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A Digital Television and Radio Future?
Matthew James
Science, Technology, Environment and Resources Group
New Digital Technology
Black and white TV, AM radio, colour TV, FM radio, stereo TV, shortwave
radio, large screen TV and flat screen TV: Australians seem to be willing
consumers of new versions of electronic entertainment technology. Presumably,
they will want to avail themselves of the next generation of digital television
and audio radio services.
While all of the previously mentioned technologies involve analogue
or actual radiofrequency wave signals, digital systems utilise computer-produced
and discrete codes. Such signals allow for computer manipulation to provide
for greater spectrum efficiency, processing and signal quality. Digital
transmission converts sound, image, text and data all into the same code.
However, it does require the purchase and use of new receivers as well
as new transmitters.
Digital services may well use radiofrequency spectrum currently used
for analogue services. The effects on and future of those services deserve
consideration, such as the costs to broadcasters and audiences. Industry
sectors - community, commercial and national, all seek a part of the new
digital technology. However, with digital radio receivers now costing
$1000 each, the timing is uncertain for introduction of services.
Radio
Digital radio is capable of worldwide broadcast of compact-disk-quality
sound, along with a variety of data services. The technology enables minimal
interference or signal fading. While listening to an audio radio program,
users may ascertain a music title by scanning the radio monitor display.
While travelling, the digital radio will automatically tune to the same
program on a stronger frequency. The user can set the radio to have travel
news interrupt the normal programs, or to select specific music types.
This service already operates in Britain. Digital radio also allows pay-per-listen
program choices along with advertising request lists, weather details
or map information.
Several proprietary systems are under test overseas. They include the
European Eureka 147, AT&T Amati, USA Digital Radio and VOA/JPL plus
Japanese systems. Eureka 147 is a patented transmission system called
coded orthogonal frequency digital multiplexing that splits the signal
into many separate data streams on closely spaced radio frequencies. The
'L' Band (0.39 to 1550MHz) spectrum should be able to accommodate parts
of digital radio. Each existing analogue channel could hold 6 digital
channels, allowing for additional channels from elsewhere, plus smaller
antennae and lower transmission costs. The technology also permits a national
service on one frequency channel.
A digital radio trial with 9 stations began in Melbourne in January.
This involves Telstra using Eureka 147 for three ABC stations, one SBS
and one community radio station. Trials of regional satellite service
delivery are also due. Early services may well exist alongside AM and
FM analogue services. Pay radio services offering some 30 channels may
also arise. Australians now have 29 million radio receivers but very few
could be used for digital services. Consumers must buy new equipment if
and when digital radio services commence.
Television
Digital television will squeeze many channels into the space that one
takes now, but it also requires completely new receivers and transmitting
equipment. Some 20 terrestrial channels and 60 satellite channels per
existing channel seem quite possible, but with lower quality than for
analogue services. High definition pictures may be possible using one
existing channel. Some services may start here before 2000, but a period
of joint analogue and digital services will most likely apply. A digital
set-top box could convert signals for old televisions, but technical standards
still await selection. The Optus satellites can provide some 5 television
channels per transponder, using video picture digital compression. Note
that Parliament's Sound and Vision Office can not receive signals from
digital Asian satellites.
With digital technology, picture quality should improve and allow wide-screen
images and ancillary data services. Europe's Digital Video Broadcasting
project group has studied technical standards for terrestrial digital
television. Other groups working on standard developments include DAVIC,
IEEE, Cablelabs and the Standards Australia Digital Video Standards Task
Group, plus those for high definition television.
The Australian Broadcasting Authority released a discussion paper titled
'Digital Terrestrial Television Broadcasting in Australia' in 1995. It
suggests that service introduction would need to suit market demand and
technical developments. The report favours an allowance for existing broadcaster
access to early digital channels, according to the cost, quality and quantity
of service. A mix of existing channel bands may be necessary. Broadcasting
nationally on a single channel is more complicated than using a number
of channels. Links with pay television technology would best serve consumers.
However, the major difficulty seems to be one of providing content for
all of the different new television channels. This has caused problems
in Britain.
Future developments may include three-dimensional television without
the need for special viewing glasses. However, questions remain as to
whether broadcasting industry and society can afford the new digital technologies,
by when, and how regulatory arrangements should best apply. Many such
issues are unresolved.
The British Experience
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| A mature, installed technology may well outlast a new technically
superior one. Early efforts to establish a European high definition
television standard failed when industry disagreed. In Britain, research
found that certain unused analogue channels were suitable for digital
use without causing any interference. However, the use of channels
by new broadcasters is still unclear.
Competition arose between existing analogue broadcasters who proposed
to provide digital services and proponents of a new independent
broadcaster. In the event, the British Government recently decided
to allocate six new digital data streams, each with at least three
channels, under new controls. These will link viewers to broadcasters,
through agencies termed 'multiplexers'. The existing broadcasters
may only use one channel each, which has led to industry friction
over content and multiplexer controls.
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