Hello, on our site we use RB433AH with R52Hn and UBNT MIMO Sector 16dbi/120deg. Both chains enabled, also 2x2 MIMO.
Clients are located 100-800 m from the AP and have UBNT devices (NanobridgeM5, NanostationM5). Signal for all clients is clear, from -45 to -55 dB on both sides. It´s linked together on 130/130 mbps (see picture), but clients get real TCP troughput only 16-22 mbps. With 802.11a (r52 as AP card and only one chain) it was the same speed...
Channel width is 20 MHz.

Where could be the problem?

PS: I forgot - the RB is running latest v5.0rc10, parameters on the card set like http://wiki.mikrotik.com/wiki/802.11n_Setup_Guide

You havn't applied "HT extention channel: above control" under HT.

Do this for both AP and client

RGDS

You havn't applied "HT extention channel: above control" under HT.

Do this for both AP and client

RGDS

Yes, I haven´t, but I dont want 40 MHz channel (extension channel makes 40 MHz bandwidth).
But also with 20 MHz the TCP troughput should be cca. 40 Mbps, not 22/16...

Are you running WDS? Mikrotik WDS with 11n is slow.
WDS only works good with nstreame or nv2 which can't be used toghther with UBNT.

I've also seen some performance problems in rc10 that wasn't in rc9

No, WDS is disabled.

The performance problems with 802.11n MIMO were also in v4.11, so I upgraded to the latest version (thinking it would be better with MIMO). But no difference at all.

When I have UBNT to UBNT on 20 MHz, it is running 30-40 mbps without AirMax and 50 (sometimes 60) mbps with AirMax enabled.
But on my AP I want to use Mikrotik radios only, because UBNT makes more noise in lower freq., such as FM CCIR 87,5-108 MHz.

I am curious to the answer of your question as well.

please contact support@mikrotik.com with the support output file when you are doing those TCP throughput tests. How do you do those tests? when you were testing the speed, you were the only one that was transmitting a lot? What speed do you have for the UDP test?

I did those tests with speedtest mini running on our main server, also it was real traffic. UBNT itself has speed test (it can measure speed to another UBNT in the network), but its measuring UDP only. Although, this UDP speed measured with UBNT is high, about 40-50 Mbps one way, so I am curious, why TCP is so low - I expected at least 30-35 Mbps with 2x2 MIMO at 20 MHz...

The RB 433AH is connected to the main network with 40 MHz nstreme link with stable troughput of about 50 Mbps one way (real traffic with speedtest mini). With bandwidth test in winbox can I measure about 52 Mbps TCP and 55 Mbps UDP.

The tests were made when there was no other traffic at time.

Could be the problem that 433AH is not able to achieve higher speed when the data flow from one wireless card to another or something like that? I am also running VLAN on this interface, isnt it slowing down the performance? I add my settings for the R52Hn.

Hello Airin!

These are the first things that come to mind on a link like this.

When diagnosing connection problems...it's usually helpful to start close in then work your way out.

So use the BTest tool on a PC to do a test through the client radio just to the AP. Once you have that setup...you can start making adjustments to the client config and the AP config and see what difference they make in throughput and latency.

Right off the bat I would suggest increasing the HW retries to 15....this may improve performance....if it does...then start decreasing the HW retries until you see a decrease in performance.

Try the enabling Adaptive Noise Immunity on the AP...again....use the BTest tool to see if it makes a difference.

On the UBNT side...make changes to the different settings and do the same tests with the btest tool.

Hope that helps.