[135333] in North American Network Operators' Group
Re: anyone running GPS clocks in Southeastern Georgia?
daemon@ATHENA.MIT.EDU (Cutler James R)
Fri Jan 21 16:52:41 2011
From: Cutler James R <james.cutler@consultant.com>
In-Reply-To: <4D39F968.3040005@csuohio.edu>
Date: Fri, 21 Jan 2011 16:52:32 -0500
To: nanog group <nanog@nanog.org>
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On Jan 21, 2011, at 4:23 PM, Michael Holstein wrote:
>=20
>> I'd be curious to see what effects (if any) those who use
>> GPS-disciplined NTP references in Southeastern Georgia see from this
>> experiment.
>>=20
>=20
> Aren't CDMA BTS clocked off GPS?
>=20
> NTP isn't going to be the only "ripple".
>=20
> Regards,
>=20
> Michael Holstein
> Cleveland State University
>=20
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 =3D 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@consultant.com
