Answer by Jeremy31 for Internet Slow on Fedora 23

An old bug report indicates that a performance gain can be achieved using

echo "options iwlwifi 11n_disable=8" | sudo tee /etc/modprobe.d/iwl11n.conf

Reboot

This option actually doesn't disable anything but enables aggressive TX

Also check the encryption of the wireless access point

iwlist scan | egrep -i 'ssid|cipher'

You want to see this below your access points ESSID

                        Group Cipher : CCMP                        Pairwise Ciphers (1) : CCMP

If you see TKIP, it will cause problems. Most routers will have a encryption setting to disable TKIP usually called WPA2-AES, WPA2 only, or WPA2-PSK