9120 (.11ax) vs 2802 (.11ac) upload speed too slow

[EURL_IPSENS]

Hi guys,

I'm facing a "strange" behavior. I'm running a setup where there are 2 AP (1x 2802E + 1x 9120AXI), with a really low upload speed on 9120, they are running on vWLC 8.10.185.0.
I can easily reach gigabit in download speed for both, a correct upload speed on 2802E, but a really low upload speed on 9120AXI
2802 DL (max/med) : 920/802 - UL : 590/560
9120 DL (max/med) : ~1500/980 - UL : 38/30

Shouldn't 802.11ax have higher throughput speed than 802.11ac ? Is it a problem with the AP ? I check everything I can, but maybe I missed a setting somewhere ?

Speed have been testing two different clients, both supported .11ax, both have quite the same result (even at <5m distance from ap).
Clients :  Intel Corporation Wi-Fi 6E AX211 160MHz and Xiaomi 12 Pro.

In controller, all MCS bands enabled, 160Mhz channel width, 11ac/ax mode enabled, clean air and BSS coloring enabled, UP+Down MU-MIMO + OFDMA enabled on Wlan

Any advice would be greatly appreciated.

[Leo Laohoo]

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@EURL_IPSENS wrote:
Clients :  Intel Corporation Wi-Fi 6E AX211 160MHz

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Intel has released a series of wireless NIC drivers to fix issues with the AX2xx when joining/joined to an 802.11ax-capable AP.  

Please refer to CSCwe50033.  

Realtek RTL8852-based wireless NIC drivers also has similar bugs (CSCwf03870).

[Rich R]

Update Intel driver to https://www.intel.com/content/www/us/en/download/19351/windows-10-and-windows-11-wi-fi-drivers-for-intel-wireless-adapters.html then re-test.

[EURL_IPSENS]

Hi guys,

Forgot to tell, I'm running Linux with latest kernel & latest firmware for iwlwifi. I'll give a try asap under windows.
But remember, same issue exists with my phone (Mi 12 Pro, can't find any details regarding the embedded wifi chipset). I don't have any other .11ax capable devices to test at the moment.

[EURL_IPSENS]

Hi guys,
Got some news, I tried with another .11ax client (MT7921AU Chipset), which is running no problem 500Mbit/s+ in upload, but it's a 80Mhz channel width max.

So I downgraded my DCA to 80Mhz, and both the previous clients are getting higher upload rates (100-300Mbit/s), it's not perfect but it more a problem with channel width rather than a driver issue (remember, both are running different OS and WiFi chipset).

Any idea ? How to debug ?

[Rich R]

> it more a problem with channel width rather than a driver issue
Well I don't think that's necessarily true - you might have actually just proved that all those drivers have trouble with 160MHz channel bonding.

Using super-wide channels "just for the sake of it" will mean that you discover more problems like this.  40 (or 80MHz) channel width is more than adequate for most use cases and will provide a more stable and reliable service too generally.  To really work out why it's happening will require debugs on both sides and OTA captures to analyse the behaviour in fine detail.  Given that AireOS vWLC has already passed the end of software maintenance milestone it's not going to get fixed even if a bug is identified.  If you can identify the same issue on 9800-CL IOS-XE 17.9.4 or 17.12.1 and it's proven to be an AP or WLC problem then TAC can open a bug for it to get it fixed.  If it proves to be a client driver problem you'll need to raise that with the driver vendor. 

> Any idea ? How to debug ?
Don't waste time debugging on AireOS - it's effectively EOL.
Move to 9800-CL on a current extended support release (17.9 or 17.12).  If you see the same problem open a TAC case for guidance on troubleshooting the issue.