The Origins of DRM
In 1998 in Southern China a consortium of broadcasters,
manufacturers, network providers and research institutes
signed up to a formal agreement to create a digital system for
AM broadcasting. To reflect its ambition of becoming a
worldwide standard with global participation, this consortium
was named Digital Radio Mondiale
TM
(DRM
TM
). DRM now
involves more than 80 organisations from across the global
broadcasting industry and counts many major international
broadcasters and receiver manufacturers among its members.
DRM has been highly successful in its aim of creating and
developing the world’s only universal,
non-proprietary
digital
transmission system for broadcasting in the AM bands below
30MHz.DRM has been designed to eventually replace existing
analogue transmission in the LW, MWand SWbands.The DRM
system specification, covering “signal-in-the-air” has been
published by both ETSI (TS 101 980) and the IEC (PAS 62272-
1). It is also the subject of an ITU recommendation (BS 1514).
A great deal of the technical and regulatory work behind DRM
has nowbeenachieved, ready for theofficial, inaugural broadcasts
of the DRM system during June 2003 at the World Radio
CommunicationConference (WRC) 2003 inGeneva, Switzerland.
This article describes the benefits of the DRM system and the
opportunity presented to international broadcasters.
The DRM System – An Overview
DRM addresses the shortcomings of traditional analogue AM
broadcasting. It can provide clear FM-quality reception on long,
medium and short wave, while retaining the essential benefits
of those media; namely coverage over very wide areas at great
distance at low cost per listener.
DRM employs a digital multi-carrier system that sits within
the existing AM channel allocations, it therefore does not
require new frequency spectrum and can co-exist with
analogue transmissions in the same bands. The system can
operate in multiple modes and bandwidths, allowing
broadcasters to optimise the performance of the transmission
over any given transmission path or channel allocation.
DRM’s critical advantage, therefore, is its robustness in the face
of those age-oldAMproblems;multi-path fading and interference.
These problems will become a thing of the past with the DRM
systemas listeners’benefit fromhigher fidelity programmes.DRM
also opens up new possibilities for content.A single channel can
be used to broadcast a mix of voice and data information. High
quality audio can be received alongside pictures and text that
scroll through in near real-time. VT Merlin has run several live
demonstrations of DRM’s multi-media capabilities.
Transmission infrastructure should not require wholesale
replacement. In many cases existing transmitters could be
converted to DRM operation, with the addition of extra digital
coding equipment.Where installations are over 12 year old, a
new transmitter may be needed, but existing power
infrastructure and antenna systems can still be retained. As
the world’s leading commercial AM network operator, VTMerlin
Communications is ideally placed to offer advice and
information on the likely convertibility of any transmitter.
The most commonly asked question is, of course, when will
DRM receivers be available and at what cost? Presently there
are a number of test and development receivers on sale to
the professional broadcast market. At IBC in Amsterdam in
September 2002, the
DRM
consor tium
demonstrated seven
different receiver
examples at their
exhibition stand.One of
these, the DRM
software radio, is
available via a website
managed by VT Merlin
on behalf of the DRM
c o n s o r t i u m
)
. For a
modest
charge
(currently
€
60) users
can download a piece
of software onto their PC and, with a modified analogue
receiver as a front end, pick up DRM transmissions (both audio
and multi-media). Full information is available at the web
address above. A further important development is the
production-ready prototype consumer receiver made by
CodingTechnologies together with the BBC R&D and German
device manufacturer AFG. A hundred of these units are to be
produced for demonstration purposes; this receiver is a world-
band radio with traditional AM reception capabilities but also
DRM decoding too.
Many of the worlds most important receiver manufacturers
are members of DRM (see
for a comprehensive
list) and have been instrumental in the design of the system
specification.With the launch of DRM fast approaching, time
will tell as to which manufacturers will announce products,
when and with what digital capabilities. Manufacturers can
leverage the exper tise they have developed during
implementation of other digital radio technologies, so time-
to-market for new DRM products should be shorter than
previous receivers. The ultimate solution for widespread
adoption of DRM in the developing world will be receivers
comparable in cost to existing AM radios. This is not a pipe-
dream; projects are underway to design and develop low cost
DRM decoding chips for the volume receiver manufacturers
of the Far East.
Why is DRM so important?
Broadcasters are still heavily reliant on AM broadcasting,
nationally and internationally and on all bands.The increasing
availability and diversity of alternative information sources
poses an increasing threat to AM broadcasters.They typically
have much investment tied up in AM infrastructure and a strong
desire to still reach large geographical areas and cross borders
in a way that only AM can.DRM offers the opportunity to remain
competitive through improving the quality, fidelity and reliability
of reception. It presents the chance to increase the economic
life of existing transmission infrastructure, while opening up
the possibilities for new digital services built on the DRM
platform.
New life for the AM bands
Peter Gordon
, Digitalisation Programme Manager, VT Merlin Communications
reveals that digits are coming to the short and medium wave broadcast bands,
bringing benefits to broadcasters and consumers alike
A prototype DRM receiver
