How to set wifi driver settings to prefer 5 GHz channel above 2.4 GHz

Run:

$ iwlist wlan0 scanning | grep -C3 <name of your network>

You should find 2 entries for the network, for example:

Cell XX - Address: 11:11:11:11:11:11 // This will be different in your machine
ESSID: "name of your network" // This will be different on your machine
Protocol: IEEE 802.11bgn
Mode: Master
Frequency: 2.437 Ghz

--

Cell XX - Address: 22:22:22:22:22:22 // This will be different on your machine
ESSID: "name of your network // This will be different on your machine
Protocol: IEEE 802.11AC
Mode: Master
Frequency: 5.18 Ghz

• BSSID for the 5Ghz Network, in this example: 22:22:22:22:22:22
• BSSID for the 2.4 Ghz Network, in this example: 11:11:11:11:11:11

Now what you do is:

1. click on 'Network Connections'
2. 'Edit Connections...'
3. [Select your network connection] (there could be 2 entries, any will do)
4. Click Edit
5. Go to 'Wi-Fi' or 'Wireless' Tab
6. Click the BSSID Dropdown
7. Select the BSSID Matching the 5 Ghz Network (22:22:22:22:22:22 in this example)
8. Switch to the 'General Tab'
9. Make sure to check the checkbox that is labeled: 'Automatically connect to this network when it is available'
10. Rename the Connection Name (not the SSID) to 'your network name'_AC
11. Click Save
12. If there were 2 entries for 'your network name' in your Network Connections list, proceed with next step, otherwise go to the last step.
13. Click on the other 'your network name' entry
14. Click Edit
15. Go to 'Wi-Fi' or 'Wireless' Tab
16. Click the BSSID Dropdown
17. Select the BSSID Matching the 2.4 Ghz Network (11:11:11:11:11:11 in this example) OR leave the BSSID empty if there are multiple other secondary access points
18. Switch to the 'General' Tab
19. Uncheck the checkbox that is labeled: 'Automatically connect to this network when it is available'
20. Set the 'Connection name' to [your network name]_N
21. Click Save...
22. Disconnect from your network and re-connect

You should now be connected to the 5Ghz network, and you would have to explicitly do the opposite process in order to connect to the 2.4 Ghz Network.

Method 1 — for use at home with a single wireless router

First, connect to your basic wifi network under "Infrastructure". Next, click on BSSID. The BSSID you are connected to at that time should appear when you click on that arrow. This feature prevents your computer from switching networks. 2.4 Ghz and 5 Ghz.

Method 2 — roaming on a network with multiple access points like a college campus or public wifi

_{NOTE: If you used the method above, you will need to do the opposite before you begin. Make sure the BSSID is not set to anything (is blank) so that you can use multiple access-points and roam across the network.}

First, you will need to edit the system-connections file that corresponds to your network. For this example, I will use a network named "coffee-shop".

sudo nano /etc/NetworkManager/system-connections/coffee-shop

Now, under the [wifi] section, edit the band field to the following (if band= is not listed, you can insert it on the line below [wifi]):

band=a

This will set the network to use 5 GHz only. If you want to use 2.4 GHz, use band=bg instead.

When you are done editing, press CTRL+o and then press ENTER to save the file and then press CTRL+x to exit nano.

Finally, restart network-manager to apply the changes:

sudo systemctl restart network-manager

Click here for more information.

_{NOTE: this setting does not exclude you from using wireless n or wireless c (so don't worry), this feature is only used to select 2.4 or 5 GHz}

Change that "Ad-hoc" option to something else, like "Infrastructure" (or a similar menu option). Infrastructure wireless is your typical "lots of devices connecting to a single router" approach, while ad-hoc wireless is intended for a "mesh" of wireless devices with no centralized router.

Being in ad-hoc mode is likely what's causing your problem (and this is further evidenced by the error message you provided).

This may work or may not work. Based on my experience, it is inconsistent. On the network manager settings, you can manually enter the BSSID of the AP. You can found out the BSSID using an android application called 'WIFI analyzer'. You can also use other linux based wifi monitoring tools like Kismet, but the easiest way that I found out is using the android application. If you don't know, 5Ghz AP have higher channel number (more than 13). Now, the inconsistency, depending on distro, the BSSID select box may be populated, or you have to input it manually. Either way, enter the BSSID that you wish to connect, and set the name of the network to something you can remember, like "U-WIFI-5Ghz". Now unfortunately, sometimes the network will appear (and you can connect to that specific AP) and sometimes it do not even if you know the AP is close by.

Run the following commands, one line at a time in the terminal (CTRL+ALT+T):

echo "options iwlwifi 11n_disable=1" | sudo tee /etc/modprobe.d/iwlwifi.conf
sudo modprobe -rfv iwldvm
sudo modprobe -rfv iwlwifi
sudo modprobe -v iwlwifi

What does this do? The 11n_disable option disables 802.11n features. Adding it to

/etc/modprobe.d/iwlwifi.conf

makes the change persist after reboots (because it will be part of the module config). The modprobe -rfv commands are removing the kernel modules iwldvm and iwlwifi, and finally the last line modprobe -v is adding iwlwifi back in.

To know what those kernel modules are/do, you can run modinfo | grep description, which will tell you the following:

iwlwifi is an Intel(R) Wireless WiFi driver for Linux (generic Intel drivers)

iwldvm is Intel(R) Wireless WiFi Link AGN driver for Linux (more specific drivers)

Other suggestions

Now, check the settings in the router. WPA2-AES is preferred; not any WPA and WPA2 mixed mode and certainly not TKIP. Second, if your router is capable of N speeds, You may have better luck with a channel width of 20 MHz in the 2.4 GHz band instead of automatic 20/40 MHz. I also have better luck with a fixed channel, either 1, 6 or 11, rather than automatic channel selection. After making these changes, you may need to reboot the router.