i recently noticed that my wifi was really slow. checking it revealed that i only had 1Mbit as bitrate, while the link quality was fine.

after fiddling around with various settings on the ap the reason turned out to be a b0rken iwlwifi driver. disabling bluetooth in the bios together with this module configuration helped:

# /etc/modprobe.d/iwlwifi.conf
options iwlwifi bt_coex_active=0 swcrypto=1 11n_disable=8

cf. debian wiki


$ iwconfig wlan0
wlan0     IEEE 802.11abgn  ESSID:"???"  
          Mode:Managed  Frequency:5.22 GHz  Access Point: ???
          Bit Rate=135 Mb/s   Tx-Power=15 dBm   
          Retry short limit:7   RTS thr:off   Fragment thr:off
          Power Management:on
          Link Quality=54/70  Signal level=-56 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:12   Missed beacon:0