General Packet Radio Service

1
General Packet Radio Service

• ???

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 Supportservice precedence?delay?
  reliability?mean throughput?peak throughput etc.
  QoS parameters

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
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)

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 Phase2 General Packet
  Radio Service, IEEE Communications, vol. 35, no.
  8, pp. 94-104, Aug 1997
• C. Bettstetter, GSM PHASE 2 GENERAL PACKET RADIO
  SERVICE GPRSARCHITECTURE, PROTOCOLS AND AIR
  INTERFACE, IEEE Communications,1997