Ndi chitukuko cha njira zoyankhulirana zopita ku burodibandi ndi kuyenda, optical fiber wireless communication system (ROF) imaphatikiza kulumikizana kwa fiber ndi kulumikizana opanda zingwe, kupereka kusewera kwathunthu paubwino wa Broadband ndi anti-interference of optical fiber lines, komanso kulumikizana opanda zingwe. . Zosavuta komanso zosinthika zimakwaniritsa zomwe anthu amafuna pa burodibandi. Ukadaulo woyambirira wa ROF udaperekedwa makamaka kuti upereke ntchito zotumizira ma waya opanda zingwe, monga ma millimeter wave optical fiber transmission. Ndi chitukuko ndi kukhwima kwa ROF luso, anthu anayamba kuphunzira wosakanizidwa mawaya ndi opanda zingwe kufala maukonde, kutanthauza, CHIKWANGWANI opanda zingwe kulankhulana (ROF) kachitidwe kupereka mawaya ndi opanda zingwe ntchito pa nthawi yomweyo. Ndi chitukuko chofulumira cha mauthenga a pawailesi, kuchepa kwa zipangizo zamakono kwakhala kodziwika kwambiri. Momwe mungasinthire kugwiritsidwa ntchito kwa ma sipekitiramu pansi pazida zopanda zingwe zopanda zingwe kuti muchepetse kutsutsana pakati pa kupezeka ndi kufunikira kwazinthu zowoneka bwino lakhala vuto lomwe liyenera kuthetsedwa m'munda wolumikizana. Cognitive Radio (CR) ndiukadaulo wanzeru wogawana nawo. Ikhoza kupititsa patsogolo kagwiritsidwe ntchito ka zinthu zosiyanasiyana pogwiritsa ntchito "kugwiritsanso ntchito kachiwiri" kwa sipekitiramu yovomerezeka, ndipo yakhala malo opangira kafukufuku pazochitika za mauthenga. Mu 802.11 opanda zingwe amderali network [1], 802.16 metropolitan area network [2] ndi 3G mobile communication network [3] ayamba kuphunzira kugwiritsa ntchito chidziwitso chaukadaulo wawayilesi kuti apititse patsogolo luso la dongosolo, ndipo adayamba kuphunzira kugwiritsa ntchito Ukadaulo wa ROF kuti ukwaniritse kufalikira kosakanikirana kwamasigino osiyanasiyana abizinesi[4]. Maukonde olumikizana ndi mawayilesi opangira ma waya omwe amatumiza ma siginecha opanda zingwe ndi mawayilesi ndi njira yopititsira patsogolo maukonde olumikizirana amtsogolo. Njira yosakanizidwa ya ROF yotengera luso lachidziwitso lawayilesi imayang'anizana ndi zovuta zambiri zatsopano, monga kapangidwe kamangidwe ka maukonde, kapangidwe ka protocol kasanjidwe, kutulutsa ma siginecha opangidwa ndi mawaya ndi opanda zingwe kutengera mautumiki angapo, kasamalidwe ka netiweki, ndikuzindikiritsa ma siginecha osinthidwa.
1 Ukadaulo wodziwa wailesi
Wailesi yachidziwitso ndi njira yabwino yothetsera kusowa kwa sipekitiramu komanso kusagwiritsidwa ntchito bwino kwa sipekitiramu. Wailesi yachidziwitso ndi njira yanzeru yolumikizirana opanda zingwe. Imazindikira kugwiritsiridwa ntchito kwa malo ozungulira ndikusintha magawo ake moyenera pophunzira kuti agwiritse ntchito bwino. Zida zama Spectrum ndi kulumikizana kodalirika. Kagwiritsidwe ntchito ka wailesi yachidziwitso ndiukadaulo wofunikira kuti muzindikire gwero la sipekitiramu kuyambira pagawo lokhazikika mpaka kugawa kosinthika. Mudongosolo lachidziwitso lawayilesi, kuti muteteze wogwiritsa ntchito wovomerezeka (kapena kukhala wogwiritsa ntchito) kuti asasokonezedwe ndi wogwiritsa ntchito kapolo (kapena wogwiritsa ntchito CR), ntchito yozindikira ma sipekitiramu ndikuzindikira ngati wogwiritsa ntchito wovomerezeka alipo. Ogwiritsa ntchito mawayilesi ozindikira amatha kugwiritsa ntchito ma frequency band kwakanthawi pomwe iwunikiridwa kuti ma frequency bandi omwe amagwiritsidwa ntchito ndi wovomerezeka sakugwiritsidwa ntchito. Zikawunikidwa kuti gulu lafupipafupi la wogwiritsa ntchito wovomerezeka likugwiritsidwa ntchito, wogwiritsa ntchito CR amatulutsa njira kwa wogwiritsa ntchito wovomerezeka, motero amaonetsetsa kuti wogwiritsa ntchito CR sakusokoneza wogwiritsa ntchito wovomerezeka. Chifukwa chake, maukonde olumikizana opanda zingwe ali ndi zinthu zotsatirazi: (1) Wogwiritsa ntchito kwambiri amakhala ndi mwayi wopeza tchanelo. Kumbali imodzi, wogwiritsa ntchito wovomerezeka akapanda kukhala panjira, wogwiritsa ntchito wachiwiri ali ndi mwayi wopeza njira yopanda ntchito; pamene wogwiritsa ntchito woyamba awonekeranso, wogwiritsa ntchito wachiwiri ayenera kutuluka pa tchanelo mu nthawi yake ndikubwezera tchanelo kwa wogwiritsa ntchito woyamba. Kumbali ina, pamene wogwiritsa ntchito wamkulu atenga tchanelo, wogwiritsa ntchito kapolo amatha kulowa panjirayo popanda kukhudza mtundu wautumiki wa wogwiritsa ntchito wamkulu. (2) Malo ochezera a CR ali ndi ntchito za kuzindikira, kasamalidwe ndi kusintha. Choyamba, malo ochezera a CR amatha kuzindikira mawonekedwe afupipafupi ndi njira zogwirira ntchito m'malo ogwirira ntchito, ndikudziwitsanso kugawana ndi kugawa kwazinthu zamagulu malinga ndi malamulo ena malinga ndi zotsatira zowunikira; kumbali ina, CR yolumikizirana yolumikizira imatha kusintha magawo ogwirira ntchito pa intaneti, monga kusintha magawo otumizira monga ma frequency onyamula ndi njira yosinthira amatha kusintha kusintha kwa chilengedwe. Mu maukonde olumikizana opanda zingwe, kuzindikira kwa ma spectrum ndi ukadaulo wofunikira. Ma algorithms omwe amagwiritsidwa ntchito nthawi zambiri amaphatikizira kuzindikira mphamvu, kuzindikira zofananira ndi zosefera, ndi njira zozindikirira mawonekedwe a cyclostationary. Njirazi zili ndi ubwino ndi zovuta zake. Kuchita kwa ma aligorivimuwa kumatengera zomwe zidapezeka kale. Ma algorithms omwe alipo a spectrum sensing ndi: fyuluta yofananira, chowunikira mphamvu ndi njira zowonera. Fyuluta yofananira ingagwiritsidwe ntchito pamene chizindikiro chachikulu chikudziwika. Chowunikira mphamvu chingagwiritsidwe ntchito pazochitika zomwe chizindikiro chachikulu sichidziwika, koma ntchito yake imawonongeka pamene nthawi yochepa yozindikira ikugwiritsidwa ntchito. Chifukwa lingaliro lalikulu la chojambulira mawonekedwe ndikugwiritsa ntchito cyclostationarity ya siginecha kuti izindikire kudzera muntchito yolumikizirana. Phokoso ndi siginecha yotakata ndipo ilibe kulumikizana, pomwe siginecha yosinthidwa imalumikizidwa ndi cyclostationary. Choncho, ntchito ya spectral correlation imatha kusiyanitsa mphamvu ya phokoso ndi mphamvu ya chizindikiro chosinthidwa. M'malo okhala ndi phokoso losatsimikizika, magwiridwe antchito a chowunikira amakhala bwino kuposa chowunikira mphamvu. Kugwira ntchito kwa chojambulira mawonekedwe pansi pa chiŵerengero chochepa cha chizindikiro-to-phokoso ndi chochepa, chimakhala ndi zovuta zowerengera, ndipo zimafuna nthawi yayitali yoyang'ana. Izi zimachepetsa kutulutsa kwa data kwa dongosolo la CR. Ndi chitukuko chaukadaulo wolumikizirana opanda zingwe, zida za sipekitiramu zikuchulukirachulukira. Chifukwa ukadaulo wa CR utha kuchepetsa vutoli, ukadaulo wa CR waperekedwa chidwi pamanetiweki olumikizirana opanda zingwe, ndipo miyezo yambiri yolumikizirana opanda zingwe idayambitsa ukadaulo wamawayilesi. Monga IEEE 802.11, IEEE 802.22 ndi IEEE 802.16h. Mumgwirizano wa 802.16h, pali zofunikira pakusankha kwamitundu yosiyanasiyana kuti zithandizire kugwiritsa ntchito kwa WiMAX pamawayilesi a wailesi ndi kanema wawayilesi, ndipo maziko ake ndiukadaulo womvera ma spectrum. Mu IEEE 802.11h mulingo wapadziko lonse wa ma netiweki am'deralo opanda zingwe, mfundo ziwiri zofunika zadziwika: dynamic spectrum selection (DFS) ndi transmit power control (TPC), ndipo wailesi yachidziwitso yakhala ikugwiritsidwa ntchito pamanetiweki am'deralo opanda zingwe. Muyeso wa 802.11y, ukadaulo wa orthogonal frequency division multiplexing (OFDM) umagwiritsidwa ntchito popereka njira zingapo za bandwidth, zomwe zimatha kukwaniritsa kusintha kwa bandwidth mwachangu. Makina a WLAN (opanda mawaya amdera lanu) atha kutengerapo mwayi pamakhalidwe a OFDM kupewa kupewa posintha bandwidth ndikutumiza magawo amagetsi. Zosokoneza ndi ena ogwiritsa ntchito mu bandi yama frequency awa. Chifukwa makina opanda zingwe opanda zingwe ali ndi maubwino a bandwidth yolumikizana ndi ma fiber ambiri komanso mawonekedwe osinthika a kulumikizana opanda zingwe, amagwiritsidwa ntchito kwambiri. M'zaka zaposachedwa, kufalikira kwa ma radio frequency cognitive WLAN siginecha mu fiber optical kwakopa chidwi. Wolemba mabuku [5-6] adanena kuti machitidwe a ROF Cognitive radio signals amafalitsidwa pansi pa zomangamanga, ndipo kuyesa koyerekeza kumasonyeza kuti machitidwe a netiweki asinthidwa.
2 ROF-based hybrid optical fiber wireless transmission system yomanga
Pofuna kukwaniritsa zosowa za ma multimedia mautumiki otumizira makanema, makina omwe akubwera kunyumba (FFTH) adzakhala ukadaulo wapamwamba kwambiri wopezera ma burodibandi, ndipo passive optical network (PON) yakhala yofunika kwambiri ikangobwera. kunja. Popeza zida zomwe zimagwiritsidwa ntchito pa netiweki ya PON ndi zida zopanda ntchito, sizifunikira mphamvu zamagetsi, zimatha kutetezedwa ndi kusokonezedwa ndi ma elekitiroma akunja ndi mphezi, zimatha kukwaniritsa ntchito zowonekera, komanso kukhala ndi kudalirika kwakukulu. Maukonde a PON makamaka amaphatikizira ma network ophatikizika a nthawi yayitali (TDM-PON) ndi ma wavelength division multiplexing passive optical network (WDM-PON). Poyerekeza ndi TDM-PON, WDM-PON ili ndi mawonekedwe ogwiritsira ntchito bandiwifi yokhayokha komanso chitetezo chokwanira, kukhala njira yolumikizirana kwambiri m'tsogolomu. Chithunzi 1 chikuwonetsa chithunzi cha block cha dongosolo la WDM-PON.