Nel Samama

Interference Mitigation in a Repeater and Pseudolite Indoor Positioning System

The widespread use of the personal navigation devices makes indoor positioning a major technological issue. The development perspectives of location-based services dramatically increase the importance of developing adequate solutions. In this paper, we carry out a theoretical study of an indoor positioning technique based on time-delayed Global Navigation Satellite Systems (GNSS) repeaters. It is a simple solution deploying minimal infrastructure which can use either outdoor repeated Global Positioning System (GPS) signals or a single signal generator. However, the positioning method presents limitations in terms of correlation and tracking performances. The paper presents theoretical approaches in order to overcome the interference problems and to improve the quality of the GPS signal reception. The new system based on ldquorepealitesrdquo (that comes from repeater and pseudolite) makes the best use of repeater and pseudolites in order to allow a fair continuity of the GNSS service indoors.

Multipath Insensitive Delay Lock Loop in GNSS Receivers

The code measurement suffers from multiple error sources and especially multipath. The latter is unpredictable and changes in space and over time. Many interesting multipath mitigation techniques have been proposed. Most of them are not sufficiently effective for precise positioning using the code measurement. This paper presents a multipath insensitive delay lock loop that aims to improve the pseudorange measurement precision in the presence of multipath. This code loop is simple and does not require postprocessing of observables. Simulation and real implementation results showed that the proposed code loop dramatically improves the tracking error due to multipaths. Tracking error is limited to 1 m on pseudorange in typical multipath environments. This loop is more sensitive than the standard delay lock loop to thermal noise and applies predominantly to strong GNSS signals.

RF subsampling GNSS receiver: Potential advantages and feasibility study

The American GPS and Russian GLONASS satellite positioning systems have been operational since the 90s. Other GNSS systems are under development like European Galileo and Chinese Compass systems. Several mass market GNSS products allow users to have their positions, speed and time, but the majority of them are limited to a single standard and do not allow positioning in no coverage areas. Hence, it is very interesting to have a single receiver that includes several positioning systems which is capable of providing precise position indoors and outdoors. This paper deals with a new GNSS receiver architecture for GPS, GLONASS and Galileo radio signals characterized by low power and high sensitivity, also capable of providing outdoor to indoor positioning service. The proposed architecture is based on an RF subsampling down-conversion topology. A fixed subsampling frequency is chosen to properly down-convert the three constellations RF bands to a fixed IF band, which relaxes the IF filter design. A Direct Digital Converter is then proposed to perform quadrature down-conversion to baseband. Simulation results show high gain and low noise for the designed RF front-end and validate subsampling frequency choice through multiband GNSS receiver condition.

Indoor positioning using GPS transmitters: Experimental results

The paper presents the results of an experimental campaign of the GNSS transmitter-based approach for indoor positioning. Details on the chosen setup are given and the main features of the system are described in full. Comments on the positioning accuracies obtained, together with the description of the real environment are provided and an analysis of the performance of the system is proposed. For the next few years the continuity of the positioning service indoors will continue to be a real challenge. GNSS, sensor networks or WLAN approaches have been proposed in order to provide this continuity [1–4]. The GNSS-based approaches aim at making a better exploitation of the satellite signal on the receiver side. Unfortunately, techniques like HS-GPS or A-GPS [5–6] do not seem to provide a definitive solution. Local infrastructure-based solutions can help establish a final system with good accuracy and a wide coverage: the approach described in the paper uses GPS transmitters that make GPS signals available indoors.

Current status of the repealite based approach: A sub-meter indoor positioning system

The paper presents experimental validations of a new approach of GNSS indoor positioning. Combining the best of pseudolites [1] and repeaters [2], the new “repealite” technique allows carrier phase measurements (in order to improve positioning accuracy and multipath mitigation) and self synchronised transmissions. Thus, this method greatly simplifies the still required infrastructure and provides better accuracy. Following theoretical aspects described in previous journals and conferences [3]-[4], we propose to give and comment experimental results. In addition, when dealing with a local infrastructure, deployment considerations are of uppermost importance. In order to remove the coaxial cable links from the central controller to the various indoor transmitting antennas, we decided to use Radio Over Fibre (RoF) techniques. The continuity of the positioning service appears as a real challenge for the next years. GNSS approaches, sensor networks or WLAN are thus proposed in order to provide this continuity. The GNSS based solutions present the advantage of making better use of the satellite receiver. Unfortunately, techniques like HS-GPS or A-GPS do not seem to give a definitive answer. Local infrastructure based solutions help in a final system with good accuracy and large coverage: the one described in the paper uses GPS so-called repealites that make GPS-like signals available indoors.

“Positioning and telecommunications” in the world

Among the numerous technical solutions to positioning, Global Navigation Satellite Systems (GNSS) have a special place. This is mainly due to the fact that they have brought such simplicity of use and low cost that many applications and domains have taken advantage of positioning; for example, civil engineering, the tracking of animals and, of course, car navigation and Location-Based Services (LBS) intended to provide geo-based applications to users. Initially designed for military purposes, the American Global Positioning System (GPS) has found a large public use, both for professional and mass market applications. This success largely exceeded the hopes of its designers and was mainly due to the incredible performances provided to users. Positioning rapidly became a new way to carry out many tasks that demanded considerably more effort than previously. This success, especially for GPS, has led to a strategic problem: if one imagines the deployment of positioning in domains such as transportation, telecommunications or safety, then it is of vital importance to share the management of a global positioning system. This was indeed the problem of the European Union: the decision to launch Galileo, the future European constellation, was closely related to strategic options. This was also the case for GLONASS, the Russian constellation launched in the 1980s, and for COMPASS, the future Chinese satellite-based navigation system. The original goal of GPS was to allow positioning in environments with no local or regional ground infrastructure or where the deployment of an infrastructure would be difficult, e.g., at sea or in the desert. Of course, the problem of positioning did not start with satellites and many previous techniques were used. The success of GPS in many applications, mainly transportation, means that satellite-based navigation has entered the public mind, although it still has many limitations. Some limitations, such as coverage, availability or even integrity are being largely dealt with in the scientific and industrial GNSS communities.

Pseudolites/repeaters infrastructure autopositioning approach—mathematics and first simulation-based results

In the various infrastructure-based indoor positioning systems using Global Navigation Satellite System signals, i.e. pseudolites, repeaters, and repealites, there is the need for the terminal to know the positions of the various transmitters. Some techniques have been proposed for high accuracy pseudolite systems, but they require carrier phase measurements and a careful choice of some specific test locations. Other approaches consider that these data are simply available by any means: Of course, this can be achieved through manual distance measurements and the use of maps of the indoor environment. In this paper, we describe a new method that is based on a two-step approach. The first one consists in deploying the system. The second one is the calculation of the position of the transmitters through classic code measurements for a few specific chosen locations. Thus, the system can be deployed without any constraint and the locations of the transmitters calculated through a basic set of elementary measurements. The theoretical method is first described and the resulting accuracy of the position of the transmitters is then evaluated through theoretical calculations. In addition, electromagnetic simulations are carried out in order to estimate the pseudo-range errors of the proposed measurements: The accuracy of the determination of the position of the transmitters is then estimated (note that two receiver tracking loop implementations are considered). Thus, the accuracy of the proposed method is evaluated theoretically and through simulations.