Which router supports manually setting MCS?

meli · November 29, 2021, 12:56pm

Hi all,

I'm a new bee in the OpenWrt forum. I want to manually set the radio to certain MCS for experimental use. Specifically, I want to switch MCSes to test the performance of a video streaming application in a wireless network.

Searching in the forum (and also the web) returns that I can set the MCS with

iw dev wlan1 set bitrates ht-mcs-2.4 1

where wlan1 is the radio in use. However, I've tried with two routers, Linksys WRT32X and Redmi AC2100. Both routers return with:

command failed: Not supported (-95)

The Linksys uses the mwlwifi driver (readlink /sys/class/net/wlan1/device/driver returns). Is it the issue of iw or driver? Are there any suggestions on which router supports manually setting the MCS? Thanks in advance!

slh · November 29, 2021, 9:42pm

Just be aware that modern wifi (anything beyond 802.11g) is a heavily fluctuating, dynamic system, the wireless rate needs to accommodate for that. Setting MCS values does not make sense in practice and is usually actively harmful - and especially newer wireless chipsets with fullmac'ish firmwares won't honour these settings anyways.

meli · November 30, 2021, 2:08am

Thank you slh! Do you have any idea on which chipset supports such settings?

lleachii · November 30, 2021, 5:31pm

Is the OpenWrt the client or AP in this scenario?

meli · December 1, 2021, 1:51am

Hi lleachii, OpenWrt is the AP

meli · December 5, 2021, 8:36am

For the people interested:

I've test five routers, and some of them work with iw dev xxx set bitrates:

Xiaomi Redmi AC2100 [Does not work]
Linksys WRT32X [Does not work]
Netgear WNDR3800 [Works]
TP-Link TL-WDR4900 [Works]
GL-iNet AR150 [Works]

At least ath9k-based drivers work with the manually set bitrates. Using Openwrt 18.06.

ManasSam · November 5, 2022, 5:37pm

To add to the above list, I was able to confirm that setting the MCS index also works with many mt76 wireless radios (tested in Openwrt 21.02 on Netgear R6120, R6220, R6850, etc.)

Does anyone know of a way to set this option in the hostapd.conf itself so that it doesn't have to be manually set using iw?
(Update: found this patch that hasn't been merged yet)