Validating the signal structures for the European Satellite Navigation Program GALILEO

Abstract

Abstract Amongst the preparatory activities in support of the European Satellite Navigation Program GALILEO, the European Space Agency (ESA) regard the definition of the signal structure and its in-depth laboratory verification and optimisation as pivotal in the development of GALILEO. The major challenge is the need to exploit with maximum efficiency the limited frequency bands that will become available to satisfy the GALILEO service requirements [1] . For that reason ESA initiated during 199 the definition and development of a comprehensive signal validation testbed by European industry. Strategies for the provision of the so-called Open Access Service (OAS) and Controlled Access Services (CAS) are discussed together with the related signal and message structures. In order to cope with the bandwidth limitations, tightly band-limited CDMA signals will be optimised for both OAS and CAS. To provide robust reception of the navigation messages, signals are convolutionally encoded, interleaved and protected by CRC. CAS signal robustness will be further enhanced by the adoption of a high chipping rate spreadspectrum signal carrying a code division multiplexed pilot. The signal -validation testbed described in the paper will be composed of a signal generation unit, a dynamic channel simulator, a multi-channel demodulator and a navigation processing unit. This ensemble will constitute a very powerful and flexible test facility to validate and optimise the GALILEO structures. The testbed, utilising state-of-the art digital signal processing techniques, will efficiently and accurately evaluate the performance of the new signal structures and widelane (TCAR) techniques in a realistic multi-satellite multi-frequency environment.