Damien Kubrak

Nominal GNSS pseudorange measurement model for vehicular urban applications

Certain GNSS applications conceived for road users in urban scenarios must meet some particular integrity requirements to assure the system safety, reliability or credibility. For instance, GNSS-based Road User Charging is one of these applications that recently has attracted special interest. A correct design of such applications needs the knowledge of the GNSS error distribution. Furthermore, the GNSS error model should have been built with overbounding techniques. The user is a vehicle equipped with a GNSS receiver that may track different signals of various systems (GPS, Galileo, SBAS), in a single-or dual-frequency configuration. The different error sources contributing to the total pseudorange error are identified, analyzed and modeled, using overbounding techniques when necessary. Finally the pseudorange measurement error model is obtained and analyzed for different receiver configurations.

Receiver Autonomous Integrity Monitoring of GNSS Signals for Electronic Toll Collection

Various road user charging mechanisms are used to control traffic and its resulting pollution, as well as revenue sources for reinvestment in the road infrastructure. Among them, electronic toll collection (ETC) systems based on user positions estimated with Global Navigation Satellite Systems (GNSS) are particularly attractive due to their flexibility and reduced roadside infrastructure in comparison to other systems such as tollbooths. Because GNSS positioning may be perturbed by different errors and failures, ETC systems, as liability critical applications, should monitor the integrity of GNSS signals in order to limit the use of faulty positions and the consequent charging errors. The integrity-monitoring systems have been originally designed for civil aviation; hence, they need to be adapted to the ETC requirements. This paper studies the use of receiver autonomous integrity monitoring (RAIM), which are algorithms run within the GNSS receiver and, therefore, are easier to tune to ETC needs than other systems based on external information. The weighted least squares residual RAIM used in civil aviation is analyzed, and an algorithm modification for ETC is proposed. Simulations demonstrate that the proposed RAIM algorithm has a superior level of availability over civil-aviation-based RAIM procedures, particularly in urban environments.

Analysis of GNSS integrity requirements for road user charging applications

GNSS-based Road User Charging (RUC) systems are particularly interesting because of their flexibility and reduced roadside infrastructure. At present, truck toll collection systems based on GPS receivers installed on the vehicles are already deployed in German and Slovak motorways. Reliability of road tolling systems is fundamental in order to limit the loss of revenue because of undercharging and the user claims because of overcharging. Consequently, GNSS integrity monitoring plays a key role in such systems, providing trustful positioning data that keep position errors and their associated legal or economical consequences within given limits. Nevertheless, the design of GNSS integrity algorithms like RAIM requires a deep knowledge of the characteristics of the application and GNSS errors. This paper analyzes the required parameters to develop RAIM algorithms for road tolling applications in urban and rural environments.

DINGPOS, a GNSS-based multi-sensor demonstrator for indoor navigation: Preliminary results

The goal of this paper is to present the architecture and first performance results of the DINGPOS platform. The DINGPOS platform (Demonstrator for INdoor GNSS POSitioning) is a project funded by the ESA that covers the design, development and integration of an experimental indoor positioning system based on the fusion of three different technologies: High Sensitivity GNSS (GPS and the future Galileo), MEMS-based Pedestrian Navigation System and WIFI. This paper introduces the different architectural trade-offs of the final platform and presents the first results of its performance and capabilities with real data.

Field test performance assessment of GNSS/INS ultra-tight coupling scheme targeted to mass-market applications

This article describes field test results of hybridization between MEMS inertial measurement unit (IMU) and GPS L1 C/A signal using an ultra-tight coupling (UTC) architecture. A software receiver is used to post-process raw GPS signal and IMU measurement recorded during the field tests. Both indoor and outdoor environments are explored and UTC with MEMS is compared to UTC with high-grade IMU and vectorized GNSS standalone positioning.

Optimizing GNSS navigation data message decoding in urban environment

Nowadays, the majority of new GNSS applications targets dynamic users in urban environments; therefore the decoder input in GNSS receivers needs to be adapted to the urban propagation channel to avoid mismatched decoding when using soft input channel decoding. The aim of this paper consists thus in showing that the GNSS signals demodulation performance is significantly improved integrating an advanced soft detection function as decoder input in urban areas. This advanced detection function takes into account some a priori information on the available Channel State Information (CSI). If no CSI is available, one has to blindly adapt the detection function in order to operate close to the perfect CSI case. This will lead to avoid mismatched decoding due to, for example, the consideration by default of the Additive White Gaussian Noise (AWGN) channel for the derivation of soft inputs to be fed to soft input decoders. As a consequence the decoding performance will be improved in urban areas. The expressions of the soft decoder input function adapted for an urban environment is highly dependent on the available CSI at the receiver end. Based on different model of urban propagation channels, several CSI contexts will be considered namely perfect CSI, partial statistical CSI and no CSI. Simulation results will be given related to the GPS L1C demodulation performance with these different advanced detection function expressions in an urban environment. The results presented in this paper are valid for any kind of soft input decoders, such as Viterbi decoding for trellis based codes, the MAP/BCJR decoding for turbo-codes and the Belief Propagation decoding for LDPC codes.