anyone running GPS clocks in Southeastern Georgia?

Cutler James R james.cutler at consultant.com
Fri Jan 21 15:52:32 CST 2011


On Jan 21, 2011, at 4:23 PM, Michael Holstein wrote:

> 
>> I'd be curious to see what effects (if any) those who use
>> GPS-disciplined NTP references in Southeastern Georgia see from this
>> experiment.
>> 
> 
> Aren't CDMA BTS clocked off GPS?
> 
> NTP isn't going to be the only "ripple".
> 
> Regards,
> 
> Michael Holstein
> Cleveland State University
> 

Possibly relevant section from
Agilent
Designing and Testing 3GPP W-CDMA
Base Transceiver Stations
(Including Femtocells)
Application Note 1355

1.15 Asynchronous cell site acquisition
One of the W-CDMA design goals was to remove the requirement for GPS synchronization.
Without dependence on GPS, the system could potentially be deployed in locations
where GPS is not readily available, such as in a basement of a building or in temporary
locations. W-CDMA accomplishes this asynchronous cell site operation through the
use of several techniques.
First, the scrambling codes in W-CDMA are Gold codes, so precise cell site time synchronization
is not required. There are, however, 512 unique Gold codes allocated
for cell site separation that the UE must search through. To facilitate this task, the
SSC in the S-SCH channel is used to instruct the UE to search through a given set of
64 Gold codes. Each set represents a group of eight scrambling codes (64 x 8 = 512).
The UE then tries each of the eight codes within each code group, in an attempt to
decode the BCH. The ability to recover the BCH information (system frame number)
completes the synchronization process.

James R. Cutler
james.cutler at consultant.com








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