Introduction to Wireless Communications - ERNET

1 Wireless CommunicationsIntroduction to Wireless CommunicationsRanjan BoseDepartment of Electrical EngineeringIndian Institute of Technology, DelhiIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering2 Wireless CommunicationsOutline What is Wireless Communications ? History of Wireless Communications The advantages The challenges The types The Indian factor Existing Wireless Systems Emerging Wireless SystemsIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering3 Wireless CommunicationsWhat is Wireless communication ? Transmitting/receiving voice and data using electromagnetic waves in open space The information from sender to receiver is carrier over a well-definedfrequency band (channel) Each channel has a fixedfrequency bandwidthand Capacity(bit-rate) Different channels can be used to transmit information in paralleland independently.

2 Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering4 Wireless CommunicationsExample Assume a spectrum of 120 KHzis allocated over a base frequency for communication between stations A and B Each channel occupies 40 KHzChannel 1 (b - b+40) Channel 2 (b+40 - b+80)Channel 3 (b+80 - b+120) Station AStation BIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering5 Wireless CommunicationsTypes of Wireless communication Mobile Cellular Phones (GSM / ) Portable IEEE (WiFi), IEEE (UWB) Fixed IEEE (WirelessMAN)Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering6 Wireless CommunicationsTypical Frequencies FM Radio~ 88 MHz TV Broadcast~ 200 MHz GSM Phones ~ 900 MHz GPS~ GHz PCS Phones~ GHz Bluetooth ~ GHz WiFi~ GHzIndian Institute of Technology.

3 DelhiRanjan BoseDepartment of Electrical Engineering7 Wireless CommunicationsThe Electromagnetic Spectrum Propagation characteristics are different in each frequency bandUV1 MHz1 kHz1 GHz1 THz1 PHz1 EHzinfraredvisibleX raysGamma raysAM radioS/W radioFM radioTVTV cellularLFHFVHFUHFSHFEHFMF 30kHz 300kHz3 MHz30 MHz300 MHz30 GHz 300 GHz10km1km100m10m1m10cm1cm100mm3 GHzEHF - Extreme High Frequency SHF - Super High Frequency UHF - Ultra High Frequency VHF - Very High Frequency HF - High Frequency MF - Medium Frequency LF - Low Frequency VLF - Very Low FrequencyIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering8 Wireless CommunicationsJames Clerk Maxwell(1831 1879)Scottish, Professor of physics, King s College (London) and Cambridge University.

4 Formulated the theory of electromagnetismfrom 1865 to = = + = ="From a very long view of the history of mankind - seen from, say, ten thousand years from now -there can be little doubt that the most significant event of the 19th century will be judged as Maxwell's discovery of the laws of electrodynamics. The American Civil War will fade into provincial insignificance in comparison with this important scientific event of the same decade."Richard Feynman, Lectures on Physics, Vol. II His work established the theoretical foundation for the development of Wireless Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering9 Wireless CommunicationsMartin Cooper, Motorola, develops first handheld cellular phone in 19732003 - US cellular subscribers exceed 150M19001920 Guglielmo Marconi (1874-1937) development of Wireless telegraphy trans-Atlantic 1901 Prof.

5 H. Hertz (1857-1894) experimental validation of Maxwell 1886-1888 at Karlsruhe18801860 Prof. J. Maxwell (1831-1879) theory of electromagnetism developed in 18651940 First television broadcast -192819801960 Two-way mobile radio services 1960s 1970s20001983 - Cellular AMPS service in ChicagoKDKA Radio -1920 Dave interviews at Bell Labs for Mobile Phone project This thing isn t going anywhere. 2008 - Indian cellular subscribers exceed 300 MTimeline of Wireless Communications Development ..Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering10 Wireless CommunicationsWhy Wireless communication ?(1) Freedom from wires No cost of installing wires or rewiring No bunches of wires running here and there Auto magical instantaneous Communications without physical connection setup, , Bluetooth, WiFi Global Coverage Communications can reach where wiring is infeasible or costly, , rural areas, old buildings, battlefield, vehicles, outer space (through communication Satellites)Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering11 Wireless CommunicationsWhy Wireless communication ?

6 (2) Stay Connected Roamingallows flexibility to stay connected anywhere and any time Rapidly growing marketattests to public need for mobility and uninterrupted access Flexibility Services reach you wherever you go (Mobility). , you don t have to go to your lab to check your mail Connect to multiple devicessimultaneously (no physical connection required)Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering12 Wireless CommunicationsWhy Wireless communication ?(3) Increasing dependence on telecommunication services for business and personal reasons Consumers and businesses are willing to pay for it Basic Mantra: Stay connected anywhere, Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering13 Wireless CommunicationsChallenges(1) Efficient Hardware Low powerTransmitters, Receivers Low PowerSignal Processing Tools Efficient use of finiteradio spectrum Cellular frequency reuse, medium access control protocols.

7 Integrated services voice, data, multimediaover a single network service differentiation, priorities, resource sharing,..Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering14 Wireless CommunicationsMultimedia RequirementsVoiceVideoDataDelayPacket LossBERData RateTraffic<100ms-<100ms<1%0<1%10-310-61 0-68-32 Kbps1-100 Mbps1-20 MbpsContinuousBurstyContinuousOne-size-f its-all protocols and design do not workwellWired networks use this approach, with poor resultsIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering15 Wireless CommunicationsChallenges(2) Network support for user mobility(mobile scenarios) location identification, handover,.. Maintaining quality of serviceover unreliable links Connectivity and coverage (internetworking) CostefficiencyIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering16 Wireless CommunicationsChallenges(3) Fading Multipath Higher probability of data corruption Hence, need for stronger channel codes Need for stronger Security mechanisms privacy, authentication.

8 Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering17 Wireless CommunicationsWireless vs Mobile NOTE: Wireless does not necessarily mean mobile Wireless Systems may be Fixed ( , Metropolitan Area Network) Portable( , Wireless interaction between TV and VCR) Mobile( , mobile phone)Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering18 Wireless CommunicationsTypes of Wireless communication (1) Radio Transmission Easily generated, omni-directionally travel long distances, easily penetrate buildings Problems: frequency-dependent relative low bandwidth for data communication tightly licensed by the governments Microwave Transmission Widely used for long distance communication Gives a high S/N ratio, relatively inexpensive Problems.

9 Don t pass through buildings well weather and frequency-dependentIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering19 Wireless CommunicationsTypes of Wireless communication (2) Infrared and Millimeter Waves Widely used for short-range communication Unable to pass through solid objects Used for indoor Wireless LANs, not for outdoors Lightwave Transmission Unguided optical signal, such as laser Connect two LANs in two buildings via laser mounted on their roof Unidirectional, easy to install, don t require license Problems: unable to penetrate rain or thick fog laser beam can be easily diverted by turbulent airIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering20 Wireless CommunicationsWireless Systems : Range ComparisonSatelliteLinksSWRadioMWRadioFM RadioMobileTelephony,WLLWLANsBluetoothIR 1,000 Km100 Km10 Km1 Km100 m10 m1 mIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering21 Wireless CommunicationsGrowth.

10 Technology take-up time to 50M usersTelephoneTVRadioWireless CommunicationsInternet35 years75 years4 years12 years13 yearsMobile Phones in India10 yearsIndian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering22 Wireless CommunicationsUser Growth1996199820002002200402004006008001 ,000 Fixed accessMobile accessFixed andmobile InternetMobile InternetMillion subscribers Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering23 Wireless CommunicationsTraffic Growth 0 25 1998 1999 2000 2001 50 75 100 125 150 Traf f ic Voice Internet access Indian Institute of Technology, DelhiRanjan BoseDepartment of Electrical Engineering24 Wireless CommunicationsMobile Phones by Numbers!