Re: [Madwifi-devel] Channel 36 mystery!

[Benoit P. <ben...@fr...>]

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Good point, but throughput between A and B, as measured by iperf has no
problem. It's only when all nodes are involved that it triggers the
problem. I'll try to reproduce the problem with nodes on my desk to see
what happens.

Regards,
Benoit

sandeep kakumanu a écrit :
> what is the throughput across router A and router B? Maybe there is some
> other user (either 802.11a or some other protocol) on channel 36.
> 
> sandeep
> 
> On Fri, Nov 14, 2008 at 3:56 PM, Benoit PAPILLAULT
> <ben...@fr... <mailto:ben...@fr...>> wrote:
> 
> Hello there,
> 
> I'd like to submit a very strange issue I have doing on field testing.
> The network is very simple : 3 routers
> 
> * router A is indoor with an antenna pointing to router B
> * router B is dual radio, one antenna is pointing to router A and the
> other is outdoor pointing to router C
> * router C is outdoor with an antenna pointing to router B
> 
> Testing is very simple : run an iperf between router A and router C. The
> setup is using channel 36 between A/B and channel 136 between B/C (using
> FR countrycode). Typical throughput is 28 Mbit/s (quite good!).
> 
> However, over a 5 minutes test, throughput can drop to 5 Mbit/s or less
> for few seconds or minutes. It's very random. I noticed that the
> throughput only get back immediately to 28 Mbit/s when ath_calibrate()
> is called. Not all calls to ath_calibrate() have this effect however.
> 
> Tests have been done with madwifi-dfs@r3762 using 0.9.30.13
> <http://0.9.30.13> HAL.
> Following nbd advice, I used the same code but only changed to
> 0.10.5.6 <http://0.10.5.6>
> HAL. It fails since channel 36 is an indoor channel and I use
> "outdoor=1" module parameter. So I switched to channel 100 and
> throughput was OK over a 5 minutes test.
> 
> So, I switched back to 0.9.30.13 <http://0.9.30.13> HAL and channel
> 100 and it was OK
> again. To sum up, all channels were OK except channel 36!
> 
> What could explain such a behavior? I've dumped the ath_info of router
> A/B if needed. Does channel 36 has special requirements? Does the
> calibrate process if specific for channel 36?
> 
> Regards,
> Benoit

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