N protocol on 802.11a freq signal strength

N protocol on 802.11a freq signal strength

[Jack Howarth]

    After replacing my Linksys WRT150N wireless router with an
Apple Airport Extreme Gigabit ethernet wireless router, configured
for using the N protocols on the 802.11a wireless frequencies, I
can confirm that the ath9k git from last week connects to this
configuration. I have noticed one oddity though. The reported
signal strength (in the NetworkManager menu bar icon) is significantly
lower than that shown under Mac OS X 10.5. Also, I notice under Mac OS X
10.5, by holding the option key on the Finder's Airport icon, that the
transmit speed is 300 Mbps when the MacBook Pro is in the same room as
the wireless router but only 108 Mbps when a couple rooms away. Should
the ath9k report such dynamic changes in transmit speed? Under Mac OS X
that transmit speed changes as I move the portable back and forth
between the two locations. Thanks in advance for any information.
                       Jack
ps I am also using wide channels if it makes any difference.

Re: N protocol on 802.11a freq signal strength

[Luis R. Rodriguez]

On Fri, Aug 8, 2008 at 7:16 AM, Jack Howarth <howarth@bromo.msbb.uc.edu> wrote:
>    After replacing my Linksys WRT150N wireless router with an
> Apple Airport Extreme Gigabit ethernet wireless router, configured
> for using the N protocols on the 802.11a wireless frequencies, I
> can confirm that the ath9k git from last week connects to this
> configuration. I have noticed one oddity though. The reported
> signal strength (in the NetworkManager menu bar icon) is significantly
> lower than that shown under Mac OS X 10.5.

The link quality we report right now should be lower than the real
one. We will enhance this later but rest assured its the same.

> Also, I notice under Mac OS X
> 10.5, by holding the option key on the Finder's Airport icon, that the
> transmit speed is 300 Mbps when the MacBook Pro is in the same room as
> the wireless router but only 108 Mbps when a couple rooms away. Should
> the ath9k report such dynamic changes in transmit speed? Under Mac OS X
> that transmit speed changes as I move the portable back and forth
> between the two locations. Thanks in advance for any information.

Keep in mind 2.6.27 has aggregation disabled right now due to the new
TX MQ changes so you won't be able to get aggregation going for any
11n wireless device. That said, I am not familiar with the Mac OS X
option key thingy to compute throughput. If you can provide technical
details as to how it computes it or where it does this (AP or STA) it
can help.

  Luis

Re: N protocol on 802.11a freq signal strength

[Luis R. Rodriguez]

On Fri, Aug 8, 2008 at 9:49 AM, Luis R. Rodriguez <mcgrof@gmail.com> wrote:
> On Fri, Aug 8, 2008 at 7:16 AM, Jack Howarth <howarth@bromo.msbb.uc.edu> wrote:
>>    After replacing my Linksys WRT150N wireless router with an
>> Apple Airport Extreme Gigabit ethernet wireless router, configured
>> for using the N protocols on the 802.11a wireless frequencies, I
>> can confirm that the ath9k git from last week connects to this
>> configuration. I have noticed one oddity though. The reported
>> signal strength (in the NetworkManager menu bar icon) is significantly
>> lower than that shown under Mac OS X 10.5.
>
> The link quality we report right now should be lower than the real
> one. We will enhance this later but rest assured its the same.
>
>> Also, I notice under Mac OS X
>> 10.5, by holding the option key on the Finder's Airport icon, that the
>> transmit speed is 300 Mbps when the MacBook Pro is in the same room as
>> the wireless router but only 108 Mbps when a couple rooms away. Should
>> the ath9k report such dynamic changes in transmit speed? Under Mac OS X
>> that transmit speed changes as I move the portable back and forth
>> between the two locations. Thanks in advance for any information.
>
> Keep in mind 2.6.27 has aggregation disabled right now due to the new
> TX MQ changes so you won't be able to get aggregation going for any
> 11n wireless device. That said, I am not familiar with the Mac OS X
> option key thingy to compute throughput. If you can provide technical
> details as to how it computes it or where it does this (AP or STA) it
> can help.

OK it just seems its calculated based on the HT params (HT40, short
guard interval) and the rate used. So in your case its probably just
that a lower rate is being used by the rate control algorithm. Is
suspect we'll get better performance at longer distances once ANI is
integrated which is on our TODO list.

  Luis

Re: N protocol on 802.11a freq signal strength

[Jack Howarth]

   FYI, I just noticed that the ath9k branch was added to
the 2.6.27-rc2-git3 kernel release so I guess it will be
in 2.6.27. 
                     Jack

Re: N protocol on 802.11a freq signal strength

[Jack Howarth]

Luis,
   Is there a wiki explanation of aggregation somewhere? As for the
option key trick, when you hold down the option key while clicking
on the Airport menu bar icon in the Finder, the dropdown menu that
displays the available wireless networks is expanded to show detailed
information for the current wireless connection (speed, SN in dB,
channel, etc).
                    Jack

On Fri, Aug 08, 2008 at 09:49:15AM -0700, Luis R. Rodriguez wrote:
> On Fri, Aug 8, 2008 at 7:16 AM, Jack Howarth <howarth@bromo.msbb.uc.edu> wrote:
> >    After replacing my Linksys WRT150N wireless router with an
> > Apple Airport Extreme Gigabit ethernet wireless router, configured
> > for using the N protocols on the 802.11a wireless frequencies, I
> > can confirm that the ath9k git from last week connects to this
> > configuration. I have noticed one oddity though. The reported
> > signal strength (in the NetworkManager menu bar icon) is significantly
> > lower than that shown under Mac OS X 10.5.
> 
> The link quality we report right now should be lower than the real
> one. We will enhance this later but rest assured its the same.
> 
> > Also, I notice under Mac OS X
> > 10.5, by holding the option key on the Finder's Airport icon, that the
> > transmit speed is 300 Mbps when the MacBook Pro is in the same room as
> > the wireless router but only 108 Mbps when a couple rooms away. Should
> > the ath9k report such dynamic changes in transmit speed? Under Mac OS X
> > that transmit speed changes as I move the portable back and forth
> > between the two locations. Thanks in advance for any information.
> 
> Keep in mind 2.6.27 has aggregation disabled right now due to the new
> TX MQ changes so you won't be able to get aggregation going for any
> 11n wireless device. That said, I am not familiar with the Mac OS X
> option key thingy to compute throughput. If you can provide technical
> details as to how it computes it or where it does this (AP or STA) it
> can help.
> 
>   Luis

Re: N protocol on 802.11a freq signal strength

[Luis R. Rodriguez]

On Fri, Aug 8, 2008 at 10:33 AM, Jack Howarth <howarth@bromo.msbb.uc.edu> wrote:
> Luis,
>   Is there a wiki explanation of aggregation somewhere?

Not that I know of, I'm still trying to get myself familiar with it.
Once someone has some time it'd be appreciated we review 11n stuff
here:

http://wireless.kernel.org/en/developers/Documentation/ieee80211/802.11n

> As for the
> option key trick, when you hold down the option key while clicking
> on the Airport menu bar icon in the Finder, the dropdown menu that
> displays the available wireless networks is expanded to show detailed
> information for the current wireless connection (speed, SN in dB,
> channel, etc).

OK but this is on your Mac OS X box using the Atheros hardware? Where
does ath9k come into the picture?

  Luis

Re: N protocol on 802.11a freq signal strength

[Jack Howarth]

Luis,
    Do these numbers make sense? I find that under Fedora 9
with the Linux 2.6.27-rc2-git3 kernel (the first with the
ath9k drivers), I get...

TX-Power 23 dBn
Link Quality 25/100
Signal Level -82 dBm
Noise Level -95 dBm

This compares to under Mac OS X 10.5 which reports an RSSI of -66
at the same location.
                 Jack