[LINK] Digital radio
david.boxall at hunterlink.net.au
Sat May 30 16:14:49 AEST 2009
On Thu, 28 May 2009 at 17:00:18 +1000 I wrote:
> For the time being, I reckon I'll stick to my lash-up (SD set-top box -
> $59, plus 7" LCD monitor - $48, and ancient speakers - $?). The sound
> could be better, but it receives the Band III test transmissions from
> Sydney OK.
To satisfy my own curiosity, I looked into what's planned for digital
radio. Some of it might be of interest to Link.
Apparently, test transmissions were DAB, but the industry intends using
DAB+. My cheap lash-up probably won't work.
Broadcasts will be in VHF Band III and L-Band (just below 1.5 GHz). I
haven't found anything for my local area, but the frequencies allocated
in Sydney are between analogue TV channels 9 & 10 (in the area occupied
by digital TV channel 9A).
For regional areas, Digital Radio Mondiale (DRM) and L-Band satellite
are mentioned. They seem to be talking DRM on Band III, but
<http://www.drm.org/> indicates that it is more suited to lower
frequencies: "While DRM currently covers the broadcasting bands below 30
MHz, the DRM consortium voted in March 2005 to begin the process of
extending the system to the broadcasting bands up to 174 MHz. The
design, development and testing phases are expected to be completed by
2009". The satellite option offers some hope to remote & regional areas.
I wonder what the battery drain would be like (for a portable radio
without a dish antenna)?
For the time being, there are no plans to discontinue AM and FM
transmissions. I wonder about the impact if (when) that eventually
happens. For example, what happens to "In disaster situations, listen to
your local ABC radio" if the signal comes via satellite and it's the
same for the whole continent?
DAB, DAB+, T-DAB, S-DAB, DRM, DRM Plus: help! Every technology comes
with a plethora of initialisms/acronyms, but here we have TLAs Plus.
... most DAB receivers will not be able to receive the DAB+ broadcasts
that the industry will use when digital radio officially launches.
The ABC has had a long-standing commitment to the development of digital
radio in Australia. New digital-only radio services are being developed
that will complement existing services.
Commercial broadcasters will commence test transmissions of digital
radio services in the five mainland state capitals during May 2009. It
is expected that the national broadcasters will commence their digital
radio services in these markets by 1 July 2009.
The legislation is premised on digital radio as a supplement to existing
radio services in Australia, rather than a replacement technology. ...
This report responds to the Minister’s Direction of 18 December 2004 on
the question of spectrum availability for digital radio in bands
corresponding to those used for the T-DAB (Eureka 147) standard.
*Spectrum available in the short-term*
Subject to necessary regulatory aspects being addressed, three VHF Band
III and three L-Band frequency blocks can be provided in each of the
five major metropolitan centres.
The VHF services may not fully cover their respective metropolitan
licence areas. For the Sydney case, which was studied in some detail,
information received from a current T-DAB trial indicates that VHF
coverage will be patchy at locations beyond Parramatta and other
locations at similar distances from the transmitter site. In addition
there could be some areas of deficient coverage due to shadowing by CBD
*VHF transmitter deployment constraints*
Transmitters using the VHF frequency blocks must be effectively co-sited
with operating channel 9 and channel 10 analog television transmitters
in order to avoid causing adjacent channel interference to viewers of
those television services. This will generally prevent the deployment of
a VHF single frequency network (SFN), although there may be scope to
implement low power VHF SFN transmitters at some television translator
sites, subject to a strategy being developed and implemented to manage
and remedy any interference to television reception.
*L-Band repeater requirements*
To address these VHF coverage deficiencies a network of L-Band repeaters
would be required to in-fill and extend the coverage achieved by the VHF
transmitter. Depending on the prediction model used and the amount of
coverage of the licence area about 5 to 11 such L-Band translators might
be required. Although it was not studied, it is expected that in cities
other than Sydney a smaller number of L-Band in-fill/coverage extenders
would be required.
Due to the requirement for in-fill transmitters the available VHF Band
III and L-Band frequency blocks would need to be allocated as pairs so
that broadcasters could be given the capability to fully cover their
radio licence area. The regulatory aspects of such an arrangement have
not been explored in this report. The use of L-Band to in-fill VHF
services is not ideal as there will be short interruptions to reception
when receivers switch between the different bands. The
preferred VHF SFN approach where all transmitters are on the same
frequency will not possible until switch-off of analog television.
Re-arrangement of digital television channels after analog switch-off
may also be necessary.
*Number of services that can be provided in the short-term*
Between 5 and 9 services can be provided per multiplex or frequency
block with trade-off between audio quality and/or potential data
capacity and the number of services. Depending upon this choice, the
three VHF Band III and three L-Band frequency block pairs could provide
between 15 and 27 wide-coverage services in each major metropolitan market.
*Regional spectrum availability*
In many regional licence areas, especially those that are geographically
adjacent to major metropolitan areas, there will be little or no readily
available VHF Band III spectrum. Even where there may be apparently
“unused” VHF Band III spectrum in an area, its use may need to be
restricted to very low power levels due to the need to avoid
interference to co-channel
adjacent area television services.
*Regional coverage and alternative technologies*
Although L-Band terrestrial transmitters could in theory be used to
provide digital radio coverage in regional areas (if enough transmitter
sites could be established) serious questions about the economic
practicality of such an approach remain. For that reason it is
recommended that alternative technologies that may be better suited to
the needs of regional Australia should be further studied. Those
alternatives include L-Band satellite and Digital Radio Mondiale (DRM)
technology (at this stage neither of these is sufficiently available to
be recommended as a solution for adoption).
*L-Band satellite spectrum*
It is recommended that 12 MHz of L-Band spectrum should be reserved to
preserve options for the introduction of a satellite digital radio
system until such time as decisions can be taken on the need or
otherwise for such a solution. The band between 1461 and 1473 MHz is
proposed as being the most suitable.
*Spectrum availability in the medium term*
Unless alternative technologies prove viable, services that cannot be
accommodated with the readily available three VHF Band III and three
L-Band frequency blocks would need to be accommodated using either:
additional VHF Band III spectrum; or, additional L-Band spectrum.
Additional VHF Band III spectrum could be provided by: (i) a 1 MHz shift
of channel 10, or; (ii) closure of analog television services. The 1 MHz
shift would provide a relatively small capacity increment (though it
could cater to all current Sydney and Melbourne wide-coverage area
services with 7 services-per-multiplex). The closure of analog
television services is subject to current government policy
consideration and the timing for this is uncertain.
The availability of additional L-Band spectrum is subject to varying
degrees of incumbency by licensed radiocommunication services that
provide point-to-point fixed link services, Defence services and
point-to-multipoint Universal Service Obligation telecommunication
services in regional and remote areas. The report proposes a strategy
that would maximise the ability of incumbent radiocommunications
licensees to continue to use L-Band while providing necessary
opportunities for introduction of broadcasting services.
Clearance of incumbent L-Band services to allow the
replication/migration of broadcasting services into L-Band will impose
costs on incumbent licensees and is likely to be resisted. The
transition process will need to be supported by appropriate regulatory
arrangements (including a revision of the 1.5 GHz Band Plan). Suggested
L-Band arrangements have been described in the report that would allow a
staged introduction of T-DAB while minimising the impact on incumbent
services and preserving the policy option to consider an L-Band
satellite system. An issue that will need careful consideration is the
time-frames within which clearance of incumbent radiocommunication
services would be required. In particular the clearance of some of the
incumbent Defence licences may not be simple or straight-forward.
*Possible strategy for digital radio introduction*
These considerations suggest that a multi-stage process for introduction
of digital radio services may be appropriate.
The first stage involving access to three frequency blocks at VHF Band
III (complimented by infill/coverage extender capacity at L-Band) in
major metropolitan areas could be introduced as soon as appropriate
legislation is passed and necessary regulatory instruments are made or
Depending on the number of services-per-multiplex adopted, those
frequency blocks could provide 15 to 27 wide-coverage services in a
radio licence area. Currently there are 28 and 29 wide-coverage services
operating in the Sydney and Melbourne radio licence areas respectively.
Of those, 18 wide-coverage area services are provided by commercial or
national broadcasters in each radio licence area.
It is clear that at the “first stage”, digital radio capacity cannot be
provided for all currently operating wide coverage and local area
services in Sydney and Melbourne. Capacity could however be provided for
all currently operating wide coverage commercial and national services,
if 6 (or more) services were assigned to each multiplex.
There are more options, and more uncertainty, for the following
stage(s). Key considerations on options for the second (and potentially
subsequent) stages are:
• Availability of additional VHF Band III spectrum depends on closure of
analog VHF Band III television services.
• Clearance of L-Band spectrum will take time and will impose costs on
incumbents. If fixed links within 200 km of metropolitan areas need to
be relocated to other bands the estimated cost could be up to $32
million. Additional costs will be also imposed on non-fixed link licensees.
• Development of alternative technologies (eg. DRM or L-Band satellite)
could shift the planning paradigm (especially in regional areas) toward
L-Band satellite or DRM.
David Boxall | Any given program,
| when running correctly,
| is obsolete.
| --Arthur C. Clarke
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