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GPRS

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GPRS

  1. 1. General Packet Radio Service (GPRS) "This report was prepared for Professor L. Orozco-Barbosa in partial fulfillment of the requirements for the course ELG/CEG 4183" Sylvain FIORONI Thierry BOUSSAC 3/11/2002
  2. 2. Outline <ul><li>Context of GPRS </li></ul><ul><li>Architecture </li></ul><ul><li>Functioning </li></ul><ul><li>Future trends </li></ul>
  3. 3. Context of GPRS
  4. 4. Data transmission in wireless networks <ul><li>Key point of next generations cellular networks </li></ul><ul><li>GSM : uses CSD technology (Circuit Switched Data) </li></ul><ul><ul><li>9.6 kb/s bandwidth 1 </li></ul></ul><ul><ul><li>Essentially text application </li></ul></ul><ul><ul><ul><li>web browsing, WAP, SMS … </li></ul></ul></ul>
  5. 5. 3G networks <ul><li>3G : UMTS </li></ul><ul><ul><li>384 kb/s – 2Mb/s </li></ul></ul><ul><ul><li>Multimedia applications : videoconference… </li></ul></ul><ul><ul><li>Very expensive (1) </li></ul></ul><ul><ul><li>Technology not yet ready (2) </li></ul></ul><ul><li>Need for a smooth transition  </li></ul><ul><ul><li>2.5 G Networks </li></ul></ul>
  6. 6. 2.5G Networks <ul><li>HSCSD : High Speed Circuit Switched Data </li></ul><ul><li>GPRS : General Packet Radio service </li></ul><ul><li>EDGE : Enhanced Data rates for Global Evolution </li></ul>
  7. 7. Architecture of GPRS
  8. 8. GPRS : General Packet Radio service <ul><li>Uses packet switching </li></ul><ul><li>Dynamic Timeslot allocation </li></ul><ul><li>Up to 8 timeslots in each direction </li></ul><ul><li>4 new coding schemes to reduce error control coding upon a sufficient link quality </li></ul><ul><li>theoretical throughput : </li></ul><ul><ul><li>8 timeslots, CS4 : 21.4kb/s => 8*21.4=171.2 kb/s </li></ul></ul><ul><ul><li>actually, only CS2 (1) available => 8*13.4=107.2 kb/s </li></ul></ul>
  9. 9. GPRS architecture
  10. 10. GPRS Components <ul><li>SGSN : (Serving GPRS Support Node) </li></ul><ul><ul><li>Equivalent to MSC in GSM </li></ul></ul><ul><li>GGSN : (Gateway GPRS Support Node) </li></ul><ul><ul><li>Equivalent to GMSC in GSM </li></ul></ul><ul><li>PCU : (Packet Coding Unit) </li></ul><ul><ul><li>Fragmentation of the packets into radio blocks </li></ul></ul>
  11. 11. GPRS interfaces <ul><li>GPRS Core Network : IP based network (1) </li></ul><ul><ul><li>Gn interface between xGSNs </li></ul></ul><ul><ul><li>Gp interface to other GPRS PLMN </li></ul></ul><ul><ul><li>Gi interface to other PSDN : </li></ul></ul><ul><ul><ul><li>Internet, Wap Gateway, Enterprise LANs… </li></ul></ul></ul><ul><li>GPRS Access Network </li></ul><ul><ul><li>Gb interface : from SGSN to PCUs </li></ul></ul><ul><ul><ul><li>Based on Frame Relay </li></ul></ul></ul><ul><ul><li>PCU-BSC : proprietary interface </li></ul></ul><ul><ul><ul><li>Called A-ter, A-bis GPRS, A-GPRS… (2) </li></ul></ul></ul>
  12. 12. GPRS interfaces <ul><li>Signaling Interfaces to GSM network (SS7 based) : </li></ul><ul><ul><li>Gr interface from SGSN to HLR </li></ul></ul><ul><ul><li>Gs interface from SGSN to MSC/VLR </li></ul></ul><ul><ul><li>Gd interface from SGSN to GMSC </li></ul></ul><ul><ul><li>Gc from GGSN to HLR </li></ul></ul><ul><ul><li>Gf from SGSN to EIR </li></ul></ul><ul><ul><li>… </li></ul></ul>
  13. 13. GPRS protocol stack
  14. 14. GPRS protocol stack <ul><li>Gb Interface : </li></ul><ul><ul><li>Network Service : part of frame relay network (defines end to end virtual circuits : NSVC (1) ) </li></ul></ul><ul><ul><li>BSSGP (BSS GPRS Protocol) </li></ul></ul><ul><ul><ul><li>routing to cells (Virtual Channels : BVC) </li></ul></ul></ul><ul><ul><ul><li>flow control for each cell and mobile station (2) </li></ul></ul></ul><ul><ul><li>LLC (Logical Link Control) </li></ul></ul><ul><ul><ul><li>Very similar to HDLC </li></ul></ul></ul><ul><ul><ul><li>Ciphering </li></ul></ul></ul>
  15. 15. GPRS protocol stack <ul><li>Gb interface </li></ul><ul><ul><li>SNDCP (Sub Network Dependent Converging Protocol) </li></ul></ul><ul><ul><ul><li>encapsulation of IP/X25 packets over lower layers </li></ul></ul></ul><ul><ul><ul><li>Compression </li></ul></ul></ul><ul><ul><li>Signalling : </li></ul></ul><ul><ul><ul><li>GMM (GPRS Mobility Management) : Attach, Routing Area Update procedures… </li></ul></ul></ul><ul><ul><ul><li>SM (Session Management) : PDP Context Activation </li></ul></ul></ul>
  16. 16. GPRS protocol stack <ul><li>Gn, Gp Interface : </li></ul><ul><ul><li>Based on TCP/UDP/IP </li></ul></ul><ul><ul><li>lower layers not specified (1) </li></ul></ul><ul><ul><li>TCP  X25, UDP  IP </li></ul></ul><ul><ul><li>GTP (GPRS Tunnelling Protocol) </li></ul></ul><ul><ul><ul><li>Encapsulation of packets over lower layers </li></ul></ul></ul><ul><ul><ul><li>mainly security function </li></ul></ul></ul><ul><ul><ul><li>Signaling functions </li></ul></ul></ul>
  17. 17. Functioning
  18. 18. Mobile Classes <ul><li>Class A : </li></ul><ul><ul><li>can be attached simultaneously to GSM and GPRS </li></ul></ul><ul><ul><li>can transmit voice and data at the same time </li></ul></ul><ul><li>Class B : </li></ul><ul><ul><li>can be attached simultaneously to GSM and GPRS </li></ul></ul><ul><ul><li>can transmit voice or data </li></ul></ul><ul><li>Class C : </li></ul><ul><ul><li>cannot be attached simultaneously to GSM and GPRS </li></ul></ul>
  19. 19. Attach procedure MS BSS SGSN GGSN Internet HLR Radius Gb Gr Gn Gi Gi GMM_Attach_Request (IMSI) MAP_update_location MAP_insert_subscr_data MAP_insert_subscr_data_ack MAP_update_location_comp GMM_Attach_Accept(P-TMSI)
  20. 20. PDP Context activation MS BSS SGSN GGSN Internet HLR Radius Gb Gr Gn Gi Gi SM_Act_PDP_Context_req(APN) GTP Create_PDP_cont_req(APN) Auth_request Auth_accept GTP Create_PDP_cont_acc(@IP) SM_Act_PDP_Context_resp(@IP)
  21. 21. PDP Context activation 193.148.25.89 MS BSS SGSN GGSN Internet HLR Radius Gb Gr Gn Gi Gi IP source:193.148.25.89 Dest : 134.214.164.24
  22. 22. <ul><li>Specification of the requested QoS on PDP context activation : </li></ul><ul><ul><li>Peak throughput </li></ul></ul><ul><ul><li>Mean throughput </li></ul></ul><ul><ul><li>Precedence : priority on MAC layer </li></ul></ul><ul><ul><li>Reliability : Functioning mode of LLC, RLC and GTP </li></ul></ul><ul><ul><li>Delay : responsibility of the operator </li></ul></ul>QoS Management Parameters of leaky bucket algorithm in BSSGP
  23. 23. Future trends <ul><li>UMTS ? </li></ul><ul><ul><li>experiences a lot of delay </li></ul></ul><ul><ul><ul><li>licence issue </li></ul></ul></ul><ul><ul><ul><li>very expensive, technology not ready </li></ul></ul></ul><ul><ul><li>Real need for high rates on mobile networks? </li></ul></ul><ul><ul><ul><li>Competition with local networks </li></ul></ul></ul><ul><li>GPRS and 2.5G can be a good compromise </li></ul><ul><ul><li>may last longer than it was supposed to (2) </li></ul></ul>
  24. 24. Conclusion <ul><li>Is there a real need for data on cellular networks now ? </li></ul><ul><ul><li>currently too expensive : Mobile terminals, Utilization fees… </li></ul></ul><ul><ul><li>relative failure of WAP… </li></ul></ul><ul><ul><li>High competition with wireless LANs </li></ul></ul><ul><li>still waiting for a killer application </li></ul>
  25. 25. References <ul><li>[1] ETSI 3GPP TS 03.60, Digital cellular telecommunications system (Phase 2+) General Packet Radio Service (GPRS) Service description Stage 2, version 7.7.0 Release 1998 </li></ul><ul><li>[2] ETSI 3GPP TS 08.18, Digital cellular telecommunications system (Phase 2+); General Packet Radio Service (GPRS); Base Station System (BSS) - Serving GPRS Support Node (SGSN) BSS GPRS Protocol (BSSGP), version 8.9.0, Release 1999 </li></ul><ul><li>[3] ETSI(3GPP 03.6, Digital cellular telecommunications system (Phase 2+);General Packet Radio Service (GPRS);Overall description of the GPRS radio interface;Stage 2, version 8.9.0 Release 1999 </li></ul><ul><li>[4] Georgios Karagiannis, QoS in GPRS, Ericsson open report 5/0362-FCP NB 102 88 Uen, 2000-12-21 </li></ul><ul><li>[5] Xavier LAGRANGE, Philippe GODLEWSKI, Sami TABANNE, Réseaux GSM - DCS: des principes à la norme,Paris, HERMES, 1995 </li></ul>
  26. 26. Questions <ul><li>What are the three 2.5G networks ? </li></ul><ul><li>Why is the theoretical maximum throughput of GPRS unreachable ? </li></ul><ul><li>What are the 5 parameters of QoS defined in GPRS ? </li></ul><ul><li>What are the nodes that have been introduced with GPRS ? </li></ul><ul><li>What is GTP ? </li></ul>

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