Frequency lock problem with WDS

Dave dave at cc0.net
Mon Jun 23 15:07:11 EDT 2003


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.
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>



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