Wifi power saving mode

WifiPSM Nokia 770 and n800 supports Wifi Power Saving Mode (often called PSM), in order to improving battery life while keeping network connection.

Unfortunately, a lot of Wifi Access Point (AP) don't support completely PSM and using full PSM mode can cause network trouble.

For Nokia 770 (running with Hacker Edition 2007), it is possible to configure a timeout for enabling PSM (with IT2006, it is not configurable).

To do so, in xterm, run :

gconftool-2 --set --type int /system/osso/connectivity/IAP/wlan_sleep_timeout 200

This will set sleep timeout at 200ms (by default, it is set to 1000ms for IT 2007.3 and earlier. For IT 2007.4 and later, it is set to 200ms).

You might want to try full power saving, by setting timeout to 0.

To reset timeout to default behaviour, run :

gconftool-2 --unset /system/osso/connectivity/IAP/wlan_sleep_timeout

For Nokia n800 / n810, one additional timeout value is available :

inactive_wlan_sleep_timeout (by default, its value is 100ms)

This value is used when lcd display is turned off.

Be sure to test if network latency is still good when testing timeout value.

To test it, with a other device connected on the same subnet, run, after connecting Nokia device to Wifi network :

ping -i 2 192.168.x.y

where 192.168.x.y is IP address of Nokia device.

There is should not be any paquet drop.

You might want to test also with arping -I eth0 -b 192.168.x.y

where eth0 is your interface in the same subnet as Wifi network.

If there is, you should try to increase timeout. Beware using very small timeout (10-100ms) might lead to increase power consumption, because radio chip might be always switching between shutdown and power-on state (when waiting for slow DNS reply for instance).