1) Ikhowudi ye-AMI
Igama elipheleleyo lekhowudi ye-AMI (Alternative Mark Inversion) yenye ikhowudi yokuguqula uphawu. blank) ihlala ingatshintshi. Umzekelo:
Ikhowudi yomyalezo: 0 1 1 0 0 0 0 0 0 0 1 1 0 0 1 1…
Ikhowudi ye-AMI: 0 -1 +1 0 0 0 0 0 0 0 0 -1 +1 0 0 -1 +1...
I-waveform ehambelana nekhowudi ye-AMI yinkqubo ye-pulse ene-positive, negative, kunye ne-zero amanqanaba. Inokuthi ithathwe njengenguquko ye-unipolar waveform, oko kukuthi, "0" isahambelana nenqanaba elingu-zero, ngelixa "1" ihambelana namanqanaba alungileyo kunye namabi ngokutshintshanayo.
Inzuzo yekhowudi ye-AMI kukuba akukho nxalenye ye-DC, kukho amacandelo ambalwa aphezulu kunye ne-low-frequency, kwaye amandla agxininiswe kwi-frequency ye-1/2 yekhowudi yesantya.
(Umfanekiso 6-4); Isekethe ye-codec ilula, kwaye ikhowudi ye-polarity ingasetyenziselwa ukujonga imeko yephutha; ukuba i-AMI-RZ waveform, ingatshintshwa ibe yi-unipolar nje ukuba i-full-wave ilungiswe emva kokufumana. I-waveform ye-RZ apho icandelo lexesha elincinci linokukhutshwa. Ngenxa yezi zibonelelo zingentla, ikhowudi ye-AMI iye yaba yenye yeentlobo zekhowudi yothumelo esetyenziswa ngokuqhelekileyo.
Ukungalungi kwekhowudi ye-AMI: Xa ikhowudi yasekuqaleni inoluhlu olude lwe "0", inqanaba lesignali alitsibi ixesha elide, okwenza kube nzima ukukhupha uphawu lwexesha. Enye yeendlela ezisebenzayo zokusombulula ingxaki nokuba "0" ikhowudi kukusebenzisa ikhowudi ye-HDB3.
(2) Ikhowudi ye-HDB3
Igama elipheleleyo lekhowudi ye-HDB3 yikhowudi yesithathu yoxinzelelo oluphezulu lwe-bipolar. Luhlobo oluphuculweyo lwekhowudi ye-AMI. Injongo yokuphucula kukugcina inzuzo yekhowudi ye-AMI kwaye inqobe iintsilelo zayo ukuze inani le "0" ezilandelelanayo lingadluli ezintathu. Imigaqo yayo yokufaka iikhowudi imi ngolu hlobo lulandelayo:
Qala ngokujonga inani lee "0" ezilandelelanayo kwikhowudi yomyalezo. Xa inani lee-“0” ezilandelelanayo lingaphantsi okanye lilingana no-3, iyafana nomgaqo wokufakwa kweekhowudi kwikhowudi ye-AMI. Xa inani lee-“0” ezilandelelanayo lidlula isi-3, i-“0” nganye kwezi-4 ezilandelelanayo iya kuguqulwa ibe licandelo kwaye endaweni yayo ithi “000V”. I-V (ixabiso +1 okanye -1) kufuneka ibe ne-polarity efanayo naleyo yandulela ngokukhawuleza i-non-”0″ pulse emeleneyo (kuba oku kwaphula umthetho wokutshintsha kwe-polarity, ngoko ke u-V ubizwa ngokuba yi-pulse etshabalalisayo). Iikhowudi ze-V ezimeleneyo kufuneka zitshintshwe. Xa ixabiso lekhowudi engu-V linokuhlangabezana neemfuno kwi-(2) kodwa lingenako ukuhlangabezana nale mfuno, emva koko endaweni ka-“0000” nge-“B00V”. Ixabiso le-B liyahambelana ne-V pulse elandelayo ukusombulula le ngxaki. Ngoko ke, u-B ubizwa ngokuba yi-modulation pulse. I-polarity yenombolo yothumelo emva kwekhowudi ye-V kufuneka kwakhona itshintshwe.
Ukongeza kwiinzuzo zekhowudi ye-AMI, ikhowudi ye-HDB3 iphinda inciphise inani leekhowudi ezilandelelanayo "0" ukuya ngaphantsi kwe-3, ukwenzela ukuba ukukhutshwa kolwazi lwexesha kunokuqinisekiswa ngexesha lokufumana. Ngoko ke, ikhowudi ye-HDB3 yolona hlobo lwekhowudi lusetyenziswa kakhulu kwilizwe lam naseYurophu, kunye neentlobo zekhowudi ye-interface engezantsi kweqela le-A-law PCM quaternary zonke iikhowudi ze-HDB3.
Kwikhowudi ye-AMI ekhankanywe ngasentla kunye nekhowudi ye-HDB3, ikhowudi nganye yokubini iguqulwa ibe yikhowudi ene-1-bit yexabiso lenqanaba lesithathu (+1, 0, -1), ngoko olu hlobo lwekhowudi lubizwa ngokuba yikhowudi ye-1B1T. Ukongeza, kuyenzeka kwakhona ukuyila ikhowudi ye-HDBn apho inani elithi "0" lingagqithisi n.
(3) Ikhowudi yeBiphase
Ikhowudi yeBiphase ikwabizwa ngokuba yikhowudi yaseManchester. Isebenzisa ixesha lamaza akwisikwere alungileyo kunye angalunganga ukumela "0" kunye nemo eguqukileyo yamaza ukumela "1". Omnye wemigaqo yokukhowuda kukuba “0” ikhowudi imelwe yi”01” ikhowudi enamanani amabini, kwaye ikhowudi ethi “1″ imelwe “yi-10” ikhowudi enamanani amabini. Umzekelo,
Ikhowudi yomyalezo: 1 1 0 0 1 0 1
Ikhowudi yeBiphase: 10 10 01 01 10 01 10
I-biphasic code waveform yi-bipolar NRZ waveform enamanqanaba amabini kuphela epolarity echaseneyo. Inomtsi wokutsiba kwindawo esembindini wesimboli ngasinye, ngoko iqulethe ulwazi olutyebileyo lwexesha. Akukho candelo le DC, kwaye inkqubo yokufaka ikhowudi nayo ilula. Ukungalungi kukuba i-bandwidth ekhoyo iphindwe kabini, enciphisa izinga lokusetyenziswa kwebhendi yefrikhwensi. Ikhowudi ye-bi-phase ilungile ekuthumeleni izixhobo ze-terminal data kwimigama emifutshane, kwaye isoloko isetyenziswa njengohlobo lwekhowudi yothumelo kwinethiwekhi yendawo yendawo.
(4) Ikhowudi yokwahlukana kwezigaba ezimbini
Ukuze ucombulule impazamo yokuchaza i-decoding ebangelwa ukuguqulwa kwe-polarity yekhowudi ye-bi-phase, ingcamango yekhowudi yokwahlukana ingasetyenziswa. Ikhowudi ye-Biphase isebenzisa inqanaba lenguqu embindini wobude bexesha lesimboli nganye yongqamaniso kunye nokumelwa kwekhowudi yemiqondiso (utshintsho olusuka kumbi ukuya kokulungileyo lumele ibhinari "0", kwaye inguqu ukusuka kokulungileyo ukuya kokubi imele ibhinari "1″). Kwikhowudi yekhowudi ye-biphase eyahlukileyo, inguqu yezinga phakathi kwesimboli ngasinye isetyenziselwa ukuvumelanisa, kwaye ingaba kukho utshintsho olongezelelweyo ekuqaleni kwesimboli ngasinye sisetyenziselwa ukumisela ikhowudi yesignali. Ukuba kukho inguqu, ithetha yokubini "1", kwaye ukuba akukho tshintsho, ithetha ibhinary "0". Le khowudi isetyenziswa rhoqo kuthungelwano lwengingqi yendawo.
Ikhowudi ye-CMI
Ikhowudi ye-CMI sisishunqulelo se-“mark inversion code. Njengekhowudi ye-bi-phase, ikwayi-bipolar ikhowudi yamanqanaba amabini. Umgaqo wekhowudi ngulo: “1″ ikhowudi ngokunye imelwe ngu “11″ kunye no “00” ikhowudi enamanani amabini; i"0" ikhowudi imelwe ngokuthe gqolo ngu "01", kwaye i-waveform yayo iboniswe kuMfanekiso 6-5(c).
Iikhowudi ze-CMI kulula ukuziphumeza kwaye ziqulethe ulwazi olutyebileyo lwexesha. Ukongezelela, ekubeni i-10 liqela lekhowudi engavumelekanga, akuyi kubakho ngaphezu kweekhowudi ezintathu ezilandelelanayo, kwaye lo mgaqo ungasetyenziselwa ukufumanisa impazamo ye-macroscopic. Le khowudi iye yanconywa yi-ITU-T njengohlobo lwekhowudi ye-interface ye-quartet ye-PCM kwaye ngamanye amaxesha isetyenziswe kwiinkqubo zokuhanjiswa kwentambo ye-optical kunye nezinga elingaphantsi kwe-8.448Mb / s.
Nqanda ukufakwa kweekhowudi
Ukuphucula ukusebenza kwekhowudi yomgca, uhlobo oluthile lokuphindaphinda luyafuneka ukuze kuqinisekiswe ulungelelwaniso lwepateni kunye nokufunyanwa kwempazamo. Ukuqaliswa kwekhowudi yebhloko kunokufezekisa zombini ezi njongo kwinqanaba elithile. Uhlobo lwekhowudi yebhloko yikhowudi ye-nBmB, ikhowudi ye-nBmT njalo njalo.
Ikhowudi ye-nBmB luhlobo lwekhowudi yebhloko, eyahlula ikhowudi yokubini ye-n-bit yomthombo wolwazi woqobo kwiqela kwaye iyibuyisele ngeqela elitsha lekhowudi ye-m-bit yokubini, apho m>n. Ukusukela m>n, iqela lekhowudi entsha inokuba Kukho 2^m indibaniselwano, ngoko kukho ngaphezulu (2^m-2^n) indibaniselwano. Phakathi kweendibaniso ezi-2″, iqela lekhowudi elivunyiweyo likhethwa ngandlel’ ithile njengeqela lekhowudi elivumelekileyo, kwaye ezinye zisetyenziswa njengeqela lekhowudi elalelweyo ukufumana ukusebenza kakuhle kwekhowudi. Ngokomzekelo, kwikhowudi ye-4B5B, ikhowudi ye-5-bit isetyenziswe endaweni ye-4-bit code. Ukufakwa kweekhowudi, kumaqela e-4-bit, kukho kuphela i-2^4=16 imidibaniso eyahlukeneyo, kunye ne-5-bit yamaqela, kukho 2^5=32 indibaniselwano eyahlukileyo. Ukuze sifezekise ungqamaniso, asinakulandela ngaphezu kwesinye esikhokelayo "0" kunye nezimamva eziMbini "0" zisetyenziselwa ukukhetha amaqela ekhowudi, kwaye amanye angasebenzi amaqela ekhowudi. Ngale ndlela, ukuba iqela lekhowudi ekhubazekileyo livela ekupheleni kokufumana, kuthetha ukuba kukho impazamo kwinkqubo yokuhambisa, ngaloo ndlela iphucula ukukwazi ukufumanisa impazamo yenkqubo. Zombini iikhowudi ze-bi-phase kunye neekhowudi ze-CMI zinokuthathwa njengeekhowudi ze-1B2B.
Kwinkqubo yokunxibelelana kwe-fiber optical, m = n + 1 isoloko ikhethwa, kwaye ikhowudi ye-1B2B, ikhowudi ye-2B3B, ikhowudi ye-3B4B kunye nekhowudi ye-5B6B ithathwa. Phakathi kwabo, imodeli yekhowudi ye-5B6B isetyenziswe ngokufanelekileyo njengepatheni yekhowudi yokuhambisa umgca kwiqela lesithathu kunye neqela lesine okanye ngaphezulu.
Ikhowudi ye-nBmB inika ulungelelwaniso olufanelekileyo kunye nemisebenzi yokukhangela impazamo, kodwa iphinda ihlawule ixabiso elithile, oko kukuthi, i-bandwidth efunekayo iyanda ngokufanelekileyo.
Umbono woyilo wekhowudi ye-nBmT kukuguqula iikhowudi zokubini zibe liqela elitsha lekhowudi ye m ternary codes, kwaye m
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