Wireless and Mobile Computing - Sajjad Ali Mushtaq

Wireless and Mobile ComputingSajjad Ali MushtaqWhat is Wireless Communication ?Transmitting voice, data, video and other services data using electromagnetic waves in open space (atmosphere)Electromagnetic waves Travel at speed of light (c = 3x108 m/s)Has a frequency (f) and wavelength (λ)c = f x λ Where c = wave speedHigher frequency means higher energyThe higher the energy the more penetrating are the radiations2Types of Wireless CommunicationCelullarWireless computer networkRadio service3Multiservice Point-to-Multipoint Wireless Network 45Electromagnetic Radiation Spectrum6The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object has a different meaning, and is instead the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object.Wavelength of Some TechnologiesGSM Phones: frequency ~= 900 Mhz wavelength ~= 33cmPCS Phonesfrequency ~= 1.8 Ghzwavelength ~= 17.5 cm Bluetooth: frequency ~= 2.4Gz wavelength ~= 12.5cm7Wireless Media Standards8Types of Electromagnetic CarriersWhen the distance between the sender and receiver is short (e.g. TV box and a remote control) infrared waves are usedFor long range distances between sender and receiver (e.g. TV broadcasting and cellular service) both microwaves and radio waves are usedradio waves are ideal when large areas need to be covered and obstacles exist in the transmission pathmicrowaves are good when large areas need to be covered and no obstacles exist in the transmission path910Wireless Applications (Services)11Advantages and Disadvantages of Wireless Communicationadvantages:mobilitya wireless communication network is a solution in areas where cables are impossible to install (e.g. hazardous areas, long distances etc.)easier to maintaindisadvantages:has security vulnerabilitieshigh costs for setting the infrastructureunlike wired comm., wireless comm. is influenced by physical obstructions, climatic conditions, interference from other wireless devices 12Wireless Systems: Range ComparisonSatelliteLinksSWRadioMWRadioFMRadioMobileTelephonyWLANsBlueooth1,000 Km100 Km10 Km1 Km100 m10 m1 m13Wireless RevolutionCellular is the fastest growing sector of communicationindustry (exponential growth since 1982, Four generations of wireless (5G is on its way)First Generation (1G): Analog 25 or 30 KHz FM, voice only, mostly vehicular communicationSecond Generation (2G): Narrowband TDMA and CDMA, voice and low bit-rate data, portable units. 2.5G increased data transmission capabilitiesThird Generation (3G): Wideband TDMA and CDMA, voice and high bit-rate data, portable units4G/5G1415THE RADIO PATENTS Tesla filed his basic radio patent applications in 1897. They were granted in 1900. Marconi's first patent application in America, filed on November 10, 1900, was turned down. Marconi's revised applications over the next three years were repeatedly rejected because of the priority of Tesla and other inventors. 16 PATENTS17Magnifying TransmitterWhat was Magnified?1819History: Historical OverviewIt Started with the Telegraph ...“We call the electric telegraph the most perfect invention of modern times ... as anything more perfect than this is scarcely conceivable, and we really begin to wonder what will be left for the next generation”An electrical telegraph is a telegraphy that uses electrical signals, usually conveyed via telecommunication lines or radio. The electromagnetic telegraph is a device for human-to-human transmission of coded text messages.2021Critical Attributes of Telecommunications SystemsSpeedAbility to transmit information in real-timeElectronic transmission: faster than transportationCoverageBeyond regional: national and international in scaleMetcalf’s Law: the more connected, the more usefulReliabilityCostSecurityTransmitted information as knowledge, news, secretsAlways an element of government oversight and control22Origins of Coded Transmission1793, Revolutionary FranceAerial Telegraph, invented by Claude ChappeExtensive network throughout France1840s, Samuel F. B. MorseCoded transmission via electronic meansRapidly spread throughout US and EuropeInternational Telegraph Union (ITU) formed in 186523Submarine Telegraphy: High Tech of the late 19th Century1850: Dover-to-Calais, first submarine line1858: First transatlantic cableBreaks after 3 months!1866: Relaid with higher quality cable Development of cable materials, technology of laying, repairTypical “Performance”:1870: London to Bombay in 4 minutes, 22 seconds1901: London to British Guiana, 22 minutes1924: Telegram around the world in 80 seconds24Radio Telegraphy(also know as “Wireless”)Radio technologyCommunicate with ships and other moving vehiclesMessages sprayed into the “ether” crossing boundariesDownfall of the nationally supported monopolistic telegraph companies1896: Guglielmo MarconiFirst demonstration of wireless telegraphyBuilt on work of Maxwell and Hertz to send and receive Morse CodeBased on long wave (>> 1 km), spark transmitter technology, requiring very large, high power transmittersFirst used by British Army and Navy in the Boer War25Wireless1907: Commercial Trans-Atlantic Wireless ServiceHuge ground stations: 30 x 100m antenna mastsBeginning of the end for cable-based telegraphyWW I: Rapid development of communications intelligence, intercept technology, cryptography1920: Marconi discovers shortwave (<100 m) radioLongwave follow contour of landVery high transmit power, 200 KW+Shortwaves reflect, refract, and absorb, like lightBounce off ionosphereHigher frequencies made possible by vacuum tube (1906)Cheaper, smaller, better quality transmitters26Broadband Wireless TechnologyHigher data rates obtainable with broadband wireless technologyGraphics, video, audioShares same advantages of all wireless services: convenience and reduced costService can be deployed faster than fixed serviceNo cost of cable plantService is mobile, deployed almost anywhere27Limitations and Difficulties of Wireless TechnologiesWireless is convenient and less expensive Limitations and political and technical difficulties inhibit wireless technologiesLack of an industry-wide standardDevice limitationsE.g., small LCD on a mobile telephone can only displaying a few lines of textE.g., browsers of most mobile wireless devices use wireless markup language (WML) instead of HTML2829Wireless Networks Compared to Fixed NetworksHigher loss-rates due to interferenceother EM signals, objects in path (multi-path, scattering) Limited availability of useful spectrumfrequencies have to be coordinated, useful frequencies are almost all occupiedLow transmission ratesHigher delays, higher jitterconnection setup time for cellular in the second range, several hundred milliseconds for wireless LAN systemsLower security, simpler active attackingradio interface accessible for everyonebase station can be simulated, thus attracting calls from mobile phonesAlways shared mediumsecure access mechanisms important30Shifting Trends3132Impressive Wireless Infrastructure!SatelliteMacro-CellMicro-CellUrbanIn-BuildingPico-CellGlobalSuburbandik ©In-Room(BlueTooth)33Wireless Network OverlaySatelliteMacro-CellMicro-CellUrbanIn-BuildingPico-CellGlobalSuburbandik ©34GSM Base Stations in EuropeNokia PrimeSiteEricsson RBS 2000September 19973536Design ChallengesHardware DesignPrecise componentsSmall, lightweight, low powerCheapHigh frequency operationsSystem DesignConverting and transferring informationHigh data ratesRobust to noise and interferenceSupports many usersNetwork DesignConnectivity and high speedEnergy and delay constrains3738Text BookWIRELESS COMMUNICATIONSAND NETWORKSBy William Stallings2nd Edition39Transmission FundamentalsSignals for Conveying InformationRelationship between Data Rate and BandwidthAnalog and Digital Data TransmissionAnalog and Digital DataAnalog and Digital SignalingAnalog and Digital TransmissionChannel CapacityNyquist BandwidthShannon Capacity Formula40Transmission MediaTransmission mediaTransmission media classificationTransmission Media characteristics and design specificationsGuided and Unguided mediaWireless Transmission FrequenciesAntennasWireless Propagation41Wireless TransmissionWireless TransmissionWireless Transmission Examplesterrestrial microwavesatellite microwavebroadcast radioInfraredWireless Transmission Systems ComparisonWireless Propagation ModesMultiplexing TDM, FDM WDM 42Communication NetworksComparison of basic communication network technologiesCircuit switchingPacket switchingFrame relayATM43Protocols and the TCP/IP Protocol SuiteRequirement of ProtocolWhy Layered Approach is AdoptedKey Features of a ProtocolSimple Protocol ArchitectureAddressingTCP/IP and OSI modelGeneral Networking Terminology44Wireless Communication TechnologyUnderlying technology of wireless transmissionEncoding of analog and digital data for wireless transmission45Antennas and PropagationPrinciples of radio and microwaveAntenna performanceWireless transmission modesFading46Antennas and PropagationElectric and Magnetic Field CouplingEM RadiationsPeriod, Frequency, and WavelengthPhase Lag and Phase LeadAntennas Why???Antenna AnalogyWhy Separate TX and RX Antennas Transmission are RequiredTransmission Line as an AntennaWorking of an AntennaFar And Near FieldsAntennas CharacteristicsPolarizationAntenna and WavelengthAntenna GainAntenna Length47Signal Encoding TechniquesWireless transmissionAnalog and digital dataAnalog and digital signalsSignal encoding techniquesdigital data, digital signalNRZ, multilevel binary, biphase, modulation rateanalog data, digital signalPCM, DMdigital data, analog signalASK, FSK, BFSK, PSKanalog data, analog signalAM, FM, PM48Spread SpectrumFrequency Hopping Direct Sequence Spread Spectrum (DSSS)Code Division Multiple Access (CDMA)49Coding and Error ControlForward Error Correction (FEC)Using redundancy for error detectionAutomatic Repeat Request (ARQ) techniques50Satellite CommunicationsGeostationary satellites (GEOS)Low-earth orbiting satellites (LEOS)Medium-earth orbiting satellites (MEOS)Capacity allocation51Cellular Wireless NetworksCellular wireless network design issuesFirst generation analog (traditional  mobile telephony service)Second generation digital cellular networksTime-division multiple access (TDMA)Code-division multiple access (CDMA)Third generation networksFourth generation networks52GSMGlobal System for Mobile CommunicationDigital TransmissionISDN compatibilityWorldwide roaming in other GSM networksProvides a model for 3G Cellular systems (UMTS) 53Network Simulator 2ns -2 stands for Network Simulator version 2.ns -2:Is a discrete event simulator for networking researchWork at packet level.Provide substantial support to simulate bunch of protocols like TCP, UDP, FTP, HTTP and DSR.Simulate wired and wireless network.Is primarily Unix based but can also be used with Windows via Cygwin.Use TCL as its scripting language.ns -2 is a standard experiment environment in research community.NS2 is also being used for Network on Chip Simulations e.g. flit arrival rate, latency, jitter evaluation and topology comparison54Software Defined RadiosApplication of Learned ConceptsApplication of most of the conceptsA Software Defined Radio (SDR) is a system where components that have been typically implemented in hardware (e.g. mixers, filters, amplifiers, modulators/demodulators, etc.) are instead implemented by means of software on a personal computer or embedded system.5556Thank You57