[Prism54-devel] Re: [Prism54-users] Output power regulation - SMC2802W

[Aquila]

Hi,

Sorry to interject :)

You can have a negative dBm value like Aurelien
stated. If I remember correctly there are a couple of
factors that play a roll in the max and min of this
setting.
1) The max output power level that the card has been
calibrated for.
2) The domain setting.
3) The hardware components.

I have tested this OID by hooking the card up to a
spectrum analyzer and measuring the output levels with
a power meter, the OID does indeed work. The lowest
value is zero dBm on the cards I tested (reference
design cards), I was told that this was a limitation
of the PA on the card. That it wasn't able to go below
0 dBm. But if a different card manufacturer uses a
different PA it might be possible to go lower (I guess
the question is: why would you want to?).

The maximum value that the card outputs is the value
that the card is calibrated for. EG. if the card is
manufactured to output a max of 15 dBm then even if
you set the OID to 127 the card will still only output
15dBm. 127 doesn't seem to be an "auto" setting.

Another limitation is the domain setting, if the card
is able to output 30 dBm but the domain is set to ETSI
(with a limit of 20dBm) then it will only output 20dBm
(and 18.5dBm on the edge channels 1&13). As opposed to
the FCC domain which is limited to 30dBm on channels
2-10 and something like 17-18dBm on channels 1 & 11
(edge channels). I'm told this is for spurious
emissions to meet regulatory requirements. If anyone
knows the proper regulatory limits, please correct me
if I'm quoting those limits incorrectly.

Regards,
Aquila


-----Original Message-----
From: prism54-devel-admin@prism54.org
[mailto:prism54-devel-admin@prism54.org] On Behalf Of
Aurelien
Sent: Wednesday, January 07, 2004 11:13 AM
To: prism54-devel@prism54.org
Subject: Re: [Prism54-devel] Re: [Prism54-users]
Output power regulation - SMC2802W


Hi,

On Wed, 07 Jan 2004 11:49:12 +0200
kaleda <gadeanta@soften.ktu.lt> wrote:

> > 2) There is probably a value for automatic mode
(127 ?).
> Also no documentatation.
> But one note: when I bring the card up - the default
value in output 
> power oid is _always_ 127, so maybe this is auto
mode.

Yep that's what made me think this was auto mode.
 
> > 3) How does it behaves with negative values ?
> ???
> What do you mean negative values ??? How strangth
can be negative ? 
> And as I already mentioned - you cannot set value
bigger than 127, so 
> there's no negative value.

Well, a power in dBm can be negative. And when I tried
your patch, I was able to set the oid to some negative
value.

 > 4) Does it really works as expected ? I'm not able
to test it...
> I also have no specific equipment to precise measure
output power. But 
> simple experiment showed that it changes: I set
output power to max 
> (127) and connect with client. I set output power to
much lesser value 
> (e.g.70), client shows lower connection quality.
> Again set txpower to lower (lets say 10), client
shows event lower
> quality.
> So I think it works.

Ok, it works :-)

> 
> > And last but not least, I don't think this feature
will be usefull.
> > Max value is hardware (or firmware ?) coded, and
by default card
adjusts 
> > power dynamically (allowing max value).
> If you're using prism54 card in client mode - its
useless, 'cause 
> afaik
> cards sets output power according to AP output power
( correct me, if
> I'm wrong).
> But in AP mode it's very usefull.

I don't know and I don't use AP mode. That's probably
why I didn't find it usefull...

> > But if anyone find it usefull, feel free to work
on it...
> Ok, I'll try to submit another patch, to newer
driver version 'cause 
> since last time I patched it, many things changed in
the > driver.

Cool. Please put some usefull comment in your code...

	...And justice for all
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