All of the 802.11n paths that had problems tended to have one chain out
of four (tx/rx on both polarities) that was much worse than the
others. This lead to the big variances in CCQ, is what I have been
told. I don't have a good technical explanation for it other than
802.11a modulation ended up making the links much more solid and got our
CCQs back up to 90%+.
We do still have one 65+ mile shot using the 802.11n modulations and it
appears to be working fine, but that link is on 4' Radiowaves dishes,
plenty of clearance along the path and has -65 signals on all of the
chains. It is also a backup link at this point and not running a lot
of traffic so it doesn't see the same kind of load that my other links
are getting. Before we figured this problem out, we were seeing great
results on testing on the long 802.11n links but they would start
getting real flaky when we put heavy loads on them.
Matt Larsen
vistabeam.com
On 4/24/2012 9:43 AM, Mike Hammett wrote:
Wouldn't multipath be *better* for N?
-----
Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com
----- Original Message -----
From: "Matt Larsen - Lists"<[email protected]>
To: "Mikrotik discussions"<[email protected]>
Sent: Tuesday, April 24, 2012 10:25:15 AM
Subject: [Mikrotik] 802.11n vs 802.11a
We are finding out that 802.11n links do some weird things when they get
over 25 miles.They will run 70meg and then drop to 5 even though the
signals and other RF conditions have not changed.As you can imagine,
this makes latency go all over the place.We found that by setting them
to 802.11a mode, we can get them to carry 30meg consistently with a much
narrower range of latency results. This is reflected in much higher
CCQ% on the 802.11a links vs the 802.11n links. Also seems like
Nstreme (not NV2) with a framer policy of 'none' and CSMA disabled is
the most stable setup.
Just thought some folks might find this useful. Butch has said that
some of our 802.11n problems may have had to do with multipath. YMMV.
Matt Larsen
vistabeam.com
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