[MLB-WIRELESS] longest link?

Richard Van Orsouw Richard.Van.Orsouw at optus.com.au
Wed Oct 29 12:00:51 EST 2003


Guys, just add some comments some testing Peter B and myself did between
nodeGDW & GUR.
802.11g testing over a 36km link that we have running on 802.11b. It seems
that 802.11g (ODFM) just doesn't work over long distance links. Even tried
"Super G" but to no avail. Using Dlink DWL-G520 card linked to a AP2000 11.g
compatible. With 11.b we can get up to 80KB/s, but using 11.g, we can "see"
the AP at the other end, but will not associate. Both ends were rx'ing SNR
values of 20dB.
Link speeds b/w nodeGDW and GHO at a distance of 52km is about 10KB/s worth
of ftp traffic. When I ftp off another node using GHO (nodeFOA) I achieve
about 7KB/s (this is a round trip distance of about 80km). I've had to
fragment my ip traffic below 512 bytes because of the noisy environment at
GHO's end ( if you do a man iwconfig under frag it also gives an
explanation).

> ----------
> From: 	paul van den bergen
> Sent: 	Tuesday, 28 October 2003 15:39
> To: 	melbwireless at wireless.org.au
> Subject: 	Re: [MLB-WIRELESS] longest link?
> 
> On Tue, 28 Oct 2003 03:11 pm, vk3jma at net2000.com.au wrote:
> > Quoting Craig Mead <craig at australianwireless.org>:
> > > Yes, C. I'd like to lock in C thanks Eddie. 103km.
> >
> > Would you like to ping a friend?
> 
> :-)
> 
> ROC of the earth tends to cut into the freznel zone so your end points
> need to 
> be WAY up in the air for these sort of links... On flat ground with about
> 15 
> foot ground clearance (antenna height), 5-8km would be about the limit... 
> (IIRC)
> 
> ofcourse, if it is straight up you can go forever[1][2]... or at least
> until 
> the ethernet timeout limits are approached.
> 
> [1] where forever is a mighty long way.
> [2] given a sufficiently high gain antenna. say, several times the
> diameter of 
> the solar system....
> 
> -- 
> Dr Paul van den Bergen
> Centre for Advanced Internet Architectures
> caia.swin.edu.au
> pvandenbergen at swin.edu.au
> IM:bulwynkl2002
> "And some run up hill and down dale, knapping the chucky stones 
> to pieces wi' hammers, like so many road makers run daft. 
> They say it is to see how the world was made."
> Sir Walter Scott, St. Ronan's Well 1824 
> 
> 
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