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Understanding GPRS

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  • Bearer service allows trasnmission between network interfaces,.UNI. GMSK is minimum phase shift keying.
  • Transcript

    • 1. General Packet Radio Service (GPRS)May 7, 2010 1
    • 2. General Packet Radio Service (GPRS) Presented by: Shahryar AliMay 7, 2010 2
    • 3. GSM PHASE 2+ GENERAL PACKET RADIO SERVICE GPRS: Architecture,Protocols,and Air interface Christian Bettstetter,Hans-Jorg Vogel,and Jorg Eberspacher TECHNISCHE UNIVERSITÄT MÜNCHEN (TUM) May 7, 2010 IEEE Communications Surveys 3
    • 4. INTRODUCTIONMay 7, 2010 4
    • 5. About GPRS• Bearer service for GSM• Data rate : 14.4 to 115.2 Kbps• Modulation Technique: GMSK• Type of Connection: Packet - Switched Technology• Replacement of HSCSD May 7, 2010 5
    • 6. What was lacking in HSCSD?• Connection setup time too long• Inefficient resource utilization for bursty traffic.• Higher call blocking probability• High cost of service May 7, 2010 6
    • 7. GPRS: Benefits• High speed• Efficient resource utilization.• Important step on the path to 3G• Billing : Amount of data transferred May 7, 2010 7
    • 8. GSM : Review• GSM-900:  Uplink: 890 MHz – 915 MHz (25 MHz)  Downlink: 935 MHz – 960 MHz (25 MHz)  Data rate: 9.6kbps• Frequency Division Multiple Access  Channels are 200 kHz wide.• Time Division Multiple Access  8 timeslots each channel May 7, 2010 8
    • 9. Network ArchitectureMay 7, 2010 9
    • 10. GSM: System Architecture• Mobile Station (MS) Mobile Equipment (ME) Subscriber Identity Module (SIM)• Base Station Subsystem (BSS) Base Transceiver Station (BTS) Base Station Controller (BSC)• Network Subsystem(NSS) Mobile Switching Center (MSC) Home Location Register (HLR) Visitor Location Register (VLR) Authentication Center (AUC) Equipment Identity Register (EIR) May 7, 2010 10
    • 11. GSM System Architecture PSTN ISDN PDNMS BTS MSC BSC GMSCMS BTS BSCMS VLR EIR BTS AUC HLR May 7, 2010 11
    • 12. GPRS Network Elements• GPRS Architecture is same as GSM except few modifications:  GPRS includes GSNs 1. SGSN 2. GGSN  GPRS Register May 7, 2010 12
    • 13. GPRS System Architecture SMS-GMSC Other GPRS Gd PLMNMS BTS SGSN Gp BSC GGSN GbMS Gn GGSN Gf BTS PDN BSC Gr Gi Gs GcMS EIR BTS HLR+GPRS May 7, 2010 13 Register MSC/VLR
    • 14. SGSN – Serving GPRS Support Node• Delivers data packets to mobile stations and vice versa.• Detect and Register new GPRS MS in its serving area.• Packet Routing• Authentication May 7, 2010 14
    • 15. GGSN – Gateway GPRS Support Node• Interfaces GPRS backbone network & external packet data networks• Converts the GPRS packets from SGSN to the PDP format• Stores profile of the user in its location registerMay 7, 2010 15
    • 16. GPRS Register• GPRS Register is integrated with GSM-HLR.• Maintains the GPRS subscriber data and Routing information.• Stores current SGSN address May 7, 2010 16
    • 17. GPRS Classes• Class A – MS supports simultaneous operation of GPRS and GSM services• Class B – It can only use one of the two services at a given time.• Class C - MS can attach for either GPRS or GSM services May 7, 2010 17
    • 18. GPRS states• Idle• Ready• Standby May 7, 2010 18
    • 19. GPRS—General packet radio service H.kan Granbohm and Joakim Wiklund Ericsson ReviewMay 7, 2010 19
    • 20. Overview GPRS Standard GSM to GPRS Air Interface Resources GPRS Multislot Classes Ericsson’s implementation of GPRS GPRS Attach PDP context Activation GPRS security Protocol Architecture May 7, 2010 20
    • 21. GPRS Standard• Evolution of the GSM standard• European Telecommunications Standards Institute.(ETSI)• 3rd Generation Partnership Project (3GPP) May 7, 2010 21
    • 22. GSM to GPRS• SGSN and GGSN• Hardware Upgrades – BSS – PCU is added to BSC• Software Upgrades – MSC/VLR – HLR May 7, 2010 22
    • 23. Air Interface Resources: GSMMay 7, 2010 23
    • 24. Air Interface Resources: GPRS• GPRS allows several users to share the same air-interface resources.• Packet data channel (PDCH) May 7, 2010 24
    • 25. Packet-switched transmission over Air interfaceMay 7, 2010 25
    • 26. GPRS users share the pool of Resources May 7, 2010 26
    • 27. GPRS Multislot classesGPRS Slots Max Max Coding schemes Upload Downloadclass used (kpbs) (kpbs) Coding Data scheme rate(kbps) 2 1,2 8 - 20 16 - 40 CS-1 8.0 4 1,3 8 - 20 24 - 60 CS-2 12.0 6 2,3 16 - 40 24 - 60 CS-3 14.4 8 1,4 8 - 20 32- 80 CS-4 20.0 10 2,4 16 -40 32- 80 12 4,4 32 -80 32- 80 May 7, 2010 27
    • 28. Ericsson’s implementation of GPRS• Fast deployment while keeping entry costs low.• SGSN and GGSN combined into one physical node.• Ericsson’s AXB 250 platform.• Hardware redundancy and the open telecom platform (OTP)• (O&M) activities toward the GSNs are handled via a Java-based graphical user interface (GUI), called the Packet eXchange.• A router function has been integrated into the GSN May 7, 2010 28
    • 29. GPRS ATTACH HLR MSC/VLR 3MS 3 BSC 2 1 3 2 1 SGSN GGSN 4 2 BTS IP 4 networ1 .MS Request k2. Authentication insertion3. Subscriber Data Backbone4. Attach Confirmation Network May 7, 2010 29
    • 30. PDP context activation. HLRMS BSC 1 1 SGSN[DNS] GGSN 5 BTS 4 IP 2,3 networ1 .MS Request k 4 42. Request Validates3. APN is sent to DNS Backbone4. GTP tunnel. Network5. IP address allocation to MS May 7, 2010 30
    • 31. GPRS SECURITY• User authentication (GSM style)• The GPRS tunneling protocol (GTP) encapsulates user packets.• IPSec functionality provides secure connections between the SGSN and GGSN May 7, 2010 31
    • 32. Protocol Stack MS BSS (PCU) SGSN GGSNApplicationIP / X.25 IP / X.25SNDCP SNDCP GTP GTP LLC UDP/ UDP/ LLC LLC TCP TCP RLC RLC BSSGP BSSGP IP IP Frame Frame MAC MAC L2 L2 Relay RelayGSM RF GSM RF GSM RF L1 L1 L1 Um Gb Gn Gi May 7, 2010 32
    • 33. Real time Video Communications over GPRS N.Fabri,Stewart Worall,Abdul Sadka,Ahmet Kandoz University of Surrey ,United Kingdom May 7, 2010 33
    • 34. GPRS - Applications• Chat• Textual and visual information• Web browsing• Document sharing, Email• Vehicle Positioning• Home Automation May 7, 2010 34
    • 35. Need of the technology• Enhanced Multimedia services on go• Integration of video, audio and data i.e rich web contents – Implication on design • Quality of service • Access to some bearer channels • Use of standardised protocols• Presents the model using ETSI`s GPRS as an access channel for the services May 7, 2010 35
    • 36. GPRS support for video com..Two main reasons• Multislotting – increases the throughput capabilities of a single terminal• IP Support – To work with internet multimedia applications May 7, 2010 36
    • 37. • SNDCP: formats network packets for transmission over GPRS and multiplexing of data• LLC: links MS to SGSN• RLC/MAC layer : fixed length segmented data – Access to physical channel – Access method May 7, 2010 37
    • 38. Protocol Architecture (Review)May 7, 2010 38
    • 39. Video communication• Video over IP is used• Real time service – Streaming of stored video – Conversational video• PDTCH: Packet Data traffic Channel is used May 7, 2010 39
    • 40. Channel Protection Schemes• Convolutional codes are used for error detection and correction May 7, 2010 40
    • 41. Video Compression• Two main standardized codecs – ITU-T`s H.26 – ISO MPEG-4• Bothe are based on the same technology – MPDCT• However MPEG-4 is more efficient – It manipulate objects in realtime by use of BIFS To vary volume, position, colour etc May 7, 2010 41
    • 42. MPEG-4 Encoder• It produces three streams – Audio – Video – BIFS• Flex Mux tool is used to combine the streams before transmission May 7, 2010 42
    • 43. Error Resilience Tools• Places the coded data in regular sized packets with a synchronization sequence• Any packet can be decoded independently• Data Partitioning: separates motion and header data from textured data in each video packet. – Less distortion in original data – Not all are very sensitive to error – Use of Reversible Variable Length Codes (RVLCs) May 7, 2010 43
    • 44. MPEG-4 Frames– Intra frames • Independent of any frames • Used to prevent error propagation by regularly refreshing the display • Much larger comparatively • Dropping the bit rate • Data loss can occur even when there is no channel errors.– Inter frames • Predicted from previous framesMay 7, 2010 44
    • 45. Adaptive Inter Refresh (AIR)• Codes fixed number of intra block in each frame• SAD is used to mark each block as intra coded by comparing it to a threshold value. May 7, 2010 45
    • 46. Quality performance of AIRMay 7, 2010 46
    • 47. Channel Allocation• PRMA (Packet Resource Multiple Access)is used• The MS sends access burst and is assigned Temporary Block Flow (TBF) untill LLC PDUs are to transmit.• Normal delay is from 200 to 300ms• Not suitable for critical data May 7, 2010 47
    • 48. References:• Mobile communication by schiller• www.wikipedia.org• Wireless and mobile communication by W.stallings May 7, 2010 48
    • 49. QUESTIONS???May 7, 2010 49

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