USB-WiFi Frequently Asked Questions (FAQ)
Note: If you find that any of the answers below no longer work or are in need of an update, please let me know by posting a message in issues. Keeping the information on this site current is a challenge and can only work with your help. Thanks.
No. 1
Question: It appears that the Wireless Regulatory information is not correct in my system. How can I fix this?
Know the Country Code for your Country: List of Current ISO 3166 country codes
Information: When you run iw reg get you should be able to see the country code setting of your system and the information about the bands that you can use. Here is an example of what you should see. My country is US, so I see the following:
$ iw reg get
global
country US: DFS-FCC
(902 - 904 @ 2), (N/A, 30), (N/A)
(904 - 920 @ 16), (N/A, 30), (N/A)
(920 - 928 @ 8), (N/A, 30), (N/A)
(2400 - 2472 @ 40), (N/A, 30), (N/A)
(5150 - 5250 @ 80), (N/A, 23), (N/A), AUTO-BW
(5250 - 5350 @ 80), (N/A, 24), (0 ms), DFS, AUTO-BW
(5470 - 5730 @ 160), (N/A, 24), (0 ms), DFS
(5730 - 5850 @ 80), (N/A, 30), (N/A), AUTO-BW
(5850 - 5895 @ 40), (N/A, 27), (N/A), NO-OUTDOOR, AUTO-BW, PASSIVE-SCAN
(5925 - 7125 @ 320), (N/A, 12), (N/A), NO-OUTDOOR, PASSIVE-SCAN
(57240 - 71000 @ 2160), (N/A, 40), (N/A)
Note: If you are located in another country, the 2 letter country code should reflect your country code.
Example of what you may see if there is no country code set and your system is having to use the global defaults:
$ sudo iw reg get
global
country 00: DFS-UNSET
(2402 - 2472 @ 40), (6, 20), (N/A)
(2457 - 2482 @ 20), (6, 20), (N/A), AUTO-BW, PASSIVE-SCAN
(2474 - 2494 @ 20), (6, 20), (N/A), NO-OFDM, PASSIVE-SCAN
(5170 - 5250 @ 80), (6, 20), (N/A), AUTO-BW, PASSIVE-SCAN
(5250 - 5330 @ 80), (6, 20), (0 ms), DFS, AUTO-BW, PASSIVE-SCAN
(5490 - 5730 @ 160), (6, 20), (0 ms), DFS, PASSIVE-SCAN
(5735 - 5835 @ 80), (6, 20), (N/A), PASSIVE-SCAN
(57240 - 63720 @ 2160), (N/A, 0), (N/A)
Notice that country 00: DFS-UNSET indicates no country code is set.
What are some of the results of the country code not being set?
- 5 GHz channels do not allow access point operation (i.e.
iw listshows No-IR on all channels) - 6 GHz channels being completely disabled.
- 2.4 GHz channel may show a lower txpower than what is allowed in your country.
The list above is only a partial list of problems that can arise if the country code is not set properly.
The first step to fix this problem is to try to set the Country Code manually:
Open a Terminal interface - Ctrl + Alt + T
sudo iw reg set AU
Check to see if this fixes the problem:
iw reg get
If the Country Code is now set, I recommend Answer 2 below to make the setting persistent. If the Country Code is not set, then I recommend trying Answer 1.
Answer 1:
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/modprobe.d/cfg80211.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following line to the file:
options cfg80211 ieee80211_regdom=AU
Note: If your country code is not AU, you will need to replace AU with your country code
Save the file: (if using nano)
Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
To check if the country code setting of your system is now correct:
iw reg get
Answer 2:
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/systemd/system/regdom.service
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following lines to the file:
[Unit]
Description=Set wireless regulatory domain to US
[Service]
ExecStart=/usr/sbin/iw reg set US
[Install]
WantedBy=multi-user.target
Note: If your country code is not US, you will need to replace US with your country code
Save the file: (if using nano)
Ctrl + O, Enter, Ctrl + X
Run the following command to activate the new service file:
sudo systemctl enable regdom.service
Reboot:
sudo reboot
After reboot it should have run the command. You can check with:
systemctl status regdom
To check if the country code setting of your system is now correct:
iw reg get
No. 2
Question: My 6 GHz band shows as disabled when I run iw list. I want to be
able to use the 6 GHz band. How can I fix this?
Answer: This may happen with MEDIATEK cards and adapters on Linux 6.7.x or newer. There has been a lot of work on the WiFi support in Linux over the last year. We have seen an uptick in WiFi problems as a result. As of kernel 6.12, things seem to be getting better but there is work to be done.
A new feature called "CLC (Country Location Control)" must be disabled in the
mt7921_common module in order to use the 6 GHz band (for now). Make a file
called /etc/modprobe.d/mt7921.conf containing options mt7921_common disable_clc=1.
Example:
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/modprobe.d/mt7921.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following line to the file:
options mt7921_common disable_clc=1
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
Information: https://bugzilla.kernel.org/show_bug.cgi?id=218731
No. 3
Question: Why do I see high levels of jitter with my mt7922 or mt7921 based wifi card (PCIe or M.2)?
Information: Variance in ping times is called "jitter" in networking terminology; it refers to the inconsistency in the arrival time of data packets, essentially measuring how much your ping fluctuates over time. Jitter disrupts the smooth flow of data, resulting in noticeable disruptions, particularly in time-sensitive activities.
Information: Both chips use the mt7921e driver.
Answer: You can try disabling power management for that card as follows:
Open a Terminal interface - Ctrl + Alt + T
Create the following file:
sudo nano /etc/modprobe.d/mt7921.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following line to the file:
options mt7921e disable_aspm=Y
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
No. 4
Question: Why do I see high levels of jitter with my USB WiFi adapter?
Information: Variance in ping times is called "jitter" in networking terminology; it refers to the inconsistency in the arrival time of data packets, essentially measuring how much your ping fluctuates over time. Jitter disrupts the smooth flow of data, resulting in noticeable disruptions, particularly in time-sensitive activities.
Answer 1: First test to see if power_save is causing the issue:
Open a Terminal interface: Ctrl + Alt + T
Run the following command (remember to change wlan0 to the name of your wireless interface):
iw wlan0 set power_save off
Do not reboot as that will return power_save to on.
Test your system to see if there is improvement. If there is improvement, you may want to check the additional answers below for a persistent solution.
Answer 2: If your system uses Network Manager, you can disable power_save for the adapter as follows:
Open a Terminal interface: Ctrl + Alt + T
Create the following file:
sudo nano /etc/NetworkManager/conf.d/wifi-power_save.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following lines to the file:
# Values are 0 (use default), 1 (ignore/don't touch), 2 (disable) or 3 (enable).
wifi.powersave = 2
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
sudo reboot
Answer 3:
If your system uses systemd, you can disable power_save for the adapter as follows:
Open a Terminal interface: Ctrl + Alt + T
Create the following file:
Note: You can use your own favorite text editor in place of nano if you wish.
sudo nano /lib/systemd/system/wifi-power_save.service
Add the following lines to the file (remember to change wlan0 to the name of your wireless interface):
[Unit]
Description=Disable power_save for specific USB WiFi adapter
After=network.target
[Service]
Type=oneshot
ExecStart=/usr/bin/iw wlan0 set power_save off
[Install]
WantedBy=default.target
Save the file: Ctrl + O, Enter, Ctrl + X
Run the following command to enable the new service:
sudo systemctl enable wifi-power_save.service
Run the following command to verify that the service is functioning properly after rebooting:
Note: remember to change wlan0 to the name of your wireless interface.
iw wlan0 get power_save
Run the following command to disable the service if you need to disable it:
sudo systemctl disable wifi-power_save.service
No. 5
Question: I am having problems with my Alfa AXML or Alfa AXM or Comfast CF-953AX. The wifi is not working. It seems to crash when coming up. What can I do?
Answer: This is a known problem that started in early 2024 around the time kernel 6.7 was released. There have been unsuccessful attempts to fix this problem. It is a strange problem in that it seems that bluetooth is involved. Most adapters with the mt7921au chipset do not have this problem. The 3 adapters listed in the question are the only 3 known to have this problem so it appears that something specific to these 3 adapters is causing the problem. Right now all that can be offered is a workaround.
This workaround was posted by @ZerBea :
Use one of the following Linux kernels if possible:
6.6.x (or earlier)
or
6.12.x (or later)
To check your kernel: $ uname -r
You may ask why? A tremendous amount of work over the last year or so had to do with adding WiFi 7 support to the Linux kernel. As time passes, the new drivers are becoming more and more complex. This has contributed greatly to overall problems. We have seen an abnormal amount of problems from kernel 6.7 through 6.11. I think kernel 6.8 was the worst of the bunch. You will be doing yourself a favor by avoiding kernels 6.7 to 6.11.
Make sure you're running the latest WiFi firmware:
[18615.766176] mt7921u 1-9.3:1.3: WM Firmware Version: ____010000, Build Time: 20241106151045
Instructions for updating the firmware can be found at the following location:
Disable BT stack:
Create the file: $ sudo nano /etc/modprobe.d/local-dontload.conf
Note: You can use your own favorite text editor in place of nano if you wish.
Add the following line to the file: install btusb /bin/false
Save the file: Ctrl + O, Enter, Ctrl + X
Reboot:
$ sudo reboot
If WiFi is not working in a USB3 port, try a USB2 port or a USB2 hub
The above solution, that shuts down bluetooth support, may not work well for people that have other bluetooth support in their system and they want to use it. In that case, simply delete BT firmware file for your adapter.
Now dmesg should print this:
[20844.686881] usb 1-9.3: new high-speed USB device number 12 using xhci_hcd
[20844.818337] usb 1-9.3: New USB device found, idVendor=0e8d, idProduct=7961, bcdDevice= 1.00
[20844.818343] usb 1-9.3: New USB device strings: Mfr=6, Product=7, SerialNumber=8
[20844.818346] usb 1-9.3: Product: Wireless_Device
[20844.818347] usb 1-9.3: Manufacturer: MediaTek Inc.
[20844.818349] usb 1-9.3: SerialNumber: 000000000
[20845.018645] usb 1-9.3: reset high-speed USB device number 12 using xhci_hcd
[20845.159101] mt7921u 1-9.3:1.3: HW/SW Version: 0x8a108a10, Build Time: 20241106151007a
[20845.420854] mt7921u 1-9.3:1.3: WM Firmware Version: ____010000, Build Time: 20241106151045
[20847.020857] mt7921u 1-9.3:1.3 wlp22s0f0u9u3i3: renamed from wlan0
test monitor mode and packet injection:
$ sudo hcxdumptool --rcascan=active --tot=1 -c 1a
...
^C
132 Packet(s) captured by kernel
0 Packet(s) dropped by kernel
57 PROBERESPONSE(s) captured
Monitor mode (device entered promiscuous mode) and packet injection (57 PROBERESPONSE(s) captured) is working!
exit on sigterm
$ sudo dmesg
[21146.046337] mt7921u 1-9.3:1.3 wlp22s0f0u9u3i3: entered promiscuous mode
[21153.630136] mt7921u 1-9.3:1.3 wlp22s0f0u9u3i3: left promiscuous mode