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Chapter11.Incaseofanaccident,thereisahighchanceofgettinglost.Thetransportationcostisveryhigheachtime.However,iftheinfrastructureissetonce,itwillbeveryeasytouseitrepeatedly.Timeforwirelesstransmissionisnegligibleassignalstravelatthespeedoflight.2.Advantagesofburstydatacommunication(a)Pulsesaremadeverynarrow,somultipathsareresolvable(b)Thetransmissiondeviceneedstobeswitchedonforlesstime.Disadvantages(a)Bandwidthrequiredisveryhigh(b)Peaktransmitpowercanbeveryhigh.3.Pb=10¡1212°=10¡12°=10122=5£1011(veryhigh)4.Geo:35,786Kmaboveearth)RTT=2£35786£103c=0:2386sMeo:8,000-20,000Kmaboveearth)RTT=2£8000£103c=0:0533sLeo:500-2,000Kmaboveearth)RTT=2£500£103c=0:0033sOnlyLeosatellitesasdelay=3:3ms30ms5.6.optimumno.ofdatauser=doptimumno.ofvoiceuser=vThreedi®erentcases:Case1:d=0,v=6)revenue=60:80:2=0:96Case2:d=1,v=3revenue=[prob.ofhavingonedatauser]£(revenueofhavingonedatauser)+[prob.ofhavingtwodatauser]£(revenueofhavingtwodatauser)+[prob.ofhavingonevoiceuser]£(revenueofhavingonevoiceuser)+[prob.ofhavingtwovoiceuser]£(revenueofhavingtwovoiceuser)+[prob.ofhavingthreeormorevoiceuser]£(revenueinthiscase))0:52µ21¶£$1+0:52£$1+µ61¶0:8£0:25£$0:2+µ62¶0:82£0:24£$0:4+·1¡µ61¶0:8£0:25£$0:2¡µ62¶0:82£0:24£$0:4¸£$0:6)$1:35Case3:d=2,v=0revenue=2£0:5=$1Sothebestcaseiscase2,whichistoallocate60kHztodataand60kHztovoice.7.8.1.Hand-o®becomesabigproblem.2.Inter-cellinterferenceisveryhighandshouldbemitigatedtogetreasonableSINR.3.Infrastructurecostisanotherproblem.9.Smallerthereusedistance,largerthenumberofuserswhocanusethesamesystemresourceandsocapacity(datarateperunitbandwidth)increases.10.(a)100cells,100users/cell)10,000users(b)100users/cell)2500cellsrequired100km2Area=cell=2500cells)Areacell=:04km2(c)FromRappaportoriterationofformula,wegetthat100channelscell)89channelscell@Pb=:02Eachsubscribergenerates130ofanErlangoftra±c.Thus,eachcellcansupport30£89=2670subscribersMacrocell:2670£100)267;000subscribersMicrocell:6,675,000subscribers(d)Macrocell:$50MMicrocell:$1.25B(e)Macrocell:$13.35M/month)3.75monthsapprox4monthstorecoopMicrocell:$333.75M/month)3.75monthsapprox4monthstorecoop11.OneCDPDline:19.2KbpsaverageWimax»40Mbps)numberofCDPDlines»2£103Chapter21.Pr=Pt·pGl¸4¼d¸2¸=c=fc=0:0610¡3=Pt·¸4¼10¸2)Pt=4:39KW10¡3=Pt·¸4¼100¸2)Pt=438:65KWAttenuationisveryhighforhighfrequencies2.d=100mht=10mhr=2mdelayspread=¿=x+x0¡lc=1:33£3.¢Á=2¼(x0+x¡l)¸x0+x¡l=p(ht+hr)2+d2¡p(ht¡hr)2+d2=d24sµht+hrd¶2+1¡sµht¡hrd¶2+135dÀht;hr;weneedtokeeponly¯rstorderterms»d8:2412sµht+hrd¶2+135¡2412sµht¡hrd¶2+1359=;=2(ht+hr)d¢Á»2¼¸2(ht+hr)d4.Signalnullsoccurwhen¢Á=(2n+1)¼2¼(x0+x¡l)¸=(2n+1)¼2¼¸hp(ht+hr)2+d2¡p(ht¡hr)2+d2i=¼(2n+1)p(ht+hr)2+d2¡p(ht¡hr)2+d2=¸2(2n+1)Letm=(2n+1)p(ht+hr)2+d2=m¸2+p(ht¡hr)2+d2squarebothsides(ht+hr)2+d2=m2¸24+(ht¡hr)2+d2+m¸p(ht¡hr)2+d2x=(ht+hr)2;y=(ht¡hr)2;x¡y=4hthrx=m2¸24+y+m¸py+d2)d=s·1m¸µx¡m2¸24¡y¶¸2¡yd=sµ4hthr(2n+1)¸¡(2n+1)¸4¶2¡(ht¡hr)2;n2Z5.ht=20mhr=3mfc=2GHz¸=cfc=0:15dc=4hthr¸=1600m=1:6KmThisisagoodradiusforsuburbancellradiusasuserdensityislowsocellscanbekeptfairlylarge.Also,shadowingislessduetofewerobstacles.6.ThinkofthebuildingasaplaneinR3ThelengthofthenormaltothebuildingfromthetopofTxantenna=htThelengthofthenormaltothebuildingfromthetopofRxantenna=hrInthissituationthe2raymodelissameasthatanalyzedinthebook.7.h(t)=®1±(t¡¿)+®2±(t¡(¿+0:22¹s))Gr=Gl=1ht=hr=8mfc=900MHz;¸=c=fc=1=3R=¡1delayspread=x+x0¡lc=0:022£10¡6s)2q82+¡d2¢2¡dc=0:022£10¡6s)d=16:1m)¿=dc=53:67ns®1=µ¸4¼pGll¶2=2:71£10¡6®2=µ¸4¼pRGrx+x0¶2=1:37£10¡68.Aprogramtoplotthe¯guresisshownbelow.Thepowerversusdistancecurvesandaplotofthephasedi®erencebetweenthetwopathsisshownonthefollowingpage.FromtheplotsitcanbeseenthatasGr(gainofre°ectedpath)isdecreased,theasymptoticbehaviorofPrtendstowardd¡2fromd¡4,whichmakessensesincethee®ectofre°ectedpathisreducedanditismorelikehavingonlyaLOSpath.Alsothevariationofpowerbeforeandarounddcisreducedbecausethestrengthofthere°ectedpathdecreasesasGrdecreases.Alsonotethatthethereceivedpoweractuallyincreaseswithdistanceuptosomepoint.Thisisbecauseforverysmalldistances(i.e.d=1),there°ectedpathisapproximatelytwotimestheLOSpath,makingthephasedi®erenceverysmall.SinceR=-1,thiscausesthetwopathstonearlycanceleachotherout.Whenthephasedi®erencebecomes180degrees,the¯rstlocalmaximaisachieved.Additionally,thelengthsofbothpathsareinitiallydominatedbythedi®erencebetweentheantennaheights(whichis35meters).Thus,thepowersofbothpathsareroughlyconstantforsmallvaluesofd,andthedominantfactoristhephasedi®erencebetweenthepaths.clearall;closeall;ht=50;hr=15;f=900e6;c=3e8;lambda=c/f;GR=[1,.316,.1,.01];Gl=1;R=-1;counter=1;figure(1);d=[1:1:100000];l=(d.^2+(ht-hr)^2).^.5;r=(d.^2+(ht+hr)^2).^.5;phd=2*pi/lambda*(r-1);dc=4*ht*hr/lambda;dnew=[dc:1:100000];forcounter=1:1:4,Gr=GR(counter);Vec=Gl./l+R*Gr./r.*exp(phd*sqrt(-1));Pr=(lambda/4/pi)^2*(abs(Vec)).^2;subplot(2,2,counter);plot(10*log10(d),10*log10(Pr)-10*log10(Pr(1)));holdon;plot(10*log10(dnew),-20*log10(dnew));plot(10*log10(dnew),-40*log10(dnew));endholdoff0204060−150−100−5005010*log10(Pr)10*log10(d)Gr=10204060−150−100−5005010*log10(Pr)10*log10(d)Gr=.3160204060−150−100