I am software developer of GPS-service. The a-gps assumes fast time-to-first-fix. The vendors write about 35 secs. But when i tested on several modern mobile android devices i find strange thing. That sometimes time-to-first-fix is < 35 secs(in the urban open street conditions). And sometimes it is more than 15 mins. On the same device devices. In the same places. Today warm and cold start can be 15-60 secs and tomorrow morning it can be > 15 min. GPRS/GPS/positionnig in mobiles network are on. I see with the help of 3d party software that A-GPS data are fresh (today). But it isn't help. I find such behavior on LG P970 and Archos 101 Tab.
Why? How can speed up and optimize A-GPS time-to-first-fix on Android?