Horrible wireless network pings in Ubuntu and how to fix them

Yesterday I had an important video call that I needed to carry out under Ubuntu as I need to demo some of my work. About two minutes before it was due to begin, I noticed that my pings to the home network router were ridiculously variable and high:

PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=60.3 ms
64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=82.9 ms
64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=105 ms

Awful.

Unfortunately, two minutes before an important call is not the time to be tinkering with network settings, so I left it at the time. Fortunately, it didn't seem to adversely affect the call.

Later, I booted into Windows to find my pings were perfectly normal (1 ms)¹. So, what's the issue under Linux?

What it turns out to be is wireless power management. You can easily test this by trying:

sudo iwconfig wlan0 power off

and remeasuring the pings:

64 bytes from 192.168.0.1: icmp_req=1 ttl=64 time=0.970 ms
64 bytes from 192.168.0.1: icmp_req=2 ttl=64 time=1.04 ms
64 bytes from 192.168.0.1: icmp_req=3 ttl=64 time=0.994 ms

Much better!

Thanks to this forum thread, I found an easy way to make this fix permanent, you need to do something like:

sudo nano /etc/pm/power.d/wireless

and add the following lines to the newly created file:

#!/bin/sh

/sbin/iwconfig wlan0 power off

Next, do:

sudo chmod +x /etc/pm/power.d/wireless

so that this script is executable.

Next time you reboot, the fix should still be in place.