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  • 251. Rantakokko, Jouni
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fredholm, M.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Marsten-Eklöf, F.
    User Requirements for Localization and Tracking Technology: A Survey of Mission-specific Needs and Constraints2010In: 2010 International Conference on Indoor Positioning and Indoor Navigation, IPIN 2010, 2010Conference paper (Refereed)
    Abstract [en]

    Current advances in localization and tracking technology have the potential to develop into much-needed tools for the saving of lives in emergency response and rescue missions, and for the safe-keeping of lives in military operations. However, civilian and military users face different environments and consequently have different user requirements. Even within the two broad fields of civilian and military applications, different types of personnel and indeed different types of missions face different needs and constraints. For instance, firefighters engaged in the suppression of a forest fire have other requirements than firefighters suppressing a fire in a high-rise building, or a conflagration in a large industrial complex full of hazardous materials. Military personnel engaged in counter-insurgency operations face requirements different from those tasked to rescue hostages held in a closed environment. This paper aims to survey the different requirements for localization and tracking technology by mission type, so that users can more easily determine their own specific technology needs. Although primarily aimed to describe requirements for military personnel, law enforcement officers, and firefighters, needs and constraints for several types of civilian applications are covered as well. Despite differences in requirements, it makes sense to develop technologies that will target several of these end-user groups. A new joint facility for development of requirements together with representatives from the various branches, and the evaluation of existing and emerging localization and tracking systems, would assist in the enabling of reliable and user-friendly capability to respond to, and recover from, all-hazards emergencies and combat operations.

  • 252.
    Rantakokko, Jouni
    et al.
    Swedish Defence Research Agency, FOI.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rydell, Joakim
    Emilsson, Erika
    Working towards scenario-based evaluations of first responder positioning systems2011Conference paper (Refereed)
    Abstract [en]

    It is indeed a challenge to create a highly-accurate positioning system for GPS-denied environments, such as indoors and in dense urban environments, or during harsh electromagnetic interference conditions. A priori information concerning for instance building layouts, magnetic field or image information obtained through extensive pre-surveying, or pre-installed infrastructure (e.g. RFID-units or WiFi base-stations), will not be available in many scenarios. However, a reliable positioning system with seamless outdoor and indoor coverage would increase the safety of first responders significantly. Such a system should be lightweight, small, power efficient and relatively inexpensive, yet still provide a high accuracy during extended indoor operations. A camera-based reference system which provides reliable ground truth data in relatively large indoor environments, using a minimum of pre-installed infrastructure, has been designed and evaluated. The reference system will be used to evaluate how errors in for instance foot-mounted inertial navigation systems (INS) or pedestrian dead-reckoning systems grow over time. Loop-closure error analysis is not sufficient for the evaluations of INS since the shape of the trajectory influences the position error. A low-cost, lightweight reference system is often needed when attempting to evaluate the performance of high-accuracy positioning systems during scenario-based exercises. In this work ARToolKitPlus have been used to estimate the camera position relative to a set of pre-installed visual markers. Experiments performed in a very accurate VICON lab show that the toolkit provides sufficient localization accuracy for the intended accuracy. The error is normally less than 0.1 meters at a distance of 1.75 meters from the marker. When the camera-based reference system is used to evaluate a foot-mounted INS, a number of checkpoints with markers will be passed several times. This way the error growth rate in the IMU-based system can be evaluated. Preliminary results from measurements performed with foot-mounted INS are provided and compared with the reference system. Practical considerations concerning sensor fusion of foot-mounted INS with additional sensors, such as magnetometers, barometric altimeters and GPS, will also be provided and particular needs for continued research are pointed out.

  • 253.
    Rantakokko, Jouni
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Nilsson, John-Olof
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Emilsson, Erika
    Swedish Defence Research Agency (FOI),.
    Rydell, Joakim
    Swedish Defence Research Agency (FOI),.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Localization and mapping technologies: an analysis of firefighter user needs and desired system functionalities2013Conference paper (Other academic)
  • 254. Rantakokko, Jouni
    et al.
    Rydell, Joakim
    Fors, Karina
    Linder, Sara
    Wirkander, Sven-Lennart
    Skog, Isaac
    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.
    Technologies for first responder indoor localization2009Conference paper (Refereed)
  • 255. Rantakokko, Jouni
    et al.
    Rydell, Joakim
    Strömbäck, Peter
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Callmer, Jonas
    Törnqvist, David
    Gustafsson, Fredrik
    Jobs, Magnus
    Grudén, Mathias
    Accurate and reliable soldier and first responder indoor positioning: multisensor systems and cooperative localization2011In: IEEE wireless communications, ISSN 1536-1284, E-ISSN 1558-0687, Vol. 18, no 2, p. 10-18Article in journal (Refereed)
    Abstract [en]

    A robust, accurate positioning system with seamless outdoor and indoor coverage is a highly needed tool for increasing safety in emergency response and military urban operations. It must be lightweight, small, inexpensive, and power efficient, and still provide meter-level accuracy during extended operations. GPS receivers, inertial sensors, and local radio-based ranging are natural choices for a multisensor positioning system. Inertial navigation with foot-mounted sensors is suitable as the core system in GPS denied environments, since it can yield meter-level accuracies for a few minutes. However, there is still a need for additional supporting sensors to keep the accuracy at acceptable levels during the duration of typical soldier and first responder operations. Suitable aiding sensors are three-axis magnetometers, barometers, imaging sensors, Doppler radars, and ultrasonic sensors. Furthermore, cooperative positioning, where first responders exchange position and error estimates in conjunction with performing radio-based ranging, is deemed a key technology. This article provides a survey on technologies and concepts for high accuracy soldier and first responder positioning systems, with an emphasis on indoor positioning.

  • 256.
    Rojas, Cristian R.
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Zetterberg, Per
    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.
    Transceiver Inphase/Quadrature Imbalance, Ellipse Fitting, and the Universal Software Radio Peripheral2011In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 60, no 11, p. 3629-3639Article in journal (Refereed)
    Abstract [en]

    In this paper, we introduce a method for inphase/quadrature imbalance parameter estimation based on ellipse fitting. The performance of the method is analytically derived. In particular, it is shown that the method exhibits a small bias (which can be negligible under some standard practical conditions) and a variance slightly above the Cramer-Rao bound. The method is then applied to measurements from a contemporary BiCMOS transceiver which is used on one of the most popular daughterboards of the universal software radio peripheral. In our measurements, the phase skew varies up to 5 degrees with the baseband frequency, while the amplitude imbalance varies between 0 and 0.3 dB over carrier frequencies and across hardware units. The time variation, however, is only 0.004 dB in amplitude and 0.06 degrees in phase. This indicates that the units could either be calibrated online when there is no transmission (in a two-antenna MIMO system, one antenna could transmit a calibration signal to the other), or they could be calibrated during production, in which case a table with different carrier and baseband frequencies would be needed. However, there is no need to estimate the parameters on every burst.

  • 257.
    Scarpati, Jose
    et al.
    SCANIA CV, Södertälje, Sweden.
    Wikström, Adam
    Scania CV, Södertälje, Sweden.
    Jönsson, Ola
    Scania CV, Södertälje, Sweden.
    Glav, Ragnar
    Scania CV, Sweden.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Hjalmarsson, Håkan
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Prediction of Engine Noise using Parameterized Combustion Pressure Curves2007In: SAE technical paper series, ISSN 0148-7191Article in journal (Refereed)
    Abstract [en]

    A parameterization for combustion chamber cylinderpressures is tuned to measurements on an inline 6cylinder Diesel engine at different operating conditions.Both measured and modeled signals are filtered in thefrequency domain and according to the so called Lucasattenuation. Two different estimates of engine radiatednoise are obtained and compared in this fashion. Theinfluence of physically meaningful parameters on thefrequency contents of the final noise level is analyzed,as well as the contribution of the pressure trace of themotored engine. The scattering of data in the pressuresignal is calculated as a function of the crank angleallowing for statistical considerations.

  • 258.
    Schüldt, Christian
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Blind low-complexity estimation of reverberation time2013In: 2013 IEEE Workshop on Applications of Signal Processing to Audio and Acoustics (WASPAA), IEEE conference proceedings, 2013, p. 6701875-Conference paper (Refereed)
    Abstract [en]

    Real-time blind reverberation time estimation is of interest in speech enhancement techniques such as e.g. dereverberation and microphone beamforming. Advances in this field have been made where the diffusive reverberation tail is modeled and the decay rate is estimated using a maximum-likelihood approach. Various methods for reducing the computational complexity have also been presented. This paper proposes a method for even further computational complexity reduction, by more than 60% in some cases, and it is shown through simulations that the results of the proposed method are very similar to that of the original.

  • 259.
    Schüldt, Christian
    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.
    Decay Rate Estimators and Their Performance for Blind Reverberation Time Estimation2014In: IEEE/ACM Transactions on Audio, Speech, and Language Processing, ISSN 2329-9290, Vol. 22, no 8, p. 1274-1284Article in journal (Refereed)
    Abstract [en]

    Several approaches for blind estimation of reverberation time have been presented in the literature and decay rate estimation is an integral part of many, if not all, of such approaches. This paper provides both an analytical and experimental comparison, in terms of the bias and variance of three common decay rate estimators; a straight-forward linear regression approach as well as two maximum-likelihood based methods. Situations with and without interfering additive noise are considered. It is shown that the linear regression based approach is unbiased if no smoothing is applied, and that the estimation variance in the absence of noise is constantly about twice that of the maximum-likelihood based methods. It is shown that the methods that do not take possible noise into account suffer from similar estimation bias in the presence of noise. Further, a hybrid method, combining the noise robustness and low computational complexity advantages of the two different maximum-likelihood based methods, is presented.

  • 260.
    Schüldt, Christian
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Noise robust integration for blind and non-blind reverberation time estimation2015In: Acoustics, Speech and Signal Processing (ICASSP), 2015 IEEE International Conference on, IEEE Signal Processing Society, 2015, p. 56-60Conference paper (Refereed)
    Abstract [en]

    The estimation of the decay rate of a signal section is an integral component of both blind and non-blind reverberation time estimation methods. Several decay rate estimators have previously been proposed, based on, e.g., linear regression and maximum-likelihood estimation. Unfortunately, most approaches are sensitive to background noise, and/or are fairly demanding in terms of computational complexity. This paper presents a low complexity decay rate estimator, robust to stationary noise, for reverberation time estimation. Simulations using artificial signals, and experiments with speech in ventilation noise, demonstrate the performance and noise robustness of the proposed method.

  • 261.
    Schüldt, Christian
    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.
    On Implications of the ISO 3382 Backward Integration Method for Automated Decay Rate Estimation2015In: Journal of The Audio Engineering Society, ISSN 0004-7554, Vol. 63, no 3, p. 161-173Article in journal (Refereed)
    Abstract [en]

    The Schröder backward integration method for estimating the reverberation time of an enclosure, as suggested in the ISO 3382 standard, is analyzed from an estimation theoretic perspective, in a general context that is applicable to both blind and non-blind estimation. Expressions for the estimation bias and variance of the reverberation decay rate are derived and verified using Monte-Carlo simulations. Comparison is made with a straight-forward linear regression method (not using backward integration). It is shown that, even though significantly reducing the estimation variance, the use of backward integration can in many cases mitigate the estimation accuracy due to large bias. This clearly indicates that prudence is called for when using backward integration for automated decay rate estimation problems.

  • 262. Sikula, Josef
    et al.
    Händel, Peter
    University of Missouri-Saint Louis.
    Truong, Amanda M.
    Quantum 1/f noise in bio-chemical resonant ZnO sensors2007In: Noise and Fluctuations, 2007, Vol. 922, p. 339-342Conference paper (Refereed)
    Abstract [en]

    Resonant sensors are based on the adsorption of a mass delta m of the biological or chemical agent on the surface of the resonant element. Corresponding antibodies with efficiency x are deployed on the resonator face. The adsorption gets detected by a reduction y =delta omega/omega =-kappa delta m/m of the resonance frequency omega of the ZnO crystal. However, the latter is also subject to fundamental Q1/f frequency fluctuations with spectrum S-y(f). The quantum 1/f limit of detection is given by (delta m/m)(min)=(2ln2)(1/2)[S-y(1Hz)](1/2)/kappa.

  • 263.
    Simón Colomar, David
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    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.
    Smoothing for ZUPT-aided INSs2012In: 2012 International Conference on Indoor Positioning and Indoor Navigation, IPIN 2012 - Conference Proceedings, IEEE conference proceedings, 2012, p. 6418869-Conference paper (Refereed)
    Abstract [en]

    Due to the recursive and integrative nature of zero-velocity-update-aided (ZUPT-aided) inertial navigation systems (INSs), the error covariance increases throughout each ZUPT-less period followed by a drastic decrease and large state estimate corrections as soon as ZUPTs are applied. For dead-reckoning with foot-mounted inertial sensors, this gives undesirable discontinuities in the estimated trajectory at the end of each step. However, for many applications, some degree of lag can be tolerated and the information provided by the ZUPTs at the end of a step can be made available throughout the step, eliminating the discontinuities. For this purpose, we propose a smoothing algorithm for ZUPT-aided INSs. For near real-time applications, smoothing is applied to the data in a step-wise manner requiring a suggested varying-lag segmentation rule. For complete off-line processing, full data set smoothing is examined. Finally, the consequences and impact of smoothing are analyzed and quantified based on real-data.

  • 264.
    Skog, Isaac
    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.
    A low-cost GPS aided inertial navigation system for vehicle applications2005Conference paper (Refereed)
    Abstract [en]

    In this paper an approach for integration between GPS and inertial navigation systems (INS) is described. The continuous-time navigation and error equations for an earth-centered earth-fixed INS system are presented. Using zero order hold sampling, the set of equations is discretized. An extended Kalman filter for closed loop integration between the GPS and INS is derived. The filter propagates and estimates the error states, which are fed back to the INS for correction of the internal navigation states. The integration algorithm is implemented on a host PC, which receives the GPS and inertial measurements via the serial port from a tailor made hardware platform, which is briefly discussed. Using a battery operated PC the system is fully mobile and suitable for real-time vehicle navigation. Simulation results of the system are presented.

  • 265.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Calibration of a MEMS inertial measurement unit2006In: Proc. XVII IMEKO World Congress, (Rio de Janeiro, Brazil), Sept.2006, 2006Conference paper (Refereed)
    Abstract [en]

    An approach for calibrating a low-cost IMU isstudied, requiring no mechanical platform for the accelerometercalibration and only a simple rotating table for the gyrocalibration. The proposed calibration methods utilize the factthat ideally the norm of the measured output of the accelerometerand gyro cluster are equal to the magnitude of appliedforce and rotational velocity, respectively. This fact, togetherwith model of the sensors is used to construct a cost function,which is minimized with respect to the unknown model parametersusing Newton’s method. The performance of the calibrationalgorithm is compared with the Cram´er-Rao bound forthe case when a mechanical platform is used to rotate the IMUinto different precisely controlled orientations. Simulation resultsshows that the mean square error of the estimated sensormodel parameters reaches the Cram´er-Rao bound within8 dB, and thus the proposed method may be acceptable for awide range of low-cost applications.

  • 266.
    Skog, Isaac
    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.
    Effects of time synchronization errors in GNSS-aided INS2008In: 2008 IEEE/ION POSITION, LOCATION AND NAVIGATION SYMPOSIUM, VOLS 1-3, NEW YORK: IEEE , 2008, p. 370-376Conference paper (Refereed)
    Abstract [en]

    The effects of time synchronization errors in a GNSS-aided inertial navigation system (INS) are studied in terms of the increased error covariance of the state vector. Expressions for evaluating the error covariance of the navigation state vector-given the vehicle trajectory and the model of the INS error dynamics-are derived. Two different cases are studied in some detail. The first case considers a navigation system in which the timing error is not included in the integration filter. This leads to a system with an increased error covariance and a bias in the estimated forward acceleration. In the second case, a parameterization of the timing error is included as a part of the estimation problem in the data integration. Simulation results show that by including the timing error in the estimation problem, almost perfect time synchronization is obtained and the bias in the forward acceleration is removed.

  • 267.
    Skog, Isaac
    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.
    In-car navigation basics2012In: Handbook of Intelligent Vehicles / [ed] Eskandarian, Azim (Ed.), Springer Publishing Company, 2012Chapter in book (Other academic)
  • 268.
    Skog, Isaac
    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.
    In-Car Positioning and Navigation Technologies: a survey2009In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 10, no 1, p. 4-21Article, review/survey (Refereed)
    Abstract [en]

    In-car positioning and navigation has been a killer application for Global Positioning System (GPS) receivers, and a variety of electronics for consumers and professionals have been launched on a large scale. Positioning technologies based on stand-alone GPS receivers are vulnerable and, thus, have to be supported by additional information sources to obtain the desired accuracy, integrity, availability, and continuity of service. A survey of the information sources and information fusion technologies used in current in-car navigation systems is presented. The pros and cons of the four commonly used information sources, namely, 1) receivers for radio-based positioning using satellites, 2) vehicle motion sensors, 3) vehicle models, and 4) digital map information, are described. Common filters to combine the information from the various sources are discussed. The expansion of the number of satellites and the number of satellite systems, with their usage of available radio spectrum, is an enabler for further development, in combination with the rapid development of microelectromechanical inertial sensors and refined digital maps.

  • 269.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Automatic Control. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Indirect Instantaneous Car-Fuel Consumption Measurements2014In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 63, no 12, p. 3190-3198Article in journal (Refereed)
    Abstract [en]

    A method to estimate the instantaneous fuel consumption of a personal car, using speed and height data recorded by a global positioning system receiver and vehicle parameters accessible via national vehicle registers and databases on the world wide web, is proposed. The method is based upon a physical model describing the relationship between the dynamics of the car, engine speed, and energy consumption of the system. An evaluation of the proposed method is done by comparing the estimated instantaneous fuel consumption with that measured by the car's onboard diagnostics data bus. The results of three tests with different cars driven in mixed highway and urban conditions indicate that the instantaneous fuel consumption may be estimated with a root mean square error of similar to 0.3 [g/s], in terms of a normalized mean square error, that corresponded to slightly <10%. One application of the proposed method is in the development of smartphone applications that educate drivers to drive more fuel efficiently.

  • 270.
    Skog, Isaac
    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.
    Synchronization by Two-Way Message Exchanges: Cramer-Rao Bounds, Approximate Maximum Likelihood, and Offshore Submarine Positioning2010In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 58, no 4, p. 2351-2362Article in journal (Refereed)
    Abstract [en]

    Accurate clock synchronization is vital to many applications of wireless sensor networks (WSNs). The availability of a mathematical tool that at an early design stage can provide insight into the theoretically achievable performance of the clock synchronization may accordingly be valuable in the initial design phase of the network. Therefore, the achievable clock synchronization accuracy is examined in a WSN employing a two-way message exchange model under a Gaussian assumption. The Cramer-Rao bound for the estimation of the clock parameters is derived for four different parameterizations (i. e., different nuisance parameters), reflecting different levels of prior knowledge concerning the system parameters. The results on the Cramer-Rao bound are transformed into a lower bound on the mean square error of the clock offset, a figure of merit often more relevant, characterizing the system performance. Further, by introducing a set of artificial observations through a linear combination of the observations originally obtained in the two-way message exchange, an approximate maximum likelihood estimator for the clock parameters is proposed. The estimator is shown to be of low complexity and it obeys near-optimal performance, that is, a mean square error in the vicinity of the Cramer-Rao bound. The applicability of the derived results is shown through a simulation study of an offshore engineering scenario, where a remotely operated underwater vehicle is used for operations at the seabed. The position of the vehicle is tracked using a WSN.

  • 271.
    Skog, Isaac
    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.
    Time Synchronization Errors in Loosely Coupled GPS-Aided Inertial Navigation Systems2011In: IEEE transactions on intelligent transportation systems (Print), ISSN 1524-9050, E-ISSN 1558-0016, Vol. 12, no 4, p. 1014-1023Article in journal (Refereed)
    Abstract [en]

    The effects of data time synchronization errors in a loosely coupled Global-Positioning-System (GPS)-aided inertial navigation system (INS) are studied and quantified in terms of the increased mean square error (MSE) of the navigation solution. An expression for evaluating the MSE of the navigation solution, given the vehicle trajectory and the model of the INS error dynamics, is derived. Thereafter, a software-based time synchronization method, where the time synchronization error is included as a state to be estimated by the data integration filter, is proposed. A practical approach to the implementation of the proposed time synchronization method is also briefly described. Moreover, an expression for the MSE of the navigation solution in the system that employs the proposed synchronization method is derived. Finally, through simulations and tests with real-world data, the correctness of the derived MSE expressions is validated, and the application of the proposed synchronization method is shown. The test results show that, with the proposed synchronization approach, a data time synchronization, which is accurate to the order of a few milliseconds, can be achieved.

  • 272.
    Skog, Isaac
    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.
    Nilsson, John-Olof
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Rantakokko, Jouni
    Zero-Velocity Detection-An Algorithm Evaluation2010In: IEEE Transactions on Biomedical Engineering, ISSN 0018-9294, E-ISSN 1558-2531, Vol. 57, no 11, p. 2657-2666Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the problem of detecting-time epochs when zero-velocity updates can be applied in a foot-mounted inertial navigation (motion-tracking) system. We examine three commonly used detectors: the acceleration-moving variance detector, the acceleration-magnitude detector, and the angular rate energy detector. We demonstrate that all detectors can be derived within the same general likelihood ratio test (LRT) framework, given the different prior knowledge about the sensor signals. Further, by combining all prior knowledge, we derive a new LRT detector. Subsequently, we develop a methodology to evaluate the performance of the detectors. Employing the developed methodology, we evaluate the performance of the detectors using leveled ground, slow (approximately 3 km/h) and normal (approximately 5 km/h) gait data. The test results are presented in terms of detection versus false-alarm probability. Our preliminary results show that the new detector performs marginally better than the angular rate energy detector that outperforms both the acceleration-moving variance detector and the acceleration-magnitude detector.

  • 273.
    Skog, Isaac
    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.
    Ohlsson, Martin
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ohlsson, Jens
    Challenges in smartphone-driven usage based insurance2013In: 2013 IEEE Global Conference on Signal and Information Processing, GlobalSIP 2013 - Proceedings, IEEE conference proceedings, 2013, p. 1135-1135Conference paper (Refereed)
    Abstract [en]

    Usage Based Insurance (UBI) programs for car insurance is becoming mainstream using tailored vehicle mounted hardware, where the commercial initiatives can be traced back to the mid-nineties [1]. The smartphone has been identified as an enabler for future UBI, replacing the vehicle (after-) mounted dedicated hardware with a ubiquitous device with a plurality of sensors, means for data processing and wireless communication. This presentation addresses some signal processing challenges in smartphone-driven UBI.

  • 274.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    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.
    An open-source multi inertial measurement unit (MIMU) platform2014In: 1st IEEE International Symposium on Inertial Sensors and Systems, ISISS 2014 - Proceedings, IEEE Computer Society, 2014Conference paper (Refereed)
    Abstract [en]

    An open-source low-cost multi inertial measurement unit (MIMU) systems platform is presented. First, the layout and system architecture of the platform, as well as the novel communication interface used to simultaneously communicate with the 18 IMUs in the platform are described. Thereafter, the potential gains of using a MIMU system are described and discussed. Finally, the error characteristics of the platform, when stationary, are illustrated using Allan variance plots.

  • 275.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Nilsson, John-Olof
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Handel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Nehorai, Arye
    Inertial Sensor Arrays, Maximum Likelihood, and Cramer-Rao Bound2016In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 64, no 16, p. 4218-4227Article in journal (Refereed)
  • 276.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    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.
    Evaluation of zero-velocity detectors for foot-mounted inertial navigation systems2010In: 2010 International Conference on Indoor Positioning and Indoor Navigation, IPIN 2010, 2010Conference paper (Refereed)
    Abstract [en]

    A study of the performance of four zero-velocity detectors for a foot-mounted inertial sensor based pedestrian navigation system is presented. The four detectors are the acceleration moving variance detector, the acceleration magnitude detector, the angular rate energy detector, and a novel generalized likelihood ratio test detector, refereed to as the SHOE. The performance of each detector is assessed by the accuracy of the position solution provided by the navigation system employing the detector to perform zero-velocity updates. The results show that for leveled ground forward gait at a speed of 5 km/h, the angular rate energy detector and the SHOE give the highest performance, with a position accuracy of 0.14% of the travelled distance. The results also indicate that during leveled ground forward gait, the gyroscope signals hold the most reliable information for zerovelocity detection.

  • 277.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    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.
    Pedestrian tracking using an IMU array2014In: 2014 IEEE International Conference on Electronics, Computing and Communication Technologies (IEEE CONECCT), IEEE Computer Society, 2014, p. 6740346-Conference paper (Refereed)
    Abstract [en]

    Ubiquitous and accurate tracking of pedestrians are an enabler for a large range of emerging and envisioned services and capabilites. To track pedestrians in prevailing indoor environments, inertial measurement units (IMUs) may be used to implement foot-mounted inertial navigation. Today emerging ultra-low-cost IMUs are taking a leading role in the advancement of the IMU performance-to-cost boundary. Unfortunately, the performance of these IMUs are still insufficient to allow extended stand-alone tracking. However, the size, price, and power consumption of single-chip ultra-low-cost IMUs makes it possible to combine multiple IMUs on a single PCB, creating an IMU array. The feasibility of such hardware has recently been demonstrated. On the other hand, the actual gain of using such multi-IMU systems in the pedestrian tracking application is unclear. Therefore, based on an in-house developed IMU array, in the article we demonstrate that foot-mounted inertial navigation with an IMU array is indeed possible and benefitial. The error characteristics of the setup and different ways of combining the inertial measurements are studied and directions for further research are given.

  • 278.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    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), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Signal Processing.
    Nehorai, Arye
    Arrays of single-chip IMUs2015In: Proc. International Conference on Indoor Positioning and Indoor Navigation (IPIN), Calgary, Canada: University of Calgary , 2015Conference paper (Refereed)
    Abstract [en]

    The development of ultralow-cost single-chip IMUs nowmake it feasible to construct massive IMU arrays. Such arrays giveproperties not attainable by single IMUs. Specifically, non-colocatedaccelerometers provide rotational information with complementary char-acteristics to that provided by the gyroscopes. In this poster we reviewthe signal model of multi-IMU systems and present experimental resultsfrom an in-house developed IMU array.

  • 279.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Nilsson, John-Olof
    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.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Fusing the information from two navigation systems using an upper bound on their maximum spatial separation2012In: 2012 International Conference on Indoor Positioning and Indoor Navigation, IPIN 2012 - Conference Proceedings, IEEE , 2012, p. 6418862-Conference paper (Refereed)
    Abstract [en]

    A method is proposed to fuse the information from two navigation systems whose relative position is unknown, but where there exists an upper limit on how far apart the two systems can be. The proposed information fusion method is applied to a scenario in which a pedestrian is equipped with two foot-mounted zero-velocity-aided inertial navigation systems; one system on each foot. The performance of the method is studied using experimental data. The results show that the method has the capability to significantly improve the navigation performance when compared to using two uncoupled foot-mounted systems.

  • 280.
    Skog, Isaac
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Schumacher, Adrian
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    A versatile PC-based platform for inertial navigation2007In: Proceedings of the 7th Nordic Signal Processing Symposium, NORSIG 2006, New York: IEEE , 2007, p. 262-265Conference paper (Refereed)
    Abstract [en]

    A GPS aided inertial navigation platform is presented, into which further sensors such as a camera, wheel-speed encoder etc., can be incorporated. The construction of the platform is described and an introduction to the sensor fusion approach is given. Results from a field-test is presented, indicating which error sources that needs to be modelled more accurately.

  • 281. Sorqvast, Patrik
    et al.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Ottersten, Björn
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Kalman Filtering for Low Distortion Speech Enhancement in Mobile Communications1997In: Proceedings of IEEE International Conference on Acoustics, Speech, and Signal Processing, ICASSP-97., IEEE , 1997, p. 1219-1222Conference paper (Refereed)
    Abstract [en]

    This paper presents a model-based approach for noise suppression of speech contaminated by additive noise. AKalman filter based speech enhancement system is presented and its performance is investigated in detail. It is shown that with a novel speech parameter estimation algorithm, it is possible to achieve 10 dB noise suppression with a high total audible quality.

  • 282. Stoica, P.
    et al.
    Händel, Peter
    Nehorai, A.
    Improved sequential music1995In: IEEE Transactions on Aerospace and Electronic Systems, ISSN 0018-9251, E-ISSN 1557-9603, Vol. 31, no 4, p. 1230-1239Article in journal (Refereed)
    Abstract [en]

    MUSIC (multiple signal classification) is one of the most frequently considered methods for source location using sensor arrays. Among the location methods based on one-dimensional search, MUSIC has excellent performance. in fact, no other one-dimensional method that may outperform MUSIC (in large samples) was known to exist Our goal here is to introduce such a method, called improved sequential MUSIC (IES-MUSIC), which is shown to be strictly more accurate than MUSIC (in large samples). First, a class of sequential MUSIC estimates is introduced, which depend on a scalar-valued user parameter. MUSIC is shown to be a special case of estimate in that class, corresponding to a value of uro for the user parameter. Next, the optimal user parameter value, which minimizes the asymptotic variance of the estimation errors, is derived IES-MUSIC is the method based on that optimal choice of the user parameter. Simulation results which Lend support to the theoretical findings are included.

  • 283. Stoica, P.
    et al.
    Händel, Peter
    Soderstrom, T.
    Approximate maximum-likelihood frequency estimation1994In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 30, no 1, p. 131-145Article in journal (Refereed)
    Abstract [en]

    The high-resolution frequency estimators most commonly used, such as MUSIC, ESPRIT and Yule-Walker, determine estimates of the sinusoidal frequencies from the sample covariances of noise-corrupted data. In this paper, a frequency estimation method termed Approximate Maximum Likelihood (AML) is derived from the approximate likelihood function of sample covariances. The statistical performance of AML is studied, both analytically and numerically, and compared with the Cramer-Rao bound as well as the statistical performance corresponding to the aforementioned methods of frequency estimation. AML is shown to provide the minimum asymptotic error variance in the class of all estimators based on a given set of covariances. The implementation of the AML frequency estimator is discussed in detail. The paper also introduces an AML-based procedure for estimating the number of sinusoidal signals in the measured data, which is shown to possess high detection performance.

  • 284. Stoica, P.
    et al.
    Händel, Peter
    Söderström, T.
    Study of Capon method for array signal processing1995In: Circuits, systems, and signal processing, ISSN 0278-081X, E-ISSN 1531-5878, Vol. 14, no 6, p. 749-770Article in journal (Refereed)
    Abstract [en]

    The mean-square error (MSE) of Capon estimate of the directions-of-arrival (DOA) is established in the narrowband array processing case. An improved Capon-like DOA estimator is proposed and its MSE is studied as well. Performance comparisons between the standard and improved Capon DOA estimates, and between these two estimates and the linear prediction DOA estimate, are performed. It is concluded that the improved Capon-like method introduced in this paper provides more accurate DOA estimates in most cases.

  • 285. Stokes, V. P.
    et al.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Comments on "On amplitude and frequency demodulation using energy operators"1998In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 46, no 2, p. 506-507Article in journal (Refereed)
  • 286. Strömback, Peter
    et al.
    Rantakokko, Jouni
    Wirkander, Sven-Lennart
    Alexandersson, Mikael
    Fors, Karina
    Skog, Isaac
    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.
    Foot-Mounted Inertial Navigation and Cooperative Sensor Fusion for Indoor Positioning2010In: Proceedings of the 2010 International Technical Meeting of The Institute of Navigation, 2010, p. 89-98Conference paper (Refereed)
    Abstract [en]

    In this paper we examine the effect of introducing an opportunistic cooperative navigation approach between soldiers, or first responders, equipped with foot-mounted IMUs and UWB-ranging equipment. The foot-mounted navigation system is based on a 15-state Extended Kalman filter, utilizing zero-velocity updates. The addition of range measurements between cooperative units displayed a significant improvement of the navigation accuracy in the studied scenarios. This approach has the potential to enable accurate positioning for several minutes in GPS-denied environments. Furthermore, the performance of the UWB-ranging sensor is examined and the resulting error statistics and typical ranging distances are characterized in indoor environments.

  • 287.
    Strömberg, Dino
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    De Angelis, Alessio
    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.
    A Low-Complexity Adaptive-Threshold Detector for Pulse UWB Systems2011Conference paper (Refereed)
    Abstract [en]

    A method for adaptively setting the threshold of an energy detector for Ultra-Wideband radio systems is presented in this paper. The method, which is suitable for low-complexity and low-cost implementation, is based on the estimation of the input noise and interference power. Simulations and experimental results obtained from a prototype UWB system show that the proposed method can adaptively set the threshold of the detector. Therefore it is robust to changes in the interference power, and it can limit the false alarm rate.

  • 288. Tichavsky, P.
    et al.
    Händel, Peter
    Efficient tracking of multiple sinusoids with slowly varying parameters1993In: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing, 1993, Vol. 3, p. 368-371Conference paper (Refereed)
    Abstract [en]

    An algorithm for tracking the parameters of slowly time-varying multiple sine waves in noise is proposed. The estimates of the instant frequencies are updated directly using a simple property of the one-step increment of the phases. The algorithm is based on the recursive least squares method with exponential weighting factor. The risetime and the noise rejection characteristics of the algorithm are studied theoretically in the single complex sine wave case, assuming that the SNR is sufficiently high. The proposed algorithm is easy to implement, and computer simulations show that it yields good results.<>

  • 289. Tichavsky, P.
    et al.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Estimating parameters of polynomial phase signals by tracking algorithms1998In: 1998 9th IEEE SP Workshop on Statistical Signal and Array Processing, 1998, p. 348-351Conference paper (Refereed)
    Abstract [en]

    Polynomial phase signals are encountered for example in pulse compression radar systems. A recently proposed ldquo;multiple frequency tracker rdquo; in combination with a polynomial fitting procedure are shown to perform well in estimating parameters of polynomial phase signals. In comparison with the popular discrete polynomial-phase transform, the proposed method is shown to have a significantly lower SNR threshold, while retaining a low computational complexity

  • 290. Tichavsky, P.
    et al.
    Händel, Peter
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Multicomponent polynomial phase signal analysis using a tracking algorithm1999In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 47, no 5, p. 1390-1395Article in journal (Refereed)
    Abstract [en]

    We describe an efficient technique analyzing signals that comprise a number of polynomial-phase components, The technique is based on a recently proposed "multiple frequency tracker," which is an algorithm for recursive estimation of parameters of multiple sine waves in noise, It has a relatively low SNR threshold and moderate computational complexity.

  • 291. Tichavsky, P.
    et al.
    Händel, Peter
    Recursive estimation of frequencies and frequency rates of multiple cisoids in noise1997In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 58, no 2, p. 117-129Article in journal (Refereed)
    Abstract [en]

    A recursive algorithm for simultaneous estimation and tracking of instantaneous frequencies and instantaneous frequency rates-of-change for signals that consist of multiple narrow-band components in noise is proposed and studied. The algorithm recursively separates the signal to individual components and uses estimated phase differences for updating the instantaneous frequency and frequency rate of each component. The main advantages of the proposed algorithm over frequencies-only tracking algorithms known in literature include the zero asymptotic bias (zero tracking delay) in estimating of the instantaneous frequencies of linear FM (chirp) signals and more accurate tracking of frequencies that cross each other. Performance of the algorithm is studied by means of a linear filter approximation technique and derived results are compared with the appropriate (posterior) Cramer-Rao bound. Superior performance of the algorithm is illustrated by computer simulations.

  • 292. Tichavsky, P.
    et al.
    Händel, Peter
    Recursive estimation of linearly or harmonically modulated frequencies of multiple cisoids in noise1997In: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing, 1997, Vol. 3, p. 1925-1928Conference paper (Refereed)
    Abstract [en]

    Recursive estimation of parameters of linearly or harmonically frequency modulated sinusoidal signals is considered. The algorithms simultaneously separate the measured signal to individual components and update signal parameters using estimated phase differences. The main advantages of the proposed algorithms over standard tracking schemes such as e.g. the adaptive notch filter is zero asymptotic bias (zero tracking delay) in estimating of the instantaneous frequencies

  • 293. Tichavsky, P.
    et al.
    Händel, Peter
    Two algorithms for adaptive retrieval of slowly time-varying multiple cisoids in noise1995In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 43, no 5, p. 1116-1127Article in journal (Refereed)
    Abstract [en]

    Two algorithms for tracking parameters of slowly varying multiple complex sine waves (cisoids) in noise (the multiple frequency tracker and the adaptive notch filter) are described, For high signal-to-noise ratio (SNR), the properties of the algorithms (i.e., stability, noise rejection, and tracking speed) are studied analytically using a linear filter approximation technique, The tradeoff between noise rejection and tracking error for both algorithms is shown to be similar, Different choices of the design variables are discussed, namely i) minimal mean-square estimation error for random walk modeled frequency variations and ii) minimal stationary estimation variance subject to a given tracking delay.

  • 294. Tichavsk’y, Petr
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Estimation and smoothing of instantaneous frequency of noisy narrow band signals2000In: Proceedings European Signal Processing Conference, 2000, p. 1803-1806Conference paper (Refereed)
  • 295. Trehag, J.
    et al.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Ögren, M.
    Onboard Estimation and Classification of a Railroad Curvature2010In: IEEE Transactions on Instrumentation and Measurement, ISSN 0018-9456, E-ISSN 1557-9662, Vol. 59, no 3, p. 653-660Article in journal (Refereed)
    Abstract [en]

    When performing tests on a rail vehicle, it is often necessary to categorize the target data according to the characteristics of the railroad plane geometry. In this paper, a method to classify and identify the railroad plane geometry is considered, employing railroad curvature readings formed by onboard sensor data. The aim is to extract the characteristics of the railroad track to identify and categorize different segments of the track. The railroad curvature is modeled as a first-order piecewise linear polynomial representing sections of straight tracks, transition curves, and circular curves along the railroad. The sensor data are preprocessed in a Global Positioning System-aided dead reckoning navigation system to debias the curvature readings. Subsequently, the noise in the curvature readings is suppressed by nonlinear filtering techniques. Furthermore, the observed curvatures are processed with a linear filter by minimizing a discounted least-squares criterion, yielding the final estimate of the railroad curvature and its rate of change, which further on are utilized to form a detector where the position of a trend change in curvature measurements is located. The result from the presented method has been compared against database values on plane geometry from Banverkets Information System-a system belonging to the Swedish Rail Administration office. The reported accuracy of detecting a change in the railroad curvature has varied in the range of +/- 7 m in difference between the position entries in the curvature database and the positions found with the developed method.

  • 296.
    Venkitaraman, Arun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Extreme learning machine for graph signal processing2018In: 2018 26th European Signal Processing Conference (EUSIPCO), European Signal Processing Conference, EUSIPCO , 2018, p. 136-140, article id 8553088Conference paper (Refereed)
    Abstract [en]

    In this article, we improve extreme learning machines for regression tasks using a graph signal processing based regularization. We assume that the target signal for prediction or regression is a graph signal. With this assumption, we use the regularization to enforce that the output of an extreme learning machine is smooth over a given graph. Simulation results with real data confirm that such regularization helps significantly when the available training data is limited in size and corrupted by noise.

  • 297.
    Venkitaraman, Arun
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Chatterjee, Saikat
    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), Signal Processing. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Graph linear prediction results in smaller error than standard linear prediction2015In: 2015 23rd European Signal Processing Conference, EUSIPCO 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015, p. 220-224Conference paper (Refereed)
    Abstract [en]

    Linear prediction is a popular strategy employed in the analysis and representation of signals. In this paper, we propose a new linear prediction approach by considering the standard linear prediction in the context of graph signal processing, which has gained significant attention recently. We view the signal to be defined on the nodes of a graph with an adjacency matrix constructed using the coefficients of the standard linear predictor (SLP). We prove theoretically that the graph based linear prediction approach results in an equal or better performance compared with the SLP in terms of the prediction gain. We illustrate the proposed concepts by application to real speech signals.

  • 298.
    Venkitaraman, Arun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    MULTI-KERNEL REGRESSION FOR GRAPH SIGNAL PROCESSING2018In: 2018 IEEE INTERNATIONAL CONFERENCE ON ACOUSTICS, SPEECH AND SIGNAL PROCESSING (ICASSP), IEEE, 2018, p. 4644-4648Conference paper (Refereed)
    Abstract [en]

    We develop a multi-kernel based regression method for graph signal processing where the target signal is assumed to be smooth over a graph. In multi-kernel regression, an effective kernel function is expressed as a linear combination of many basis kernel functions. We estimate the linear weights to learn the effective kernel function by appropriate regularization based on graph smoothness. We show that the resulting optimization problem is shown to be convex and propose an accelerated projected gradient descent based solution. Simulation results using real-world graph signals show efficiency of the multi-kernel based approach over a standard kernel based approach.

  • 299.
    Venkitaraman, Arun
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Chatterjee, Saikat
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Händel, Peter
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    On Hilbert transform, analytic signal, and modulation analysis for signals over graphs2019In: Signal Processing, ISSN 0165-1684, E-ISSN 1872-7557, Vol. 156, p. 106-115Article in journal (Refereed)
    Abstract [en]

    We propose Hilbert transform and analytic signal construction for signals over graphs. This is motivated by the popularity of Hilbert transform, analytic signal, and modulation analysis in conventional signal processing, and the observation that complementary insight is often obtained by viewing conventional signals in the graph setting. Our definitions of Hilbert transform and analytic signal use a conjugate symmetry-like property exhibited by the graph Fourier transform (GFT), resulting in a 'one-sided' spectrum for the graph analytic signal. The resulting graph Hilbert transform is shown to possess many interesting mathematical properties and also exhibit the ability to highlight anomalies/discontinuities in the graph signal and the nodes across which signal discontinuities occur. Using the graph analytic signal, we further define amplitude, phase, and frequency modulations for a graph signal. We illustrate the proposed concepts by showing applications to synthesized and real-world signals. For example, we show that the graph Hilbert transform can indicate presence of anomalies and that graph analytic signal, and associated amplitude and frequency modulations reveal complementary information in speech signals.

  • 300.
    Voet, Kevin
    et al.
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Händel, Peter
    KTH, School of Electrical Engineering (EES), Signal Processing.
    Björsell, Niclas
    Van Moer, Wendy
    Mirrored parallel Hammerstein predistortion for multitone generation2011In: 2011 IEEE INTERNATIONAL INSTRUMENTATION AND MEASUREMENT TECHNOLOGY CONFERENCE (I2MTC), 2011, p. 814-817Conference paper (Refereed)
    Abstract [en]

    The paper discusses the approach tested for digital pre-distortion of radio frequency vector signal generators, where joint mitigation of impairments is considered stemming from the inphase/quadrature modulator, local oscillator, and power amplifier. A predistorter structure, linear in its parameters, was taken and the parameters were estimated by the least-squares method. The proposed method is validated by demonstrating improvement in the performance of the Rohde & Schwarz SMU200 by about 8 dB reduction in mirror-frequency interference, 17 dB reduction in leakage from the local oscillator, and 6 dB improvement in inter-modulation products. Thus, the tested approach is considered useful for several instrumentation and measurement applications.

34567 251 - 300 of 343
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