Two solutions for this

1) remove the driver from the kernel and re-insert it.

sudo rmmod iwlwifi

sudo modprobe iwlwifi

2) Create a file and add the following line to it :

sudo gedit /etc/modprobe.d/iwlwifi.conf

and then this line should be added inside the file and then re-boot:

options iwlwifi 11n_disable=1

Thanks to the following reference.