[time-nuts] Timing over low bandwidth channels

[Bob Camp]

Hi

... and for a very low power system, there's no reason to stick with a "short" 512 bit data set, or a "fast" 1 second rep rate. 

If the signal is a "only at night" sort of thing (as I'm guessing it is over that path), all you really might do is a couple of time transfers a night. A code that marked 10 minute slots would do the trick. Make it nice and long so you don't loose precision. 

Bob

 
On Dec 9, 2010, at 5:55 AM, Poul-Henning Kamp wrote:

> In message <20101209105031.6104C80003B at ip-64-139-1-69.sjc.megapath.net>, Hal Murray writes:
> 
>> Is there a similar sort of high level picture about sending timing info?  I'm 
>> not even sure what the units are.
> 
> Basically with timing you only send one bit: "now"
> 
> The most precise way to send that bit is to use a very long PRNG
> spreading code, and identify the correlator output peak using
> statistical estimation on the slopes up to the peak.
> 
> DCF77 sends a 512 bit PRNG every second and in hand-run testes I have
> been able to determine the peak of the correlation with precision which
> is 100-500 times better than the second to second jitter on the 1200km
> propagation.
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be explained by incompetence.
> 
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