Cell Phone GPS Tracking

[Ex-Member]

OK, that's interesting. I assumed they all just incorporated a SiRFII/III type receiver, with WAAS. So, differential time code from the tower and the GPS Sat? Seems like by the time you did all that, it'd be easier to just use WAAS or old style DGPS with the tower as the DGPS base. Or does the cell phone measure arrival differences between available Sats, then data packets them off to the tower for it to calculate the offset it sees in the Sats? Send the timecode so the tower can go back and get what it saw.

Interesting, if the tower has to be involved, that would complicate things. I assumed a GPS chip would interrupt out of Stndby every couple minutes, just long enough to acquire, then peekAboo the transmitter on a non reliable type channel with a cutdown coordinates packet.

The newer phones are incorporating a true GPS receiver, that gets a lot better position than what the GPCS is capable of getting because of the increased distance between the satellites and device, as well as the accuracy of the on-board clocks. Most of them don't have the true GPS receivers in tehm but depend on the network time signals and divide those to find a position between towers. The towers don't move, so that makes them a good reference.

 

[Snowizard]

There's also a small possibility that they have the antenna setup in such a way as to cause a dead spot right where you are.

Actually thats true. Cell signals can go in all directions, or beamed into areas where there are subscribers, and deadend over treeain where there isn't likely to be any users.

Mooseknuckle, NEXTEL "Iden" protocol is its own unique format, ans different from a "Sprint" labe; phone. Also Nextel operated in the 800 Megahertz frequency spectrum, while most other cell phones (PCS phones actually) operate in thw 2,100-2,400 MHz spectrum, with wider bandwidth for all the whiz-bang features people want now days.

Footnote: How do I know all this stuff? Well I taught cellular and mobile radio field service technicians for 37 year. Actually, cellular since 1984 until I retired in 2000. I still mess with radio's as a sideline.
One of my former students is upper-midwest region srevice manager for Sprint-Nextel. (Class of 1978 )