Christophe Macabiau

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.

Performance study of FLL schemes for a successful acquisition-to-tracking transition

This article focuses on the analysis of several FLL schemes for different GNSS signals in order to success the acquisition-to-tracking transition at low received C/N0. In a first part, a discussion on different FLL discriminators is lead by comparing frequency error response, linear region, data bit transition insensitivity. Then, based on Monte-Carlo simulations, for each signal, the choices of FLL scheme parameters as the discriminator, loop bandwidth, correlator outputs combination technique are studied in order to highlight the FFL schemes which provide the best performance in terms of probability to get locked.

Complementary signal structure proposals for future airborne SBAS L5 signal and other non-airborne applications

This paper studies complementary signal structures to the SBAS L5 SIS ICD definition which increases its original bit rate without degrading or even improving the SBAS L5 SIS ICD signal key performances. The proposition of this paper is based on modifying only certain characteristics of the current SBAS L5 SIS ICD signal structure and on keeping the signal characteristics which allow a perfect compatibility with SBAS L5 SIS ICD message content: symbol rate, bit information rate (250 bps), basic information units of 250 bits and capability of interrupting the nominal message at each second in order to transmit alarm messages. The main signal design modifications are first the introduction of linear block channel codes, instead of a convolutional code, in order to reduce header and CRC bits and in order to decrease the signal demodulation threshold. Second, new signal components, such as the synchronization component or a second data component, are introduced allowing an easier synchronization and increasing the effective bit rate. Smart combinations of the two data components are suggested to not degrade the final demodulation threshold. Finally, the selective introduction of a Code Shift Keying (CSK) modulation is also proposed to further increase the bit rate. Demodulation, carrier phase tracking and secondary PRN code acquisition performances are explained and analyzed for the complementary proposed signal structures.