Scoping Study on Pseudolites

Pseudolites or pseudo-satellites are an emerging technology with the potential of enabling satellite navigation indoors. This technology found several applications that are not limited to indoor navigation. Precise landing, emergency services in difficult environments and precise positioning and machine control are few examples where pseudolite technology can be employed. Despite the great potential of this technology, severe interference problems with existing GNSS services can arise. The problem can be particularly severe when considering non-participating receivers, i.e., legacy devices not designed for pseudolite signals. The design of pseudolite signals is thus a complex problem that has to account for market requirements (modifications of existing receivers for enabling the use of pseudolite signals, measurement accuracy, target application), regulatory aspects (frequency bands to be allocated for pseudoliteservices) and interference problems. The main aspects for the design of a pseudolite signal standard minimizing the interference problem without compromising the location capabilities of the system are considered. The focus is on the signal characteristics and topics relevant for the signal design. A literature review on the different pseudolite applications, prototypes and solutions adopted for minimizing the interference problem is first conducted. Recommendations on the aspects that should be further investigated are then provided.JRC.DG.G.6-Security technology assessmen

Impact of Pseudolite Signals on Non-Participating GPS Receivers

Pseudolites or pseudo-satellites are an emerging technology that has the potential to extend the capability of Global Navigation Satellite Systems (GNSS) indoors and in harsh environments where GNSS services are denied. Although their potential, pseudolites could cause severe interference problems to non-participating receivers, i.e., GNSS receivers unable or not designed to use pseudolite signals. In this report, preliminary results obtained by the IPSC-JRC on the impact of pseudolite signals on commercial non-participating receivers are presented. The analysis considered two pseudolite modulations. In the fist case, the pseudolite signal has same structure adopted by GPS L1 C/A signals whereas in the second scenario a pulsing scheme has been adopted to reduce the interference problem. From the analysis, it emerges that in the case of a continuous pseudolite modulation, the performance of the non-participating receiver is already significantly degraded when the pseudolite signal is about 10 times stronger than the average signal power. More specifically, a 3 dB loss is introduced in the estimated C/N0 of the useful GPS signals. The use of a pulsing scheme significantly mitigates the impact of pseudolite signals and the receiver is able to maintain lock and provide a position solution for all the tested pseudolite power levels. Further investigations are required to determine if higher pseudolite signal powers could affect more severely a non-participating receiver.JRC.DG.G.6-Security technology assessmen

An Assessment of Indoor Geolocation Systems

Currently there is a need to design, develop, and deploy autonomous and portable indoor geolocation systems to fulfil the needs of military, civilian, governmental and commercial customers where GPS and GLONASS signals are not available due to the limitations of both GPS and GLONASS signal structure designs. The goal of this dissertation is (1) to introduce geolocation systems; (2) to classify the state of the art geolocation systems; (3) to identify the issues with the state of the art indoor geolocation systems; and (4) to propose and assess four WPI indoor geolocation systems. It is assessed that the current GPS and GLONASS signal structures are inadequate to overcome two main design concerns; namely, (1) the near-far effect and (2) the multipath effect. We propose four WPI indoor geolocation systems as an alternative solution to near-far and multipath effects. The WPI indoor geolocation systems are (1) a DSSS/CDMA indoor geolocation system, (2) a DSSS/CDMA/FDMA indoor geolocation system, (3) a DSSS/OFDM/CDMA/FDMA indoor geolocation system, and (4) an OFDM/FDMA indoor geolocation system. Each system is researched, discussed, and analyzed based on its principle of operation, its transmitter, the indoor channel, and its receiver design and issues associated with obtaining an observable to achieve indoor navigation. Our assessment of these systems concludes the following. First, a DSSS/CDMA indoor geolocation system is inadequate to neither overcome the near-far effect not mitigate cross-channel interference due to the multipath. Second, a DSSS/CDMA/FDMA indoor geolocation system is a potential candidate for indoor positioning, with data rate up to 3.2 KBPS, pseudorange error, less than to 2 m and phase error less than 5 mm. Third, a DSSS/OFDM/CDMA/FDMA indoor geolocation system is a potential candidate to achieve similar or better navigation accuracy than a DSSS/CDMA indoor geolocation system and data rate up to 5 MBPS. Fourth, an OFDM/FDMA indoor geolocation system is another potential candidate with a totally different signal structure than the pervious three WPI indoor geolocation systems, but with similar pseudorange error performance

Generation of Slot Index Tables for Time-Hopping Pseudolites with the Constructed Congruence Codes

The time-hopping (TH) pulsed pseudolite (PL) can be used to enhance the performance of global navigation satellite systems (GNSS), and the slot index table (SIT) is an important part to form this PL signal. In this paper, a new method to generate SITs for multiple PLs is proposed. The general process of the proposed method is that first different time-hopping slot index (THSI) base matrices are generated based on the constructed congruence codes, and then by combining several different THSI base matrices to constitute a new matrix, the SIT for a PL is formed. Further by changing the combined matrices, different SITs for different PLs can be generated. During this process, two critical factors that affect the performance of the given method, i.e., the collision or hit property of the generated THSI base matrix and the correlation property of the formed SIT, are analyzed in detail. The simulations given at the end of this paper show that compared with many other similar schemes, the SITs given by the proposed method can obtain better correlation performance and detection performance in the receiver, and these results also imply that the proposed method offers a more effective way to design this kind of PL signal

Closely-coupled integration of Locata and GPS for engineering applications

GPS has become an almost indispensable part of our infrastructure and modern life. Yet because its accuracy, reliability, and integrity depend on the number and geometric distribution of the visible satellites, it is not reliable enough for the safety of life, environmental or economically critical applications. Traditionally, this has been addressed by augmentation from dedicated support systems, or integration with other sensors. However, from an engineering perspective only expensive inertial systems or pseudolites offer the accuracy required. In the case of pseudolites, the equivalent of ground based satellites, geometry constraints, fading multipath, imprecise clocks, the near-far effect, tropospheric delay and legislative obstructions make them difficult to implement. This thesis takes a step forward, by proposing a loosely coupled integration with Locata, a novel, terrestrial positioning technology, based on the pseudolite concept. It avoids the above pitfalls by utilising frequency and spatially separated antennas and a license-free frequency band, though this comes at the cost of in-bound interference. Its ability to provide stand-alone position and network synchronisation at nanosecond level is used commercially in open-cast mining and in military aviation. Discussion of Locata and GPS technology has identified their shortcomings and main limiting factors as well as the advantages of the proposed integration. During the course of this research, tropospheric delay, planar solution and known point initialisation ambiguity resolution methods have been identified as the main limiting factors for Locata. These are analysed in various static and kinematic scenarios. Discussion also includes ambiguity resolution, noise and interference detection and system performance in indoor and outdoor scenarios. The proposed navigation engine uses a closely coupled integration at the measurement level and LAMBDA as the ambiguity resolution method for Locata and GPS. A combined solution is demonstrated to offer a geometrical improvement, especially in the respect of height determination, with centimetre to decimetre accuracy and a minimum requirement of two signals from any component. This study identifies that proper separation and de-correlation of Locata and GPS ambiguities and better tropospheric models are essential to reach centimetre level accuracy. The thesis concludes with examples of system implementation including: seamless navigation, city-wide network deployment, urban canyons, a long term-monitoring scenario and indoor positioning. This demonstrates how the proposed navigation engine can be an advantage in areas such as: civil engineering, GIS, mobile mapping, deformation, machine navigation and control

Closely-coupled integration of Locata and GPS for engineering applications

GPS has become an almost indispensable part of our infrastructure and modern life. Yet because its accuracy, reliability, and integrity depend on the number and geometric distribution of the visible satellites, it is not reliable enough for the safety of life, environmental or economically critical applications. Traditionally, this has been addressed by augmentation from dedicated support systems, or integration with other sensors. However, from an engineering perspective only expensive inertial systems or pseudolites offer the accuracy required. In the case of pseudolites, the equivalent of ground based satellites, geometry constraints, fading multipath, imprecise clocks, the near-far effect, tropospheric delay and legislative obstructions make them difficult to implement. This thesis takes a step forward, by proposing a loosely coupled integration with Locata, a novel, terrestrial positioning technology, based on the pseudolite concept. It avoids the above pitfalls by utilising frequency and spatially separated antennas and a license-free frequency band, though this comes at the cost of in-bound interference. Its ability to provide stand-alone position and network synchronisation at nanosecond level is used commercially in open-cast mining and in military aviation. Discussion of Locata and GPS technology has identified their shortcomings and main limiting factors as well as the advantages of the proposed integration. During the course of this research, tropospheric delay, planar solution and known point initialisation ambiguity resolution methods have been identified as the main limiting factors for Locata. These are analysed in various static and kinematic scenarios. Discussion also includes ambiguity resolution, noise and interference detection and system performance in indoor and outdoor scenarios. The proposed navigation engine uses a closely coupled integration at the measurement level and LAMBDA as the ambiguity resolution method for Locata and GPS. A combined solution is demonstrated to offer a geometrical improvement, especially in the respect of height determination, with centimetre to decimetre accuracy and a minimum requirement of two signals from any component. This study identifies that proper separation and de-correlation of Locata and GPS ambiguities and better tropospheric models are essential to reach centimetre level accuracy. The thesis concludes with examples of system implementation including: seamless navigation, city-wide network deployment, urban canyons, a long term-monitoring scenario and indoor positioning. This demonstrates how the proposed navigation engine can be an advantage in areas such as: civil engineering, GIS, mobile mapping, deformation, machine navigation and control

Bridge deformation monitoring with single frequency GPS augmented by pseudolites

Bridges are an important part of the infrastructure of both road and rail networks. As bridge stocks age it is becoming increasing important to monitor their health and predict their lifespan. Current health assessment methods of visual inspection have many drawbacks and so non-destructive evaluation methods such as GPS are becoming more important. This study focuses on the use of single frequency GPS for bridge deformation monitoring. Previous studies have focussed on the use of more expensive dual frequency receivers. This thesis has resulted in the development of single frequency processing software that has enabled these receivers to be used in bridge deformation situations. Improvements in integer ambiguity resolution methods mean it is now possible to be resolve ambiguities instantly for small bridges and greatly reduces ambiguity time for long bridges. The development of this software is outlined along with results from bridge trials. The thesis further looks at extensions to the use of single frequency GPS by outlining experiments conducted with Garmin handheld receivers and also with JNS 100 receivers measuring at 50 Hz. The potential to use Garmin receivers in monitoring applications is demonstrated. The use of 50 Hz data enables the identification of higher frequency bridge dynamics than has ever been possible before. The final investigation looks at using pseudolites to augment the current GPS constellation specifically for bridge monitoring applications. The introduction of pseudolites led to improvements in all three coordinate directions, with the most improvement being seen in the vertical direction

Advanced Location-Based Technologies and Services

Since the publication of the first edition in 2004, advances in mobile devices, positioning sensors, WiFi fingerprinting, and wireless communications, among others, have paved the way for developing new and advanced location-based services (LBSs). This second edition provides up-to-date information on LBSs, including WiFi fingerprinting, mobile computing, geospatial clouds, geospatial data mining, location privacy, and location-based social networking. It also includes new chapters on application areas such as LBSs for public health, indoor navigation, and advertising. In addition, the chapter on remote sensing has been revised to address advancements