Selecting the 40 MHz channel in WPA Supplicant

Not being able to connect to a 40 MHz Wifi Channel is not a problem on the Linux side per se in this case. WiFi is a complex protocol, and even more down to the definition of the protocol and particular bits of how to is implemented by different vendors.

As we can see from the output of your commands, you are using Cisco equipment and the client is in the 2.4GHz band. The culprit is the Cisco WiFi gear/AP is not supporting 802.11n over 2.4GHz.

From Cisco forums:

Cisco does not support channel bonding in 2.4 GHz frequency (802.11 b/g), because only three non-overlapping channels 1, 6 and 11 are available.
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In 802.11n, two adjacent channels, each of 20 MHz are bonded to get a total bandwidth of 40 MHz. This provides increased channel width to transmit more data. Cisco does not support channel bonding in 2.4 GHz frequency (802.11 b/g), because only three non-overlapping channels 1, 6 and 11 are available. However, the channel bonding has more relevance in 5 GHz frequency range where you have as many as 23 adjacent non-overlapping channels currently available. Channel bonding is supported only in 5 GHz, for example 802.11a.

Also, as a footnote, if you want to try other 2.4GHz equipment, beware the WiFi protocol defines 40MHz channels only go up if the AP does not sense other nearby APs also transmitting in overlapping frequencies. Some vendors chose to ignore that, hostapd and other vendors do not ignore that feature.

Nevertheless, if you want to use 40MHz with that Cisco equipment, you need to use a WiFi stick or a client that supports 5GHz.

PS. I do advise to see the vendor literature of both the AP and client Wifi chipset in the future when doing experiments for having a notion of what it is supported. Beware that also distance to the AP/noise/quality of signal/quality of wifi adapter can determine you won't be able to operate at the full AP offered speed.

I would advise also reading for general WiFi knowledge my related answer Wi-Fi problems using ASUS USB-N13 adapter (realtek)


The problem is with the firmware of the chipset I am using. The vendor has disabled the channel bonding in the configuration. Once I enabled it I can connect it to the 40 Mhz Channel. The Qualcomm chipset requires the gChannelBondingMode24GHz variable to be set as one in the configuration file

Tags:

Wifi