本科毕业论文中英文翻译WirelessCommunications无线通信.docx

本科毕业论文中英文翻译WirelessCommunications无线通信.docx

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本科毕业论文中英文翻译WirelessCommunications无线通信

本科毕业论文中英文翻译--Wireless-Communications无线通信

WirelessCommunications*

by

JoshuaS.Gans,StephenP.KingandJulianWright

1.Introduction

In1895,GuglielmoMarconiopenedthewayformodernwirelesscommunicationsbytransmittingthethree-dotMorsecodefortheletter‘S’overadistanceofthreekilometersusingelectromagneticwaves.Fromthisbeginning,wirelesscommunicationshasdevelopedintoakeyelementofmodernsociety.Fromsatellitetransmission,radioandtelevisionbroadcastingtothenowubiquitousmobiletelephone,wirelesscommunicationshasrevolutionizedthewaysocietiesfunction.

Thischaptersurveystheeconomicsliteratureonwirelesscommunications.Wirelesscommunicationsandtheeconomicgoodsandservicesthatutiliseithavesomespecialcharacteristicsthathavemotivatedspecialisedstudies.First,wirelesscommunicationsrelieson

communicationtechnologies.Section3thenconsiderstheeconomicissuesassociatedwithmobiletelephonyincludingspectrumallocationandstandards.Section4surveysrecenteconomicstudiesofthediffusionofmobiletelephony.Finally,section5reviewsissuesofregulationandcompetition;inparticular,theneedforandprinciplesbehindaccesspricingformobilephonenetworks.

2.Background

Marconi’spioneeringworkquicklyledtovarietyofcommercialandgovernment（particularlymilitary）developmentsandinnovations.Intheearly1900s,voiceandthenmusicwastransmittedandmodernradiowasborn.By1920,commercialradiohadbeenestablishedwithDetroitstationWWJandKDKAinPittsburgh.Wirelesstelegraphywas

firstusedbytheBritishmilitaryinSouthAfricain1900duringtheAnglo-Boerwar.TheBritishnavyusedequipmentsuppliedbyMarconitocommunicatebetweenshipsinDelagoaBay.ShippingwasamajorearlyclientforwirelesstelegraphyandwirelesswasstandardforshippingbythetimetheTitanicissueditsradiodistresscallsin1912.1

Earlyon,itwasquicklyrecognizedthatinternationalcoordinationwasrequiredforwirelesscommunicationtobeeffective.Thiscoordinationinvolvedtwofeatures.First,thepotentialforinterferenceinradiotransmissionsmeantthatatleastlocalcoordinationwasneededtoavoidthetransmissionofconflictingsignals.Secondly,withspectrumtobeusedforinternationalcommunicationsandareassuchasmaritimesafetyandnavigation,coordinationwasnecessarybetweencountriestoguaranteeconsistencyinapproachtotheseservices.Thisdrovegovernmentinterventiontoensurethecoordinatedallocationofradiospectrum.

2.1SpectrumAllocation

Radiotransmissioninvolvestheuseofpartoftheelectromagneticspectrum.Electromagneticenergyistransmittedindifferentfrequenciesandthepropertiesoftheenergydependonthefrequency.Forexample,visiblelighthasafrequencybetween4×1014and7.5×1014Hz.2Ultravioletradiation,X-raysandgammarayshavehigherfrequencies（orequivalentlyashorterwavelength）whileinfraredradiation,microwavesandradiowaveshavelowerfrequencies（longerwavelengths）.Theradiofrequencyspectruminvolveselectromagneticradiationwithfrequenciesbetween3000Hzand300GHz.3

Evenwithintheradiospectrum,differentfrequencieshavedifferentproperties.AsCave（2001）notes,thehigherthefrequency,theshorterthedistancethesignalwilltravel,butthegreaterthecapacityofthesignaltocarrydata.Thetasksofinternationallycoordinatingtheuseofradiospectrum,managinginterferenceandsettingglobalstandardsareundertakenbytheInternationalTelecommunicationUnion（ITU）.TheITUwascreatedbytheInternationalTelecommunicationsConventionin1947buthaspredecessorsdatingbacktoapproximately1865.4ItisaspecialistagencyoftheUnitedNationswithover180members.

TheRadiocommunicationSectoroftheITUcoordinatesglobalspectrumusethroughtheRadioRegulations.Theseregulationswerefirstputinplaceatthe1906BerlinInternationalRadiotelegraphConference.Allocationoftheradiospectrumoccursalongthreedimensions–thefrequency,thegeographiclocationandthepriorityoftheuserwithregardstointerference.Theradiospectrumisbrokenintoeightfrequencybands,rangingfromVeryLowFrequency（3to30kHz）uptoExtremelyHighFrequency（30to300GHz）.Geographically,theworldisalsodividedintothreeregions.TheITUthenallocatescertainfrequenciesforspecificusesoneitheraworldwideoraregionalbasis.IndividualcountriesmaythenfurtherallocatefrequencieswithintheITUinternationalallocation.Forexample,intheUnitedStates,theFederalCommunicationsCommission’s（FCC’s）tableoffrequencyallocationsisderivedfromboththeinternationaltableofallocationsandU.S.allocations.Usersarebrokenintoprimaryandsecondaryservices,withprimaryusersprotectedfrominterferencefromsecondaryusersbutnotviceversa.

Asanexample,in2003,thebandbelow9kHzwasnotallocatedintheinternationalortheU.S.table.9to14kHzwasallocatedtoradionavigationinbothtablesandallinternationalregionswhile14to70kHzisallocatedwithbothmaritimecommunicationsandfixedwirelesscommunicationsasprimaryusers.Thereisalsoaninternationaltimesignalat20kHz.ButtheU.S.tablealsoaddsanadditionaltimefrequencyat60kHz.Internationalregionaldistinctionsbegintoappearinthe70to90kHzrangewithdifferencesinuseandprioritybetweenradionavigation,fixed,radiolocationandmaritimemobileuses.Theseallocationscontinuerightupto300GHz,withfrequenciesabove300GHznotallocatedintheUnitedStatesandthoseabove275GHznotallocatedintheinternationaltable.5

TheITUdealswithinterferencebyrequiringmembercountriestofollownotificationandregistrationprocedureswhenevertheyplantoassignfrequencytoaparticularuse,suchasaradiostationoranewsatellite.

2.2Therangeofwirelessservices

Radiospectrumisusedforawiderangeofservices.Thesecanbebrokenintothefollowingbroadclasses:

•Broadcastingservices:

includingshortwave,AMandFMradioaswellasterrestrialtelevision;

•Mobilecommunicationsofvoiceanddata:

includingmaritimeandaeronauticalmobileforcommunicationsbetweenships,airplanesandland;landmobileforcommunicationsbetweenafixedbasestationandmovingsitessuchasataxifleetandpagingservices,andmobilecommunicationseitherbetweenmobileusersandafixednetworkorbetweenmobileusers,suchasmobiletelephoneservices;

•FixedServices:

eitherpointtopointorpointtomultipointservices;

•Satellite:

usedforbroadcasting,telecommunicationsandinternet,particularlyoverlongdistances;

•Amateurradio;

•OtherUses:

includingmilitary,radioastronomy,meteorologicalandscientificuses.6

Theamountofspectrumallocatedtothesedifferentusesdiffersbycountryandfrequencyband.Forexample,intheU.K.,40%ofthe88MHzto1GHzbandoffrequenciesareusedforTVbroadcasting,22%fordefense,10%forGSMmobileand1%formaritimecommunications.Incontrast,noneofthe1GHzto3GHzfrequencyrangeisusedfortelevision,19%isallocatedtoGSMandthird-generationmobilephones,17%todefenseand23%foraeronauticalradar.7

Thenumberofdifferentdevicesusingwirelesscommunicationsisrisingrapidly.Sensorsandembeddedwirelesscontrollersareincreasinglyusedinavarietyofappliancesandapplications.Personaldigitalassistants（PDAs）andmobilecomputersareregularlyconnectedtoe-mailandinternetservicesthroughwirelesscommunications,andwirelesslocalareanetworksforcomputersarebecomingcommoninpublicareaslikeairportlounges.However,byfarthemostimportantanddramaticchangeintheuseof

wirelesscommunicationsinthepasttwentyyearshasbeentheriseofthemobiletelephone.

2.3Theriseandriseofmobiletelephony

Thehistoryofmobiletelephonescanbebrokenintofourperiods.Thefirst（pre-cellular）periodinvolvedmobiletelephonesthatexclusivelyusedafrequencybandinaparticulararea.Thesetelephoneshadsevereproblemswithcongestionandcallcompletion.Ifonecustomerwasusingaparticularfrequencyinageographicarea,noothercustomercouldmakeacallonthatsamefrequency.Further,thenumberoffrequenciesallocatedbytheFCCintheU.S.tomobiletelephoneserviceswassmall,limitingthenumberofsimultaneouscalls.Similarsystems,knownasA-NetzandB-NetzweredevelopedinGermany.

Theintroductionofcellulartechnologygreatlyexpandedtheefficiencyoffrequencyuseofmobilephones.Ratherthanexclusivelyallocatingabandoffrequencytoonetelephonecallinalargegeographicarea,acelltelephonebreaksdownageographicareaintosmallareasorcells.Differentusersindifferent（non-adjacent）cellsareabletousethesamefrequencyforacallwithoutinterference.

Firstgenerationcellularmobiletelephonesdevelopedaroundtheworldusingdifferent,incompatibleanaloguetechnologies.Forexample,inthe1980sintheU.S.therewastheAdvancedMobilePhoneSystem（AMPS）,theU.K.hadtheTotalAccessCommunicationsSystem（TACS）,GermanydevelopedC-Netz,whileScandinaviadevelopedtheNordicMobileTelephone（NMT）system.Theresultwasawiderangeoflargelyincompatiblesystems,particularlyinEurope,althoughthesingleAMPSsystemwasusedthroughouttheU.S.

Secondgeneration（2G）mobiletelephonesuseddigitaltechnology.TheadoptionofsecondgenerationtechnologydifferedsubstantiallybetweentheUnitedStatesandEuropeandreversestheearlieranaloguemobileexperience.InEurope,acommonstandardwasadopted,partlyduetogovernmentintervention.

GroupeSpecialeMobile（GSM）wasfirstdevelopedinthe1