[Mikrotik] 802.11N MIMO configuration

Butch Evans butche at butchevans.com
Thu Dec 20 22:11:13 CST 2012


On Fri, 2012-12-21 at 00:56 +0100, Tayeb Meftah wrote:
> i belieuv  i cant do mimo with rb951-2n
> but now i fixed my 72.0mbps issue, i have 150mbit/s now. want to go to 300 
> =)

The only way to get to 300 speed is to set the channel width to 40MHz.
150M is the max speed of 2X2 mimo in 20MHz.  300MHz is only available
with 40MHz.  MCS-15 is 64QAM with 2 spacial streams (2
"chains"/antennas) in 40MHz of spectrum with 400ns SGI (symbol guard
interval).  Same config with the standard 800ns SGI will yield 270 Mbps
coding rate, but PER (packet error rate) should improve significantly,
which of course will generally will result in better throughput when
timing between the two devices are not precisely controlled - ALWAYS
true in my experience.  These settings are all available under
"/interface wireless".  

channel-width - set to 20/40mhz-ht-above or 20/40mhz-ht-below depending
on where you want the extra 20mhz of spectrum to come from.

ht-guard-interval - set to "any" to take advantage of the possibility to
negotiate the short (400ns) SGI.  Set to "long" to disable this shorter
SGI and you will see a max coding rate of 270mbps

ht-rxchains and ht-txchains - both of these should be set to "0,1" if
you want to use 2 chains/antennas and get the possibility of 2x2 mimo
and ht mcs-15 (270/300mbps) - NOTE: be sure you have 2 actual antennas
or this will result in pretty poor performance

Also note that I only mention the details that are specific to the
802.11n configuration.  The other settings mean the same as they do the
rest of the time.

Just a final note:  For those that are interested, I can provide you
with a coupon code worth a 10% discount for the upcoming training in
Salt Lake City if you are a WISPA member.  For NON WISPA members (first,
why are you NOT a member) I will provide a 7% discount code.  For either
code, send me an email or call the number below.  The 7% discount will
NOT be available after 1/1/2013.  See my store at
http://store.wispgear.net for details on the training.  We DO cover the
information above during the class.  These are the types of things that
we do in my training events...stuff you WILL use in the real world!

-- 
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