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  1. 1. General Packet Radio Service 王詔丘
  2. 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. 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. 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. 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. 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. 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. 8. GPRS Applications WWW FTP Telnet Chat E-mail Image Audio Video GPS(Global Positioning System)
  9. 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. 10. GSM Architecture
  11. 11. GPRS Architecture
  12. 12. Comparison between GPRS & Circuit-switched
  13. 13. GPRS Architecture
  14. 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. 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. 16. Simple example of transmission
  17. 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. 18. Simple example of routing
  19. 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. 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. 21. FDMA & TDMA
  22. 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. 23. Mobility Management State Diagram
  24. 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. 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. 26. Protocol Architecture
  27. 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. 28. GPRS Architecture
  29. 29. GPRS Protocol Stack
  30. 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. 31. GPRS Logical Channels(cont.)
  32. 32. Uplink
  33. 33. Downlink
  34. 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. 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. 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