[Ns-developers] sta does not receive probe response (from wifi scanning patch)

[Gustavo Carneiro]

2009/2/3 ichrak amdouni <ichrak.amdouni at gmail.com>

> Hi all,
> I am  using ns3.3 and I have adapted the wifi scanning patch (
> http://code.nsnam.org/gjc/ns-3-wifi-scanning/rev/d84735b462a8) that
> Gustavo
> provided for ns3.2 version.
> In the scanning procedure, after switching from a channel to another,  the
> station successfully sends probe requests, APs receive the probe and send
> probe response, but  the station never receive the probe response from the
> AP.
> The issue  is that at the physical layer, station drops packet because
> 'already in Syn'.
> Even if I use a unique channel for all nodes (but still calling
> SetChannel()), I have always the same behavior.
> If the station does not change the channel, it receives correctly the probe
> response.
> Does anyone has an explanation for this.
> thank you in advance.
>

Sorry for the delay, but I couldn't think of any answer before.

I just noticed on my own tests that if you have multiple nodes trying to
scan at the same time some wifi problem (bug or natural, I am not sure)
occurs due to the synchronization.  Try adding a small random delay to the
scheduled event that starts the scanning; it will probably solve your
problem.  It's ok to do this because in the real world independent mobile
terminals do not usually do things so synchronized.

Hope this helps.

-- 
Gustavo J. A. M. Carneiro
INESC Porto, Telecommunications and Multimedia Unit
"The universe is always one step beyond logic." -- Frank Herbert