1. General Packet Radio Service
王詔丘

2. GPRS History
Established by ETSI(European
Telecommunications Standards
Institute)
GSM phase 1 --- 1992
GSM phase 2 --- 1996
GPRS begin in 1994 and published at
the end of 1997

3. General Packet Radio Service
Packet switching
GPRS is evolved from GSM by introducing
two new core network nodes SGSN and
GGSN
Existing GSM nodes(BSS,MSC/VLR and
HLR) are upgraded
Concept foresees bit rates of nearly
170kb/s
QoS Support ： service
precedence 、 delay 、 reliability 、 mean
throughput 、 peak throughput etc. QoS

4. General Packet Radio Service
Several users can use the same channel
simultaneously
Always on line
Radio resource allocation
Charging is based on amount of transmitted
data
No need to access HLR for every GPRS
packet
Burst data transmission

5. GPRS Objectives
GPRS uses packet switched resource allocation
Dynamic channel allocation
1 to 8 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
Efficient delivery of SMS over the GPRS air
interface
Connections with data networks
IP network,X.25,GPRS own protocols

6. GPRS Development
Phase
Point-to-Point
Point-to-Multipoint
Class
Support GPRS and other GSM simultaneously
Support GPRS and GSM network parallel
Only GPRS
Multi-slot Type
Half-Duplex
Full-Duplex

7. Service type of GPRS
GPRS provides two types of services:
PTP (Point-To-Point)
Connectionless: IP
Connection-oriented: X.25
PTM (Point-To-Multipoint)
Multicast Service (PTM-M)
Group Call Service (PTM-G)

8. GPRS Applications
WWW
FTP
Telnet
Chat
E-mail
Image
Audio
Video
GPS(Global Positioning System)

9. GSM Architecture
MS(Mobile Station)
BSS(Base Station Subsystem)
BTS(Base Transceiver Station)
BSC(Base Station Controller)
MSC(Mobile Switching Center)
PSTN(Public Switched Telephone Network)
HLR(Home Location Register)
VLR(Visitor Location Register)
AUC(Authentication Center)

10. GSM Architecture

11. GPRS Architecture

12. Comparison between GPRS &
Circuit-switched

13. GPRS Architecture

14. GPRS Components
GPRS support node(GSN)
Packet routing and transfer within PLMN(Public
Land Mobile Network)
Gateway GPRS support node(GGSN)
Acts as a logical interface to external
PDN(Packet Data Network)
Maintains routing information used to tunnel
the PDUs(Protocol Data Unit) to the SGSN
currently serving the MS(Mobile Station)
Serving GPRS support node(SGSN)
Delivery of packets to the MSs within its
service area

15. Mobile Transmission
SGSN(SGSN-S) encapsulates the packets
transmitted by the MS and routes them to the
appropriate GGSN(GGSN-S)
Based on the examination of the destination
address, packets are then routed to the GGSN-D
through the packet data network
The GGSN-D checks the routing context
associated with the destination address and
determines the SGSN-D and relevant tunneling
information
Each packet is then encapsulated and forwarded
to the SGSN-D, which delivers it to the
destination mobile

16. Simple example of
transmission

17. Packet Data Transmission
Scenario
Mobile-originated
MS to some LAN host
Mobile-terminated
Receive packet from some host when MS is in
Home Public Land Mobile Network （ PLMN ）
Mobile-terminated
Receive packet from some host when MS is
roaming at some Visited Public Land Mobile
Network （ PLMN ）

18. Simple example of routing

19. GPRS Architecture
MS
BS
BS
BS
BS
MS
B SC
B SC
MS
MS
MS
BS
BS
BS
BSC
BSC
MS
MS
S GSN
BS
In terne t
PS TN
HLR
VLR
S S7
MSC
MS
Data
Voice
SS7 si gnaling
Voice and data
Air interface
S GSN
GGS N
X.2 5
Intr a-P LMN
Back bone
BG
I nter -P LMN
Back bone
Host
R

20. GPRS Coding Scheme
Best reliability : CS-1
No reliability : CS-4
Maximum data rate :
171.2Kbps(21.4Kbps x 8) with eight
time slots

21. FDMA & TDMA

22. Mobility Management
Two encapsulation schemes:
Between GSNs
Between MS and SGSN
Before MS sends data, MS has to attach
to GPRS using an attachment procedure
When moving to another SGSN(location
update), GGSN and GR/HLR are informed
about the new routing context

23. Mobility Management
State Diagram

24. GPRS Protocols
Sub-Network Dependent Convergence Protocol (SNDCP)
maps a network-level protocol
provides compression, segmentation and multiplexing of
network-layer messages to a single virtual connection
Logical Link Control (LLC)
assures the reliable transfer of user data across a
wireless network
Base Station System GPRS Protocol (BSSGP)
processes routing and QoS information
uses the Frame Relay Q.922 core protocol
GPRS Tunnel Protocol (GTP)
tunnels the protocol data units between GSNs

25. GPRS Protocols
GPRS Mobility Management (GMM)
handles roaming, authentication, and selection of
encryption algorithms
Network Service
maps BSSGP's service requests to the Frame Relay Q.922 Core
Radio Link Control(RLC)/MAC
Enable multiple MSs to share a common transmission medium
which consist of several physical channels
Physical Link Sublayer(PLL)
Data coding, detection and correction
Physical RF Sublayer(RFL)
Perform the modulation and demodulation of the physical
waveforms

26. Protocol Architecture

27. Air Interface – Physical Layer
GPRS air interface protocol is concerned
with communication between MS and BSS
Physical Channel divided into Packet Data
Channel （ PDCH ） and Traffic Channel
（ TCH ），
PDCH --- Dedicated to Packet Data
Traffic ，
TCH --- GSM Voice or Data Traffic 。
Allocation of TCHs and PDCHs is done
dynamically according to the 「 Capacity-
on-demand 」 principles

28. GPRS Architecture

29. GPRS Protocol Stack

30. GPRS Logical Channels
Packet Broadcast Control Channel(PBCCH)
Transmits system information to all GPRS
terminals in a cell
Packet Common Control Channel(PCCCH)
Initiate packet transfers or respond to paging
messages
Packet Traffic Channels(PTCH)
Channel resource allocation

31. GPRS Logical Channels(cont.)

32. Uplink

33. Downlink

34. HSCSD and EDGE
High-Speed Circuit-Switched Data （ HSCSD ）
Multi-timeslot
Using V42bis coding scheme can achieve 14.4Kbps
Maximum data rate : 115.2Kbps(14.4Kbps * 8)
Circuit switching
Enhanced Data for GSM Evolution （ EDGE ）
Maximum data rate : 384kbps
EDGE use the new Modulation Technique --- eight-phase-
shift （ 8PSK ）
Support Packet switching and Circuit switching
simultaneously

35. GPRS Glossary
ETSI(European Telecommunications Standards Institute)
MS(Mobile Station)
BSS(Base Station Subsystem)
BTS(Base Transceiver Station)
BSC(Base Station Controller)
MSC(Mobile Switching Center)
PSTN(Public Switched Telephone Network)
HLR(Home Location Register)
VLR(Visitor Location Register)
AUC(Authentication Center)
GPRS support node(GSN)
Gateway GPRS support node(GGSN)
Serving GPRS support node(SGSN)
packet data network(PDN)
Public Land Mobile Network （ PLMN ）
Sub-Network Dependent Convergence Protocol (SNDCP)
Logical Link Control (LLC)
Base Station System GPRS Protocol (BSSGP)
GPRS Tunnel Protocol (GTP)
GPRS Mobility Management (GMM)
Packet Data Channel （ PDCH ）
Traffic Channel （ TCH ）
Packet Broadcast Control Channel(PBCCH)
Packet Common Control Channel(PCCCH)
Packet Traffic Channels(PTCH)
High-Speed Circuit-Switched Data （ HSCSD ）
Enhanced Data for GSM Evolution （ EDGE ）

36. Reference
J. Cai and DJ Goodman, General Packet Radio
Service in GSM, IEEE Communications,
vol. 35, no. 10, pp. 122-131, October 1997
G. Brasche and B. Walke, Concepts, Services, and
Protocols of the New GSM Phase
2+ General Packet Radio Service, IEEE
Communications, vol. 35, no. 8, pp. 94-104, Aug
1997
C. Bettstetter, GSM PHASE 2+ GENERAL
PACKET RADIO SERVICE
GPRS:ARCHITECTURE, PROTOCOLS AND AIR
INTERFACE, IEEE Communications,1997