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From: "Tauno Voipio"
References: <email@example.com> <4Ini9.firstname.lastname@example.org>
Subject: Re: Extracting time from GSM / mobile phone transmissions?
X-Newsreader: Microsoft Outlook Express 5.50.4522.1200
Date: Fri, 20 Sep 2002 08:02:44 GMT
NNTP-Posting-Date: Fri, 20 Sep 2002 11:02:44 EET DST
Organization: Sonera corp Internet services
"Taws" wrote in message
> > > I have in the past asked about a cheap way of extracting *accurate*
> > > time from GPS (not possible), or timecode signals (possible).
> > >
> > > What about doing it from mobile phone signals. These are everywhere in
> > > the developed world, although AFAIK the standards differ between e.g.
> > > the USA and Europe.
> > >
> > > Also this needs to work in a light aircraft, say 20000ft, so the
> > > reception might not be too great.
> > The mobile phone is out of question in an aircraft - the cellular
> > does not stand the antenna height. In many countries (including mine,
> > Finland) the use of mobile phones is prohibited in an aircraft of any
> > due to air safety reasons.
> > The horizon distance at an altitude of 20000 ft is about 160 NM - enough
> > wake up all the GSM ground stations in an average-size European country.
> Regulations aside, I think he's asking about only receiving signals from
> base station to use them for getting time, not transmitting on GSM freqs.
> We need a cellular engineer to join in and tell us if time is available on
> GSM phone channels.
> Why isn't GPS accurate enough ?
GPS must be more than enough - to get a good fix, the time must be resolved
to within 100 ns or better. I think that the original poster thinks GPS
calculation too complicated (GSM in not much simpler).
Before providing anything useful, GSM needs a two-way communication.
tauno voipio @ iki fi
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