A GNSS Signal Integrity Simulator

Project: Engineering and Physical Sciences Research Council/ BAE SYSTEMS Studentship 2003-2006

Researcher: Andrew Smith

Global Navigation Satellite Systems (GNSS) can provide position, velocity and time information anywhere on or near the surface of the Earth. The first such system widely available to civilian users is the Global Positioning System (GPS), which has been adopted successfully for many different applications. However, a number of critical problems still remain in using GPS for applications requiring a high degree of accuracy or integrity. These problems originate in uncertainties in the signal's environment and can be divided into two areas (i) atmospheric phenomena and (ii) local environment factors. This proposal is to undertake research in these areas by means of developing an advanced GNSS simulator. This will be of key interest for understanding the detrimental effects of the ionised regions of the atmosphere in the low-latitude regions. The project is timely as it coincides with the development phase of the forthcoming European Galileo System. Several questions have been raised about the magnitude of ionospheric scintillation at GNSS frequencies. The physical causes behind these rapid fluctuations in signal amplitude and phase (scintillations) are small-scale irregularities in electron concentration in the ionosphere. The effect on a receiver is still a complicated issue to resolve, since the loss of signal due to low SNR may be caused by local multipath, ionospheric multipath or ionospheric scintillation. Nevertheless, a systematic modelling study can be undertaken to distinguish between these effects and in particular it is intended that this project will address the following question. Is it possible to isolate certain criteria to distinguish between (i) local multipath (ii) ionospheric multipath (iii) and ionospheric scintillation (diffraction) in causing GNSS receiver loss of lock? A number of different receiver types will be modelled and their responses to the signal characteristics will be evaluated.