[Mikrotik] 802.11n vs 802.11a

Matt Larsen - Lists lists at manageisp.com
Tue Apr 24 11:01:07 CDT 2012


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"<lists at manageisp.com>
> To: "Mikrotik discussions"<mikrotik at mail.butchevans.com>
> 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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