1、STD-ITU-R RECMN 60-2007-1-ENGL 1998 m 4855212 053b41i9 09b M 22 Rep. ITU-R B0.2007-1 REPORT ITU-R B0.2007-1 CONSIDERATIONS FOR THE INTRODUCTION OF BROADCASTING SATELLITE SERVICE HIGH DEFINITION TELEVISION SYSTEMS* (1995-1998) 1 Introduction The World Administrative Radio Conference for Dealing with
2、Frequency Allocations in Certain Parts of the Spectrum (Malaga-Torremolinos, 1992) (WARC-92) made an allocation in the bands 21.4-22.0 GHz in Regions 1 and 3 and 17.3-17.8 GHz in Region 2 to the broadcasting-satellite service (BSS) on a primary basis from 1 April 2007. It has adopted, by Resolution
3、525 (WARC-92), a set of interim procedures to allow BSS high-definition television (HDTV) to be introduced in Regions 1 and 3 from 1 April 1992. Resolution 525 (WARC-92) also stipulates that the located frequency band shall be used for HDTV in the BSS. It stipulates further that, before a future con
4、ference has taken decisions on definitive procedures, the use of the allocated band shall be based on Resolution 33 (Rev.WRC-97) and Article S27/34 of the Radio Regulations (RR), and that after 1 April 2007 the introduction of HDTV systems in this band must be regulated in a flexible and equitable m
5、anner until such time as a future competent world radio conference has adopted definitive provisions for this purpose in accordance with Resolution 507. The interim procedures utilize sections of Resolution 33 (Rev.WRC-97) which apply to the BSS in bands where plans are not in force but limits the r
6、equirements for coordination with the assignments of other countries to systems which exceed certain trigger values. This Report lists a number of characteristics to be considered in the development of BSS (HDTV) systems under these procedures. Although the interim procedures of Resolution 525 (WARC
7、-92) apply only to the introduction of BSS (HDTV) in the 21.4-22 GHz band in Regions 1 and 3, the material in 8 5,6 and 7, and in the Annexes to this Report may also be of interest for system planning in the 17.3-17.8 GHz band in Region 2. Likewise, this material may be of interest in connection wit
8、h the possible accommodation in the 12 GHz band of BSS (HDTV) systems, particularly for the tropical countries of Regions 1 and 3 as envisioned in Resolution 524 (WARC-92). 2 Regulatory provisions Resolution 525 (WARC-92) established an interim set of regulatory provisions to give flexible and equit
9、able access to the geostationary orbit and the designated spectrum before a competent radiocommunication conference takes definitive decisions on a replacement procedure. The Resolution makes a distinction between “operational” and “experimental” systems and to systems introduced before and after 1
10、April 2007. Table 1 indicates the applicable procedures. 3 Status of existing services The band 2 1.4-22.0 GHz is also allocated to the fixed and mobile services on a primary basis. Paragraph 1 of the Annex to Resolution 525 (WARC-92) indicates that: “It shall be understood that prior to 1 April 200
11、7 all existing services in the band 21.4-22.0 GHz in Regions 1 and 3 operating in accordance with the Table of Frequency Allocation shall be entitled to continue to operate. After that date they may continue to operate, but they shall neither cause harmful interference to BSS (HDTV) systems nor be e
12、ntitled to claim protection from such systems.” This requirement may result in fixed services needing to be relocated from the 2L4-22.0 GHz band to other nearby bands. Radiocommunication Joint Working Party (JUTp)lO-l1S has requested Study Group 9 to look into this topic. * This Report provides tech
13、nical information relevant to the application of the interim procedures contained in Resolution 525 (WARC-92). STD.ITU-R RECMN 60.2003-1-ENGL 1998 Rep. ITU-R B0.2007-1 = 4855212 053b420 808 m 23 TABLE 1 General scheme of applicable procedures to implement BSS (HDTV) systems* Date of use of HDTV band
14、 Before 1 April 2007 After I April 2007 Conditions Experimental systems I PFD a Operational systems PFD m o .- I - i -30 40 Service interruption -I- F 4 T I Non-layered HQ layer LQ layer O 10 20 30 40 50 60 Time (min) a) Case of a storm O - -10 8 M C -o .- e 2 -20 G W m b) .- .d - -30 -40 Service in
15、terruption I I l I Il LQ layer O 10 20 30 40 50 60 Time (min) b) Case of a typhoon Rap 2W?-08 STDmITU-R RECMN B0-2007-1-ENGL 1998 4855232 053b431 b93 34 Rep. ITU-R B0.2007-1 For the viewers of HDTV, for example, even a relatively short interruption of service can severely disturb an attractive and e
16、xciting scene. Therefore, although it is important to evaluate the service continuity due to the rain attenuation with cumulative time percentage, detailed rain fade profiles are much more important when considering service availability. Digital broadcasting should bring excellent performance, far b
17、etter than current FM television broadcasting. It should be noted that the effectiveness of layered modulation depends largely on the available link budget margin for the high-quality (HQ) service. Layered modulation can significantly improve the service availability, accepting a lower quality level
18、 of service during high precipitation periods, if the HQ link budget margin is relatively small (e.g. 3-4 dB), Le. for limited satellite transmit power and/or small home receive antennas. If the HQ link budget margin is rather large, say 10-15 dB, because high satellite e.i.r.p. and/or large home re
19、ceive antennas are used, the improvement in service continuity by the second (and, if applicable, the third layer) is relatively small, because rain attenuation increases exponentially for small cumulative percentages of time. 4 Summary The described methods are examples of how the service continuit
20、y could be increased by using a concept of layered modulation in conjunction with layered picture coding and layered channel coding. Other variants of this principal approach are presently under investigation. It can already be deduced, however, that by means of this technique the service continuity
21、 could be extended to, or even exceed, 99.9% of the worst-month in areas of moderate climate without the need for increasing the satellite transmit power, the service quality under severe attenuation conditions being reduced from high definition to normal or limited definition television. In countri
22、es characterized by high density (tropical) rainstorms, additional measures such as adaptive satellite e.i.r.p. control method (see Annex 2) might be required to reach such a high service continuity. Nominal high-quality sound service should be preserved even under severe fades and the sound should
23、only fail after the failure of picture. The concepts outlined in this Annex warrant further study. For example: Effects of detailed compensation by the layered modulation approach using the practical rainfall profile. Parameters for efficient service availability and the threshold CIN value for each
24、 layer. Effects of frequent strong rainfall in typhoons, etc. and of heavy continuous rain. Complexity of the demodulator and the decrease of efficiency of spectrum usage due to layered transmission. Development of stable demodulator in a low CIN environment, especially for synchronization. REFERENC
25、ES PALICOT, J. and VEILLARD, J. 1993bl Possible coding and modulation approaches to improve service availability for digital satellite broadcasting at 22 GHz. IEEE Trans. Consumer Electron, August. PALICOT, J. and VEILLARD, J. 1993a Possible channel coding and modulation system for the satellite bro
26、adcasting of a high-definition signal. Image Comm. J., Special Issue on “Advances in High-Definition Television”, September. TSUZUKU, A., FUKUCHI, H., OHKAWA, M., OHUCHI, and MORIKAWA, H. 19931 Advanced satellite broadcasting experiment using Japans R an example of a three-layer system; an introduct
27、ion to the interworking aspects considered in the Project, and more particularly the “common receiver concept” and the “interoperability with cable networks”. 2 Service characterization Service requirements and characterizations within the HD-SAT project have been determined with user requirement st
28、udies including a comprehensive survey which was sent to European satellite operators, terrestrial broadcasters and cable network operators. A summary of the basic HD-SAT service characterization is given below: - - - European coverage; - - service availability of 99.6% (of worst month); highest qua
29、lity possible within HDTV format (virtual studio quality); small (60-90 cm) DTH receiver antenna; full quality service to the end-user via cable and MMDS networks. 3 The use of the 20 GHz frequency band for satellite transmission must cope in an efficient way with the adverse propagation conditions
30、in these bands, which are characterized by deep rain fades and atmospheric depolarization. A key issue is the service continuity, for which new solutions are implemented which involve layered channel modulation to allow for a “graceful degradation” under deteriorating atmospheric conditions. Service
31、 continuity - graceful degradation in the Ka-band Contrary to the gradual degradation observed in analogue systems, for digital TV it is possible to go from virtually error-free reception to complete loss of picture decoder operation over a range of less than 1 dB of C/N degradation (the brick-wall
32、effect). By providing for the means of receiving lower quality pictures under deteriorating reception conditions, digital graceful degradation can allow for an increased service continuity. The goal for a successful satellite modulation scheme is, using minimum satellite power and a small home recei
33、ver antenna size, to achieve service continuity for 99.6% of the worst-month within Europe. The graceful degradation satellite modem for HD-SAT has been conceived using the concept of time-multiplex of modulation techniques offering a hierarchy of C/N values required for successful demodulation. In
34、this way, as the propagation conditions deteriorate, the modulation layers requiring the higher C/N values are “lost”, while the more robust layers continue to be received. Synchronization of the modem is simplified by keeping the same symbol rate (27 MBd/s) for each of the modulation layers. Figure
35、 13 illustrates the modulation “frame” for a three-layer implementation. FIGURE 13 Example of hierarchical channel coding Essential data, basic sound, low resolution video HQ SDTV, Hierarchical HD-components surround sound Spatial SIN (quality) QPSK at 54 Mbids - _ T1 T2 T3 t T 1 : T2: TCM: trellis
36、coded modulation turbo code i12 turbo code 314 or “convolutional code and Reed-Solomon Rap 2007-13 STD-ITU-R RECMN B0.2007-1-ENGL 1998 9 4855212 053b438 “48 = Rep. ITU-R B0.2007-1 41 When choosing, for example, the ratio Tl:T2:T3 = 1:3:6, the corresponding bit rates will be 2.7 Mbit/s for TI, 16.2 M
37、bitk for T2 and 48.6 Mbit/s for T3, giving the total gross bit rate of 67.5 Mbit/s. 8-PSK modulation combined with trellis convolution coding is selected as an appropriate scheme for the highest spectral efficiency (but least “robust”) of the HD-SAT modulation hierarchy. Lower level schemes include
38、QPSK with turbo code or a classical scheme of convolutional code with concatenated Reed-Solomon, for an intermediate level of service, and 2-PSK for the low-level service fallback mode. Turbo coding uses iterative processes in a hardware efficient implementation of code concatenation. It is particul
39、arly effective when applied to relatively low code rates. Results of turbo coding applied to QPSK within HD-SAT show a significant coding gain, a high degree of independence to roll-off combined with good transmission efficiency (by removing the need for an FEC outer code) within a non-linear satell
40、ite channel. Under these conditions the performance of the channel coding closely approaches the Shannon limit. A modulation scheme allowing for approximately 12 dB of attenuation between the nominal clear sky operating point for HDTV and complete loss of service is proposed as a viable solution. Of
41、 this 12 dB, 9 dB is provided by the graceful degradation operation itself, with the remaining 3 dB coming from the operating point margin of a “nominal” home receiver antenna. A graph of HD-SAT service versus received UN is given in Fig. 14 to illustrate the graceful degradation operation and perfo
42、rmance. FIGURE 14 Hierarchical channel coding CIN performance Service HDTV quality i SDTVEDTV quality “Fall back” quality Service interruption I III l I I I I I I 1 I l I), !,!I O 5 10 CIN (dB) in 36 MHz 3-level hierarchical system - conventional system EDTV: extended definition TV Rap 2007- 14 STD-
43、ITU-R RECMN B0-2007-L-ENGL 1998 4855212 0536439 984 42 Rep. ITU-R B0.2007-1 1st layer 2nd layer 4 Picture coding (MPEG-2) and attribution of the modulation layers The HD-SAT system uses MPEG-2 coding (high profile at high level) and multiplexing, which amongst other functionalities offers the two fo
44、llowing key features: Essential data, sound and limited definition image “Good” quality SDTV sound and image and additional data e.g. 1.5 Mbit/s e.g. 10 Mbit/s - spatial and SNR scalability; - downward compatibility. The codec definition and the function of the satellite graceful degradation modem a
45、re intimately related. The allocation of the appropriate components of the Codec to the modulation layer will define the HD-SAT services under graceful degradation. First sublayer: spatial hierarchical data complement to achieve HDTV quality Second sublayer: additional SNR scalable information compl
46、ement to reach virtual studio quality HDTV The three-layer system below is chosen primarily for its comprehensive range of service availabilities over both moderate and severely degraded propagation conditions, as well as for its potential for interworking with other systems and media. e.g. 15 Mbits
47、 e.g. 20 Mbits TABLE 5 Performances of layers 3rd layer 5 Interworking aspects 5.1 Common receiver concept Interworking between media and television formats could be made economically feasible by the concept of the common receiver (see Fig. 15) which allows an end-user to receive programmes and serv
48、ices over a variety of media using a common demultiplexer, source decoder and display. For each media to be exploited, this common receiver uses the appropriate channel adapteddecoder which provides the common MPEG-2 transport stream format to the input of the multiplexer, 5.2 Interoperability with
49、cable networks The channel characteristics of a coaxial television cable network are very different from those of a satellite transponder. In particular, there is no need nor place for graceful degradation within the cable channel. At the cable head-end, an adaptation of the HD-SAT MPEG-2 transport stream is required to optimize the use of the cable bandwidth. The base HD-SAT MPEG-2 transport stream necessarily contains some additional components for the service continuity fallback service which are not used in media implementation without graceful degradation. For th
