Ngokuthuthuka kwamanethiwekhi okuxhumana abheke ku-broadband kanye nokuhamba, i-optical fibre wireless communication system (ROF) ihlanganisa ukuxhumana kwefiber optical kanye nokuxhumana okungenantambo, inikeze ukudlala okugcwele okuhle kwe-broadband kanye nokuphikisana nokuphazanyiswa kwemigqa ye-fiber optical, kanye nokuxhumana okungenantambo. .Izici ezilula nezivumelana nezimo zihlangabezana nesidingo sabantu se-broadband.Ubuchwepheshe bokuqala be-ROF bebunikezelwe ngokuyinhloko ekuhlinzekeni ngezinsizakalo zokudlulisa okungenantambo zemvamisa ephezulu, njenge-millimeter wave optical fiber transmission.Ngokuthuthuka nokuvuthwa kobuchwepheshe be-ROF, abantu baqala ukufunda amanethiwekhi e-hybrid anezintambo nangenawaya, okungukuthi, izinhlelo ze-optical fibre wireless communication (ROF) ezihlinzeka ngezinsizakalo ezinezintambo nezingenantambo ngesikhathi esisodwa.Ngokuthuthuka okusheshayo kwezokuxhumana ngomsakazo, ukushoda kwezinsiza ze-spectrum sekugqame kakhulu.Indlela yokuthuthukisa ukusetshenziswa kwe-spectrum ngaphansi kwesimo sezinsiza ezilinganiselwe ezingenazintambo ukuze kuncishiswe ukungqubuzana phakathi kokunikezwa kanye nokufunwa kwezinsiza ze-spectrum sekuyinkinga okufanele ixazululwe emkhakheni wezokuxhumana.Irediyo ye-Cognitive (CR) ubuchwepheshe bokwabelana nge-spectrum obuhlakaniphile.Ingathuthukisa ngempumelelo ukusetshenziswa kwezinsiza ze-spectrum ngokusebenzisa "ukusetshenziswa kwesibili" kwe-spectrum egunyaziwe, futhi isiphenduke indawo yocwaningo emkhakheni wezokuxhumana.Kunethiwekhi yendawo engenantambo ye-802.11 [1], inethiwekhi yendawo yedolobha engu-802.16 [2] kanye nenethiwekhi yezokuxhumana yeselula ye-3G [3] sebeqalile ukutadisha ukusetshenziswa kobuchwepheshe bomsakazo wokuqonda ukuthuthukisa umthamo wesistimu, futhi baqala ukutadisha ukusetshenziswa Ubuchwepheshe be-ROF ukuze kuzuzwe ukudluliswa okuxubile kwezimpawu zebhizinisi ezihlukene[4].Amanethiwekhi okuxhumana angenantambo asuselwa kumsakazo we-fiber optical adlulisa amasignali anezintambo nangenawaya awumkhuba wokuthuthukiswa kwamanethiwekhi okuxhumana angomuso.I-hybrid transmission system ye-ROF esekelwe kubuchwepheshe berediyo bokuqonda ibhekana nezinselele eziningi ezintsha, njengokwakheka kwenethiwekhi yezakhiwo, ukwakheka kwephrothokholi yongqimba, ukukhiqizwa kwamasiginali ashintshiwe anentambo nangenantambo ngokusekelwe kumasevisi amaningi, ukuphathwa kwenethiwekhi, nokuhlonza amasignali ashintshiwe.
1 Ubuchwepheshe bomsakazo wokuqonda
Umsakazo wokuqonda uyindlela esebenzayo yokuxazulula ukushoda kwe-spectrum kanye nokusetshenziswa kancane kwe-spectrum.Umsakazo wokuqonda wuhlelo lokuxhumana olungenantambo oluhlakaniphile.Izwa ukusetshenziswa kwe-spectrum yendawo ezungezile futhi ilungise amapharamitha ayo ngokuguquguquka ngokufunda ukuze izuze ukusetshenziswa ngempumelelo.Izinsiza ze-Spectrum nokuxhumana okuthembekile.Ukusetshenziswa komsakazo wokuqonda kuwubuchwepheshe obuyinhloko bokubona insiza ye-spectrum kusukela ekwabiweni okungaguquki kuya ekwabiweni okuguquguqukayo.Kuhlelo lwerediyo yengqondo, ukuze kuvikelwe umsebenzisi ogunyaziwe (noma abe umsebenzisi oyinhloko) ekuphazamisekeni komsebenzisi oyisigqila (noma umsebenzisi we-CR), umsebenzi wokuzwa kwe-spectrum ukubona ukuthi umsebenzisi ogunyaziwe ukhona yini.Abasebenzisi bomsakazo abasebenzisa ingqondo bangasebenzisa ibhendi yefrikhwensi okwesikhashana uma iqashwe ukuthi ibhendi yefrikhwensi esetshenziswa umsebenzisi ogunyaziwe ayisetshenziswa.Uma kuqashelwa ukuthi ibhendi yemvamisa yomsebenzisi ogunyaziwe iyasebenza, umsebenzisi we-CR udedela isiteshi kumsebenzisi ogunyaziwe, ngaleyo ndlela aqinisekise ukuthi umsebenzisi we-CR akaphazamisi umsebenzisi ogunyaziwe.Ngakho-ke, inethiwekhi yokuxhumana okungenantambo inezici ezilandelayo ezibalulekile: (1) Umsebenzisi oyinhloko unokubaluleka okuphelele kokufinyelela esiteshini.Ngakolunye uhlangothi, lapho umsebenzisi ogunyaziwe engahlali esiteshini, umsebenzisi wesibili unethuba lokufinyelela isiteshi esingasebenzi;lapho umsebenzisi oyinhloko ephinda evela, umsebenzisi wesibili kufanele aphume esiteshini ngesikhathi futhi abuyisele isiteshi kumsebenzisi oyinhloko.Ngakolunye uhlangothi, lapho umsebenzisi oyinhloko ethatha isiteshi, umsebenzisi wesigqila angangena esiteshini ngaphandle kokuphazamisa ikhwalithi yesevisi yomsebenzisi oyinhloko.(2) Indawo yokuxhumana ye-CR inemisebenzi yokubona, yokuphatha kanye nokulungisa.Okokuqala, indawo yokuxhumana ye-CR ingakwazi ukubona i-spectrum ye-frequency kanye nemvelo yesiteshi endaweni yokusebenza, futhi inqume ukwabelana nokwabiwa kwezinsiza ze-spectrum ngokuvumelana nemithetho ethile ngokuya ngemiphumela yokutholwa;ngakolunye uhlangothi, i-terminal yezokuxhumana ye-CR inamandla okulungisa imingcele yokusebenza ku-inthanethi, njengokushintsha Imingcele yokudlulisela efana nemvamisa yenkampani yenethiwekhi kanye nendlela yokushintshashintsha ingakwazi ukuzivumelanisa nezinguquko endaweni.Kumanethiwekhi okuxhumana angenantambo engqondo, ukuzwa kwe-spectrum kuwubuchwepheshe obubalulekile.Ama-algorithms avame ukusetshenziswa enzwa ye-spectrum ahlanganisa ukutholwa kwamandla, ukutholwa kwesihlungi esifanayo, nezindlela zokuthola izici ze-cyclostationary.Lezi zindlela zinezinzuzo zazo kanye nokubi.Ukusebenza kwalawa ma-algorithms kuncike olwazini lwangaphambili olutholiwe.Ama-algorithms akhona okuzwa i-spectrum yilawa: isihlungi esifanisiwe, isitholi samandla kanye nezindlela zomtshina wesici.Isihlungi esifanisiwe singasetshenziswa kuphela uma isignali eyinhloko yaziwa.Umtshina wamandla ungasetshenziswa esimweni lapho isignali eyinhloko ingaziwa, kodwa ukusebenza kwayo kuyawohloka lapho kusetshenziswa isikhathi esifushane sokuzwa.Ngoba umqondo oyinhloko womtshina wesici ukusebenzisa i-cyclostationarity yesiginali ukuthola ngomsebenzi wokuhlanganisa i-spectral.Umsindo isignali emile ebanzi futhi ayinakho ukuhlobana, kuyilapho isignali eshintshiwe ihlotshaniswa ne-cyclostationary.Ngakho-ke, umsebenzi we-spectral correlation ungahlukanisa amandla omsindo namandla esignali eshintshiwe.Endaweni enomsindo ongaqinisekile, ukusebenza komtshina wesici kungcono kunomtshina wamandla.Ukusebenza komtshina wesici ngaphansi kwesilinganiso esiphansi sesignali-kuya-kumsindo kunqunyelwe, kunobunzima bekhompyutha obuphezulu, futhi kudinga isikhathi eside sokubhekwa.Lokhu kunciphisa ukuphuma kwedatha yesistimu ye-CR.Ngokuthuthuka kobuchwepheshe bokuxhumana okungenazintambo, izinsiza ze-spectrum ziya ngokuya zishuba.Ngenxa yokuthi ubuchwepheshe be-CR bungadambisa le nkinga, ubuchwepheshe be-CR buye banakwa kumanethiwekhi okuxhumana angenantambo, futhi amazinga amaningi enethiwekhi yokuxhumana okungenantambo angenise ubuchwepheshe bomsakazo bokucabanga.Okufana ne-IEEE 802.11, IEEE 802.22 kanye ne-IEEE 802.16h.Esivumelwaneni se-802.16h, kunokuqukethwe okubalulekile kokukhethwa kwe-spectrum eguqukayo ukuze kube lula ukusetshenziswa kwe-WiMAX kwamabhendi erediyo kanye nethelevishini, futhi isisekelo sakho ubuchwepheshe be-spectrum sensing.Ezingeni lamazwe ngamazwe le-IEEE 802.11h lamanethiwekhi endawo angenantambo, imiqondo emibili ebalulekile yethuliwe: i-dynamic spectrum selection (DFS) kanye nokulawula amandla okudlulisa (TPC), futhi umsakazo wokuqonda usetshenziswe kumanethiwekhi endawo angenantambo.Ezingeni elijwayelekile le-802.11y, ubuchwepheshe be-orthogonal frequency division multiplexing (OFDM) busetshenziselwa ukuhlinzeka ngezinketho zomkhawulokudonsa, ezingafinyelela ukushintsha okusheshayo komkhawulokudonsa.Amasistimu e-WLAN (inethiwekhi yendawo engenazintambo) angakwazi ukusebenzisa izici ze-OFDM ukuze agweme ukugwema ngokulungisa umkhawulokudonsa futhi adlulisele amapharamitha wamandla.Thintana nabanye abasebenzisi abasebenza kuleli bhendi yefrikhwensi.Ngenxa yokuthi isistimu engenantambo ye-fiber optical inezinzuzo zomkhawulokudonsa obanzi wokuxhumana we-fiber optical kanye nezici eziguquguqukayo zokuxhumana okungenantambo, isetshenziswe kabanzi.Eminyakeni yamuva nje, ukudluliswa kwamasiginali e-WLAN ye-radio frequency cognitive ku-fiber optical kudonse ukunaka.Umbhali wezincwadi [5-6] uphakamise ukuthi uhlelo lwe-ROF Izimpawu zomsakazo we-Cognitive zisakazwa ngaphansi kwezakhiwo, futhi ukuhlolwa kokulingisa kubonisa ukuthi ukusebenza kwenethiwekhi kuye kwathuthukiswa.
2 ROF-based hybrid optical fibre wireless transmission system architecture
Ukuze kuhlangatshezwane nezidingo zesevisi ye-multimedia yokudluliswa kwevidiyo, i-fiber-to-the-home (FFTH) izoba ubuchwepheshe bokufinyelela obuphelele be-broadband, futhi i-passive optical network (PON) isigxile kakhulu lapho isifikile. ngaphandle.Njengoba amadivaysi asetshenziswa kunethiwekhi ye-PON angamadivayisi angenzi lutho, awadingi ukunikezwa kwamandla, angavikeleka ethonyeni lokuphazanyiswa nombani wangaphandle kagesi, angafinyelela ukudluliswa kwezinsizakalo obala, futhi abe nokuthembeka okuphezulu kwesistimu.Amanethiwekhi e-PON ikakhulukazi ahlanganisa isikhathi sokuhlukaniswa kwe-multiplexing passive optical networks (TDM-PON) kanye ne-wavelength division multiplexing passive optical networks (WDM-PON).Uma kuqhathaniswa ne-TDM-PON, i-WDM-PON inezici zomkhawulokudonsa okhethekile wabasebenzisi kanye nokuvikeleka okuphezulu, okuba inethiwekhi yokufinyelela ebonakalayo enamandla kakhulu esikhathini esizayo.Umfanekiso 1 ubonisa umdwebo we-block wesistimu ye-WDM-PON.