hAP ax S - 3x3 MIMO activation

Hardware MikroTik hardware general
1

Dear All,

I try to benefit from the 3x3 MIMO (triple chain) feature of my hAP ax S box, using 5G AX mode - as specified officially.

With default settings, and also with Wifi Configuration set to “Chains” and “Chains Tx” to 0, 1, 2 looks for me stuck on 2x2 MIMO. I am checking the effective wifi parameters on my mobile (Samsung S24), with WiFiman app.
( my old Tp-Link / Openwrt routers are capable for 3x3 MIMO without any further config trick, by default)

Is there any trick to force hAP ax S to go for 3x3 MIMO mode?

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There is no trick. Just use the defaults, meaning don't mess with chains settings.

S24 is capable of 3 spatial streams? I can't find it in the specs of s24. Have you verified it by using the good OpenWrt/TP-Link?

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tx-chains (list of integer 0..7) Radio chains to use for transmitting signals. Defaults to all chains available to the corresponding radio hardware.

S24 (Exynos or Snapdragon) isn't capable of nothing more than 2x2. Even the S24 Ultra running FastConnect 7800 is still 2x2.
TBH, I’m not aware of any mobile phone being capable of 3x3/ 4x4.

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Leaving it as default and therefore not configured shouldn't it automatically use 3 chains?
How can I check from terminal?

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/interface/wifi/radio/print detail proplist=interface,radio-mac,rx-chains,tx-chains
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[user@MikroTik] > /interface/wifi/radio/print detail proplist=interface,radio-mac,rx-chains,tx-chains
Flags: L - LOCAL 
 0 L interface=wifi1 radio-mac=04:F4:1C:CD:8F:54 rx-chains=0,1 tx-chains=0,1 

 1 L interface=wifi2 radio-mac=04:F4:1C:CD:8F:55 rx-chains=0,1,2 tx-chains=0,1,2 

 2   interface=cap-wifi1 radio-mac=04:F4:1C:CD:8F:8C rx-chains=0,1 tx-chains=0,1 

 3   interface=cap-wifi2 radio-mac=04:F4:1C:CD:8F:8D rx-chains=0,1,2 tx-chains=0,1,2

I confirm, without configuration it uses 3 chains.

@cyrq Thanks!

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wifi/radio/print shows radio capabilities. not effective configuration.

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Hm, you’re probably right.
There are props like current-country, current-channels etc, but there’s nothing that explicitly says that the current config is running x amount of chains. I have no clue how validate that from ROS.

Fastest way to do that (client side) would be:

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AFAIK ROS always runs number of configured chains. However, "excess" chains are only used for communication with stations which can utilize those chains. As already mentioned, only a few station devices can do more than 2x2 MIMO ... and for the rest there's minor improvement when AP supports "excess" chains (mainly due to spatial Rx diversity, I'm not sure it Tx benefits as well).

I'm not even sure (can't test as I don't have any station supporting more than 2x2) if stations can actually do 3x3 MIMO if they have 4x4 MIMO support (I wouldn't be much surprised if they didn't if developers considered 3x3 or any odd X odd MIMO mode to be odd).

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Thanks for your answers. i also tried to investigate about my device capabilities. Samsung S24, and also the Intel AX201 adapter in my notebook can only handle 2x2 streams, so most probably not too much benefit from 3x3 on a single device.
Potential benefit from 3x3 in case there is a 2x2 client + 1x1 client connecting simultaneously can draw the full throughput of the AP?

WiFiman app (on my S24): i assume this app show only the hw capabilities of an AP / SSID . I see APs with MIMO 3x3, and also MIMO 4x4 at my workplace. Now understood my device alone can not use 4x4, but the AP is capable for that.
hAP ax S shown max 2x2 (this is the default), in case in configuration chains are manually reduced, it shows 1x1. This means the configuration setting is effective somehow, but by default it doesn’t provide 3x3.

WinFi 3.0 Pro: installed it, provide very detailed information. Unfortunately i have not found Stream / MIMO info yet.

I am wondering what is the real potential benefit of 3x3 MIMO advertised AP - if at all. (may be for me nothing…)

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I am a user of analiti for Android. It shows is it in the network info tab as SU-MIMO/MU-MIMO fields. the raw information for that spatial stream capabilites are contained in the "HT Capabilities" IE (look for TX Max Spatial Stream Supported or RX Max Spatial Stream Supported - see https://mrncciew.com/2014/10/19/cwap-ht-capabilities-ie/). This is broadcasted by the AP.

So yes, you can actually "see" the capabilities as a client. If your AP broadcasts "2 spatial" then this can have 2 explanations:

  • wrong HT capabilities sent by AP
  • AP actually really uses only 2 spatial streams

I would collect evidence and contact MikroTik support if it is actually reported as 2x2 and device misconfiguration can be ruled out.

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Yup ... if both AP and stations support MU-MIMO. If I'm not much mistaken, hAP ax S should support it. But all stations that might share airtime (by using different AP chains) also have to support MU-MIMO. And IIRC support for MU-MIMO is not mandatory in WiFi6 (and I don't know if this changed in WiFi7).
Additionally this really only starts to make any difference in a congested AP ...

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There was this bug some years ago.

AP announced Country Latvia, regardless of your actual country setting in wifi configuration.

Maybe 2 spatial is hard coded? :upside_down_face:

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WinFi 3.0 also confirms my suspect. Spatial Stream = 2 . with default config. I can reduce it manually to 1 with “Chains: 0” config.

3 is not possible even with manual “Chains: 0,1,2” configuration, though the config can be applied to the AP.
I reckon this is not a significant bottleneck of the performance, but it is interesting that the vendor has not recognized this “issue” so far. (though the 3x3 MIMO is still a selling point and comparative advantage of hAP ax S)

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Do you check 5ghz bssid? 2ghz is 2 chains, 5ghz is 3.

Btw, just found this in changelog.

What's new in 7.22.2 (2026-Apr-22 11:03):

*) wifi-mediatek - fixed HE capabilities IE on 2GHz band;

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Yes, 5 Ghz was checked. 2 chains max.
For later reference: ROS version 7.22.3 (current stable)
Hope Mikrotik recognizes this topic, and will fix it.

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hAP ax S is a pretty recent device and is running a recent wireless driver pack (wifi-mediatek). Many of experienced forum members would consider that device a "beta" device and thus it would make much sense to run "beta" (or development) version of ROS on it.

If the issue with having only 2 chains active persists with beta/RC version of ROS, then by all means report it in appropriate beta/RC thread ... because there's a better chance for MT devs to see the problem. Another possibility would be to open a support ticket (and provide supout.rif file).