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  • 201.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Segmentation of Signals Using Piecewise Constant Linear Regression Models1994Report (Other academic)
    Abstract [en]

    The signal segmentation approach described herein assumes that the signal can be accurately modelled by a linear regression with piece-wise constant parameters. A simultaneous estimate of the change times is considered. The maximum likelihood and maximum a posteriori probability estimates are derived after marginalization of the linear regression parameters and the measurement noise variance, which are considered as nuisance parameters. A well-known problem is that the complexity of segmentation increases exponentially in the number of data. Therefore, two inequalities are derived enabling the exact estimate to be computed with quadratic complexity. A linear in time complexity recursive approximation is proposed as well, based on these inequalities. The method is evaluated on a speech signal previously analyzed in literature, showing that a comparable result is obtained directly without the usual tuning effort. It is also detailed how it successfully has been applied in a car for online segmentation of the driven path for supporting guidance systems.

  • 202.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Signals and Systems Lab2008Other (Other academic)
  • 203.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Slip-Based Estimation of Tire-Road Friction1995In: Proceedings of the 3rd Eropean Control Conference, 1995, p. 725-730Conference paper (Refereed)
    Abstract [en]

    An approach to estimate the tire road friction during normal drive using only the wheel slip, that is, the relative difference in wheel velocities, is presented. The driver can be informed about the maximal friction force and be alarmed for sudden changes. Friction related parameters are estimated using only signals from standard sensors in a modern car, and the physical relation between these parameters and the maximal friction force is determined from extensive field trials using a Volvo 850 GLT as a test car.

  • 204.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Slip-Based Estimation of Tire-Road Friction1995Report (Other academic)
    Abstract [en]

    An approach to estimate the tire road friction during normal drive using only the wheel slip, that is, the relative difference in wheel velocities, is presented. The driver can be informed about the maximal friction force and be alarmed for sudden changes. Friction related parameters are estimated using only signals from standard sensors in a modern car, and the physical relation between these parameters and the maximal friction force is determined from extensive field trials using a Volvo 850 GLT as a test car.

  • 205.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Slip-Based Estimation of Tire-Road Friction1997In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 33, no 6, p. 1087-1099Article in journal (Refereed)
    Abstract [en]

    An approach to estimate the tire-road friction during normal drive using only the wheel slip, that is, the relative difference in wheel velocities, is presented. The driver can be informed about the maximum friction force and be alarmed for sudden changes. Friction-related parameters are estimated using only signals from standard sensors in a modern car. An adaptive estimator is presented for a model linear in parameters, which is designed to work for periods of poor excitation, errors in variables, simultaneous slow and fast parameter drifts and abrupt changes. The physical relation between these parameters and the maximal friction force is determined from extensive field trials using a Volvo 850 GLT as a test car.

  • 206.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Statistical sensor fusion2010 (ed. 1)Book (Other academic)
    Abstract [en]

    Sensor fusion deals with Merging information from two or more sensors. Elsewhere the area of statistical signal processing provides a powerful toolbox to attack bothering theoretical and practical problems. The objective of this book is to explain state of the art theory and algorithms into statistical sensor fusion, covering estimation, detection and non-linear filtering theory with applications to localisation, navigation and tracking problems. The book starts with a review of the theory on linear and non-linear estimation, with a focus on sensor network applications. Then, general non-linear filter theory is surveyed with a Particular attention to Different variants of the Kalman filter and the particle filter. Complexity and implementation issues are discussed in detail. Simultaneous localisation and mapping (SLAM) is distressed as a challenging application area of high-dimensional non-linear filtering problems. The book spans the whole range from mathematical foundations provided in Extensive Appendices, to real-world problems the covered in a party surveying standard sensors, motion models and applications in this field. All models and algorithms are available as object-oriented Matlab code with an Extensive data file library, and the examples, Which are richly distressed to illustrate the theory, are supplemented by fully reproducible Matlab code.

  • 207.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Statistical Signal Processing Approaches to Fault Detection2006In: Proceedings of the 6th IFAC Symposium on Fault Detection, Supervision and Safety of Technical Processes, 2006, p. 24-35Conference paper (Refereed)
    Abstract [en]

    The parity space approach to fault detection and isolation (FDI) has beendeveloped during the last twenty years, and the focus here is to describe its applicationto stochastic systems. A mixed model with both stochastic inputs and deterministicdisturbances and faults is formulated over a sliding window. Algorithms for detecting andisolating faults on-line and analyzing the probability for correct and incorrect decisionsoff-line are provided. A major part of the paper is devoted to discussing properties ofthis model-based approach and generalizations to cases of incomplete model knowledge,and non-linear non-Gaussian models. For this purpose, a simulation example is usedthroughout the paper for numerical illustrations, and real-life applications for motivations.The final section discusses the reverse problem: fault detection approaches to statisticalsignal processing. It is motivated by three applications that a simple CUSUM detectorin feedback loop with an adaptive filter can mitigate the inherent trade-off betweenestimation accuracy and tracking speed in linear filters.

  • 208.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Statistical Signal Processing Approaches to Fault Detection2007In: Annual Reviews in Control, ISSN 1367-5788, E-ISSN 1872-9088, Vol. 31, no 1, p. 41-54Article in journal (Refereed)
    Abstract [en]

    The parity space approach to fault detection and isolation (FDI) has been developed during the last 20 years, and the focus here is to describe its application to stochastic systems. A mixed model with both stochastic inputs and deterministic disturbances and faults is formulated over a sliding window. Algorithms for detecting and isolating faults on-line and analyzing the probability for correct and incorrect decisions off-line are provided. A major part of the paper is devoted to discussing properties of this model-based approach and generalizations to cases of incomplete model knowledge, and non-linear non-Gaussian models. For this purpose, a simulation example is used throughout the paper for numerical illustrations, and real-life applications for motivations. The final section discusses the reverse problem: fault detection approaches to statistical signal processing. It is motivated by three applications that a simple CUSUM detector in feedback loop with an adaptive filter can mitigate the inherent trade-off between estimation accuracy and tracking speed in linear filters.

  • 209.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Statistical Signal Processing for Automotive Safety Systems2005In: Proceedings of the 13th IEEE/SP Workshop on Statistical Signal Processing, IEEE , 2005, p. 1345-1352Conference paper (Other academic)
    Abstract [en]

    The amount of software in general and safety systems in particular increases rapidly in the automotive industry. The trend is that functionality is decentralized, so new safety functions are distributed to common shared computer hardware, sensors and actuators using central data buses. This paper overviews recent and future safety systems, and highlights the big challenges for researchers in the signal processing area.

  • 210.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Stochastic Fault Diagnosability in Parity Spaces2002In: Proceedings of the 15th IFAC World Congress, 2002, p. 736-736Conference paper (Refereed)
    Abstract [en]

    We here analyze the parity space approach to fault detection and isolation in a stochastic setting. Using a state space model with both deterministic and stochastic unmeasurable inputs we show a formal relationship between the Kalman filter and the parity space. Based on a statistical fault detection and diagnosis algorithm, the probability for incorrect diagnosis is computed explicitly, given that only a single fault with known time profile has occurred. An example illustrates how the matrix of diagnosis probabilities can be used as a design tool for performance optimization with respect to, for instance, design variables and sensor placement and quality.

  • 211.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Stochastic Observability and Fault Diagnosis of Additive Changes in State Space Models2002In: Proceedings of the 2001 IEEE International Conference on Acoustics, Speech, and Signal Processing, 2002, p. 2833-2836 vol.5Conference paper (Refereed)
    Abstract [en]

    We derive a Kalman filter based on data from a sliding window. This is used for a new approach to fault detection and diagnosis, where the state estimate from past data is compared to the state estimate of some of the future data. We suggest a method to judge the quality of diagnosis in a simple way. For fault estimation in the diagnosis, the general concept of stochastic observability in linear systems is introduced. Its role on the design step is illustrated on a problem of estimating the true velocity of a car.

  • 212.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Test Drives for Tire-Road Friction Estimation1994Report (Other academic)
  • 213.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    The Marginalized Likelihood Ratio Test for Detecting Abrupt Changes1994Report (Other academic)
    Abstract [en]

    The generalized likelihood ratio (GLR) test is a widely used method for detecting abrupt changes in linear systems and signals. In this paper the marginalized likelihood ratio (MLR) test is introduced for eliminating three shortcomings of GLR while preserving its applicability and generality. First, the need for a user-chosen threshold is eliminated in MLR. Second, the noise levels need not be known exactly and may even change over time, which means that MLR is robust. Finally, a very efficient exact implementation with linear in time complexity for batch-wise data processing is developed. This should be compared to the quadratic in time complexity of the exact GLR.

  • 214.
    Gustafsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    The Marginalized Likelihood Ratio Test for Detecting Abrupt Changes1996In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 41, no 1, p. 66-78Article in journal (Refereed)
    Abstract [en]

    The generalized likelihood ratio (GLR) test is a widely used method for detecting abrupt changes in linear systems and signals. In this paper the marginalized likelihood ratio (MLR) test is introduced for eliminating three shortcomings of GLR while preserving its applicability and generality. First, the need for a user-chosen threshold is eliminated in MLR. Second, the noise levels need not be known exactly and may even change over time, which means that MLR is robust. Finally, a very efficient exact implementation with linear in time complexity for batch-wise data processing is developed. This should be compared to the quadratic in time complexity of the exact GLR.

  • 215.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Bergman, Niclas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Three Statistical Batch Algorithms for Tracking Manoeuvring Targets1999In: Proceedings of the 5th European Control Conference, 1999Conference paper (Refereed)
    Abstract [en]

    The EM algorithm and two MCMC algorithms are applied to manoeuvre detection in target tracking. These statistical methods are off-line and the intended use is to compute upper performance limits of on-line algorithms as well as for off-line analysis. A consequence of the MCMC theory is that an approximation of the a posteriori distribution for the manoeuvre times is obtained.

  • 216.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Constrained Power Control in Cellular Systems Subject to Time Delays1998In: Proceedings of Reglermöte 1998, 1998Conference paper (Other academic)
  • 217.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Mobile Communication Systems - An Object-Oriented Simulation Environment1997In: Proceedings of the Nordic MATLAB Conference 97, 1997Conference paper (Refereed)
  • 218.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Power Control Algorithms and Stability Analysis for Radio Network Control1998In: Proceedings of the 37th IEEE Conference on Decision and Control, 1998, p. 2041-2042 vol.2Conference paper (Refereed)
    Abstract [en]

    Power control algorithms in cellular radio networks are analyzed. This is basically a MIMO problem where the controlled input is the powers used by the transmitters, and the measurements consist of signal to interference ratios for each receiver. These algorithms can, for each single connection and neglecting the cross couplings, be interpreted as a feedback system. The main contribution here is to analyze a generic control algorithm, which covers some important suggested classical control theory methods such as the root locus and describing function. The results include the important conclusion that unavoidable time delays and nonlinearities (saturation and quantization) in the feedback loop can cause a considerable loss in the stability margin. The results are supported by simulations.

  • 219.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Power Control in Cellular Systems Subject to Constraints and Time Delays1998In: Proceedings of the 1998 IEEE Global Telecommunications Conference, 1998, p. 3645-3650 vol.6Conference paper (Refereed)
    Abstract [en]

    Stability is a fundamental property desirable for any controlled system. We briefly review the root locus and describing function techniques, which are tools for stability analysis, and show how they can be applied to power control algorithms in cellular radio networks. The root locus method is used to find stability limits on controller parameters, and describing functions for predicting the presence of oscillations in the system. Thus these methods can be used to support the design phase, when deciding upon the appropriate controller parameters. These tools are demonstrated for various control algorithms and when different smoothing filters are applied. The analysis reveals that the distributed power control (DPC) algorithm, which works fine under ideal circumstances, yields an unstable system when subject to a small time delay. Furthermore, it is concluded that the performance with respect to stability is better when the measurements are averaged by an exponential forgetting filter than by the moving average filter.

  • 220.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Carlemalm, Catharina
    Uppsala University, Sweden.
    MAP based schemes for detection of double talk and abrupt changes in the echo path for fading channels1998In: Proceedings of the 9th European Signal Processing Conference, 1998Conference paper (Refereed)
    Abstract [en]

    An algorithm for discrimination and detection of the two phenomena double talk and abrupt changes in the echo path is proposed for fading channels. Being able to discriminate and detect these two phenomena is crucial since the echo canceler must react differently. The suggested detection scheme is based on a sequential detection approach. The communication channel is modeled as a randomly time-varying linear system. An autoregressive model is used to describe the time evolution of the channel taps. The channel parameters are identified using a Kalman filter coupled with a recursive least squares algorithm, and, based on model assumptions, the maximum a posteriori probabilities corresponding to double talk and abrupt echo path changes are calculated. The proposed scheme is verified experimentally by way of computer simulations.

  • 221.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Carlemalm, Catharina
    Royal Institute of Technology, Sweden.
    Wahlberg, Bo
    Royal Institute of Technology, Sweden.
    On the Problem of Detection and Discrimination of Double Talk and Change in the Echo Path1996In: Proceedings of the 1996 IEEE International Conference on Acoustics, Speech and Signal Processing, 1996, p. 2742-2745 vol.5Conference paper (Refereed)
    Abstract [en]

    The problem of detection and discrimination of double talk and change in the echo path in a telephone channel is considered. The phenomenon echo path change requires fast adaptation of the channel model to be able to equalize the echo dynamics. On the other hand, the adaption rate should be reduced when double talk occurs. Thus, it is critical to quickly detect a change in the echo path while not confusing it with double talk, which gives a similar effect. The proposed likelihood based approach compares a global channel model with a local one over a sliding window, both estimated with the recursive least squares algorithm.

  • 222.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ekström, Håkan
    Tire-Road Friction Estimation Results from Field Trials in Arvidsjaur1993Report (Other academic)
  • 223.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Fauske, Kjell Magne
    University Graduate Center Kjeller, Norway.
    Hegrenaes, Øyvind
    University Graduate Center Kjeller, Norway.
    Estimation of AUV Dynamics for Sensor Fusion2007In: Proceedings of the 10th International Conference on Information Fusion, IEEE , 2007, p. 1-6Conference paper (Refereed)
    Abstract [en]

    This paper presents a method for identifying dynamic models of autonomous underwater vehicles (AUV) from logged data and a physically motivated model structure. Such models are instrumental for model-based control system design, but also for integrated navigation systems. We motive our work from the perspective of developing second generation integrated navigation systems, which use a sensor fusion approach to merge external information with a dynamic model for purposes of redundancy, integrity, and for fault detection and isolation.

  • 224.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Geijer Lundin, Erik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Uplink Load and Link Budget with Stochastic Noise Rise Levels in CDMA Cellular Systems2004Report (Other academic)
    Abstract [en]

    The limiting factor in the uplink of all CDMA cellular systems is the relation between uplink noise rise and intended coverage. In link budgets, noise rise is usually simply handled as a constant contribution to the background noise in logarithmic scale, often referred to as interference margin. In practice, however, it is not constant. We model the uplink noise rise as a lognormal distribution, and investigate the impact to link budgets. Simulations and numerical calculations show that the uplink noise rise variance does not critically affect the uplink capacity and coverage. System feasibility and its relation to the uplink load is also discussed. It is shown that approximative load expressions provides an upper bound on the uplink load and therefore they can be used to imply system feasibility. Furthermore, the uplink load expressions provide accurate approximations of the load given that the load is within the practical limits given by the link budgets.

  • 225.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Graebe, S. F.
    University of Newcastle, Australia.
    Closed Loop Performance Monitoring in the Presence of System Changes and Disturbances1998In: Automatica, ISSN 0005-1098, E-ISSN 1873-2836, Vol. 34, no 11, p. 1311-1326Article in journal (Refereed)
    Abstract [en]

    This paper addresses issues in closed-loop performance monitoring. Particular attention is paid to detecting whether an observed deviation from nominal performance is due to a disturbance or due to a control relevant system change. This is achieved by introducing a novel performance measure that allows feasible application of a standard CUSUM change detector. The paper includes explicit results on the risk of mistaking a disturbance for a system change. The algorithm has been implemented in real time on a DSP and evaluated on a DC motor.

  • 226.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Graebe, Stefan F
    University of Newcastle, Australia.
    Closed Loop Performance Monitoring in the Presence of System Changes and Disturbances1995In: Proceedings of the 3rd European Control Conference, 1995, p. 453-458Conference paper (Refereed)
    Abstract [en]

    This paper addresses issues in closed loop performance monitoring. Particular attention is paid to detecting whether an observed deviation from nominal performance is due to a disturbance or due to a system change. This is achieved by introducing a novel performance measure that allows feasible application of a standard CUSUM change detector. The paper includes explicit results on the probability of mistaking a disturbance for a system change and demonstrates the algorithm with a simulation study.

  • 227.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Graebe, Stefan F
    University of Newcastle, Australia.
    Closed Loop Performance Monitoring in the Presence of System Changes and Disturbances1995Report (Other academic)
    Abstract [en]

    This paper addresses issues in closed loop performance monitoring. Particular attention is paid to detecting whether an observed deviation from nominal performance is due to a disturbance or due to a system change. This is achieved by introducing a novel performance measure that allows feasible application of a standard CUSUM change detector. The paper includes explicit results on the probability of mistaking a disturbance for a system change and demonstrates the algorithm with a simulation study.

  • 228.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Grönwall, Christina
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A Cramer-Rao Lower Bound Expression for a Scanning Laser Radar System2002In: Proceedings of Reglermöte 2002, 2002, p. 126-129Conference paper (Other academic)
  • 229.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Localization Based on Observations Linear in Log Range2008In: Proceedings of the 17th IFAC World Congress, 2008, p. 10252-10257Conference paper (Refereed)
    Abstract [en]

    AbstractReceived signal strength (RSS) is used in wireless networks as a ranging measurement for positioning and localization services. This contribution studies conceptually different networks, where neither transmitted power or the path decay constant can be assumed to be known. The application in mind is a rapidly deployed network consisting of a number of sensor nodes with low-bandwidth communication, each node consisting of a number of sensor types measuring RSS. Typical sensors measure acoustic, seismic, magnetic and IR power emitted from a target. First, a model linear in the unknown nuisance parameters (transmitted power and path loss constant) is presented and validated from real data. Then, the separable least squares principle is applied to the non-linear least squares (NLS) cost function, after which a cost function of only the unknown position is obtained. Results from field trials are presented to validate the method.

  • 230.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Localization in sensor networks based on log range observations2007In: 2007 PROCEEDINGS OF THE 10TH INTERNATIONAL CONFERENCE ON INFORMATION FUSION, VOLS 1-4, IEEE , 2007, p. 1048-1055Conference paper (Refereed)
    Abstract [en]

    This contribution presents a unified framework for localization and tracking in sensor networks based on fusing a variety of signal energy measurements as provided by for instance acoustic, seismic, magnetic, radio, microwave and infrared sensors. The received energy from such sensors generally decays exponentially, and a log range model is introduced for the sensor observations in logarithmic scale, which is linear in transmitted power and the path loss exponent. Field trial sensor data confirms the validity of the log range model. The novelty in this contribution ties in a systematic least squares approach to eliminate these nuisance parameters and also the sensor noise variances. Details on how to solve the resulting low-dimensional non-linear least squares criterion are given, and how to extend the algorithms to target tracking. Explicit formulas for the Cramer-Rao lower bound are given for both localization and tracking.

  • 231.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Measurements used in Wireless Sensor Networks Localization2009In: Localization Algorithms and Strategies for Wireless Sensor Networks: Monitoring and Surveillance Techniques for Target Tracking / [ed] Guoqiang Mao, Bari Fidan, Information Science Reference, 2009, 1, p. 33-53Chapter in book (Refereed)
    Abstract [en]

    Wireless sensor networks (WSN) localization relies on measurements. Availability of, and the information content in, these measurements depend on the network architecture, connectivity, node time synchronization and the signaling bandwidth between the sensor nodes. This chapter addresses wireless sensor networks measurements in a general framework based on a set of nodes, where each node either emits or receives signals. The emitted signal can for example be a radio, acoustic, seismic, infrared or sonic wave that is propagated in a certain media to the receiver. This general observation model does not make any difference between localization of sensor network nodes or unknown objects, or whether the nodes or objects are stationary or mobile. The information available for localization in wireless cellular networks (WCN) is in literature classified as direction of arrival (DOA), time of arrival (TOA), time difference of arrival (TDOA) and received signal strength (RSS). This chapter generalizes these concepts to the more general wireless sensor networks.

  • 232.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Mobile Positioning using Wireless Networks: Possibilities and Fundamental Limitations based on Available Wireless Network Measurements2005In: IEEE signal processing magazine (Print), ISSN 1053-5888, E-ISSN 1558-0792, Vol. 22, no 4, p. 41-53Article in journal (Refereed)
    Abstract [en]

    Location in wireless networks is of increasing importance for safety, gaming, and commercial services. There are plenty of measurements available today, ranging from signal arrival times to maps of received power. It is demonstrated how fundamental the Fisher information matrix (FIM) for each measurement is to assess possible location performance. As one illustration, the FCC positioning requirements are transformed to requirements on sufficient information. Thus, it is possible to investigate whether specific sensor configurations would provide acceptable accuracy.

  • 233.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Positioning using Time-Difference of Arrival Measurements2003In: Proceedings of the 2003 IEEE International Conference on Acoustics, Speech and Signal Processing, 2003, Vol. 6, p. 553-556 vol.6Conference paper (Refereed)
    Abstract [en]

    The problem of position estimation from Time Difference Of Arrival (TDOA) measurements occurs in a range of applications from wireless communication networks to electronic warfare positioning. Correlation analysis of the transmitted signal to two receivers gives rise to one hyperbolic function. With more than two receivers, we can compute more hyperbolic functions, which ideally intersect in one unique point. With TDOA measurement uncertainty, we face a non-linear estimation problem. We here suggest and compare both a Monte Carlo based method for positioning and a gradient search algorithm using a non-linear least squares framework. The former has the feature to be easily extended to a dynamic framework where a motion model of the transmitter is included. A small simulation study is presented.

  • 234.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Power Control in Wireless Communications Networks - from a Control Theory Perspective2002In: Proceedings of the 15th IFAC World Congress, 2002, p. 935-935Conference paper (Refereed)
    Abstract [en]

    The global communications systems critically relyon control algorithms of various kinds. In wireless communications systems, power control algorithms play an important role for efficient resource utilization. This survey article discusses relevant aspects of power control with emphasis on practical issues, using an automatic control framework. Generally, power control of each connection is distributedly implemented as cascade control, with an inner loop to compensate for fast variations and an outerloop focusing on longer term statistics. These control loops are interrelated via complex connections, which affect important issues such as capacity, load and stability. Therefore, both local and global properties are important. The concepts and algorithms are illustrated by simple examples and simulations.

  • 235.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Bergman, Niclas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Forsell, Urban
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Jansson, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Karlsson, Rickard
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nordlund, Per-Johan
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Particle Filters for Positioning, Navigation and Tracking2002In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 50, no 2, p. 425-437Article in journal (Refereed)
    Abstract [en]

    A framework for positioning, navigation and tracking problems using particle filters (sequential Monte Carlo methods) is developed. It consists of a class of motion models and a general non-linear measurement equation in position. A general algorithm is presented, which is parsimonious with the particle dimension. It is based on marginalization, enabling a Kalman filter to estimate all position derivatives, and the particle filter becomes low-dimensional. This is of utmost importance for high-performance real-time applications. Automotive and airborne applications illustrate numerically the advantage over classical Kalman filter based algorithms. Here the use of non-linear models and non-Gaussian noise is the main explanation for the improvement in accuracy. More specifically, we describe how the technique of map matching is used to match an aircraft's elevation profile to a digital elevation map, and a car's horizontal driven path to a street map. In both cases, real-time implementations are available, and tests have shown that the accuracy in both cases is comparable to satellite navigation (as GPS), but with higher integrity. Based on simulations, we also argue how the particle filter can be used for positioning based on cellular phone measurements, for integrated navigation in aircraft, and for target tracking in aircraft and cars. Finally, the particle filter enables a promising solution to the combined task of navigation and tracking, with possible application to airborne hunting and collision avoidance systems in cars.

  • 236.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Bergman, Niclas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Forssell, Urban
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Jansson, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Karlsson, Rickard
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nordlund, Per-Johan
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Particle Filters for Positioning, Navigation and Tracking2001Report (Other academic)
    Abstract [en]

    A framework for positioning, navigation and tracking problems using particle filters (sequential Monte Carlo methods) is developed. It consists of a class of motion models and a general non-linear measurement equation in position. A general algorithm is presented, which is parsimonious with the particle dimension. It is based on marginalization, enabling a Kalman filter to estimate all position derivatives, and the particle filter becomes low-dimensional. This is of utmost importance for high-performance real-time applications. Automotive and airborne applications illustrate numerically the advantage over classical Kalman filter based algorithms. Here the use of non-linear models and non-Gaussian noise is the main explanation for the improvement in accuracy. More specifically, we describe how the technique of map matching is used to match an aircraft's elevation profile to a digital elevation map, and a car's horizontal driven path to a street map. In both cases, real-time implementations are available, and tests have shown that the accuracy in both cases is comparable to satellite navigation (as GPS), but with higher integrity. Based on simulations, we also argue how the particle filter can be used for positioning based on cellular phone measurements, for integrated navigation in aircraft, and for target tracking in aircraft and cars. Finally, the particle filter enables a promising solution to the combined task of navigation and tracking, with possible application to airborne hunting and collision avoidance systems in cars.

  • 237.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    A New Concept of Power Control in Cellular Systems Reflecting Challenges of Today's Systems1998In: Proceedings of the 1998 IEEE Global Telecommunications Conference, 1998, p. 2097-2102 vol.4Conference paper (Refereed)
    Abstract [en]

    When the systems evolved from analog to digital, the performance was improved by the use of power control on the one hand and different modulations and coding schemes on the other. Condensing the available information we are able to propose a new concept of power control. The concept is applicable to real systems, since it uses the available measurements for estimating parameters necessary for the power control. It also supports the use of an adequate quality measure together with a quality specification supplied by the operator. We will use frequency hopping GSM as an example and the resulting control algorithm is ready for implementation in the software in the base stations where the output powers are computed. No modifications are needed in the GSM standard, the mobile terminals, the radio interfaces or in the base station transmitters. Finally we provide simulation results confirming the benefits of using the new concept for power control.

  • 238.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Constrained Power Control Subject to Time Delays1998In: Proceedings of the 1998 International Conference on Communication Technology, 1998Conference paper (Refereed)
  • 239.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Blom, Jonas
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Estimation in Cellular Radio Systems1999In: Proceedings of the 1999 IEEE International Conference on Acoustics, Speech, and Signal Processing, 1999, p. 2551-2554 vol.5Conference paper (Refereed)
    Abstract [en]

    The problem to track time-varying parameters in cellular radio systems is studied, and the focus is on estimation based only on the signals that are readily available. Previous work have demonstrated very good performance, but were relying on analog measurement that are not available. Most of the information is lost due to quantization and sampling at a rate that might be as low as 2 Hz (GSM case). For that matter a maximum likelihood estimator have been designed and exemplified in the case of GSM. Simulations indicate good performance both when most parameters are varying slowly, and when subject to fast variations as in realistic cases. Since most computations take place in the base stations, the estimator is ready for implementation in a second generation wireless system. No update of the software in the mobile stations is needed.

  • 240.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Geijer Lundin, Erik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Uplink Load Estimation in WCDMA2002In: Proceedings of Radiovetenskap och Kommunikation 2002, 2002Conference paper (Other academic)
    Abstract [en]

    All cellular radio systems depend on well performing radio resource management algorithms to efficiently utilize available resources. These algorithms make their decisions based on some sort of resource quantity. In the uplink of a WCDMA system, the total received power at the base stations is a natural choice of such a quantity. Unfortunately this quantity cannot be measured with enough accuracy to be used by resource management algorithms. One way of getting around this problem is to estimate a closely related quantity, namely the uplink noise rise. In this paper, we propose and evaluate four different methods to estimate the noise rise. The estimates are insensitive to users bit rate and use data readily available in the system. The best performing method estimates, on average, the uplink noise rise with an error of less than 1 dB for practical load scenarios.

  • 241.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Geijer Lundin, Erik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Törnqvist, David
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Transmission Timing - A Control Approach to Distributed Uplink Scheduling in WCDMA2004In: Proceedings of Reglermöte 2004, 2004Conference paper (Other academic)
    Abstract [en]

    Centralized control and coordination of the connections in a wireless network is not possible in practice. To keep the delay from measure-ment instants to actuating the decisions, distributed control is required. This paper focuses on the uplink (from mobiles to base stations) and dis-cusses distributing the decision of when and when not to transmit data (distributed scheduling) to the mobiles. The scheme, uplink transmission timing, utilizes mobile transmitter power control feedback from the base station receiver to determine whether the channel is favorable or not compared to the average channel condition. Thereby, the battery consumption and disturbing power to other connections are reduced. The algorithm can be described as a feedback control system. Some transient behaviors are analyzed using systems theory, and supported by wireless network simulations of a system with a WCDMA (Wideband Code Division Multiple Access) radio interface as in most 3G systems.

  • 242.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Frida
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Aspects on Performance Measurements of TCP Traffic and Its Reflection into Control Theory2002In: Proceedings of Reglermöte 2002, 2002Conference paper (Other academic)
    Abstract [en]

    One of the challenges of the communication world today is to improve the performance of Internet traffic for the changing traffic scenarios of today, e.g., radio transmissions. This leaves us with the question of what good performance is and how we measure it. This work will discuss some issues of performance when using TCP and also present some of the measures that are used today. We will then discuss this matter from the perspective of a bottleneck queue and present a measure that can be used from that view point in the network. This measure is illustrated by comparing two versions of TCP and is used as a base for a discussion of what models will be needed to actually achieve the goals that we have. A control structure is presented that currently is used as a base for the development of a mathematical description of the system. We use the dropping of packets as a control signal, as is done by e.g. ~ RED, and the output signal is the queue length.

  • 243.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Frida
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Issues on Performance Measurements of TCP2002In: Proceedings of Radiovetenskap och Kommunikation 2002, 2002Conference paper (Other academic)
    Abstract [en]

    Due to the rapid growth of the Internet and the use of packet data traffic, the communication world has to find ways of improving performance of this traffic. New areas of use include, e.g., radio transmissions and real time data. This work discusses some issues of performance when using TCP and also present some of the measures that are used today. Furthermore we discuss this matter from the perspective of a bottleneck queue and present a measure that can be used from that viewpoint in the network. This measure is illustrated by comparing two versions of TCP and form the basis for a discussion of what models will be needed to actually achieve the goals that we have. A control structure is presented and using simulations and a control interpretation we note that RED introduces an implicit wanted steady state value of the queue length. We use the dropping of packets as a control signal and the output signal is the queue length.

  • 244.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Frida
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Issues on Performance Measurements of TCP2002In: Proceedings of the 4th Conference on Computer Science and Systems Engineering, 2002Conference paper (Other academic)
    Abstract [en]

    Due to the rapid growth of the Internet and the use of packet datatraffic, the communication world has to find ways of improving performance of this traffic. New areas of use include, e.g., radio transmissions and real time data. This work discusses some issues of performance when using TCP and also present some of the measures that are used today. Furthermore we discuss this matter from the perspective of a bottleneck queue and present a measure that can be used from that view point in the network. This measure is illustrated by comparing two versions of TCP and form the basis for a discussion of what models will be needed to actually achieve the goals that we have. A control structure is presented and using simulations and a control interpretation we note that RED introduces an implicit wanted steady state value of the queue length. We use the dropping of packets as a control signal and the output signal is the queue length.

  • 245.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Frida
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    TCP Performance based on Queue Occupation2001In: Proceedings of the 2001 Nordic Radio Symposium, 2001Conference paper (Refereed)
    Abstract [en]

    The main protocol for flow and congestion control on the Internet is the Transmission Control Protocol, TCP. This protocol was constructed and developed based on heuristic arguments, and its main purpose is to prevent network congestion. Because of changes in the character of the Internet traffic, TCP does not work as well as when it was designed - a problem that has been addressed by researchers in different ways. In this contribution, the bad performance of TCP will be illustrated using queue occupation. Simulations have been made using a simple simulation testbed implemented in the Matlab tools Simulink and StateFlow, as well as a more complex environment in a simulator developed at Berkeley called ns-2. It is seen that a modified TCP implementation yields significant performance improvements.

  • 246.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Frida
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    TCP Performance based on Queue Occupation2001In: Proceedings of the Third Conference on Computer Science and Systems Engineering, 2001, p. 127-134Conference paper (Refereed)
    Abstract [en]

    The main protocol for flow and congestion control on the Internet is the Transmission Control Protocol, TCP. This protocol was constructed and developed based on heuristic arguments, and its main purpose is to prevent network congestion. Because of shifts in the Internet traffic, TCP does not work as well as when it was designed - a problem that has been addressed by researchers in different ways. We will illustrate the bad performance using the queue occupancy and also show that a proposed feedback scheme improves the performance, in a simulation environment.

  • 247.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Frida
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Björsson, Anders
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Knutsson, Björn
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Radio Access Network (UTRAN) Modeling for Heterogenous Network Simulations, A Brief Description2003In: Proceedings of the 1st Swedish National Computer Networking Workshop, 2003Conference paper (Refereed)
    Abstract [en]

    The vision of mobile Internet comprises heterogeneous networks with both wired and wireless infrastructures. The network parts are typically radio access network, core network, service network, Internet, etc. Due to the multitude of nodes and users in such networks and the complicated nature of layered communications protocols, performance analysis through simulations is crucial. The open source network simulation tool, ns-2, is widely used for simulating the behavior of wired, routed networks. This work adds modules to model radio access network nodes that emulate typical behavior of UTRAN (UMTS Terrestrial Radio Access Network) - the 3G standard opted for in Europe and Japan. Furthermore, data communication examples illustrate typical behavior of such a heterogenous network.

  • 248.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, Faculty of Science & Engineering.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Lindgren, David
    Swedish Defence Research Agency, Linköping, Sweden.
    Sensor models and localization algorithms for sensor networks based on received signal strength2012In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 1, no 16Article in journal (Refereed)
    Abstract [en]

    Received signal strength (RSS) can be used in sensor networks as a ranging measurement for positioning and localization applications. This contribution studies the realistic situation where neither the emitted power nor the power law decay exponent be assumed to be known. The application in mind is a rapidly deployed network consisting of a number of sensor nodes with low-bandwidth communication, each node measuring RSS of signals traveled through air (microphones) and ground (geophones). The first contribution concerns validation of a model in logarithmic scale, that is, linear in the unknown nuisance parameters (emitted power and power loss constant). The parameter variation is studied over time and space. The second contribution is a localization algorithm based on this model, where the separable least squares principle is applied to the non-linear least squares (NLS) cost function, after which a cost function of only the unknown position is obtained. Results from field trials are presented to illustrate the method, together with fundamental performance bounds. The ambition is to pave the way for sensor configuration design and more thorough performance evaluations as well as filtering and target tracking aspects.

  • 249.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Fredrik
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Nordlund, Per-Johan
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology.
    Particle Filters for Positioning in Wireless Networks2002In: Proceedings of the 11th European Signal Processing Conference, 2002, p. 311-314 vol.24Conference paper (Refereed)
    Abstract [en]

    Positioning of road vehicles in wireless radio networks is a highly non-linear multi-sensor problem. The radio measurements deliver snapshot information of position as circle, radial and hyperbolic lines with various reliability, and possibly also complex power attenuation maps. Further, fading and absence of line of sight give complicated disturbances on these measurements. Temporal and spatial prior knowledge may include maximal velocity and acceleration of the mobile unit, and for automotive applications also the constraint that most of the time is spent on roads, which are stored in a digital map. We outline a framework where all this information can be incorporated, and the true a posteriori distribution of position can be approximated with arbitrary accuracy to be traded o with real-time requirements. The algorithm is based on the particle filter, and we demonstrate it on a few simulation examples.

  • 250.
    Gustafsson, Fredrik
    et al.
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Gunnarsson, Svante
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    Ljung, Lennart
    Linköping University, Department of Electrical Engineering, Automatic Control. Linköping University, The Institute of Technology.
    On Time-Frequency Resolution of Signal Properties using Parametric Techniques1995Report (Other academic)
    Abstract [en]

    The problem to track time-varying properties of a signal is studied. The somewhat contradictory notion of “time-varying spectrum” and how to estimate the “current” spectrum in an on-line fashion is discussed. The traditional concepts and relations between time- and frequency resolution are crucial for this problem. An adaptive estimation algorithm is used to estimate the parameters of a time-varying autoregressive model of the signal. It is shown how this algorithm can be equipped with a feature such that the time-frequency resolution trade-off favors quick detection of changes at higher frequencies and has slower adaptation at lower frequencies. This should be an attractive feature and similar to, for example, what wavelet transform techniques achieve for the same problem.

2345678 201 - 250 of 583
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