Nrog rau txoj kev loj hlob ntawm kev sib txuas lus ntawm kev sib txuas lus mus rau broadband thiab kev txav mus los, lub optical fiber wireless kev sib txuas lus system (ROF) integrates optical fiber kev sib txuas lus thiab wireless kev sib txuas lus, muab tag nrho cov kev ua si rau qhov zoo ntawm broadband thiab tiv thaiv kev cuam tshuam ntawm optical fiber kab, nrog rau kev sib txuas lus wireless. .Cov yam ntxwv yooj yim thiab hloov tau raws li tib neeg qhov kev thov rau broadband.ROF thev naus laus zis thaum ntxov tau mob siab rau muab cov kev pabcuam xa xov hluav taws xob siab, xws li millimeter wave optical fiber kis.Nrog rau kev txhim kho thiab kev loj hlob ntawm ROF thev naus laus zis, tib neeg pib kawm hybrid wired thiab wireless kis tau tus mob sib txuas, uas yog, optical fiber wireless kev sib txuas lus (ROF) cov tshuab uas muab cov kev pabcuam xaim thiab wireless tib lub sijhawm.Nrog rau kev loj hlob sai ntawm kev sib txuas lus hauv xov tooj cua, qhov tsis txaus ntawm cov peev txheej spectrum tau dhau los ua qhov tseem ceeb.Yuav ua li cas txhim kho kev siv spectrum nyob rau hauv cov xwm txheej ntawm cov peev txheej wireless tsawg los daws qhov tsis sib xws ntawm cov khoom siv thiab kev xav tau ntawm cov peev txheej spectrum tau dhau los ua teeb meem los daws hauv kev sib txuas lus.Kev paub xov tooj cua (CR) yog ib qho kev txawj ntse spectrum sib qhia technology.Nws tuaj yeem txhim kho kev siv cov peev txheej spectrum zoo los ntawm "kev siv thib ob" ntawm kev tso cai spectrum, thiab tau dhau los ua qhov kev tshawb fawb hotspot hauv kev sib txuas lus.Hauv 802.11 wireless hauv cheeb tsam network [1], 802.16 lub nroog cheeb tsam network [2] thiab 3G mobile kev sib txuas lus network [3] tau pib kawm txog kev siv xov tooj cua kev txawj ntse los txhim kho lub peev xwm ntawm cov kab ke, thiab pib kawm txog daim ntawv thov ntawm ROF thev naus laus zis kom ua tiav kev sib xyaw ua ke ntawm cov cim lag luam sib txawv [4].Kev paub txog xov tooj cua-raws li optical fiber wireless kev sib txuas lus uas xa cov xov tooj cua thiab wireless teeb liab yog kev txhim kho ntawm kev sib txuas lus yav tom ntej.Lub hybrid kis tau tus mob ROF system raws li kev txawj ntse xov tooj cua technology ntsib ntau yam kev cov nyom tshiab, xws li network architecture tsim, txheej raws tu qauv tsim, tiam ntawm wired thiab wireless modulated signals raws li ntau yam kev pab cuam, network tswj, thiab kev txheeb xyuas ntawm modulated signals.
1 Kev txawj ntse xov tooj cua technology
Kev paub xov tooj cua yog ib txoj hauv kev zoo los daws qhov tsis muaj spectrum thiab kev siv tsis zoo ntawm spectrum.Kev paub xov tooj cua yog ib qho kev sib txuas lus ntse wireless.Nws paub txog kev siv spectrum ntawm ib puag ncig ib puag ncig thiab kho nws tus kheej tsis hloov pauv los ntawm kev kawm kom ua tiav kev siv tau zoo.Spectrum cov peev txheej thiab kev sib txuas lus txhim khu kev qha.Kev siv xov tooj cua kev txawj ntse yog ib qho tseem ceeb thev naus laus zis kom paub txog cov peev txheej spectrum los ntawm kev faib khoom ruaj khov mus rau kev faib tawm dynamic.Hauv xov tooj cua kev txawj ntse, txhawm rau tiv thaiv tus neeg siv tau tso cai (lossis dhau los ua tus tswv siv) los ntawm kev cuam tshuam los ntawm tus neeg siv qhev (lossis CR tus neeg siv), txoj haujlwm ntawm spectrum sensing yog kom pom tias tus neeg siv tau tso cai muaj nyob.Cov neeg siv xov tooj cua paub siv tau ib ntus siv cov zaus band thaum nws raug saib xyuas tias cov zaus band siv los ntawm cov neeg siv tau tso cai tsis raug siv.Thaum nws raug saib xyuas tias qhov zaus ntawm cov neeg siv tau tso cai siv, CR cov neeg siv tau tso tawm cov channel rau tus neeg siv tau tso cai, yog li ua kom ntseeg tau tias tus neeg siv CR tsis cuam tshuam nrog tus neeg siv tau tso cai.Yog li ntawd, kev txawj ntse wireless kev sib txuas lus network muaj cov yam ntxwv tseem ceeb hauv qab no: (1) Tus neeg siv thawj zaug muaj qhov tseem ceeb rau kev nkag mus rau cov channel.Ntawm qhov tod tes, thaum tus neeg siv tau tso cai tsis nyob hauv lub channel, tus neeg siv thib ob muaj lub sijhawm nkag mus rau cov channel tsis ua haujlwm;Thaum tus neeg siv thawj zaug rov tshwm sim, tus neeg siv thib ob yuav tsum tawm ntawm cov channel hauv lub sijhawm thiab xa cov channel rov qab rau thawj tus neeg siv.Ntawm qhov tod tes, thaum tus tswv siv nyob hauv lub channel, cov neeg siv qhev tuaj yeem nkag mus rau cov channel yam tsis muaj kev cuam tshuam rau kev pabcuam zoo ntawm tus tswv siv.(2) CR kev sib txuas lus davhlau ya nyob twg muaj lub luag haujlwm ntawm kev nkag siab, kev tswj hwm thiab kev hloov kho.Ua ntej, CR kev sib txuas lus lub davhlau ya nyob twg tuaj yeem pom qhov zaus spectrum thiab channel ib puag ncig hauv qhov chaw ua haujlwm, thiab txiav txim siab sib koom thiab faib cov peev txheej spectrum raws li qee txoj cai raws li kev tshawb pom;ntawm qhov tod tes, CR kev sib txuas lus davhlau ya nyob twg muaj peev xwm los kho cov haujlwm tsis ua haujlwm hauv online, xws li kev hloov pauv cov kev sib kis xws li cov neeg nqa khoom zaus thiab cov qauv kev hloov pauv tuaj yeem hloov pauv hauv ib puag ncig.Hauv kev paub txog kev sib txuas lus wireless network, spectrum sensing yog ib qho tseem ceeb thev naus laus zis.Feem ntau siv spectrum sensing algorithms muaj xws li kev tshawb nrhiav lub zog, kev sib tw lim kom pom, thiab cyclostationary feature nrhiav txoj hauv kev.Cov txheej txheem no muaj lawv tus kheej qhov zoo thiab qhov tsis zoo.Kev ua tau zoo ntawm cov algorithms no nyob ntawm cov ntaub ntawv ua ntej tau txais.Cov spectrum sensing algorithms uas twb muaj lawm yog: sib phim lim, lub zog ntes thiab feature ntes txoj kev.Cov lim uas sib phim tsuas yog siv tau thaum lub teeb liab tseem ceeb paub.Lub zog ntsuas hluav taws xob tuaj yeem siv rau qhov xwm txheej uas lub teeb liab tseem ceeb tsis paub, tab sis nws qhov kev ua haujlwm tsis zoo thaum siv lub sijhawm luv luv.Vim hais tias lub tswv yim tseem ceeb ntawm lub feature detector yog siv lub cyclostationarity ntawm lub teeb liab mus ntes los ntawm lub spectral correlation muaj nuj nqi.Lub suab nrov yog lub teeb liab dav nyob ruaj khov thiab tsis muaj kev sib raug zoo, thaum lub teeb liab modulated yog correlated thiab cyclostationary.Yog li ntawd, spectral correlation muaj nuj nqi tuaj yeem paub qhov txawv ntawm lub zog ntawm lub suab nrov thiab lub zog ntawm cov teeb liab modulated.Nyob rau hauv ib puag ncig uas tsis muaj suab nrov, qhov kev ua tau zoo ntawm cov cuab yeej ntes tau zoo dua li ntawm lub zog ntes.Qhov kev ua tau zoo ntawm cov cuab yeej ntes tau nyob rau hauv qhov tsis tshua muaj teeb liab-rau-lub suab sib piv yog txwv, muaj kev suav siab nyuaj, thiab yuav tsum tau saib xyuas lub sijhawm ntev.Qhov no txo cov ntaub ntawv dhau los ntawm CR system.Nrog rau txoj kev loj hlob ntawm wireless kev sib txuas lus thev naus laus zis, spectrum cov peev txheej tau dhau los ua nruj dua.Vim tias CR thev naus laus zis tuaj yeem daws qhov teeb meem no, CR thev naus laus zis tau them nyiaj rau hauv kev sib txuas lus wireless, thiab ntau cov qauv kev sib txuas lus wireless tau qhia txog kev txawj ntse hauv xov tooj cua.Xws li IEEE 802.11, IEEE 802.22 thiab IEEE 802.16h.Nyob rau hauv daim ntawv cog lus 802.16h, muaj cov ntsiab lus tseem ceeb ntawm dynamic spectrum xaiv los pab txhawb WiMAX txoj kev siv xov tooj cua thiab TV zaus bands, thiab nws lub hauv paus yog spectrum sensing technology.Hauv IEEE 802.11h tus qauv thoob ntiaj teb rau wireless hauv cheeb tsam hauv cheeb tsam, ob lub ntsiab lus tseem ceeb tau qhia: dynamic spectrum xaiv (DFS) thiab xa hluav taws xob tswj (TPC), thiab kev txawj ntse xov tooj cua tau siv rau wireless hauv cheeb tsam network.Nyob rau hauv tus qauv 802.11y, orthogonal zaus division multiplexing (OFDM) thev naus laus zis yog siv los muab ntau hom kev xaiv bandwidth, uas tuaj yeem ua tiav kev hloov pauv ceev ceev.WLAN (wireless hauv cheeb tsam network) cov tshuab tuaj yeem ua kom zoo dua ntawm cov yam ntxwv ntawm OFDM kom tsis txhob muaj kev zam los ntawm kev kho bandwidth thiab xa cov hluav taws xob tsis zoo.Kev cuam tshuam nrog lwm tus neeg siv ua haujlwm hauv qhov zaus band.Vim hais tias lub optical fiber wireless system muaj qhov zoo ntawm kev sib txuas lus fiber ntau bandwidth thiab cov yam ntxwv hloov tau ntawm kev sib txuas lus wireless, nws tau siv dav.Nyob rau hauv xyoo tas los no, kev sib kis ntawm xov tooj cua zaus paub WLAN cov teeb liab hauv optical fiber tau nyiam mloog.Tus sau cov ntaub ntawv [5-6] tau hais tias ROF system Cognitive radio signals raug xa mus nyob rau hauv cov qauv tsim, thiab simulation thwmsim qhia tias kev ua haujlwm hauv network tau txhim kho.
2 ROF-raws li hybrid optical fiber wireless kis tau tus mob system architecture
Txhawm rau ua kom tau raws li cov kev xav tau ntawm cov kev pabcuam multimedia rau kev xa cov yeeb yaj kiab, qhov tshwm sim fiber ntau-rau-lub-tsev (FFTH) yuav dhau los ua qhov kawg broadband nkag tshuab, thiab passive optical network (PON) tau dhau los ua qhov tseem ceeb ntawm kev mloog thaum nws los txog. tawm.Txij li thaum cov khoom siv hauv PON network yog cov khoom siv passive, lawv tsis xav tau lub zog hluav taws xob, tuaj yeem tiv thaiv kev cuam tshuam ntawm sab nraud electromagnetic cuam tshuam thiab xob laim, tuaj yeem ua tiav cov kev pabcuam pob tshab, thiab muaj kev ntseeg siab.PON tes hauj lwm feem ntau suav nrog lub sij hawm faib multiplexing passive optical networks (TDM-PON) thiab wavelength division multiplexing passive optical networks (WDM-PON).Piv nrog TDM-PON, WDM-PON muaj cov yam ntxwv ntawm cov neeg siv tshwj xeeb bandwidth thiab kev ruaj ntseg siab, dhau los ua qhov muaj peev xwm tshaj plaws kho qhov muag nkag mus rau yav tom ntej.Daim duab 1 qhia txog daim duab thaiv ntawm WDM-PON system.