Frequency lock problem with WDS

Joe Parks jphstap at roinet.com
Mon Jun 23 16:10:47 EDT 2003


The cards I use normally are high power cards, but I've managed to get the same results from various low power cards as well.   I've discussed the issue with the card manufacturer and while they can't say for certain, they suspect that the driver is allowing the tuner to behave in a "promiscuous" way.

I've also noticed significantly lower throughput (18% or more) for a WDS connection on channel 1 when another connection, even on channel 11, is active nearby.  ("Nearby" can be as far away as 20 feet, I haven't tested further than that).  I was under the impression that the guard band between those channels should be enough to avoid that sort of thing.   

On 2003.06.23 15:07, Dave wrote:
> Hello Joe,
> 
> 
> Could it be the cards you are using are pretty high powered? I have
> experienced the same thing but I don't consider this a problem or an
> issue...I think it is by design that although you select channel 1 or
> channel 6 as the center of the frequency that you will see RF on surrounding
> channels depending on how powerful your card is (tx) and how high the
> receive sensitivity is.
> 
> I could very well be wrong...
> 
> 
> 
> -Dave
> 
> 
> 
> > Something is *UP* with WDS.   It is as if the radio is not "locked" on the
> proper frequency or something.   I can't explain this, and I suspect it is
> leading to throughput problems.   Give it a try though.  It's quite amazing.
> >
> > This test demonstrates that radios tuned to and transmitting on different
> channels are somehow able to communicate with one another despite how
> improbable that sounds.
> >
> > Setup:  2 computers with radio cards running hostap driver.   (any version
> that supports WDS)
> >
> > On computer A issue the following commands:
> >
> > iwconfig wlan0 essid "crosstest"
> > iwconfig wlan0 mode master
> > iwconfig wlan0 channel 6
> > iwpriv wlan0 prism2_param 14 1
> > iwpriv wlan0 prism2_param 8 1
> >
> > Likewise, issue the following commands on computer B:
> >
> > iwconfig wlan0 essid "crosstest"
> > iwconfig wlan0 mode master
> > iwconfig wlan0 channel 1
> > iwpriv wlan0 prism2_param 14 1
> > iwpriv wlan0 prism2_param 8 1
> >
> > If the computers are sufficiently close together (within a few feet of
> each other this always works) they will quickly form a WDS connection with
> one another.
> >
> > You can see this connection listed with:
> >
> > cat /proc/net/hostap/wlan0/wds
> >
> > On each machine an interface wlan0wds0 will now exist that you can bind an
> IP address to.
> >
> > On computer A:
> > ifconfig wlan0wds0 192.168.6.1
> >
> > On computer B:
> > ifconfig wlan0wds0 192.168.6.2
> >
> > Try some pings. This will confirm that data is actually flowing through
> this "Cross-Channel" connection.
> >
> > If you try this test with different channel arrangements you should see
> that the 'closer' the channels are in frequency to one another, the further
> apart the computers can be and still establish a working WDS connection.
> > _______________________________________________
> > HostAP mailing list
> > HostAP at shmoo.com
> > http://lists.shmoo.com/mailman/listinfo/hostap
> >
> 
> 



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