ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position o... more ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position of a mobile device using terrestrial network-based radio communication systems are addressed in Chapter 3. The potential position-related information that can be extracted from a propagating signal is reviewed, namely: received signal strength (RSS), time of arrival (TOA), time difference of arrival (TDOA), and angle of arrival (AOA). Then the fundamental techniques to derive the position information from a collection of such measurements are explained, according to the classification in geometric techniques (either deterministic or statistical) and mapping (or fingerprinting) techniques. The most common sources of error affecting the above-mentioned processes are then analyzed. The chapter continues presenting the positioning approaches typically adopted in different network technologies (i.e., cellular networks, wireless LANs, and wireless sensor networks), addressing the underlying signal format, the most suitable kind of measurement, and the associated positioning and navigation algorithms. Particular attention is devoted to the ultrawideband technology, as the most promising signal format to implement high-performance terrestrial positioning.
This paper studies the possibility of upper bounding the position error of an estimate for range ... more This paper studies the possibility of upper bounding the position error of an estimate for range based positioning algorithms in wireless sensor networks. In this study, we argue that in certain situations when the measured distances between sensor nodes are positively biased, e.g., in non-line-of-sight conditions, the target node is confined to a closed bounded convex set (a feasible set) which can be derived from the measurements. Then, we formulate two classes of geometric upper bounds with respect to the feasible set. If an estimate is available, either feasible or infeasible, the worst-case position error can be defined as the maximum distance between the estimate and any point in the feasible set (the first bound).
The problem of positioning targets based on distance estimates is studied for cooperative wireles... more The problem of positioning targets based on distance estimates is studied for cooperative wireless sensor networks when there is limited a priori information about measurements noise. To solve this problem, two different methods of positioning are considered: statistical and geometrical. Based on a geometric interpretation, we show that the positioning problem can be rendered as finding the intersection of a number of convex sets. To find this intersection, we propose two different methods based on projection onto convex sets and outer-approximation. In the statistical approach, a partly novel two-step linear estimator is proposed which can be expressed in a closed-form solution. We also propose a new constrained non-linear least squares algorithm based on constraints derived in the outerapproximation approach. Simulation results show that the geometrical methods are more robust against non-line-of-sight measurements than the statistical approaches while in dense networks with lineof-sight measurements statistical approaches outperform geometrical methods.
The problem of positioning an unknown target is studied for a cooperative wireless sensor network... more The problem of positioning an unknown target is studied for a cooperative wireless sensor network using hybrid two-way time-of-arrival and time-difference-of-arrival measurements. A maximum likelihood estimator (MLE) can be employed to solve the problem. Due to the non-linear nature of the cost function in the MLE, a numerical method, e.g., an iterative search algorithm with a good initial point, should be taken to accurately estimate the target. To avoid drawbacks in a numerical method, we instead linearize the measurements and obtain a new two-step estimator that has a closed-form solution in each step. Simulation results confirm that the proposed linear estimator can attain Cramér-Rao lower bound for sufficiently high SNR.
ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position o... more ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position of a mobile device using terrestrial network-based radio communication systems are addressed in Chapter 3. The potential position-related information that can be extracted from a propagating signal is reviewed, namely: received signal strength (RSS), time of arrival (TOA), time difference of arrival (TDOA), and angle of arrival (AOA). Then the fundamental techniques to derive the position information from a collection of such measurements are explained, according to the classification in geometric techniques (either deterministic or statistical) and mapping (or fingerprinting) techniques. The most common sources of error affecting the above-mentioned processes are then analyzed. The chapter continues presenting the positioning approaches typically adopted in different network technologies (i.e., cellular networks, wireless LANs, and wireless sensor networks), addressing the underlying signal format, the most suitable kind of measurement, and the associated positioning and navigation algorithms. Particular attention is devoted to the ultrawideband technology, as the most promising signal format to implement high-performance terrestrial positioning.
EURASIP Journal on Advances in Signal Processing, 2006
We consider the problem of autonomously locating a number of asynchronous sensor nodes in a wirel... more We consider the problem of autonomously locating a number of asynchronous sensor nodes in a wireless network. A strong focus lies on reducing the processing resources needed to solve the relative positioning problem, an issue of great interest in resource-constrained wireless sensor networks. In the first part of the paper, based on a well-known derivation of the Cramér-Rao lower bound for the asynchronous sensor positioning problem, we are able to construct optimal preprocessing methods for sensor clock-offset cancellation. A cancellation of unknown clock-offsets from the asynchronous positioning problem reduces processing requirements, and, under certain reasonable assumptions, allows for statistically efficient distributed positioning algorithms.
Abstract: The present deliverable reports research results on seamless positioning techniques dev... more Abstract: The present deliverable reports research results on seamless positioning techniques developed in the framework of the work package WPR. B on Localization and Positioning within the NEWCOM++ NoE. These results address a wide range of cutting-edge topics starting from measurements, channel modeling, parameter estimation, cognitive and cooperative positioning techniques, and arriving to Bayesian methods for data fusion and integration of hybrid positioning systems (eg, GNSS/terrestrial, radio/inertial ...
Abstract: Accurate information on position of wireless users is crucial not only for emerging loc... more Abstract: Accurate information on position of wireless users is crucial not only for emerging location-based services and applications but also for network optimization. In order to develop accurate positioning algorithms, environmental characterization of basic radio propagation mechanisms carries significant importance. In the first part of this report, a measurement campaign performed within the NEWCOM++ WPR.
Abstract: Theoretical limits play a fundamental role in position estimation as guidelines and ben... more Abstract: Theoretical limits play a fundamental role in position estimation as guidelines and benchmarks of new developed algorithms. When designing practical positioning techniques the main focus is on reducing the gap between theoretical and real performance and keeping the complexity of the estimator at reasonable level. This report presents the results related to position estimation techniques obtained in the first eighteen months of activity of NEWCOM++ WPR. B. Most of the material represents the outcome of joint activities ...
ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position o... more ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position of a mobile device using terrestrial network-based radio communication systems are addressed in Chapter 3. The potential position-related information that can be extracted from a propagating signal is reviewed, namely: received signal strength (RSS), time of arrival (TOA), time difference of arrival (TDOA), and angle of arrival (AOA). Then the fundamental techniques to derive the position information from a collection of such measurements are explained, according to the classification in geometric techniques (either deterministic or statistical) and mapping (or fingerprinting) techniques. The most common sources of error affecting the above-mentioned processes are then analyzed. The chapter continues presenting the positioning approaches typically adopted in different network technologies (i.e., cellular networks, wireless LANs, and wireless sensor networks), addressing the underlying signal format, the most suitable kind of measurement, and the associated positioning and navigation algorithms. Particular attention is devoted to the ultrawideband technology, as the most promising signal format to implement high-performance terrestrial positioning.
This paper studies the possibility of upper bounding the position error of an estimate for range ... more This paper studies the possibility of upper bounding the position error of an estimate for range based positioning algorithms in wireless sensor networks. In this study, we argue that in certain situations when the measured distances between sensor nodes are positively biased, e.g., in non-line-of-sight conditions, the target node is confined to a closed bounded convex set (a feasible set) which can be derived from the measurements. Then, we formulate two classes of geometric upper bounds with respect to the feasible set. If an estimate is available, either feasible or infeasible, the worst-case position error can be defined as the maximum distance between the estimate and any point in the feasible set (the first bound).
The problem of positioning targets based on distance estimates is studied for cooperative wireles... more The problem of positioning targets based on distance estimates is studied for cooperative wireless sensor networks when there is limited a priori information about measurements noise. To solve this problem, two different methods of positioning are considered: statistical and geometrical. Based on a geometric interpretation, we show that the positioning problem can be rendered as finding the intersection of a number of convex sets. To find this intersection, we propose two different methods based on projection onto convex sets and outer-approximation. In the statistical approach, a partly novel two-step linear estimator is proposed which can be expressed in a closed-form solution. We also propose a new constrained non-linear least squares algorithm based on constraints derived in the outerapproximation approach. Simulation results show that the geometrical methods are more robust against non-line-of-sight measurements than the statistical approaches while in dense networks with lineof-sight measurements statistical approaches outperform geometrical methods.
The problem of positioning an unknown target is studied for a cooperative wireless sensor network... more The problem of positioning an unknown target is studied for a cooperative wireless sensor network using hybrid two-way time-of-arrival and time-difference-of-arrival measurements. A maximum likelihood estimator (MLE) can be employed to solve the problem. Due to the non-linear nature of the cost function in the MLE, a numerical method, e.g., an iterative search algorithm with a good initial point, should be taken to accurately estimate the target. To avoid drawbacks in a numerical method, we instead linearize the measurements and obtain a new two-step estimator that has a closed-form solution in each step. Simulation results confirm that the proposed linear estimator can attain Cramér-Rao lower bound for sufficiently high SNR.
ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position o... more ABSTRACT The fundamental technologies and signal-processing approaches to estimate the position of a mobile device using terrestrial network-based radio communication systems are addressed in Chapter 3. The potential position-related information that can be extracted from a propagating signal is reviewed, namely: received signal strength (RSS), time of arrival (TOA), time difference of arrival (TDOA), and angle of arrival (AOA). Then the fundamental techniques to derive the position information from a collection of such measurements are explained, according to the classification in geometric techniques (either deterministic or statistical) and mapping (or fingerprinting) techniques. The most common sources of error affecting the above-mentioned processes are then analyzed. The chapter continues presenting the positioning approaches typically adopted in different network technologies (i.e., cellular networks, wireless LANs, and wireless sensor networks), addressing the underlying signal format, the most suitable kind of measurement, and the associated positioning and navigation algorithms. Particular attention is devoted to the ultrawideband technology, as the most promising signal format to implement high-performance terrestrial positioning.
EURASIP Journal on Advances in Signal Processing, 2006
We consider the problem of autonomously locating a number of asynchronous sensor nodes in a wirel... more We consider the problem of autonomously locating a number of asynchronous sensor nodes in a wireless network. A strong focus lies on reducing the processing resources needed to solve the relative positioning problem, an issue of great interest in resource-constrained wireless sensor networks. In the first part of the paper, based on a well-known derivation of the Cramér-Rao lower bound for the asynchronous sensor positioning problem, we are able to construct optimal preprocessing methods for sensor clock-offset cancellation. A cancellation of unknown clock-offsets from the asynchronous positioning problem reduces processing requirements, and, under certain reasonable assumptions, allows for statistically efficient distributed positioning algorithms.
Abstract: The present deliverable reports research results on seamless positioning techniques dev... more Abstract: The present deliverable reports research results on seamless positioning techniques developed in the framework of the work package WPR. B on Localization and Positioning within the NEWCOM++ NoE. These results address a wide range of cutting-edge topics starting from measurements, channel modeling, parameter estimation, cognitive and cooperative positioning techniques, and arriving to Bayesian methods for data fusion and integration of hybrid positioning systems (eg, GNSS/terrestrial, radio/inertial ...
Abstract: Accurate information on position of wireless users is crucial not only for emerging loc... more Abstract: Accurate information on position of wireless users is crucial not only for emerging location-based services and applications but also for network optimization. In order to develop accurate positioning algorithms, environmental characterization of basic radio propagation mechanisms carries significant importance. In the first part of this report, a measurement campaign performed within the NEWCOM++ WPR.
Abstract: Theoretical limits play a fundamental role in position estimation as guidelines and ben... more Abstract: Theoretical limits play a fundamental role in position estimation as guidelines and benchmarks of new developed algorithms. When designing practical positioning techniques the main focus is on reducing the gap between theoretical and real performance and keeping the complexity of the estimator at reasonable level. This report presents the results related to position estimation techniques obtained in the first eighteen months of activity of NEWCOM++ WPR. B. Most of the material represents the outcome of joint activities ...
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Papers by M. Rydström