Dongosolo la EPON lili ndi mayunitsi angapo optical network (ONU), optical line terminal (OLT), ndi netiweki imodzi kapena angapo (onani Chithunzi 1).M'njira yowonjezera, chizindikiro chotumizidwa ndi OLT chimawulutsidwa ku ma ONU onse.8h Sinthani mawonekedwe a chimango, fotokozaninso gawo lakutsogolo, ndikuwonjezera nthawi ndi chizindikiritso chomveka (LLID)).LLID imazindikiritsa ONU iliyonse mu dongosolo la PON, ndipo LLID imatchulidwa panthawi yotulukira.
(1) Kuthamanga
Mu dongosolo la EPON, mtunda wapakati pakati pa ONU iliyonse ndi OLT mumayendedwe otumizira uthenga kumtunda siwofanana.Dongosolo la EPON likunena kuti mtunda wautali kwambiri pakati pa ONU ndi OLT ndi 20km, ndipo mtunda waufupi kwambiri ndi 0km.Kusiyana kwa mtundaku kupangitsa 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 zingayambitse mikangano ya zizindikiro zamtunda.Mkanganowu udzabweretsa zolakwika zambiri ndi kutayika kwa kulumikizana, ndi zina zambiri, zomwe zimapangitsa kuti dongosololi lilephere kugwira ntchito moyenera.Pogwiritsa ntchito njira yoyambira, choyamba yezani mtunda wa thupi, ndiyeno sinthani ma ONU onse pamtunda wofanana ndi wa OLT, ndiyeno chitani njira ya TDMA kuti mukwaniritse kupeŵa mikangano.Pakalipano, njira zosiyanasiyana zomwe zimagwiritsidwa ntchito zikuphatikizapo kufalikira-kuyambira, kutuluka kunja kwa gulu ndi mu-band-kutsegula mawindo.Mwachitsanzo, njira yoyambira ma tag ya nthawi imagwiritsidwa ntchito kuyeza nthawi yochedwa ya loop kuchokera ku ONU iliyonse kupita ku OLT, kenako ndikuyika kuchedwetsa kwapadera kwa Td mtengo pa ONU iliyonse, kuti nthawi yakuchedwa kwa ma ONU onse mutatha kuyika Td. (Kutchedwa equalization loop delay value Tequ) ndi ofanana, zotsatira zake zimakhala zofanana ndi kuti ONU iliyonse imasunthidwa kumtunda wofanana ndi wa OLT, ndiyeno chimango chikhoza kutumizidwa molondola malinga ndi luso la TDMA popanda mikangano..
(2) Njira yotulukira
OLT imapeza kuti ONU mu dongosolo la PON imatumiza mauthenga a Gate MPCP nthawi ndi nthawi.Pambuyo polandira uthenga wa Chipata, ONU yosalembetsa idzadikirira nthawi yachisawawa (kupewa kulembetsa nthawi yomweyo ma ONU angapo), ndiyeno kutumiza uthenga wa Register ku OLT.Pambuyo polembetsa bwino, OLT imapatsa LLID ku ONU.
(3) Efaneti OAM
ONU italembetsa ndi OLT, Ethernet OAM pa ONU imayamba njira yotulukira ndikukhazikitsa kulumikizana ndi OLT.Ethernet OAM imagwiritsidwa ntchito pa maulalo a ONU/OLT kuti apeze zolakwika zakutali, kuyambitsa ma loopback akutali, ndikuwona ulalo wabwino.Komabe, Ethernet OAM imapereka chithandizo cha 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 ndi mtundu wa bandwidth womwe ukukulitsidwa mu ONU.Kugwiritsa ntchito kosagwirizana kumeneku ndiye chinsinsi cha mayeso ndipo kumakhala cholepheretsa kulumikizana pakati pa ONU ndi OLT.
(4) Kutsika kwa mtsinje
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.Tiyenera kuganizira makamaka momwe magalimoto akutsikira pansi amatumizira mavidiyo.Chifukwa cha kuwulutsa kwa dongosolo la EPON, wogwiritsa ntchito akasintha makonda pulogalamu ya kanema, imawulutsidwa kwa ogwiritsa ntchito onse, omwe amadya bandwidth yotsika kwambiri.OLT nthawi zambiri imathandizira IGMP Snooping.Ikhoza kuyang'ana mauthenga a IGMP Lowani nawo ndikutumiza deta yambiri kwa ogwiritsa ntchito okhudzana ndi gululi m'malo mofalitsa kwa onse ogwiritsa ntchito, kuchepetsa kuchuluka kwa magalimoto motere.
(5) Kuthamanga kwa mtsinje
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 kuti ifunse mwayi wotumiza, kufotokoza mwatsatanetsatane za mzere uliwonse. OLT iyenera kuyang'anira zofunikira za bandwidth kwa ma ONU onse, ndipo iyenera kuika patsogolo chilolezo chotumizira. Kuwongolera zofunikira za bandwidth pa ma ONU onse.
2.2 Malinga ndi luso la machitidwe a EPON, zovuta zoyesa zomwe EPON imakumana nazo
(1) Poganizira kukula kwa dongosolo la EPON
Ngakhale kuti IEEE802.3ah simatanthawuza kuchuluka kwa chiwerengero mu dongosolo la EPON, chiwerengero chachikulu chothandizidwa ndi dongosolo la EPON chimachokera ku 16 mpaka 128. ONU iliyonse yolowa mu EPON imafuna gawo la MPCP ndi gawo la OAM.Pamene masamba ambiri akulowa mu EPON, chiopsezo cha zolakwika zamakina chidzawonjezeka.Mwachitsanzo, ONU iliyonse iyenera kupezanso njira, njira yolowera ndikuyamba gawo la OAM.Choncho, nthawi yobwezeretsa dongosolo lonse idzawonjezeka ndi chiwerengero cha ONU.
(2) Vuto la kulumikizana kwa zida
Zotsatirazi zimaganiziridwa makamaka pakulumikizana kwa zida:
● The dynamic bandwidth algorithm (DBA) yoperekedwa ndi opanga osiyanasiyana ndi yosiyana.
●Opanga ena amagwiritsa ntchito “Organization Specific Elements” ya OAM kuti akhazikitse makhalidwe enaake.
●Kaya kukhazikitsidwa kwa protocol ya MPCP sikufanana.
●Kaya njira zoyezera mtunda zopangidwa ndi opanga osiyanasiyana zimagwirizana ndi mawotchi.
(3) Zowopsa zobisika pakufalitsa ntchito zosewerera katatu mu dongosolo la EPON
Chifukwa cha mawonekedwe opatsirana a EPON, zoopsa zina zobisika zidzayambitsidwa potumiza masewero atatu:
● Kutsika kwapansi kumawononga kwambiri bandwidth: dongosolo la EPON limagwiritsa ntchito njira yotumizira mauthenga kumtunda: ONU iliyonse idzalandira kuchuluka kwa magalimoto otumizidwa ku ma ONU ena, kuwononga zambiri zapansi.
●Kuchedwa kwa mtsinje kumakhala kwakukulu: Pamene ONU itumiza deta ku OLT, iyenera kuyembekezera mwayi wotumizira woperekedwa ndi OLT.Chifukwa chake, ONU iyenera kusungitsa kuchuluka kwa magalimoto akumtunda, zomwe zingayambitse kuchedwa, jitter, ndi kutayika kwa paketi.
3 ukadaulo woyeserera wa EPON
Kuyesa kwa EPON kumaphatikizapo zinthu zingapo monga kuyesa kugwirizanirana, kuyesa kwa protocol, kuyesa kachitidwe ka kachitidwe ka makina, ntchito ndi kutsimikizira ntchito.Mayeso amtundu wanthawi zonse akuwonetsedwa mu Chithunzi 2. Zogulitsa za IXIA za IxN2X zimapereka khadi loyesera la EPON, mawonekedwe oyesera a EPON, amatha kujambula ndi kusanthula ma protocol a MPCP ndi OAM, amatha kutumiza kuchuluka kwa magalimoto a EPON, kupereka pulogalamu yoyesera yokha, komanso imathandizira ogwiritsa ntchito kuyesa. Ma algorithms a DBA.
