Post on 14-Apr-2018
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TP-0094.3, February 2000, Slide 1
GPRS: General Packet
Radio Service
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TP-0094.3, February 2000, Slide 2
What Is GPRS?
GPRS is the integration of the two strongestworldwide trends:
In ternet and GSM
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TP-0094.3, February 2000, Slide 3
What Is GPRS? (Cont.)
Packet data network connectivity for GSMnetworks
Allows completely transparent IP support
Billing according to actual bandwidth consumed!
• As opposed to billing by calls, or billing by
bandwidth provisioned
User can stay connected (on-line) for long
periods of time without sending any data and
without paying
Dynamically variable data rates: from 9 to 150
Kbits/s per user
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TP-0094.3, February 2000, Slide 4
Data will account for up to 75% of total mobile traffic
Source:
Siemens
Mbytes per user per month
Today
0.8 Mb/user/month
Huge Increase of Mobile Data
Volume
0
5
10
15
20
25
30
35
1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
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TP-0094.3, February 2000, Slide 5
GPRS Applications
Two classes of applications :
• Horizontal applications – Are not specific to any
business segment.
• Vertical applications – Are tailormade for specific
business segment.
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TP-0094.3, February 2000, Slide 6
GPRS Applications(Cont.)
Horizontal applications :• Company e-mail
• Document and data sharing
• Sales and customers support
•Corporate news and phone directories
• Job postings
Vertical applications :
• Vending and lottery machines
• Dispatch operations(taxi, field services)• Police operations
• Medical emergency operations
• Traffic and weather conditions
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GPRS Main Concepts
Optimizes the use of RF network and resources
Strict separation between the RF subsystem and
data network
Datacom internetworking performed by the
tunneling concept
Internetworking defined for IP and X.25 networks
• Seamless connectivity to the internet
Does not force any changes to GSM’s MSCs Other GSM entities need only software updates
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GSM Architecture
GSM Network
Mobile
PSTN
BSS
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GPRS Architecture
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GPRS Architecture (Cont.)
GPRSBackbone
SS7
PSTN
Data
Network
Internet
Mobile
PC E t h e r n e t
BSS
BTS
EIR
MSC
SGSN
BSC
VLR
GGSN
Workstation
FW
Router
Border GWInter PLMN
Network
X.25
Network
Corporate
Network
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GPRS Add-ons to GSM
SGSN: the serving GSN (GPRS support node)• Keeps track of individual MS location
• Performs security and access control functions
• Is connected to the BSS via frame relay
GGSN: the gateway GSN (GPRS support node)
• Provides interworking with external packet-switched
networks(IP, X.25)
•Is connected to the SGSN via an IP-based GPRSbackbone network
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GPRS Add-ons to GSM(Cont.)
Other additions• HLR – is enhanced with GPRS subscriber
information
• SMS – is upgraded in order to support SMS
transmission via the SGSN
• MSC/VLR – optionally, the MSC/VLR can be
enhanced for more efficient co-ordination of GPRS
and non-GPRS services and functionality
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Transmission Plane
Consists of a layered protocol structureproviding:
• User information transfer
• Information transfer control procedures
•
Flow control• Error detection,
• Error correction
• Error recovery
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Transmission Plane Protocol
Stack
Relay
Network
Service
GTP
Application
IP / X.25
SNDCP
LLC
RLC
MAC
GSM RF
SNDCP
LLC
BSSGP
L1bis
RLC
MAC
GSM RF
BSSGP
L1bis
Relay
L2
L1
IP
L2
L1
IP
GTP
IP / X.25
Um Gb Gn GiMS BSS SGSN GGSN
Network
Service
UDP /TCP
UDP /TCP
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Transmission Plane Protocol
Stack(Cont.)GTP – GPRS tunnelling protocol.
SNDCP – maps network-level characteristics
onto the characteristics of the underlying
network.
BSSGP – conveys routing and QoS information
between the BSS and SGSN.
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Transmission Plane Protocol
Stack(Cont.)NS – performs the transport of BSSGP PDUs
between the BSS and SGSN.
LLC – defines the logical link control layer protocol to be used for packet data transfer
between the MS and the SGSN.
Relay – relays LLC or PDP PDUs between
different interfaces(Um/Gb or Gb/Gn).RLC/MAC – provides radio link control function.
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Signalling Plane
Consists of protocols for control and support of the transmission plane functions:
• Controlling the GPRS network access connections
• Controlling the attributes of an established network
access connection
• Controlling the routing path of an established
network connection
• Controlling the assignment of network resources
• Providing supplementary services
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Signalling Plane MS-SGSN
BSSGP
Relay
GMM/SMLLC
RLC
MAC
GSM RF
GMM/SMLLC
BSSGP
L1bis
Um Gb
MS BSS SGSN
Network
Service
RLC
MAC
GSM RF L1bis
Network
Service
GMM/SM:
• GPRS Attach/Detach
• Security, routing area, location update
• PDP context activation/modification/deactivation
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TP-0094.3, February 2000, Slide 19
Signalling Plane SGSN-HLR
MAP - with additional functionalities to handleGPRS subscribers information, among other functions
TCAP, SCCP, MTP3 and MTP2 – SS7 protocols
SCCP
MTP2
MTP3
MTP2
MTP3
SCCP
Gr
SGSN HLR
TCAP
MAP
TCAP
MAP
L1 L1
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TP-0094.3, February 2000, Slide 20
Signalling Plane GSN-GSN
GTP – GPRS Tunnelling protocol.
• This protocol tunnels user and signalling data between
GPRS support nodes(GSNs) in the GPRS backbone.
• Create/update/delete PDP context request/response.
UDP
L2L1
IP
L2L1
IP
UDP
GnGSN GSN
GTP GTP
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TP-0094.3, February 2000, Slide 21
Signalling Plane-Interfaces
MS - SGSN : Um and Gb interfaces
GSN - GSN : Gn interface
SGSN - HLR : Gr interfaceOther signalling planes:
• SGSN - MSC/VLR : Gs interface
• SGSN - EIR : Gf interface
• SGSN - SMS-GMSC or SMS-IWMSC : Gd interface• GGSN - HLR : Gc interface
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TP-0094.3, February 2000, Slide 22
GPRS Protocols - Interfaces
Protocol Interface
GTP Gn
SNDCP Gb
LLC Gb
NS Gb
GMM Gb
BSSGP Gb
BSSAP+ Gs
MAP Gr , Gf , Gd and Gc
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TP-0094.3, February 2000, Slide 23
MS Identities
IMSI – International Mobile Subscriber Identity.• A unique identity allocated to each mobile
subscriber in GSM/GPRS.
P-TMSI – Packet Temporary Mobile Subscriber
Identity.TLLI – Temporary Logical Link Identity.
• Is derived from a P-TMSI and provides user identity
confidentiality.
PDP Address – Packet Data Protocol Address• A GPRS Subscriber(identified by IMSI) shall have a
network layer address(IP version 4/6).
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TP-0094.3, February 2000, Slide 24
MM Functionality
Mobility management(MM) states
• Three different MM states :
• IDLE
• STANDBY
• READY
• Each state describes a level of functionality and
information
• The information sets held at MS and SGSN are
denoted MM context
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TP-0094.3, February 2000, Slide 25
MM Functionality(Cont.)
IDLE
READY
STANDBY
GPRS Detach
PDU transmission
GPRS Attach
READY timer expiryor Force to STANDBY
STANDBY timer
expiry
State model of MS - Transitions and Functions
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TP-0094.3, February 2000, Slide 26
MM Functionality(Cont.)
State model of SGSN - Transitions and Functions
IDLE
READY
STANDBY
GPRS Detach
or
Cancel Location
PDU reception
GPRS Attach
READY timer expiry
or Force to STANDBY
or Abnormal RLC condition
STANDBY timer
Expiry or Cancel
Location
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TP-0094.3, February 2000, Slide 27
GPRS Attach Procedure
MS Network
ATTACH REQUESTStart T3310
ATTACH ACCEPT
ATTACH REJECTStop T3310
Stop T3310
or
ATTACH COMPLETEStop T3350
ATTACH REQUEST
Start T3310
If P-TMSI
and/or
TMSI allocated
Start T3350If P-TMSI
and/or
TMSI allocated
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TP-0094.3, February 2000, Slide 28
GPRS MM TimersTIMER
NUM.
TIMER
VALUE
STATE CAUSE OF START NORMAL STOP ON THE
1st
, 2nd
, 3rd
, 4th
EXPIRY Note 3
T3310 15s GMM-REG-INIT
ATTACH REQ sent ATTACH ACCEPTreceived
ATTACH REJECTreceived
Retransmission of ATTACH REQ
T3311 15s GMM-DEREG ATTEMPTINGTO ATTACH or
GMM-REG ATTEMPTING
TO UPDATE
ATTACH REJ with othe r causevalues as described in chapter ‘GPRS Attach’
ROUTING AREA UPDATE REJwith other cause values asdescribed in chapter ‘Routing
Area Update’
Low layer failure
Change of therouting area
Restart of the Attach or th e RAUprocedure withupdating of therelevant attemptcounter
T3321 15s GMM-
DEREG-INIT
DETACH REQ sent DETACH ACCEPTreceived
Retransmission of the DETACH REQ
T3330 15s GMM-ROUTING-UPDATING-INITIATED
ROUTING AREA UPDATEREQUEST sent
ROUTING AREAUPDATE ACCreceived
ROUTING AREAUPDATE REJreceived
Retransmission of the ROUTING AREA UPDATEREQUESTmessage
TIMERNUM.
TIMERVALUE
STATE CAUSE OF START NORMAL STOP ON THE
1st
, 2nd
, 3rd
, 4th
EXPIRY Note 3
T3322 6s GMM-DEREG-INIT DETACH REQ sent DETACH ACCEPTreceived Retransmission of DETACHREQUEST
T3350 6s GMM-COMMON-PROC-INIT
ATTACH ACCEPTsent with P-TMSI and/or TMSI
RAU ACCEPT sent with P-TMSIand/or TMSI
P-TMSI REALLOC COMMANDsent
ATTACHCOMPLETEreceived
RAU COMPLETEreceived
P-TMSI REALLOCCOMPLETEreceived
Retransmission of the same messagetype, i.e. ATTACH ACCEPT, RAU ACCEPT or REALLOCCOMMAND
T3360 6s GMM-COMMON-PROC-INIT
AUTH AND CIPH REQUESTsent
AUTH AND CIPHRESPONSEreceived
Retransmission of AUTH AND CIPHREQUEST
T3370 6s GMM-COMMON-
PROC-INIT
IDENTITY REQUEST sent IDENTITYRESPONSE
received
Retransmission of IDENTITY
REQUEST
GSM 04.08: GPRS Mobility management timers - network side
GSM 04.08: GPRS Mobility management timers - MS side
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TP-0094.3, February 2000, Slide 29
GPRS Detach Procedure
MS Network
DETACH REQUESTStart T3321
DETACH ACCEPTStop T3321
or at MS power switch off
DETACH RE UEST
MS initiated GPRS detach procedure
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TP-0094.3, February 2000, Slide 30
GPRS Detach Procedure(Cont.)
MS Network
DETACH REQUEST Start T3322
DETACH ACCEPTStop T3322
SGSN initiated GPRS detach procedure
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TP-0094.3, February 2000, Slide 31
PDP Procedure
Packet Data Protocol(PDP):• PDP context - Procedure that allows an MS to
transfer data.
• PDP Address – Network layer address(IP version 4,
IP version 6).
• Each PDP address – Described by an individual PDP
context in the MS/SGSN/GGSN.
• There are two PDP states:
• Inactive State.
• Active State.
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TP-0094.3, February 2000, Slide 32
INACTIVE State:
• No routing or mapping information to process PDUs
•
No data can be transferred ACTIVE State:
• MM state of subscriber is STANDBY or READY
• Moves to INACTIVE when MM state changes to IDLE
PDP States
ACTIVE
INACTIVE
Deactivate PDP Context
or
MM state change to IDLE Activate PDP Context
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TP-0094.3, February 2000, Slide 33
PDP Context Activation,
Modification and DeactivationA MS can initiate those functions at any time
A GGSN may request the PDP context activation
and initiate the PDP context deactivation
Static and Dynamic PDP Addresses:
• Static address : The PLMN operator assigns a PDP
address permanently to the MS
• Dynamic address : The PLMN operator assigns a
PDP address to the MS when a PDP context isactivated
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TP-0094.3, February 2000, Slide 34
MS-PDP Context Activation
Procedure
MS GGSNSGSN
1.Activate PDP Context Request
3.Create PDP Context Request
3.Create PDP Context Response
4.Activate PDP Context Accept
2.Security Functions
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TP-0094.3, February 2000, Slide 35
GGSN-PDP Context Activation
ProcedureMS GGSNSGSN
2.Send Routing Info for GPRS
3.PDU Notification Request
4.Request PDP Context Activation
HLR1.PDP PDU
2.Send Routing Info for GPRS Ack
3.PDU Notification Response
5.PDP Context Activation Procedure
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TP-0094.3, February 2000, Slide 36
PDP Context Modification
Procedure
MS GGSNSGSN
1.Update PDP Context Request
3.Modify PDP Context Request
2.Update PDP Context Response
4.Modify PDP Context Accept
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TP-0094.3, February 2000, Slide 37
MS-PDP Context Deactivation
Procedure
MS GGSNSGSN
1.Deactivate PDP Context Request
3.Delete PDP Context Request
3.Delete PDP Context Response
4.Deactivate PDP Context Accept
2.Security Functions
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TP-0094.3, February 2000, Slide 38
GGSN-PDP Context
Deactivation Procedure
MS GGSNSGSN
1.Delete PDP Context Request
2.Deactivate PDP Context Request
3.Delete PDP Context Response
2.Deactivate PDP Context Accept
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TP-0094.3, February 2000, Slide 39
GPRS Tunnelling Protocol
GPRS Tunnelling Protocol(GTP) - Allows multi-protocol packets to be tunnelled through the
GPRS Backbone between GSNs
Two modes of operation for information transfer
are supported:• Unacknowledged Mode – UDP/IP
• Acknowledged Mode – TCP/IP
Uses a tunnelling mechanism to provide services
for carrying PDUs over an IP or X.25 networks
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GTP Signalling Messages
Path management messages:• Echo Request
• Echo Reply
Tunnel management messages:
• Create PDP Context Request (SGSN to GGSN)• Create PDP Context Response (GGSN to GGSN)
• Update PDP Context Request / Response
• Delete PDP Context Request / Response