Alexandre Vervisch-Picois

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.

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.