RB 751 - is it really 2x2 MIMO?
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Airin
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RB 751 - is it really 2x2 MIMO?

by Airin » Fri Sep 28, 2012 2:07 pm

Hi,
in recent months I tested RB751G/RB751U wireless performance. Even with DYI antennas, or with external antenna, or with original PIF antennas.
With better antennas, the router is working fine with great range, BUT:

I can't set it to work in 2x2 MIMO mode. On 20 MHz channel, I get only 65/65 Mbit rates, and on 40 MHz (20 MHz HT Above/Below) I get only 150/150 Mbit rates.

I tried almost everything, different antenna setting (a, b, rxA/txB and txA/rxB) is not solving anything, configuration of the MCS rates also didn't work.

Of course there is chain 0 AND chain 1 enabled, rate selection advanced, security default or WPA2 AES, as mentioned in another topics.

I truly believe that RB751 can't be 2x2 MIMO, because in every antenna mode, it still uses only ONE antenna for TX, and there is no setting to use BOTH antennas for TX (or both for RX).
For 2x2 MIMO, the wireless card has to use TWO antennas, both in rx/tx mode - but RB751 can't :shock:

In my RB433 + R52Hn with two omni antennas and both chains enabled, there is no problem with 130/130 on 20 MHz channel. Also with any TPLink etc., it also runs fine with 130 Mbit rates on 20 MHz channel or 270(300) Mbit on 40 MHz channel.

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TheWiFiGuy
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RB 751 - is it really 2x2 MIMO?

by TheWiFiGuy » Fri Sep 28, 2012 10:41 pm

I get 280mb on 40mhz so yes, its 2x2 mimo. Is your client device?
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Airin
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Re: RB 751 - is it really 2x2 MIMO?

by Airin » Sat Sep 29, 2012 10:51 am

Yes, I tried different notebooks, all of them are running 2x2 MIMO on RX site (so I get 130/65), one of them also on TX site (also 130/130 rates).
With RB433 and R52Hn its ok, with RB 751 only 65/65 rates.

What is your RB751 setup (antenna, MCS rates etc.)?

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TrollMan
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RB 751 - is it really 2x2 MIMO?

by TrollMan » Sat Sep 29, 2012 11:53 am

Export your wireless settings, also make sure you only have aes encryption on and n mode only.

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cbrown
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RB 751 - is it really 2x2 MIMO?

by cbrown » Sat Sep 29, 2012 4:05 pm

Please post /export compact
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janisk
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Re: RB 751 - is it really 2x2 MIMO?

by janisk » Mon Oct 01, 2012 9:31 am

check if you have set 'ht-txchains=0,1' and 'ht-rxchains=0,1'

in CLI you can do that like this:

ros code

/interface wireless <wlan-name> set ht-txchains=0,1 ht-rxchains=0,1


of course there could be some other reaseon, so if this does not help do this, edit out private information:

ros code

/interface wireless export compact

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