Povećanje broja programa u multipleksima DVB-T2 sistema

Abstract

televizija / television

Predmet istraživanja prikazanog u ovoj doktorskoj tezi je emitovanje TV programa preko digitalnih sistema za prenos televizijskog signala putem zemaljskih predajnika druge generacije DVB-T2 (Digital Video Broadcasting- Terrestrial), koji se koristi u Evropi. DVBT2 je savremeni sistem koji omogućava da se u multipleksu RF kanala opsega 8 MHz emituje 15-18 programa standardne definicije, SD (Standard definition), ali samo 4-6 programa visoke definicije, HD (High Definition), koji imaju mnogo veće bitske protoke. Poboljšanje kvaliteta nastaviće se kroz formate HD i 3D programa druge generacije, do formata ultra visokih definicija, UHD (Ultra High Definition) u budućnosti. Nove formate će karakterisati sve veći izvorni tok. Bez obzira na primenu efikasnih tehnika komprimovanja, kao što je HEVC (High Efficiency Video Coding), protok komprimovanog video signala će biti sve veći, a u multipleks jednog RF kanala će moći da se smesti sve manje TV programa. Istraživanje se vrši u trenutku kada nadležne institucije postepeno smanjuju opseg namenjen DTT emitovanju (Digital Terrestrial Television), pa se sa očekivanih 3 do 9 multipleksa (još uvek nije definisano), moraju zadovoljiti očekivanja korisnika i zadržati konkurentnost na tržištu. Cilj istraživanja je da se sagledaju mogućnosti DVB-T2 sistema i predlože rešenja za emitovanje što većeg broja HD i UHD programa. Na bazi dostupnih istraživanja, kako u zemaljskoj, tako i u drugim srodnim tehnikama emitovanja video sadržaja, kao i originalnih istraživanja, predložena su rešenja za povećanje broja emitovanih TV programa. Kroz kvantifikaciju i sprovedene proračune utvrđeni su pojedinačni dometi predloženih rešenja, kao i rezultat njihove istovremene primene. Kao značajne za dalju analizu u razmatranje su uzete činjenice koje karakterišu sadašnje, nazovimo ga tradicionalno, smeštanje TV programa u DVB-T2 multiplekse: a) Frekvencijska karakteristika multipleksa digitalnih TV programa u RF kanalu je sasvim drugačija od karakteristike analognog TV programa. b) Multipleks TV programa se emituje preko RF kanala nasleđenog iz vremena analognih TV programa sa opsegom od 8MHz, od čega se efektivno koristi 7.61 do 7.77 MHz, a ostatak služi kao zaštitni frekvencijski interval na krajevima opsega. Ovaj opseg nije namenjen niti prilagođen potrebama digitalnog emitovanja, a pre svega nije dovoljan resurs za velike protoke HD i UHD programa. c) Komprimovani video signal ima promenljivi protok, VBR (Variable Bit Rate), pa je iskorišćenost kapaciteta kanala promenljiva i povezana sa brojem programa i primenjenim tehnikama njihovog multipleksiranja. U radu se pošlo od opšteprihvaćene pretpostavke da su svojstava protoka komprimovanog HD i UHD video sadržaja ista kao i kod SD formata...

This doctoral thesis presents research of broadcasting TV programmes through the second generation terrestrial digital video systems DVB-T2 (Digital Video Broadcasting - Terrestrial), which has been used in Europe. DVB-T2 is a modern system which allows multiplexing 15-18 SD (Standard definition) programmes in single RF channel, but only 4-6 HD (High Definition) programmes of the first generation, due to their higher bit rate. Farther quality improvements of HD and 3D programmes will continue through the second generation of HD and UHD (Ultra High Definition), formats in the future. The services in the new formats will have more and more source rates. Regardless of the application of highly effective compression techniques, such as HEVC (High Efficiency Video Coding), the rate of the compressed video signal will be continuously increasing. Multiplex in single RF channel will be able to accommodate only a few TV programmes. Research has been conducted during the time when the authorities are trying to decrease the spectrum accounted to the DTT broadcasting (Digital Terrestrial Television), so expected 3 to 9 multiplexes (not determined yet), need to satisfy the users expectations and maintain market demand. The objective of the research was to examine the possibilities of DVB-T2 system, and propose solutions which would result in broadcasting a larger number of HD and UHD programmes. Based on available research, both in the terrestrial and in other related techniques of broadcasting, as well as on the results of original studies, some solutions have been proposed on how to increase the number of broadcasted TV programmes. Through quantification and implemented calculations, have been determined the individual achievements of the proposed solutions, as well as their simultaneous applications. For the purposes of further analysis, it is important to analyze the facts that characterize the present, let's call it traditional, allocation of TV programmes in DVB-T2 multiplexes: a) Frequency characteristic of multiplex of digital TV programmes in the RF channel is quite different from the analog TV programme. b) RF channel bandwidth, for example 8 MHz, is inherited from the times of analog TV programmes. Only 7.61 to 7.77 MHz can be used effectively , while the rest of it is used as a protective (gard) frequency interval at the ends of the band. This bandwidth is not designed or tailored for the needs of digital broadcasting, especially for the HD and UHD programmes, since its does not have the neccessery reasources. c) The compressed video signal has a VBR (Variable Bit Rate) nature, and the utilization of the channel capacity is also variable and depends on a number of programmes and applied techniques of their multiplexing. It is generally accepted that the rate properties of compressed HD and UHD video content is the same as in SD format. d) Because of the frequency and time selective response of wireless channel, system parameters are set on the threshold for acceptable broadcasting in case of bad conditions of transmission. As a precaution, large part of the capacity is used as a redundancy for protection at different levels...