RBS 2308 Protocol Error

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Labs rp.labs at gmx.ch
Thu Dec 1 23:41:55 UTC 2016


Hello Csaba,

On 12/1/16 11:25 PM, Sipos Csaba wrote:
> Hi,
> 
> Maybe its not completely related, but my experience with Nokia Site is to use full E1 timeslots (64kbit) for RSL and OML signalling, otherwise it is not working, and this is not a Nokia limitation.
> 

Nokia did a different implementation on Abis. I'm hoping to get a Nokia
soon and play with it.

> Just try using:

I can't try it because I don't have a PCM based Ericsson but an IP based
one and I really don't know how to make the openbsc.cfg for that one
since I couldn't find anything in the wiki for it. I was trying to help
Caleb and also understand the OM2000. I worked previously on RAN part
with E/// and we integrated this RBSes with real BSCes and according to
my notes E/// is not using full PCM timeslots (64kbit) exactly. They
have 3 types of LDAP configurations for their Abis to RBS.

- Unconcentrated LAPD
For E1 they leave the full timeslot 0 free for synchronization and
utilize timeslots 1-31. In this mode they use a full timeslot for
signaling to TRU (TRXC) and 2 other full timeslots submultiplexed each
in 4x 16kbit for voice and data. OML(CF) is not mentioned specifically
but it says "TRXC-0 and CF goes together on the same timeslot". The E///
naming TRH (Transceiver Handler) says that is handling all LAPD
signaling, signaling BTS to MS and O&M (CF). For T1 lines there is not
synchronization timeslot used and sync is done from the overall T1 line
so T1 config should start with "timeslot 0".

- Concentrated LAPD
Recommended for 3 or more TRUs. Here TS0 64kbit is for synchronization
in E1 links, TS1 is used as 4x16kbit signaling for the first 4 TRXes,
TS2-9 submultiplexed each in 4x16kbit for traffic, TS10 again 4x
signaling,etc. For T1 the same but no TS0 so config starts with TS0 for
4x signaling links for the first 4 TRXes. Since in this mode you need
also configuration for CON the CF(OML) is added by CON to the same
timeslot as the first 4x TRXes that means TS1.

- Multiplexed LAPD
This is used for small cells and here I made the mistake in my previous
mail saying is "Unconcentrated". This type of config multiplexes TRX
signaling + CF(OML) + BCCH/CCCH + SDCCH8 in one full 64kbit timeslot and
on the second timeslot keeps 2x 16kbit subrates spare.

So in the end I am still not sure how the config should look like to
have a PCM based RBS working with OpenBSC.

> And don't forget to configure the BTS Abis allocation accordingly!
> 
> Also for DAHDI, you will need to use the correct config with CCS signalling. This is an example for the system.conf for an E1 based BTS:
> 
> span=1,0,0,ccs,hdb3,crc4    
> bchan=1-31
> 

Thanks for config.

> Regards,
> Csaba
> 

Regards,
Razvan



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