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Re: LF: Re: Loran C

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Subject: Re: LF: Re: Loran C
From: Stewart Bryant <[email protected]>
Date: Fri, 20 Jun 2008 11:58:19 +0100
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US base stations do need time ... and yes they do have
have GPS receivers (which BTW are not cheap) at the towers.
However I assumed that we were talking about the UK
when I answered.

When the IETF TICTOC WG files its reports on the Paris Interim
that happened earlier this week I will point you to a
chart that shows current and NG services and what the timing
requirements are.

As for GSM referenced below, there is definitely no external
time reference used - just 50ppb or better frequency reference.

Stewart G3YSX

Andy Talbot wrote:
The whole over-air interface for the mobile phone system has to be
locked - the frame structure in GSM is critical to microseconds, and
has to be synchronised between all base stations.  I believe 3G is
even more time-critical, with the PN codes carefully adjusted for
multiple users, with fine tuning for base-mobile delay.  So they must
have accurate timing somewhere, but is it derived locally or is there
a central distribution.



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