Thursday, June 7, 2012
DAB - the wave of the future?
DAB is a digital radio format for broadcasting radio stations used in several countries, particularly in Europe. As of 2006, approximately 1,002 stations worldwide broadcast in the DAB format.
The DAB standard was initiated as a European research project in the 1980s. The Norwegian Broadcasting Corporation (NRK) launched the very first DAB channel in the world on June 1 1995 (NRK Klassisk), and the BBC and SR launched their first DAB digital radio broadcasts in September 1995. DAB receivers have been available in many countries since the end of the nineties. DAB possesses the capacity to allow more radio programmes over a specific spectrum than analogue FM radio. DAB is more robust with regard to noise and multipath fading, since DAB reception quality first degrades rapidly when the signal strength falls below a critical threshold, whereas FM reception quality degrades slowly with the decreasing signal.
An unblinded "informal listening test" by Sverre Holm has shown that for stationary listening the audio quality on DAB is subjectively lower than FM stereo (but this may be due to observer bias). Most stations using a bit rate of 128 kbit/s or less, with the MP2 audio codec, which requires 160 kbit/s to achieve perceived FM quality. 128 kbit/s gives better dynamic range or signal-to-noise ratio than FM radio, but a more smeared stereo image, and an upper cutoff frequency of 14 kHz, corresponding to 15 kHz of FM radio. However, "CD sound quality" with MP2 is possible "with 256..192 kbps".
An upgraded version of the system was released in February 2007, which is called DAB+. DAB is not forward compatible with DAB+, which means that DAB-only receivers will not be able to receive DAB+ broadcasts. DAB+ is approximately twice as efficient as DAB due to the adoption of the AAC+ audio codec, and DAB+ can provide high quality audio with as low as 64 kbit/s. Reception quality will also be more robust on DAB+ than on DAB due to the addition of Reed-Solomon error correction coding.
In spectrum management, the bands that are allocated for public DAB services, are abbreviated with T-DAB, where the "T" stands for terrestrial.
More than 20 countries provide DAB transmissions, and several countries, such as Australia, Italy, Malta, Switzerland and Germany, have started transmitting DAB+ stations. However, DAB radio has still not replaced the old FM system in popularity.
It's certainly good to see that radio hasn't lost its incentive to move and progress into the the future with innovative, SQ-improving innovations. At least for the foreseeable future, terrestrial radio will still be there to provide local coverage such as traffic and weather, and those are but two relevant reasons for the medium to exist well into the future. At least until dematerialization becomes our main mode of travel and we can dodge the raindrops (not to mention traffic mishaps), AM radio, with periodic updates of road closings, for instance, will still provide a necessary service to get us to and from where we're going, physically and logistically speaking. FM radio here in the United States is still a viable broadcast entertainment medium, however restricted you might find the current offerings in your area. I personally find surfing for local internet stations around the world lots of fun, and listening in unfamiliar markets reminds me of everyday life there (wherever there ends up to be!). Even foreign language stations are cool, it really doesn't even matter what propaganda might or might not be being disseminated at any given time. If it's music you're after, the difference in what's available in that country will be immediately obvious. If it's mindless chatter, you can get plenty of that here in the good ol' US of A!
Tomorrow, it's more of that programming that makes you jump for joy, puts a wiggle in your giggle, and rocks your rolls. So, keep your tubes hot and your antenna up! See you then!