29 Mar Spectrum Efficiency of DRM in the FM Band – Your Question Answered
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29th March 2021
After the India trial there was a lot of talk about the spectrum efficiency of DRM in the FM band. How efficient is it really? [Members of the India DRM WhatsApp group]
DRM is the most efficient, flexible standard in all frequency bands. In the FM band DRM achieves 8 DRM services in the 200kHz bandwidth (occupied by one FM service) and thus it is compatible with the existing current analogue FM bandwidth licensing policy in India and many other countries of the world. If used in white space (between 800kHz analogue spacing, as existing in India for example) DRM can operate in 500kHz with 5 independent DRM blocks providing 5 independent frequencies, with a total of 20 DRM services (e.g. 15 audio services plus 5 data Journaline services). Each independent DRM block (of the five) could be used by the same broadcaster or could be auctioned to different broadcasters.
DRM in VHF bands provides bit rates from 37 kbps to 186 kbps. DRM uses the xHE-AAC codec (also used in mobiles/cells) which gets best in class audio compression even at very low kbps. For example, xHE-AAC achieves good audio at 8+ kbps for mono and 16+kbps for stereo services.