CosmoS Dim 04 Mar 2007, 00:59
Space Opera a écrit:Ils n'ont apparemment pas encore spécifié les codes pseudo-aléatoires de chaque PRN (ou du moins je ne les ai pas encore vus publiquement) mais seulement les structures du signal en spectre étalé et du signal numérique.
Il va encore falloir attendre pour notre récepteur !
C'est dans la partie 7 du document. Un document plus complet est disponible ici:
http://www.galileoju.com/doc/Galileo%20Navigation%20Primary%20Codes.zip
Je découvre que l'université de Cornell avait "cracké" les codes peu avant leurs publication par l'ESA:
http://www.news.cornell.edu/stories/July06/GPS.code.cracked.TO.html
Pas très sympa pour l'Europe et Galileo, ces passages où Cornell prétend (presque) avoir fait oeuvre de salut public en craquant ces codes:
"Because GPS satellites, which were put into orbit by the Department of Defense, are funded by U.S. taxpayers, the signal is free -- consumers need only purchase a receiver. Galileo, on the other hand, must make money to reimburse its investors -- presumably by charging a fee for PRN codes. Because Galileo and GPS will share frequency bandwidths, Europe and the United States signed an agreement whereby some of Galileo's PRN codes must be "open source." Nevertheless, after broadcasting its first signals on Jan. 12, 2006, none of GIOVE-A's codes had been made public.".
(...)
Galileo eventually published PRN codes in mid-April, but they weren't the codes currently used by the GIOVE-A satellite. Furthermore, the same publication labeled the open source codes as intellectual property, claiming a license is required for any commercial receiver. "That caught my eye right away," said Psiaki. "Apparently they were trying to make money on the open source code."
