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Broadcasting is regarded as the simultaneous
distribution of information to a multitude of subscribers ("one
to many"). In radio broadcasting the subscriber receives the information
via an audio signal, whereas in television both an audio signal and a
video signal are received. The further development in analogue radio broadcasting
also allows to transmit additional data. Examples are RDS (Radio Data
System) in radio broadcasting and broadcast videotex in television. The
television standard used in many European countries is PAL ("Phase
Alternation Line").
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| Broadcast videotex is digital information that
is added to the analogue television picture. The page-oriented broadcast
videotext is inserted in the gaps of the transmission of the picture
sequences. |
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| Radio Data System (RDS) uses a free space in
the stereo multiplex signal at 57 kHz. The additional information
is transmitted on an auxiliary carrier at a data rate of 1.2 kbit/s.
RDS enables, among other things, automatic tuning to a selected station.
The basic idea of RDS, i.e. to provide additional information for
mobile reception, is continued in digital audio broadcasting. |
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| The PAL ("Phase Alternation Line")
television standard delivers 625 lines at 25 frames (50 half-frames)
per second, 576 of which carry picture information. Another television
standard is, for example, NTSC. This television standard, which is
widely used in the USA, delivers 525 lines at 30 frames per second. |
Broadcasting is characterised by the following three
groups of functions:
- Production: by means of sound and video recording, programmes are
produced (news, movies, commercials etc.).
- Transmission: the appropriately processed signal is transmitted from
the studio to the radio or TV user via different paths. This transmission
can be carried out via terrestrial transmitters or satellite technology
as well as by using cable networks.
- Reception: to make the distributed signals audible and/or visible,
consumers need appropriate receivers, such as antenna systems, radio
and TV sets as well as additional equipment (decoder, set-top box),
if required.
Basically, three types of distribution can be distinguished in broadcasting:
- Satellite broadcasting: the signals are distributed via broadcasting
satellites. These satellites orbit at a height of approx. 36,000 km
above the equator, i.e. at the same speed as the earth; thus, the broadcasting
satellites are "standing" still above a specific position
on the earth. They receive a data signal from a ground radio station
and, after amplifying or processing this signal, send it back to the
earth. The coverage area thus achieved, also called "footprint",
is much bigger, as compared to terrestrial coverage. Broadcasting satellites
supply parts of continents or entire continents. In Austria, broadcasting
programmes are received, in particular, via the ASTRA and EUTELSAT satellite
systems. For this kind of reception, a satellite receiver ("dish")
is required and, possibly, additional equipment, such as a set-top box.
Furthermore, a decoder is required for decoding those TV programmes
for which the broadcaster has not acquired the broadcasting rights for
the entire coverage area.
- Terrestrial transmission: the signal is distributed via a large number
of transmitters which are located at sites that are suitable in topographical
respect and for radio transmission (similar to the mobile radio communications
network). The terrestrially distributed signal is received by means
of a room or house aerial.
- Cable broadcasting: the broadcasting signal is directly fed into a
cable network. This method is similar to the distribution via a telephone
network. Cable broadcasting is possible only in households that have
a connection socket to the cable network. Cable networks are provided
by different operators. In Austria, there are about 250 cable network
operators. The largest Austrian cable network supplies more than 440,000
households in the capital of Vienna; however, a large number of cable
networks only has a few hundred subscribers.
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| Service area: this is the area which is technically
supplied (terrestrially or via satellite) with broadcasting signals
by a transmitter. The terrestrial coverage area is defined by the
location of the transmitter (topography), by the transmit power and/or
the antenna characteristics of the system and, eventually, by the
number and strength of the interference signals. |
Frequency coordination
(frequency management) is the process which is required to integrate a
newly planned transmitter into an existing transmitter network. It has
to be observed that national and internationally guaranteed rights are
not violated and that no interferences are caused.
When the set-up of the broadcasting networks was started
in the 1960’s and only few transmitters were operative, the coordination
activities were easier insofar as enough frequencies (channels) were still
available for the transmitters to be newly planned. Because of the extreme
density of today’s existing networks, coordination is extremely
difficult, as almost no gaps can be found in the frequency spectrum any
more, despite highly efficient technical methods. With regard to the utilisation
of the frequency spectrum, we are approaching the limits of what is physically
and technically feasible.
Broadcasting frequencies are a scarce resource, as more
and more programme providers have to share a limited part of the frequency
spectrum. It is not possible to expand the spectrum, since other radio
services as well (mobile radio, military and public radio services, radio
relay etc.) have to cope with the shortage of the share of the frequency
spectrum allocated to them.
The entire coordination activities are based on international
conventions and agreements on the European and worldwide levels. Special
reference is made to the conferences on radio broadcasting in Geneva 1984
and on television in Stockholm 1961.
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| The TV frequency scale has different channel
numbers (2 to 69). These channel numbers correspond to specific frequencies
with associated bandwidths. The digital channel 34, for example, corresponds
to a centre frequency of 578 MHz and a bandwidth of 8 MHz. |
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| One technical definition of the term transmission
capacity is limited to the parameters location, radiated power and
frequency, such as Wien 1 - Kahlenberg, 500 kW, centre frequency of
578 MHz (channel 34). |
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In the broadcasting sector, digitisation
has already arrived in many areas, such as in studio engineering, satellite
transmission and, to a limited extent, also in the distribution via cable
networks. Terrestrial transmission, on the other hand, is implemented
in most European countries still according to analogue technology. However,
there is no doubt that, because of the further development of communications
technology that has been under way long since, digital transmission will
be introduced probably in all European countries in the next few years,
eventually replacing the analogue transmission links as from the second
half of this decade.
On the part of the EU, for some time the year 2010 has
been assumed to be the deadline for the final turn-off of the analogue
frequencies. Only recently, on the occasion of the summit of the Council
in Seville 2002, the action plan "eEurope 2005" was adopted,
which stipulates, inter alia, that all member states will have to submit
detailed time schedules for the switchover from analogue to digital transmission
technology in the field of broadcasting.
Against the background of this European scenario, which
has been developing for quite some time, the Austrian legislator laid
down specific provisions under the heading of "digitisation"
in section 6 of the PrTV-G which took effect on 01.08.2001. After tenders
had been invited by the Federal Chancellor, the working group "Digital
Platform Austria" was founded. Its central task is to support the
regulatory authority in working out a digitisation plan, thereby involving
all broadcasters and other affected market players.
The digitisation plan to be prepared shall guarantee
a smooth transition from analogue to digital reception. In this process,
all technical, economic and, also, legal framework conditions shall be
taken into account or newly created. On the one hand, comparable measures
(pilot trials or introduction of DVB-T) in other countries shall serve
as benchmarks, on the other hand, it will be indispensable take account
of the characteristics of the Austrian situation (dual broadcasting system
only under construction, particular shortage of available frequencies,
extremely mountainous country, fierce competition due to successful TV
broadcasters from Germany etc.).
By means of a test operation various technical parameters
shall be tested. In addition, it is intended to examine also the acceptance
of new contents (applications) by the audience (additional offerings,
data services, interactive applications).
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| "Digital Platform Austria" is a working
group that was established by the Federal Chancellor. It supports
KommAustria in working out a plan for the introduction of digital
broadcasting in Austria. |
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DAB (Digital Audio Broadcasting): this is
a process developed and standardised by the EU research initiative
EUREKA for the digital transmission of radio programmes. Besides
improved sound quality, the digital transmission technology also
allows to transmit additional information. So far, the DAB system
has not gained acceptance to the extent expected.
DVB (Digital Video Broadcasting): this is
an international standard for the digital transmission of TV and
radio programmes, as well as various data services. DVB can be distributed
via satellite (DVB-S), cable (DVB-C) or also via terrestrial transmitters
(DVB-T). In addition to improved receive quality and the possible
"taking along" of additional services, the more efficient
usage of the frequency spectrum is an advantage of DVB.
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This term refers to the migration
from analogue to digital broadcasting. Due to the shortage of frequencies,
analogue and digital transmission in full configuration is not possible
in parallel. Therefore, the digital transmission technology has
to be set up step by step, while the analogue technology is being
maintained (simulcast phase). Only when the highest possible degree
of coverage by means of DVB-T has been reached, turn-off of analogue
transmission can be considered. The simulcast operation will end
with the switchover (also called ATO = Analogue Turn Off). In the
simulcast phase consumers will be given the opportunity to replace
their equipment (set-top boxes or digital TV sets) during reasonable
periods of time. |
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| This technical equipment allows to receive digital
signals and make them visible on analogue TV receivers (DVB). The
TV set itself can also assume the function of the set-top box, provided
the required modules are integrated. |
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Basically, "free to air" and
"pay TV" are distinguished in the reception of broadcasts.
"Free to air" reception means that any technically functioning
receiver can present the broadcasting signal correctly. No additional
charges are incurred, the signal is not encoded. In the case of
"pay TV", there is a defined user group and only authorised
users can present the received broadcasting signals correctly. The
data stream, which is encoded before it is sent out, is decoded
at the receiver by means of a smart card. Simultaneous decoding
of several programmes (programme bouquet) depends on the content
provider.
In summary, CA refers to commercial and technical system components
that serve the purpose of making a signal visible and audible to
those users who are given the corresponding authorisation by the
programme provider (e.g. pay TV).
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| A programme bouquet is an arrangement of different
programmes of one or several programme providers. |
| EPG (Electronic Program
Guide)/Navigator |
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| A digital TV channel can transmit several programmes.
Although this is an essential advantage, compared to analogue TV,
it also creates a great number of programmes. The EGP/Navigator provides
for orientation, with regard to the individual programmes, by offering
additional information. In the set-top box, this additional information
is separated from the programme contents again. So, the EGP, in a
similar way as a programme journal, guides through the variety of
programmes and provides background information. |
| MHP (Multimedia Home Platform) |
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| The MHP system developed by European industry
shall be used by all programme providers, terminal equipment manufacturers
and network operators as uniform standard and common basis for interactive
additional applications. |
| Multiplexing and Multiplexing Platform |
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Multiplexing: this term refers to the process,
which is typical of digital transmission, where the different video,
audio and data signals are compiled into a common data stream which
is transmitted via satellite, cable or terrestrial antenna to the
terminal equipment. In the digital TV set the received data stream
is split up into its individual components again ("demultiplexing").
The term "multiplexer" refers to the actual technical
device.
Multiplexing platform: this refers to the technical infrastructure
for merging and distributing the programmes and additional services
compiled in a digital data stream. |
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