Herbert Graf wrote:

> On Wed, 2005-04-06 at 14:12 -0600, Robert Rolf wrote:
> 
>>All digital PCS cellular systems
>>use GPS for synchronization between nodes. 
> 
> Are you sure about that? While I know that CDMA based technologies have
> GPS antennas at each site, I've never seen GSM, TDMA or iDEN sites with
> those antennas, and as I understand it GPS is not necessary with those
> techniques.
> 
> Please correct me if I'm wrong.

GPS accuracies are not a _requirement_ for GSM/TDMA/iDEN
systems but it seems to be commonly done (perhaps just for
the frequency standard). I shouldn't have said "all" since
this is a global list.
All the Fido (GSM) sites in Canada that I have seen (nearly a dozen
in my travels) have a GPS antenna.
http://www.arcx.com/sites/Fido%20Gallery%20(Old).htm

All the Rogers sites (TDMA/GSM) I have seen also have a GPS antenna.
It may be quite different in the US.

You are correct that iDEN sites do not need GPS accuracies.
It certainly IS a requirement for CDMA sites in order that
the PN codes not overlap in phase between adjacent sites.

Comparison info on the technologies.
http://www.arcx.com/sites/Technical%20Comparison.htm

Some detailed info on GSM format since TDMA is pretty much dead
in North America.
http://www.mobilecomms-technology.com/projects/gsm/

My apologies for not thinking globally.

Robert

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