LAC 0 / paging to all BTS

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Holger Freyther zecke at selfish.org
Wed Sep 30 11:37:42 UTC 2009


On Wednesday 30 September 2009 13:23:10 Harald Welte wrote:
> Hi Zecke,
> 
> I've been reviewing some of your patches:
> > commit 45f9b3d3fc47074652be951eb74df2b0be2a230f
> > Author: Holger Hans Peter Freyther <zecke at selfish.org>
> > Date:   Fri Aug 21 05:30:19 2009 +0200
> >
> >     [paging] Use one of the two reserved LAC to page every BTS
> >
> >     For the on-waves.com MSC case we want to page every BTS reached
> >     of the network. Our gsm_subscriber entry does not have a LAC
> >     entry set and defaults to zero. Use the reserved 0x0000 to
> >     indicate that we want to use every bts in the network.
> >
> >     This will influence the paging code to start and stop paging.
> 
> The problem is that in the current code, we use LAC == 0 to indicate that
>  the subscriber has sent an IMSI DETACH message, i.e. switched his phone
>  off.
> 
> You are now redefiniing the LAC 0 to something like the opposite case,
>  which I don't particularly like.  Is there some alternative solution?

I didn't think about the IMSI DETACH case. One easy alternative is to use the 
other reserved lac value. With the least significant bit set 0 and all others 
to 1 (so 0xfffe... ETSI always makes me unsure about it).

The other option is changing gst_bts_by_lac to specify to not filter by lac but 
just give the next one.

what do you think?
	z.




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