Assessing the Radio Frequency Compatibility between GPS and Galileo

The Galileo signal plan has been presented in [1] and all the remaining options have been closed since then: the E5b signals (I&Q) central frequency has been frozen to 1207.14 MHz and the E5a and E5b signals (I&Q) chip rates to 10.23 Mcps. Most recent results of design studies are presented in [2]. One of the key requirements for the design of Galileo signal plan has been the compatibility with GPS from a radio-frequency point of view together with the use of some frequency bands that GPS is currently using or plans to use in the future (L1 and L5 bands) in order to foster the development of combined GPS/Galileo receivers for the mass market. To ensure that GPS and Galileo are fully compatible from a radio-frequency point of view, the Galileo program has been supported by several interference studies (see [3,4,5]). This paper builds upon the findings of these studies and stresses on new results. This paper provides an assessment of the radio-frequency compatibility between GPS and Galileo. The basics of interference assessment methodologies are recalled and applied to the case of two RNSS sharing some frequency bands together with a detailed discussion on the adequate figures of merit to be used in such an analysis. Simulation results based on the interference tool developed by the European Space Agency (see [4]) are presented and analyzed.