Todays analog radio system still follows the basic principle of frequency modulation invented back in 1993.In addition to audio transmission ,very limited information such as the station identification can accompany the programs.Transmission quality varies greatly depending on multi-path effects and the interferance.The fully digital DAB systems doen not only offer sound in a CD like quality ,it is immune to interferance and multipath propagation.
DAB systems can use single frequency network(sfn) i.e all the senders transmitting the same radio program operate at same frequency .Today ,different senders have to use different frequencies to avoid inteferance although they are transmitting the same radio program.Using an SFN is very frequency efficient , as a single radio station only needs one frequency throughout the whole country.Additionally , DAB transmission power per antenna is orders of magnitude lower compared to traditional FM stations.DAB uses VHF and UHF frequency bands(depending on national regulations) e.g:- the terrestial tv channels 5 to 12 (175- 230 Mhz ) or the L-band .The modulation with 192 to 1536 carriers so called ensemble within DAB channel of 1.5 Mhz.
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