Re: Prevent auto scan in wireless devices

[Aloisio Almeida <aloisio almeida openbossa org>]

Hey Tony,

Before come to work I was thinking exactly the same. Actually prevent
the background scan is not the main point. We must save power. Why
would you have a wireless card that does nothing? Turn it off.

I think nm should have a kind of SAVE_POWER profiling that can be
automatically activated when running on battery, and in this mode it
could turn the wireless card off when disconnected and turn it on only
by client request, for instance.

When activated, the scan interleaving times could be increased to all
modes, but i don't know if this is really necessary.

Another thing to discuss is if the frequent firmware load/unload can
brings us some problem or not.


On Tue, Jan 13, 2009 at 6:53 PM, Tony Espy <espy canonical com> wrote:
> Aloisio Almeida wrote:
>>
>> Hi all,
>>
>> I noticed that wireless devices are always scanning, and this is very
>> bad to power consuption in embedded systems.
>
> Having looked at Wi-Fi power consumption last year while working on a MID
> project, we did some measurements with a Marvell SD8686 card and found that
> backing off the scanning didnd't really save all that much power compared to
> when the device was associated with an AP and PS-Mode was enabled.
>
> This led us to the conclusion that the only way to really save power while
> unassociated ( at least with the SD8686 ) was to toggle the power to the
> card when NM was in it's inactive phase ( ie. not associated, and not
> currently scanning ).
>
> I haven't looked to closely at NM 0.7 to see how applicable this approach
> is, but if I get some time, I'll try and do so...
>
>> Any comments? Is it a good way to implement that?
>
> In the past, Dan has stated that he's against making scanning directly
> controllable via DBUS.
>
> Ciao,
> /tony
>
>