Guido De Angelis

An Indoor AC Magnetic Positioning System

This paper describes the design and realization of a magnetic indoor positioning system. The system is entirely realized using off-the-shelf components and is based on inductive coupling between resonating coils. Both system-level architecture and realization details are described along with experimental results. The realized system exhibits a maximum positioning error of <;10 cm in an indoor environment over a 3 × 3 m2 area. Extensive experiments in larger areas, in nonline-of-sight conditions, and in unfavorable geometric configurations, show submeter accuracy, thus validating the robustness of the system with respect to other existing solutions.

A Simple Ranging System Based on Mutually Coupled Resonating Circuits

In this paper, a ranging technique based on inductive coupling between resonating coils is presented. By exploiting resonance, both a high range and high signal-to-noise ratio at the receiver are achieved. The theoretical background is discussed; a theoretical model is presented; and a practical implementation is illustrated and experimentally validated. It is shown that the proposed technique, implemented using off-the-shelf components, is only moderately sensitive to the effect of conductive objects placed close to the receiver, whereas it proves its effectiveness in an ordinary laboratory setup, achieving a maximum error of <;3 cm over a 5.8-m range. It is thus suitable for indoor positioning applications.

A Positioning System Based on Low-Frequency Magnetic Fields

This paper describes the design and the realization of a low-frequency ac magnetic-field-based indoor positioning system (PS). The system operation is based on the principle of inductive coupling between wire loop antennas. Specifically, due to the characteristics of the ac artificially generated magnetic fields, the relation between the induced voltage and the distance is modeled with a linear behavior in a bilogarithmic scale when a configuration with coplanar, thus equally oriented, antennas is used. In this case, the distance between a transmitting antenna and a receiving one is estimated using measurements of the induced voltage in the latter. For a high operational range, the system makes use of resonant antennas tuned at the same nominal resonant frequency. The quality factors act as antenna gain increasing the amplitude of the induced voltage. The low-operating frequency is the key factor for improving robustness against nonline-of-sight (NLOS) conditions and environment influences with respect to other existing solutions. The realized prototype, which is implemented using off-the-shelf components, exhibits an average and maximum positioning error, respectively, lower than 0.3 and 0.9 m in an indoor environment over a large area of 15 m × 12 m in NLOS conditions. Similar performance is obtained in an outdoor environment over an area of 30 m × 14 m. Furthermore, the system does not require any type of synchronization between the nodes and can accommodate an arbitrary number of users without additional infrastructure.

Positioning Techniques in Indoor Environments Based on Stochastic Modeling of UWB Round-Trip-Time Measurements

In this paper, a technique for modeling propagation of ultrawideband (UWB) signals in indoor or outdoor environments is proposed, supporting the design of a positioning systems based on round-trip-time (RTT) measurements and on a particle filter. By assuming that nonlinear pulses are transmitted in an additive white Gaussian noise channel and are detected using a threshold-based receiver, it is shown that RTT measurements may be affected by non-Gaussian noise. RTT noise properties are analyzed, and the effects of non-Gaussian noise on the performance of an RTT-based positioning system are investigated. To this aim, a classical least-squares estimator, an extended Kalman filter, and a particle filter are compared when used to detect a slowly moving target in the presence of the modeled noise. It is shown that, in a realistic indoor environment, the particle filter solution may be a competitive solution, at a price of increased computational complexity. Experimental verifications validate the presented approach.

Magnetic Field-Based Positioning Systems

This paper provides an introductory survey on the various systems that exploit magnetic fields for positioning. Such systems find applications in those scenarios, both indoors and outdoors, where global navigation satellite systems are not available or fail to provide information with the needed accuracy. While the main idea of using electromagnetic fields to provide position information dates back to the past century, new application-led research on this topic has emerged in recent years. Results have expanded the application range of magnetic positioning technologies and form now a domain of knowledge that enables realization of positioning systems applicable to indoor and outdoor environments. This paper provides the main characteristics of different positioning systems with focus on those solutions that are based on low-frequency magnetic fields. Some background theory is presented and positioning results from the literature are analyzed and compared.

Analysis of the sensitivity of AC magnetic ranging systems to environmental configurations

The influence of the environmental configuration on AC magnetic distance-measurement systems, which are based on inductive coupling of tuned resonators, is experimentally analyzed. The main aspects that affect accuracy in such systems are the conductivity of the terrain and the presence of metallic materials near the resonators. It is shown that such aspects are frequency-dependent, and a tradeoff is to be considered between maximum operating range and error. Moreover, a strategy to detect if measurement results are corrupted by environmental configuration is presented. This strategy is crucial to improve the integrity of positioning systems.

An accurate Indoor Position-measurement system using mutually coupled resonating circuits

This paper describes the design and realization of a Magnetic Indoor Positioning System. The system is entirely realized using off-the-shelf components and is based on inductive coupling between resonating coils. Both system-level architecture and realization details are described along with experimental results. The realized system exhibits a maximum positioning error of less than 10 cm in an indoor environment over a 3×3 m2 area.

Magnetic field analysis for distance measurement in 3D positioning applications

This paper proposes an analysis of the quasi-stationary magnetic field generated by coils and its applicability to 3D positioning applications. Starting from a theoretical background, an approximation of the induced voltage in a sensor coil is developed and analyzed. In particular, the introduced approximation error is shown to be lower than 5 mm over a 20 m range. Finally, the developed model is compared against a well-established theoretical model developed in the literature and against in-field measurements in the range 0.5 m to 5 m. Results show that the developed model may be suitable for magnetic field based distance measurements in low complexity 3D positioning applications.

An Experimental System for Tightly Coupled Integration of GPS and AC Magnetic Positioning

This paper describes the design and realization of a magnetic positioning system (MPS) integrated with a global positioning system (GPS) receiver. The GPS receiver is composed of hardware and software sections that can be integrated with the MPS. Both system-level architecture and realization details are described along with experimental results. The realized prototype measurement system exhibits a maximum positioning error of less than 5 m and an average error of less than 3 m, thus providing better performance than a stand-alone GPS consumer receiver. Further, the system is tested in two different scenarios, showing repeatable performance. A practical system implementation is presented, which can be employed in applications that require power-efficiency and low-cost operation. Such an implementation is tested experimentally, providing results that are comparable to those of the preliminary prototype, thus validating the proposed approach.

Parallel PN code acquisition for wireless positioning in CDMA handsets

This paper proposes a simplified acquisition system for finding and identifying Base Stations (BSs) in visibility in the framework of a CDMA wireless positioning system, based on IS-95 cellular standard. The problem of having more than one BS in the same PN code acquisition system makes it necessary to discriminate between correct detection and false alarm events. Since IS-95 uses the same PN sequence for all BSs, but with different code offsets, it is possible to use a cross-correlation technique to estimate both code and frequency offsets of several BSs at once. Time-Difference-Of-Arrival (TDOA) technique is used by the Mobile Station (MS) to geolocate itself. The positioning estimate is found to be stable in time and with a precision compatible with that required by emergency services, such as Enhanced 911 (E911).