Richard Jonsson wrote:
> On Monday 06 August 2007 03:21:11 you wrote:
>> Richard Jonsson wrote:
>>> Isn't Desired TX power supposed to adapt so that higher bitrates are
>>> possible, with Bit Rate going lower if that is not enough to keep a good
>>> connection?
>> Richard,
>> Please grab a new copy of the port_to_mac80211 patch, and try the patch
>> below. It boosts the desired power by up to 5 dBm as signal - noise
>> decreases from 20 to 0.
>> Larry
> Hard to say if there is a difference. I've noticed that signal quality 
> changes 
> between reboots. When I first tried this patch I couldn't get above 36M even 
> at the AP, so I loaded the version without the patch. Same thing.
> So I rebooted and then all rates worked, even 11M. Even for the driver 
> version 
> that didn't work a few days ago.

That is scary! That may mean that something is not being reset. The real 
question is whether warm 
reboots are intrinsically different than cold (power-off) reboots.

> New/updated observations:
> Rate scaling seems to work, but if it gets down to 1M it will not rise again 
> unless I force it to a higher bitrate and run iperf for a few seconds before 
> setting it to auto. This is even when signal is -5dBm and noise is -80dBm. I 
> get a feeling it's a bit to sensitive as it will drop quickly at a few meters 
> away. At this distance forced 54M still works well.
> Maybe this is due to small dips (0.5sec) in traffic flow?!

I'm surprised that you get signal values as high as -5 dBm. My maximum is about 
-35. I'm usually in 
the -40 range, even at 2 m from the AP.

> With the patch applied power is reported as 27dB in debugfs. With 
> debug_xmitpower dmesg reports desired power to be 16.5 and actual 16.25. This 
> is max when I manually set power through debugfs. After a while it's down to 
> 10dB, even though only 1M works where I sit.
> Range seems to be higher for B-rates. Maybe this is just how things are, I 
> lack experience.

The CCCK (B) encoding is much different than OFDM (G) transmissions. I would 
not be surprised to 
learn that its range were longer.

The power setting that comes from mac80211 is 27 dBm, which is completely bogus 
for what is supposed 
to be the FCC table. The regulatory limit is 20 dBm EIRP (a fancy acronym that 
means take the 
antenna into account). I've sent a fix for comment, but as is the usual case 
for mac80211, it will 
take several days or weeks to get a response. The maximum power that a bcm43xx 
device can use is 
encoded in the sprom. For most of them that quantity is 18.5 dBm, corresponding 
to the regulatory 
limit of 20 minus a safety factor of 1.5. I think that is there to prevent 
setting the power too 
high and flunking the certification tests. The output that goes to the radio is 
thus 18.5 less the 
gain of the antenna, which is also in the sprom with a usual value of 2 dBm. 
That is why you see the 
code setting a Desired power of 16.5 dBm.

Initially, I thought that the performance of my BCM4311 fell off as the power 
increased; however, 
that no longer happens. As a result, we can push full power at all times and 
there seems to be no 
need to use the kind of algorithm that you were testing. Don't tell the FCC, 
but we could relax that 
upper power limit as we will never try to get the device certified, but then we 
would use extra 
power, and run the risk of burning out the radio. If you decide to do that, 
please tell me the power 
setting at which it fried!

With the patches that were pushed into wireless-dev a few minutes ago, I 
suggest that you try 
bcm43xx-mac80211. It is getting at least as good, if not better, performance 
than the BCM4301 or the 
softmac port to mac80211 drivers do. We would also appreciate as much testing 
as possible as it will 
help getting it merged into mainstream. That driver will require V4 firmware.

Thanks for your report,

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