Set wifi.powersave to 2 to disable powersave

 

sudo nano /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf 

NM_SETTING_WIRELESS_POWERSAVE_DEFAULT (0): use the default value
NM_SETTING_WIRELESS_POWERSAVE_IGNORE  (1): don't touch existing setting
NM_SETTING_WIRELESS_POWERSAVE_DISABLE (2): disable powersave
NM_SETTING_WIRELESS_POWERSAVE_ENABLE  (3): enable powersave