Re: [Openbts-discuss] GPRS Attach issue

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Hi,

After some configuration and code tweaking, the GPRS modem is still not
able to attach to GPRS network (Short Message Service and calls are
working).
By studying the code and the logs I got, I found out that this modem is
performing the Attach Request with its IMSI as the mobileId :

Feb 4 16:41:21 client5 openbts: INFO 6529:6670 2015-02-04T16:41:21.8
Sgsn.cpp:1053:handleL3GmmMsg: SGSN:Received AttachRequest mAttachType=1
MOBILEID= IMSI=00101641604**** addtionalMobileId=not present drx=1282
tmsiStatus=0 pdpContextStatus=PdpContextStatus=0,0
mCypheringKeySequenceNumber=7 oldRaId=MCC=001 MNC=01f LAC=65534 RAC=45
mOldPtmsiSignature=0 mRequestedReadyTimerValue=0
mMsNetworkCapability=ByteVector(size=1 data: e4)#012
MsRaCapability[GSM_850]=( GPRSMultislotClass=10
GPRSExtendedDynamicAllocationCapability=0)#012 MsRaCapability[GSM_E]=(
GPRSMultislotClass=10 GPRSExtendedDynamicAllocationCapability=0)#012
MsRaCapability[GSM_1800]=( GPRSMultislotClass=10
GPRSExtendedDynamicAllocationCapability=0)#012
MS#2,TLLI=78c32f1b,c00d7002 imsi=00101641604****

It makes a difference with all the working devices I've tested so far,
as they perform the Attach Request using a PTMSI :

Feb 4 16:33:41 client5 openbts: INFO 6529:6670 2015-02-04T16:33:41.6
Sgsn.cpp:1053:handleL3GmmMsg: SGSN:Received AttachRequest mAttachType=1
MOBILEID= (P)TMSI=0XE9003 addtionalMobileId=not present drx=2050
tmsiStatus=0 pdpContextStatus=PdpContextStatus=0,0
mCypheringKeySequenceNumber=7 oldRaId=MCC=001 MNC=01f LAC=543 RAC=45
mOldPtmsiSignature=0 mRequestedReadyTimerValue=0
mMsNetworkCapability=ByteVector(size=2 data: f4 00)#012
MsRaCapability[GSM_E]=( GPRSMultislotClass=4
GPRSExtendedDynamicAllocationCapability=1)#012
MsRaCapability[GSM_1800]=( GPRSMultislotClass=4
GPRSExtendedDynamicAllocationCapability=1)#012 MS#1,TLLI=800e9003

I don't really understand why the modem sends an IMSI before we ask for
it, instead of sending its previously used PTMSI.
Is this kind of situation handled in OpenBTS ? 

Best Regards,

Le 2015-01-30 09:00, Pierre Baudry a écrit :
> Hello,
> 
> I am currently having some trouble to get a specific GPRS M2M modem
> attached to an OpenBTS GPRS network
> 
> From what I've observed so far, It seems that either:
> * the ME never receives the GPRS Attach Accept from the BTS.
> * the GPRS Attach Accept never makes it out of the radio (it is sent
> out by SGSN)
> * the ME never sends the GPRS Attach Acknowledgement (AttachComplete).
> * the GPRS Attach Acknowledgement never arrives at SGSN (although no
> further GPRS messages such as ActivatePDPContextRequest seem to be
> received either)
> 
> 
> (Seen with SGSN debug logs, GPRS TAP trace, and a trial of OpenBSC tools)
> 
> This specific GPRS modem works well with commercial networks.
> 
> You can find a piece of SGSN debug logs for both modems attached in
> this mail. Notice that for the working modem, an Identity Request is
> sent before the Attach Accept packet is sent
> 
> Here is what I got from the command 'gprs list ms -cxv' during the
> attach process
> 
> MS#11,TLLI=800d0001 rrmode=PacketIdle Bytes:125up/57down Utilization=0%
> GMM Context: imsi=00101303099**** ptmsi=0xd0001
> tlli=0xc00d0001 state=GmmDeregistered age=2208 idle=1963 IPs=none
> MsRaCapability[GSM_850]=( RFPowerCapability=4 A5Bits=64
> ESInd=1 PS=0 VGCS=0 VBS=0 GPRSMultislotClass=10
> GPRSExtendedDynamicAllocationCapability=0)
> MsRaCapability[GSM_E]=( RFPowerCapability=4 A5Bits=64 ESInd=1
> PS=0 VGCS=0 VBS=0 GPRSMultislotClass=10
> GPRSExtendedDynamicAllocationCapability=0)
> MsRaCapability[GSM_1800]=( RFPowerCapability=1 A5Bits=64
> ESInd=1 PS=0 VGCS=0 VBS=0 GPRSMultislotClass=10
> GPRSExtendedDynamicAllocationCapability=0)
> TimingError=(1.28 min=-1.05 max=1.91 avg=0.79 N=53) RSSI=(-24
> min=-48 max=-21 avg=-35.45 N=53) CV=(27 min=27 max=31 avg=30.00 N=6)
> ILev=(0) RXQual=(0) SigVar=(0
> ) ChCoding=(3 min=0 max=3 avg=2.20 N=60)
> dataER:.0% (331) recent:0% (0) tbfER:.4% (12)
> rrbpER:.5% (27) recent:0% (0) ccchER:1.0% (94) recent:1.0%
> (30) low:1.0% (2)
> 
> 
> I noticed that another GPRS M2M modem of the same brand (Cinterion),
> that _does_ work with our current setup, I get some differences in
> capabilities :
> 
> MS#2,TLLI=c00c8001,800d0004 rrmode=PacketIdle Bytes:106up/86down Utilization=0%
> GMM Context: imsi=00101303099**** ptmsi=0xc8001
> tlli=0xc00c8001 state=GmmRegisteredNormal age=17 idle=2
> IPs=192.168.99.1
> MsRaCapability[GSM_E]=( RFPowerCapability=4 A5Bits=64 ESInd=1
> PS=1 VGCS=0 VBS=0 GPRSMultislotClass=4
> GPRSExtendedDynamicAllocationCapability=1 SMS_VALUE=7 SM_VA
> LUE=5)
> MsRaCapability[GSM_1800]=( RFPowerCapability=1 A5Bits=64
> ESInd=1 PS=1 VGCS=0 VBS=0 GPRSMultislotClass=4
> GPRSExtendedDynamicAllocationCapability=1 SMS_VALUE=7 SM
> _VALUE=5)
> TimingError=(0.18 min=-0.78 max=1.59 avg=0.16 N=204)
> RSSI=(-63 min=-63 max=-61 avg=-62.81 N=204) CV=(50 min=47 max=51
> avg=49.43 N=7) ILev=(0) RXQual=(0) SigVar=
> (63) ChCoding=(0)
> dataER:.7% (68) recent:.7% (55) low:.8% (38) tbfER:.14% (7)
> rrbpER:.3% (35) recent:.4% (30) low:1.0% (6) ccchER:0% (0)
> recent:0% (0)
> 
> The differences I see are:
> * No GSM_850 capabilities (advertised?) in the modem that does work.
> * PS=0 (pseudo-synchronisation) on the modem that does _not_ work, vs. PS=1
> * GPRSExtendedDynamicAllocationCapability=0 on the modem that does
> _not_ work, vs. GPRSExtendedDynamicAllocationCapability=1
> 
> Do you know if this modem not being able to perform an extended
> dynamic allocation (according to the uplink packet resource request)
> can prevent it from attaching to GPRS ?
> The same goes for PS (pseudo-synchronisation)
> Have you ever encountered this kind of situation, or have any idea
> where to look for problems?
> 
> Best Regards,
> 
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Re: [Openbts-discuss] GPRS Attach issue

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Re: [Openbts-discuss] GPRS Attach issue