Community discussions

MikroTik App
 
User avatar
rfc1149
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 77
Joined: Fri May 15, 2020 4:26 am
Location: England

Bandwidth rate representations between hAP AC and hAP AC2

Sat Jan 22, 2022 3:55 pm

For the 2.4GHz side of things only:
Between the hAP AC (Triple-chain) and the hAP AC2 (Dual-chain),
both of these devices support 40MHz operation at 2.4GHz.

1S = 1 stream (20MHz operation)
2S = 2 streams (40MHz operation)
SGI = Short Guard Interval

I've observed its reported differently between these two devices.
On the hAP AC, 40MHz operation at the highest rate shows up as 144.4Mbps-20MHz/2S/SGI
ac.png
On the hAP AC2, 40MHz operation at the highest rate shows up as 300Mbps-40MHz/2S/SGI
ac2.png
There is certainly no 80MHz operation on 2.4GHz which is what the AC2 implies if the AC's readings are to be taken similarly.
I know they use different wireless chipsets (Atheros AR9300 vs Qualcomm IPQ4019) but it's still confusing.

In summary, my question is this:
Is there a major hardware or throughput difference I'm failing to acknowledge or are these just same same but different? :D
You do not have the required permissions to view the files attached to this post.
 
User avatar
rfc1149
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 77
Joined: Fri May 15, 2020 4:26 am
Location: England

Re: Bandwidth rate representations between hAP AC and hAP AC2

Tue Jan 25, 2022 9:06 pm

No comment on this? :shock:
 
User avatar
chechito
Forum Guru
Forum Guru
Posts: 2990
Joined: Sun Aug 24, 2014 3:14 am
Location: Bogota Colombia
Contact:

Re: Bandwidth rate representations between hAP AC and hAP AC2

Tue Jan 25, 2022 9:54 pm

which version of RouterOS running on this devices??

Routerboot Updated?
 
User avatar
chechito
Forum Guru
Forum Guru
Posts: 2990
Joined: Sun Aug 24, 2014 3:14 am
Location: Bogota Colombia
Contact:

Re: Bandwidth rate representations between hAP AC and hAP AC2

Tue Jan 25, 2022 10:00 pm

144.4Mbps-20Mhz/2S/SGI looks correct

300mbps requires 40mhz thats showing on hap ac2

maybe a discrepancy between client device and ap, or radio config

normally the number of chains does not alter the form data-rate is shown, i have not seen differences on audience device it has 4x4 radio and show data-rates without problem
 
User avatar
bpwl
Forum Guru
Forum Guru
Posts: 2983
Joined: Mon Apr 08, 2019 1:16 am

Re: Bandwidth rate representations between hAP AC and hAP AC2  [SOLVED]

Tue Jan 25, 2022 10:07 pm

144.4Mbps-20MHz/2S/SGI
Take https://mcsindex.com/ as reference document: HT = 802.11n , VHT= 802.11ac, (HE =802.11 ax)

The above interface rate is:
- HT MCS15 (or 2x VHT MCS07) encoding, rate is 144.4Mbps
- bandwidth is 20 MHz (not 40MHz)
- 2S= dual stream (two independent data streams, uses 2 antenna)
- SGI = short guard interval 0.4µs
.
300Mbps-40MHz/2S/SGI
- HT MCS15 encoding, rate is 300Mbps
- bandwidth is 40 MHz
- 2S dual stream
- SGI short guard
.
243Mbps-40MHz/2S
is HT MCS14 (or 2x VHT MCS06) , interface rate 243Mbps, bandwidth 40MHz, dual stream, long guard

Some rules:
- bandwidth 20/40/80 is negotiated, but mostly set by AP (client must be able to execute, and normally keeps all options open, but may not have 80MHz)
- MCS index is dynamically changed, independent for both directions. Bad transmissions (>HW retry) makes the interface step down in MCS , good transmissions trigger step ups
-dual stream: if both devices support it, and if the radio can maintain it. Sometimes 2S is dropped as not maintainable. Client and AP # of antenna defines max # streams.
So: hAP AC is 3S, but except for iMAC not many clients have 3S. e.g.: Tablet will connect as 2S
So: laptop is mostly 2S, tablet 2S, smartphone 1S. Smartphone will always connect as 1S to hAP ac and hAP ac2, (even to the 4x4 Audience).
- short guard: as set in AP. short/long/auto. With auto it depends on signal quality

In 802.11ac in 40MHZ/2S/SGI highest MCS09, interface rate is 400Mbps
In 802.11ac in 80MHz/2S/SGI highest MCS09 , interface rate is 866,7Mbps
In 802.11ac in 80MHz/3S/SGI highest MCS09 , interface rate is 1300Mbps
Effective user datarate is much lower. The overhead becomes more important with higher interface rates. A lot depends on the driver and the aggregation used. viewtopic.php?t=174294#p852582
On MT 400Mbps interface rate yields 260Mbps, 866Mbps drops to 360Mbps. (other brands and wifiwave2 drivers will go to 500Mbps+)
 
User avatar
rfc1149
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 77
Joined: Fri May 15, 2020 4:26 am
Location: England

Re: Bandwidth rate representations between hAP AC and hAP AC2

Tue Jan 25, 2022 10:44 pm

which version of RouterOS running on this devices??
Both devices running ROS 7.1.1
 
User avatar
rfc1149
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 77
Joined: Fri May 15, 2020 4:26 am
Location: England

Re: Bandwidth rate representations between hAP AC and hAP AC2

Tue Jan 25, 2022 10:54 pm

-dual stream: if both devices support it, and if the radio can maintain it. Sometimes 2S is dropped as not maintainable. Client and AP # of antenna defines max # streams.
So: hAP AC is 3S, but except for iMAC not many clients have 3S. e.g.: Tablet will connect as 2S
First of all, thank you so much for going into the details. I understand this a LOT better because of your input.

This is getting stranger for me then. My hAP AC is not negotiating 40MHz despite all clients supporting that mode of operation.
I just tested with an AX1650 and it definitely negotiated 40MHz with it but the others stick to 20MHz operation like 40MHz is the plague.
It doesn't make sense but okay. See below, the AX1650 is the 3rd on the list and the last for the 2.4GHz interface.
throughput-ax1650.png
You do not have the required permissions to view the files attached to this post.
 
User avatar
bpwl
Forum Guru
Forum Guru
Posts: 2983
Joined: Mon Apr 08, 2019 1:16 am

Re: Bandwidth rate representations between hAP AC and hAP AC2

Wed Jan 26, 2022 12:05 am

OK. Looking for other limitations

What are the freq set for 2.4GHz ? Mikrotik uses the notation of Control channel and extension channel. Other brands use the midfreq of the 40 MHz
Possible non-overlapping settings for 20 MHz are channel 1,6 and 11, because channels are 5 MHz wide only.
And with b-protocol (801.11b/g/n) enabled channel width is even 22.5MHz. (we usually disable b-protocol today)
Mikrotik notation for 40 MHz is "20MHz/Ce/eC or XX"
With Ce the control channel and freq if for the lowest value
With eC the control channel and freq is for the highest value
With XX it's undefined.
So the 40 MHz wide 2412 (channel1) Ce is possible. This would take 8 channels wide 0-1-2-3-4-5-6-7
2437 (channel6) would always overlap.
Even 2462 (channel11) eC would overlap as it takes 5-6-7-8-9-10-11-12.
There is only room for 1 40MHz channel in 2.4GHz. (In theory in Europe we could use 2 full 40MHz channels 1Ce and 13eC)
Some devices that see 40MHz send a "40MHz intolerant" message, and all devices must reduce 40 MHz channels to 20 MHz.


It is not clear what happened in your case. Wrongly assigned freq as cause or receiving the "40 MHz intolerant bit", or just poor signal quality.
(In MCS stepping down the step from 2S to 1S or from 40MHz to 20MHz is also taken). Fallback to 20MHz happens also when channels overlap.
The MT starts rather slowly if there is not much traffic, starting from 6Mbps-20MHz, and stepping up.
2.4GHz is 802.11n as highest rate and that is HT MCS only
There is no 80MHz in HT MCS.
 
User avatar
rfc1149
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 77
Joined: Fri May 15, 2020 4:26 am
Location: England

Re: Bandwidth rate representations between hAP AC and hAP AC2

Wed Jan 26, 2022 12:49 am

OK. Looking for other limitations

I'll keep looking I guess, but the same behaviour continues. AX1650 registers as 40MHz, everything else maintains 20MHz.
In all likelihood, it might be the hardware but it seems highly unlikely since I know from specs that other devices support 40MHz operation.
Even if it's 1x1, they support it. Eh, wireless clients are weird.

Who is online

Users browsing this forum: vkp and 26 guests