GSM & GPRS Primer

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GSM & GPRS Primer

  1. 1. GSM & GPRS PrimerErick O‟ConnorFebruary 2005
  2. 2. Topics Background General Packet Radio System (GPRS) • The history of cellular communications • Protocol layers • Key statistics • Key information – Worldwide subscribers • Dimensioning a Network – Top 20 global mobile operators • Mobility Management Global System for Mobile (GSM) Third-Generation Systems (UMTS) • The Radio environment • Evolution paths • Basestation & Network subsystems • Core components • Subscriber data & addressing • Circuit-switched network architecture • Overview of PDH transmission • Common Channel Signalling & GSM MAP©2001 - 2005 Erick O’Connor 2
  3. 3. History of Cellular Communications1960s to the Present Day
  4. 4. …the early years 1960 – 1970s • Idea of a cell-based mobile radio system developed by AT&T‟s Bell Labs in late 1960s • First commercial analogue mobile cellular systems deployed 1978 1980s (1st Generation Analogue Systems) • Usage in N.America grows rapidly – Advanced Mobile Phone System (AMPS) becoming the de facto standard • Europe, run by the PTTs, characterised by multiple incompatible analogue standards – Nordic Mobile Telecommunications (NMT-450) – Total Access Communications (TAC) – United Kingdom – C-Netz – West Germany – Radiocom 2000 – France – RTM / RTMS – Italy etc. etc. • Capacity limitations already becoming apparent by end of decade….©2001 - 2005 Erick O’Connor 4
  5. 5. … going digital Late 1980s to early 1990s (2nd Generation Digital Systems) • N.America relies on de facto “let the best technology win” standardisation • By contrast Europe decides to rely on standardisation & co-operation – Huge pent-up demand for mobility can not be met by upgrading existing purely analogue systems. Parallel advances in digital techniques and Very Large Scale Integration (VLSI) chipset manufacture suggest a new way forward – However European domestic markets individually too small to achieve the economies of scale necessary for vendors to take the risk of developing such a risky new solution – Enter the European Commission with a political agenda – demonstrate Europe‟s “technology leadership” and ensure European manufacturers can compete globally • New spectrum auctions in USA in early 1990 (PCS 1900) lead to plethora of standards – D-AMPS IS-54 – Motorola sponsored, TDMA IS-136, CDMA IS-95 – Qualcomm sponsored – Plus, limited GSM • Meanwhile in Europe…©2001 - 2005 Erick O’Connor 5
  6. 6. …GSM is born Late 1980s to early 1990s (2nd Generation Digital Systems) • Guided by European Commission & European Telecommunications Standard Institute • 26 European telecommunication administrations establish the Groupe Spéciale Mobile (GSM) in 1982 with aim to develop a new specification for a fully digital pan-European mobile communications network • The Group notes that the “new industry’s economic future will rely on unprecedented levels of pan-European co-operation” • Political decision to force member countries to: – allocate frequencies at 900 MHz in every EC country (later 1800 MHz) – specify the exact technology to be used and; – deploy systems by 1991 • First commercial GSM networks deployed in 1992 – Denmark / Finland / France / Germany / Italy / Portugal / Sweden / United Kingdom©2001 - 2005 Erick O’Connor 6
  7. 7. …beginning of the GSM success story By End of 1993 • One million subscribers using GSM • GSM Association has 70 members, 48 countries • First non-European operator, Telstra of Australia And, by technology.… www.gsmworld.com ….Subscribers©2001 - 2005 Erick O’Connor 7
  8. 8. …the turn of the century & 3rd generation services • Multiple operators per country & worldwide (800+) – intense price based competition – Huge growth in subscribers thanks to pre-paid but falling ARPU & high churn (c.25%) – Market close to saturation – slowing subscriber penetration growth rates (c.85%) • The challenge – what to do in future? • Europe keen to replicate commercial success of GSM but, Americans & Japanese had different views and needs – Japan had run out of spectrum for voice – Americans unhappy at being “dictated to” by a European standard – European vision of always on data & rich value added content services • America & Japan jointly force Europe to open up standardisation process so as not to once again “lock-out” other trading blocs‟ vendors – Creation of 3rd Gen Partnership Programme (3GPP) body – Heated standardisation on Wideband CDMA (Qualcomm vs Ericsson) – Final agreement on Universal Mobile Telecommunications Standard (UMTS) in 1998….©2001 - 2005 Erick O’Connor 8
  9. 9. The market today – key statistics©2001 - 2005 Erick O’Connor 9
  10. 10. GSM designRadio & Network subsystems, Signalling & Transmission
  11. 11. Basic GSM network elements PSTN Network Subsystem ISDN PDN ISC BTS GMSC SIWF BSC XCDR MSC User Data & Authentication EIR BTS BSC AUC HLR VLR AUC Authentication Centre BTS BSC Basestation Controller BTS Basestation Transceiver EIR Equipment Identity Register MS + SIM GMSC Gateway Mobile Switching Centre HLR Home Location Register ISC International Switching Centre Radio Subsystem ISDN MSC Integrated Services Digital Network Mobile Switching Centre PDN Packet Data Network (X25) PSTN Public Switched Telephony Network SIWF Shared Interworking Function VLR Visitor Location Register©2001 - 2005 Erick O’Connor XCDR Transcoder (16 / 64kbps coding) 11
  12. 12. GSM air interface design • Access Techniques – Time Division Multiple Access – Frequency Division Multiple Access – Space Division Multiple Access Multiple cells -400 kHz f0 +400 kHz • Radio characteristics 8 timeslots GMSK Spectrum – Gaussian Minimum Shift Keying (GMSK) f3 – Slow Frequency Hopping f2 Frequency • Logical structure f1 – 8 Timeslots per Carrier f0 – 1 Downlink Timeslot reserved for signalling – 3 timeslot difference between uplink & downlink FDMA & TDMA Time • Frame structure used for synchronisation – 51-frame Multiframe (235.4 ms) 0 1 2 3 4 5 6 7 Downlink – 51 or 26 Multiframe Superframe (6.12 sec) – 2048 Superframe Hyperframe (3 hr 28 mins) Uplink 0 1 2 3 4 5 6 7 Delay©2001 - 2005 Erick O’Connor 12
  13. 13. Radio subsystem (i) • Basestation Transceiver (BTS) provides radio channels for signalling & user data BTS BSC XCDR • A BTS has 1 to 6 RF carriers per sector and 1(omni) to 6 sectors – e.g. 3/3/3 = 3 sector with 3 carriers per sector BTS BSC – 3 x 7 Timeslots x 3 = 63 Timeslots total – c.52 Erlangs @ 2% Grade of Service BTS MS + SIM – c.2,000 users per BTS @ 25 mErl / User (90 seconds) 3 2 1 • Frequency reuse depends on terrain, Frequency reuse & 3 f3 2 f2 frequencies available etc. cluster formation 1 f1 K=3 • Paired spectrum shared by Operators 7 – 900 / 1800 MHz in Europe / Asia (25 & 75 MHz) 6 2 7 1 6 2 – 1900 MHz in N.America 5 3 1 4 5 3 f7 4 • 200 kHz channel separation f6 f2 f1 • 125 Channels @ 900 MHz f5 f3 f4 K=7©2001 - 2005 Erick O’Connor 13
  14. 14. Radio subsystem (ii) BTS BSC XCDR • Basestation Controller (BSC) controls a number of BTS – Acts as a small switch BTS – Assists in handover between cells and between BTS BSC – Manages the Radio Resource, allocating channels on the air interface BTS MS + SIM • Transcoding (XCDR) function is logically associated with BTS – But, typically located at BSC to save on transmission costs – XCDR provides 13 kbps Coding / Decoding between GSM Codec & standard 64 kbps A-law encoded voice • Interfaces – “Abis” – BTS to BSC interface (never fully standardised so vendor-specific variants exist) – “A” – BSC to MSC interface carrying voice, BSC signalling and Radio – Traffic Channels are mapped one-to-one between BTS and Transcoder – BTS can be connected in “Star” or “Daisy-chain” arrangement to BSC (max. 15)©2001 - 2005 Erick O’Connor 14
  15. 15. Network subsystem (i) PSTN ISDN PDN ISC • Core component is Mobile Switching Centre (MSC) GMSC SIWF – Performs all switching functions of a fixed-network switch MSC – Allocates and administers radio resources & controls mobility of users – Multiple BSC hosted by one MSC • Gateway MSC (GMSC) provide interworking with other fixed & mobile networks – Crucial role in delivering in-coming call to mobile user in association with Home Location Register (HLR) interrogation • Shared Interworking Function (SIWF) – Bearer Services are defined in GSM including 3.1 kHz Voice, ISDN, 9.6 kbps Data & 14.4 kbps – IWF provides “modem” capabilities to convert between digital bearer & PSTN, ISDN & PDN • International Switching Centre (ISC) – Provides switching of calls internationally. Switch may be provided by another carrier©2001 - 2005 Erick O’Connor 15
  16. 16. Network subsystem (ii) • Home Location Register (HLR) holds EIR AUC HLR master database of all subscribers VLR – Stores all permanent subscriber data & relevant temporary data including: • Authentication Centre (AUC) & Equipment Identity Register (EIR) • MS-ISDN (Mobile Subscriber‟s telephone no.) • MSRN (Mobile Station Roaming no.) – GSM is inherently secure using encryption over the air-interface and for • Current Mobile Location Area authentication / registration – Actively involved in incoming call set-up & – AUC holds each subscriber‟s secret key supplementary services (Ki) & calculates “triplet” for challenge / respond authentication with mobile • Visitor Location Register (VLR) – SIM is sent data and must calculate associated with individual MSCs appropriate response – VLR stores temporary subscriber information – EIR is used to store mobile terminals obtained from HLR of mobiles currently serial numbers registered in serving area of MSC – Involved in registration of mobiles – Assists in delivery of supplementary service features such as Call Waiting / Call Hold©2001 - 2005 Erick O’Connor 16
  17. 17. GSM call setup & Signalling
  18. 18. Signalling – Air interface Air Interface Signalling • Uplink signalling (from MS) more complicated • Downlink signalling (to Mobile Station) – Random Access Channel (RACH) – – Relies on Bearer Control Channel competitive multi-access mode using (BCCH) set at fixed frequency per cell slotted ALOHA to request dedicated signalling channel (SDCCH) • Mobile Stations use this to lock-on to network • Bidirectional channels include • Mobile Stations periodically scan – Traffic Channels (TCH) – Carrying full environment and report back other rate voice @ 13 kbps / half-rate voice BCCH power levels to BSC to assist in handover – Standalone Dedicated Control Channel (SDCCH) – used for updating location – Access Grant Channel (AGCH) – used information or parts of connection set-up to assign a Control or Traffic Channel to the mobile – Slow Associated Control Channel (SACCH) – used to report radio conditions – Paging Channel (PCH) – paging to find & measurement reports specific mobiles – Fast Associated Control Channel (FACCH) – uses “stolen” traffic channel capacity to add extra signalling capacity©2001 - 2005 Erick O’Connor 18
  19. 19. Signalling – Mobile Application Part interfaces Network Signalling GSM Specific Signalling Interfaces (Mobile Application Part) Um Air interface signalling MSC Abis Radio management A BSS management, connection EIR control & mobility management MSC B Subscriber data, location F E information, supplementary service settings BSC C C Routing information requests A HLR D Exchange of location-dependent B D subscriber data & subscriber BTS Abis management VLR E Inter-MSC handover signalling G F Subscriber & equipment identity BTS VLR check G Inter-MSC handover, transfer of Um subscriber data MS + SIM©2001 - 2005 Erick O’Connor 19
  20. 20. ITU-T Common Channel Signalling System Number 7 A Application Parts Actually carry the specific GSM interfaces B, C, D, E & G messages for Mobile (MAP), Standard Telephone carried as Mobile Application Part Intelligent Network (INAP) or User Part (TUP) Operations & Maintenance Most basic CSS7 signalling (OMAP) MAP INAP OMAP Transaction Control Application Part – component responsible for TCAP ISO Layers 1 thro 7 “carrying” higher level ISUP Application Parts to their TUP correct destinations SCCP Signalling Connection ISDN User Part Control Part Add functionality to Functionally equivalent to TCP permit ISDN signalling layer, carries “Connectionless” (i.e. fully digital) messages between Network elements MTP Layers 1/2/3 between networks Signalling 101 • Line signalling – “tell the other end you want to make call” Message Transfer Part Lowest level, permits • Register signalling – “tell the other end the destination of the call” interconnection with underlying physical transmission medium©2001 - 2005 Erick O’Connor 20
  21. 21. PDH transmission …composition of 32 channel E1 bearer TS 0 Synchronisation Header TS16 Signalling ITU-T G.703 E1 link 2048 kbps 32 x 64 kbps Timeslots 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Plesiochronous Digital Hierarchy (PDH) 140 Mbps 34 Mbps Voice / Data Timeslot 2 Mbps Abis - Voice GSM Codec 4 x 13 kbps Timeslots Synchronous Digital Hierarchy (SDH) STM-16 (SONET - USA) STM-4 STM-1©2001 - 2005 Erick O’Connor 21
  22. 22. Circuit-switched network architecture (Transmission & Signalling planes)BSS Basestation SubsystemCCS7 Common Channel Signalling #7CO Central Office CSS7 Signalling PlaneHLR Home Location Register SSPMSC Mobile Switching Centre HLRSDH Synchronous Digital Hierarchy CCS7 LinksSSP Service Switching PointSTP Signalling Transfer Point CO Switch STP MSC SDH Fibre Optic Network Synchronisation Drop & Insert Other Networks Multiplexers BSS Transmission Plane©2001 - 2005 Erick O’Connor 22
  23. 23. Call setup Data held in HLR: Call is placed to a mobile subscriber by dialling the mobile 1 number (MS-ISDN). • Subscriber & Subscription Data – International Mobile Subscriber Identity (IMSI) – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions PSTN – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR – Authentication data MSC • Tracking & Routing Information – Mobile Station Roaming Number (MSRN) BTS BSC HLR – Temporary Mobile Subscriber VLR Identity (TMSI) BTS – Current VLR address MS + SIM – Current MSC address – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 23
  24. 24. Call setup Data held in HLR: Using the MS-ISDN the MSC interrogates the HLR to find status 2 and location of mobile subscriber. • Subscriber & Subscription Data – International Mobile Subscriber Identity (IMSI) – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions PSTN – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR – Authentication data 2 MS-ISDN MSC • Tracking & Routing Information – Mobile Station Roaming Number (MSRN) BTS BSC HLR – Temporary Mobile Subscriber VLR Identity (TMSI) BTS – Current VLR address MS + SIM – Current MSC address – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 24
  25. 25. Call setup Data held in HLR: The HLR returns the MSRN – a “virtual” number telling the 3 GMSC how to route the call to the serving MSC. • Subscriber & Subscription Data – International Mobile Subscriber Identity (IMSI) – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions PSTN – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR – Authentication data 3 MSRN 2 MS-ISDN MSC • Tracking & Routing Information – Mobile Station Roaming Number (MSRN) BTS BSC HLR – Temporary Mobile Subscriber VLR Identity (TMSI) BTS – Current VLR address MS + SIM – Current MSC address – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 25
  26. 26. Call setup Data held in HLR: Using the MSRN the GMSC routes the call to the serving MSC. 4 • Subscriber & Subscription Data – International Mobile Subscriber Identity (IMSI) – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions MSRN PSTN 4 – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR – Authentication data 3 MSRN 2 MS-ISDN MSC • Tracking & Routing Information – Mobile Station Roaming Number (MSRN) BTS BSC HLR – Temporary Mobile Subscriber VLR Identity (TMSI) BTS – Current VLR address MS + SIM – Current MSC address – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 26
  27. 27. Call setup Data held in HLR: When Using the MS-ISDN the MSC interrogates the queries findVLR to MSC receives the incoming call it HLR to its status 5 obtain the TMSI for the subscriber. and location of mobile subscriber. • Subscriber & Subscription Data – International Mobile Subscriber Identity (IMSI) – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions MSRN PSTN 4 – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR – Authentication data 3 MSRN 2 MS-ISDN MSC • Tracking & Routing Information – Mobile Station Roaming Number (MSRN) BTS BSC 5 MSRN HLR – Temporary Mobile Subscriber VLR Identity (TMSI) BTS – Current VLR address MS + SIM – Current MSC address – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 27
  28. 28. Call setup Data held in HLR: The TMSI is assigned at registration and is another “virtual” 6 number used for security purposes. Together with cell ID • Subscriber & Subscription Data location information stored in the VLR the MSC now has – International Mobile Subscriber Identity (IMSI) sufficient information to be able to route the call. – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions MSRN PSTN 4 – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR – Authentication data 3 MSRN 2 MS-ISDN MSC • Tracking & Routing Information – Mobile Station Roaming Number (MSRN) BTS BSC 5 MSRN HLR – Temporary Mobile Subscriber VLR Identity (TMSI) 6 BTS TMSI – Current VLR address MS + SIM – Current MSC address – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 28
  29. 29. Call setup Data held in HLR: The MSC directs the BSC to page the subscriber and inform the 7 handset of an incoming call. • Subscriber & Subscription Data – International Mobile Subscriber Identity (IMSI) – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions MSRN PSTN 4 – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR 7 – Authentication data 3 MSRN 2 MS-ISDN MSC • Tracking & Routing Information 7 – Mobile Station Roaming Number (MSRN) BTS BSC 5 MSRN HLR – Temporary Mobile Subscriber 7 TMSI VLR Identity (TMSI) 6 BTS TMSI – Current VLR address MS + SIM – Current MSC address – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 29
  30. 30. Call setup Data held in HLR: The handset acknowledges the incoming call and the call is 8 established between the two parties. The handset may also • Subscriber & Subscription Data signal the BSC / MSC during the call to set up supplementary – International Mobile Subscriber Identity (IMSI) services such as Call Hold, 3-way calling etc. – Mobile Station ISDN (MS-ISDN) – Bearer & teleservice subscriptions MS-ISDN 1 – Service restrictions MSRN PSTN 4 – Parameters for additional services – Information on subscriber BTS equipment GMSC BSC XCDR 7 – Authentication data 3 MSRN 2 MS-ISDN MSC • Tracking & Routing Information 7 – Mobile Station Roaming Number (MSRN) BTS BSC 5 MSRN HLR – Temporary Mobile Subscriber 7 TMSI VLR Identity (TMSI) 6 BTS TMSI – Current VLR address MS + SIM 8 – Current MSC address TMSI – Local Mobile Subscriber Identity Principle of routing call to mobile subscribers©2001 - 2005 Erick O’Connor 30
  31. 31. GPRS Design
  32. 32. GPRS network elements Other GPRS SM-SC PLMN BTS GGSN BSC PCU BG SGSN PDN GGSN BTS BSC BG Border Gateway BSC Basestation Controller VLR HLR BTS Basestation Transceiver BTS GGSN Gateway GPRS Support Node HLR Home Location Register GPRS MS + SIM PCU Packet Control Unit PDN Packet Data Network (X25) PLMN Public Land Mobile Network SM-SC Short Message Service Centre SGSN Serving GPRS Support Node VLR Visitor Location Register©2001 - 2005 Erick O’Connor 32
  33. 33. How GSM & GPRS co-exist DHCP Radius X.25 / IP / PDN PSTN Internet Firewall DNS De facto interfaces G.703 E1 64kbps Gi (IP) SMSC OSS CG GMSC IWF GGSN MAP C LIAN MAP E Gn (IP) DNS HLR VLR MAP D MAP Gr MAP Ga SMSC SGSN GSM XCDR GPRS A (G.703 E1 16kbps) BSC Basestation Controller BTS Basestation Transceiver BSC PCU CCS7 Common Channel Signalling #7 Gb (Frame Relay) CG Charging Gateway DHCP Dynamic Host Configuration Protocol DNS Domain Name Server BTS GSN GPRS Serving Node (Serving / Gateway) Abis (G.703 E1) HLR Home Location Register Cells IWF Interworking Function (Circuit / Packet) LIAN Legal Intercept Attendance Node MAP Mobile Application Part (CCS7) Voice or Data link MSC Mobile Switching Centre (Serving / Gateway) OSS Operational Support System Signalling & Name of Interface PCU Packet Control Unit PSTN Public Switched Telephony Network VLR Visitor Location Register©2001 - 2005 Erick O’Connor XCDR Transcoder (16 / 64kbps coding) 33
  34. 34. GPRS key information • Four Coding Schemes defined • GSM offsets uplink timeslots (Ts) from – CS1 9.05 kbit / second per timeslot downlink by 3 to save on radio transmit / receive hardware – CS2 13.40 – Therefore today‟s handsets are typically: – CS3 15.60 • 1 Ts downlink – CS4 21.40 • 2 to 3 Ts uplink – Higher speed = Trade off of Forward Error Correction & hence quality • Class B • CS1 & CS2 capable • Three Handset Types defined • Equals 3 x 13.40 = 40.20 kbit/s maximum – Class A – simultaneous voice & data – Class B – voice or data only at one time – Handsets can exceed this limit – Class C – data only • But cost more… • Use more power etc, GPRS 0 1 2 3 4 5 6 7 8 Downlink Signalling Uplink GPRS©2001 - 2005 Erick O’Connor 34
  35. 35. Protocol layers in GPRS Application Protocol (http / ftp) TCP Transmission Control Protocol (TCP) TCP TCP IP IP IP IP SNDCP SNDCP GTP GTP LLC LLC UDP / UDP / TCP TCP RLC RLC BSSGP BSSGP IP IP Network Network MAC MAC L2 L2 Service Service GSM GSM RF L1 bis L1 Bis L1 L1 RF Laptop GPRS MS BSS SGSN GGSN / PDA BSSGP Basestation System GPRS Protocol GSM RF Radio Frequency GTP Gateway Tunnelling Protocol LLC Logical Link Control MAC Medium Access Control RLC Radio Link Control SNDCP Subnetwork Dependent Convergence Protocol©2001 - 2005 Erick O’Connor 35
  36. 36. Mobility management • Mobility management • Packet Data Protocol (PDP) Contexts – Attach – Every mobile must have an address for each • Know who is the MS PDP Context in use • Know what the user is allowed to do – Addresses are statically or dynamically assigned – Detach – Context information includes: • Leave the system • PDP Type – Location updates • PDP address (optional) • Know location of MS • Quality of Service (5 classes – Service Precedence / Reliability / Delay / • Route mobile terminated (MT) packets to MS Throughput Maximum & Mean) – SGSN has main control of QoS • GPRS Service Descriptions – Point-to-Point • Connection-orientated (X25) • Connection-less (IPv4 / IPv6) – Point-to-Multipoint (Release 2) • Multicast • Groupcast – Short Message Service (SMS)©2001 - 2005 Erick O’Connor 36
  37. 37. GPRS dimensioning • 900MHz UK Network • Dimensioning – 7 Timeslots per Carrier – 8 million subscribers – 1 to 6 RF carriers / cell – 10% GPRS handset penetration – 1 to 3 cells / BTS – 800,000 users – 5,000 BTS – 10:1 Activity factor – 250 BSC – 10:1 x 800,000 = 80,000 simultaneous users – 50 MSC – 8 SGSN / 2 GGSN – 10 GMSC • Exact dimensioning depends on: • GPRS – Number of users – SGSN c.10,000 simultaneous users – Geography – GGSN c.45,000 simultaneous users – Population density – 10 to 1 contention ratio – Data profile & activity – GPRS growth©2001 - 2005 Erick O’Connor 37
  38. 38. Evolution towards UMTS – All IP core Internet Packet Data GSM & GPRS PSTN Packet Gateway HLR CAMEL Circuit All IP Packet Gateway Network Call Control Server BTS RNC Server BTS BSC UMTS BTS Node B 3rd Generation UMTS©2001 - 2005 Erick O’Connor 38
  39. 39. Further Reading • „GSM Switching, Services and Protocols‟ – Jörg Eberspöcher & Hans-Jörg Vögel, John Wiley & Sons, 2000 • „GPRS General Packet Radio Service‟ – Regis J. “Bud” Bates, McGraw-Hill Telecom Professional, 2002 • „GPRS Networks‟ – Geoff Sanders, Lionel Thorens, Manfred Reisky, Oliver Rulik, Stefan Deylitz, John Wiley & Sons, 2003©2001 - 2005 Erick O’Connor 39

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