1 Kev Taw Qhia
Nrog rau txoj kev loj hlob sai ntawm kev siv thev naus laus zis thev naus laus zis, ntau yam kev siv thev naus laus zis tshiab tau tshwm sim tom qab los nag. Tom qab PON thev naus laus zis yog DSL thev naus laus zis thiab cable thev naus laus zis, lwm lub platform zoo tshaj plaws, PON tuaj yeem muab cov kev pabcuam kho qhov muag ncaj qha lossis FTTH cov kev pabcuam. EPON yog ib hom tshiab ntawm fiber ntau siv network technology, siv cov ntsiab lus rau ntau lub ntsiab lus qauv, tsis muaj lub teeb kis tau tus mob, muab ntau yam kev pabcuam Ethernet. Nws siv PON's topologies los siv Ethernet nkag, thiab PON thev naus laus zis yog siv rau hauv txheej txheej hauv lub cev. Yog li ntawd, nws koom nrog qhov zoo ntawm PON thev naus laus zis thiab Ethernet thev naus laus zis: tus nqi qis; bandwidth siab; muaj zog scalability, hloov tau yooj yim thiab ceev kev pab cuam restructuring; compatibility nrog Ethernet uas twb muaj lawm; yooj yim tswj, thiab lwm yam. EPON xeem yog txawv heev los ntawm cov tsoos Ethernet khoom. Kab lus no tsom mus rau EPON kev xeem thev naus laus zis.
2 EPON thev naus laus zis kev taw qhia thiab kev xeem sib tw
CovEPONLub kaw lus muaj ntau qhov chaw kho qhov muag, lub teeb davhlau ya nyob twg (OLT), thiab ib lossis ntau qhov spectra (saib daim duab 1). Hauv kev taw qhia downlink, lub teeb liab xa los ntawm OLT yog tshaj tawm rau txhua ONUs. Nyob rau hauv cov kev taw qhia uplink, TDMA multi-channel cov tswv yim yog siv, thiab cov ntaub ntawv uplink ntawm ntau ONUs ua TDM cov ntaub ntawv rau OLT. 802.3AH Hloov kho Ethernet thav duab hom, rov txhais cov ntsiab lus ua ntej, ntxiv cov ntawv teev sijhawm thiab cov cim txuas txuas (LLID). LLID txheeb xyuas txhua ONU ntawm PON system thiab qhia txog LLID thaum lub sijhawm nrhiav pom.
3 Cov thev naus laus zis tseem ceeb hauv PON system
Nyob rau hauv EPON system, lub cev nyob deb ntawm txhua ONU thiab OLT nyob rau hauv lub upstream cov ntaub ntawv kis tau tus mob yog tsis sib npaug. Feem ntau, EPON system qhia tias qhov ntev tshaj plaws ntawm ONU mus rau OLT yog 20km, thiab qhov luv tshaj plaws yog 0km. Qhov sib txawv ntawm qhov kev ncua deb no ua rau ncua sij hawm sib txawv ntawm 0 thiab 200 peb. Yog tias tsis muaj qhov sib txawv txaus, cov teeb liab ntawm ONUs sib txawv tuaj yeem ncav cuag qhov kawg ntawm OLT nyob rau tib lub sijhawm, ua rau muaj kev tsis sib haum xeeb ntawm cov teeb liab ntws. Kev tsis sib haum xeeb tuaj yeem ua rau muaj ntau qhov yuam kev thiab synchronization poob, thiab lwm yam, ua rau lub cev tsis ua haujlwm zoo. Siv txoj kev sib txawv, ua ntej ntsuas lub cev nyob deb, tom qab ntawd kho tag nrho ONUs mus rau tib qhov kev ncua deb li OLT, thiab tom qab ntawd ua raws li TDMA txoj kev kom tsis txhob muaj teeb meem. Cov kev siv ntau yam tam sim no suav nrog kev sib kis-spectrum sib txawv, tawm ntawm pawg sib txawv thiab hauv-band qhov rais-qhib ntau. Piv txwv li, siv lub sij hawm-scale sib piv txoj kev, ua ntej ntsuas lub teeb liab voj ncua sij hawm los ntawm txhua ONU mus rau lub OLT, thiab ces ntxig ib tug sib npaug zos ncua ncua sij hawm Td tus nqi rau txhua ONU, kom lub voj qeeb ntawm tag nrho cov ONUs tom qab inserting Td tau. tau txais Lub Sijhawm (xa mus rau qhov sib npaug ntawm lub voj voog ncua sijhawm Tequ) yog qhov sib npaug, thiab qhov tshwm sim zoo ib yam li txav txhua ONU mus rau tib lub laj thawj nyob deb li OLT, thiab tom qab ntawd xa cov ncej kom raug raws li TDMA thev naus laus zis tsis muaj kev sib tsoo.
OLT pom tias ONU nyob rau hauv lub PON system ib ntus xa Gate MPCP cov lus. Tom qab ONU uas tsis tau sau npe tau txais cov lus Gate, nws yuav tos lub sijhawm random (kom tsis txhob sau npe ib txhij ntawm ntau ONU), thiab tom qab ntawd xa cov lus Sau npe rau OLT. Tom qab kev tso npe ua tiav, OLT muab LLID rau ONU.
Tom qab ONU sau npe nrog OLT, Ethernet OAM ntawm ONU pib cov txheej txheem tshawb pom thiab tsim kev sib txuas nrog OLT. Ethernet OAM yog siv los xyuas cov chaw taws teeb tsis raug ntawm ONU / OLT txuas, ua rau cov chaw taws teeb rov qab, thiab tshawb xyuas qhov txuas zoo. Txawm li cas los xij, Ethernet OAM muab kev txhawb nqa rau kev cai OAM PDUs, cov ntaub ntawv qhia, thiab cov ntawv ceeb toom sijhawm. Ntau ONU / OLT cov tuam txhab siv OAM txuas ntxiv los teeb tsa cov haujlwm tshwj xeeb ntawm ONUs. Ib daim ntawv thov raug yog los tswj cov bandwidth ntawm cov neeg siv kawg los ntawm kev txuas ntxiv cov qauv bandwidth hauv ONU. Daim ntawv thov tsis yog tus qauv no yog tus yuam sij rau kev xeem thiab dhau los ua qhov cuam tshuam rau kev sib txuas lus ntawm ONU thiab OLT.
Thaum OLT muaj tsheb thauj mus los xa ONU, nws yuav nqa cov ntaub ntawv LLID ntawm qhov chaw ONU hauv kev tsheb. Vim yog cov yam ntxwv tshaj tawm ntawm PON, cov ntaub ntawv xa los ntawm OLT yuav tshaj tawm rau txhua ONUs. Tshwj xeeb, qhov xwm txheej uas cov tsheb thauj mus los hauv qab xa cov kev pabcuam video yuav tsum tau txiav txim siab. Vim qhov kev tshaj tawm cov yam ntxwv ntawm EPON system, thaum tus neeg siv hloov kho qhov kev pab cuam video, nws yuav tshaj tawm rau txhua tus neeg siv, uas siv ntau qhov chaw qis qis. OLT feem ntau txhawb IGMP Snooping. Nws tuaj yeem saib xyuas IGMP Koom Nrog Thov cov lus thiab xa cov ntaub ntawv ntau yam rau cov neeg siv cuam tshuam nrog pab pawg es tsis txhob tshaj tawm rau txhua tus neeg siv, yog li txo cov tsheb khiav.
Tsuas yog ib qho ONU tuaj yeem xa cov tsheb khiav ntawm lub sijhawm. ONU muaj ntau qhov tseem ceeb hauv kab (txhua kab ntawv sib raug rau qib QoS. ONU xa cov lus ceeb toom rau OLT kom thov lub sijhawm xa, piav qhia txog qhov xwm txheej ntawm txhua kab. OLT xa Gate lus rau ONU los qhia ONU lub sijhawm pib ntawm kev xa mus rau OLT tom ntej Nws yuav tsum muaj peev xwm tswj hwm cov kev cai bandwidth ntawm tag nrho ONUs, thiab yuav tsum tau muab qhov tseem ceeb rau txoj cai sib kis raws li qhov tseem ceeb ntawm cov kab, sib npaug cov kev thov ntawm ntau ONUs muaj peev xwm tswj hwm cov kev cai bandwidth ntawm tag nrho ONUs thiab dynamically faib upstream bandwidth (ie DBA algorithm).