layer23 bursts - strategy for filtering IA's for tmsi based on downlink traffic only?

Mad mad at auth.se
Wed Feb 23 14:34:09 UTC 2011


 On Wed, 23 Feb 2011 09:53:34 +0000 (GMT), MATTHEW EVANS wrote:

>
> I am running some tests/experiments with the burst_ind branch. I want
> to be able
> to only follow the immediate assignments for my TMSI as it is 
> difficult to
> verify that the bursts are indeed my traffic. However, I suspect this 
> is not
> possible using only downlink traffic as without the channel request
> from the MS
> I cannot match the resulting IA? I would need to capture uplink too?
>

 Even if you would capture the uplink on the RACH you would not be able 
 to
 distinguish your phones request using your tmsi because IAs refer to 
 requests by
 their Random Reference (04.08, 9.1.8). Only if you knew this reference 
 you could
 follow only your phones DCHs. The first time a tmsi/imsi may be sent is 
 on an
 already established DCH.
 Of course you could still implement something that only if a RACH 
 request is
 received on uplink the IA is followed, so you could be sure to follow 
 only
 requests from phones in your vicinity.

 Regards,
   Mad




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