Understanding the GIOVE-B broadcast codes of the Galileo system

Europe´s second Galileo In-Orbit Validation Element (GIOVE-B) satellite was launched on April 27, 2008, at 22:16 UTC and successfully began transmission on May 7. On the same day, we observed signals in the L1, E5a, and E5b bands, with the L1 spectrum showing multiplexed binary offset carrier (MBOC) modulation. We then identified the generators for the Pseudo Random Noise (PRN) codes in each band. We revealed these codes to be 13- or 14-stage Gold codes, different from the memory codes in the Galileo Interface Control Document (ICD). The GIOVE-B PRN codes have the same code structure as those of the first Galileo test satellite, GIOVE-A. The code generators are the same except for the initial states. However, the signal modulation type in one of the frequency bands is different. The new modulation applied by GIOVE-B ensures more robustness to multipath.