1 Mawu Oyamba
Ndi chitukuko chofulumira chaukadaulo wofikira ma burodibandi, matekinoloje osiyanasiyana omwe akungotuluka kumene mvula itatha.Pambuyo ukadaulo wa PON ndiukadaulo wa DSL ndi ukadaulo wa chingwe, nsanja ina yabwino yofikira, PON imatha kupereka mwachindunji mautumiki owonera kapena ntchito za FTTH.EPON ndi mtundu watsopano waukadaulo waukadaulo wofikira pa intaneti, wogwiritsa ntchito mfundo kumapangidwe amitundu yambiri, kufalitsa kuwala kopanda gwero, kupereka mautumiki osiyanasiyana a Ethernet.Imagwiritsa ntchito ma topology a PON kuti agwiritse ntchito mwayi wa Ethernet, ndipo ukadaulo wa PON umagwiritsidwa ntchito pazosanjikiza zakuthupi.Choncho, imagwirizanitsa ubwino wa teknoloji ya PON ndi teknoloji ya Ethernet: mtengo wotsika;mkulu bandwidth;scalability yamphamvu, yosinthika komanso yofulumira kukonzanso ntchito;kuyanjana ndi Ethernet yomwe ilipo;kasamalidwe yabwino, etc. EPON mayeso ndi wosiyana kwambiri ndi zida chikhalidwe Efaneti.Nkhaniyi ikuyang'ana kwambiri paukadaulo woyeserera wa EPON.
2 Kuyambitsa ukadaulo wa EPON ndi zovuta zoyesa
TheEPONdongosolo lili ndi kuchuluka kwa mayunitsi a optical network, terminal yowunikira (OLT), ndi mawonekedwe amodzi kapena angapo (onani Chithunzi 1).Panjira yotsika, chizindikiro chotumizidwa ndi OLT chimawulutsidwa pa ma ONU onse.Mu njira ya uplink, njira za TDMA zamakina ambiri zimagwiritsidwa ntchito, ndipo chidziwitso cha uplink cha ma ONU angapo chimapanga chidziwitso cha TDM ku OLT.802.3AH Sinthani mawonekedwe a Ethernet frame, fotokozaninso gawo lodziwikiratu, onjezani masitampu anthawi ndi zozindikiritsa maulalo omveka (LLID).LLID imazindikiritsa ONU iliyonse yadongosolo la PON ndikutchula LLID panthawi yotulukira.
3 Ukadaulo wofunikira mu dongosolo la PON
Mu dongosolo la EPON, mtunda wapakati pakati pa ONU iliyonse ndi OLT mumayendedwe otumizira uthenga kumtunda siwofanana.Nthawi zambiri, dongosolo la EPON limanena kuti mtunda wautali kwambiri kuchokera ku ONU kupita ku OLT ndi 20km, ndipo mtunda waufupi kwambiri ndi 0km.Kusiyanaku kwa mtunda kumapangitsa kuchedwa kusiyanasiyana pakati pa 0 ndi 200 ife.Ngati palibe kusiyana kokwanira kudzipatula, zizindikiro zochokera ku ONU zosiyana zimatha kufika kumapeto kwa OLT nthawi yomweyo, zomwe zimayambitsa mikangano ya zizindikiro zamtunda.Kusemphana maganizo kungayambitse zolakwika zambiri ndi kutayika kwa kuyanjanitsa, ndi zina zotero, zomwe zimapangitsa kuti dongosololi lisagwire ntchito bwino.Pogwiritsa ntchito njira yoyambira, choyamba yezani mtunda wakuthupi, kenaka sinthani ma ONU onse pamtunda wofanana ndi wa OLT, ndiyeno perekani njira ya TDMA kuti mupewe mikangano.Njira zomwe zikugwiritsidwa ntchito panopa zikuphatikiza kufalikira-kuyambira, kutuluka kunja kwa gulu ndi mu-band mawindo otsegula kuyambira.Mwachitsanzo, pogwiritsa ntchito njira yoyambira nthawi, choyamba yezani nthawi yochedwa kuzungulira kwa siginecha kuchokera ku ONU iliyonse kupita ku OLT, ndiyeno ikani kuchedwetsa kwapadera kwa Td mtengo pa ONU iliyonse, kuti kuchedwetsa kwa ma ONU onse mutatha kuyika Td akhoza. kupezedwa Nthawi (yotchedwa Equalization loop delay value Tequ) ndi yofanana, ndipo zotsatira zake zimakhala zofanana ndi kusuntha ONU iliyonse kumtunda wofanana ndi wa OLT, ndiyeno kutumiza chimango molondola malinga ndi luso la TDMA popanda kugunda.
OLT imapeza kuti ONU mu dongosolo la PON nthawi ndi nthawi imatumiza mauthenga a Gate MPCP.Pambuyo pa ONU yosalembetsa italandira uthenga wa Chipata, idzadikirira nthawi yodzidzimutsa (kupewa kulembetsa nthawi yomweyo kwa ma ONU angapo), ndiyeno tumizani uthenga wa Register ku OLT.Pambuyo polembetsa bwino, OLT imapatsa LLID ku ONU.
ONU ikalembetsa ndi OLT, Ethernet OAM pa ONU imayamba njira yotulukira ndikukhazikitsa kulumikizana ndi OLT.Ethernet OAM imagwiritsidwa ntchito pozindikira zolakwika zakutali pa ulalo wa ONU/OLT, kuyambitsa loopback yakutali, ndikuwona ulalo waubwino.Komabe, Ethernet OAM imapereka chithandizo kwa ma OAM PDUs, magawo azidziwitso, ndi malipoti a nthawi.Opanga ambiri a ONU/OLT amagwiritsa ntchito zowonjezera za OAM kukhazikitsa ntchito zapadera za ONU.Ntchito yodziwika bwino ndikuwongolera bandwidth ya ogwiritsa ntchito kumapeto kudzera mu mtundu wowonjezera wa bandwidth mu ONU.Kugwiritsa ntchito kosagwirizana kumeneku ndiye chinsinsi cha mayeso ndipo kumakhala cholepheretsa kulumikizana pakati pa ONU ndi OLT.
OLT ikakhala ndi magalimoto otumiza ONU, imanyamula chidziwitso cha LLID cha komwe akupita ONU mumsewu.Chifukwa cha mawonekedwe owulutsa a PON, deta yotumizidwa ndi OLT idzaulutsidwa ku ma ONU onse.Makamaka, momwe magalimoto akutsikira pansi amatumizira mayendedwe a kanema ayenera kuganiziridwa.Chifukwa cha mawonekedwe owulutsa a dongosolo la EPON, wogwiritsa ntchito akakonza pulogalamu yamavidiyo, imawulutsidwa kwa ogwiritsa ntchito onse, omwe amadya kwambiri bandwidth yakumunsi.OLT nthawi zambiri imathandizira IGMP Snooping.Itha kuyang'anira mauthenga a IGMP Lowani nawo ndikutumiza deta ya multicast kwa ogwiritsa ntchito okhudzana ndi gululo m'malo mofalitsa kwa ogwiritsa ntchito onse, potero kuchepetsa kuchuluka kwa magalimoto.
ONU imodzi yokha ingatumize magalimoto panthawi inayake.ONU ili ndi mizere yambiri yofunika kwambiri (mzere uliwonse umafanana ndi mlingo wa QoS. ONU imatumiza uthenga wa Report ku OLT kupempha mwayi wotumiza, kufotokoza mwatsatanetsatane za mzere uliwonse. OLT imatumiza uthenga wa Chipata ku ONU kuti auze ONU. nthawi yoyambira kufalitsa kotsatira ku OLT Iyenera kuyendetsa zofunikira za bandwidth za ma ONU onse, ndipo iyenera kupereka patsogolo mphamvu zopatsirana.Molingana ndi kutsogolo kwa mzere, kulinganiza zopempha za ONU angapo. Kutha kuyang'anira zofunikira za bandwidth za ma ONU onse ndikugawa mwamphamvu bandwidth (ie DBA algorithm).