Anne-Christine Escher

Multipath study on the airport surface

Airport Navigation will require more stringent localization performance requirements than in-flight navigation [1]. GNSS signals (Global Navigation Satellites Systems) can be envisaged to elaborate the aircraft estimate position on the airport surface. To improve the performance of localization on the airport, the errors on GNSS signals particular to the airport environment must be characterized. Most of these errors are well known such as ionosphere error, troposphere error, etc, and do not depend on the airport environment. But to achieve the expected sub-metric performance, it is necessary to better model multipath error for which a model already exists but is valid for operations from en-route down to CAT I only. In this paper, an analysis of real GPS measurements (using code pseudo range measurement, carrier phase measurement, Doppler measurement and the estimate C/N0 ratio measurement) during taxiing operation on the airport surface is conducted. The goal of this paper is to evaluate when multipath occurs and to compare the multipath model (elaborated from the standard deviation of the measurement errors due to multipath) based on those collected measurements in the airport with different models proposed in the literature (not necessary proposed for airport navigation).

Implementation of Code Shift Keying signalling technique in GALILEO E1 signal

One of limitations of the current GNSS signals is their low data information rate. This low data information rate does not allow, for example, the transmission of additional commercial services or the transmission of redundant ephemeris data. The Code Shift Keying (CSK) is a signaling technique specifically designed to increase the transmission bit rate of a spreading spectrum signal. Therefore, one solution to increase the data information rate of the GNSS signals is to introduce the CSK technique in them. In this paper, the implementation of the CSK technique into GNSS signals is inspected through the development and analysis of the likelihood ratio expression of the bits transmitted inside a CSK symbol, and through the identification of the best mapping between bits belonging to a word and bits transmitted inside a CSK symbol. Finally, the impact of the CSK technique on the GALILEO E1 signal is analyzed by calculating the CSK demodulation performance for a given scenario and the drawbacks of the technique on the signal acquisition and tracking processes.

Analysis of the GPS acquisition environment: indoors and outdoors

The emergence of the LBS services (location based services) creates the need for indoor and outdoor positioning. Indoor environments refer to environments inside buildings, and outdoor environments refer to urban environments (streets). Indoor localization poses a true challenge for classical positioning systems. Indeed, radio propagation in indoor environments is affected by several factors particularly multipath, shadowing, cross-correlations, receiver mobility, interference. Urban environments are also challenging environments where multipaths problems are even more pronounced. This paper aims at analyzing such environments in the frame of a state of the art of the GPS acquisition environment