The following workaround has solved my issue on my ThinkPad X220 with Intel Centrino Wireless-N 1000 card using iwlwifi driver (except, of course, that I don't have N wireless capabilities now):
1) Create a file at /etc/modprobe.d/intel_11n_disable.conf containing this one line:
options iwlwifi 11n_disable=1
The following workaround has solved my issue on my ThinkPad X220 with Intel Centrino Wireless-N 1000 card using iwlwifi driver (except, of course, that I don't have N wireless capabilities now):
1) Create a file at /etc/modprobe. d/intel_ 11n_disable. conf containing this one line:
options iwlwifi 11n_disable=1
2) Run this command:
sudo update-initramfs -u
3) Reboot