脈沖位置調(diào)制光譜切片傳輸中英文翻譯

1、本文格式為Word版，下載可任意編輯 脈沖位置調(diào)制光譜切片傳輸中英文翻譯 Pulse position modulation for spectrum-sliced transmission Proponents of ultra-wideband (UWB) technology promise todeliver large amounts of data with very lowpower spectral density. The ultra-wideband radio concept is very attractive as it promises to open large

2、amounts of spectrum to a variety of user sand at the same time it claims little interfere nice between users. Unlike conven tional wire less communications systems that are carrier based,UWB-based communications is baseband .It use sase ries of short pulses that spread thee nergy of thes ignal from

3、near DC to a few GHz. One typical technique is to as sign a window in time and shif the position of the pulse with in that window. This is classical pulse position modulation. With band width restrictions effectively removed, UWB promises to speed upwire less data trans ferrates. Some pub lished wor

4、k has addressed the issue of how many users can the UWB channel support23.This work considered one type of capacity-the capacity interms on the number of users. The capacity was derived from signal-to-no is eratio (SNR)consi derations. Acer tain SNR is required to achieve a specified biterr or proba

5、bility(BEP).The no is eflo or raises with the number of users. A more fund amentalty peofcapacity is the well known Shannon capacity in bits/s. Our go a list odevelopanunderstanding of thero leofvar iouspara me terso nthe Shannoncapac it yo fUW B commun ications.The well known Shannon!s form ulC=Wlo

6、g(l+SNR),where SNR is the 2 signal-to-noiseratio and Wist hechannel band width, predicts the channel capacity Cfor an additive white Gaussiannoise (AWGN) channel with continuousal uedinput sand outputs. This express iondoesnot apply to communications with PPM signals. PP mis a modul ation with discr

7、et e-valuedi nputsan dcon tinu ous-val uedoutput s.Further more,P Pmsignalsa reorthogo nal,whichi mposesa naddition alconst raintont hecapacityc alcul ations. Newcapacitycal culations arerequi red,which htakeint oaccountthes econstrain ts.PPMcap acitywas studiedint hecontex tofwireles sinfra reda nd

8、 optic alcha nnels4.The capacityo fPPM modul ationservesas thestarti ngpointtow hichUWB- speci ficcons traintsar eadded.Thec onstraints arethepow erspectr umdensityl imitation underF CCPar t15r ulesand thes preadingra tiocons train t.Sincegiga hertzunoc cupiedslice sofbandwidth arenotavailable atmic

9、 rowavef requencies,underFCCreg ulations,U Wbradiomust betreat eda ss p uriousint erferenc etoallother communicat I onsystems. The FCC is currently assessing whether to allow UWB emission son an unlicensed basis. Un in tend edout of bande missionsa regov ernedb yFCCPart15ru les.Inthisp aper,weassume

10、tha tUWBtransmiss ionscomplywi ththisFCCrul e.Thespreading ratioconst raintisinte ndedtosatisfyi nterferences uppressionre quirements5 6.Thispape risorgani zedasfollows. Sectionintrodu cesthesi gnalmodel.The linkbudgetcalculati onforUWBunde rFCCPart 15rules isdevel opedinsectio n.AnalysisofU WBM-ary

11、 PPM capacity is carried out insection IV.Finally,conclusionsarep rovidedinse ctionV.SIGNALMODEL Considera single-user UWB pulse position modulated communication ssystem. The M-ary PPM signal setis S1(t),S2(t),SM(t), where Sm(t), (mM) Canbewrit tenas: (t)=p(t-j). Inthisexpr ession, p(t)is the UWB pu

12、ls eofduration Tp (normalizedsuchthat), Episthee nergyperp ulse,Tis the puls erepetition time, thesequencecj frepresents thet imehoppi ngcode,withcj Tanadditional times hiftto the jthpul seof the ccomm unication burst. Fora fixedT ,the symbolrate R=1/(N,Tf) determinesN, the fnumbero fpulsestha tform

13、asymbol. The symbolduration is then T,=N,Tf. The parameter is the additional times hift corresponding to the pulseposition modulation, mwith T=0, T100. Theband widthrequ irementso fM-aryPPMca nbeestim atedfromth eLandau- Pollak theorem8, which hstates that the band width of as ignalt imelimitedto T,

14、(symboldu ration)andof dimensionali tyMisappro ximatelyB = .Thisval uecanbeint erpretedasthe minimumbandw idthrequire dtotransmi tuncodedM -aryPPM.UWB using Mary PPM is spread spect rumin thesense that theUWBbandwidthWB.From (2),W=c/Tp,andT,=NT,the spread spectrumcondition WsfBismet for aspread ingr

15、atio=M.Themot ivationfor spreadspe ctrumUWBPPMis twofold:(1)atta inspecifie dleveloftr ansmittedpower subjecttopower densityconstra intssetb yFCCPart1 5regulat ion,(2)attai nspecif iedlev elofresist anceto othe remissi onsintheb and(jamresistance).The transmitted powerre quirementis deter m ine dbyt

16、hedis tanceb etweenthe transmitte randthere ceiver.Thi sissueisdi scusse dinthenextse ction.Jamre sistance of U WB isanalyzed . UWB LINKB UDGET InMay 2000,the FCC published aNot ice of Proposed RuleMaking(NPRM) to include UWB emissionsunder Part15 rule.In the notice,the FCC tentatively proposed that

17、 UWB emissions above 2GHz,shoul dcomply with the existing Part 15limits,and that UWBemissionsbelow 2GHz should beat tenuate datleast12dB below the Part 15 limits.Inthissec tionofthe paper,weassess the range of communication using UWB by carrying out linkbudget calculation sassuming compliance with F

18、CC Part 15 rules.The commonlyused link budgete quation canbeexpressedas:,3 where Ptistran smitted UWB power,Pisreceived power at distanced.Gtand Garean tennagain sfor transmitt erandrec eiverre spectiv ely,bot hassumed as0dB.Thee xpression ofpathlo ssPLtobeus edin(3)depen dsonthepr opagation model.C

19、urrently,there is nocommonly accepted model for UWB.In9,it was shown that in an environment dense with obscuring objects,there ceivedsignalstreng thapproxi mately-4followsd-dependency with distanced.At short range suchasseveral meters,the-2trans missioni sdominatedby the direct signal path(ddependen

20、cy).Thegeneral UWB path lossmode lcanbe written:PL(dB)=10log ,where nis the power at tenuation exponent and Xis the wave leng thcorre sponding to the working frequ encyfc.The working frequency is the center of band width,andit is assumed to be2.5GHz for a UWB signal of bandwidth W=1Ghzoccupying the

21、frequency range from2GHzto3GHz.Acco rding to FCC Part 15 rules, em is sionsab ove900Mhzshallnot exceed field strength levels of E=50 0micro-volts/meter/Mhz measure data distanceof3elation ship between Pta nd Ecand epen donanu mberofaddi tionalfac tors,acom monly-usede xpressiontoap proxim atetheirre

22、 lationship is10:.5From(5)andafterso mecalculat ions,weobtain thetransmitte dpowercons traintf oraUWBtra nsmission overa1GHzb andwidthi s.6Toproper lydetectan ddecodethere ceive dsigna l,there ceiverreq uiresa certain minim umS NR.Ifw econs ideronlyt hermalnoisea stheprimar ysourceo fin terfer ence,

23、therece ivednois epowerNca nbecalcu latedf rom:N=Ktwf,7whe rekistheBo ltzmann! sconstan1.3 8xJoules /K,Tisth eroomtem perature( typicallytake nas300K) ,andFisth enoisefigure (optimisti cally)assum edF=5dB.F oraUWBrec eiverwithband widthW=1GHz ,thecalcul atednois eflooris- 89dBm.Unl ikeotherc ommunic

24、a tionsmetho ds,which transmitc ontinuouss ignals(100%dutycycle)and thepeakpower equalsthea veragepower,with UWB,the pulseduration Tpismuc hshorter thanthepul serepeti tiontim eTf.Thesp readingr atioP,which isdefined asth eratioTf/Tp,I stypicallyl argerthan100,resu ltinginapu lsepeakpo werhundred so

25、ftimelar gerthant heaverage power.TheSNRp ersymbolatt heinputofth ecorrelation receiverisex pressed=2E,/No,wher eE,istheener gypersymbol andNoisthenoi sepowerdensity.Thes ymbolSNRisrelat edtotheaver ageSNRasfollows.Theav eragesigna lpowerisgiv enbyE,/T,Wit hW=and= ,weha vethefollowing expressi onfor

26、theav erageSNRatthe receiver:SNR= ,8wher eg=2cN.Thepar amete rgplayst heroleo fproces sing gain(ratioofthesymbolsSN Ravail ableatdet ectiontot heaverageSNR atther eceiv erinput).Itfollow sthatthere quiredsen sitivity ofthere ceiveri sgivenby:S=N+F+SN ,9whereSNR is there quired signal tonoisera tioan dallquant itiesa reexp ress edindBmD ordB.Inord ertogetthe desiredperf ormancea tadistanced, theminimum receivedsig nalpowershou ldbeequalorl argertha nthesensiti vity,viz.,d S.Fro