Re: Does the HostAP driver come up at max TX power?

From: Jouni Malinen (
Date: 2002-04-05 18:30:54 UTC

On Sat, Mar 30, 2002 at 01:32:14AM -0500, Brian Capouch wrote:
> Jouni Malinen wrote:

> > It depends.. The driver does not touch any TX power related
> > configuration unless specificly asked to with 'iwconfig wlan0 txpower
> > <val>'.

> Just to be safe, can we hurt anything if <val> is too high?
> I'm not quite sure what to use there, although I think you have
> addressed this in a post somewhere along the line.

I would assume that nobody would produce cards that are so clear to breaking point that setting TX power to maximum would be fatal. At least I have never had any problems with setting TX power to maximum value. Anyway, I'm not given any guarantees for the driver operations.. ;-)

The driver maps given power levels with somewhat adhoc method to a value that is then written to baseband processor configuration registers. Thus, it is a bit difficult to determine a proper setting without testing. I have just tried to make it about right on some test cards, but its certainly not exact. I set 20 dBm to be the maximum value (i.e., 'iwpriv wlan0 txpower 20'). Anything above 20 does not really change the value at all. Similarily, -44 dBm is mapped to minimum and anything below it results in the minimum value.

Jouni Malinen                                            PGP id EFC895FA

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