History
Opticaltelephone
Thefirstwirelesstelephoneconversationintheworldappearedin1880.Atthattime,theopticaltelephonewasusedbyAlexanderGraham.BellandCharlesSumnerTianteinventedandappliedforapatent.Opticaltelephonestransmitvoicesignalsthroughmodulatedlightbeams.Atthattime,therewasnoequipmenttoprovideelectricity,andevensciencefictiondidnotevenmentionlasers.Theirinventiondidnotseemtobeofpracticalvalueatthetime,andtheeffectoftelephonecallswasalsolimitedbysunlightandweather.Opticalphonesandfree-spaceopticalcommunicationsystemsarethesame.Therecanbenoobjectsblockingthebeambetweenthetransmitterandthetransmitter.Decadeslater,theopticaltelephonewasappliedtothefieldofmilitarycommunications.
Earlywork
DavidE.Hughesusedatransmittertotransmitradioseveralhundredmetersawayin1878.AtthattimeMaxwell'selectromagnetictheorywasnotwellknowntotheworld,socontemporaryscientistsregardedthisinventionastheresultofinduction.In1885,ThomasEdisonusedvibratormagnetsasinductivetransmission.In1888,EdisondeployedasignaltransmissionsystemfortheHayeValleyRailway.In1891,heobtainedaradiopatentusinginductance(USPatent465,971).
In1888,HeinrichHertzdemonstratedtheexistenceofelectromagneticwaves,whichbecamethebasisformostofthelaterwirelesstechnologies.Hertzprovedthatelectromagneticwavestravelinastraightlineinspaceandcanbereceivedbyexperimentalequipment,buthedidnotcontinueotherrelatedexperiments.JagdishChandraBossdevelopedanearlyradiodetectiondevicethatalsohelpedtounderstandthecharacteristicsofelectromagneticwaveswithinafewcentimetersofwavelength.
Radio
"Wireless"originallyreferredtoradioreceivers,ortransceivers(devicesthatcanbeusedforbothtransmissionandreception),asearlyastheeraofwirelesstelegraphy.Similardeviceshavebeenapplied.Nowtheterm"wireless"referstomodernwirelesscommunications,suchascellularnetworksandwirelessbroadbandcommunications.Thetermwirelessalsoreferstoanyapplicationthatcanbecarriedoutwithoutwires,suchas"wirelessremotecontrol"and"wirelessenergy".Conversion”withoutdistinguishingwhethertheactualapplicationtechnologyisradio,infraredorultrasonic.
GuglielmoMarconiandKarlBraunwontheNobelPrizeinPhysicsin1909fortheircontributionstowirelesstelegraphy.
Mode
Wirelesscommunicationcanbecarriedoutinthefollowingways:
Radio
Mainarticle:Radio
Radiocommunicationandmicrowavecommunicationareusedinlong-distancecommunicationandneedtobeequippedwithahigh-directionalantennaorshort-distancecommunication.
Freespaceopticalcommunication
Mainarticle:Freespaceopticalcommunication
Freespaceopticalcommunicationsystem(FSO)useslightinfreespace(thatis,air,Wirelessopticalcommunicationtechnologythattravelsinouterspaceandvacuumtotransmitsignals.Thefreespaceopticalcommunicationsystemusesvisiblelightorinfrared,suchasremotecontrolandinfraredcommunication.
Acousticcommunication
Soundwavesandultrasonicwavesarecommonlyusedinshort-distanceapplicationsthatusesoundwavestotransmitsignals.
Electromagneticinduction
Electromagneticinductionismainlyusedinlow-energyandshort-distancecommunicationapplications,suchaspacemakersandshort-distanceRFIDtags.
Wirelessnetwork
Wirelessnetworkcanmeetmanydifferentneeds,themostcommononeistofacilitatelaptopuserstoconnecttotheInternetonthewaytoandfromdifferentplaces,anotherpurposeItisconnectedtotheInternetbymobilephones.Iftheactuallocationofacertainnetworksegmentoftenchanges,itismorereasonabletouseawirelessnetworktoconnect.Thewirelessnetworkcanbeusedinthefollowingsituations:
Thedistanceofthenetworkexceedsthelengthallowedbythegeneralwirednetwork.
Asabackupnetwork,itisusedwhenthenormalnetworkisabnormal.
Connectmobileortemporarynodes.
Ingeneralnetworkwiringisdifficultorthecostistoohigh.
Mobileusersconnectorconnecttomobilenetworks.
Whendevelopingradiofrequencywirelessnetworks,designersneedtoconsiderthefollowingfactors:
UsehundredstothousandsofMHzOrtheGHzband.
Operatingrangeandbatterylife.
Sensitivityanddatarate.
Networktopologyandnodeintelligence.
Theapplicationsofwirelessnetworksincludepoint-to-pointcommunication,point-to-multipointcommunication,broadcasting,cellularnetworksandotherwirelessnetworksandWi-Fitechnology.
Electromagneticwavespectrum
Light,color,AMandFMbroadcasting,andmanyelectronicdevicesalluseradiowavespectrum.Theradiofrequencyspectrumthatcanbeusedforcommunicationisregardedaspublicproperty.Itismanagedbynationalagencies,suchastheFederalCommunicationsCommissionintheUnitedStatesandOfcomintheUnitedKingdom.Theseagenciesdefinewhocanusewhichfrequencybandandwhattheirpurposeis.Ifthepublicfrequencybandisliketheelectromagneticspectrumforpersonaluse,theremaybeconfusionifthereisnosimilarcontroloralternativeconfigurationmeasures.Forexample,theaircraftdoesnothaveaspecialfrequencythatcanbeusedontheairtrafficcontrol,andthesignaloftheamateurradiooperatorinterfereswiththeairtrafficcontrolsignal,Makingitimpossibleforthepilottolandtheplanenormally.Thefrequencybandofwirelesscommunicationisfrom9kHzto300GHz.
Applicationofwirelesscommunicationtechnology
Mobilephone
Mobilephoneshouldbeoneofthemostwidelyknownapplicationsofwirelesscommunication.Attheendof2010,thereweremorethan4.6billionmobilephones.Mobilephonesuseradiowavestoenableusersindifferentplacestocalleachother.Theusercanusethemobilephonewithintherangeofthemobilecommunicationbasestation,andthebasestationwillpickupandreceivethesignalfromthemobilephone.
Wirelessdatatransmission
Wirelessdatatransmissionisanindispensablepartofmobilecomputing.Therearemanyavailabletechnologies.Thedifferenceistheavailability,coverage,andperformanceintheregion.Insomecases,usersmustbeabletodeploymultipleconnectionmethodsandswitchbetweendifferentmodes.Inordertosimplifythetimespentbyusers,connectionmanagementsoftwarecanbeused,orMVPNcanbeusedtoprocessseveralconnectionsintoasinglesecurevirtualnetwork..Thefollowingaresomewirelesscommunicationsusedinwirelessdatatransmission:
Wi-Fiisawirelesslocalareanetwork,allowingportablecomputingdevicestoconnecttotheInternetinasimpleway,throughIEEE802.11a,b,g,nandotherstandards,thespeedofWi-Fiisclosetosomewirednetworks.Wi-Fihasbecomethedefactostandardforhotspotsinhomes,officesandpublicspaces.SomecompanieschargeWi-Fionceamonth,andsomecompaniesprovideitforfree,becauseprovidingWi-Ficanincreasethesalesoftheirproducts.
Honeycombnetwork:Itcanbeusedaslongasitiswithintentofifteenkilometersfromthenearestbasestation.AndGPRS,to3GnetworkslikeW-CDMA,GSMEnhancedDataRateEvolution(EDGE)orCDMA2000.
Mobilesatellitecommunication:Itcanbeusedinsituationswhereotherwirelesstechnologiescannotbeused,suchaslargeruralareasorremoteplaces.Communicationsatellitesareparticularlyimportantintransportation,aviation,navigationandmilitaryaffairs.
Wirelesssensornetwork:Itcandirectlydetectrelatedphysicalquantities,monitorandcollectdata,producemeaningfuldisplaysforpeopletowatch,andprovidesomedecision-makingfunctions.
Wirelesspowersupply
Mainarticle:Wirelesspowersupply
WirelesspowersupplyreferstotheThepowerispassedtoanotherdevicethatdoesnothaveabuilt-inpowersupply.Therearetwobasicwirelesspowersupplymethods,whichcanusebeam/laser,radioormicrowavetransmission,orusenear-fieldinduction.Electromagneticwavemagneticfieldsareusedinseveralways.
Wirelessmedicaltechnology
Newtechnologieslikemobilebodyareanetworks(MBAN)canusewirelesstechnologytomonitorbloodpressure,heartbeat,oxygenconcentrationandbodytemperature.Thewirelessbodyareanetworksendsalow-powerwirelesssignaltothereceiver,andthentransmitsittothemonitoringequipmentornursingstation.Thistechnologyreducestheriskofinfection,whetherintentionallyorunintentionally,orproblemscausedbybrokenwires.
Computerinterfaceequipment
Theearliestkeyboards,miceandotherequipmentarewired,andthenwirelessinterfaceequipmentslowlyappeared,mostofwhichuseBluetoothtechnology.TheresponseItmaybeslightlyslowerthanwireddevices,butthegapbetweenthetwoisgettingsmallerandsmaller.
Wirelessinterfacedevicesofcomputerssuchaskeyboardsandmicearegenerallybattery-poweredandtransmitradiofrequencysignalstothereceiverconnectedtothecomputer’sUSBport.Becauseoftheuseofradiofrequencysignals,datacanbetransmittedwirelessly,andtherangeofusecanbeexpanded,generallyuptothreemeters.Distance,physicalobstacles,otherwirelesssignalsandeventhehumanbodymayreducethesignalquality.
Attheendof2007,theissueofwirelesskeyboardsecuritybegantobediscussed.Atthattime,itwasdiscoveredthatMicrosoftwasusingthe27MHzseries,anditsencryptionimplementationwashighlylackinginsecurity.
Therealization,equipmentandrelatedstandardsofwirelesscommunication
Radio.
Broadcast.
Amateurradio.
Landmobileradiosystemorprofessionalmobileradio:groundrelayradio,P25,OpensSky,EDACS,DMR,dPMR.
Wirelessphone:digitallyenhancedwirelessphonesystem.
Honeycombnetwork:0G,1G,2G,3G,4G.
Short-distancepoint-to-pointcommunication:wirelessmicrophone,remotecontrol,IrDA,radiofrequencyidentification(RFID),TransferJet,wirelessuniversalserialbus,DSRC,EnOcean,nearfieldcommunication.
Wirelesssensingnetwork:ZigBee,EnOcean,wirelesspersonalnetwork,Bluetooth,TransferJet,ultra-wideband(UWB).
Wirelessnetwork:wirelesslocalareanetwork(WLAN,likeWi-FiandHiperLAN,etc.),globalinteroperabilitymicrowaveaccess(WiMAX).
Relateditems
Radio
Hotspot(Wi-Fi),wirelesspowersupply,wirelessaccessdevice
LightInternetTechnology(Li-Fi)
PersonalAreaNetwork
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