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Re: LF: Re: Loran C

To: [email protected]
Subject: Re: LF: Re: Loran C
From: "Andy Talbot" <[email protected]>
Date: Thu, 19 Jun 2008 18:28:56 +0100
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Good - I'm glad to know the telecomms opeators have thought about the
vulnerabilities inherent with putting all their eggs into the GPS
timing basket.  I had been told - clearly from a not too informed
source - that GPS timing units were used at each base station.

Does the same apply to 3G (or GSM for that matter) mobile networks as well?

Andy  G4JNT


2008/6/19 Stewart Bryant <[email protected]>:
> Andy Talbot wrote:
>>
>> The article has a very good point to make about GPS jamming though. I
>> think its probably the first time I've seen it talked about in the
>> open-press.  Our telecomms infrastructure now is so critically
>> dependent on accurate timing that a few well deployed low power
>> jammers could cause serious disruption.
>
> Although modern communications systems are dependent on sync,
> the current systems in the UK need frequency not time.
>
> Although the UK SDH networks use GPS for local time sources,
> to drive reference oscillators, all the systems I know
> use multiple Cesiums as a backup. Most other networks
> (for example the mobile phone networks) connect to
> an SDH network by some means or other and take their sync
> from that source.
>
> The big R&D problem in this space is how we manage the
> migration to packet networks with Ethernet delivery, and
> great lengths are being taken to avoid the need to rely
> on GPS for critical sync functions. Indeed GPS-only sync
> would be regarded as a show-stopper by all of the sync
> network designers I have spoken to.
>
> A lot of newer sync technology (the media access systems)
> needs relatively course (1us class) time as well as frequency
> to function, but there is work in hand to deliver that
> over packet networks (IEEE1588, IETF TICTOC etc)
>
> So I would not worry about GPS jamming disrupting comms.
>
> Navigation is a different matter, and as Alan says Loran
> is vulnerable, perhaps not quite as vulnerable as civilian
> GPS, but certainly more vulnerable than seems to be claimed.
>
> Stewart/G3YSX
>
>
>



-- 
Andy G4JNT
www.scrbg.org/g4jnt


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