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In the past decades, traditional television broadcasting has been an autonomous field which was largely independent of the world of telecommunications and computers. The analog television standards PAL, SECAM and NTSC have remained almost untouched with regard to their picture information. Whatever development took place was essentially in support of programming and was based on the existence of a certain redundancy in the representation of the signal in the time and fre­ quency domain. In the 70S, for example, the teletext system was introduced throughout Europe. A further supplementary digital service in television, intro­ duced in the early 80S, was the Video Programme System (VPS) which utilizes part of the TV data line and ensures that programmes can be recorded with the correct timing on video recorders even when the programmes are delayed. There is no doubt that as far as the transmission from the studio to the view­ er is concerned, the future belongs to digital video broadcasting (DVB) which is about to be implemented in the satellite, cable and terrestrial radio transmission media. The European DVB Project finalized its specification for channel coding and modulation for the digital broadband transmission channels at the begin­ ning of 1996.

Inhaltsverzeichnis

Frontmatter

1. History of the Development of Digital Transmission Techniques in TV Broadcasting

Abstract
The history of development in TV broadcasting has been characterized by the increasing part digital signal transmission has played since the introduction of colour television in 1967. Supplementary and value-added services were introduced and then digital audio techniques were specified and partially implemented. To achieve the digitization of the television image, however, it was necessary for a number of driving forces to combine synergetically:
  • the (original) motivation for introducing high-definition television (HDTV)
  • the revolutionary advances in microelectronics integration (DSP-Digital Signal Processing), and
  • the results of research in psychooptics, utilized in data compression of the source signals.
Paul Dambacher

2. Present State of the Terrestrial Television Broadcasting Service

Abstract
In this section, the relevant state of the art is set forth for:
  • the programme feed to the transmitting stations
  • mixed analog and digital signal transmission and
  • the terrestrial television transmitters.
Paul Dambacher

3. Basic Principles of Digital Television Transmission

Abstract
This section explains the basic principles of terrestrial digital television transmission. It is divided into a first part which deals with the video and audio encoding and the MPEG-2 transport stream. This part also applies to the other technical media of satellite (for direct reception) and cable and will certainly also apply completely to other future paths (e.g. ADSL — Asynchronous Digital Subscriber Line and MMDS — Microwave Multipoint Distribution System).
Paul Dambacher

4. Basic Parameters of the Specification for the Digital Terrestrial TV Transmission

Abstract
In the following section, the basic parameters of the specification for the coding and modulation for the terrestrial channel are represented. The first parts of the channel coding, the energy dispersal, the outer and inner coders and the outer interleaver have been adopted from the satellite standard. For the inner interleaver and all parameters associated with the OFDM modulation, the 8K/2K QAM specification [4.7] was available at the end of 1995. It is the result of combining two draft specifications 8K/QAM [4.1, 4.2] and 2K/DAPSK [4.4]. The two drafts differ in the following basic parameters:
In 8K/QAM with an FFT length of 8K, the number of carriers is 6785. The active symbol period TU = 896 μs results in guard intervals △l = 1/4 TU, △2 = 1/8 TU and △3 = 1/32 TU. The carrier modulation defined is QPSK,16 QAM and 64 QAM as well as 16 MR (Multi-Resolution) and 64 MR QAM for hierarchical coding/modulation. The OFDM frame contains 96 symbols including the zero symbol, the CAZAC/M (Constant Amplitude Zero Auto Correlation with M sequences) symbol and the TPS (Transmission Parameter Signalling) symbol. In addition, continual and boosted pilots are inserted.
Paul Dambacher

5. Programme Feeds to the Digital Terrestrial Transmitting Stations

Abstract
Satellites are considered to be the best solution as a means for feeding terrestrial single-frequency networks both from the point of view of technology and of economics. Alternative solutions are microwave and fibre-optical links. The tasks are the same or similar, especially with respect to bit-synchronous radiation, but in the case of switched networks, for example having ATM-type structures, the requirements are higher.
Paul Dambacher

6. Technology of Terrestrial DVB Transmitters

Abstract
To prepare field and pilot trials which, in particular, involve service areas with single-frequency networks, DVB transmitters are needed which are not yet available as a commercial product. These transmitters, therefore, use modified existing technology, particularly with respect to the power amplifier. This chapter discusses the adaptation and correction of the tetrode and solid-state amplifiers from analog television for OFDM signals. In addition, preliminary investigations are carried out regarding the development of the OFDM modulator in accordance with the DVB-T specification and for antenna patterns in accordance with new optimization criteria. This also includes an approach to implementing a digital I/Q modulator.
Paul Dambacher

7. Test Methods for the Digital Terrestrial Television Transmitter

Abstract
In analog television transmitter testing, the essential video parameters are related to the frequency domain (amplitude, phase and delay/frequency response) and to the time domain (linear distortions (e.g. pulse tilt, streaking) and nonlinear distortions (e.g. differential amplitude and phase)).
Paul Dambacher

8. Synchronization of the DVB Transmitters in a Single-Frequency Network

Abstract
The fact that the digital terrestrial television transmitters are capable of operating at a single common frequency certainly has significant advantages:
  • economic use of the frequency resource
  • power economy due to the addition of the field strengths of adjacent DVB transmitters and of multi-path signals
  • reliability of coverage in difficult terrain.
Paul Dambacher

9. Techniques of Measuring the Coverage of Digital Terrestrial Television Networks

Abstract
Programmes for protecting the field strength are available as tools for planning coverage. However, the results exhibit relatively high uncertainties since these tools only use very coarse models. To compensate for the uncertainties it would be conceivable to increase the transmitting power or the number of transmitter sites but this is not practicable.
Paul Dambacher

10. Outlook

Abstract
In any assessment of the future development of digital terrestrial television broadcasting, the status and interdependence with the other technical media currently operated and the specific penetration profiles must be discussed. Table 10.1-1 shows the status of the absolute and relative figures of TV households in Europe connected to terrestrial TV, to satellites and to cable, the number of inhabitants per country being provided as additional information. The excerpts below show that the situation is heterogeneous: 98% of Belgium and 92% of the Netherlands are connected to cable but national terrestrial transmitter networks are being operated mainly for programme distribution to cable headstations.
Paul Dambacher

11. Summary

Abstract
Digital terrestrial television broadcasting originated in the United States, with the quite revolutionary claim (for 1990) to be able to transmit high-definition television within the standard American 6-MHz channel. After 1991, separate research projects and pilot developments arose in Europe.
Paul Dambacher

Backmatter

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