WiFi and Bluetooth are two most commonly used short range wireless communication technologies. Re... more WiFi and Bluetooth are two most commonly used short range wireless communication technologies. Recent years, with increasing number of WiFi and Bluetooth mobile terminals, tags, and other devices, a demand for integration and coexistence of these two technologies including their positioning function is booming. In this paper, we firstly investigate the interferences between WiFi and Bluetooth signals from the signal and protocol perspectives. Secondly, the principle of fingerprinting approach for WiFi positioning is introduced. In order to evaluate the performance of WiFi fingerprinting coexisted with Bluetooth, both occurrence-based and Weibull-based approaches are utilized for generating the database. Field tests present the interference in the WiFi and Bluetooth coexistence environments. A WiFi mobile device with a Bluetooth device nearby obtains poor positioning results due to the interference. Weibull-based database has more robust performance than occurrence-based database in the coexistence environments.
Space-based augmentation systems (SBAS), such as EGNOS, are largely used to complement GPS for ac... more Space-based augmentation systems (SBAS), such as EGNOS, are largely used to complement GPS for accurate and reliable positioning, which is required by rapidly growing location-based services (LBS). However, it is challenging to use EGNOS in the environments including urban areas and marginal area of the monitoring networks, where many LBS are delivered. Through the experiments in the challenging observation conditions, this study first evaluates the performance of EGNOS in these environments. Challenges consist in two aspects: EGNOS signals may be interrupted by blockages; EGNOS messages are not produced at all for marginal geographical areas due to the lack of raw satellite measurements. In order to use EGNOS for enhanced positioning performance in these environments, this paper then discusses several potential solutions. It is concluded that the two autonomous approaches, i.e. using aged corrections and mixing corrected and uncorrected satellites, can improve the positioning accuracy with a stand-alone receiver, and a full EGNOS positioning performance can be achieved in urban areas via a terrestrial access to EGNOS data, for example, the Internet connection with a smartphone. This paper discusses the effectiveness and usability of these approaches.
2014 Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS), 2014
Nowadays smartphones are equipped with various sensors and powerful processing modules, and are a... more Nowadays smartphones are equipped with various sensors and powerful processing modules, and are accessible to flexible communication networks, thus enabling complex applications such as context awareness, activity recognition, health care monitoring and so forth. These applications typically require contextual information to optimize the effectiveness, e.g. indoor/outdoor identification. This paper develops an indoor/outdoor detection method based on a generic smartphone platform, utilizing the information extracted from the internal clock, GPS module and light intensity sensor. The vote principle is used in the detection. The approach has been tested in multiple locations in order to evaluate performance. This includes residences, office space, roads, restaurants, markets and so forth. Two kinds of detection results consisting of static and walking scenarios are shown in the paper. This method can output detection results with good accuracy in both day and night and all weather conditions. The approach can operate on different smartphone profiles from low-end to high-end. An optimized method also presents for some advanced smartphones with GPS satellite signal noise ratio output, which has been shown more effective in real-time response and detection accuracy.
2014 Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS), 2014
This paper introduces a framework of contextual thinking in mobile devices. It is based on real-t... more This paper introduces a framework of contextual thinking in mobile devices. It is based on real-time sensing of local time, significant locations, location-dwelling states, and user states to infer significant activities. A significant activity is a well-defined activity to be inferred, for example, waiting for a bus, having a meeting, working in office, taking a break in a coffee shop et al. A significant location is defined as a geofence, which can be a node associated with a circle, or a polygon. A location-dwelling state is defined as enter into a significant location, the location-dwelling duration, or exit from a significant location. A user state is a combination of user mobility states, user actions, user social states and event psychological states. With this initial study, we just focus on the user motion states including static, slow walking, walking and fast moving that can be fast walking or driving. However, the framework and the activity inference algorithm are flexible for adopting other user states in the future. Using the measurements of the built-in sensors and radio signals in mobile devices, we can capture a snapshot of a contextual tuple for every second, which includes a time tag, an ID of a significant location, a location-dwelling duration, and a user state. The sequence of contextual tuples is used as the inputs for inferring the user significant activities. The contextual thinking engine will evaluate the posteriori probability of each significant activity for each given contextual tuple using a Bayesian approach. An "un-defined" activity is adopted to cover all activities other than the selected significant activities. A prototype of the contextual thinking engine has been developed in the Geospatial Computing Lab at Texas A&M University Corpus Christi. A test environment was setup on the campus. Six significant activities were defined and tested by two different testers for three days using two different smartphones. These significant activities include: 1) working in an office; 2) having a meeting; 3) having a lunch, 4) having a coffee break, 5) visiting the library, and 6) waiting for a bus. An "un-defined" activity was included to cover all activities other than the selected significant activities. The inferred activities were then compared with the labeled activities to assess the performance of the contextual thinking engine. We demonstrated that the success rate of inference was more than 90% on average. We recognized that the positioning accuracy plays a significant role in the inference algorithm because it has direct impact to two elements in the contextual tuple: the significant location and the location-dwelling duration.
ABSTRACT Satellite-based positioning is undergoing a rapid change. There is a need to reform the ... more ABSTRACT Satellite-based positioning is undergoing a rapid change. There is a need to reform the U.S. GPS and Russian GLONASS systems due to the increasing number of applications that utilize positioning, more demanding requirements from users and the need to mitigate interferences and disturbances to the radio signals used by these systems. Both the GPS and the GLONASS systems are being modernized to serve better the current challenging applications in harsh signal conditions. These modernizations include increasing the number of transmission frequencies and changes to the signal components. In addition, the European Galileo and the Chinese BeiDou systems are currently under development for global operation. There is a strong intention to design the forthcoming: to make the modernized systems to be resistant to interference as well as make them more accurate and available over a wider range of conditions. Also, the use of multiple systems for positioning increases the accuracy and reliability even further. Europe’s own satellite navigation system Galileo is designed for civilian use and has been under development for almost a decade. Two test satellites (GIOVE-A, GIOVE-B) have already been in orbital operation since 2005 and 2008, respectively, and in October 2012 the latest Galileo launch secured 4 actual in-orbit validation (IOV) satellites to be successfully transmitting signals from their planned orbits. The amount of 4 IOV satellites is already sufficient to determine the position, time and speed of a Galileo receiver in real-time. The fully deployed Galileo system will consists of 30 satellites positioned in three circular Medium Earth Orbit (MEO) planes at around 23000 km altitude above the Earth’s mean sea level with an inclination angle of 56 degrees with respect to the equator. The system is expected to be operational by the year 2020. Galileo will provide EU countries an independent navigation system that has better positioning accuracy and reliability compared to the current satellite systems of the US (GPS) and Russia (GLONASS). Galileo satellites will transmit signals on the same frequencies as GPS, but modulated with different code techniques. The Chinese satellite navigation system BeiDou has a mixed space constellation that has, when fully deployed, five Geostationary Earth Orbit (GEO) satellites, twenty-seven MEO satellites and three Inclined Geosynchronous Satellite Orbit (IGSO) satellites. The GEO satellites are operating in orbit at an altitude of 35786 kilometers and positioned at 58.75°E, 80°E, 110.5°E, 140°E and 160°E respectively. The MEO satellites are operating in orbit at an altitude of 21528 kilometers and an inclination of 55° to the equatorial plane. The IGSO satellites are operating in orbit at an altitude of 35786 kilometers and an inclination of 55° to the equatorial plane. These satellites broadcast navigation signals and messages within 3 frequency bands. The BeiDou system has been in development for more than a decade, and it is estimated to be operational with global coverage at the latest in 2020. The BeiDou satellites transmit ranging signals based on the CDMA (code division multiple access) principle, like GPS and Galileo. The mixed constellation structure of BeiDou results in better observation geometry for positioning and orbit determination compared to current GPS and GLONASS, and future Galileo, especially in China and neighboring regions. The BeiDou system contributes to the multi-GNSS benefits where increased accuracy, availability and integrity are possible when utilizing interoperable GNSS (Global Navigation Satellite Systems). Researchers at the Finnish Geodetic Institute are following signals from all four IOV-satellites of the Galileo-system as well as the visible BeiDou satellites with their software-defined satellite navigation receiver FGI-GSRx which has been developed for research purposes. So far the platform has been used to verify that the Galileo satellites are sending accurate signals as defined in the Galileo system specifications and also to acquire and track BeiDou satellites. The software receiver is a unique platform in Finland for analyzing Galileo and BeiDou signals. Better positioning methods utilizing Galileo and BeiDou signals can be developed, especially for challenging environments such as urban spaces or high-dynamics space applications. We will present initial results on Galileo and BeiDou signal acquisition and tracking with the developed FGI-GSRx software receiver platform.
Ubiquitous Positioning and Mobile Location-Based Services in Smart Phones
Although the short range radio frequency technologies such as WLAN (Wireless Local Area Network) ... more Although the short range radio frequency technologies such as WLAN (Wireless Local Area Network) and Bluetooth were originally designed for the purpose of wireless communication, they have been widely adopted as common signals of opportunity for positioning in smart phones for both indoors and outdoors. The cell identifier and radio signal strength are the most common observables used for positioning. The applicable position methods include Cell-ID, fingerprinting, and trilateration. Fingerprinting is the most common approach, which can provide a positioning accuracy of even 2-5 meters indoors using either the pattern recognition algorithm or the probabilistic algorithm; however, the obtainable accuracy depends on the positioning environment. The objective of this chapter is to present the WLAN and Bluetooth positioning methodologies and explain the related positioning algorithms. The chapter covers an introduction of the topic, descriptions of the observables, the positioning algor...
Advancing Embedded Systems and Real-Time Communications with Emerging Technologies
This chapter studies wireless positioning using a network of Bluetooth signals. Fingerprints of R... more This chapter studies wireless positioning using a network of Bluetooth signals. Fingerprints of Received Signal Strength Indicators (RSSI) are used for localization. Due to the relatively long interval between the available consecutive Bluetooth signal strength measurements, the authors applied an information filter method with speed detection, which combines the estimation information from the RSSI measurements with the prior information from the motion model. Speed detection is assisted to correct the outliers of position estimation. The field tests show the effectiveness of the information filter-assisted positioning method, which improves the horizontal positioning accuracy of indoor navigation by about 17% compared to the static fingerprinting positioning method, achieving a 4.2 m positioning accuracy on the average, and about 16% improvement compared to the point Kalman filter. In RSSI fingerprinting localization, building a fingerprint database is usually time-consuming and labour-intensive. In the final section, a self-designed autonomous SLAM robot platform is introduced to be able to carry out the Bluetooth RSS data collecting.
International Conference on Indoor Positioning and Indoor Navigation, 2013
ABSTRACT Microphone arrays, also known as acoustic antennas, have been extensively used for sound... more ABSTRACT Microphone arrays, also known as acoustic antennas, have been extensively used for sound localization. Small-scale microphone arrays have especially been used in teleconferences and game consoles due to their small dimension and easy deployment. In this article, we present an approach to locating a sound source using a small linear microphone array. We describe the fundamentals of linear microphone arrays and analyze the impact of geometry in terms of positioning accuracy using the dilution of precision (DOP) concept. The generalized cross-correlation (GCC) based on the phase transform (PHAT) weighting function is used to estimate the time difference of arrivals in a microphone array. Given the time differences, we use both closed-form and iterative optimization solutions to calculate the coordinates of the sound source. In order to evaluate the performances of the solutions applied in this paper, simulations and field tests were conducted. Simulation results show that the closed-form algorithm gives a positioning error of less than 5 cm in a 10-by-10 meter room when the geometry of a microphone array is good and the signal to noise ratio (SNR) is high. Linear small microphone arrays have lower performances compared to a non-linear distributed array. When the scale of a linear array is reduced, the positioning accuracy decreases dramatically. With a small linear array, the iterative optimization algorithm gives much better performance compared to the closed-form algorithm. Field tests were conducted in an 11-by-5.6 meter room using a linear array with a length of 0.23 meters. Positioning results show an average error of 0.25 meters along the axis parallel to the linear array and 0.53 meters error along the axis which is perpendicular to the linear array.
2012 Ubiquitous Positioning, Indoor Navigation, and Location Based Service (UPINLBS), 2012
Abstract An increasing number of WiFi and Bluetooth terminals, tags, and other mobile devices dri... more Abstract An increasing number of WiFi and Bluetooth terminals, tags, and other mobile devices drives a growing demand for integration and coexistence of these two technologies. This paper gives the preliminary results of WiFi positioning in a WiFi and Bluetooth coexistence environment. The received signal strength indication is introduced as an observation applied to our WiFi positioning. Then, we present the basis of a fingerprinting approach to WiFi positioning and analyze the characters and protocols of WiFi and ...
ABSTRACT The conventional ionosphere total electron content (TEC) models based on geodetic coordi... more ABSTRACT The conventional ionosphere total electron content (TEC) models based on geodetic coordinates have asynchronous dimensional resolution, especially in the area close to the pole. This paper presents a novel spherical cap harmonic model for mapping the arctic regional ionospheric TEC in a spherical cap coordinate system. Utilizing a series of IGS (International GNSS Service) products, a set of dual-frequency GPS (Global Positioning System) data from IGS stations in high latitudes is processed and used to map the arctic regional TEC values with the spherical cap harmonic model and the conventional regional TEC models. Together with the global ionosphere mapping (GIM) model from IGS, the TEC mapping accuracies from these models are compared. The comparison results show that the spherical cap harmonic model has a better TEC mapping performance with more homogeneous accuracy distributions in both temporal and spatial domains for the arctic region. In addition, the spectrum components of the coefficient series of the spherical cap harmonic models are demonstrated in this paper.
The paper presents an indoor navigation solution by combining physical motion recognition with wi... more The paper presents an indoor navigation solution by combining physical motion recognition with wireless positioning. Twenty-seven simple features are extracted from the built-in accelerometers and magnetometers in a smartphone. Eight common motion states used during indoor navigation are detected by a Least Square-Support Vector Machines (LS-SVM) classification algorithm, e.g., static, standing with hand swinging, normal walking while holding the phone in hand, normal walking with hand swinging, fast walking, U-turning, going up stairs, and going down stairs. The results indicate that the motion states are recognized with an accuracy of up to 95.53% for the test cases employed in this study. A motion recognition assisted wireless positioning approach is applied to determine the position of a mobile user. Field tests show a 1.22 m mean error in -Static Tests‖ and a 3.53 m in -Stop-Go Tests‖.
This research focuses on sensing context, modeling human behavior and developing a new architectu... more This research focuses on sensing context, modeling human behavior and developing a new architecture for a cognitive phone platform. We combine the latest positioning technologies and phone sensors to capture human movements in natural environments and use the movements to study human behavior. Contexts in this research are abstracted as a Context Pyramid which includes six levels: Raw Sensor Data, Physical Parameter, Features/Patterns, Simple Contextual Descriptors, Activity-Level Descriptors, and Rich Context. To achieve implementation of the Context Pyramid on a cognitive phone, three key technologies are utilized: ubiquitous positioning, motion recognition, and human behavior modeling. Preliminary tests indicate that we have successfully achieved the Activity-Level Descriptors level with our LoMoCo (Location-Motion-Context) model. Location accuracy of the proposed solution is up to 1.9 meters in corridor environments and 3.5 meters in open spaces. Test results also indicate that the motion states are recognized with an accuracy rate up to 92.9% using a Least Square-Support Vector Machine (LS-SVM) classifier.
This study discusses a simple multi-sensor multi-network positioning system that integrates globa... more This study discusses a simple multi-sensor multi-network positioning system that integrates global positioning satellite (GPS) measurements, accelerometers and a digital compass with wireless network localisation utilising a pedestrian motion model and dead reckoning. The feasibility of the multi-technology system for seamless outdoor to indoor pedestrian navigation is discussed with the emphasis on reliability issues and adaptability requirements. The multi-sensor multi-network positioning system is developed for challenging navigation environments such as indoors and deep urban canyons. This study considers how to estimate and improve such a multi-sensor multi-network system's reliability and estimate its accuracy. An outdoor to indoor pedestrian test is conducted. Adaptive filtering performance of the multi-technology solution as well as general measurement quality monitoring and error detection when an over-determined solution is at hand is shown. Reliability estimation utilising adaptation in the form of environment detection to estimate the final positioning accuracy is also presented.
Human activities in high latitudes and the arctic region are nowadays more and more popular, eg r... more Human activities in high latitudes and the arctic region are nowadays more and more popular, eg resource utilization, research, airlines over the arctic, and exploration in the arctic region, etc. Therefore, accurate GNSS positioning and navigation in high latitudes and the arctic region is required for these applications.
The present invention provides GPS receivers with clock calibration for fast reacquisition of GPS... more The present invention provides GPS receivers with clock calibration for fast reacquisition of GPS signals after waking up from a sleep state or coming out of signal blockage. In a preferred embodiment, a GPS receiver comprises a local clock based on an oscillator, eg, crystal oscillator. The GPS receiver calculates a clock calibration value based on a computed oscillator count for the period during which the GPS receiver is in the sleep state or the signal is blocked. This clock calibration value is used to calibrate the local clock ...
Based on spherical cap harmonic analysis(SCHA) methodology,the SCHA model to fit regional ionosph... more Based on spherical cap harmonic analysis(SCHA) methodology,the SCHA model to fit regional ionosphere total electronic content(TEC) over China is developed,and the accuracy and validity of this new TEC model by the GPS measurements from two Chinese domestic GPS observation networks in 2004 are evaluated.The results show that SCHA model is preferable since the overall modeling residual with respect to TEC measurements is relatively small,and the residual distribution is well-proportioned within temporal and spatial domain.Moreover,the time series of SCHA coefficients reflect the procecss of ionospheric activity explicitly,e.g.,the coefficient 0,0 depicts the mean regional ionosphere TEC,which is confirmed by the result deduced by GIM parameters of CODE,one of IGS analysis centers.That implies that SCHA mode can be used to predicate regional ionospheric TEC.Due to more GPS measurements over China involved in the modeling,SCHA model provides more precise TEC estimation in the region than IONEX data delivered by IGS analysis centers.
WiFi and Bluetooth are two most commonly used short range wireless communication technologies. Re... more WiFi and Bluetooth are two most commonly used short range wireless communication technologies. Recent years, with increasing number of WiFi and Bluetooth mobile terminals, tags, and other devices, a demand for integration and coexistence of these two technologies including their positioning function is booming. In this paper, we firstly investigate the interferences between WiFi and Bluetooth signals from the signal and protocol perspectives. Secondly, the principle of fingerprinting approach for WiFi positioning is introduced. In order to evaluate the performance of WiFi fingerprinting coexisted with Bluetooth, both occurrence-based and Weibull-based approaches are utilized for generating the database. Field tests present the interference in the WiFi and Bluetooth coexistence environments. A WiFi mobile device with a Bluetooth device nearby obtains poor positioning results due to the interference. Weibull-based database has more robust performance than occurrence-based database in the coexistence environments.
Space-based augmentation systems (SBAS), such as EGNOS, are largely used to complement GPS for ac... more Space-based augmentation systems (SBAS), such as EGNOS, are largely used to complement GPS for accurate and reliable positioning, which is required by rapidly growing location-based services (LBS). However, it is challenging to use EGNOS in the environments including urban areas and marginal area of the monitoring networks, where many LBS are delivered. Through the experiments in the challenging observation conditions, this study first evaluates the performance of EGNOS in these environments. Challenges consist in two aspects: EGNOS signals may be interrupted by blockages; EGNOS messages are not produced at all for marginal geographical areas due to the lack of raw satellite measurements. In order to use EGNOS for enhanced positioning performance in these environments, this paper then discusses several potential solutions. It is concluded that the two autonomous approaches, i.e. using aged corrections and mixing corrected and uncorrected satellites, can improve the positioning accuracy with a stand-alone receiver, and a full EGNOS positioning performance can be achieved in urban areas via a terrestrial access to EGNOS data, for example, the Internet connection with a smartphone. This paper discusses the effectiveness and usability of these approaches.
2014 Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS), 2014
Nowadays smartphones are equipped with various sensors and powerful processing modules, and are a... more Nowadays smartphones are equipped with various sensors and powerful processing modules, and are accessible to flexible communication networks, thus enabling complex applications such as context awareness, activity recognition, health care monitoring and so forth. These applications typically require contextual information to optimize the effectiveness, e.g. indoor/outdoor identification. This paper develops an indoor/outdoor detection method based on a generic smartphone platform, utilizing the information extracted from the internal clock, GPS module and light intensity sensor. The vote principle is used in the detection. The approach has been tested in multiple locations in order to evaluate performance. This includes residences, office space, roads, restaurants, markets and so forth. Two kinds of detection results consisting of static and walking scenarios are shown in the paper. This method can output detection results with good accuracy in both day and night and all weather conditions. The approach can operate on different smartphone profiles from low-end to high-end. An optimized method also presents for some advanced smartphones with GPS satellite signal noise ratio output, which has been shown more effective in real-time response and detection accuracy.
2014 Ubiquitous Positioning Indoor Navigation and Location Based Service (UPINLBS), 2014
This paper introduces a framework of contextual thinking in mobile devices. It is based on real-t... more This paper introduces a framework of contextual thinking in mobile devices. It is based on real-time sensing of local time, significant locations, location-dwelling states, and user states to infer significant activities. A significant activity is a well-defined activity to be inferred, for example, waiting for a bus, having a meeting, working in office, taking a break in a coffee shop et al. A significant location is defined as a geofence, which can be a node associated with a circle, or a polygon. A location-dwelling state is defined as enter into a significant location, the location-dwelling duration, or exit from a significant location. A user state is a combination of user mobility states, user actions, user social states and event psychological states. With this initial study, we just focus on the user motion states including static, slow walking, walking and fast moving that can be fast walking or driving. However, the framework and the activity inference algorithm are flexible for adopting other user states in the future. Using the measurements of the built-in sensors and radio signals in mobile devices, we can capture a snapshot of a contextual tuple for every second, which includes a time tag, an ID of a significant location, a location-dwelling duration, and a user state. The sequence of contextual tuples is used as the inputs for inferring the user significant activities. The contextual thinking engine will evaluate the posteriori probability of each significant activity for each given contextual tuple using a Bayesian approach. An "un-defined" activity is adopted to cover all activities other than the selected significant activities. A prototype of the contextual thinking engine has been developed in the Geospatial Computing Lab at Texas A&M University Corpus Christi. A test environment was setup on the campus. Six significant activities were defined and tested by two different testers for three days using two different smartphones. These significant activities include: 1) working in an office; 2) having a meeting; 3) having a lunch, 4) having a coffee break, 5) visiting the library, and 6) waiting for a bus. An "un-defined" activity was included to cover all activities other than the selected significant activities. The inferred activities were then compared with the labeled activities to assess the performance of the contextual thinking engine. We demonstrated that the success rate of inference was more than 90% on average. We recognized that the positioning accuracy plays a significant role in the inference algorithm because it has direct impact to two elements in the contextual tuple: the significant location and the location-dwelling duration.
ABSTRACT Satellite-based positioning is undergoing a rapid change. There is a need to reform the ... more ABSTRACT Satellite-based positioning is undergoing a rapid change. There is a need to reform the U.S. GPS and Russian GLONASS systems due to the increasing number of applications that utilize positioning, more demanding requirements from users and the need to mitigate interferences and disturbances to the radio signals used by these systems. Both the GPS and the GLONASS systems are being modernized to serve better the current challenging applications in harsh signal conditions. These modernizations include increasing the number of transmission frequencies and changes to the signal components. In addition, the European Galileo and the Chinese BeiDou systems are currently under development for global operation. There is a strong intention to design the forthcoming: to make the modernized systems to be resistant to interference as well as make them more accurate and available over a wider range of conditions. Also, the use of multiple systems for positioning increases the accuracy and reliability even further. Europe’s own satellite navigation system Galileo is designed for civilian use and has been under development for almost a decade. Two test satellites (GIOVE-A, GIOVE-B) have already been in orbital operation since 2005 and 2008, respectively, and in October 2012 the latest Galileo launch secured 4 actual in-orbit validation (IOV) satellites to be successfully transmitting signals from their planned orbits. The amount of 4 IOV satellites is already sufficient to determine the position, time and speed of a Galileo receiver in real-time. The fully deployed Galileo system will consists of 30 satellites positioned in three circular Medium Earth Orbit (MEO) planes at around 23000 km altitude above the Earth’s mean sea level with an inclination angle of 56 degrees with respect to the equator. The system is expected to be operational by the year 2020. Galileo will provide EU countries an independent navigation system that has better positioning accuracy and reliability compared to the current satellite systems of the US (GPS) and Russia (GLONASS). Galileo satellites will transmit signals on the same frequencies as GPS, but modulated with different code techniques. The Chinese satellite navigation system BeiDou has a mixed space constellation that has, when fully deployed, five Geostationary Earth Orbit (GEO) satellites, twenty-seven MEO satellites and three Inclined Geosynchronous Satellite Orbit (IGSO) satellites. The GEO satellites are operating in orbit at an altitude of 35786 kilometers and positioned at 58.75°E, 80°E, 110.5°E, 140°E and 160°E respectively. The MEO satellites are operating in orbit at an altitude of 21528 kilometers and an inclination of 55° to the equatorial plane. The IGSO satellites are operating in orbit at an altitude of 35786 kilometers and an inclination of 55° to the equatorial plane. These satellites broadcast navigation signals and messages within 3 frequency bands. The BeiDou system has been in development for more than a decade, and it is estimated to be operational with global coverage at the latest in 2020. The BeiDou satellites transmit ranging signals based on the CDMA (code division multiple access) principle, like GPS and Galileo. The mixed constellation structure of BeiDou results in better observation geometry for positioning and orbit determination compared to current GPS and GLONASS, and future Galileo, especially in China and neighboring regions. The BeiDou system contributes to the multi-GNSS benefits where increased accuracy, availability and integrity are possible when utilizing interoperable GNSS (Global Navigation Satellite Systems). Researchers at the Finnish Geodetic Institute are following signals from all four IOV-satellites of the Galileo-system as well as the visible BeiDou satellites with their software-defined satellite navigation receiver FGI-GSRx which has been developed for research purposes. So far the platform has been used to verify that the Galileo satellites are sending accurate signals as defined in the Galileo system specifications and also to acquire and track BeiDou satellites. The software receiver is a unique platform in Finland for analyzing Galileo and BeiDou signals. Better positioning methods utilizing Galileo and BeiDou signals can be developed, especially for challenging environments such as urban spaces or high-dynamics space applications. We will present initial results on Galileo and BeiDou signal acquisition and tracking with the developed FGI-GSRx software receiver platform.
Ubiquitous Positioning and Mobile Location-Based Services in Smart Phones
Although the short range radio frequency technologies such as WLAN (Wireless Local Area Network) ... more Although the short range radio frequency technologies such as WLAN (Wireless Local Area Network) and Bluetooth were originally designed for the purpose of wireless communication, they have been widely adopted as common signals of opportunity for positioning in smart phones for both indoors and outdoors. The cell identifier and radio signal strength are the most common observables used for positioning. The applicable position methods include Cell-ID, fingerprinting, and trilateration. Fingerprinting is the most common approach, which can provide a positioning accuracy of even 2-5 meters indoors using either the pattern recognition algorithm or the probabilistic algorithm; however, the obtainable accuracy depends on the positioning environment. The objective of this chapter is to present the WLAN and Bluetooth positioning methodologies and explain the related positioning algorithms. The chapter covers an introduction of the topic, descriptions of the observables, the positioning algor...
Advancing Embedded Systems and Real-Time Communications with Emerging Technologies
This chapter studies wireless positioning using a network of Bluetooth signals. Fingerprints of R... more This chapter studies wireless positioning using a network of Bluetooth signals. Fingerprints of Received Signal Strength Indicators (RSSI) are used for localization. Due to the relatively long interval between the available consecutive Bluetooth signal strength measurements, the authors applied an information filter method with speed detection, which combines the estimation information from the RSSI measurements with the prior information from the motion model. Speed detection is assisted to correct the outliers of position estimation. The field tests show the effectiveness of the information filter-assisted positioning method, which improves the horizontal positioning accuracy of indoor navigation by about 17% compared to the static fingerprinting positioning method, achieving a 4.2 m positioning accuracy on the average, and about 16% improvement compared to the point Kalman filter. In RSSI fingerprinting localization, building a fingerprint database is usually time-consuming and labour-intensive. In the final section, a self-designed autonomous SLAM robot platform is introduced to be able to carry out the Bluetooth RSS data collecting.
International Conference on Indoor Positioning and Indoor Navigation, 2013
ABSTRACT Microphone arrays, also known as acoustic antennas, have been extensively used for sound... more ABSTRACT Microphone arrays, also known as acoustic antennas, have been extensively used for sound localization. Small-scale microphone arrays have especially been used in teleconferences and game consoles due to their small dimension and easy deployment. In this article, we present an approach to locating a sound source using a small linear microphone array. We describe the fundamentals of linear microphone arrays and analyze the impact of geometry in terms of positioning accuracy using the dilution of precision (DOP) concept. The generalized cross-correlation (GCC) based on the phase transform (PHAT) weighting function is used to estimate the time difference of arrivals in a microphone array. Given the time differences, we use both closed-form and iterative optimization solutions to calculate the coordinates of the sound source. In order to evaluate the performances of the solutions applied in this paper, simulations and field tests were conducted. Simulation results show that the closed-form algorithm gives a positioning error of less than 5 cm in a 10-by-10 meter room when the geometry of a microphone array is good and the signal to noise ratio (SNR) is high. Linear small microphone arrays have lower performances compared to a non-linear distributed array. When the scale of a linear array is reduced, the positioning accuracy decreases dramatically. With a small linear array, the iterative optimization algorithm gives much better performance compared to the closed-form algorithm. Field tests were conducted in an 11-by-5.6 meter room using a linear array with a length of 0.23 meters. Positioning results show an average error of 0.25 meters along the axis parallel to the linear array and 0.53 meters error along the axis which is perpendicular to the linear array.
2012 Ubiquitous Positioning, Indoor Navigation, and Location Based Service (UPINLBS), 2012
Abstract An increasing number of WiFi and Bluetooth terminals, tags, and other mobile devices dri... more Abstract An increasing number of WiFi and Bluetooth terminals, tags, and other mobile devices drives a growing demand for integration and coexistence of these two technologies. This paper gives the preliminary results of WiFi positioning in a WiFi and Bluetooth coexistence environment. The received signal strength indication is introduced as an observation applied to our WiFi positioning. Then, we present the basis of a fingerprinting approach to WiFi positioning and analyze the characters and protocols of WiFi and ...
ABSTRACT The conventional ionosphere total electron content (TEC) models based on geodetic coordi... more ABSTRACT The conventional ionosphere total electron content (TEC) models based on geodetic coordinates have asynchronous dimensional resolution, especially in the area close to the pole. This paper presents a novel spherical cap harmonic model for mapping the arctic regional ionospheric TEC in a spherical cap coordinate system. Utilizing a series of IGS (International GNSS Service) products, a set of dual-frequency GPS (Global Positioning System) data from IGS stations in high latitudes is processed and used to map the arctic regional TEC values with the spherical cap harmonic model and the conventional regional TEC models. Together with the global ionosphere mapping (GIM) model from IGS, the TEC mapping accuracies from these models are compared. The comparison results show that the spherical cap harmonic model has a better TEC mapping performance with more homogeneous accuracy distributions in both temporal and spatial domains for the arctic region. In addition, the spectrum components of the coefficient series of the spherical cap harmonic models are demonstrated in this paper.
The paper presents an indoor navigation solution by combining physical motion recognition with wi... more The paper presents an indoor navigation solution by combining physical motion recognition with wireless positioning. Twenty-seven simple features are extracted from the built-in accelerometers and magnetometers in a smartphone. Eight common motion states used during indoor navigation are detected by a Least Square-Support Vector Machines (LS-SVM) classification algorithm, e.g., static, standing with hand swinging, normal walking while holding the phone in hand, normal walking with hand swinging, fast walking, U-turning, going up stairs, and going down stairs. The results indicate that the motion states are recognized with an accuracy of up to 95.53% for the test cases employed in this study. A motion recognition assisted wireless positioning approach is applied to determine the position of a mobile user. Field tests show a 1.22 m mean error in -Static Tests‖ and a 3.53 m in -Stop-Go Tests‖.
This research focuses on sensing context, modeling human behavior and developing a new architectu... more This research focuses on sensing context, modeling human behavior and developing a new architecture for a cognitive phone platform. We combine the latest positioning technologies and phone sensors to capture human movements in natural environments and use the movements to study human behavior. Contexts in this research are abstracted as a Context Pyramid which includes six levels: Raw Sensor Data, Physical Parameter, Features/Patterns, Simple Contextual Descriptors, Activity-Level Descriptors, and Rich Context. To achieve implementation of the Context Pyramid on a cognitive phone, three key technologies are utilized: ubiquitous positioning, motion recognition, and human behavior modeling. Preliminary tests indicate that we have successfully achieved the Activity-Level Descriptors level with our LoMoCo (Location-Motion-Context) model. Location accuracy of the proposed solution is up to 1.9 meters in corridor environments and 3.5 meters in open spaces. Test results also indicate that the motion states are recognized with an accuracy rate up to 92.9% using a Least Square-Support Vector Machine (LS-SVM) classifier.
This study discusses a simple multi-sensor multi-network positioning system that integrates globa... more This study discusses a simple multi-sensor multi-network positioning system that integrates global positioning satellite (GPS) measurements, accelerometers and a digital compass with wireless network localisation utilising a pedestrian motion model and dead reckoning. The feasibility of the multi-technology system for seamless outdoor to indoor pedestrian navigation is discussed with the emphasis on reliability issues and adaptability requirements. The multi-sensor multi-network positioning system is developed for challenging navigation environments such as indoors and deep urban canyons. This study considers how to estimate and improve such a multi-sensor multi-network system's reliability and estimate its accuracy. An outdoor to indoor pedestrian test is conducted. Adaptive filtering performance of the multi-technology solution as well as general measurement quality monitoring and error detection when an over-determined solution is at hand is shown. Reliability estimation utilising adaptation in the form of environment detection to estimate the final positioning accuracy is also presented.
Human activities in high latitudes and the arctic region are nowadays more and more popular, eg r... more Human activities in high latitudes and the arctic region are nowadays more and more popular, eg resource utilization, research, airlines over the arctic, and exploration in the arctic region, etc. Therefore, accurate GNSS positioning and navigation in high latitudes and the arctic region is required for these applications.
The present invention provides GPS receivers with clock calibration for fast reacquisition of GPS... more The present invention provides GPS receivers with clock calibration for fast reacquisition of GPS signals after waking up from a sleep state or coming out of signal blockage. In a preferred embodiment, a GPS receiver comprises a local clock based on an oscillator, eg, crystal oscillator. The GPS receiver calculates a clock calibration value based on a computed oscillator count for the period during which the GPS receiver is in the sleep state or the signal is blocked. This clock calibration value is used to calibrate the local clock ...
Based on spherical cap harmonic analysis(SCHA) methodology,the SCHA model to fit regional ionosph... more Based on spherical cap harmonic analysis(SCHA) methodology,the SCHA model to fit regional ionosphere total electronic content(TEC) over China is developed,and the accuracy and validity of this new TEC model by the GPS measurements from two Chinese domestic GPS observation networks in 2004 are evaluated.The results show that SCHA model is preferable since the overall modeling residual with respect to TEC measurements is relatively small,and the residual distribution is well-proportioned within temporal and spatial domain.Moreover,the time series of SCHA coefficients reflect the procecss of ionospheric activity explicitly,e.g.,the coefficient 0,0 depicts the mean regional ionosphere TEC,which is confirmed by the result deduced by GIM parameters of CODE,one of IGS analysis centers.That implies that SCHA mode can be used to predicate regional ionospheric TEC.Due to more GPS measurements over China involved in the modeling,SCHA model provides more precise TEC estimation in the region than IONEX data delivered by IGS analysis centers.
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Papers by Jingbin Liu