Discussion:
[manchesterwireless] Extreme solutions...
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Harry Moyes
2005-08-01 20:54:21 UTC
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In case nobody is watching slashdot

http://wwww.wifiworldrecord.com


Now that's some shooting..


Harry
John Greenwood
2005-08-02 20:24:13 UTC
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Come on Ged you know how this is done,,,


It's with an interositor have you forgotten?

John
Hi Harry,
Post by Harry Moyes
http://wwww.wifiworldrecord.com
Now that's some shooting..
"Ping times varied from 0.01 ms to 400 ms, seeming to average
around 10 ms."
Hmmm... 250/186411 = 0.00134 ... How do you think he gets his signal
to go faster than light? :)
73,
Ged.
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John Greenwood
2005-08-02 21:18:55 UTC
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full plans available here for eager builders if future WIFI
installations.

http://www.shipbrook.com/jeff/interocitor/
Hi John,
Post by John Greenwood
Come on Ged you know how this is done,,,
It's with an interositor have you forgotten?
Even if I hadn't, I wouldn't admit it.
http://www.answers.com/topic/interocitor :)
73,
Ged.
Post by John Greenwood
...
How do you think he gets his signal to go faster than light? :)
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Harry Moyes
2005-08-02 22:11:41 UTC
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Hmmm... 250/186411 = 0.00134 ... How do you think he gets his signal
to go faster than light? :)
I like the colourfully explanations better, but if you want a guess
at the real cause try the following.


Sadly this is a common instrumentation error. The timer resolution in
the OS is limited, and there are two passes at least through the
scheduling algorithm.



submit ICMP frame to radio > > > Frame reaches target
submit time stamp request to OS
OS reschedules
timestamp reply ^

response frame received < < < Target Responds
submit time stamp request to OS
OS reschedules
ho hum doing something else
timestamp reply ^


^ error in reported transit time ^



Or the other way round........



submit ICMP frame to radio > > > Frame reaches target
submit time stamp request to OS
ho hum doing something else
timestamp reply ^


response frame received < < < Target Responds
submit time stamp request to OS
OS reschedules
timestamp reply ^


^ ^
negative error in reported transit time



At a resolution of tens of microseconds present standard Linux Kernels
are struggling. Linux kernels usually report ping times in tenths
of milliseconds.

Most versions of windows only report ping times in whole milliseconds.

Now with Ingo Molnars shiny new RT Linux patchset maybe you can get
down to this sort of interval reliably.....


Harry
G.W. Haywood
2005-08-10 12:17:10 UTC
Permalink
Hi all,

"The airwaves belong to the public, not the highest bidder," said FCC
Commissioner Jonathan Adelstein.

in

http://news.bbc.co.uk/1/hi/entertainment/music/4135762.stm

Something of which the UK government might take note?

73,
Ged.

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