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Cablenut9
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cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 12:42 am

I set up my new cAP ac with cAPsMAN and even though it can receive with 2 chains from this one device, it can't receive with 2, but rather 1. For this reason, I can't get above 300Mbps download when doing a speedtest with my device, yet it's easy to get 500+ upload. Is there a fix? There's no setting that's disabling the second chain, as it actually shows 2 when first connecting and with a lower PHY speed.
 
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anav
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 3:33 am

Ahh I see you come from the planet, EASILY FOOLED.

Lets talk facts, the capac is rated loosely as a 1200speed wifi device.
Breaking it down 300 2gig and 867 5gig.

You must come from the Country called ADVERTISING SUCKER

Those speeds are two way speeds not one way and finally wifi suffers losses.
So to get the realistic throughput just use the MTUNA certification rule of 1/3
Meaning on your 2gig expect roughly one way speeds of 100Mbps
On 5gig expect roughly one way speeds of 289Mbps and if you do better than that you have less interference than most and probably LOS connectivity.

Did you say you were from the Town called DUMBFOUNDED?
 
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anav
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 3:36 am

One of my capacs, Check out on the wifi tab advanced mode (HT) tab!
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Cablenut9
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 3:53 am

I had the expectation that the cAP would give 2 chains with 802.11ac, yielding a PHY of 866Mbps and throughput of 500, but I can get only 1 chain DOWNLOAD, and upload gets 2. In other words, I get 250Mbps download and 500Mbps upload using a known good 802.11ac client that supports 160MHz DFS 2x2 APs, which the cAP is a far cry from. My dinosaur "draft-ac" router way back from 2013 has 2 chains BOTH on download and upload and gets close to 500 with BOTH download and upload, so this shouldn't happen.
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anav
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 5:26 am

You dont have a clue of what you are talking about.
Moving on to help others.
 
Cablenut9
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 5:48 am

You dont have a clue of what you are talking about.
Moving on to help others.
This kind of ad hominem attack is the reason why so many people don't want to mess with Mikrotik stuff.
 
erlinden
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 10:06 am

Can you please share your configuration?
/caps-man export

I'm sure the cAP ac is capable of two streams (up and down), might be a configuration thing.

In regards to your expectations...500Mbps is a bit enthousiastic.
 
Cablenut9
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 4:18 pm

Here's an /export:
/caps-man datapath
add client-to-client-forwarding=yes local-forwarding=yes name="turbo wifi"
/caps-man security
add authentication-types=wpa2-psk name="turbo wifi"
/caps-man configuration
add channel.band=5ghz-n/ac channel.control-channel-width=20mhz channel.extension-channel=eeCe channel.frequency=5300 country="united states" datapath="turbo wifi" datapath.local-forwarding=yes mode=ap name="5g 1" security="turbo wifi" ssid="turbo wifi"
add channel.band=2ghz-onlyn channel.control-channel-width=20mhz channel.extension-channel=disabled channel.frequency=2437 datapath="turbo wifi" datapath.local-forwarding=yes name="2g 1" security="turbo wifi" ssid="turbo wifi"
/caps-man interface
add channel.extension-channel=disabled configuration="2g 1" configuration.rx-chains=0,1 configuration.tx-chains=0,1 disabled=no l2mtu=1600 mac-address=08:55:31:B0:C9:48 master-interface=none name=cap1 radio-mac=08:55:31:B0:C9:48 radio-name=085531B0C948
add configuration="5g 1" configuration.tx-chains=0,1 disabled=no l2mtu=1600 mac-address=08:55:31:B0:C9:49 master-interface=none name=cap2 radio-mac=08:55:31:B0:C9:49 radio-name=085531B0C949
/caps-man manager
set enabled=yes
/caps-man provisioning
add action=create-dynamic-enabled master-configuration="5g 1"
 
erlinden
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 4:51 pm

What version Routerboard and firmware are you running?
Haven't seen the L2MTU size set before (except in very old configuration examples), do you need it? I prefer to use as much default as possible, leave everything (i.e. L2MTU) empty, etc
 
Cablenut9
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 5:01 pm

I'm using a recent cAP ac with 6.49beta11, and a hEX S also with 6.49beta11.
 
biomesh
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 5:04 pm

Generally you don't need to set any TX or RX chains in capsman. The default device values will use both chains for TX and RX. I see that it looks like you have modified the cap interfaces (changing the RX and TX chains). The 5G one is missing the RX chain config.

I would not even mess with this though.

I would set your security profile for aes-ccm only. I would also delete your capsman interfaces and re-provision them. For country you should use "united states3" vs "united states" and not use a DFS channel for reliable performance and results.
 
erlinden
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 5:09 pm

I'm using a recent cAP ac with 6.49beta11, and a hEX S also with 6.49beta11.
Currently I'm running LTS (6.47.9) which works best for me. Why are you running beta? Could be beta related (though I have no clue).

Great addition, biomesh. I alreay wondered why there was a /caps-man interface section in the export.

Why the advice not to use DFS channels? Is this to prevent false radar detections?
 
Cablenut9
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Re: cAP ac only has 1 tx chain, but 2 rx chains  [SOLVED]

Tue Mar 02, 2021 5:25 pm

As it turns out, there's some 802.11 incompatibility issue with my old draft-ac router, as it bypasses "power saving" on the client devices, yet the cAP ac doesn't. I found that the fix was to turn off this "power saving" anti-feature on my client with
sudo iwconfig adapter-name power off
and now I'm reaching 866Mbps PHY speeds.

As for DFS, I chose it because the 5GHz spectrum is cluttered in the non-DFS bands, yet the DFS bands are free real estate.. Even though I live just a couple miles from one of the largest airports, I've never had issues with it dropping out or switching bands.
 
biomesh
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 6:05 pm

Great addition, biomesh. I alreay wondered why there was a /caps-man interface section in the export.

Why the advice not to use DFS channels? Is this to prevent false radar detections?
I avoid DFS as many devices can't or won't use it. Also the radar detections can cause outages while using non DFS channels will always work. 5GHz is pretty weak, so even if there is a lot of radios adjacent to your location, the impact will be less than 2.4GHz - if you have sufficient coverage to provide reliable access in all areas (aka use multiple APs).
 
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Re: cAP ac only has 1 tx chain, but 2 rx chains

Tue Mar 02, 2021 6:17 pm

Hmmm ... I'm late ?

Actually the PHY speed used is dynamic, and depends on the sequence of failed transmissions. Every time the transmission fails (after hw_retries attempts) the PHY rate is stepped down.
The current PHY is always visible in the "Registration" of the MKT AP. It reads like "866Mbps-80MHz/2S/SGI" till "6Mbps-20Mhz/1S"
It will lower MCS rate, bandwidth, number of streams, and swap short for long guard interval until it works. If it works repeatedly it will step up the scale again.
MKT does not show the MCS rate used but the PHY rate, so you have to use the mcsindex.com table.
(Some MUM presentation showed the new algorithm for the step down sequence: MCS versus other parameters)
It also depends on the signal path if multiple streams can be used or not. (and of course the number of chains on the client).

Reception quality can be different on both ends. (reflections, distortion, power used, interference ...). So it's no surprise if the PHY rates are different.
Not much you can about this on the AP side, except "hw-retries", limiting the highest (VHT-)MCS rates to 0-8 or 0-7, and HW-fragmentation-threshold.
Lowering AMSDU will facilitate the retransmission by working with smaller checksummed blocks.

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