WiFi powersave broken?

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derek
Posts: 96
Joined: Fri Oct 22, 2010 12:26 am

WiFi powersave broken?

Post by derek »

I don't know whether this has always been the case but now with Ubuntu I observe that the WiFi works initially when booted up but within seconds to minutes after boot the WiFi interface disappears and cannot be resurrected (and this also causes shutdown to hang most of the time and may be related to the lspci command hanging and then making the shutdown even more likely to hang).

I believe this is caused by enabling powersave mode in the WiFi, which Ubuntu does by default.

To work around this I edited /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf and changed wifi.powersave = 3 to wifi.powersave = 2 (3 means enabled, 2 means disabled).

I guess this is some kind of driver / firmware problem. As I am powering my IPC3 from the mains, I don't really mind if it never powersaves (and I certainly do mind all the symptoms above).

Anyone else seeing this?
Does this happen with Mint?

jens
Posts: 33
Joined: Thu May 07, 2009 2:32 pm

Re: WiFi powersave broken?

Post by jens »

I was having some strange issues with Wifi on Windows which sound like what you are
describing. The wifi would work until the machine had gone into sleep mode. When it woke up it
was hit or miss whether the wifi card could start up. I even replaced the card, but with the same result.
I disabled Hibernating in Windows and after that is ran great of a while. Yesterday it started acting up again.
I do not know if Windows Update has rolled something back.

derek
Posts: 96
Joined: Fri Oct 22, 2010 12:26 am

Re: WiFi powersave broken?

Post by derek »

Hard to say whether it's the same thing.

The difference between the two situations is that when the operating system hibernates or goes into standby then all or most of the hardware in the system is completely switched off or goes into a low power state - and then, on the way back out, operating systems and/or devices are notorious for not coming back properly. This is usually a software / firmware problem.

Powersave mode within WiFi is a mode that is specific to and affects only WiFi - while the rest of the system operates normally. The WiFi client device and the Wireless Access Point cooperate so that the client device can sleep most of the time and only wake up periodically to listen to the WAP to see whether the WAP is telling it that there is traffic that the WAP wants to transmit to the client device (i.e. effectively data for the client device to receive). On the transmit side, I suppose the host computer controls coming out of powersave mode when there is data queued to transmit.

Since you specifically say "hibernation", it probably isn't the same problem because the expectation with hibernation is that everything is powered completely off (so the WiFi client device is "off", not powersaving) - but I don't use Windows so take with a grain of salt.

Maybe check other power management settings for the computer as a whole to ensure that nothing happens after X minutes (except possibly switching off the screen).

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