Sonke sazi kakuhle ukuba ihlabathi letekhnoloji elisijikelezileyo leledijithali, okanye lizabalazela oko. Usasazo lweDijithali kamabonakude akude kutsha, kodwa ukuba awukhange ube nomdla ngokuthe ngqo kuyo, ubuchwephesha obukhoyo bunokukothusa.
Iziqulatho zoluhlu lwamanqaku
- Icandelo 4: ICandelo loMqondiso weDijithali
- Icandelo 5: Inethiwekhi yokusabalalisa i-coaxial
- Icandelo 6: I-RF Signal Amplifiers
- Icandelo 7: Abamkeli bamehlo
- Icandelo 8: Inethiwekhi ye-Optical backbone
- Icandelo 9: Intloko
- Icandelo 10: Ukulungisa inethiwekhi yeCATV
Ukuqulunqwa komqondiso kamabonakude wedijithali
Isignali kamabonakude wedijithali yindlela yothutho yeenguqulelo ezahlukeneyo zeMPEG (ngamanye amaxesha ezinye iicodecs), ezihanjiswa ngumqondiso werediyo usebenzisa i-QAM yeedigri ezahlukeneyo. La magama kufuneka acace njengemini kuye nawuphi na umqondiso, ngoko ke ndiza kunika i-gif ukusuka , endiyathemba ukuba, iya kunika ukuqonda ukuba yintoni na kwabo bangekabi namdla:
Ukumodareyitha okunjalo ngendlela enye okanye enye ayisetyenziselwa kuphela "i-anachronism yethelevishini", kodwa nazo zonke iinkqubo zokuhanjiswa kwedatha kwi-teknoloji ephezulu. Isantya somsinga wedijithali kwintambo "ye-antenna" ngamakhulu eemegabhithi!
Iiparamitha zomqondiso wedijithali
Ukusebenzisa i-Deviser DS2400T kwindlela yokubonisa iiparamitha zesignali yedijithali, sinokubona ukuba oku kwenzeka njani ngokwenene:
Uthungelwano lwethu luqulethe iimpawu zemigangatho emithathu ngaxeshanye: DVB-T, DVB-T2 kunye neDVB-C. Masizijonge nganye nganye.
I-DVB-T
Lo mgangatho awuzange ube ngowona uphambili kwilizwe lethu, unika indlela kuguqulelo lwesibini, kodwa ulungele ukusetyenziswa ngumqhubi ngenxa yokuba abamkeli be-DVB-T2 babuyela ngasemva bayahambelana nomgangatho wesizukulwana sokuqala, okuthetha ukuba umrhumi. ingafumana umqondiso onjalo phantse kuyo nayiphi na iTV yedijithali ngaphandle kweeconsole ezongezelelweyo. Ukongezelela, umgangatho ojoliswe ekugqithiseni emoyeni (unobumba u-T umele i-Terrestrial, i-ether) une-immunity enhle yengxolo kunye ne-redundancy ukuba ngamanye amaxesha isebenza apho, ngenxa yesizathu esithile, umqondiso we-analog awukwazi ukungena.
Kwisikrini sesixhobo sinokujonga indlela i-constellation ye-64QAM eyakhiwa ngayo (umgangatho uxhasa i-QPSK, i-16QAM, i-64QAM). Kungabonwa ukuba kwiimeko zokwenyani amanqaku awadibanisi kwelinye, kodwa eze kunye nokusasazeka. Oku kuqhelekile okoko idikhowuda inokugqiba ukuba yeyiphi isikwere indawo yokufika, kodwa nakulo mfanekiso ungasentla kukho iindawo ezibekwe kuzo kumda okanye kufutshane nayo. Kulo mfanekiso unokugqiba ngokukhawuleza umgangatho wesignali "ngeso": ukuba i-amplifier ayisebenzi kakuhle, umzekelo, amachaphaza ahlala e-chaotically, kwaye iTV ayikwazi ukuqokelela umfanekiso kwidatha efunyenweyo: "i-pixelates" , okanye nokuba ngumkhenkce ngokupheleleyo. Kukho amaxesha apho iprosesa ye-amplifier "ikhohlwa" ukongeza enye yamacandelo (i-amplitude okanye isigaba) kwisignali. Kwiimeko ezinjalo, kwisikrini sesixhobo ungabona isangqa okanye u-ring ubungakanani bendawo yonke. Amanqaku amabini angaphandle kwebala eliphambili ngamanqaku okubhekisela kummkeli kwaye musa ukuthwala ulwazi.
Kwicala lasekhohlo lesikrini, phantsi kwenombolo yesitishi, sibona iiparamitha zobungakanani:
Inqanaba lomqondiso (P) kwi-dBµV efanayo neye-analogu, nangona kunjalo, kwisiginali yedijithali iGOST ilawula kuphela i-50 dBµV kwigalelo kumamkeli. Oko kukuthi, kwiindawo ezinokunciphisa okukhulu, "idijithali" iya kusebenza ngcono kune-analogue.
Ixabiso leempazamo zohlengahlengiso (SEA) ibonisa indlela egqwethekileyo ngayo isignali esiyifumanayo, oko kukuthi, ukuba indawo yokufika ingaba njani ukusuka kumbindi wesikwere. Le parameter ifana ne-signal-to-noise ratio esuka kwi-analog system; ixabiso eliqhelekileyo le-64QAM lisuka kwi-28 dB. Ingabonwa ngokucacileyo ukuba ukuphambuka okuphawulekayo kumfanekiso ongentla kuhambelana nomgangatho ongaphezulu kwesiqhelo: oku kukukhusela kwingxolo yesignali yedijithali.
Inani leempazamo kuphawu olufunyenweyo (CBER) - inani leempazamo kwisignali ngaphambi kokuqhutyelwa ngayo nayiphi na i-algorithms yokulungiswa.
Inani leempazamo emva kokusebenza kweViterbi decoder (VBER) sisiphumo sedikhowuda esebenzisa ulwazi olungafunekiyo ukubuyisela iimpazamo kumqondiso. Zombini ezi parameters zilinganiswa "ngeziqwenga ngobungakanani obuthathiweyo." Ukuze isixhobo sibonise inani leempazamo ngaphantsi kwesinye kwikhulu lamawaka okanye ishumi lezigidi (njengoko kulo mfanekiso ungasentla), kufuneka samkele ezi bits ezizigidi ezilishumi, ezithatha ixesha elithile kwitshaneli enye, ngoko umphumo wokulinganisa ayiveli ngokukhawuleza, kwaye inokuba mbi ekuqaleni (E -03, umzekelo), kodwa emva kwemizuzwana embalwa ufikelela kwiparameter ebalaseleyo.
DVB-T2
Umgangatho wosasazo lwedijithali owamkelwe eRashiya nawo unokuhanjiswa ngentambo. Ukumila kwekroza kunokumangalisa ngandlel’ ithile xa uthi krwaqu nje:
Oku kujikeleziswa kongeza ukhuseleko lwengxolo, kuba umamkeli uyazi ukuba umlaza kufuneka ujikelezwe nge-engile enikiweyo, okuthetha ukuba inokucoca into ezayo ngaphandle kokutshintsha okwakhelwe ngaphakathi. Kuyabonakala ukuba kulo mgangatho imilinganiselo yempazamo ye-bit ngumyalelo wobukhulu obuphezulu kwaye iimpazamo kumqondiso phambi kokuba ukucubungula akusagqithi kumda wokulinganisa, kodwa zifikelela kwi-8,6 yokwenyani ngesigidi. Ukuzilungisa, kusetyenziswa idikhowuda I-LDPC, ngoko iparameter ibizwa ngokuba yi-LBER.
Ngenxa yokwanda kokhuselo lwengxolo, lo mgangatho uxhasa inqanaba lokumodareyitha le-256QAM, kodwa okwangoku yi-64QAM kuphela esetyenziswayo kusasazo.
I-DVB-C
Lo mgangatho wawudalelwe ukuhanjiswa ngentambo (C - Cable) - iphakathi ezinzile ngakumbi kunomoya, ngoko ke ivumela ukusetyenziswa kweqondo eliphezulu lokumodareyitha kune-DVB-T, kwaye ke ngoko idlulisela isixa esikhulu solwazi ngaphandle kokusebenzisa ubunzima. ikhowudi.
Apha sibona iqela leenkwenkwezi 256QAM. Kukho izikwere ezininzi, ubukhulu bawo bube buncinci. Ithuba lempazamo liye landa, oku kuthetha ukuba i-medium ethembekileyo (okanye ikhowudi enzima ngakumbi, njenge-DVB-T2) iyafuneka ukuhambisa umqondiso onjalo. Umqondiso onjalo "unokuthi "usasaze" apho i-analog kunye ne-DVB-T / T2 isebenza, kodwa inomda we-immunity yengxolo kunye ne-algorithms yokulungisa iimpazamo.
Ngenxa yokwenzeka kwempazamo ephezulu, iparamitha ye-MER ye-256-QAM iqhelekile ukuya kuma-32 dB.
I-counter of bits ephosakeleyo inyuke enye indlela yobukhulu kwaye ngoku ibala i-bit ephosakeleyo kwibhiliyoni nganye, kodwa nokuba kukho amakhulu ezigidi zazo (PRE-BER ~E-07-8), i-Reed-Solomon decoder esetyenziswe kule umgangatho uya kuphelisa zonke iimpazamo.
umthombo: www.habr.com