GNSS transmitter based indoor positioning systems : deployment rules in real buildings

International audienceIndoor positioning appears to be a real challenging topic and many techniques have been proposed these last ten years, ranging from High-Sensitivity GNSS to sensor networks, through Assisted-GNSS or WLAN based approaches. No ultimate solution seems yet to provide the answer to the problem, probably crucial to Location Based Services, of continuity of the availability of the positioning from outdoors (where GNSS are such good candidates) to indoors. Current works are mainly oriented towards hybridisation techniques. The repeater approach is based on the use of GNSS so-called repeaters in order to provide GNSS availability indoors through the way of an amplification of the signals received by an outdoor antenna (typically located on the roof). The complete system, already presented in previous conferences, uses four repeaters in order to provide a full 3D 1 to 2 meter accuracy positioning, indoors. The measurements, performed at the receiver end, are the pseudo-ranges at the instant of transition from one repeater to the next, the transmission being achieved through a sequential scheme (only one repeater transmitting at any given time). Since regulations tend to be provided (ECC reports on maximum transmitted power allowed) for both repeaters and pseudolites, we carried out indoor propagation simulations, for real environments, in order to define realistic deployments of both systems. Different buildings have been considered and modelled. Coverage and positioning accuracy results are presented for various hypotheses: full 3D (3D positioning all over the building), 2.5D (2D positioning all over the building and 3D provided only where floor level changes are possible, i.e. near the stairs and near the lifts) and only 2D (assuming the floor level is available through another mean). The number of repeaters/pseudolites required for a complete coverage of the buildings is also given and commented (the specific case of the Institut Telecom campus in France is analysed

A universal and autonomous positioning system based on wireless networks connectivity

International audienceIndoor positioning appears to be a real challenging topic and many techniques have been proposed these last ten years, ranging from High-Sensitivity GNSS to sensor networks, through Assisted-GNSS or WLAN based approaches. No ultimate solution seems yet to provide the answer to the problem, probably crucial to Location Based Services, of continuity of the availability of the positioning from outdoors (where GNSS are such good candidates) to indoors. Current works are mainly oriented towards hybridisation techniques. Many interesting results are provided with accuracies down to a metre sometimes. But this performance is always linked to associated constraints such as specific deployments, calibration phases, non-mature technologies, etc. We propose another approach based on the use of all available wireless networks and all available connections between mobile terminals. Our approach is based on two fundamental steps: the study of the so-called "visibility" and the estimation of geographical links. The visibility estimates which equipments in the environment have the ability to be radio connected to the terminal and a three-dimensional graph is build according to relative distance estimates between terminals. This graph enables the visualisation of the geographic positions of each device. Various models of visibility have been implemented and evaluated through comparisons of positioning in several elementary scenarios. MatLab simulation results are presented to validate this approach. The positioning accuracy ranges typically from 2 to 10 metres, depending on the environments, density of terminals, percentage of known location terminals and dynamic scenarios. One should keep in mind that these accuracies, even if they are not among the best published, are achieved with no additional infrastructure and is potentially implementable on all today communication devices. Furthermore, this is bound to work outdoors as well as indoors

Repeater based indoor positioning summary of experimental campaigns of measurements

International audienceThe repeater indoor positioning system is based on the use of GNSS so-called repeaters in order to provide GNSS availability indoors through the way of an amplification of the signals received on an outdoor (typically on the roof) antenna or generated by a signal generator. The complete system, already described in previous conferences, uses four repeaters in order to provide a full 3D indoor positioning. The measurements, at the receiver end, are the pseudo-ranges at the instant of transition from one repeater to the next, the transmission being achieved through a sequential scheme (only one repeater transmitting at any given time). This approach implements a sort of "time differential" approach that provides a good positioning accuracy. The multipath problem is dealt with through the use of the SMICL (Short Multipath Insensitive Code Loop) design, already fully described in previous papers. In addition regulations tend to be provided for both repeaters and pseudolites and must be taken into account. The complete system, including both the infrastructure to be deployed and the various algorithms required at the receiver end (mainly the tracking loops), has been implemented in such a way it is possible to test and evaluate the indoor positioning in all desired environments. Thus, measurement campaigns were performed in Italy and in France in various indoor environments including large halls, classrooms, amphitheatre and car parks. Various receivers were also tested with different receiving bandwidth, ranging from 2 to 30 MHz, using either a standard Delay Locked Loop or the above mentioned SMICL approach. Results are provided concerning of course the accuracy of the achieved positioning, but also a full comparison of the performance of the receivers and associated data processing. All these results are also presented for the various tested environment

Multipath modelisation of typical indoor environments optimisation of GNSS based indoor positioning

International audienceThe present paper describes a detailed numerical simulation study of indoor propagation carried out in order to evaluate multipath effects on the GNSS repeater based approach in various environments. Previous work studied multipath effects in a very restricted areas about 50 square meters with metallic walls. The goal of the present paper is to provide the required complementary information to evaluate the multipath problem in typical indoor environments and to propose some directions of optimisatio

GNSS repeater based approach for indoor positioning : current status

International audienceThe present paper presents an overview of the GNSS repeater based approach for indoor positioning. The latest theoretical and experimental results are presented in order to highlight the interesting features of the proposed method. The advantages of this method in terms of accuracy, cost, and simplicity of the infrastructure will be identified furthermore. Indoor positioning is a very important topic, mainly in terms of continuity of services. This leads to many theoretical and experimental works in this field using a large range of techniques, from purely GNSS approaches to networks of physical sensors or Wireless Local Area Telecommunication Networks. Among all these techniques, the GNSS based ones present the advantage of making better use of the satellite receiver, which is considered to be the "best" solution for outdoor applications (even with the current limitations in urban canyon environments). Thus, techniques like High Sensitivity GPS or Assisted GPS have been widely investigated within the satellite community: results are interesting but it does not seem to give a definitive answer to indoor positioning. Pseudolites and repeaters are now solutions that could help in a final system with good accuracy and a large coverage: studies are being carried out and show encouraging results for both approaches. This paper focuses on the repeater system, previously described in various papers [1], presenting its latest theoretical and experimental results. The paper is organized as follows. Section 2 outlines the theory of the GNSS repeater based approach. The multipath propagation simulations, performed in order to provide us with deployment rules for the repeaters, as well as a better understanding of the multipath effects on the positioning accuracy, are described in Section 3. New receiver architectures, developed in order to optimise the accuracy of the measurements of the phase jumps, are presented in Section 4. Finally, real deployments and real conditions positioning results will be presented and discussed in Section 5, before concludin

Multipath effects on the GNSS repeater based approach : tracking loop discriminator impact on multipath mitigation

International audienceThis paper presents a study of the impact of different tracking loop discriminators on the precision of the indoor positioning carried out in order to evaluate multipath effects on the GNSS repeater based approach. In addition, antenna characteristics are considered. A previous work [1] evaluated the impact of multipath characteristics (power, delay and carrier phase) on the estimation of the distances in different indoor environments. Different antenna patterns were studied and significant differences were observed while changing characteristics like the pattern or the orientation of the repeater antennas. The goal of the present paper is to provide directions of optimisation of the multipath problem in indoor environments by combining the effects of the antenna characteristics, the multipath propagation mechanisms and the tracking code loop discriminator performances. The theory of the GNSS repeater approach, together with experimental results validating its principle was fully described in previous papers [2]. Briefly, it consists in using four GNSS repeaters in a sequential mode, with only one repeater transmitting at a given time. A transmission cycle is thus set up in order to carry out measurements of the pseudo-range jumps at the transition from one repeater to the next. After a complete cycle four such jumps are available and allow the indoor calculation, through a classical GNSS computation. However, as often indoors, the GNSS repeater based approach is strongly affected by multipath, the main problem being that their effects are difficult to evaluate and/or estimate [3]. Indeed, the multipath characteristics have fast variations in time and space, hence there is no exact model to eliminate it. In order to carry out multipath evaluation and optimisation we study the influence of multipath characteristics on the positioning precision. This study is performed in two steps: first, all the multipath components propagating between each repeater antenna and the indoor receiving antenna are determined using a propagation simulation software. Furthermore all the multipath rays are injected in a Matlab/Simulink GPS receiver simulator which evaluates the error on the pseudo-range caused by the multipath. The paper is organized as follows. Section 2 describes the simulations setup. The multipath propagation simulation software used in order to determine the multipath components characteristics is presented here, including the description of the propagation environment and of the considered antennas. The GPS receiver simulator, implemented using Matlab/Simulink is presented furthermore. Two different implementations of this receiver are described and compared. The first one is based on the usual Early-Late GPS tracking loop discriminator, while the second is based on an optimized discriminator [4] developed in order to mitigate the short multipath (with delays of less than 0.5 code chip), which are the ones occurring in typical indoor environments. Section 3 presents the simulation results of the predicted distance between each repeater and each receiving antenna position. A comparison of the impact of the two tracking loops is performed for two different types of repeater antennas, validating the theoretical performances of the optimized discriminator. Section 4 evaluates the precision of the positioning by estimating the impact of multipath components on the pseudo-range jumps at the transition from one repeater to the next. Finally, Section 5 summarizes the paper and conclude

Optimised tracking loop for multipath mitigation : case of repeater based indoor positioning system

International audience

Indoor positioning using GPS transmitters : experimental results

International audienceThe 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 indoor