OpenBTS with GPRS....trouble with SGSN and PCU

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altaf sk altaf329 at gmail.com
Tue Jun 4 09:57:55 UTC 2013


Hello everybody.

I was successful in running the calypso BTS by using the openBTS (without
gprs).


Now I am trying to setup a GPRS N/w with the guide provided at
http://wush.net/trac/rangepublic/wiki/GPRS  and by using the same Calypso
BTS. Want to know whether if this can work out. If not I want to do some
minimal implementation (GPRS attach or just activate a PDP context).

I followed the tutorial and I am here with logs from PCU and SGSN.

LOG from Osmo-PCU

# ./osmo-pcu -n 06 -m 234
<0001> pcu_l1_if.cpp:375 BTS available
<0001> pcu_l1_if.cpp:91 Sending activate request: trx=0 ts=6
<0001> pcu_l1_if.cpp:502 PDCH: trx=0 ts=6
<0001> pcu_l1_if.cpp:91 Sending activate request: trx=0 ts=7

<0001> pcu_l1_if.cpp:502 PDCH: trx=0 ts=7
<0009> gprs_bssgp_pcu.cpp:508 NS-VC 4 is unblocked.
<0008> gprs_bssgp_pcu.cpp:549 Sending reset on BVCI 0
<0008> gprs_bssgp_pcu.cpp:557 Sending reset on BVCI 7
<0008> gprs_bssgp_pcu.cpp:565 Sending unblock on BVCI 7

<0001> pcu_l1_if.cpp:296 RACH request received: sapi=1 qta=1, ra=120,
             fn=961674
<0002> gprs_rlcmac_data.cpp:1901 Got IMM.ASS confirm, but rest octets
            do not start with bit sequence 'HH01' (Packet Downlink
Assignment)
0002>  gprs_rlcmac_data.cpp:564 TBF T3169 timeout during transsmission
<0002> gprs_rlcmac_data.cpp:82 - Assignment was on CCCH
<0002> gprs_rlcmac_data.cpp:88 - No uplink data received yet


<0001> pcu_l1_if.cpp:296 RACH request received: sapi=1 qta=1, ra=124,
            fn=963005
<0002> gprs_rlcmac_data.cpp:1901 Got IMM.ASS confirm, but rest octets
            do not start with bit sequence 'HH01' (Packet
DownlinkAssignment)
0002> gprs_rlcmac_data.cpp:564 TBF T3169 timeout during transsmission
<0002> gprs_rlcmac_data.cpp:82 - Assignment was on CCCH
<0002> gprs_rlcmac_data.cpp:88 - No uplink data received yet

After a successful GSM attach procedure the phone is accessing the BTS on
RACH for a GPRS attach.
This set of statements repeats as long as the phone trying to do a GPRS
attach send requests on RACH. It seems like the phone BTS receives RACH and
a channel is assigned (IMM ASS, I can see this TBF assignment in
Wireshark), but I doubt whether this IMM ASS has reached the phone that is
trying to GPRS attach.


Log from SGSN

#./osmo-sgsn
<0010> gprs_ns.c:171 NSVCI=65534 Creating NS-VC
<0010> gprs_ns.c:171 NSVCI=65535 Creating NS-VC
<0010> gprs_ns.c:806 Creating NS-VC for BSS at 192.168.111.144:5948
<0010> gprs_ns.c:679 NSEI=65535 Rx NS RESET (NSVCI=0, cause=O&M
intervention)
<0010> gprs_ns.c:538 NSEI=8 Tx NS RESET ACK (NSVCI=4)
<0010> gprs_ns.c:679 NSEI=4 Rx NS RESET (NSVCI=8, cause=PDU not compatible
with protocol state)
<0010> gprs_ns.c:538 NSEI=8 Tx NS RESET ACK (NSVCI=4)
<0010> gprs_ns.c:865 NSEI=8 Rx NS UNBLOCK
<0010> gprs_ns.c:865 NSEI=8 Rx NS UNBLOCK
<0011> gprs_bssgp.c:249 BSSGP BVCI=0 Rx RESET cause=O&M intervention
<0011> gprs_bssgp.c:249 BSSGP BVCI=7 Rx RESET cause=O&M intervention
<0011> gprs_bssgp.c:272 Cell 234-6-1000-0 CI 0 on BVCI 7
<0011> gprs_bssgp.c:344 BSSGP BVCI=7 Rx BVC-UNBLOCK
<0011> gprs_bssgp.c:747 BSSGP BVCI=7 Rx Flow Control BVC
<0011> gprs_bssgp.c:747 BSSGP BVCI=7 Rx Flow Control BVC

and The last statement repeats.........

the statement
Cell 234-6-1000-0 CI 0 on BVCI 7
The RAI and Cell ID are 0 and 0.... But when I read the code gprs_bssgp.c
it says these parameters will be received from BSS. If I set these
parameters in OpenBTS.db similar to LAC=RAC but still there is no effect.


I am running ./ggsn, ./osmo-sgsn, ./osmo-pcu, ./openbts

Is osmo-nitb needed along with SGSN and PCU.

I fail to do GPRS attcach in this situation. Can someone please give your
comments and guide me with some suggestions.


regards,

Altaf
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