synchronization and temporal ordering results from the system implemented with a typical set of navigation sensors are presented.

  • 221.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kristensen, Johan
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    A unifying approach to feature point orientation assignmentManuscript (preprint) (Other academic)
    Abstract [en]

    A general structure of an orientation measure for orientation assignment of 2D image feature points is heuristically motivated. The measure is discretized and general approximation methods are presented. Orientation assignment methods found in the literature are shown to exploit special cases of the general measure, which thereby provides a unifying framework for them. An analytical robustness analysis is conducted, giving a number of desirable robustness properties of the measure components. Following this, a detailed treatment of implementation issues such as gradient sampling and binning is given and based on the desirable properties and other implementation considerations, specific measure components with implementations are suggested. Together, this constitutes a novel feature point orientation assignment method, which we have called RAID. We argue that this method is considerably less expensive than comparable methods in the literature, and by means of a quantitative perturbation analysis, a significantly improved orientation assignment repeatability is demonstrated compared with the available methods found in the literature.

     

  • 222.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Kristensen, Johan
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fast scale-space approximation by cascaded box filters and integer signal representationManuscript (preprint) (Other academic)
    Abstract [en]

    A method for computationally inexpensive approximation of a set of scale levels in a Gaussian scale-space is presented. Box filters of different widths and orientations are cascaded to approximate the Gaussian kernels. The signal is downsampled at higher scales to reduce the number of samples and thereby the computational cost. Integer signal representation is used throughout the filtering, and the signal is downshifted as required to keep within the numerical range of the representation. The filtering require only add (and subtract) and shift operations to implement. An optimization problem is formulated for designing the filter cascade and a branch-and-bound technique is used to solve it. The level of approximation versus the computational cost is studied and based on a qualitative comparison with state-of-the-art approximation methods, it is concluded that the presented method shows unprecedented low computational cost and unique properties for low cost Gaussian scale-space approximation.

     

  • 223.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rantakokko, Jouni
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ohlsson, Martin
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Hari, K.V.S.
    Indian Institute of Science (IISc).
    Accurate Indoor Positioning of Firefighters using Dual Foot-mounted Inertial Sensors and Inter-agent Ranging2014In: Proceedings of the Position, Location and Navigation Symposium (PLANS), 2014 IEEE/ION, 2014Conference paper (Refereed)
    Abstract [en]

    A real-time cooperative localization system,utilizing dual foot-mounted low-cost inertial sensors and RFbasedinter-agent ranging, has been developed. Scenario-basedtests have been performed, using fully-equipped firefightersmimicking a search operation in a partly smoke-filledenvironment, to evaluate the performance of the TOR (TacticallOcatoR) system. The performed tests included realisticfirefighter movements and inter-agent distances, factors that arecrucial in order to provide realistic evaluations of the expectedperformance in real-world operations. The tests indicate that theTOR system may be able to provide a position accuracy ofapproximately two to three meters during realistic firefighteroperations, with only two smoke diving firefighters and onesupervising firefighter within range.

  • 224.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Schüldt, Christian
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. Limes Audio, Sweden .
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Voice radio communication, pedestrian localization, and the tactical use of 3D audio2013In: 2013 International Conference on Indoor Positioning and Indoor Navigation, IPIN 2013, IEEE Computer Society, 2013, p. 6817918-Conference paper (Refereed)
    Abstract [en]

    The relation between voice radio communication and pedestrian localization is studied. 3D audio is identified as a linking technology which brings strong mutual benefits. Voice communication rendered with 3D audio provides a potential low secondary task interference user interface to the localization information. Vice versa, location information in the 3D audio provides spatial cues in the voice communication, improving speech intelligibility. An experimental setup with voice radio communication, cooperative pedestrian localization, and 3D audio is presented and we discuss high level tactical possibilities that the 3D audio brings. Finally, results of an initial experiment, demonstrating the effectiveness of the setup, are presented.

  • 225.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    De Angelis, Alessio
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Aquilanti, Claudia
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Gear scale estimation for synthetic speed pulse generation2011In: 36th IEEE International Conference on Acoustics, Speech, and Signal Processing, IEEE conference proceedings, 2011, p. 1825-1828Conference paper (Refereed)
    Abstract [en]

    In a motorized vehicle a number of easily measurable signals with frequency components related to the rotational speed of the engine can be found, e.g., vibrations, electrical system voltage level, and ambient sound. These signals could potentially be used to estimate the speed and related states of the vehicle. Unfortunately, such estimates would typically require the relations (scale factors) between the frequency components and the speed for different gears to be known. Consequently, in this article we look at the problem of estimating these gear scale factors from training data consisting only of speed measurements and measurements of the signal in question. The estimation problem is formulated as a maximum likelihood estimation problem and heuristics is used to find initial values for a numerical evaluation of the estimator. Finally, a measurement campaign is conducted and the functionality of the estimation method is verified on real data.

  • 226.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    A note on the limitations of ZUPTs and the implications on sensor error modeling2012In: Proceeding of 2012 International Conference on Indoor Positioning and Indoor Navigation (IPIN), 13-15th November 2012, 2012Conference paper (Refereed)
    Abstract [en]

    The limitations of zero-velocity-updates (ZUPTs) for aiding a foot-mounted inertial navigation system (INS) are studied. Multiple significant modeling errors related to the ZUPTs are pointed out and quantified. Their implications for the possibility to estimate systematic inertial sensor errors are discussed and it is argued that modeling and estimating such errors, in foot-mounted ZUPT-aided INSs, should be avoided in many cases.

  • 227.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Aligning the Forces-Eliminating the Misalignments in IMU Arrays2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, no 10, p. 2498-2500Article in journal (Refereed)
    Abstract [en]

    Ultralow-cost single-chip inertial measurement units (IMUs) combined into IMU arrays are opening up new possibilities for inertial sensing. However, to make these systems practical for researchers, a simple calibration procedure that aligns the sensitivity axes of the sensors in the array is needed. In this paper, we suggest a novel mechanical-rotation-rig-free calibration procedure based on blind system identification and a Platonic solid printable using a contemporary 3-D printer. The IMU array is placed inside the Platonic solid, and static measurements are taken with the solid subsequently placed on all sides. The recorded data are then used together with a maximum-likelihood-based approach to estimate the interIMU misalignment and the gain, bias, and sensitivity axis nonorthogonality of the accelerometers. The effectiveness of the method is demonstrated with calibration results from an in-house developed IMU array. MATLAB scripts for the parameter estimation and production files for the calibration device (solid) are provided.

  • 228.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    JOINT STATE AND MEASUREMENT TIME-DELAY ESTIMATION OF NONLINEARSTATE SPACE SYSTEMS2010In: Proc. ISSPA 2010, IEEE , 2010, p. 324-328Conference paper (Refereed)
    Abstract [en]

    Sensor fusion algorithms often assume perfect time synchronization of the sensor clocks. In a practical sensor-actuator setup this is often difficult to achieve which in turn can give rise to systematic errors in the sensor fusion. In this article we suggest how the effect of the synchronization error from an unknown static or slowly varying measurement time-delays in a nonlinear state space system can be handled by linearizing the measurement equation in time. Based on the linearization an augmented system is constructed from which the system states and the delays can be jointly estimated. Expressions for the system, measurement, and covariance matrices of the augmented system are derived. Finally, the feasibility of the suggested approach is demonstrated by an example and a Monte-Carlo simulation.

  • 229.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Performance characterisation of foot-mountedZUPT-aided INSs and other related systems2010In: Proc. IPIN2010, IEEE , 2010, p. 1-7Conference paper (Refereed)
    Abstract [en]

    Foot-mounted zero-velocity-update (ZUPT) aided inertial navigation system (INS) is a conceptually well known with publications in the area typically focusing on improved methods for filtering and addition of sensors and heuristics. Despite this, the performance characteristics, which would ultimately justify and give guidelines for such system modifications of ZUPT-aided INSs and other related systems, are in some aspects poorly documented. Unfortunately, the systems are non-linear, meaning that the performance is dependent on the system set-up, parameter setting, and the true trajectory. This complicates the process of evaluating performance and partially explains the few publications with detailed performance characterisation results. Therefore in this article we suggest and motivate methodologies for evaluating performance of ZUPT-aided INS and other related systems, we apply them to a suggested baseline set-up of the system, and study some aspects of the performance characteristics.

  • 230.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Hari, K.V.S.
    Department of ECE, Indian Institute of Science (IISc).
    Foot-mounted INS for Everybody: An Open-source Embedded Implementation2012In: 2012 IEEE/ION Position Location and Navigation Symposium (PLANS), IEEE , 2012, p. 140-145Conference paper (Refereed)
    Abstract [en]

    We present an open-source, realtime, embedded implementation of a foot-mounted, zero-velocity-update-aided inertial navigation system. The implementation includes both hardware design and software, uses off-the-shelf components and assembly methods, and features a standard USB interface. The software is written in C and can easily be modified to run user implemented a1gorithlUS. The hardware design and the software are released under permissive open-source licenses and production files, source code, documentation, and further resources areavailable at www.openshoe.org. The reproduction cost for a single unit is below $800, with the inertial measurement unit makingup the bulk ($700). The form factor of the implementation is small enough for it to be integrated in the sole of a shoe. A performance evaluation of the system shows a position errors for short trajectories «100 [m)) of ± 0.2-1 % of the traveled distance, depending on the shape of trajectory.

  • 231.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zachariah, Dave
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Realtime Implementation of Visual-aided Inertial Navigation Using Epipolar Constraints2012In: 2012 IEEE/ION Position Location and Navigation Symposium (PLANS), IEEE , 2012, p. 711-718Conference paper (Refereed)
    Abstract [en]

    A real-time implementation and the related theory of a visual-aided inertial navigation system are presented. The entire system runs on a standard laptop with off-the-shelf sensory equipment connected via standard interfaces. The visual-aiding is based on epipolar constraints derived from a finite visual memory. The navigational states are estimated with a squareroot sigma-point Kalman filter. An adaptive visual memory based on  statistical coupling is presented and used to store and discard images selectively. Timing and temporal ordering of sensory data are estimated recursively. The computational cost and complexity of the system is described, and the implementation is discussed in terms of code structure, external libraries, and important parameters. Finally, limited performance evaluation results of the system are presented.

  • 232.
    Nilsson, John-Olof
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zachariah, Dave
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Cooperative localization by dual foot-mounted inertial sensors and inter-agent ranging2013In: EURASIP Journal on Advances in Signal Processing, ISSN 1687-6172, E-ISSN 1687-6180, Vol. 164Article in journal (Refereed)
    Abstract [en]

    The implementation challenges of cooperative localization by dual foot-mounted inertial sensors and inter-agent ranging are discussed and work on the subject is reviewed. System architecture and sensor fusion are identified as key challenges. A partially decentralized system architecture based on step-wise inertial navigation and step-wise dead reckoning is presented. This architecture is argued to reduce the computational cost and required communication bandwidth by around two orders of magnitude while only giving negligible information loss in comparison with a naive centralized implementation. This makes a joint global state estimation feasible for up to a platoon-sized group of agents. Furthermore, robust and low-cost sensor fusion for the considered setup, based on state space transformation and marginalization, is presented. The transformation and marginalization are used to give the necessary flexibility for presented sampling based updates for the inter-agent ranging and ranging free fusion of the two feet of an individual agent. Finally, characteristics of the suggested implementation are demonstrated with simulations and a real-time system implementation.

  • 233. Ohlsson, Martin
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Ohlsson, Jens
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Larm-anordning i fordon2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    An alarm method for vehicles comprises detection (S31) of whether a portable electronic apparatus (100) is connected to an alarm device (200) arranged in a vehicle (150), detection (S32) of whether a predetermined functionality is activated in the portable electronic apparatus (100), and activation (S33) of an alarm when the portable electronic apparatus (100) is unconnected or the predetermined functionality is inactivated.

  • 234.
    Panahandeh, Ghazaleh
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hutchinson, Seth
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Planar-Based Visual Inertial Navigation: Observability Analysis and Motion Estimation2015In: Journal of Intelligent and Robotic Systems, ISSN 0921-0296, E-ISSN 1573-0409, p. 1-23Article in journal (Refereed)
    Abstract [en]

    In this paper, we address the problem of ego-motion estimation by fusing visual and inertial information. The hardware consists of an inertial measurement unit (IMU) and a monocular camera. The camera provides visual observations in the form of features on a horizontal plane. Exploiting the geometric constraint of features on the plane into visual and inertial data, we propose a novel closed form measurement model for this system. Our first contribution in this paper is an observability analysis of the proposed planar-based visual inertial navigation system (VINS). In particular, we prove that the system has only three unobservable states corresponding to global translations parallel to the plane, and rotation around the gravity vector. Hence, compared to general VINS, an advantage of using features on the horizontal plane is that the vertical translation along the normal of the plane becomes observable. As the second contribution, we present a state-space formulation for the pose estimation in the analyzed system and solve it via a modified unscented Kalman filter (UKF). Finally, the findings of the theoretical analysis and 6-DoF motion estimation are validated by simulations as well as using experimental data.

  • 235.
    Panahandeh, Ghazaleh
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Planar-Based Visual Inertial Navigation2015In: Localization and GNSS (ICL-GNSS), 2015 International Conference on, IEEE conference proceedings, 2015, p. 1-8Conference paper (Refereed)
    Abstract [en]

    This paper investigates the problem of visual-inertialnavigation. The proposed navigation system integrates inertialinformation from an inertial measurement unit (IMU) withvisual data from a camera to provide relative pose estimationfor a system which is navigating in an unknown structuralenvironment. The main contribution of this paper is derivationof a novel measurement model based on inertial data and visualplanar features. The proposed formulation is a solution to the6-DoF motion estimation where the IMU-camera movement isnot restricted over a desired navigation plane. Compared toprevious works, which are restricted on using only horizontalplane features, the proposed model is generalized for arbitraryplanar features. The theoretical finding of this study is extensivelyevaluated both with simulation and real world experiments. Thepresented experiments indicate the reliability of the proposedmethod to perform accurate 6-DoF pose estimation.

  • 236.
    Panahandeh, Ghazaleh
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Calibration of an IMU-Camera Cluster Using Planar Mirror Reflection and Its Observability Analysis2015In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 64, no 1, p. 75-88Article in journal (Refereed)
    Abstract [en]

    This paper describes a novel and a low-cost calibration approach to estimate the relative transformation between an inertial measurement unit (IMU) and a camera, which are rigidly mounted together. The calibration is performed by fusing the measurements from the IMU-camera rig moving in front of a planar mirror. To construct the visual observations, we select a set of key features (KFs) attached to the visual inertial rig where the 3-D positions of the KFs are unknown. During calibration, the system is navigating in front of the planar mirror, while the vision sensor observes the reflections of the KFs in the mirror, and the inertial sensor measures the system's linear accelerations and rotational velocities over time. Our first contribution in this paper is studying the observability properties of IMU-camera calibration parameters. For this visual inertial calibration problem, we derive its time-varying nonlinear state-space model and study its observability properties using the Lie derivative rank condition test. We show that the calibration parameters and the 3-D position of the KFs are observable. As our second contribution, we propose an approach for estimating the calibration parameters along with the 3-D position of the KFs and the dynamics of the analyzed system. The estimation problem is then solved in the unscented Kalman filter framework. We illustrate the findings of our theoretical analysis using both simulations and experiments. The achieved performance indicates that our proposed method can conveniently be used in consumer products like visual inertial-based applications in smartphones for localization, 3-D reconstruction, and surveillance applications.

  • 237.
    Panahandeh, Ghazaleh
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Observability Analysis of Mirror-Based IMU-Camera Self-Calibration2013In: IPIN 2013: 4th International Conference on Indoor Positioning and Indoor Navigation, 2013Conference paper (Refereed)
  • 238.
    Panahandeh, Ghazaleh
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Mohammadiha, Nasser
    KTH, School of Electrical Engineering (EES), Sound and Image Processing (Closed 130101).
    Leijon, Arne
    KTH, School of Electrical Engineering (EES), Sound and Image Processing (Closed 130101).
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Chest-Mounted Inertial Measurement Unit for Pedestrian Motion Classification Using Continuous Hidden Markov Model2012In: 2012 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), IEEE , 2012, p. 991-995Conference paper (Refereed)
    Abstract [en]

    This paper presents a method for pedestrian motionclassification based on MEMS inertial measurement unit (IMU)mounted on the chest. The choice of mounting the IMU on thechest provides the potential application of the current study incamera-aided inertial navigation for positioning and personalassistance. In the present work, five categories of the pedestrianmotion including standing, walking, running, going upstairs,and going down the stairs are considered in the classificationprocedure. As the classification method, the continuous hiddenMarkov model (HMM) is used in which the output densityfunctions are assumed to be Gaussian mixture models (GMMs).The correct recognition rates based on the experimental resultsare about 95%.

  • 239.
    Panahandeh, Ghazaleh
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mohammadiha, Nasser
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Leijon, Arne
    KTH, School of Electrical Engineering (EES), Sound and Image Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Continuous Hidden Markov Model for Pedestrian Activity Classification and Gait Analysis2013In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 62, no 5, p. 1073-1083Article in journal (Refereed)
    Abstract [en]

    This paper presents a method for pedestrian activity classification and gait analysis based on the microelectromechanical-systems inertial measurement unit (IMU). The work targets two groups of applications, including the following: 1) human activity classification and 2) joint human activity and gait-phase classification. In the latter case, the gait phase is defined as a substate of a specific gait cycle, i.e., the states of the body between the stance and swing phases. We model the pedestrian motion with a continuous hidden Markov model (HMM) in which the output density functions are assumed to be Gaussian mixture models. For the joint activity and gait-phase classification, motivated by the cyclical nature of the IMU measurements, each individual activity is modeled by a "circular HMM." For both the proposed classification methods, proper feature vectors are extracted from the IMU measurements. In this paper, we report the results of conducted experiments where the IMU was mounted on the humans' chests. This permits the potential application of the current study in camera-aided inertial navigation for positioning and personal assistance for future research works. Five classes of activity, including walking, running, going upstairs, going downstairs, and standing, are considered in the experiments. The performance of the proposed methods is illustrated in various ways, and as an objective measure, the confusion matrix is computed and reported. The achieved relative figure of merits using the collected data validates the reliability of the proposed methods for the desired applications.

  • 240.
    Panahandeh, Ghazaleh
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Mohammadiha, Nasser
    KTH, School of Electrical Engineering (EES), Sound and Image Processing (Closed 130101).
    Leijon, Arne
    KTH, School of Electrical Engineering (EES), Sound and Image Processing (Closed 130101).
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Pedestrian Motion Classification via Body-Mounted Inertial Measurement Unit2012Conference paper (Other academic)
  • 241. Pasku, Valter
    et al.
    De Angelis, Alessio
    Moschitta, Antonio
    Carbone, Paolo
    Nilsson, John-Olof
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    A Magnetic Ranging Aided Dead-Reckoning Indoor Positioning System for Pedestrian Applications2016In: 2016 IEEE INTERNATIONAL INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE PROCEEDINGS, IEEE conference proceedings, 2016, p. 1526-1531Conference paper (Refereed)
    Abstract [en]

    This paper investigates the applicability of a developed magnetic ranging and positioning system (MPS) as a support for a dead reckoning inertial navigation system for pedestrian applications. The integrated system combines the complementary properties of the separate systems, operating over long periods of time and in cluttered indoor areas with partial non-line-of-sight conditions. The obtained results show that the proposed approach can effectively improve the coverage area of the MPS and the operation time with bounded errors of the dead reckoning based system.

  • 242. Pasku, Valter
    et al.
    De Angelis, Alessio
    Moschitta, Antonio
    Carbone, Paolo
    Nilsson, John-Olof
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Dwivedi, Satyam
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    A Magnetic Ranging-Aided Dead-Reckoning Positioning System for Pedestrian Applications2017In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 66, no 5, p. 953-963Article in journal (Refereed)
    Abstract [en]

    This paper investigates the applicability of a developed Magnetic Positioning System (MPS) as a support for a dead-reckoning inertial navigation system (DR-INS) for pedestrian applications. The integrated system combines the complementary properties of the separate systems, operating over long periods of time and in cluttered indoor areas with partial nonline-of-sight conditions. The obtained results show that the proposed approach can effectively improve the coverage area of the MPS and the operation time with bounded errors of the DR-INS. In particular, a solution that provides bounded position errors of 1-2 m over significantly long periods of time up to 45 min, in realistic indoor environments, is demonstrated. Moreover, system applicability is also shown in those scenarios where arbitrary orientations of the MPS mobile node are considered and an MPS position estimate is not available due to less than three distance measurements.

  • 243. PETTERSSON, Mikael
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    SKOGLUND, Mikael
    FULL SCALE CALIBRATION OF ANALOG-TO-DIGITAL CONVERSION2000Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    Methods and arrangements enable ADCs (105) to be calibrated from reference signals with unknown parameters and/or with amplitudes that exceed the dynamic range of the ADCs (105). A given analog reference signal s(t) is supplied to an ADC (105). The output x(k) of the ADC (105) is used by calibration logic (320) to estimate at least one paramater of the reference signal. A FIR filter (455) accepts as input the x(k) signals and outputs and estimate ((k)) as the sampled instances of thes(t) signal. A reconstruction table is created that approximates the analog input signal in the digital domain using the knowledge of the analog input signal waveform type. The actual ADC (105) outputs are compared to the values in the reconstruction table to produce a correction table (350) for calibration. In an alternative embodiment, calibration logic (320) interpolates the output (x(k)) of the ADC (105) to reconstruct clipped portion(s) of the input analog reference signal s(t) when the amplitude of the input analog reference signals s(t) exceeds the full swing of the ADC (105). The FIR filter can thereafter use the reconstructed signal from the interpolation.

  • 244.
    Prasad, Sathyaveer
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Medawar, Samer
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Beckman, Claes
    Estimation of the Rician K-factor in Reverberation Chambers for Improved Repeatability in Terminal Antenna Measurements2008In: 30th Annual Symposium of the Antenna Measurement Techniques Association (AMTA), Boston, Mass.: AMTA , 2008Conference paper (Refereed)
    Abstract [en]

    The in-network performance of the mobile phone depends highly on the terminal antennas. Their performance may reduce the coverage and the capacity of the whole network. Hence, an antenna measurement method that accurately emulates the in-network radio environment is much desired.

    The reverberation, or mode-stirred, chamber is a cavity resonator with a high Q factor used for testing the performance of terminals and terminal antennas in a controlled field environment. In order to create a homogeneous field inside the chamber, emulating an isotropic multipath environment, mode stirrers are used.

    The Rician K-factor is a statistical parameter that describes the field distribution in the chamber and is defined as the ratio of the unstirred to stirred field components in the chamber. This K-factor varies from zero to infinity. In order to be able to accurately repeat a measurement performed in a reverberation chamber it is, hence, of greatest importance to accurately determine the Rician K-factor from said measurements.

    In this paper, a statistical model for the electromagnetic fields in reverberation chamber is reviewed for a Line of Sight (LOS) environment. An Estimator of the Rician K-factor is derived and its accuracy is verified.

  • 245. Prateek, G. V.
    et al.
    Girisha, R.
    Hari, K. V. S.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Data fusion of dual foot-mounted INS to reduce the systematic heading drift2013In: Fourth International Conference on Intelligent Systems, Modelling and Simulation (ISMS 2013), 2013, p. 208-213Conference paper (Refereed)
    Abstract [en]

    In this report, we investigate the problem of applying a range constraint in order to reduce the systematic heading drift in a foot-mounted inertial navigation system (INS) (motion-tracking). We make use of two foot-mounted INS, one on each foot, which are aided with zero-velocity detectors. A novel algorithm is proposed in order to reduce the systematic heading drift. The proposed algorithm is based on the idea that the separation between the two feet at any given instance must always lie within a sphere of radius equal to the maximum possible spatial separation between the two feet. A Kalman filter, getting one measurement update and two observation updates is used in this algorithm.

  • 246. Rantakokko, J.
    et al.
    Nygards, J.
    Strömbäck, P.
    Andersson, P.
    Nilsson, John Olof
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Integration of GNSS-receivers with dual foot-mounted INS in urban and indoor environments2016In: Proceedings of the IEEE/ION Position, Location and Navigation Symposium, PLANS 2016, Institute of Electrical and Electronics Engineers (IEEE), 2016, p. 589-598Conference paper (Refereed)
    Abstract [en]

    In safety-critical applications, including firefighter and law enforcement operations, infrastructure-free localization systems are typically required. These systems must provide accurate localization in all scenarios. Seamless indoor and outdoor localization and navigation, including in dense urban environments, are needed. Multi-sensor fusion algorithms constitute an integral part in all state-of-the-art indoor positioning systems. GNSS-receivers typically provide poor estimates of their own position uncertainty in dense urban and indoor environments, where significant position errors can be expected, which makes the design of a robust sensor fusion algorithm a challenge. Sensor fusion strategies for integration of a GNSS-receiver with foot-mounted inertial navigation systems (INS) are described and evaluated in this work. For a loosely coupled integration strategy, we suggest to use a cut-off criteria that governs when to discard the GNSS-positions and demonstrate that it can improve the position and heading accuracy in outdoor/indoor transition regions. Similarly, for a tightly coupled integration strategy, we suggest an approach with heavy-tailed measurement noise and demonstrate its capability to suppress inconsistent data and improve performance in the same regions.

  • 247. Rantakokko, Jouni
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Positionering av krishanteringspersonal vid räddningsinsatser: redovisning av genomfört seminarium2007Report (Other academic)
    Abstract [en]

    Genom att utveckla ett väl fungerande personburet positioneringssystem avsett för räddningspersonal kan många liv räddas vid framtida räddningsinsatser. Det gäller exempelvis vid katastrofinsatser, saneringsinsatser, polisiära och militära insatser. Ett väl fungerande robust positioneringssystem på indivvidnivå möjliggör en effektiv ledning av insatsen och ger betydligt utökade möjligheter för en lyckad, säker insats. Det ger dessutom möjlighet att i efterhand följa upp och analysera händelseförlopp under insatsen. Positioneringssystem existerar redan idag, bl a i form av satellitnavigeringssystem som GPS, men deras prestanda är vid ett stort antal räddningsinsatser sannolikt otillräckliga. Det är möjligt att väsentligt förbättra noggrannheten och tillförlitligheten för dessa system. Vinnova projekt 2006-02576 är en förstudie där positionering av krishanteringspersonal vid räddningsinsatser studeras. Denna rapport är en kompilerad form av det material som gicks igenom vid ett seminarium 2007-06-19 och är komplement till de officiella projektrapporterna TRITA-EE 2007:036 Positionering av krishanteringspersonal vid räddningsinsatser - scenarion och användarbehov TRITA-EE 2007:037 Positioning of emergency personnel in rescue operations - possibilities and vulnerabilities with existing techniques and identification of needs for future R&D

  • 248. Rantakokko, Jouni
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Positionering av krishanteringspersonal vid räddningsinsatser: scenarion och användarbehov2007Report (Other academic)
  • 249. Rantakokko, Jouni
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Positioning of incident responders scenarios, user requirements and technological enablers2007Conference paper (Refereed)
  • 250. Rantakokko, Jouni
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Eklöf, Fredrik
    Boberg, Bengt
    Junered, Marcus
    Akos, Dennis
    Skog, Isaac
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Bohlin, Hans
    Neregård, Fredrik
    Hoffmann, Franz
    Andersson, Daniel
    Jansson, Magnus
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Stenumgaard, Peter
    Positioning of emergency personnel in rescue operations: possibilities and vulnerabilities with existing techniques and identification of needs for future R&D2007Report (Other academic)
    Abstract [en]

    Summary and recommendations Presently, GPS-equipped mobile phones are launched at a large scale, enabling a variety of positioning based services. Indeed, GPS is expected to be the future killer application for mobile phones and services. The concept of accurate positioning by technical means implies a large number of applications not only for the mass market, but also for rescue services, fire brigades, police forces, and military and so on. For professional and governmental safety-of-life services the current systems are far from usable and large efforts have to be concentrated on research and development. Technologies based on GPS and other satellite-based positioning systems alone are vulnerable and are expected to malfunction in indoor or challenging electromagnetic environments, or due to antagonistic measures. Satellite-based positioning is a key component in a robust communication and positioning system aimed for first responders. Satellite based positioning in combination with local radio-based positioning systems and dead-reckoning or inertial navigation systems are enablers to fulfill the users? requirements on accuracy and availability of the positioning service. Sweden is a competent player within security. Around 300 companies with some 22.000 employees have been identified within the area. Swedish industry, research institutes and universities are expected to take part in international consortiums within EU FP7, as well as being a player within DHS funded research and development within the personal positioning and navigation area. The market potential for professional and safety-of-life personal equipment for robust positioning and communication with suitable means for information presentation is significant. In the US and the EU there are some 2 million incident responders each. On a national level we count some 35.000 fire fighters, police, and military personnel in international operations. A migration of the technology to private end-consumers as implemented in consumer electronics opens up a gigantic market for wireless services within navigation, gaming, and position-awareness services. Within the project positioning of first responders in rescue operations, robust positioning has been studied. From a system perspective, technologies for positioning of personnel are key system components within a platform for positioning, information transfer for command and control, and information processing and presentation for the personnel at all levels. \? Systems for training are needed to introduce the end-user to the technology, and for training and simulation of novel strategies enabled by the technology. Stationary training systems can be implemented with state-of-the art positioning methods. Feedback from the end-user to the R&D community is instrumental in the specification and development of future means for positioning of first responders. A research infrastructure, or test-bed, for implementation and evaluation of robust positioning is an essential tool. \? The functionality of the equipment has to be robust against hostile electromagnetic environments, either due to the actual physical environment (indoor scenario, intersystem interference from nearby electronic equipment, scenario within a large steel constructions, or power plant, etc), or due to electronic warfare antagonistic actions. Research has to be performed in several areas such as channel characterization for radio positioning, quality of satellite signals subjected to interference, and integrity of sensor information due to external influences. \? Contemporary MEMS-technology provides small-size sensors with low energy consumption. The rapid development within sensor technologies enables data fusion from a plurality of sensors by digital signal processing. Fundamental issues within digital signal processing have to be studied in several fields, including methods to enhance sensor performance by incorporating behavioral modeling; fusion of digital information from a plurality of sensors; aspects of hardware implementation to fulfill requirements on size, weight and uptime, and software defined receivers for radio-based positioning, communication and mapping. In summary, future systems for positioning of first responders in rescue operations rely on the development of infra-structure aimed for end-users in a training scenario; and a platform for R&D-purposes. In parallel, fundamental issues have to be studied regarding the electromagnetic environment, as well as methodologies in digital signal processing.

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