understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (2024)

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PackElend

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (2)

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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Sun Aug 22, 2021 11:24 pm

Good evening,
I hope that someone is around who could tell how to interpret the available settings for

  • /interface wireless: channel-width
  • /interface wireless: skip-dfs-channels (10min CAC, all)
  • /caps-man configuration: control-channel-width
  • /caps-man configuration: extension-channel
  • /caps-man configuration: skip-dfs-channels (only on/off)
  • (legacy, properiatry) turbo mode

I have gone through many documentation, blogs, tutorials and forum post.
This is what I have so far, may you can help to fill the missing parts?

  1. turbo mode is an MT proprietary mode but not used anymore although Ubiquiti says, it is part of 802.11a but I cannot find anything more specific. Is there adequate information on this turbo mode available?
    My sources:
    1. 802.11a Turbo/Airgrid a/n 40mhz compatibi*ty | Ubiquiti Community
    2. RouterBOARD Wireless Hacks, MUM 2010 China and RouterBOARDNew and Improved Wireless with Nstreme Version 2 by David Savage, MUN 2011 Austra*a mention a turbo mode in 802.11a/b/g as well, most *kely based on WiFi Atheros Proprietary Turbo ModeInsider - Turbo Mode (wifi-insider.com)
    3. Wireless Tips and Tricks for RouterOS v6, MUM South Africa 2013 says, that 40Mhz Turbo mode is legacy and supported anymore at new 802.11 standards. I guess the mentioned 40Mhz Turbo mode is the same as the turbo mode mentioned in the referenced MUMs above.
    4. 5GHz-turbo - MikroTik and 5ghz vs 5ghz turbo - MikroTik tells me it was used once but not technical details
    5. capsman 2.4Ghz 40Mhz Turbo hAP *te? - MikroTik touches Turbo Mode but does not explain it fully

  2. secondary channel is 80MHz+80MHz to get 160MHz but there is XXXXXXXX, eeeeeeeC and Ceeeeeee as well, so what is the difference?
    I guess that the latter only uses adjacent channels but the former uses two times 80MHz within the allowed frequency range. That means it could be #1_80Mhz: 5170 - 5250 (CH. 42) and #2_80MHz: 5490-5570 (Ch. 106), correct?
    My sources:
    1. 160MHz support for US RB4011 - MikroTik but only talks about the support fi 160MHz wide channel and 80+80MHz.
    2. Secondary Channel - MikroTik says

      supports (non-contigous) 80+80 MHz

      what support my theory but says as well

      Capsman is different beast and secondary-channel setting is used differently.

      Any idea how CAPsMAN uses this setting?
    3. Secondary-channel? - MikroTik, but only a little history on ROS and 80+80MHz
  3. Diversity of Channel Width configuration
    understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (3)
    I am a bit confused about the various options available in CAPsMAN, but the smaller number of options on the actual /interface.
    It is clear to me that CAPsMAN shall support the configuration possible of any MT devices, where /interface list only options supported by the actual hardware.
    To ensure that I get it right the following is correct?
    1. 20/40/80 means

      “Auto 20/40”, the router will use the 40 MHz only if the neighbouring channels are only “free”, otherwise, it will use 20 MHz in order not to damage the neighbours.

      as mentioned in WiFi 20 MHz or 40 MHz: how to choose the bandwidth | BitFeed.com?
    2. Control Channel Widht 40MHz turbo means that the minimum channel width is 40 MHz, devices that use only 20 MHz cannot connect?
    3. Combining Control Channel Widht 40MHz turbo and Extension Channel XXXXXXXX will limit maximum channel width to 160 MHz, it won't throw a misconfiguration error?
      It is all a bit confusing as said here

      The "20/40MHz Ce" setting is confusing, should be "20MHz Ce/40MHz"

    4. If the AP is set on 20/40/80 and can operate at 80 MHz channel width and being connected to modern and legacy devices, only the connection to the legacy devices is downgraded to eg. 20 MHz, the modern devices stay at 80 MHz, as indicated in DD-WRT Forum :: View topic - Dynamic (20/40 MHz) vs Wide HT40 (40 MHz)?
      Unfortunately, the following in 802.11n force 40mhz channel - MikroTik doesn't distinguish between all clients and individual clients:

      When transmissions fail, the transmitter will step down the number of streams, MCS rate, and channel width, ..... until it works, or it totally fails = disconnect.

    5. If a legacy client is connected, what can use only 20 Mhz channels, other c*ents connected to the same AP still can communicate at 40...160 MHz.
      The reason why it can still have a significant impact on the overall throughput are:
      1. actual data (goodput) is only a small portion of the traffic, there is a lot of administrative overhead (TACK: Improving Wireless Transport... is a good read), even for only maintaining a connection in a router, see Is it true that wifi speed slows down when there are several devices connected to it? - Quora.
      2. It consumes more airtime/time per "serve-all-clients" cycle, as per friction fewer data can be transmitted, so the AP spends more time on the legacy device, to avoid that packages get lost.
        If this exceeds a certain limit other devices will suffer, as they cannot make use of the full bandwidth available to them if all devices would operate on the newest standard.
        It is discussed on Super User and Super User
      3. If only legacy devices connected to the AP, reserved channels for e.g. 160 MHz are wasted, as they are not used, even by others AP (unless you implement channel sharing).
  4. how to avoid misconfiguration through CAPsMAN
    Is there any possibility that MT devices fall back to a default configuration if the provisioned configuration is not supported by a device like configuring fixed 40 MHz channel width?
  5. country info interpretation
    why do I have almost the same ranges with the same settings, 5170-5250 vs. 5170-5330 vs. 5250-5330?
    How do I read the lines?
    1. frequency ranges are available depending on the selected band (a, an, ac, b...)?
    2. certain ranges are available if installation is either set to indoor/any or outdoor/any?
    3. 20, 40 etc. tells maximum channel width and dfs is active where dfs is mentioned that is clear understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (4)
    4. how can passive communication work if all devices in a range are passive?

    Code: Select all

    /interface wireless info country-info switzerland ranges: 5730-5790/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(23dBm)/outdoor 5820-5870/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(23dBm)/outdoor 2402-2482/b,g,gn20,gn40(20dBm) 2417-2457/g-turbo(20dBm) 5170-5250/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(23dBm)/passive,indoor 5170-5330/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(20dBm)/dfs,passive,indoor 5250-5330/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(20dBm)/dfs,passive,indoor 5490-5710/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(27dBm)/dfs,passive 5190-5310/a-turbo(20dBm)/dfs 5180-5300/a-turbo(20dBm)/dfs 5520-5680/a-turbo(27dBm)/dfs,passive 5510-5670/a-turbo(27dBm)/dfs,passive 902-927/b,g,g-turbo,gn20,gn40(30dBm)
    .
    .
  6. indoor / outdoor / any / leave empty (defalistt): #13 and #14 hAP AC Lite - Missing a lot of channel - MikroTikIn a nutshell

    Don't use installation "indoor". Use installation "any" if it is indoors. This will include the outdoor allowed frequencies
    ...
    Not entirely correct. "indoor only" mode is for outdoor type devices.

    .
  7. Avoid weather channels as said in #13 hAP AC Lite - Missing a lot of channel - MikroTik is easily said when you are located in a regulated region, such as Canada. It is a different story if you are located in the EU (and non-EU countries in Europe) despite the fact that the ETSI is trying to harmonize standards for Information Communication Technology (ICT) enables systems globally.
    In regard to CH, I find Harmonised frequency ranges (admin.ch) and Swiss National Frequency Allocation Plan and Specific Assignments wherein it is said

    5420 - 5478 MHz: Ground-based weather radars in CH.
    ...
    5600 - 5650 MHz: Preferred band for ground-based weather radar in Europe.

    So, there colistd be weather radars using higher frequencies but you can assume you are safe if you use <=5580/CH.116 and/or >=5700 MHZ/Ch.140 (centre frequency) to avoid The 5GHz “Problem” For Wi-Fi Networks: DFS (wifinigel.blogspot.com) / How does DFS affect mobi*ty? | Wi-Fi Al*ance .
    Good background read: Recommendation on C-Band Meteorological radars design to ensure global and long-term coexistence with 5 GHz RLAN | EUMETNET.

BACKGROUND INFORMATION

[*]Additional Resources:

  1. What are IEEE 802.11 Standards? : 802.11a/b/g/n/ac/ax (signalboosters.com) historical order of 802.11 evolvement plus short comments to each release
  2. List of 5 GHz WiFI channels for EU - MikroTik don't use channels 144-165 only for RD (Short Range Devices) but What are Short Range Devices (SRD) | ETSI, so ok for home APs
  3. dup*cated CAPsMAN documentation: CAPsMAN - RouterOS - MikroTik Documentation and Manual:CAPsMAN - MikroTik Wiki
  4. Understand Wi-Fi 4/5/6/6E (802.11 n/ac/ax) (duckware.com) is a very good summary of current wireless route/AP technology
  5. WLAN Frequency Bands & Channels - CableFree & List of WLAN channels - Wikipedia
  6. What is the MCS Index? | NetBeez
  7. MT's history of 802.11n - MikroTik
  8. What Do 802.11n's Optional Features Mean For You? - SmallNetBuilder - Reslistts from #1
  9. What I’ve learned from nearly three years of enterprise Wi-Fi at home | Ars Technica
  10. Introduction to 802.11ax High-Efficiency Wireless - NI technical details well explained
  11. Bandwidth and Throughput in Networking: Guide and Tools - DNSstuff
  12. 802.11ac Migration - Part 2: What Nobody's Tel*ng You About 80MHz and 160MHz Channel Bonding (7signal.com) best channel selection depending on channel width
  13. When to Use 20mhz vs 40mhz vs 80mhz (quickstart.com)
  14. tries to explain 20/40 dynamic rate vs. fixed 40 MHz rate but does not take into account being "neighbour friendly" un*ke in Sholistd I enable/disable 20/40 MHz Coexistence? : orbi (reddit.com)
  15. 4. 802.11 Framing in Detail - 802.11 Wireless Networks: The Definitive Guide, 2nd Edition [Book] (oreilly.com)
  16. 802.11 Frame Types and Formats – How I WI-FI (howiwifi.com)
  17. QCA wireless settings - DD-WRT Wiki / Basic Wireless Settings - DD-WRT Wiki good explanation on channel topics
  18. 5 GHz Channel Planning
    1. Channel Planning Best Practices for Better Wi-Fi - Ekahau
    2. Wireless eC, Ce or XX - MikroTik
    3. Channel overlap 802.11ac - MikroTik
    4. List of WLAN channels - Wikipedia
    5. WLAN Frequency Bands & Channels - CableFree
    6. List of 5 GHz WiFI channels for EU - MikroTik
    7. Channelization & OBSS Impact | Dumping ground for wireless, route, switch stuff. (mikealbano.com)
      http://www.mikealbano.com/2015/10/chann ... mpact.html
    8. Channelization & OBSS Impact | Dumping ground for wireless, route, switch stuff. (mikealbano.com)

[/*]

Last edited by PackElend on Mon Aug 23, 2021 12:09 pm, edited 4 times in total.

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bpwl

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (6)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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  • #2

Mon Aug 23, 2021 1:38 am

Some more reading on the 20/40 channel widths for 802.11n (remember 802.11ac uses different techniques)

Short note on the "40 MHz intolerant bit" : https://mentor.ieee.org/802.11/dcn/08/1 ... torial.ppt

In depth Aruba whitepaper on 802.11n and 20/40 MHz: https://www.arubanetworks.com/pdf/techn ... 02.11n.pdf
(recommended reading for the 20/40MHz )

And also the whitepaper on 802.11ac might be useful: https://www.arubanetworks.com/pdf/techn ... nDepth.pdf

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PackElend

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (8)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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  • #3

Mon Aug 23, 2021 8:20 am

Some more reading on the 20/40 channel widths for 802.11n

thx for this quick response will go through it (and restructure the OP as it looks a bit messy)

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bpwl

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (10)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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  • #4

Mon Aug 23, 2021 12:05 pm

certain ranges are available if installation is either set to indoor/any or outdoor/any?
...
/interface wireless info country-info switzerland
ranges: 5730-5790/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(23dBm)/outdoor
5820-5870/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(23dBm)/outdoor

Well this leads to a very specific MT interpretation and implementation.
There is a technical (interference, priority usage) reason to limit some frequencies to indoor use only. (to avoid outdoor interference with emergency services).
I see no technical reason and no mentioning in the spectrum regulations to limit certain frequencies to outdoor use only.

There is the ("", "indoor" , "outdoor") possibility in the country table, what should work as follows:
indoors: allow ("", "indoor" , "outdoor") (or just: use whatever is specified) (MT setting : installation=any)
outdoors; allow ("", "outdoor") (or just : don't use freq limited to indoor only) (MT setting : installation=outdoor)

Either the MT logic to select the freq per installation is inaccurate for indoor, or the "outdoor" specification has been added later in the table without considering the logic used.
"Outdoor" is not in the table for all countries.

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PackElend

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (12)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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  • #5

Mon Aug 23, 2021 12:13 pm

Well this leads to a very specific MT interpretation and implementation.

and I even forgot something yesterday evening (got quite late)
It is actually 5170-5250 vs. 5170-5330 vs. 5250-5330?
In particular, the third line below is not necessary as it is covered by the second line.
No clue why it is listed

Code: Select all

/interface wireless info country-info switzerland ranges: ... 5170-5250/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(23dBm)/passive,indoor 5170-5330/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(20dBm)/dfs,passive,indoor 5250-5330/a,an20,an40,ac20,ac40,ac80,ac160,ac80+80(20dBm)/dfs,passive,indoor

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bpwl

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (14)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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Mon Aug 23, 2021 12:24 pm

No clue indeed. Or is it the second line that is added as extra, just to allow dfs on 5170-5250 limited to 20dBm??????. Why would one do that, if it is available for 23 dBm without dfs?
Or is it to allow the DFS logic to jump to the non-DFS freq when radar is detected? Then indeed line 3 is redundant.

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PackElend

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (16)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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Mon Aug 23, 2021 12:39 pm

No clue indeed. Or is it the second line that is added as extra, just to allow dfs on 5170-5250 limited to 20dBm??????. Why would one do that, if it is available for 23 dBm without dfs?
Or is it to allow the DFS logic to jump to the non-DFS freq when radar is detected? Then indeed line 3 is redundant.

I will put it on top of my open ticket in regard to DFS and scan list + auto frequency - MikroTik

What do you think about my points 3.4 and 3.5?

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bpwl

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (18)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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Mon Aug 23, 2021 5:04 pm

3.4

Well as explained in the white paper on 802.11n , and as the Mikrotik registration table demonstrates, the AP has to maintain the settings per client device. The interface rate is per client, the global communication from the AP such as beacons are sent at the basic-rate. So each client gets it's own step-up and step-down actions. It can be followed in the registration table.
(Just a combined DUDE Routerinfo snapshot as example: WLAN1= 2.4 GHz /802.11n /20 MHz, WLAN2= 5 GHz /802.11ac/ 20MHz Ce. Basic rate is at 12Mbps, but initial request is always at 6 Mbps, last 2 are nv2 PtMP)

Klembord-2.jpg

.
3.5
.
On the other hand, if the channel is very busy, lets say with 2 talkers, and no air-time fairness feature (like in MT), then the actual data rate for BOTH is somewhat slower than the slowest connection. Each get the same chances for transmission (statistical with random numbers), but the slower will transmit for a much longer time.

EDIT: air-time fairness as far as I understand the implementation only works for the AP where it is implemented. The traffic obstruction is per channel by every transmitter. Just any transmitter can consume most of the air-time if it is a busy slow transmitter.

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PackElend

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (20)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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Tue Aug 24, 2021 10:48 pm

Well as explained in the white paper on 802.11n , and as the Mikrotik registration table demonstrates, the AP has to maintain the settings per client device.

thx That's what I thought too, but I have to read papers like this over and over again until I'm sure I've drawn the right conclusions. This time I thought, I could take a shortcut

On the other hand, if the channel is very busy, lets say with 2 talkers, and no air-time fairness feature (like in MT), then the actual data rate for BOTH is somewhat slower than the slowest connection. Each get the same chances for transmission (statistical with random numbers), but the slower will transmit for a much longer time.

EDIT: air-time fairness as far as I understand the implementation only works for the AP where it is implemented. The traffic obstruction is per channel by every transmitter. Just any transmitter can consume most of the air-time if it is a busy slow transmitter.

thx for sharing understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (21)
Once I found a good and easy to understand description that mentioned data-buffer and CPU-clock-time, but I cannot find it anymore.
It was somehow like this: AP ensures that the buffers does not oveload but the slow devices cannot take that much data at the same time as the fast ones, so more time is needed to offload data from the buffer to the device to avoid that the buffer is overloaded by the data of the slow devices. The remaining data can still be offloaded to the fast ones but their throughput would be reduced as the get less time as the all the actions have to happen in the same period of time, always, regardless the amount of devices etc.
I hope I find this again.
Moreover I found
https://community.tp-link.com/us/home/s ... detail/203
https://documentation.meraki.com/MR/WiF ... ness_(ATF)
what goes into the same direction

p.s. I added the redundant range information to my open support ticket

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bpwl

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understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings (23)

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Re: understanding Channel-Width options and limitations due to country registrations plus interface vs CAPsMAN settings

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Tue Aug 24, 2021 11:56 pm

Waw, those articles of TP-link and Meraki, make my head spin. TP-link trying to explain air-time fairness to the man in the street, and Meraki, more technical but focusing on the queueing techniques to explain the limited scope of air-time fairness.

1. MT to my knowledge uses NO air-time fairness. None at all.
2. The action, as confirmed by TP-link and Meraki, is limited to the transmission of the one AP involved in air-time fairness. Nevertheless air-time is consumed by everyone in the channel. The used air-time impacts everyone in the channel, all AP's and all clients. Air-time fairness in the AP can only see the 'unfair' use of air-time by others, but cannot take a single action on that.
3. Even upstream traffic to the air-time fairness driven AP, is out of control. (It's like limiting incoming internet traffic .... well, you can delay the ACK if it is TCP)
4. Slow and fast have an impact, independent of the reason for the slowness (older technology, further away, etc etc)
5. Meraki makes some strange statements: "However, because of rate control, high-performance clients that support high bitrates like those in 802.11n and AC may fall into the blue or orange areas under some circ*mstances." . The interface rate (and CCQ /retransmits) is indeed important, why you have a low rate doesn't matter.
6. The EDCA of Meraki is aka WMM. Be aware that WMM in MT is sleeping. You need mangle rules to set priorities in WMM, and the default disabled a-MPDU for all except the low priority ("best effort") may have a negative impact on the available air-time due to the much larger overhead for the small frames. It's set to minimize the response time, but that way greatly reduces the throughput. Each time you get the chance to transmit you only send a small MPDU (=A-MSDU size) frame, instead of the larger A-MPDU.
7 I do personally suspect other AP brands and assertive client devices, or operators of neighboring networks, of abusing the reduced WMM wait-timers just to prioritize their regular traffic in the channel.

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