1、 Report ITU-R RA.2195(10/2010)The transition to digital television andits impact on the unprotected use by the radio astronomy service of bands used for terrestrial television broadcastingRA SeriesRadio astronomyii Rep. ITU-R RA.2195 Foreword The role of the Radiocommunication Sector is to ensure th
2、e rational, equitable, efficient and economical 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 R
3、adiocommunication Sector are performed by 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 Anne
4、x 1 of Resolution ITU-R 1. Forms to be used 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 i
5、nformation database can also be found. Series 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
6、Fixed service M Mobile, radiodetermination, amateur and related satellite services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service syst
7、ems SM Spectrum management Note: This ITU-R Report was approved in English by the Study Group under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2011 ITU 2011 All rights reserved. No part of this publication may be reproduced, by any means whatsoever, without written
8、permission of ITU. Rep. ITU-R RA.2195 1 REPORT ITU-R RA.2195 The transition to digital television and its impact on the unprotected use by the radio astronomy service of bands used for terrestrial television broadcasting (2010) TABLE OF CONTENTS Page 1 Introduction 2 Annex 1 Transition from analogue
9、 to digital television broadcasting 4 1 Australia . 4 1.1 Date of transition 4 1.2 Frequency allocations and assignments 4 1.3 Transmission spectrum mask and the maximum permitted power level of spurious emission or unwanted emission . 4 1.4 Radio astronomy observations in frequency bands allocated
10、to terrestrial broadcasting 8 2 Brazil 8 2.1 Brazilian DTT standard 8 2.2 Date of transition 8 2.3 Frequency allocations and assignments 9 2.4 Current situation of digital terrestrial television deployment in Brazil 9 3 Japan . 10 3.1 Date of transition 10 3.2 Frequency allocations and assignments 1
11、0 3.3 Transmission spectrum mask and the maximum permitted power level of spurious emission or unwanted emission . 10 3.4 Radio astronomy station in the frequency range between 470 and 710 MHz 13 4 United States of America 13 4.1 Date of transition 13 4.2 Changes to frequency allocations . 13 4.3 Ch
12、anges to allotments and assignments . 15 4.4 Changes to allowed transmit power and unwanted emissions 17 4.5 Changes to the spectrum of the transmitted signal . 18 2 Rep. ITU-R RA.2195 1 Introduction Television has become a fundamental form of communication in every region of the world. Its utility
13、as a source of news, entertainment, and emergency information has been evident since its inception more than 60 years ago. Presently providing coverage to a global population numbering in the billions, terrestrial television broadcasting is one of the most ubiquitous uses of the radio spectrum. The
14、radio astronomy service does not share any allocations with terrestrial television broadcasting; however, such broadcasts generally occupy spectrum that is extremely important to low-frequency astrophysics and the observation of red shifted neutral hydrogen (HI) arising from early epochs in the form
15、ation of the universe. To date, radio astronomers have made use of TV bands to conduct observations, in accordance with No. 4.4 of the Radio Regulations (RR). At the present time, many countries are transitioning from analogue to digital television broadcast standards (see Fig. 1), and some are also
16、 revising their broadcast allocations to recover spectrum that is expected to be freed up by the so-called “digital dividend”. Some aspects of the digital transition are expected to result in a reduction in the ability of radio astronomers to make use of the terrestrial television broadcast bands fo
17、r observations that are currently conducted on an unprotected basis (see Fig. 2). Some aspects may improve the ability to make passive observations in the TV bands. FIGURE 1 Distribution of planned digital TV transition, by technology. Areas in gray have no current plans for digital TV transition DV
18、B/TATSCISDB-TDMB-T/HAssessing multiple standardsRep. ITU-R RA.2195 3 FIGURE 2 An example of the impact of digital TV signals compared to analogue TV. The spectra were obtained at a radio astronomy site during a brief period of highly enhanced propagation. The TV signals are originating from approxim
19、ately 290 km away. The digital signal from 181-188 MHz “fills” the spectrum much more substantially than the analogue TV signals occupying 174-181, 188-195, and 195-202 MHz, whose spectra are concentrated in discrete video, chrominance, and audio carriers Annex 1 summarizes the plans for the transit
20、ion to digital television for several countries around the world with current radio astronomy programmes operating within bands used for terrestrial television broadcasting, and for countries of strategic importance to future radio astronomy stations presently under design and development that inten
21、d to utilize such bands. The impact of service rules for digital television on the use of the television broadcast bands for radio astronomy is discussed. The material in this report is specific to the impact of the digital transition on the radio astronomy service. A more general introduction to th
22、e transition to digital TV is available in Report ITU-R BT.2140 Transition from analogue to digital terrestrial broadcasting. 4 Rep. ITU-R RA.2195 Annex 1 Transition from analogue to digital television broadcasting The following sections summarize those aspects of the transition to digital televisio
23、n that may impact the opportunistic use of the television broadcast bands for radio astronomy. 1 Australia 1.1 Date of transition The Australian Government has announced a programme to switchover from analogue to digital transmissions and that it will be “completing the switchover by 31 December 201
24、3”. 1.2 Frequency allocations and assignments In the Australian Radiofrequency Spectrum Plan (ARSP) VHF bands I (45-70 MHz), II (85-108 MHz) and III (137-144/174-230 MHz) as well as UHF bands IV (520-582 MHz) and V (582-820 MHz) have a primary allocation to the broadcasting service. Digital televisi
25、on has been planned for operation within existing allocated broadcasting services bands in bands III (174-230 MHz), IV (526-582 MHz) and V (582-820 MHz). Australian terrestrial television broadcasting services have been planned on a 7 MHz channel raster in both VHF and UHF bands. 1.3 Transmission sp
26、ectrum mask and the maximum permitted power level of spurious emission or unwanted emission Technical aspects of the planning and protection of the broadcasting service are based upon information contained in Recommendation ITU-R BT.1368 (for digital systems) and Recommendation ITU-R BT.470 (for ana
27、logue systems). Further details are contained in the Australian Communications and Media Authoritys (ACMA) Broadcasting Services (Technical Planning) Guidelines 20071. These guidelines are supplemented by more detailed information contained in the ACMA DTTB Planning Handbook2. A summary of differenc
28、es between the Australian digital terrestrial television service planning assumptions and the data contained in Recommendation ITU-R BT.1368 are as follows. Australian planning for both analogue and digital terrestrial television is based on an assumption of fixed reception using outdoor receiving a
29、ntennas. Therefore protection ratios relevant to Ricean channels are used where available. The DVB-T mode 64-QAM with 2/3 FEC and a 1/8 guard interval has been adopted as the basis for digital television planning, however to achieve a higher picture quality for SD/HD simulcast, a number of broadcast
30、ers have selected 64-QAM with 3/4 FEC and a 1/16 guard interval. 1Refer http:/www.acma.gov.au/WEB/STANDARD/pc=PC_90249. 2Refer http:/www.acma.gov.au/WEB/STANDARD/pc=PC_91853. Rep. ITU-R RA.2195 5 Protection ratios for digital-digital and digital-analogue co-channel and adjacent channel interference
31、from other television broadcasting services were first defined in July 1999. Only minor changes have been made to those original values. The values used in Australian planning are the same as the 64-QAM, 2/3 FEC values set out in Recommendation ITU-R BT.1368-73. Australias planning for digital telev
32、ision services takes into account a legislated requirement that “. in SDTV digital mode in that area should achieve the same level of coverage and potential reception quality as is achieved by the transmission of that service in analogue mode in the same area”. Following this approach, Australias di
33、gital services are typically planned with a maximum e.r.p. of 6 dB less than same band analogue television services. The operating radiated power levels of digital services across the VHF and UHF bands are chosen on the basis of addressing the coverage requirements of each transmitter. Radiated powe
34、r levels of particular digital services in band III range up to 50 kW e.r.p. in metropolitan areas and up to 100 kW e.r.p. in some regional areas. Services in band IV have been planned with e.r.p. levels that range up to 500 kW e.r.p. and services in band V range up to 1.25 MW e.r.p. in regional are
35、as. Australian digital television planning is based on provision of a minimum median field strength level. The Australian planning values are reasonably close to the values that can be derived from the sample calculation value provided in Table 44 of Recommendation ITU-R BT.1368-74. The Australian v
36、alues are higher than values that would be derived from the Recommendation. The difference is due to: inclusion of a 1 dB higher receiver noise figure allowance; use of 6.7 MHz rather than 7.6 MHz for the receiver bandwidth; and use of frequencies at the top rather than the middle of each band as th
37、e reference frequency for the calculation. The Australian minimum field-strength calculations also include a 1 dB “Interference margin” for the support of co-channel, frequency reuse planning. Planning guidelines in Australia also specify minimum median field strengths (referred to a measurement hei
38、ght of 10 m above local terrain) for digital television services as shown in Table 15,6. TABLE 1 Minimum median field strength for DTTB Planning in Australia Environment Band III (dB(V/m) Band IV (dB(V/m) Band V (dB(V/m) Urban 66 71 74Suburban 57 63 67 Rural 44 50 543The original 1999 values were ad
39、opted following protection ratio measurements made in 1998 using the “traditional” wanted-to-wanted protection ratio measurement approach, rather than the more recent C/(I+N) approach that appeared in Recommendation ITU-R BT.1368-1 (and later revisions). 4Australian planning is based on provision of
40、 a service at 80% of locations within 200 m by 200 m areas. A 4.5 dB correction factor is applied to convert from a 50% of locations to an 80% locations field strength value. 5Refer http:/www.acma.gov.au/WEB/STANDARD/pc=PC_91853. 6Field strength values used here apply to 7 MHz channel bandwidths. 6
41、Rep. ITU-R RA.2195 To minimize the “cliff-effect”, digital television services are planned to achieve the required protection ratio for better than 99% of the time, irrespective of whether the interference is considered to be continuous or tropospheric in nature. The relevant protection ratios are n
42、ot to be exceeded for more than 1% of the time. That is, the E(50,1) value is used for the interfering field strength. Spectrum masks for cases where a transmitter for digital terrestrial television is co-located with, and operating on a channel adjacent to: a) a transmitter for analogue television
43、are given in Fig. 3 and Table 2 for analogue television system B/PAL/A2; b) a transmitter for digital television are given in Fig. 4 and Table 3 for COFDM digital television with a modulation mode of 64-QAM with an FEC of 2/3. The masks shown in Figs 3 and 4 cover the minimum protection needed for a
44、nalogue and digital television where the analogue and the digital television transmitters are co-located and are applicable for cases where: no polarization discrimination between digital and analogue television is used. The masks are to be used for the comparison of e.r.psof the wanted and unwanted
45、 services. Such comparison may be provided from calculation from the actual transmitter spectrum output and antenna system gains. The masks provide the limit to the power and the out-of-band products of the unwanted digital service. The mask levels are fixed in relationship to the wanted service, he
46、nce the actual mask of the interfering service must be derived from the actual operating power of the interfering service and its relationship to the wanted analogue or digital service. FIGURE 3 Spectrum mask for a digital terrestrial television transmitter operating with a co-located lower or upper
47、 adjacent channel analogue television transmitter 100Frequency relative to centre DTTB channel (MHz)0Spectraldensity(dB/4kHz)301012 11 10 9 8 7 6 5 4 3 2 1 0 1 2 3 4 5 6 7 8 9 10 11 12206040907080DTTB Spectrum mask (analogue upper and lower adjacent)DTTB “CW“ carrier powerPAL “peak sync“ vision carr
48、ier power DTTB spectral densityeg 10 dB ref. PAL Lower analogue channel Upper analogue channel50Rep. ITU-R RA.2195 7 TABLE 2 Breakpoints for spectrum mask for a digital terrestrial television transmitter operating with a co-located lower or upper adjacent channel analogue television transmitter Lowe
49、r breakpoints Relative frequency (MHz) 0 3.3 3.4 3.5 3.51 3.75 4.75 8.25 9.25 10.5 Relative level (dB/4 kHz) 29 29 50 56 56 56 74.5 77 77 100 Upper breakpoints Relative frequency (MHz) 0 3.5 3.7 3.8 4.2 4.75 10 10.5 Relative level (dB/4 kHz) 29 29 29 40 77 77 77 100 FIGURE 4 Spectrum mask for a digital terrestrial television transmitter operating with a co-located lower or upper adjacent channel digital terrestrial television transmitter 100Frequency relative to centre DTTB channel (MHz)0Spectraldensity
