Digital Dividend
The introduction of digital terrestrial broadcasting, which is underway in many
parts of the world, provides many benefits, among which is the professed ‘digital
dividend’. Digital compression technology and coding systems allow for
several television programme channels to be carried within the same bandwidth
that is used by an analogue television channel. Digital terrestrial
television (DTT) delivers an increasing number of quality television
programmes within the same amount of spectrum that is used by an analogue
channel and uses spectrum more efficiently.
So as television broadcasting migrates from analogue to digital, it is clear
that all existing analogue television channels can be accommodated in less
spectrum than used previously and many additional television
channels can be introduced in the available broadcasting spectrum. One might say
that some spectrum may be released after the analogue TV services have closed
down. This release of spectrum is referred to as the ‘digital dividend’.
This released spectrum could be used for many purposes, such as:
-
providing many more digital television broadcasting
services
of conventional quality and resolution;
-
providing a new service concept (partially or totally)
that allows for indoor,
portable and mobile reception including digital TV services for reception
on hand-held receivers;
-
providing enhanced sound and picture quality, like High
Definition TV,
Three-Dimensional TV;
-
providing non-broadcasting services, like
IMT, WiMAX, Wifi, etc.
It is anticipated that this 'digital dividend' is
likely be used by the Member States for various purposes reflecting their
political, social, and cultural considerations. Already, the digital dividend
has resulted in the availability of some of the broadcasting spectrum in the UHF
band in Region 1 - specifically from 790- 862 MHz, for mobile broadcasting on a
primary basis from 17 June 2015. Furthermore, Agenda item 1.17 of the
2012 World Radiocommunication Conference (WRC-12) tasks the ITU-R Sector to
consider results of sharing studies between the mobile service and other
services in the band 790-862 MHz in Regions 1 and 3, in accordance with
Resolution 749 (WRC-07)
- to ensure the adequate protection of services to which this frequency band is
allocated, and to take appropriate action to assure this.
ITU-R Joint Task Group 5-6 (JTG
5-6) - 'Studies on the use of the band 790-862 MHz by mobile applications
and by other services' was established by the first session of the
Conference Preparatory Meeting (CPM
11-1) in order to carry out these studies and to develop the text for the 'Draft
CPM Report on Agenda item 1.17 (WRC-12)'. The
JTG 5-6 completed its work
at the meeting held from 30 April – 7 May 2010.
White spaces
Another aspect of the switch-over to digital terrestrial television broadcasting
is the thorough review of the UHF broadcasting spectrum that is taking
place in Administrations undertaking this transition. The terrestrial TV
networks in the UHF bands have been traditionally planned as Multi-Frequency
Networks (MFNs), in order to support regional TV planning and to facilitate
international frequency coordination. In this type of planning, there are
locations within a country where particular UHF channels are not used in order
to avoid interference to TV services in adjacent regions. These channels are
known as UHF white space and have been used by the broadcasters for
low-power applications like radio microphones and wireless in-ear monitors,
known as Programme Making and Special Events (PMSE) applications. This
sharing of the broadcasting spectrum is the subject of many ITU-R
Recommendations (ITU-R
BT.1368 - 'Planning criteria for digital terrestrial television services
in the VHF/UHF bands' and
ITU-R BS.1786
- 'Criterion to assess the impact of interference to the terrestrial
broadcasting service (BS)', etc.) which provide the necessary criteria for
the interference-free operation of such equipment. |
There is now a demand for this UHF white space (spectrum) by fixed and mobile
devices, which are looking to deliver improved Wifi systems for mobile broadband
and for multimedia streaming in the home. These devices are based on a
combination of spectrum sensing (Cognitive Radio - CR) and
geolocation (database of locally “unused” channels in an area) techniques.
CR technology is under study in
WRC-12 Agenda item 1.19. The broadcasting community is particularly uneasy
about the impact that these ubiquitous devices could have on TV reception in the
home. The CR process is difficult and requires high performance Radio
Frequency (RF) circuitry and potentially complex signal processing as the
licensed Digital terrestrial television (DTT) signal to be detected will
be received at a very low level. In addition, the database to be developed and
maintained for the geolocation poses many questions as to its accuracy,
timeliness and reliability. In addition to the broadcasters who are affected by
the use of large numbers of such unlicensed devices, the cable industry have
pronounced concerns by the ingress of these signals into cables (which have no
white spaces).
Power Line Telecommunication (PLT) system
PLT system is a communication system which uses the electrical
infrastructure wiring to transfer high-frequency data signals from place to
place. It is superimposed on electrical wiring that is used within the house or
office, from power sockets to all spurs or branches that go to the light
fittings, ceiling/wall outlets, etc. In some countries this technique is
referred to as 'Broadband over Powerline (BPL)'.
As electrical wiring is not designed or engineered for the transmission of wide
bandwidth data, radiation from the wiring is a consequence. So PLT systems
will increase the level of ambient noise at locations where they operate; and
radiation from such unlicensed devices will impact the potential performance of
any broadcast receiver (or any other licensed/authorized service) operating at
that location.
The ITU-R Sector has been studying the impact of PLT on
radiocommunication services and in 2009 published
Report ITU-R
SM.2158 - 'Impact of power line telecommunication systems on
radiocommunication systems operating in the LF, MF, HF and VHF bands below 80
MHz'.
Initially PLT systems operated in the frequency bands below
80 MHz and consequently Report ITU-R SM.2158 focused on these bands. However,
developments in PLT technology have extended the frequency of PLT operation
beyond 300 MHz. Further studies are thus required to investigate the effect of
PLT in the VHF broadcasting bands up to at least 230 MHz (i.e. the top of the
VHF broadcasting bands).
ITU-R Study Group 6
(Broadcasting service) is actively studying the
above-mentioned areas by undertaking tests and measurement programmes and is
developing pertinent
Reports and
Recommendations.
For more information:
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