At first check if powersaving is on,

ifconfig

…. if wlan0, run

iwconfig wlan0 | grep "Power Management"

Edit the next file changing the value from 3 to 2 and after editing reboot

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

[connection]
wifi.powersave = 2

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An another way:

If wlan connection disappears every now and then, disable wlan´s powersave.

1. Check your wlan
nmcli dev | grep wlan
2. Add the line to the /etc/rc.local file
sudo nano /etc/rc.local
… add the line
iwconfig wlan0 power off
… if your wlan is wlan0
3. Save and quit
Ctrl o
Ctrl x

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A third way is to make a script like:

#! /bin/bash
xterm -e su -c 'iwconfig wlan0 power off' root

… or

#! /bin/bash
xterm -e sudo iwconfig wlan0 power off

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Keywords: wifi, wlan, power, network, connection, drop