1、 Report ITU-R BS.2144(05/2009)Planning parameters and coveragefor Digital Radio Mondiale (DRM) broadcasting at frequenciesbelow 30 MHz BS SeriesBroadcasting service (sound)ii Rep. ITU-R BS.2144 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and eco
2、nomical use of the radio-frequency spectrum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed b
3、y World and Regional Radiocommunication Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be u
4、sed for the submission of patent statements and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. S
5、eries of ITU-R Reports (Also available online at http:/www.itu.int/publ/R-REP/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodeterminati
6、on, amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management Note: This ITU-R Report was approved in
7、 English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2009 ITU 2009 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written permission of ITU. Rep. ITU-R BS.2144 1 REPORT ITU-R BS.2144 Plann
8、ing parameters and coverage for Digital Radio Mondiale (DRM) broadcasting at frequencies below 30 MHz (2009) Introduction Countries around the world are in the process of migrating from analogue to digital broadcasting techniques for both television and radio. This Report looks at sound broadcasting
9、 in the bands below 30 MHz. It briefly examines the underlying reasons for the migration and looks at the technologies involved. Its focus is the DRM system as developed for use in the LF, MF and HF bands. The Report is intended to: Explain why and how a broadcaster might go digital. Be a reference
10、technical document for DRM planning. Provide new information based on the practical experience in DRM. TABLE OF CONTENTS Page Introduction 1 1 Objectives . 4 1.1 Why digital? Technical considerations . 4 1.2 Why digital? Commercial and operational considerations 4 1.3 How digital? Technical and oper
11、ational considerations 4 1.4 How digital? Commercial considerations . 5 2 DRM system aspects 6 2.1 Key features of the system design 6 2.2 Audio coding guidelines . 7 2.3 Transmission modes and data rates 9 2.3.1 DRM robustness modes . 9 2.3.2 Spectrum occupancy types. 10 2.3.3 DRM theoretical data
12、rates 10 3 Modification of transmitters and antennas . 12 3.1 Principles of modifying existing transmitters conversion to digital 13 3.2 Converting different types of transmitter to DRM . 14 2 Rep. ITU-R BS.2144 Page 3.3 Coverage efficiency 15 3.4 The experience of Vatican Radio 15 3.4.1 Modern soli
13、d-state MW transmitter. 15 3.4.2 PDM SW transmitter 15 3.4.3 First-generation (GTO) PSM MW transmitter. 16 3.4.4 Modern PSM (IGBT) SW transmitter 16 3.5 Spectrum mask 16 3.6 Antenna constraints 17 4 Coverage and frequency planning 18 4.1 Introduction. 18 4.1.1 Minimum usable field strength 18 4.1.2
14、Protection criteria. 19 4.2 LF/MF bands 20 4.2.1 Frequency bands allocated to LF and MF sound broadcasting 20 4.2.2 Coverage 21 4.2.3 Propagation 25 4.2.4 Frequency choice and coordination . 29 4.2.5 Reception . 29 4.2.6 Planning software. 31 4.3 HF band 31 4.3.1 Coverage 31 4.3.2 Protection ratios
15、. 32 4.3.3 Propagation 32 4.3.4 Frequency choice and coordination . 33 4.3.5 Reception . 35 4.3.6 Planning software. 35 4.4 Required S/N ratios for DRM reception . 36 4.5 Minimum usable field-strength values for planning. 36 4.5.1 Procedure for estimation of the minimum usable field strength 36 4.5.
16、2 Computation of minimum usable field strength 36 4.5.3 Feedback from field tests . 39 4.6 RF protection ratios 40 4.6.1 Relative protection ratios . 40 4.6.2 Values of relative protection ratios 42 4.6.3 RF protection ratios used for HF coordination 47 4.6.4 RF power reduction for DRM 49 Rep. ITU-R
17、 BS.2144 3 Page 4.7 The specific case of the 26 MHz band 50 4.8 Simulcast. 51 4.9 NVIS . 52 4.10 Example of SFN use in Broadcasting below 30 MHz 53 4.10.1 System setup 53 4.10.2 Stand-alone versus SFN transmitter operation. 55 4.10.3 Long-term test 56 4.10.4 Conclusion . 56 5 International regulatio
18、ns. 56 5.1 The planning process: assignment planning for LF/MF. 56 5.1.1 Special study regarding the use of digital modulation in the LF and MF bands governed by the Regional Agreements GE75, RJ81 and RJ88 . 56 5.1.2 Regulatory considerations 57 5.1.3 Regional Agreement GE75 57 5.1.4 Regional Agreem
19、ent RJ81 . 62 5.1.5 Regional Agreement RJ88 . 62 5.2 Coordination for HF . 63 5.2.1 The HFBC framework . 63 5.2.2 The RR Article 12 procedure . 63 6 Conclusions 63 6.1 DRM is already operational 63 6.2 Technical and regulatory information related to DRM services coverage planning that are compiled i
20、n this text 64 6.3 Feedback from operational and experimental transmissions is available. 64 6.4 And next . 65 7 List of terms (abbreviations). 65 References 67 Annex 1 Required S/N values for DRM reception 67 Annex 2 Information related to RF protection ratios 72 Annex 3 Results of some DRM trials
21、. 80 Annex 4 RMS modulation depth 94 Annex 5 DRM facilities and transmissions operated by European Broadcasters. 96 4 Rep. ITU-R BS.2144 1 Objectives 1.1 Why digital? Technical considerations A primary benefit of digitalization is greater control over channel performance. The overall performance of
22、an analogue communications channel is dictated largely by the characteristics of the channel itself. The scope for exploiting the “trade-offs” implicit in Shannons Theorem Shannon, 1949 is limited. By contrast, the overall performance of digital systems is largely governed by the quality of the conv
23、ersion processes (analogue to digital and vice versa) provided that the capabilities of the channel are not exceeded. There is much greater scope for exploiting the “Shannon trade-offs”, particularly if error correction techniques are used. In effect, the performance of analogue systems tends to det
24、eriorate as the channel performance deteriorates while digital systems remain as defined by the conversion processes until they fail completely. Unfortunately, this means that the subjective effects of channel performance on digital systems can be much more obtrusive when working close to the ultima
25、te channel capacity. Of seminal importance is the ability of digital systems to compress data into a smaller space. In the broadcasting context this means the use of compression coding techniques which allow much higher sound quality to be accommodated in the same channel bandwidth. A related benefi
26、t is the ability to trade between quality (which is dictated primarily by the degree of compression) and ruggedness more or less at will. Further to this digital systems offer additional benefits. Firstly, the relatively easy addition of ancillary data services allows such features as automatic or s
27、emi automatic tuning, conditional access and the inclusion of supplementary (or even completely unrelated) data streams. Secondly, digital broadcasting techniques can offer credible “single frequency networks”. This in its turn makes for even more efficient use of available spectrum, potentially ope
28、ning the door to more audience choice. 1.2 Why digital? Commercial and operational considerations As already stated, the major commercial advantage of digital broadcasting is the ability to offer higher quality and diversity of services. Since this can be done without the need for additional spectru
29、m and with lower transmitter power this is attractive from the broadcasters perspective. New commercial opportunities will exist. The more consistent subjective quality can be a benefit to both providers and users, as can the ancillary services like automatic re-tuning of a receiver. There are, howe
30、ver, commercial drawbacks. For any individual broadcaster there is the cost of re-equipping and it is unlikely that this will be offset by increased revenue (advertising or subsidy). Persuading the audience to invest in new receivers is of fundamental importance to the venture. This cannot be stress
31、ed too highly and to do it, it is necessary either to offer a wider range of high quality programming or threaten to discontinue the analogue service. 1.3 How digital? Technical and operational considerations There is little compatibility between digital and analogue broadcast transmission systems.
32、While this can cause some transition problems it is generally advantageous because the digital systems have been optimized against their own technical and financial drivers and are not compromised by having to be compatible with less advanced existing technologies. A limiting consideration with the
33、familiar Zenith GE system for stereo radio was that it had to be backward compatible with existing mono FM receivers. Rep. ITU-R BS.2144 5 Any technical switchover strategy must work within certain commercial and regulatory imperatives. In essence any transition strategy will probably demand the con
34、tinued availability of analogue versions of existing programme streams until a high proportion of the audience is able to receive the digital services by one delivery means or another (satellite, cable or terrestrial broadcast). Typically, this will mean that digital and analogue versions of the sam
35、e programmes are broadcast simultaneously during the transition period. Various technical strategies can be and have been deployed to achieve this (e.g. simulcast). With DRM, where the digital transmission can be made to occupy the same amount of spectrum and have the same interference impact as an
36、analogue signal, it is possible simply to replace an existing analogue service with a digital one or to use an existing, unused allocation. In most bands there are few unused allocations and so this strategy relies on the existence of broadcasters who simultaneously transmit the same material on dif
37、ferent channels (or even platforms) and are prepared to risk one (the smaller) audience re-tuning to the other frequency. This strategy is currently being used in the AM bands. In the HF bands there is less of a problem because there is free allocation of channels through the various coordinating bo
38、dies. There are however, still problems with congestion in the lower frequency HF bands. 1.4 How digital? Commercial considerations It seems unlikely that there has been or will be any pressure from the audience to introduce digital services for their own sake. Audience take up is driven much more b
39、y the potential benefits: the availability of a wider range of services; improved formats such as stereo in the “AM bands”; improved and more consistent sound quality; programme associated data, metadata or even independent services like web pages; easier selection of programming e.g. automatic swit
40、ching between different LF, MF and HF; transmitters or electronic programme guides. These must be traded against the perceived cost of new equipment. It is essential therefore that the audience is presented with an attractive package of services and receivers at prices it is prepared to pay. The dri
41、vers for the industry are therefore the production of more and increasingly attractive programme content and the deployment of receivers at appropriate prices. The importance of programme content, while outside the scope of this report, cannot be stressed too highly. Receiver price is driven by a nu
42、mber of factors, not least the willingness of the broadcaster or regulator to subsidies the cost in order to promote sales and uptake of the service. Any switch over strategy must recognize that, the user community can generally be divided in three in its willingness to invest in new technology. The
43、 “early adopters” tend to be enthusiastic about technological development and will invest in new machinery simply in order to have it at an early stage. Such people will typically be prepared to pay a high price for new equipment. In the early stages of product life, the manufacturers rely on this c
44、ommunity to offset some of the high development costs of new consumer equipment. The early adopters are followed by the “mainstream”. These users will be much more circumspect about price and will compare the value they put on the new service with the cost of making the change before actually buying
45、 a new receiver, These people know that they intend to make the change but do so when the cost of the receiver has dropped (as it inevitably will) to the level they are prepared to pay. This is the most important group in driving the changeover. 6 Rep. ITU-R BS.2144 The third group, the “unwilling”
46、have typically decided that they will never change or they have sufficiently little interest in the subject that they are unaware of the development. These people will only change when they absolutely have to (perhaps because the analogue service is withdrawn) or when the price becomes so low that i
47、t is not important and digital has anyway become the standard. This simplistic model of the market is clearly going to be distorted by factors such as subsidies and the threat of discontinuing the analogue services. The threat of discontinuation is a (market) driver that must be used with extreme ca
48、ution. Public service broadcasters as well as the advertisers who fund a large part of the broadcasting industry will not be pleased to find themselves “cut off” from an established audience if “switch off” is contemplated before a substantial proportion of it is able to receive the new service. The
49、 community of broadcasters will be unwilling to turn any of their services off before the audience drops to the point where the transmission cost is not viable. One thing can be stated with certainty. Continued technical development and an ever-expanding consumer base will mean that the cost of producing receivers will fall. This in turn will push down the purchase price. Continuous development in the integrated technology IT sector means that systems of ever-greater complexity can be accommodated on small silicon chipsets. Receivers wi
