I've been searching around google and even in manufacturer site for this information and found nothing relevant.
Is it possible to turn off GSM module and keep turned on the GPS? How can it be done?
This point is critical to my application since I need to keep GSM module OFF almost all the time and the GPS always ON.
edit: Command manual and product page for Simcom SIM908.
Best Answer
[This started as a comment, but I ran out of room.]
Having the GPS on while GSM is off (or in a low power mode) may be possible. Look into the hardware design guide for SIM908 (4.2MB .doc). Section 4.3 describes the low power modes for GSM and how to enter them. Section 5.2 describes power control for the GPS.
Somebody who had first-hand experience with this module might be able to provide a more definitive answer. E-mailing a carefully crafted question to Simcom 's application support might also be a good idea. (And if they tell you the answer, make sure to post it here on EE.SE for posterity.)