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www.huawei.com
Internal
OMQ000001 GPRS Principle
ISSUE 2.0
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GPRS principle is the basic part of the
whole GPRS system and the succeeding products learning.
This slide will help us to understand the
GPRS system networking and wireless subsystem etc.
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References
� GPRS principle
� GPRS protocol
� 31025698 - M900/M1800 PCU
Technical Manual
HUAWEI TECHNOLOGIES CO., LTD. Page 4All rights reserved
� Upon completion of this course, you will
be able to:
�Know the GPRS system structure
�Describe the GPRS important
interfaces
�Understand the GPRS channel
structures
�Master the GPRS relevant numbering
HUAWEI TECHNOLOGIES CO., LTD. Page 5All rights reserved
Chapter 1 Chapter 1 GPRS System OverviewGPRS System Overview
Chapter 2 GPRS Achitecture Chapter 2 GPRS Achitecture
Chapter 3Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
Chapter 5 Chapter 5 GPRS Location AreaGPRS Location Area
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Circuit Switch (CS)
CS
F
CS
CS CS
CS
A
B
C
D
E
G
H
I
J
K
L
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Packet Switch (PS)
PS
PS
PS
12 3
12
3
1
3
2
2
1 3
2
2
1 3
1 2 3
12
3
PS
PS
PS
PS
PS
PS
PS
12 3
12
3
1
3
2
2
1 3
2
2
1 3
1 2 3
12
3
PS
PS
PS
AC
B D
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GSM Development Evolution
GSM 9.6 Kb/s
GPRS21.4 Kb/s
EGPRS59.2 Kb/s
384 Kb/s UMTS
2 G
2.5 G
2.75 G
3 G
HSCSD14.4 Kb/s
ECSD38.8 Kb/s
CS
PS
EDGE
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What is GPRS and EDGE?
� Abbreviation of General Packet Radio Service.
� GPRS is an end-to-end packet switching technology provided
on the basis of GSM technology.
� It has much interactive services with the existing GSM circuit
switching system.
� GPRS supports wireless access rate of up to 171.2Kbps.
� EDGE (Enhanced Data Rates for GSM Evolution)
� EGPRS (Enhanced GPRS)
− EGPRS supports wireless access rate of up to 473.6Kbps.
� ECSD (Enhanced CSD, Enhanced HSCSD-High Speed Circuit
Switched Data)
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GPRS&EDGE Coding Rate
8PSKGMSK
9.05
13.415.6
21.4
8.811.2
14.817.6
22.4
29.6
44.8
54.4
59.2
0.00
10.00
20.00
30.00
40.00
50.00
60.00
CS-1 CS-3 CS-4 MCS-1 MCS-2 MCS-3 MCS-4 MCS-5 MCS-6 MCS-7 MCS-8 MCS-9
Kbps
GPRS
EGPRS
CS-2
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Adjustments to GSM Network
BSS CS Core Network
A
PS Core Network
PCU
BSS NSS
Gb
Pb
Gs
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Most Popular GPRS Applications
� Web Browsing
� Information Services
� Moving Images
� Still Images
� Remote LAN Access
� File Transfer
� Job Despatch
Traffic Information
Sport Report
Weather Forecast
Stock Market
PublicInformation
Service
Web Browsing
Still Images
File Transfer
Moving Bank
Live News
PersonalInformation
Service
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Advantages and Disadvantages of GPRS
� Advantages
�Share resource with GSM
�High resource utilization
�Fast transmission rate
�Always on line
�Short access time
� Disadvantages
�Slower data rates in practice than anticipated in theory
�Suboptimal modulation technique
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Chapter 1 Chapter 1 GPRS System OverviewGPRS System Overview
Chapter 2 GPRS Achitecture Chapter 2 GPRS Achitecture
Chapter 3Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
Chapter 5 Chapter 5 GPRS Location AreaGPRS Location Area
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CS & PS Logic Structure
HLRAUC
GPRSRegister
MSC/VLR
BSCAbis
D
C
CS
GMSCPSTN
BTS
BSS
CN
E
A
PS Gs
SGSN
GGSN
Gb
Gn
Gc
Gr
Gi
Internet
G-Abis Pb
PCU
TRAU
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Modifications in BSS (GSM Evolves into GPRS)
Upgrade BSC software
Add new PCUUpgrade BTS software
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Modifications in BSS (GPRS Evolves into EDGE)
Upgrade BSC software
Upgrade PCU software
Upgrade BTS software and hardware
TE
R
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Modifications in Core Network(GSM Evolves into GPRS/EDGE)
� New GPRS CN equipments
�SGSN
�GGSN
�CG
� Upgraded GPRS CN equipments
�HLR
�MSC/VLR
�SMS-GMSC/SMS-IWMSC
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Gf
GiGn
Gc
Gp
Gs
MSC/VLR
Gr
SGSN
Gd
SMS-GMSCSMS-IWMSC
GGSN
EIR
SGSN
Gn
GPRSBackbone
ATM/DDN/ISDN/Ethernet, etc
CNCN--PSPS
GGSN
GiCG
GPRS System Structure
Gb
SS7
HLR
Ga
Intranet/InternetFirewall
RADIUS
WAP Gateway
Other PLMN
BTS
BSCBSSBSS
AbisPCU
Gb
BTS
BSCBSSBSS
AbisPCU
X.25
DNS BG
MS
MS
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GPRS MS� TE(Terminal Equipment)
� MT(Mobile Terminal)
� TA (Terminal Adapter)
TETEMTMT
UUmmR R GGii
GPRS Network1
GPRSNetwork2
PDN/Other Network
GGpp
TA
MSMS
S S
Reference Point Reference Point
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GPRS MS
�Class A
�The MS is attached to both GPRS and other GSM services and the MS supports simultaneous operation of GPRS and other GSM services.
�Class B
�The MS is attached on GPRS network and GSM network simultaneously but not enabling circuit switching and packet switching services at the same time.
�services are selected automatically.
�Class C
�The MS is attached to either GPRS or other GSM services. Alternate use only.
�services are selected manually or default selected service.
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Functions of PCU (Packet Control Unit)
� Provides physical and logical data interface out of the BSS for packet data traffic
� LLC layer PDU segmentation/reassembly of RLC blocks
� Packet data transfer scheduling
� Radio channel management function
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Position of Huawei PCU
CCU
CCU
BSCBTS
SGSN
Um Gb
BSC
Pb
CCU
CCU
PCU
BTS
Abis
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Functions of SGSN (Serving GPRS Support Node)
� Packet routing
� MS Session management
� Authentication and Ciphering
� Mobility management
� Billing information collection
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Functions of GGSN (Gateway GPRS Support Node)
� Interface between GPRS backbone and external PDNs.
� PDP Conversion and context management
� IP address assignment management
� Packet routing to/from SGSNs
� Billing information collection
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Functions of CG (Charging Gateway)
� Real-time collection of GPRS bills
� Temporary storage and buffering of GPRS bills
� Pre-processing of GPRS bills
� Sending GPRS bills to the billing center
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Functions of MSC/VLR
When Gs interface is installed, MSC/VLR can support
� Establishment and maintenance of the association between SGSN
and MSC/VLR.
� GPRS combined mobility management procedure.
� Combined IMSI/GPRS attachment/detachment.
� Combined location area/routing area updating.
� Circuit paging coordination function.
The wireless resource usage can be greatly improved.
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Functions of HLR/AUC
� Saving and updating GPRS subscriber subscription data
� User authentication
� Providing location/routing 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.
� Subscriber tracing (optional)
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Functions of SMS-GMSC/SMS-IWMSC
� The SMS-GMSC and SMS-IWMSC are connected to the SGSN
via the Gd interface to enable GPRS MSs to send and receive
SMs over GPRS radio channels.
� After Gd interface is installed, short messages can be sent via
GPRS, which reduces the occupation on SDCCH and cuts down
the influence on voice services by SMS services.
� The operator can select to send SMS via MSC or SGSN.
MS SGSN SMS-IWMSCSMS-GMSC
GdSMS
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Functions of BG (Border Gateway)� BG enables the following protocols necessary for in terworking between
operators
� Security protocol: IPSec and firewall are recommended
� Routing protocol: BGP is recommended
� Billing protocol: determined by the operators with negotiation; BG
might be needed in collecting billing information
� It is normally based on routers
� It can be combined with GGSN in physical.
� BG does not exclusively belong to the GPRS network.
Gp
PLMN AGSN RR
BG RR
BG GSN PLMN B
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Functions of DNS (Domain Name System)� The following two types of DNSs may be adopted in the GPRS network:
�The DNS between the GGSN and external networks
�The DNS on the GPRS backbone network. Provides two types of
functions:
− a. Resolve the GGSN IP address based on the Access Point
Name (APN) in the process of the PDP context activation;
− b. Resolve original SGSN IP address based on the original routing area No. in the process of the update of inter-SGSN
routing area.
� DNS does not exclusively
belong to the GPRS network. GPRS BackboneSGSN
DNS Server
SGSN
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Functions of RADIUS Server (Remote Authentication Dial In User Service Server)
� It is a protocol used by Remote Access Server's for user Authentication.
� The RADIUS server stores the authentication and authorization
information of subscribers.
� It also performs subscriber identity authentication in the case of non-
transparent access.
� RADIUS Server does not exclusively belong to the GPRS network.
HUAWEI TECHNOLOGIES CO., LTD. Page 33All rights reserved
Chapter 1 Chapter 1 GPRS System OverviewGPRS System Overview
Chapter 2 GPRS Achitecture Chapter 2 GPRS Achitecture
Chapter 3 Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
Chapter 5 Chapter 5 GPRS Location AreaGPRS Location Area
HUAWEI TECHNOLOGIES CO., LTD. Page 34All rights reserved
Chapter 3 Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
3.1 Interface and Protocol Stack
3.2 Um Interface
3.3 G-abis/Pb Interface
3.4 Gb Interface
3.5 Gs Interface
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Network Interface Types
GPRS backbone network
SGSNSGSN
SGSNSGSNGGSNGGSNGn
IP interface
SS7 interface
BSS MSCSMS-GMSC
AUm
PDP network(IP/X.25)
Gi
TE
MT
MS
HLR
Gs
Gr
Gd
Gc
Gb
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Interface in GPRS Network
The interface between MS and GPRS network sideUm
The interface between the SGSN and EIR (optional). Gf
The interface between the SGSN and MSC/VLR (optional). Gs
The interface between the SGSN and HLR. Gr
The interface between GSNs of different PLMNs. Gp
The interface between SGSNs and between SGSN and GGSN in the PLMN. Gn
The reference point between the GPRS and external packet dataGi
The interface between SMS and GMSCThe interface between SMS-IWMSC and SGSN
Gd
The interface between the GGSN and HLR (optional). Gc
The interface between the SGSN and BSS. Gb
The reference point between the Mobile Terminal (MT) (for example, mobile phone) and the Terminal Equipment (TE) (for example, the portable computer).
R
DescriptionInterfac
e
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Data Transmission Plane
� MAC: Media Access Control
� RLC: Radio Link Control
� LLC: Logical Link Control
� BSSGP: BSS GPRS Protocol
� SNDCP: Sub-Network Dependency Convergence Protocol
� GTP: GPRS Tunneling Protocol
Application
IP/X.25 IP/X.25 IP/X.25
SNDCP GTP
LLC LLC UDP/TCP UDP/TCP
RLC BSSGP BSSGP IP IP
MAC MAC NetworkService
NetworkService L2 L2
L2 (MAC)
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
PhysicalLayer
MS BSS SGSN GGSN
relay
relaySNDCP GTP
Um Gb Gn Gi
RLC
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MS-SGSN Signaling Plane
� GMM: GPRS Mobility Management
� SM: Session Management
MS BSS SGSN
BSSGP
GMM/SM
LLC
RLC
MAC
GSM RF
GMM/SM
LLC
BSSGP
L1bis
Um Gb
NetworkService
RLC
MAC
GSM RF L1bis
NetworkService
Relayrelay
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Chapter 3 Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
3.1 Interface and Protocol Stack
3.2 Um Interface
3.3 G-abis/Pb Interface
3.4 Gb Interface
3.5 Gs Interface
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Protocol Layer of Um Interface
� GMM (GPRS Mobility Management): operates in the signalling plane of GPRS supports mobility management functionality.
� SM (Session Management): processes procedure that GPRS MS connects to the external data network.
� SNDCP (Subnetwork Dependent Convergence Protocol): Multiplexing of several PDPs, compression / decompression and Segmentation of user data.
� LLC (Logical Link Control ): This layer provides a highly reliable ciphered logical link between an MS and its SGSN.
� RLC:Segmentation and re-assembly between LLC PDUs and RLC blocks.
� MAC: defines the procedures that enable multiple mobile stations to
share a common transmission medium.
LLC
RLC
MAC
RF
Physical Link
SN
DC
P
SM
S
GM
M/S
M
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MM State
IDLE �GMM context is not established; MS is not reachable.
�MS can implement data transmission.
�GMM context is established; MS can receive paging but cannot implement data transmission.
− The MS performs MM procedures to provide the network with the actual
selected cell.
− SGSN performs the MM on cell level.
READY
STANDBY− The location information in the SGSN MM context contains only the GPRS RAI.
− Pages for data or signalling information transfers may be received. It is also
possible to receive pages for the CS services via the SGSN. Data reception
and transmission are not possible in this state.
− Data transmission to and from the mobile subscriber as well as the paging of
the subscriber are not possible
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MM State Model
IDLE READY STANDBY
IDLE READY STANDBY
MM State Model of MS
MM State Model of SGSN
GPRS Attach
GPRS Detach
READY timer expiry or
PDU transmission
PDU reception
Implicit Detach or Cancel Location
GPRS Attach
Force to STANDBY
READY timer expiry orForce to STANDBY or
Abnormal RLC condition
GPRS Detach or Cancel Location
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Transmission Principle of Data Packet on Um Interface
RLC/MAC block
Subscriber data
RLC/MAC headLLC headSNDCP head LLC FCS
LLC frame
Subscriber IP packet (N-PDU)
SNDCP PDU(SN-PDU)
Network Layer
SNDCP Layer
LLC Layer
RLC/MAC Layer
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Chapter 3 Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
3.1 Interface and Protocol Stack
3.2 Um Interface
3.3 G-abis/Pb Interface
3.4 Gb Interface
3.5 Gs Interface
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G-abis/Pb Interface
MS
BTS
PCU
MS
G-abisBSC
Abis Pb
�G-abis/Pb interface is not a standard interface
HUAWEI TECHNOLOGIES CO., LTD. Page 46All rights reserved
Chapter 3 Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
3.1 Interface and Protocol Stack
3.2 Um Interface
3.3 G-abis/Pb Interface
3.4 Gb Interface
3.5 Gs Interface
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Protocol Stack of the Gb Interface
BSS SGSN
BSSGP
GMM/SM
LLC
BSSGP
L1bis
Gb
NetworkService
RLC
MAC
GSM RF L1bis
NetworkService
Relayrelay
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NS Layer Definition
�The Network Service performs the transport of NS SDUs(Service Data Unit )
between the SGSN and BSS.
�The Network Service entity is composed of the Sub-Network Service and the
Network Service Control.
FR PVC((((DLCI))))
NSVC((((NSVCI))))
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NS Layer Functions
� Sub-Network Service Functions
� The Sub-Network Service functions of the Network Service shall provide access to the intermediate network (or to the peer entity in case of direct point-to-point configuration) and shall provide NS-VCs between NS peer entities.
� Frame Relay shall be the network used on the Gb interface. The Sub-Network Service entity is the Frame Relay entity.
� Network Service Control Functions
� NS SDU transmission
� Load sharing� NS-VC management
BSS
FR Network
SGSN
DTE
DTEDTE
DCE
Gb Gb
Gb
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NS Layer Parameters
� BC
� Bearer Channel: consist of one group of time slots in one E1
� DLCI� Data Link Connection Identifier: the identifier of PVC having end-to-end
significance across the Gb interface
� NSVC, NSVCI
� The NS-VCs are end-to-end virtual connections between the BSS and SGSN.
� NSE, NSEI� NS entity, NSE is responsible for management of all of NS-VC, e.g. NSVC
block /unblock /reset
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NS Layer StructureBC1(TS1~TS3)
BC2(TS1~TS3)E1 link
TS0~TS31
SGSN
E1 linkTS0~TS31
BSS
NSVCI=10
DLCI=259
NSVCI=20
DLCI=16
NSVCI=20
DLCI=16
NSVCI=10
DLCI=259
NSVC collection
NSEI=1
NSVC collection
NSEI=1
TS3TS2TS1
TS3TS2 TS1
……
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NS Layer Load-sharing
NSVC channel=10 DLCI=259
NSVC channel=20 DLCI=16
NS Layer
ms#1ms#2
cell
SGSN BSS
BSSGP Layer BVC1 BVC2
BVC1 BVC2
NSE1NSE1NSE2 NSE2
NSE3 NSE3
Two users in the same cell
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Functions of BSSGP� The primary function of BSSGP is to provide the radio-related, QoS, and routing
information that is required to transmit user data between a BSS and an SGSN.
� A secondary function is to enable the SGSN and BSS to operate node
management control functions.
� BSSGP Virtual Connections (BVCs) provide communication paths between BSSGP entities. Each BVC is used in the transport of BSSGP PDUs between the
following entities:
− peer point-to-point (PTP) functional entities : PTP user data transmission. A
cell is identified by a BVCI.
− peer point-to-multipoint(PTM) functional entities: PTM user data
transmission. There is one or more PTM functional entities per BSS.
− peer signalling functional entities : Signaling transmission. Each NSE
corresponds a SIG BVC. There is one or more NSEs per BSS.
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Realization of BSSGP Layer
GbSIG BVC
BVC1 1
BVC1 2
BVC1 3
BVC1 4
BVC1 5
BVC1 1
BVC1 2
BVC1 3
BVC1 4
cell1
cell2
cell3
cell4
PTP BVC
BSC SGSN
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The Difference btw. PTP BVC and SIG BVC
NSE NSE
NSVC1
NSVC2
SIG BVC
PTP BVC
Signaling
User data
Cell1 Cell2 Cell1 Cell2
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Chapter 3 Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
3.1 Interface and Protocol Stack
3.2 Um Interface
3.3 G-abis/Pb Interface
3.4 Gb Interface
3.5 Gs Interface
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SCCP
MTP2MTP3
MTP2MTP3
SCCP
GsSGSN MSC/VLR
BSSAP+ BSSAP+
L1 L1
SGSN - MSC/VLR Signaling Plane
� Gs interface is the optional interface.
� It adopts BSSAP+ protocol to enable combined mobility management and
paging functions so as to improve the effective usage of wireless resources.
MSC/VLR
Gs
SGSN
BSCPCU
TRAU
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Cooperation between GMM and MM
� Objectives
� To improve the effective usage of wireless resources
� To reduce the network signaling traffic
� Pre-condition
�SGSN and MSC/VLR support Gs interface
� Functions
�Combined IMSI/GPRS attachment and Combined IMSI/GPRS detachment
�Combined routing area/location area updating (including periodical)
�Paging Co-ordination
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Network Operation Mode (Paging Co-ordination)�Paging co-ordination means that the network sends paging messages for circuit-switched services on the same channel as used for packet-switched services, i.e., on the GPRS paging channel or on the GPRS traffic channel, and the MS needs
only to monitor that channel.
CCCH Paging Channel
CCCH Paging Channel
CCCH Paging Channel
Packet Data Channel
CCCH Paging Channel
Packet Paging Channel
Circuit Paging Channel
CCCH Paging Channel
Packet Paging ChannelNetwork Operation Mode
III
No (Gs interface is not present, all MSC-originated paging of GPRS-attached MSs shall
go via the A interface)
CCCH Paging ChannelNetwork Operation Mode
II ��
Not Applicable
CCCH Paging Channel
Yes (Gs interface is present, all MSC-originated paging of GPRS-attached MSs shall
go via the SGSN)
Packet Paging ChannelNetwork Operation Mode
I
Paging co-ordinationGPRS Paging Channel
Mode
HUAWEI TECHNOLOGIES CO., LTD. Page 60All rights reserved
Chapter 1 Chapter 1 GPRS System OverviewGPRS System Overview
Chapter 2 GPRS Achitecture Chapter 2 GPRS Achitecture
Chapter 3Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
Chapter 5 Chapter 5 GPRS Location AreaGPRS Location Area
HUAWEI TECHNOLOGIES CO., LTD. Page 61All rights reserved
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
4.1 Packet Channels
4.2 Medium Access Modes
4.3 MS Multi-TS Ability
4.4 Power Control
4.5 Network Control Modes
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Physical Channel
The same as in GSM
� The same frequency
� The modulation mode
� The same TDMA frame definition
� The same burst pulse definition
� …
� The differences between GPRS and GSM
� The Multi-frame structure
� The channel coding
� …
Application
IP/X25
SNDCP
LLC
RLC RLC BSSGP
MAC MACFramerelay
PhysicalLayer
PhysicalLayer
PhysicalLayer
MS BSS
Relay
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Packet Logic Channels
� The specific type of PDCH (except PRACH) is determined by RLC/MAC head
and RLC/MAC control message type.
TCH
BCCH
PCH, RACH, AGCH,NCH
Packet service channel
PACCH
Packet Logic Channel
Packet control channel
PBCCH
PPCH PRACH PAGCH
PCCCH PDCCH
PDTCH/U PDTCH/D PNCH
PTCCH/U PTCCH/DSACCH
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Channel Abbreviation
� Packet Data Traffic CHannel Uplink - PDTCH/U
� Packet Data Traffic CHannel Downlink - PDTCH/D
� Packet Broadcast Control CHannel - PBCCH
� Packet Common Control CHannel - PCCCH
� Packet Dedicated Control Channel - PDCCH
� Packet Paging CHannel - PPCH
� Packet Random Access CHannel - PRACH
� Packet Access Grant CHannel - PAGCH
� Packet Notification CHannel - PNCH
� Packet Associated Control CHannel - PACCH
� Packet Timing advance Control CHannel Uplink - PTCCH/U
� Packet Timing advance Control CHannel Downlink - PTCCH/D
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PDTCH (Packet Data Traffic CHannel)
� All packet data traffic channels are uni-
directional.
� Uplink (PDTCH/U) for a mobile
originated packet transfer.
� Downlink (PDTCH/D) for a mobile
terminated packet transfer.
Packet service channel
PDTCH/U PDTCH/D
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PBCCH (Packet Broadcast Control CHannel)
� The PBCCH broadcasts parameters used by the MS to access the network for packet transmission operation.
� The PBCCH also carries the information transmitted via the BCCH to allow circuit switching operation.
�The MS in GPRS attached mode monitors the PBCCH only, if PBCCH is available, otherwise, the BCCH shall be used to broadcast information for packet operation.
�The existence of the PBCCH in the cell is indicated on the BCCH via SI13.
Packet control channel
PBCCH
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PCCCH (Packet Common Control CHannel) � PPCH
� Downlink only, used to page MS.
� PRACH � Uplink only, used to request allocation of one
or several PDTCH/Us or PDTCH/Ds.
� PAGCH � Downlink only, used to allocate one or
several PDTCHs.
� PNCH� Downlink only, used to notify MS of PTM-M
call.
� If no PCCCH is allocated, the information for packet switching operation is transmitted on the CCCH. If a PCCCH is allocated, it may transmit information for circuit switching operation.
PPCH PRACH PAGCH
PCCCH
PNCH
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PDCCH (Packet Dedicated Control Channels)
� PACCH
�Bi-directional, used to transmit the
packet signaling in data transmission.
� PTCCH/U
�Used to transmit random access bursts
to allow estimation of the timing advance for one MS in packet transfer
mode.
� PTCCH/D
�Used to transmit timing advance
updates for several MS. One PTCCH/D
is paired with several PTCCH/U's.
PACCH
PDCCH
PTCCH/U PTCCH/D
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Combinations of Packet Logic Channel
Mode 3: PDTCH+PACCH+PTCCH
Mode 1: PBCCH+PCCCH+PDTCH+PACCH+PTCCH Mode 2: PCCCH+PDTCH+PACCH+PTCCH
In case of small GPRS traffic, GPRS and circuit services share the same BCCH and CCCH in the cell. In this case, only combination mode 3 is needed in the cell.
With the increase of traffic, the packet public channel should be configured in the cell. Channel combination mode 1 and mode 2 should be adopted.
Mode 4: PBCCH+PCCCH
(PCCCH=PPCH+PRACH+PAGCH+PNCH)
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Packet Wireless Channel Configurations
� Reason of adopting static PDCH
� To enable that GPRS MS is constantly online in the cell.
� To ensure certain QoS of GPRS services.
� Reason of adopting dynamic PDCH
�GPRS and GSM share wireless resources.
�Wireless resources should be adopted in priority; on the other hand,
QoS of voice services should be ensured.
� In a cell, the percentage of packet switching services and the
percentage of circuit switching services are constantly changing.
�Dynamic PDCH is not visible for voice services.
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Packet Wireless Channel Configurations
� General principles
� The cell should be configured with static PDCH to enable MS to be normally
attached on GPRS network as well as certain QoS of GPRS services.
�Dynamic PDCH should be configured according to the GPRS traffic forecast,
which should be adjusted as TCH or PDCH usable in the operation process
according to the cell traffic status.
�Circuit switching services can seize the channel used by GPRS services.
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Mapping of Packet Logic Channel
I = Idle frame T = Frame used for PTCCHB0 ~ B11 = Radio blocks
51250
B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11T I T I
456 bits
0 1 2 3 4 5 6 7
1 TDMA frame
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
� A radio block is a 4-normal-burst sequence that carries a RLC/MAC PDU
(Protocol Data Unit).
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Mapping of Packet Logic Channel
51
4
3
5
6
7
0
1
2 B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11T I T I
500
BCCH
PDCH
TCH
S B B B B C C C C F S CC C C C C C C F S C C CCC C C C F S C C C C C CC C F S C C C C C C C C I
T T T T T T T T T T T S T T T T T T T T T T T T IT
F
25
2512
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Transmission Principle of Data Packet on Um Interface
Subscriber data
RLC/MAC headLLC headSNDCP head
Subscriber IP packet
LLC FCS
SNDCP PDU
LLC PDU
RLC/MAC block
Physical layer
B0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11T I T I
NB
NB
NB
NB
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Allocation of Wireless Packet Resources
� Wireless resource allocation and wireless transmission adopt the wireless block (BLOCK) as the
basic unit.
� Each PDCH can be used by several MSs; each MS can use multiple PDCHs at the same time.
B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11B0
B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11B0
B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11B0
MS3MS2
TS 0
TS 1
TS 2
MS1
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Basic Conceptions about Radio Block
� USF(Uplink State Flag) is sent in all downlink RLC/MAC blocks
and indicates the owner or use of the next uplink Radio block
on the same timeslot.
� The USF field is three bits in length
B11B10 B9B8 B7 B6
B5 B4 B3B2 B1 B0
T
I
T
I
UL
DL
USF=1USF=1
USF=1USF=2
USF=2USF=3
USF=3USF=3
USF=3USF=4
USF=4USF=4
T
I
T
I
USF=1
USF=2
USF=3
USF=4
MS1
MS2
MS3
MS4
USF=1
……
B0 I……
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Basic Conceptions about Radio Block
� TBF (Temporary Block Flow)
� A Temporary Block Flow (TBF) is a physical connection used by the two
RR entities(the RR entity of the MS and that of the BSS) to support the
unidirectional transfer of LLC PDUs on packet data physical channels.
�A TBF is temporary and is maintained only for the duration of the data
transfer.
� TFI (Temporary Flow Identity)
�Each TBF is assigned a Temporary Flow Identity (TFI) by the network.
�The TFI field is five bits in length.
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Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
4.1 Packet Channels
4.2 Medium Access Modes
4.3 MS Multi-TS Ability
4.4 Power Control
4.5 Network Control Modes
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Medium Access Modes
� Uplink resource allocation mode
�Dynamic allocation (supported by all MSs and all networks)
− The mobile station detecting an assigned USF value for each assigned PDCH and block or group of four blocks that it is allowed to transmit on that PDCH.
� Fixed allocation (supported by all MSs and all networks)
− Fixed bit mapping is adopted to determine the allocated blocks in the allocation period without an assigned USF.
�Extended dynamic allocation (optional for the network)
− The mobile station detecting an assigned USF value for any assigned PDCH allowing the mobile station to transmit on that PDCH and all higher numbered assigned PDCHs in the same block or group of four blocks.
� Downlink resource allocation mode
�Dynamic allocation and fixed allocation.
HUAWEI TECHNOLOGIES CO., LTD. Page 80All rights reserved
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
4.1 Packet Channels
4.2 Medium Access Modes
4.3 MS Multi-TS Ability
4.4 Power Control
4.5 Network Control Modes
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MS Multi-TS Ability
� Concept of MS multi-TS ability
� Types
− Type 1: Non-simultaneous TRX
− Type 2: Simultaneous TRX
� the multi-TS ability level is 1-29; the bigger the level, the stronger the multi-TS ability.
− 1~12 (Type 1),up to 4 timeslots in any direction
− 13~18 (Type 2),ranges between 3~8 timeslots
− 19~29 (Type 1)
� BSS allocates resources according to the MS multi-TS ability, requested QoS and
current resource configuration.
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Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
4.1 Packet Channels
4.2 Medium Access Modes
4.3 MS Multi-TS Ability
4.4 Power Control
4.5 Network Control Modes
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Power Control
� Power control can improve the spectrum usage and system capacity as
well as reduce MS power consumption.
� As there is no continuous bi-directional connection in the packet data
transmission process, GPRS power control is very complicated.
� Uplink power control includes open-loop and close-loop power control.
� About downlink power control, there is no specific definition in protocol. It
lies on the BTS and its algorithm needs information about downlink, so
downlink power control needs MS sends channel quality reports to BTS.
HUAWEI TECHNOLOGIES CO., LTD. Page 84All rights reserved
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
4.1 Packet Channels
4.2 Medium Access Modes
4.3 MS Multi-TS Ability
4.4 Power Control
4.5 Network Control Modes
HUAWEI TECHNOLOGIES CO., LTD. Page 85All rights reserved
Network Control Modes
� During the network controlled cell re-selection, the network may request measurement reports from the MS and control its cell re-selection. Hence, three types of mode are defined as follows:
� NC0: Normal MS controls
� NC1: MS control with measurement reports
� NC2: Network control
� The network subsystem must support NC0 and should gradually support NC1 and NC2.
HUAWEI TECHNOLOGIES CO., LTD. Page 86All rights reserved
Network Control Modes
MS NC0 NC1
NC2
The MS shall perform autonomous cell re-selection
MS
The MS shall perform autonomous cell re-selection
The MS shall send
measurement reports
to the network
MS BTS
MR
Cell re-selection
command
The MS shall not
perform autonomous cell
re-selection
HUAWEI TECHNOLOGIES CO., LTD. Page 87All rights reserved
Chapter 1 Chapter 1 GPRS System OverviewGPRS System Overview
Chapter 2 GPRS Achitecture Chapter 2 GPRS Achitecture
Chapter 3Chapter 3 GPRS Network Interfaces & ProtocolsGPRS Network Interfaces & Protocols
Chapter 4 Chapter 4 GPRS Wireless SubsystemGPRS Wireless Subsystem
Chapter 5 Chapter 5 GPRS Location AreaGPRS Location Area
HUAWEI TECHNOLOGIES CO., LTD. Page 88All rights reserved
Relationship among Location Areas
CELL
CELL
CELL
CELL
RA1
RA2
CELL
CELL
RA3
CELL
CELL
CELL
SGSN1SGSN2
BSC1
BSC2
BSC3
LA1 LA2
HUAWEI TECHNOLOGIES CO., LTD. Page 89All rights reserved
� MCC:Mobile Country Code, it consists of 3 digits. For example:
The MCC of China is "460"
� MNC:Mobile Network Code, it consists of 2 digits. For example:
The MNC of China Mobile is "00"
� LAC:Location Area Code, it is a two bytes hex code. The value
0000 and FFFF is invalid
� For example: 460008C90
Location Area Identification
MCC MNC LAC
LAI (Location Area Identification)
HUAWEI TECHNOLOGIES CO., LTD. Page 90All rights reserved
RAI
� Routing area is the sub-set of the location area. In special cases, the two
areas are equal
� The division of the routing area is related with traffic distribution and
SGSN processing ability
Location Area Identification
MCC MNC LAC RAC
Routing Area Identification
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CGI
Location Area Identification
MCC MNC LAC CI
CGI
� CI (Cell Identity): This code uses two bytes hex code to identify the radio cells within a LAI.
� RAC is only unique when presented together with LAI.
� CI is only unique when presented together with LAI or RAI.
� CGI = MCC+MNC+LAC+{RAC}+CI
RAC
Routing Area Identification
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CGI
Relationship among Location Areas
� LAI
�MCC+ MNC+ LAC
LAI
� RAI
�MCC+ MNC+ LAC+RAC
� CGI /CellID
�MCC+ MNC+ LAC+{RAC}+CI
RAI
HUAWEI TECHNOLOGIES CO., LTD. Page 93All rights reserved
Summary
� GPRS System Overview
� GPRS Achitecture
� GPRS Network Interfaces & Protocols
� GPRS Wireless Subsystem
� GPRS Location Area
www.huawei.com
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