Need help with configuration of Timeslots and of multible USRPs

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Holger Hans Peter Freyther holger at freyther.de
Mon Jul 7 20:00:21 UTC 2014


On Mon, Jul 07, 2014 at 01:39:06PM +0200, Norbert Englberger wrote:
> Hello everybody,

Hi,

> 
> 1. The students told me, that OpenBSC doesn't behave like all the BTS from
> commercial Providers they analysed:
> The say that on commercial nets at the beginning of a phone call there will
> be send an "Immediate assignment" sending the MS always to a SDCCH on TS 1
> or TS2 where the encryption will be startet. After establishing the
> encryption another "Immediate assignment" will occour and send the MS to a
> Traffic Channel (which also contains the FACCH / SACCH) for the actual
> Communication.
> OpenBSC also sends the "Immediate assignment" on TS0 but sends the MS
> directly to Timeslot with a Traffic Channel where all the signalling, like
> encryption, will be done in the SACCH.
> Is there any way to configure OsmoBSC to behave like the commercial BTS the
> students described?

it is not a question of BTS but the BSC. The role of the BSC is to manage
the channels. Inside src/libbsc/gsm_04_08_utils.c you will see a table
that determines how the BSC/NITB will respond to "channel request" inside
the RACH request by the phone.

E.g. if you change get_ctype_by_chreq to always return LCHAN_SDCCH you
should be close to the behavior you have described.





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