Valter Pasku

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 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.

A magnetic ranging aided dead-reckoning indoor positioning system for pedestrian applications

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

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.

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.

Analysis of Nonideal Effects and Performance in Magnetic Positioning Systems

The influence of the environmental configuration on ac magnetic distance and position measurement systems, which are based on inductive coupling of tuned resonators, is experimentally analyzed. The main aspects that affect the accuracy of 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 the maximum operating range and the error. Moreover, a strategy to detect if the measurement results are corrupted by the environmental configuration is presented. The analysis is then extended to a positioning scenario where the prototype of a magnetic positioning system (MPS) is deployed and a comparison with a commercial ultrawideband (UWB) system is performed. The results show that the MPS performance is comparable with the commercial UWB system, leading to a mean positioning error of the order of 0.6 m when using an extended Kalman filter-based positioning algorithm.

Tightly coupled integration of GPS and AC Magnetic Positioning Systems

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 a hardware section and a software section that can integrate with the MPS. Both system-level architecture and realization details are described along with experimental results. The realized 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 standalone GPS consumer receiver. Further, the system has been tested in two different scenarios, showing repeatable performance.

Effects of antenna directivity on a 2.5D positioning technique based on multiple RF transceivers

In this paper, a 2.5D positioning system is analyzed, based on Received Signal Strength (RSS) measurements, collected from narrowband RF transmissions. The mobile node of the considered system uses multiple closely spaced receivers, collecting RSS measurements and combining them to mitigate multipath effects. Using simulations and optical approximation, the effect of antenna directivity on the positioning accuracy is analyzed. Moreover, a simple iterative method is proposed, that further improves the accuracy obtained using the multipath mitigation technique.