Tese tinoziva zvakanyanya kuti nyika yetekinoroji yakatitenderedza ndeyedhijitari, kana kuti iri kuvavarira. Digital terevhizheni kutepfenyura kuri kure nenyowani, asi kana wanga usina kunyatsoifarira, matekinoroji aripo anogona kukushamisa iwe.

Zviri mukati mechikamu chechinyorwa

• Chikamu 1: General dhizaini yeCATV network
• Chikamu 2: Kuumbwa uye waveform
• Chikamu 3: Analog chikamu chechiratidzo
• Chikamu 4: Digital chikamu chechiratidzo
• Chikamu 5: Coaxial Distribution Network
• Chikamu 6: RF Amplifiers
• Chikamu 7: Optical Receivers
• Chikamu 8: Optical backbone network
• Chikamu 9: Musoro
• Chikamu 10: Troubleshooting pamusoro tambo TV network

Kuumbwa kwedhijitari terevhizheni chiratidzo

Chiratidzo cheterevhizheni chedhijitari inzira yekufambisa yemhando dzakasiyana dzeMPEG (dzimwe nguva mamwe macodec), inofambiswa neredhiyo chiratidzo uchishandisa QAM yemadhigirii akasiyana. Aya mazwi anofanirwa kujeka sezuva kune chero chiratidzo, saka ini ndichangopa gif kubva Wikipedia, iyo, ndinovimba, ichapa nzwisiso yezviri kune avo vanga vasati vambofarira:

Kuchinja kwakadaro mune imwe nzira kana imwe kunoshandiswa kwete chete ku "terevhizheni anachronism", asiwo kune ese masystem ekutumira data pakakwirira tekinoroji. Iko kumhanya kwedhijitari mutambo ye "antenna" mazana emamegabits!

Digital chiratidzo parameters

Tichishandisa iyo Deviser DS2400T mumodhi yekuratidza madhijitari masaini paramita, tinogona kuona kuti izvi zvinoitika sei chaizvo:

Network yedu ine masaini ezviyero zvitatu panguva imwe chete: DVB-T, DVB-T2 uye DVB-C. Ngativatarisei mumwe nemumwe.

DVB-T

Iyi chiyero haina kuzove iyo huru munyika yedu, ichipa nzira kune yechipiri vhezheni, asi yakanyatsokodzera kushandiswa neanoshanda nekuda kwekuti DVB-T2 vanogashira vari kumashure vanoenderana neyekutanga chizvarwa standard, zvinoreva kuti munyoreri. inogona kugamuchira chiratidzo chakadaro pane chero dhijitari TV isina mamwe maconsoles. Pamusoro pezvo, chiyero chakatarirwa kutapurirana pamusoro pemhepo (bhii T inomirira Terrestrial, ether) ine ruzha rwakanaka rwekudzivirira uye redundancy zvekuti dzimwe nguva inoshanda uko, nekuda kwechimwe chikonzero, chiratidzo cheanalogi hachigone kupinda.

Pachidzitiro chemudziyo tinogona kuona kuti boka renyeredzi re64QAM riri kuvakwa sei (chiyero chinotsigira QPSK, 16QAM, 64QAM). Zvinogona kuoneka kuti mumamiriro ezvinhu chaiwo mapoinzi haasanganisire mune imwe, asi huya nekumwe kuparadzira. Izvi zvakajairika chero bedzi decoder ichigona kuona kuti nzvimbo yekusvika ndeyapi, asi kunyangwe mumufananidzo uri pamusoro pane nzvimbo dzavari pamuganhu kana padyo nayo. Kubva pamufananidzo uyu unogona kukurumidza kuona kunaka kwechiratidzo "neziso": kana amplifier isiri kushanda zvakanaka, semuenzaniso, madotsi anowanikwa chaotically, uye TV haigoni kuunganidza mufananidzo kubva kune yakagamuchirwa data: iyo "pixelates" , kana kutoomesa nechando zvachose. Pane dzimwe nguva iyo amplifier processor "inokanganwa" kuwedzera chimwe chezvikamu (amplitude kana chikamu) kune chiratidzo. Mumamiriro ezvinhu akadaro, pachiratidziro chemudziyo unogona kuona denderedzwa kana kurira saizi yemunda wese. Mapoinzi maviri ari kunze kwemunda mukuru ndiwo mareferenzi emugamuchiri uye haatakure ruzivo.

Kurutivi rworuboshwe rwechidzitiro, pasi peiyo chiteshi nhamba, tinoona huwandu hwema paramita:

Chiyero chechiratidzo (P) mune imwecheteyo dBµV neyeanalogue, zvisinei, yedhijitari chiratidzo GOST inoronga chete 50 dBµV pakupinza kune anogamuchira. Ndiko kuti, munzvimbo dzine attenuation yakakura, "digital" ichashanda zviri nani kupfuura analogue.

Kukosha kwezvikanganiso zvemodulation (MER) inoratidza kukanganiswa kwechiratidzo chatiri kugamuchira, ndiko kuti, kureba kwakadii kwenzvimbo yekusvika kubva pakati pechikwere. Iyi parameter yakafanana nechiratidzo-ku-ruzha reshiyo kubva kune analog system; iyo yakajairika kukosha kwe64QAM inobva pa28 dB. Zvinogona kuoneka zvakajeka kuti kutsauka kwakakosha mumufananidzo uri pamusoro kunoenderana nemhando yepamusoro peyakajairwa: uku ndiko kusadzivirirwa kweruzha rwechiratidzo chedhijitari.

Nhamba yezvikanganiso muchiratidzo chakagamuchirwa (CBER) - nhamba yezvikanganiso muchiratidzo isati yagadziriswa nechero kugadzirisa algorithms.

Nhamba yezvikanganiso mushure mekushanda kweViterbi decoder (VBER) ndiwo mhedzisiro yedecoder inoshandisa isina ruzivo kudzoreredza zvikanganiso muchiratidzo. Ose maviri maparameter aya anoyerwa mu "zvidimbu pahuwandu hwakatorwa." Kuti mudziyo uratidze huwandu hwekukanganisa isingasviki imwe mumazana zana kana gumi miriyoni (sezviri pamufananidzo uri pamusoro), inofanirwa kugamuchira aya mamirioni gumi mabits, izvo zvinotora nguva pane imwe chiteshi, saka kuyerwa kunoguma. haina kuoneka nekukasira, uye inogona kunge yakaipa pakutanga (E -03, semuenzaniso), asi mushure memasekondi mashoma unosvika yakanakisa parameter.

DVB-T2

Iyo dhijitari yekutepfenyura mwero yakagamuchirwa muRussia inogona zvakare kufambiswa kuburikidza netambo. Chimiro chenyeredzi chinogona kunge chichishamisa pakutanga kuona:

Kutenderera uku kunowedzera kusadzivirirwa kweruzha, sezvo iye anogamuchira achiziva kuti boka renyeredzi rinofanira kutenderedzwa nekona rakapihwa, zvinoreva kuti rinogona kusefa izvo zvinouya pasina yakavakirwa-mukati shanduko. Zvinogona kuonekwa kuti kune iyi chiyero chiyero chekukanganisa chiyero chehukuru hwepamusoro uye zvikanganiso muchiratidzo chisati chagadziriswa hazvichapfuuri chiyero chekuyera, asi chinosvika ku8,6 chaiyo pamiriyoni. Kuti vagadzirise, decoder inoshandiswa LDPC, saka parameter inonzi LBER.
Nekuda kwekuwedzera kusadzivirirwa kweruzha, chiyero ichi chinotsigira mwero we256QAM, asi parizvino 64QAM chete ndiyo inoshandiswa kutepfenyura.

DVB-C

Iyi chiyero yakatanga kugadzirirwa kutapurirana kuburikidza netambo (C - Cable) - yepakati yakagadzikana zvakanyanya kupfuura mhepo, saka inobvumira kushandiswa kweyepamusoro dhigirii yemodulation kupfuura DVB-T, uye nekudaro inotumira huwandu hukuru hweruzivo pasina kushandisa yakaoma. coding.

Pano tinoona boka renyeredzi 256QAM. Kune mamwe masikweya, saizi yavo yave diki. Mukana wekukanganisa wawedzera, zvinoreva kuti imwe yakavimbika yepakati (kana yakanyanya kuomarara coding, semuDVB-T2) inodiwa kutumira chiratidzo chakadaro. Chiratidzo chakadaro chinogona "kuparadzira" panoshanda analogi uye DVB-T / T2, asi zvakare ine muganho wekudzivirira kweruzha uye kukanganisa kugadzirisa algorithms.

Nekuda kwepamusoro mukana wekukanganisa, iyo MER parameter ye256-QAM inojairirwa kusvika makumi matatu nemaviri dB.

Iyo counter yekukanganisa mabheti yakakwira imwe kurongeka kwehukuru uye ikozvino inoverengera imwe yakanganisa bit pabhiriyoni, asi kunyangwe paine mazana emamiriyoni avo (PRE-BER ~E-07-8), iyo Reed-Solomon decoder yakashandiswa mune ino. standard ichabvisa zvikanganiso zvese.

Source: www.habr.com