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GPRS
byPrakshet ThapaMSD, Jawalakhel3G n GPRS SectionMob:9851144444
1
Contents• Evolution of Wireless • Introduction of GPRS• GPRS Architecture
• SGSN, GGSN, BG, DNS, CG
• GPRS characteristics • GPRS data rate• Session management in GPRS• Location management in GPRS• Routine Area Code• Radio Channels in GPRS• GPRS Roaming and Billing• Application
2
Cellular Evolution Timeline
Nepal TelecomMobile Service Directorate
3
Evolution of WCDMA CN
GSM
GPRS Edge PS
CS
CDMA2000CDMA
2G 2.5G 2.75G 3G
3GPP
3GPP2
Organization
4
What is GPRS•GPRS is the abbreviation of General Packet
Radio Service•GPRS provides end to end packet switch
service for user based on GSM•GPRS make the best use of existing GSM
network•GPRS provides highly efficient use of radio
resources•GPRS provides as high as 171.2Kbps
access rate
5
What is PS• PS is the packet switch network in WCDMA core
network• PS provides end-to-end packet switch service for
users• PS has almost the same elements and network
structure with GPRS• PS can provides access for GPRS radio access
equipment and 2/3G hybrid network• WCDMA-PS provides as high as 2Mbps access
rate
6
GPRS Network GMSC
ZXG10 GPRS System Structure
BSS
InternetX.25
ISDN
GPRS MS
TE
MSC
PCU
SGSN GGSN
GSNBackbone
Voice
Packet Data
CS service line
PS service line
GPRS Network
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RNC
Node B
TDM/ATM PSTN
IP
Iu-PS
Gn Gn
Gp
Gi
CG
Billing Center
Ga
HLR
MSC
GGSN
GMSC
Serving GPRS Support Node
Gateway GPRS Support Node
Inter-PLMN
Charging Gateway
BSCBTS
SGSN
Gb
Internet
PS Network
8
Iu-CS
A
Gr Gc
GPRS Network Elements
GPRS Architecture is same as GSM except few hardware modifications :
GPRS includes GSNs SGSN : Serving GPRS Support
Node GGSN : Gateway GPRS Support
Node
9
Interfaces• Gb – Connects BSC with SGSN
• Gn – SGSN – SGSN/GGSN (in the same network)
• Gp – SGSN –GGSN (in different networks)
• Gi – Connects PLMN with external PDNs
• Gr – To exchange User profile between HLR & SGSN
• Gs – To exchange Database between SGSN & MSC
• Gd – Interface between SMS & GPRS
• Gf – For equipment querying at registering time
10
SGSN Function
•Perform mobility management for GPRS terminals (attach/detach, user authentication, ciphering, location management)
•Route packets between mobile terminals and the GGSN
▫Detect and Register new GPRS MS in its serving area
▫Its location register stores location info. & user profiles
•Charging information
11
GGSN Function
•Routing Select, PDP PDU Transfer, Address Mapping
•Tunnel Capsulate and Transfer •Subscriber Data Management•Session Management•IP Address Management•Charging Information Select
12
DNS Function
When activating PDP, APN is used to get the IP address of GGSN Get old SGSN IP address during the process of inter-SGSN routing area
update
SGSN GGSN(A)
MS
BSS
GPRS Core NetworkGPRS Core Network
ISP AISP A
ISP BISP B
Internet/IntranetGGSN(B)
DNS
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BC
GPRS Bore
TCP/IP
SGSN/GGSN SGSN/GGSN
CG
TCP/UDPGTP'
FTAM/FTPFTAM/FTP
CG OMM Server CG OMM Client CG OMM Client
CG Function
14
CG Function
•CG implements the following functions:▫CDRs generated by GSNs collected in real
time▫Buffering the CDRs▫Preprocessing the CDRs, such as CDR
consolidation and filtering, deleting certain CDR fields, and modifying or adding some CDR fields.
▫Transferring the CDRs to the BC.
15
SGSN GGSN
Backbone Network
S-SMT-CDRS-CDR M-CDRS-SMO-CDR G-CDR
CG CDRs
16
BG Function
•BG implement these functions▫Security: IPSec and firewall ▫Routing protocol: BGP▫Billing protocol: negotiated by operators,
collect billing information•Usually based on router•Can be the same equipment as GGSN
17
HLR/AUC Function
•Store and update GPRS user profile•User authentication•Processing the location/routing
information related to mobility management and route selection, such as▫Store and update user’s serving SGSN
number and address▫MS reachable or not flag
18
MSC/VLR Function
•When Gs interface is installed, MSC/VLR can support:▫SGSN and MSC/VLR relationship
establishment and maintenance▫GPRS joint mobility management▫Joint IMSI/GPRS attach/detach▫Joint location area/routing area updating▫Circuit paging coordination function
Improve the radio resource utilization ratio
19
GPRS characteristics•GPRS uses packet switched resource
allocation▫resources allocated only when data is to be sent/received
•Flexible channel allocation▫one to eight time slots
▫available resources shared by active users
▫up and down link channels reserved separately
▫GPRS and circuit switched GSM services can use same time slots alternatively
•Traffic characteristics suitable for GPRS▫Intermittent, bursty data transmissions
▫Frequent transmissions of small volumes of data
▫Infrequent transmission of larger volumes of data
20
Air interface resources
0
2
4
6
8
10
12
14
16
1:00 PM 1:15 PM 1:30 PM 1:45 PM
TCH
An example of occupied TCH capacity by CS traffic during busy hour with n% blocking
0
2
4
6
8
10
12
14
16
3:00 6:00 9:00 12:00 15:00 18:00 21:00 0:00
TCH
Capacity occupied by CS traffic
FreeCapacityGPRS "steals" any TCH
capacity not used by CStraffic
21
Statistical Multiplexing22
23
GPRS Data Rates
Scheme Data Rate (kbps)
Note
CS-1 9.05 Best performance for low C/I values
CS-2 13.4 CS-2 and CS-3 have similar performance
CS-3 15.6 CS-2 and CS-3 have similar performance
CS-4 21.4 Needs high C/I values
24
GPRS Terminals
•Class A – support simultaneous GPRS and GSM voice services with two channels
•Class B – support either GPRS and GSM voice services with simultaneous network attachment
•Class C – support only GPRS service
Iu mode
•CS/PS mode: Same as Class A in A/Gb mode
•PS mode: MS can only operate packet switched services
•CS mode: MS can only operate circuit switched services
25
APN information
26
SESSION MANAGEMENT IN GPRS
27
Attachment & Detachment Procedure
•GPRS attach- User is registered in SGSN, after authentication
check from HLR- SGSN assigns P-TMSI to MS
•GPRS detach- Disconnection of MS from GPRS network is called
GPRS detach- It can be initiated by MS or by network(SGSN or
HLR)
28
Session Management
•Mobile Station applies for PDP address•For each session PDP context is created & it
contains PDP addressed assigned to MSAddress of GGSN that servers access point
to PDN
•With active PDP context MS able to send or receive data packets
•Allocation of PDP address can be static or dynamic
29
PDP Context Activation30
LOCATION MANAGEMENT IN GPRS
31
State Model of GPRS MS
32
Location Management
Mobile station can be in 1 of the 3 states depending on traffic amount▫ Idle : MS is not using GPRS service
▫ Ready : Performing GPRS Attach, MS gets into READY State
▫ Standby : When MS does not send any packets for longer period of time,
Ready timer Expires
33
Routing Area Update
•GSM Location Area(LA) is divided into several Routing Areas(RA)
•RA consists of several cells•SGSN is informed when MS moves to a new
RA•MS sends a “Routing Area Update Request”
to its assigned SGSN
34
Routing Area Update35
Channels in GPRS
•Logical Channel▫Traffic Channels▫Signaling Channels (Control Channels)
•Physical Channels
36
Logical ChannelsGroup Channel Function Direction
Packet data traffic channel
PDTCH Data traffic MS BSS
Packet broadcast control channel
PBCCH Broadcast control
MS BSS
PRACH Random access
MS BSS
PAGCH Access grant
MS BSS
PPCH Paging MS BSS
PNCH Notification MS BSS
PACCH Associated control
MS BSS
PTCCH Timing advance control
MS BSS
Packet common control channel (PCCCH)
Packet dedicated control channels
37
Packet Data Channel(PDCH)
•Physical Channel for GPRS Traffic
•PDCH are taken from all channels available in the cell
•Depending on current traffic load and priority of service, the physical channel are allocated to either GPRS or GSM services.
•Physical channels not currently used by GSM can be allocated as PDCH to increase the QOS for GPRS
38
39
BTS BSCSGSN
GGSN
Internet
VISITEDPLMN
HOMEPLMN
BG
BG
GGSN
Home Operator
Visited Operator
AP
Visiting user selects to use home APN1
1
HomeDNS
my.isp.com
myoperator.fi.gprs
RootDNS
4 4Visited DNS asks GPRS root DNS:
"who knows the IP address for this name?”
VisitedDNS
3
3
SGSN asks for GGSN IP address (using APN as the key) from visited DNS
5
5
GPRS root DNS replies the home DNS address to visited DNS GRX
6
6
Visited DNS asks home DNS for GGSN address
7
7
Home DNS replies the GGSN IP address
8
8 Visited DNS replies SGSN
99
SGSN creates PDP context with home GGSN
2 MS sends "activate PDP context”
2
GPRS Roaming & GRX
Can pass through GRXs
BillingGGSN
MSC
PSTN
BSC
SGSN
GPRS Network
Charging Gateway
Mediation
MSC
Billing
40
Other Data related VAS
41
• MMS
• MVS
• Video On Demand
• Live TV
Applications
▫Standard data network protocol based IP based applications
WWW, FTP, Telnet, ...Any conventional TCP/IP based applications
▫GPRS specific protocol basedPoint-to-point applications
Toll road system, UIC train control systemPoint-to-multipoint applications
Weather info, road traffic info, news, fleet management
▫SMS delivery (GPRS as a bearer for SMS)
42
Thanks for listening
43