Mobile Communications
                 Chapter 4: Wireless
             Telecommunication Systems
                        ...
Mobile phone subscribers worldwide                                        approx. 1.7 bn

                    1600


     ...
GSM: Overview

GSM
       q   formerly: Groupe Spéciale Mobile (founded 1982)
       q   now: Global System for Mobile Com...
Performance characteristics of GSM (wrt. analog sys.)
     Communication
           q   mobile, wireless communication; vo...
Disadvantages of GSM

There is no perfect system!!
q no end-to-end encryption of user data
q no full ISDN bandwidth of 64 ...
GSM: Mobile Services

GSM offers
      q   several types of connections
            l   voice connections, data connection...
Bearer Services

q   Telecommunication services to transfer data between access points
q   Specification of services up to...
Tele Services I

     q   Telecommunication services that enable voice communication
         via mobile phones
     q   A...
Tele Services II

     Additional services
           q   Non-Voice-Teleservices
                 l group 3 fax
          ...
Supplementary services

     q   Services in addition to the basic services, cannot be offered
         stand-alone
     q...
Architecture of the GSM system

GSM is a PLMN (Public Land Mobile Network)
      q   several providers setup mobile networ...
Ingredients 1: Mobile Phones, PDAs & Co.




                                                                  The visible...
Ingredients 2: Antennas




                            Still visible – cause many discussions…
Prof. Dr.-Ing. Jochen Schi...
Ingredients 3: Infrastructure 1

                                                   Base Stations




                    ...
Ingredients 3: Infrastructure 2

                                                                Not „visible“, but
      ...
GSM: overview
               OMC, EIR,
                 AUC
                                   HLR
                       ...
GSM: elements and interfaces


                                             radio cell
                                   ...
System architecture: radio subsystem
         radio                   network and switching
         subsystem            ...
Radio subsystem

The Radio Subsystem (RSS) comprises the cellular mobile network up to
  the switching centers
q Component...
GSM: cellular network

       segmentation of the area into cells

                                                       ...
GSM frequency bands

      Type                     Channels                  Uplink [MHz]        Downlink [MHz]

      GS...
Example coverage of GSM networks (www.gsmworld.com)

T-Mobile (GSM-900/1800) Germany                             O2 (GSM-1...
Base Transceiver Station and Base Station Controller

     Tasks of a BSS are distributed over BSC and BTS
     q BTS comp...
GSM - TDMA/FDMA

                                                         935-960 MHz
                                    ...
GSM protocol layers for signaling


                      Um                          Abis                         A
     ...
4 types of handover


                     1
                                          2               3           4

    ...
Handover decision



                  receive level                                         receive level
               ...
Handover procedure


     MS         BTSold       BSCold                        MSC               BSCnew            BTSnew...
Security in GSM

  Security services
        q   access control/authentication
              l user ó SIM (Subscriber Iden...
Data services in GSM II
     GSM Data transmission standardized with only 9.6 kbit/s
           q   advanced coding allows...
Example 3G Networks: Japan




  FOMA (Freedom Of Mobile multimedia
  Access) in Japan
                                   ...
Example 3G networks: Australia




    cdma2000 1xEV-DO in Melbourne/Australia



                                        ...
Isle of Man – Start of UMTS in Europe as Test




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   MC SS05 ...
UMTS in Monaco




Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/   MC SS05   4.34
UMTS in Europe




                                                 Orange/UK


     Vodafone/Germany




Prof. Dr.-Ing. J...
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Mobile Communications Chapter 4: Wireless Telecommunication ...

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Mobile Communications Chapter 4: Wireless Telecommunication ...

  1. 1. Mobile Communications Chapter 4: Wireless Telecommunication Systems slides by Jochen Schiller with modifications by Emmanuel Agu q Market q GSM q Overview q Services q Sub-systems q Components Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.1
  2. 2. Mobile phone subscribers worldwide approx. 1.7 bn 1600 1400 1200 Subscribers [million] GSM total 1000 TDMA total CDMA total 800 PDC total Analogue total W-CDMA 600 Total wireless Prediction (1998) 400 200 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 year Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.2
  3. 3. GSM: Overview GSM q formerly: Groupe Spéciale Mobile (founded 1982) q now: Global System for Mobile Communication q Pan-European standard (ETSI, European Telecommunications Standardisation Institute) q simultaneous introduction of essential services in three phases (1991, 1994, 1996) by the European telecommunication administrations (Germany: D1 and D2) è seamless roaming within Europe possible q today many providers all over the world use GSM (more than 200 countries in Asia, Africa, Europe, Australia, America) q more than 1.2 billion subscribers in more than 630 networks q more than 75% of all digital mobile phones use GSM (74% total) q over 200 million SMS per month in Germany, > 550 billion/year worldwide (> 10% of the revenues for many operators) [be aware: these are only rough numbers…] Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.3
  4. 4. Performance characteristics of GSM (wrt. analog sys.) Communication q mobile, wireless communication; voice and data services Total mobility q international access, chip-card enables use of access points of different providers Worldwide connectivity q one number, the network handles localization High capacity q better frequency efficiency, smaller cells, more customers per cell High transmission quality q high audio quality and reliability for wireless, uninterrupted phone calls at higher speeds (e.g., from cars, trains) Security functions q access control, authentication via chip-card and PIN Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.4
  5. 5. Disadvantages of GSM There is no perfect system!! q no end-to-end encryption of user data q no full ISDN bandwidth of 64 kbit/s to the user, no transparent B- channel q reduced concentration while driving q electromagnetic radiation q abuse of private data possible q roaming profiles accessible q high complexity of the system q several incompatibilities within the GSM standards Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.5
  6. 6. GSM: Mobile Services GSM offers q several types of connections l voice connections, data connections, short message service q multi-service options (combination of basic services) Three service domains q Bearer Services q Telematic Services q Supplementary Services bearer services MS transit source/ TE MT GSM-PLMN network destination TE R, S Um (PSTN, ISDN) network (U, S, R) tele services Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.6
  7. 7. Bearer Services q Telecommunication services to transfer data between access points q Specification of services up to the terminal interface (OSI layers 1-3) q Different data rates for voice and data (original standard) q data service (circuit switched) l synchronous: 2.4, 4.8 or 9.6 kbit/s l asynchronous: 300 - 1200 bit/s q data service (packet switched) l synchronous: 2.4, 4.8 or 9.6 kbit/s l asynchronous: 300 - 9600 bit/s Today: data rates of approx. 50 kbit/s possible – will be covered later! Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.7
  8. 8. Tele Services I q Telecommunication services that enable voice communication via mobile phones q All these basic services have to obey cellular functions, security measurements etc. q Offered services q mobile telephony primary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz q Emergency number common number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible) q Multinumbering several ISDN phone numbers per user possible Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.8
  9. 9. Tele Services II Additional services q Non-Voice-Teleservices l group 3 fax l voice mailbox (implemented in the fixed network supporting the mobile terminals) l electronic mail (MHS, Message Handling System, implemented in the fixed network) l ... l Short Message Service (SMS) alphanumeric data transmission to/from the mobile terminal (160 characters) using the signaling channel, thus allowing simultaneous use of basic services and SMS (almost ignored in the beginning now the most successful add-on!) Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.9
  10. 10. Supplementary services q Services in addition to the basic services, cannot be offered stand-alone q Similar to ISDN services besides lower bandwidth due to the radio link q May differ between different service providers, countries and protocol versions q Important services q identification: forwarding of caller number q suppression of number forwarding q automatic call-back q conferencing with up to 7 participants q locking of the mobile terminal (incoming or outgoing calls) q ... Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.10
  11. 11. Architecture of the GSM system GSM is a PLMN (Public Land Mobile Network) q several providers setup mobile networks following the GSM standard within each country q components l MS (mobile station) l BS (base station) l MSC (mobile switching center) l LR (location register) q subsystems l RSS (radio subsystem): covers all radio aspects l NSS (network and switching subsystem): call forwarding, handover, switching l OSS (operation subsystem): management of the network Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.11
  12. 12. Ingredients 1: Mobile Phones, PDAs & Co. The visible but smallest part of the network! Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.12
  13. 13. Ingredients 2: Antennas Still visible – cause many discussions… Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.13
  14. 14. Ingredients 3: Infrastructure 1 Base Stations Cabling Microwave links Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.14
  15. 15. Ingredients 3: Infrastructure 2 Not „visible“, but comprise the major part of the network (also from an investment point of view…) Management Data bases Switching units Monitoring Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.15
  16. 16. GSM: overview OMC, EIR, AUC HLR GMSC NSS fixed network with OSS VLR MSC MSC VLR BSC BSC RSS Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.16
  17. 17. GSM: elements and interfaces radio cell BSS MS MS Um radio cell RSS BTS MS BTS Abis BSC BSC A MSC MSC NSS signaling VLR VLR ISDN, PSTN HLR GMSC PDN IWF O OSS EIR AUC OMC Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.17
  18. 18. System architecture: radio subsystem radio network and switching subsystem subsystem MS MS Components q MS (Mobile Station) Um q BSS (Base Station Subsystem): BTS Abis consisting of BSC MSC l BTS (Base Transceiver Station): BTS sender and receiver l BSC (Base Station Controller): controlling several transceivers Interfaces q Um : radio interface A BTS q Abis : standardized, open interface with MSC BSC 16 kbit/s user channels BTS q A: standardized, open interface with BSS 64 kbit/s user channels Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.18
  19. 19. Radio subsystem The Radio Subsystem (RSS) comprises the cellular mobile network up to the switching centers q Components q Base Station Subsystem (BSS): l Base Transceiver Station (BTS): radio components including sender, receiver, antenna - if directed antennas are used one BTS can cover several cells l Base Station Controller (BSC): switching between BTSs, controlling BTSs, managing of network resources, mapping of radio channels (Um) onto terrestrial channels (A interface) l BSS = BSC + sum(BTS) + interconnection q Mobile Stations (MS) Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.19
  20. 20. GSM: cellular network segmentation of the area into cells possible radio coverage of the cell idealized shape of the cell cell q use of several carrier frequencies q not the same frequency in adjoining cells q cell sizes vary from some 100 m up to 35 km depending on user density, geography, transceiver power etc. q hexagonal shape of cells is idealized (cells overlap, shapes depend on geography) q if a mobile user changes cells ê handover of the connection to the neighbor cell Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.20
  21. 21. GSM frequency bands Type Channels Uplink [MHz] Downlink [MHz] GSM 850 128-251 824-849 869-894 (Americas) GSM 900 0-124, 955-1023 876-915 921-960 classical 124 channels 890-915 935-960 extended +49 channels 880-915 925-960 GSM 1800 512-885 1710-1785 1805-1880 GSM 1900 512-810 1850-1910 1930-1990 (Americas) GSM-R 955-1024, 0-124 876-915 921-960 exclusive 69 channels 876-880 921-925 - Additionally: GSM 400 (also named GSM 450 or GSM 480 at 450-458/460-468 or 479-486/489-496 MHz - Please note: frequency ranges may vary depending on the country! - Channels at the lower/upper edge of a frequency band are typically not used Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.21
  22. 22. Example coverage of GSM networks (www.gsmworld.com) T-Mobile (GSM-900/1800) Germany O2 (GSM-1800) Germany AT&T (GSM-850/1900) USA Vodacom (GSM-900) South Africa Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.22
  23. 23. Base Transceiver Station and Base Station Controller Tasks of a BSS are distributed over BSC and BTS q BTS comprises radio specific functions q BSC is the switching center for radio channels Functions BTS BSC Management of radio channels X Frequency hopping (FH) X X Management of terrestrial channels X Mapping of terrestrial onto radio channels X Channel coding and decoding X Rate adaptation X Encryption and decryption X X Paging X X Uplink signal measurements X Traffic measurement X Authentication X Location registry, location update X Handover management X Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.23
  24. 24. GSM - TDMA/FDMA 935-960 MHz 124 channels (200 kHz) downlink cy en 890-915 MHz qu fre 124 channels (200 kHz) uplink higher GSM frame structures time GSM TDMA frame 1 2 3 4 5 6 7 8 4.615 ms GSM time-slot (normal burst) guard guard space tail user data S Training S user data tail space 3 bits 57 bits 1 26 bits 1 57 bits 3 546.5 µs 577 µs Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.24
  25. 25. GSM protocol layers for signaling Um Abis A MS BTS BSC MSC CM CM MM MM BSSAP BSSAP RR RR’ RR’ BTSM BTSM SS7 SS7 LAPDm LAPDm LAPD LAPD radio radio PCM PCM PCM PCM 16/64 kbit/s 64 kbit/s / 2.048 Mbit/s Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.25
  26. 26. 4 types of handover 1 2 3 4 MS MS MS MS BTS BTS BTS BTS BSC BSC BSC MSC MSC Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.26
  27. 27. Handover decision receive level receive level BTSold BTSold HO_MARGIN MS MS BTSold BTSnew Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.27
  28. 28. Handover procedure MS BTSold BSCold MSC BSCnew BTSnew measurement measurement report result HO decision HO required HO request resource allocation ch. activation HO command HO request ack ch. activation ack HO command HO command HO access Link establishment HO complete HO complete clear command clear command clear complete clear complete Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.28
  29. 29. Security in GSM Security services q access control/authentication l user ó SIM (Subscriber Identity Module): secret PIN (personal identification number) l SIM ó network: challenge response method q confidentiality l voice and signaling encrypted on the wireless link (after successful authentication) q anonymity “secret”: l temporary identity TMSI • A3 and A8 (Temporary Mobile Subscriber Identity) available via the l newly assigned at each new location update (LUP) Internet • network providers l encrypted transmission can use stronger 3 algorithms specified in GSM mechanisms q A3 for authentication (“secret”, open interface) q A5 for encryption (standardized) q A8 for key generation (“secret”, open interface) Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.29
  30. 30. Data services in GSM II GSM Data transmission standardized with only 9.6 kbit/s q advanced coding allows 14,4 kbit/s q not enough for Internet and multimedia applications GPRS (General Packet Radio Service) q packet switching q using free slots only if data packets ready to send (e.g., 50 kbit/s using 4 slots temporarily) q standardization 1998, introduction 2001 q advantage: one step towards UMTS, more flexible q disadvantage: more investment needed (new hardware) Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.30
  31. 31. Example 3G Networks: Japan FOMA (Freedom Of Mobile multimedia Access) in Japan Examples for FOMA phones Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.31
  32. 32. Example 3G networks: Australia cdma2000 1xEV-DO in Melbourne/Australia Examples for 1xEV-DO devices Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.32
  33. 33. Isle of Man – Start of UMTS in Europe as Test Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.33
  34. 34. UMTS in Monaco Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.34
  35. 35. UMTS in Europe Orange/UK Vodafone/Germany Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS05 4.35

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