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Mobile Communications

Mobile Communications. Introduction Use-cases, applications Definition of terms Challenges, history Wireless Transmission Frequencies & regulations Signals, antennas, signal propagation Multiplexing, modulation, spread spectrum, cellular system Medium Access SDMA, FDMA, TDMA, CDMA

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Mobile Communications

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  1. Mobile Communications

  2. Introduction Use-cases, applications Definition of terms Challenges, history Wireless Transmission Frequencies & regulations Signals, antennas, signal propagation Multiplexing, modulation, spread spectrum, cellular system Medium Access SDMA, FDMA, TDMA, CDMA CSMA/CA, versions of Aloha Collision avoidance, polling Wireless Telecommunication Systems GSM, HSCSD, GPRS, DECT, TETRA, UMTS, IMT-2000 Satellite Systems GEO, LEO, MEO, routing, handover Broadcast Systems DAB, DVB Wireless LANs Basic Technology IEEE 802.11a/b/g/…, .15, Bluetooth, ZigBee Network Protocols Mobile IP Ad-hoc networking Routing Transport Protocols Reliable transmission Flow control Quality of Service Support for Mobility File systems, WWW, WAP, i-mode, J2ME, ... Outlook Overview

  3. Mobile CommunicationsChapter 1: Introduction A case for mobility – many aspects History of mobile communication Market Areas of research

  4. Computers for the next decades? • Computers are integrated • small, cheap, portable, replaceable - no more separate devices • Technology is in the background • computer are aware of their environment and adapt (“location awareness”) • computer recognize the location of the user and react appropriately (e.g., call forwarding, fax forwarding, “context awareness”)) • Advances in technology • more computing power in smaller devices • flat, lightweight displays with low power consumption • new user interfaces due to small dimensions • more bandwidth per cubic meter • multiple wireless interfaces: wireless LANs, wireless WANs, regional wireless telecommunication networks etc. („overlay networks“)

  5. Mobile communication • Two aspects of mobility: • user mobility: users communicate (wireless) “anytime, anywhere, with anyone” • device portability: devices can be connected anytime, anywhere to the network • Wireless vs. mobile Examples  stationary computer  notebook in a hotel   wireless LANs in historic buildings   Personal Digital Assistant (PDA) • The demand for mobile communication creates the need for integration of wireless networks into existing fixed networks: • local area networks: standardization of IEEE 802.11 • Internet: Mobile IP extension of the internet protocol IP • wide area networks: e.g., internetworking of GSM and ISDN, VoIP over WLAN and POTS(Plain old telephone service)

  6. Applications I • Vehicles • transmission of news, road condition, weather, music via DAB/DVB-T • personal communication using GSM/UMTS • position via GPS • local ad-hoc network with vehicles close-by to prevent accidents, guidance system, redundancy • vehicle data (e.g., from busses, high-speed trains) can be transmitted in advance for maintenance • Emergencies • early transmission of patient data to the hospital, current status, first diagnosis • replacement of a fixed infrastructure in case of earthquakes, hurricanes, fire etc. • crisis, war, ...

  7. Typical application: road traffic UMTS, WLAN, DAB, DVB, GSM, cdma2000, TETRA, ... ad hoc Personal Travel Assistant, PDA, Laptop, GSM, UMTS, WLAN, Bluetooth, ...

  8. Mobile and wireless services – Always Best Connected UMTS, GSM 115 kbit/s LAN 100 Mbit/s, WLAN 54 Mbit/s GSM/GPRS 53 kbit/s Bluetooth 500 kbit/s DSL/ WLAN 3 Mbit/s UMTS 2 Mbit/s GSM/EDGE 384 kbit/s, DSL/WLAN 3 Mbit/s UMTS, GSM 384 kbit/s GSM 115 kbit/s, WLAN 11 Mbit/s

  9. Applications II • Traveling salesmen • direct access to customer files stored in a central location • consistent databases for all agents • mobile office • Replacement of fixed networks • remote sensors, e.g., weather, earth activities • flexibility for trade shows • LANs in historic buildings • Entertainment, education, ... • outdoor Internet access • intelligent travel guide with up-to-datelocation dependent information • ad-hoc networks formulti user games History Info

  10. Location dependent services • Location aware services • what services, e.g., printer, fax, phone, server etc. exist in the local environment • Follow-on services • automatic call-forwarding, transmission of the actual workspace to the current location • Information services • “push”: e.g., current special offers in the supermarket • “pull”: e.g., where is the Black Forrest Cheese Cake? • Support services • caches, intermediate results, state information etc. “follow” the mobile device through the fixed network • Privacy • who should gain knowledge about the location

  11. Mobile devices • Laptop/Notebook • fully functional • standard applications • PDA • graphical displays • character recognition • simplified WWW • Pager • receive only • tiny displays • simple text messages Sensors, embedded controllers • Smartphone • tiny keyboard • simple versions of standard applications • Mobile phones • voice, data • simple graphical displays www.scatterweb.net performance No clear separation between device types possible (e.g. smart phones, embedded PCs, …)

  12. Effects of device portability • Power consumption • limited computing power, low quality displays, small disks due to limited battery capacity • CPU: power consumption ~ CV2f • C: internal capacity, reduced by integration • V: supply voltage, can be reduced to a certain limit • f: clock frequency, can be reduced temporally • Loss of data • higher probability, has to be included in advance into the design (e.g., defects, theft) • Limited user interfaces • compromise between size of fingers and portability • integration of character/voice recognition, abstract symbols • Limited memory • limited usage of mass memories with moving parts • flash-memory or ? as alternative

  13. Wireless networks in comparison to fixed networks • Higher loss-rates due to interference • emissions of, e.g., engines, lightning • Restrictive regulations of frequencies • frequencies have to be coordinated, useful frequencies are almost all occupied • Low transmission rates • local some Mbit/s, regional currently, e.g., 53kbit/s with GSM/GPRS or about 150 kbit/s using EDGE • Higher delays, higher jitter • connection setup time with GSM in the second range, several hundred milliseconds for other wireless systems • Lower security, simpler active attacking • radio interface accessible for everyone, base station can be simulated, thus attracting calls from mobile phones • Always shared medium • secure access mechanisms important

  14. Early history of wireless communication • Many people in history used light for communication • heliographs, flags (“semaphore”), ... • 150 BC smoke signals for communication;(Polybius, Greece) • 1794, optical telegraph, Claude Chappe • Here electromagnetic waves are of special importance: • 1831 Faraday demonstrates electromagnetic induction • J. Maxwell (1831-79): theory of electromagnetic Fields, wave equations (1864) • H. Hertz (1857-94): demonstrateswith an experiment the wave character of electrical transmission through space(1888, in Karlsruhe, Germany)

  15. History of wireless communication I • 1896 Guglielmo Marconi • first demonstration of wireless telegraphy (digital!) • long wave transmission, high transmission power necessary (> 200kw) • 1907 Commercial transatlantic connections • huge base stations (30 100m high antennas) • 1915 Wireless voice transmission New York - San Francisco • 1920 Discovery of short waves by Marconi • reflection at the ionosphere • smaller sender and receiver, possible due to the invention of the vacuum tube (1906, Lee DeForest and Robert von Lieben) • 1926 Train-phone on the line Hamburg - Berlin • wires parallel to the railroad track

  16. History of wireless communication II • 1928 many TV broadcast trials (across Atlantic, color TV, news) • 1933 Frequency modulation (E. H. Armstrong) • 1958 A-Netz in Germany • analog, 160MHz, connection setup only from the mobile station, no handover, 80% coverage, 1971 11000 customers • 1972 B-Netz in Germany • analog, 160MHz, connection setup from the fixed network too (but location of the mobile station has to be known) • available also in A, NL and LUX, 1979 13000 customers in D • 1979 NMT at 450MHz (Scandinavian countries) • 1982 Start of GSM-specification • goal: pan-European digital mobile phone system with roaming • 1983 Start of the American AMPS (Advanced Mobile Phone System, analog) • 1984 CT-1 standard (Europe) for cordless telephones

  17. History of wireless communication III • 1986 C-Netz in Germany • analog voice transmission, 450MHz, hand-over possible, digital signaling, automatic location of mobile device • was in use until 2000, services: FAX, modem, X.25, e-mail, 98% coverage • 1991 Specification of DECT • Digital European Cordless Telephone (today: Digital Enhanced Cordless Telecommunications) • 1880-1900MHz, ~100-500m range, 120 duplex channels, 1.2Mbit/s data transmission, voice encryption, authentication, up to several 10000 user/km2, used in more than 50 countries • 1992 Start of GSM • in D as D1 and D2, fully digital, 900MHz, 124 channels • automatic location, hand-over, cellular • roaming in Europe - now worldwide in more than 200 countries • services: data with 9.6kbit/s, FAX, voice, ...

  18. History of wireless communication IV • 1994 E-Netz in Germany • GSM with 1800MHz, smaller cells • as Eplus in D (1997 98% coverage of the population) • 1996 HiperLAN (High Performance Radio Local Area Network) • ETSI, standardization of type 1: 5.15 - 5.30GHz, 23.5Mbit/s • recommendations for type 2 and 3 (both 5GHz) and 4 (17GHz) as wireless ATM-networks (up to 155Mbit/s) • 1997 Wireless LAN - IEEE802.11 • IEEE standard, 2.4 - 2.5GHz and infrared, 2Mbit/s • already many (proprietary) products available in the beginning • 1998 Specification of GSM successors • for UMTS (Universal Mobile Telecommunications System) as European proposals for IMT-2000 • Iridium • 66 satellites (+6 spare), 1.6GHz to the mobile phone

  19. History of wireless communication V • 1999 Standardization of additional wireless LANs • IEEE standard 802.11b, 2.4-2.5GHz, 11Mbit/s • Bluetooth for piconets, 2.4GHz, <1Mbit/s • decision about IMT-2000 • several “members” of a “family”: UMTS, cdma2000, DECT, … • Start of WAP (Wireless Application Protocol) and i-mode • first step towards a unified Internet/mobile communication system • access to many services via the mobile phone • 2000 GSM with higher data rates • HSCSD offers up to 57,6kbit/s • first GPRS trials with up to 50 kbit/s (packet oriented!) • UMTS auctions/beauty contests • Hype followed by disillusionment (50 B$ paid in Germany for 6 licenses!) • Iridium goes bankrupt • 2001 Start of 3G systems • Cdma2000 in Korea, UMTS tests in Europe, Foma (almost UMTS) in Japan

  20. History of wireless communication VI • 2002 • WLAN hot-spots start to spread • 2003 • UMTS starts in Germany • Start of DVB-T in Germany replacing analog TV • 2005 • WiMax starts as DSL alternative (not mobile) • first ZigBee products • 2006 • HSDPA(High-Speed Downlink Packet Access) starts in Germany as fast UMTS download version offering > 3 Mbit/s • WLAN draft for 250 Mbit/s (802.11n) using MIMO • WPA2 mandatory for Wi-Fi WLAN devices • 2007 • over 3.3 billion subscribers for mobile phones (NOT 3 bn people!) • 2008 • “real” Internet widely available on mobile phones (standard browsers, decent data rates) • 7.2 Mbit/s HSDPA, 1.4 Mbit/s HSUPA available in Germany, more than 100 operators support HSPA worldwide

  21. Wireless systems: overview of the development cordlessphones wireless LAN cellular phones satellites 1980:CT0 1981: NMT 450 1982: Inmarsat-A 1983: AMPS 1984:CT1 1986: NMT 900 1987:CT1+ 1988: Inmarsat-C 1989: CT 2 1991: CDMA 1991: D-AMPS 1991: DECT 199x: proprietary 1992: GSM 1992: Inmarsat-B Inmarsat-M 1993: PDC 1997: IEEE 802.11 1994:DCS 1800 1998: Iridium 1999: 802.11b, Bluetooth 2000: IEEE 802.11a 2000:GPRS analog 2001: IMT-2000 digital 200?: Fourth Generation (Internet based) 4G – fourth generation: when and how?

  22. Worldwide wireless subscribers (old prediction 1998) 700 600 500 Americas Europe 400 Japan 300 others total 200 100 0 1996 1997 1998 1999 2000 2001

  23. Mobile phones per 100 people 1999 0 10 20 30 40 50 60 Germany Greece Spain Belgium France Netherlands Great Britain Switzerland Ireland Austria Portugal Luxemburg Italy Denmark Norway Sweden Finland 2005: 70-90% penetration in Western Europe

  24. Worldwide cellular subscriber growth Note that the curve starts to flatten in 2000 – 2008: over 3.3 billion subscribers

  25. Cellular subscribers per region (June 2002) 2004: 715 million mobile phones delivered

  26. Total Global Mobile Users 869M / 1.52G / 2G /3.3G Total Analogue Users 71M / 34M / 1M Total US Mobile users 145M / 140M Total Global GSM users 680M / 1.25G1.5G /2.7G Total Global CDMA Users 127M / 202M Total TDMA users 84M / 120M Total European users 283M / 343M Total African users 18.5M / 53M / 83M Total 3G users 130M / 130M Total South African users 13.2M / 19M / 30M European Prepaid Penetration 63% European Mobile Penetration 70.2% Global Phone Shipments 2001 393M / 1G 2008 Global Phone Sales 2Q02 96.7M www.cellular.co.za/stats/stats-main.htm www.gsmworld.com/news/statistics/index.shtml #1 Mobile Country China (139M / 300M) #1 GSM Country China (99M / 282M /483M) #1 SMS Country Philipines #1 Handset Vendor 2Q02 Nokia (37.2%) #1 Network In Africa Vodacom (6.6M / 11M) #1 Network In Asia Unicom (153M) #1 Network In Japan DoCoMo #1 Network In Europe T-Mobile (22M / 28M) #1 In Infrastructure Ericsson SMS Sent Globally 1Q 60T / 135G / 235G /650 G SMS sent in UK 6/02 1.3T / 2.1G SMS sent Germany 1Q02 5.7T GSM Countries on Air 171 / 210 / 220 GSM Association members 574 / 839 Total Cost of 3G Licenses in Europe 110T€ SMS/month/user 36 Mobile statistics snapshots (09/2002 / 12/2004 / 04/2006 / Q4/2007 The figures vary a lot depending on the statistic, creator of the statistic etc.!

  27. Areas of research in mobile communication • Wireless Communication • transmission quality (bandwidth, error rate, delay) • modulation, coding, interference • media access, regulations • ... • Mobility • location dependent services • location transparency • quality of service support (delay, jitter, security) • ... • Portability • power consumption • limited computing power, sizes of display, ... • usability • ...

  28. Simple reference model used here Network Network Application Application Transport Transport Network Network Data Link Data Link Data Link Data Link Physical Physical Physical Physical Medium Radio

  29. Application layer Transport layer Network layer Data link layer Physical layer service location new/adaptive applications multimedia congestion/flow control quality of service addressing, routing device location hand-over authentication media access/control multiplexing encryption modulation interference attenuation frequency Influence of mobile communication to the layer model

  30. Overview of the main chapters Chapter 10: Support for Mobility Chapter 9: Mobile Transport Layer Chapter 8: Mobile Network Layer Chapter 4: Telecommunication Systems Chapter 5: Satellite Systems Chapter 6: Broadcast Systems Chapter 7: Wireless LAN Chapter 3: Medium Access Control Chapter 2: Wireless Transmission

  31. Overlay Networks - the global goal integration of heterogeneous fixed andmobile networks with varyingtransmission characteristics regional vertical handover metropolitan area campus-based horizontal handover in-house

  32. GSM

  33. GSM: Overview • GSM • formerly: Groupe Spéciale Mobile (founded 1982) • now: Global System for Mobile Communication • Today many providers all over the world use GSM(218 countries in Asia, Africa, Europe, Australia, America) • more than 3 billion subscribers in more than 700 networks • more than 75% of all digital mobile phones use GSM • 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…]

  34. Performance characteristics of GSM (wrt. analog sys.) • Communication • mobile, wireless communication; support for voice and data services • Total mobility • international access, chip-card enables use of access points of different providers • Worldwide connectivity • one number, the network handles localization • High capacity • better frequency efficiency, smaller cells, more customers per cell • High transmission quality • high audio quality and reliability for wireless, uninterrupted phone calls at higher speeds (e.g., from cars, trains) • Security functions • access control, authentication via chip-card and PIN

  35. Disadvantages of GSM • There is no perfect system!! • no end-to-end encryption of user data • no full ISDN bandwidth of 64 kbit/s to the user, no transparent B-channel • reduced concentration while driving • electromagnetic radiation • abuse of private data possible • roaming profiles accessible • high complexity of the system • several incompatibilities within the GSM standards

  36. GSM: Mobile Services • GSM offers • several types of connections • voice connections, data connections, short message service • multi-service options (combination of basic services) • Three service domains • Bearer Services • Telematic Services • Supplementary Services bearer services MS GSM-PLMN transit network (PSTN, ISDN) source/ destination network TE MT TE R, S Um (U, S, R) tele services

  37. Bearer Services • Telecommunication services to transfer data between access points • Specification of services up to the terminal interface (OSI layers 1-3) • Different data rates for voice and data (original standard) • data service (circuit switched) • synchronous: 2.4, 4.8 or 9.6 kbit/s • asynchronous: 300 - 1200 bit/s • data service (packet switched) • synchronous: 2.4, 4.8 or 9.6 kbit/s • asynchronous: 300 - 9600 bit/s

  38. Tele Services I • Telecommunication services that enable voice communication via mobile phones • All these basic services have to obey cellular functions, security measurements etc. • Offered services • mobile telephonyprimary goal of GSM was to enable mobile telephony offering the traditional bandwidth of 3.1 kHz • Emergency numbercommon number throughout Europe (112); mandatory for all service providers; free of charge; connection with the highest priority (preemption of other connections possible) • Multinumberingseveral ISDN phone numbers per user possible

  39. Tele Services II • Additional services • Non-Voice-Teleservices • group 3 fax (a standard in 1980 for digital facsimile devices to communicate over analog telephone lines). • voice mailbox (implemented in the fixed network supporting the mobile terminals) • electronic mail (MHS, Message Handling System, implemented in the fixed network) • ... • 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!)

  40. Supplementary services • Services in addition to the basic services, cannot be offered stand-alone • Similar to ISDN services besides lower bandwidth due to the radio link • May differ between different service providers, countries and protocol versions • Important services • identification: forwarding of caller number • suppression of number forwarding • automatic call-back • conferencing with up to 7 participants • locking of the mobile terminal (incoming or outgoing calls) • ...

  41. Architecture of the GSM system • GSM is a PLMN (Public Land Mobile Network) • several providers setup mobile networks following the GSM standard within each country • components • MS (mobile station) • BS (base station) • MSC (mobile switching center) • LR (location register) • subsystems • RSS (radio subsystem): covers all radio aspects • NSS (network and switching subsystem): call forwarding, handover, switching • OSS (operation subsystem): management of the network

  42. Ingredients 1: Mobile Phones, PDAs & Co. The visible but smallest part of the network!

  43. Ingredients 2: Antennas Still visible – cause many discussions…

  44. Ingredients 3: Infrastructure 1 Base Stations Cabling Microwave links

  45. 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

  46. GSM: overview OMC, EIR, AUC fixed network HLR GMSC NSS with OSS VLR MSC VLR MSC BSC Visitor Location Register (VLR) home location register (HLR) A Gateway Mobile Switching Centre provides an edge function within a PLMN (Public Land Mobile Network) GMSC authentication center (AUC) equipment identity register (EIR) The operations and maintenance center (OMC) BSC RSS

  47. GSM: elements and interfaces radio cell BSS MS MS Um radio cell MS RSS BTS BTS Abis BSC BSC A MSC MSC NSS VLR VLR signaling HLR ISDN, PSTN GMSC PDN IWF O OSS EIR AUC OMC

  48. GSM: system architecture radiosubsystem network and switching subsystem fixedpartner networks MS MS ISDNPSTN MSC Um Abis BTS BSC EIR BTS SS7 HLR VLR BTS ISDNPSTN BSC BTS MSC A IWF BSS PSPDNCSPDN

  49. Components MS (Mobile Station) BSS (Base Station Subsystem):consisting of BTS (Base Transceiver Station):sender and receiver BSC (Base Station Controller):controlling several transceivers Interfaces Um : radio interface Abis : standardized, open interface with 16 kbit/s user channels A: standardized, open interface with 64 kbit/s user channels System architecture: radio subsystem radiosubsystem network and switchingsubsystem MS MS Um Abis BTS MSC BSC BTS A BTS MSC BSC BTS BSS

  50. System architecture: network and switching subsystem networksubsystem fixed partnernetworks • Components • MSC (Mobile Services Switching Center): • IWF (Interworking Functions) • ISDN (Integrated Services Digital Network) • PSTN (Public Switched Telephone Network) • PSPDN (Packet Switched Public Data Net.) • CSPDN (Circuit Switched Public Data Net.) • Databases • HLR (Home Location Register) • VLR (Visitor Location Register) • EIR (Equipment Identity Register) ISDNPSTN MSC EIR SS7 HLR VLR ISDNPSTN MSC IWF PSPDNCSPDN

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