ps basics

MP000001 GPRS FundamentalGPRS Fundamental
Foreword
GPRS principle is the basic part of the whole system and the later products learning. This slide will help us to understand the GPRS system networking and some important procedure.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
References
Objectives
Upon completion of this course, you will be able to:
Describe the GPRS networking structure
Describe the GPRS mobility management procedure
Describe the GPRS session management procedure
Contents
GPRS Network Structure
What is GPRS?
Why GPRS?
In order to provide the data service out the scope of the fixed network
GPRS network classification
BSS: Base Station Subsystem
SGSN: Service GPRS Support Node
GGSN: Gateway GPRS Support Node
CG: Charging Gateway
BG: Bordering Gateway
SMS-GMSC: Gateway MSC For Short Message Service
SMS-IWMSC: Short Message Service Interworking MSC
SCP: Service Control Point
HLR: Home Location Register
EIR: Equipment Identity Register
Mobility management
The mobility management functions are used to keep track of the current location of an MS within the PLMN or within another PLMN.
Session management
Session Management (SM) function manages the PDP context of MS.
Routing and transfer
SGSN performs routing and forwarding of service data between MS and GGSN.
Charging
Lawful Interception
Session Management (SM) function manages the PDP context of MS.
Routing and transfer
GGSN performs routing and forwarding of service data between MS and internet.
Charging
Dynamic IP allocation
Temporary storage and buffering of GPRS bills
Pre-processing of GPRS bills
Internet/
Intranet
GGSN(B)
DNS
Resolve the APN to a GGSN IP in the PDP active procedure
Resolve the RAI to a SGSN IP in the inter-SGSN RAU procedure
Resolve the RNCID to a SGSN IP in the relocation procedure (UMTS)
347.unknown
348.unknown
349.unknown
350.unknown
351.unknown
352.unknown
User authentication
Providing location information and processing needed in mobility management and routing, for example
Saving and updating user service SGSN number and address
GPRS user location deletion indication
Whether MS is reachable
Contents
Contents
GMM (GPRS Mobility Management)
Function of the Mobility Management
keep track of the current location of an MS within the PLMN or within another PLMN
Subscription data management
MS states management
GMM (GPRS Mobility Management)
2G Network States Transition
Network Transition States - 2G
3G Network States Transition
Attach Procedure
Function
An MS shall perform a GPRS Attach to the SGSN in order to obtain access to the GPRS services.
If the MS is connected via a GSM radio, it shall perform a GSM GPRS Attach procedure
If the MS is connected via a UMTS radio access network, it shall perform a UMTS GPRS Attach procedure
Attach Types
Combined GPRS + IMSI attach (PS + CS attach)
GPRS attach while IMSI attach (PS attach by existing CS attach)
Attach Procedure
Attach Procedure
Attach Procedure
SGSN get subscriber data from HLR
HLR recorded the MS’s serving SGSN number
SGSN and MS create MM context for the MS
MS can request Session Management services
HUAWEI TECHNOLOGIES CO., LTD.
X
X
MM State
Mobility management state, IDLE, STANDBY, READY, PMMDETACHED, PMMIDLE, or PMMCONNECTED.
X
X
X
X
X
X
IMEI
X
X
Cell Identity
Current cell in READY state, last known cell in STANDBY or IDLE state.
X
Cell Identity Age
Time elapsed since the last LLC PDU was received from the MS at the SGSN.
X
Service Area Code
Last known SAC when initial UE message was received or Location Reporting procedure was executed.
X
Service Area Code Age
Time elapsed since the last SAC was received at the 3GSGSN.
X
The VLR number of the MSC/VLR currently serving this MS.
X
X
New SGSN Address
The IP address of the new SGSN where buffered and not sent NPDUs should be forwarded to.
X
X
X
X
Kc
X
2)
CKSN
X
2)
1)
X
All rights reserved
The information marked with a "1)" may be maintained if authentication is performed by the UMTS authentication procedure.
The information marked with a "2)" may be maintained if authentication is performed by the GSM authentication procedure.
MM Context
1)
X
KSI
X
MNRG
Indicates whether activity from the MS shall be reported to the HLR.
X
X
NGAF
Indicates whether activity from the MS shall be reported to the MSC/VLR.
X
X
PPF
Indicates whether paging for PS and CS services can be initiated.
X
X
Subscribed Charging Characteristics
The charging characteristics for the MS, e.g. normal, prepaid, flat-rate, and/or hot billing subscription.
X
X
X
X
Recovery
X
X
X
X
ODB for PS parameters
Indicates that the status of the operator determined barring for packet oriented services.
X
X
Detach Procedure
Function
The GPRS Detach procedure allows an MS to inform the network that it does not want to access the SGSN-based services any longer
The GPRS Detach procedure allows the network to inform an MS that it does not have access to the SGSN-based services any more
The following three entity can initiate the detach procedure
MS
SGSN
HLR
Detach Procedure (MS Initiation)
MS
GGSN
SGSN
BSS/UTRAN
Detach Procedure
The SGSN shall not service the detached MS, unless reattach
The MS is in idle or PMM-DETACHED state
The MS is detached either explicitly or implicitly:
Explicit detach: The network or the MS explicitly requests detach
Implicit detach: The network detaches the MS, without notifying the MS, a configuration-dependent time after the mobile reachable timer expired, or after an irrecoverable radio error causes disconnection of the logical link.
Contents
Location Management
A mechanisms for cell and PLMN selection
A mechanism for the network to know the Routeing Area for MSs in
STANDBY, PMMIDLE and READY, PMMCONNECTED states
A mechanism for the 2GSGSN to know the cell identity for MSs in READY state;
A mechanism for the UTRAN to know the URA identity or cell identity for MSs in PMMCONNECTED state
A mechanism for the UTRAN to indicate to an MS in RRC Connected mode when a Routing Area Update procedure shall be performed by providing the RAI
A mechanism for the network to know the address of the serving RNC handling an MS in PMMCONNECTED state. This mechanism is the serving RNC relocation procedure
URA = UMTS Routing Area
RRC = Radio Resource Control
Layered Location Management Mode (2G)
SGSN
HLR
BSS
MS
Layered Location Management Mode (3G)
SGSN
HLR
RNC
MS
Network Architecture
Route area update procedure
SGSN can manage the MS location information via RAU procedure in RAI level
Relocation procedure
Handover procedure
Iur
353.unknown
Routing Area Update Procedure
MS entered a new Route Area
Periodic RAU ( after periodic timer expires)
Inter-SGSN RAU
The new SGSN find the old SGSN from the old RAI
Old SGSN stop downlink signaling, transfer MM context and PDP context to new SGSN
Tunnelling N-PDU to the new SGSN
Update PDP context and subscriber data
Routing Area Update Procedure
Inter-SGSN RAU Procedure (2G)
Next uplink/downwlink GTP NPDU sequence number
Next uplink/downlink PDCP-PDU sequence number
Service Request Procedure (UMTS only)
MS initiated
For the data transmission
Service Request Procedure –MS initiated
Service Request Procedurenetwork initiated
Contents
Purge Function
Function
The Purge function allows an SGSN to inform the HLR that it has deleted the MM and PDP contexts of a detached MS
After the MS detach from the network:
The SGSN may delete the MM/PDP context immediately
the SGSN may keep the MM/PDP context for some time of the detached MS
Purge Function
Mobility Management Timer Function
Monitors the periodic routeing area update procedure in the MS
Upon its expiry, the MS shall start a periodic routeing area update procedure.
The length of the timer is set in SGSN; The value of the timer is sent to MS in attach accept message or RAU accept message
Mobile Reachable Timer Function
Upon the expiry of this timer, the MS is detached
This is reset and started when the state returns to STANDBY or PMMIDLE
The timer shall be slightly longer than the periodic RA update timer used by an MS
The length of the timer is set in SGSN
Purge Timer Function
Allows the SGSN to inform the HLR that it has deleted the MM and PDP contexts of a detached MS.
The purge timer is set longer than the mobile reachable timer
Authentication Function
Function
Permit the network to check whether the identity provided by the mobile station is acceptable or not;
Provide parameters enabling the mobile station to calculate a new ciphering key ; UMTS and GSM
Provide parameters enabling the mobile station to calculate a new UMTS integrity key;UMTS only
Permit the mobile station to authenticate the network. UMTS only
Authentication Function
Authentication Function(3G)
Identity Check
Identity Check
PTMSI Reallocation
The reallocation procedure can be performed by the PTMSI Reallocation procedure
Function
The SGSN may reallocate the PTMSI at any time
The PTMSI can be included in the
Attach procedure or
PTMSI Reallocation
Contents
Paging Summary
PMM-IDLE
STANDBY mode
Change MM state in MS to PMM-Connected or Ready after successful paging.
Identification of MS in Paging message:
P-TMSI is used to identify the MS
If P-TMSI is invalid or MS not respond ,then use IMSI
Notes 20061213 duxiaoqin
8.2.4 Paging Initiated by CN
A CN node requests paging only for MSs in CMMIDLE state or PMMIDLE state. In the separate CN architecture, paging from a CN node is done independently from the state of the MS in the other CN service domain.
In this alternative with paging co-ordination in the UTRAN, the MS does not need to listen to the PCH (Paging Channel) in the RRC Connected mode, at least not when MS is allocated a dedicated channel.
For each paging request received from a CN node, the RNC determines whether the MS has an established RRC connection or not. In order to achieve this, the context that is prepared within the SRNC for MS in RRC Connected mode must contain the IMSI, which is the common MS identity for the two CN domains.
If no context is found for the MS, "normal PCH paging" is performed. The paging message is transferred on the paging channel, and it includes the MS paging identity received from the CN and a CN service domain type indication.
If a context is found, a "CN paging message" is transferred using the existing RRC connection. This message includes a CN service domain type indication. If, potentially after repetition, this transfer is unsuccessful and if the CS domain originally triggered the paging, the RNC should decide whether to attempt “normal PCH paging” as described in sub-clause “Unsynchronous states in the UE and the UTRAN”.
Paging for GPRS (2G)
Function
An MS in STANDBY state is paged by the SGSN before a downlink transfer to that MS
Paging move the MS state from STANDBY to READY.
Any uplink data from MS is a valid response to paging
Paging for GPRS (2G)
5. Any LLC Frame
4. Any LLC Frame
3. GPRS Paging Request
(Receive Ready or Information frame)
PS!
Paging Initiated by CN (3G)
PS Paging Initiated by 3GSGSN without RRC Connection for CS
A CN node requests paging only for MSs in PMMIDLE state
The RNS controls whether the MS has an established RRC connection or not
MS has no RRC connection
Paging Type 1 is transferred on the Paging channel
PS Paging Initiated by 3GSGSN without RRC Connection for CS
4. Service Request
4. Service Request
PS Paging Initiated by 3GSGSN with RRC Connection for CS
A CN node requests paging only for MSs in PMMIDLE state
The RNS controls whether the MS has an established RRC connection or not
In this case, MS has an established RRC connection for CS service
Paging Type 2 is base on the establish RRC connection
PS Paging Initiated by 3GSGSN with RRC Connection for CS
(RRC paging)
PMM IDLE
PMM CONNECTED
Contents
Session Management
Function
Establish and monitor a packet tunnel from MS to GGSN, and allocate system resource for the packet service.
Important Procedure
Session Management
APN-NI
DNS
BTS
SGSN
MS
DNS
BSC
PDP Context
PDP Context
The PDP context is Packet Data Protocol context
PDP context contains all the information needed to transfer user data between MS and GGSN.
The context includes parameters such as RA, QoS (Quality of Service), Charging ID etc.
PDP context exists in MS, SGSN, GGSN and RNC/BSS
PDP Context
Each MM context contains zero or more of the following PDP contexts:
Field
Description
X
X
X
X
X
X
X
X
X
X
APN in Use
The APN currently used. This APN shall be composed of the APNNetwork Identifier and the APN Operator Identifier.
X
X
NSAPI
X
X
TI
X
X
X
X
X
VPLMN Address Allowed
Specifies whether the MS is allowed to use the APN in the domain of the HPLMN only, or additionally the APN in the domain of the VPLMN.
X
X
X
X
PDP Context
X
X
X
X
The RLC/MAC radio priority level for uplink user data transmission.
X
Aggregate BSS QoS Profile Negotiated
The aggregate BSS quality of service profile negotiated for the packet flow that this PDP context belongs to.
X
Send NPDU Number
SNDCP sequence number of the next downlink NPDU to be sent to the MS.
X
Receive NPDU Number
SNDCP sequence number of the next uplink NPDU expected from the MS.
X
GTPSND
GTPU sequence number of the next downlink NPDU to be sent to the MS.
X
X
GTPSNU
GTPU sequence number of the next uplink NPDU to be sent to the GGSN.
X
X
PDCPSND
Sequence number of the next downlink in-sequence PDCPPDU to be sent to the MS.
X
PDCPSNU
Sequence number of the next uplink in-sequence PDCPPDU expected from the MS.
X
Charging identifier, identifies charging records generated by SGSN and GGSN.
X
X
The charging characteristics of this PDP context, e.g. normal, prepaid, flat-rate, and/or hot billing.
X
X
X
MM Context and PDP Context
MM context
PDP State
PDP state
ACTIVE
Deactivate PDP ContextorMM state change to IDLEor PMM-DETACHED
Activate PDPContext
PDP Type and PDP Address
PDP Type
QoS
QoS is quality of service
It is a group of parameters that can define the network ability, such as
bit rate for downlink data transmission
bit rate for uplink data transmission
reliability class
delay class
APN
Network ID shall not end with “.gprs”
huawei.com.cn.mnc<MNC>.mcc<MCC>.gprs
google.com.mnc001.mcc262.gprs
APN
APN
google.com.mnc262.mcc01.gprs
APN Network ID
APN Network ID
APN_NI: shall not end with “.gprs”
APN
MS
SGSN
GGSN1
GGSN2
GGSN3
DNS
APN1
APN2
APN3
APN
APN
PDP Activation Procedure
PDP context activation procedure
To establish a PDP context between the MS and the SGSN, the GGSN
PDP Active Procedure (2G)
2G
-SGSN
BSS
C1
C2
PDP Active Procedure (3G)
Charging ID allocation
3G
-SGSN
UTRAN
MS
4.
C1
C2
Handle in MS
MS start and send “Active PDP context request” to SGSN
Provide QoS parameter
Provide a APN-NI
Receive ACCEPT from SGSN
If the QoS not accept by MS, then starts delete PDP context procedure.
Handle in SGSN
Check subscriber data
According to TS 23.060
default APN,APN provide from MS and the APN subscribed in HLR
APN-NI.APN-OI
QoS provided from MS, default QoS ,QoS subscribed in HLR
Send message “create PDP context request” to GGSN
RAB assignment
Dynamic IP address
Handle in RNC
Allocate Iu interface resource
Handle in GGSN
QoS negotiation
Allocate a charging ID for the PDP context
Return a CREATE PDP CONTEXT ACCEPT message to SGSN
Dynamic IP
Summary
In the whole GPRS fundamental, you should remember some important concept and the basic signalling procedure
Thank you
8. Downlink PDU
Request
Response
IDLE
READY
STANDBY
IDLE
READY
STANDBY
1. Detach Request
3
Request
Response
4. Service Accept
Deactivate PDP Context
or PMM-DETACHED
Activate PDP

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