Digital Television Broadcasting and Single Frequency Networks
While are we talk about us digital broadcasting usually talk about better image and sound, tall definition television, MPEG’S pressure and option be. Anyway, best of all men is not aware of that lie technology behind digital broadcasting and what gain with technological digital other than pictured better and sound.
Root from transition to digital television broadcasting lies in purpose more effective from radio-frequency spectrum. At our analog television the world one have grooved radio frequency (frequency) where each frequency sends one Tv Channel (program) and that avoid same frequency interference get again been used just far-away. Digital Technology to let we to use continuing pressure algorithm to compress audio and video signal, accordingly we get to use one frequency path to send more than one service (usually three tenth and even more Tv Channel), and we can build one network emittinging to dissect thus same frequency significantly down number from frequency (path) necessary to cover one region.
There are several default for digital television broadcasting. For terrestrial television Negara use system as ISDB t, T DMB, ATSC and DVB T. DVB t is maybe the most imperially be used it is used at Europe, Russia, Australia, India, and a lot of other country. All these system is base COFDM’S Coded Orthogonal’s Frequency Division Multiplexing. This is one design of modulation with many thousand spaced Carrie coherences, each take in digital information.
Frequency plots for DVB t is base allotment area where all dispatch transmitter on same frequency. How come we send on nonintervention same frequency because? Well, there is interference but within umpteen this curb is constructive. This helps at demodulating signal. Fact is at whatever dot signs from different transmitter to arrive at different time. But since signal is digital signal same be gotten. Long from digital data device with which each longer ruled than distinctive time arrives from different transmitter. This in addition to each device lengthened by one interval looks after. Up to device guard interval that equals varying arrival time get without been gotten whatever inter device interference. This is basic principle from Single Frequency Network (SFN).
Obviously, maximum distance between emitting dissect same frequency depends on long from guard interval. With appropriate planning from SFNs distance from 70 km gets to be reached. This matter that all transmitter is dissect same frequency and is same content broadcasting. This is one over huge gain analog television where that we will need a lot of frequency to cover same area.
This obvious it digital broadcasting of a lot of gain. Digital network needs to be synchronized to run with every consideration at SFNs and it can be sometimes nasty. This correctness that digital network fare tall but it be divided among many services. And most important fact is it digital network fare significantly inferior than cost of radio-frequencies spectrum most valuable resource.