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csaba, 02/19/2016 10:47 PM


OpenBSC is currently supporting the Site family of Nokia BTSes.

'''Things that work:'''

- Nokia InSite and MetroSite units are proven to be working, UltraSite is probably working
- Full Rate and Enhanced Full Rate voice calls (MO & MT)
- SMS (MO & MT)
- Cell reselection
- Handover (please see this patch: [http://cgit.osmocom.org/openbsc/commit/?id=7d8fa3418ff6c589eba10e562da8b96995e19f7a] )

'''Handover:'''

The OpenBSC side of the handover logic works quiet well. But at the moment, there is a slight problem with the Nokia units. The handover decision is made correctly, the GSM phone is commanded to switch to the new channel on the new BTS, which the phone does. But despite the channel release is sent, the old channel never get released, and this leads to a Radio Link Failure.

Update: it seems that the root cause of the previous handover failure is that the InSite BTSes (probably others too) are not sending the channel release ACK to the BSC after the old channel release is requested by the BSC. Andreas Eversberg added a patch which overcomes this problem by implicating the missing ACK, so the BSC can continue and finish the handover process. This can be enbaled by adding the next line to the BTS part of the config file:

{{{
nokia_site no-local-rel-conf 1
}}}

This fix is tested on Nokia InSite and MetroSite units, all of them are performing handovers normally.

For more info, please see this patch: [http://cgit.osmocom.org/openbsc/commit/?id=7d8fa3418ff6c589eba10e562da8b96995e19f7a]

'''E1 cards:'''

The original Nokia support was written for HFC-E1 and mISDN. The Site can only be interfaced via traditional E1 lines (no IP ABIS support for these old units). It is also possible to use a DAHDI card to interface with the BTS. For this you have to use the following configuration in /etc/dahdi/system.conf:

{{{
span=1,0,0,ccs,hdb3,crc4
bchan=1-31
}}}

Unlike in traditional E1 communication, we are using CCS signalling. For every signalling and traffic channel between the BTS and the BSC, we are using dedicated timeslots. Because of that, we are no longer need any shared signalling channel on the E1 line (e.g. D channel on timeslot 16.

'''Example config file for an 1800MHz Nokia InSite unit:'''

{{{
!
! OpenBSC configuration saved from vty
! !
password foo
!
line vty
no login
!
e1_input
e1_line 0 driver dahdi # e1_line 0 port 0
log file /root/900_nokia.log
logging filter all 1
logging color 1
logging timestamp 1

network
network country code 1
mobile network code 1
short name OpenBSC
long name OpenBSC
neci 0
rrlp mode none
mm info 1
handover 0
handover window rxlev averaging 5
handover window rxqual averaging 1
handover window rxlev neighbor averaging 5
handover power budget interval 6
handover power budget hysteresis 3
handover maximum distance 9999
timer t3101 3
timer t3103 5
timer t3105 20
timer t3107 10
timer t3109 15
timer t3111 2
timer t3113 10
timer t3115 0
timer t3117 0
timer t3119 0
timer t3141 0
timer t3122 10

bts 0
type nokia_site
band GSM1800
cell_identity 1
location_area_code 1
base_station_id_code 63
training_sequence_code 7
ms max power 12
cell reselection hysteresis 4
periodic location update 10
nokia_site skip-reset 0
nokia_site no-local-rel-conf 1
oml e1 line 0 timeslot 8 sub-slot full
oml e1 tei 1
trx 0
arfcn 885
nominal power 18
max_power_red 10
rsl e1 line 0 timeslot 7 sub-slot full
rsl e1 tei 1
timeslot 0
phys_chan_config CCCH+SDCCH4
e1 line 0 timeslot 5 sub-slot 0
timeslot 1
phys_chan_config SDCCH8
e1 line 0 timeslot 5 sub-slot 1
timeslot 2
phys_chan_config TCH/F
e1 line 0 timeslot 5 sub-slot 2
timeslot 3
phys_chan_config TCH/F
e1 line 0 timeslot 5 sub-slot 3
timeslot 4
phys_chan_config TCH/F
e1 line 0 timeslot 6 sub-slot 0
timeslot 5
phys_chan_config TCH/F
e1 line 0 timeslot 6 sub-slot 1
timeslot 6
phys_chan_config TCH/F
e1 line 0 timeslot 6 sub-slot 2
timeslot 7
phys_chan_config TCH/F
e1 line 0 timeslot 6 sub-slot 3

}}}

'''LMP cable pinout for InSite units:'''

'''LMP cable pinout for MetroSite units:'''

'''Tips and tricks for Site family and OpenBSC:'''

'''RESET Timer:'''

The Nokia part of the OpenBSC code contains a fixed reset timer, which is set to 15 seconds by default. Every time you start a BTS, OpenBSC first resets (actually restarts) the unit, and only configures and starts the BTS after that. The reason behind this, is if you change the radio parameters of the BTS (ARFCN, CID, BSIC, TSC, TX power etc.), these parameters are not going to change on the BTS if this resets is skipped.

This 15 seconds is working well in general, but in some cases you need to raise this parameter (eg. to force OpenBSC to wait more for the BTS to restart). For example: if you use more than one unit on the same E1 (InSite units daisy chained via the internal HDSL interface), or MetroSite units daisy chained via the E1 cross connector TRE unit.

This parameter can be modified in the source code of OpenBSC at openbsc/openbsc/src/libbsc/bts_nokia_site.c

{{{
#define RESET_INTERVAL 15, 0 /* 15 seconds */
}}}

Try 20 or 23 instead of 15. Example: for a HDSL cascaded two BTS InSite setup, I needed to raise this parameter to 20 seconds.

After the modification of this parameter, you need to recompile OpenBSC!

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