Telecom_gprs-attach_detach_procedure.pdf

Data Call flow

1. GPRS Attach/Detach GPRS Attach/Detach
Shengyao Chen
Lecturer: Dr. Cornelia Kappler
UMTS Network WS 2003/2004
Technical University Berlin
1. Overview
2. GPRS Attach/Detach in the Overall Picture
3. Signaling by GPRS Attach
4. Signaling by GRPS Detach
5. Who knows what?

2. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 21. Overview
1.1.
GPRS Attach/Detach -Registration/Cancelation of the UE
by SGSN in PS-Domain
IMSI Attach/Detach - Registration/Cancelation of the UE
by MSC/VLR in CS-Domain
1.2.
GPRS Attach/Detach
A connection (MM context) between UE and SGSN (CN), HLR and
EIR can be involved. PMM states by UE and SGSN change:
PMM
idle
PMM
connected
PMM
detached
UE
PMM
idle
PMM
connected
PMM
detached
SG
SN
Other-
wise
Data transfer
After GPRS Attach Before
GPRS
Attach
UE RNS SGSN
HLR/AuC EIR
GGSN
MM context
PDP context

3. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 31. Overview 1.3. Protocol stack
UE
RNS
SGSN
HLR / EIR
GMM
RRC
RLC
MAC
PHY
RRC
Signalling
Bearer
SCCP
PHY
MAC
RLC
Relay
RANAP
L1
L2
Signalling
Bearer
SCCP
RANAP
L1
L2
Signalling
Bearer
SCCP
TCAP
Signalling
Bearer
SCCP
TCAP
GMM MAP MAP
Uu Gr/CfIu-PS

4. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 42. GPRS Attach/Detach in the Overview Picture
IMSI Attach in CS-Domain
GPRS Attach in PS-Domain
Attachment in CN
Data transmission via PDP context
LA/RA update, Intra/Inter SGSN relocation etc.
IMSI Detach in CS-Domain GPRS Detach in PS-Domain
Detachment in CN
Create a list of suitable cells, select the best cell Select a suitable cell
Select a suitable PLMN according to a preference
list stored on the USIM
Read system information in BCCH
(BCH, P-CCPCH)
Read CPICH in order to get
scrambling code
Frame synchronisation
Time slot synchronisation Scan all
possible
frequencies,
select the
initial cell,
get system
information
e.g. PLMN-ID
Select a suitable
PLMN

5. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 53. Signaling by GPRS Attach 3.1. Overview GPRS Attach is initiated by UE and has 3 phases:
1.
Request over RRC:
Establish RRC connection between UE and RNC.
A Request of a GPRS-Attach initiated by UE will be sent to
SGSN.
2. Authentication and encryption:
SGSN authenticates the identity of the user and equipment.
Data exchange will be ciphered.
3. SGSN address will be registrated in HLR.
SGSN gets the services which the UE can use from HLR
(Authorization).
UE gets the P-TMSI.

6. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 63. Signaling by GPRS Attach –
3.2. Signaling flows
UE RNS SGSN HLR EIR
RRCconnection
Activate ciphering
GMMAttach request (IMSI)
MAPsend authenication info (IMSI)
MAPsend authenication info ACK (Vector)
GMM authentication and ciph. request
GMM authentication and ciph. response (RES)
3
2
1
GMM indentity request
GMMindentity response (IMEI)
MAPcheck IMEI (IMEI)
MAPcheck IMEI ACK (IMEI, status)
MAPupdate GPRS location (IMSI)
MAPinsert subscriber data
MAP insert subscriber data ACK
MAPupdate GPRS location ACK
GMM Attach accpet (P-TMSI)
GMMAttach complete

7. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 73. Signaling by GPRS Attach 3.3. GPRS Attach may be denied
a) by SGSN when:
IMSI is invaild, GPRS Attach request will be
rejected by HLR.
IMEI is invalid, GPRS Attach request will be
rejected by EIR.
Both cases will suspend the USIM card –
Registration later impossible
b) by UE when:
PLMN is “forbidden” in USIM: e.g. no roaming
agreement between HPLMN and this PLMN,
the UE not allowed to switch PLMNs.
LAI is “forbidden” in USIM.
No RRC connection will be started.
USIM
IMEI
IMSI
MSISDN
P-TMSI
RA
KSI (IK,CK)
...
UE

8. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 84. GRPS Detach 4.1. Overview
GPRS Detach can be initiated explicitly by UE or SGSN,
or implicitly by CN without notifying the UE.
PDP context may be canceled between UE and CN.
User data will be deleted by SGSN.
RRC connection will be released.
PMM states of UE and SGSN change to PMM detach.
HLR can be updated later (Purge function).

9. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 94.2. Signaling by GPRS Detach initiated by UE 4. GPRS Detach
UE RNS
SGSN HLR
GGSN
GMMDetach request (P- IMSI)
GMMDetach request (P- IMSI)
PS signalling Connection Release
MAPPurge UE
GTP-C Delete PDP context Response
GTP-C Delete PDP context Request
MAPPurge UE ACK

10. 12.02.2004 UMTS WS03/04 GPRS Attach/Detach Shengyao Chen 10
Information stored before and after GPRS Attach for one UE 5. Who knows what?
SGSN address PMM State
P-TMSI
MSISDN
RA
KSI(IK,CK)
QoS profile
PMM State
P-TMSI
After GPRS
Attach
IMSI
MSISDN
KSI(IK,CK)
QoS profile
IMSI
MSISDN
RA
KSI(IK,CK)
QoS profile
Before
GPRS
Attach
HLR SGSN UE