2.4 GHz WiFi Trouble? Disable Bluetooth.

tl;dr: Bluetooth and 2.4 GHz WiFi don’t play nicely together. Here’s how I figured it out.

I have both 2.4 and 5 GHz networks running in my home. I have found that my personal laptop has a really hard time scanning for / connecting to 2.4 GHz networks. It’ll eventually connect, but it takes up to a few minutes to find the 2.4 GHz network and work out a connection.

I got tired of it and started searching the Interwebz.

At some point in my web searches, I learned that I’m running an Intel wireless network card using the built-in Linux kernel iwlwifi driver. Here’s partial output of lspci -k:

02:00.0 Network controller: Intel Corporation Wireless 8265 / 8275 (rev 78)
    Subsystem: Intel Corporation Wireless 8265 / 8275
    Kernel driver in use: iwlwifi
    Kernel modules: iwlwifi

I also learned about the various config parameters for this driver. Here’s partial output of modinfo iwlwifi:

parm:           swcrypto:using crypto in software (default 0 [hardware]) (int)
parm:           11n_disable:disable 11n functionality, bitmap: 1: full, 2: disable agg TX, 4: disable agg RX, 8 enable agg TX (uint)
parm:           amsdu_size:amsdu size 0: 12K for multi Rx queue devices, 2K for AX210 devices, 4K for other devices 1:4K 2:8K 3:12K (16K buffers) 4: 2K (default 0) (int)
parm:           fw_restart:restart firmware in case of error (default true) (bool)
parm:           nvm_file:NVM file name (charp)
parm:           uapsd_disable:disable U-APSD functionality bitmap 1: BSS 2: P2P Client (default: 3) (uint)
parm:           enable_ini:0:disable, 1-15:FW_DBG_PRESET Values, 16:enabled without preset value defined,Debug INI TLV FW debug infrastructure (default: 16)
parm:           bt_coex_active:enable wifi/bt co-exist (default: enable) (bool)
parm:           led_mode:0=system default, 1=On(RF On)/Off(RF Off), 2=blinking, 3=Off (default: 0) (int)
parm:           power_save:enable WiFi power management (default: disable) (bool)
parm:           power_level:default power save level (range from 1 - 5, default: 1) (int)
parm:           disable_11ac:Disable VHT capabilities (default: false) (bool)
parm:           remove_when_gone:Remove dev from PCIe bus if it is deemed inaccessible (default: false) (bool)
parm:           disable_11ax:Disable HE capabilities (default: false) (bool)
parm:           disable_11be:Disable EHT capabilities (default: false) (bool)

Well hey, what’s this bt_coex_active:enable wifi/bt co-exist business? Some web searching led me to this very old SuperUser answer:

The 2.4 GHz Wifi band and bluetooth spectrums have a great deal of overlap and can conflict with each other

So apparently you can configure your driver to not allow Bluetooth and 2.4 GHz WiFi to be activated simultaneously, which can be important because their operating frequencies overlap.

I don’t use (or like) Bluetooth anyway, so instead of messing with my driver, I just decided to turn Bluetooth off permanently.

sudo systemctl disable --now bluetooth

Problem solved.