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[HCDX] RADIO REVOLUTION, THE DRM WAY
RADIO REVOLUTION, THE DRM WAY
With clear, near-FM quality sound, excellent reception
and dramatic improvement over analogue, Digital Radio
Mondiale (DRM) will revitalize radio in markets
worldwide.
Traditional AM can travel great lengths along the
curvature of the earth, but it is notoriously prone to
disturbances. The same holds true for short wave,
which can reach the other side of the planet by
bouncing a signal off the ionosphere. But its
reception is prone interference from solar conditions,
the time of day and year as well as the distance
between the transmitter and the target receiver.
There is a global trend towards the adoption of
digital technology in radio and communications,
especially for distribution and transmission.
Digitalization offers many substantial advantages to
national/international broadcasters and info casters.
We are seeing the introduction of high quality
delivery systems in homes. FM sound broadcasting is
gradually moving to a DAB standard. But coverage on FM
88-108 MHz (VHF) is limited. For many national and
international broadcasters, the advantage of a
complementary digital broadcast system below 30 MHz is
gradually emerging. However, the limited fidelity of
existing AM services is causing listeners to search
for other alternatives.
Implementation of digital radio in today?s AM bands
(i.e. long, medium and short wave) will enable
operators to provide services that should be
successful with both existing and future high-quality
services operating on other parts of the dial. Digital
broadcasting on short wave, medium wave, or long wave
(AM) is highly advantageous when compared to the
conventional analogue system that is now in use.
Digital Radio Mondiale (DRM) is a fast emerging domain
that combines the benefits of FM and AM. This has FM
like sound quality with lesser multi-path interference
and the reach of AM. Some DRM receivers and equipment
are already available to broadcasters and consumers,
with more expected throughout 2004. Besides providing
near ? FM quality audio, the DRM system has the
capacity to integrate data and text. This additional
content can be displayed on DRM receiver to enhance
the listening experience.
Unlike digital systems that require a new frequency
allocation, DRM uses existing AM broadcast frequency
bands. The DRM signal is designed to fit in with the
existing AM broadcasting AM broadcast band plan, based
on signals of 9 kHz or 10 kHz bandwidth. It has modes
requiring as little as 4.5 kHz or 5 kHz bandwidth,
plus modes that can take advantage of wider bandwidth,
such as 18 or 20 kHz. Simulcast testing is underway.
Many existing AM transmitters can be easily modified
to carry DRM signals.
The DRM technology works by encoding the signal using
MPEG 4 compression to make it fit the existing AM
bandwidth. While minimizing interface, the digital
technology has only two modes: reception and no
reception. Hardcore short wave fans who appreciate the
challenge of deciphering short wave broadcasts
unperturbed by the notorious fading may lament this.
But near FM digital quality makes short wave
interesting for an audience that has never touched a
world band receiver before. Another advantage is that
DRM requires only 10% of the power needed for
traditional short wave transmission and therefore, for
broadcasters, new transmission equipment pays for
itself. Furthermore, DRM allows for dual transmission
mode, broadcasting analogue as well as digital.
DRM applications include fixed and portable radios,
car receivers, software receivers and PDAs. Depending
on broadcasters preferences, the DRM system can use
three types of audio coding. MPEG4 AAC audio coding
augmented by SBR bandwidth extension is used as a
general-purpose audio coder and provides the highest
quality. MPEG4 CELP speech coding is used for high
quality speech coding where there is no musical
content. HVXC speech coding can be used to provide a
very low bit-rate speech coder.
Today, DRM is the world?s only non-proprietary,
digital system for short, medium and long wave with
the ability to use existing frequencies and bandwidth
across the globe. It is the only digital radio system
recommended by the international telecommunication
union (ITU) for all the three radio bands below 30MHz
short wave, medium wave, and long wave. In January
2003 the DRM consortium took the first hurdle in
standardizing audio broadcasts on the AM bands when
the International Electro-technical Committee (IEC)
granted the DRM transmission technology an
international standard.
Since DRM?s inaugural broadcast on June 16, 2003, more
than 60 broadcasters have started transmitting their
daily, weekly or periodic DRM programs. Thereafter, an
increasing number of broadcasters started their DRM
transmissions. In August 2003, DRM and the World DAB
Forum announced their cooperation, paving the way for
DRM and DAB capable receivers. Sony has committed to
help expand the markets for digital radio in Europe,
pledging its active support in the commercial sectors
of both DRM and World DAB Forum.
India remains oblivious to the benefits of such a
platform; leave aside launching this technology. While
speaking to India?s only radio network in this
context, few were even aware that radio was on the
threshold of going digital!
(Recently published in AV MAX, an audio-visual monthly
publication.)
Regards & 73?s
Mukesh Kumar
Muzaffarpur
INDIA.
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