1、-1- Rep. ITUT-R B0.2006 REPORT ITU-R B0.2006 INTRODUCTION OF SATELLITE AND COMPLEMENTARY TERRESTRIAL DIGITAL SOUND BROADCASTING IN THE WARC-92 FREQUENCY ALLOCATIONS (Questions ITU-R 93-1/10 AND ITU-R 107/10) (1 995) NOTE 1 - This Report addresses the necessary planning elements associated with satel
2、lite and complementary terrestrial digital sound broadcasting and should be read in conjunction with the latest versions of Report ITU-R B0.955 and Report ITU-R BS. 1203. 1 Introduction Allocations in Certain Parts of the Spectrum (Malaga-Torremolinos, 1992) (WARC-92), the following frequency alloca
3、tions were made to the broadcasting-satellite service (sound) (BSS(S): Arising from the World Administrative Radio Conference for Dealing with Frequency Worldwide (Regions 1,2 and 3) except the United States America: the band 1 452-1 492 MHz is allocated for BSS(S) and complementary BS(S) on a prima
4、ry basis, although some countries (mainly in Europe and Africa) have chosen to maintain this allocation on a secondary basis until I April 2007. For the United States and India, the band 2 310-2 360 MHz is (in a footnote) located for BSS(S) and)d complementary BS(S) on a primary basis. For some coun
5、tries in Asia and the Russian Federation, the band 2 535-2 655 MHz (note that the bandwidth is 120 MHz), is by means of a footnote, allocated for BSS(S) and complementary BS(S) on a primary basis. Associated with the allocations in Article 8 of the Radio Regulations (RR), there are footnotes restric
6、ting the dates of introduction and the level of service in some countries. The worldwide allocation is therefore not available in all countries as the Regulations are now phrased. In particular, the United States has an alternative allocation and (in a footnote) the band 1 452-1 492 MHz is allocated
7、 to fixed and mobile services on a primary bases. In addition to the allocation in RR Article 8, there were several procedures for)r introduction of new sound services. Resolution No. 527 (WARC-92) recognized that it may be possible to introduce new digital services in the terrestrial VHF broadcasti
8、ng bands and opened the door to a more detailed consideration. Resolution No. 528 (WARC-92) -eves details of the introductory procedures. It discusses the need for a planing conference, restricts the range of frequencies that may be used before the planing conference to the upper 25 MHz of the appro
9、priate band, and details the method of calculating interference criteria (these are determined by means of Resolution No. 703 (Rev. WARC-92) procedures, and so there are as yet no formal technical procedures that can be applied). -2- Rep. ITUT-R B0.2006 Resolution No. 522 (WARC-92) gives details of
10、the types of orbit that can be used and the future work that is necessary before non-GSO systems can be deployed. Figure I shows the differences in allocations throughout the world. 2 Service requirements 2.1 Service goals There are a number of possible goals in introducing digital sound broadcastin
11、g services: to replace current AMEM broadcasting, in order to provide better quality and more reliable services and to better compete with other distribution media that can bring “CD” quality audio services to the listener; to provide the listener with a new service that can compete with the current
12、 AMEM broadcasting service; to provide a service with conventional quality grade to large service areas for reception by very low cost receivers. There is a recognized need for new sound broadcasting services to provide a better service to vehicular receivers (see Recommendation ITU-R B0.789). Furth
13、ermore, some services may also be directed to portable receivers for use inside buildings. Currently, several administrations and commercial organizations have proposed sound- broadcasting satellite systems having different audio quality levels (CD, “Near-CD”, FM stereophonic, FM monophonic and AM).
14、 Service to different kinds of receiver installations has been proposed (vehicular, portable and fixed), as well to a variety of environments (indoor, outdoor, rural, urban and suburban). All of these system approaches are technically feasible. One or more of them may be cost-effective and attractiv
15、e to administrations depending on their state of development, the extent of their existing terrestrial systems and their broadcasting requirements. -3- Rep. ITUT-R B0.2006 N I c3 9 N U m N I W Vl F I N IT U Ln 7 N I W 9 N U m N X U N N I 0 ln c N I W n N -4- Rep. ITUT-R B0.2006 There is a need to pr
16、ovide digital sound broadcasting services having a wide range of subjective audio quality. There may be substantial demand, particularly in developing countries and in sparsely settled countries having little terrestrial broadcasting infrastructure, for the digital equivalent of standard monophonic
17、FM, and oven for the digital equivalent of double-sideband AM. 2.2 Service objectives The objective of new sound broadcasting services is to improve the availability, quality and diversity of programme services to listeners. Wide area coverage-e will bring programme service to many listeners for the
18、 first tone and advanced digital techniques will allow high-quality sound equivalent to the quality available from other sound media (e.g., compact discs). Advanced digital techniques will also make possible a wide range of new programme-related and independent services with minimal impact on spectr
19、um and power requirements. The BSS (sound) and BS (sound) is aimed at fixed, vehicular and portable reception. The technical system objectives are determined by two factors: quality and availability. 2.2.1 Quality determining the type of system to be used and the overall system design and cost. Care
20、ful consideration needs to be given to the interaction between performance and economic factors. Digital sound broadcasting has been under consideration now for over 25 years, and during that time the reproduction and transmission of sound has undergone considerable development. The service objectiv
21、es for digital sound broadcasting may play an important role in The expectations of the listeners have also increased considerably. Most people in urban areas now expect high-quality stereo sound, even from portable or vehicular radios. The enormous advances in the performance of domestic “hi-fi“ eq
22、uipment, culminating in the extensive use of compact discs, has conditioned many people to expect sound quality greater than that which even fixed FM receivers cap give. Even in remote areas, similar expectations often exist owing to the wide availability of good quality cassette recorders and compa
23、ct disc players. Much of the wide-area coverage is currently achieved by long-, medium- and short-wave ionospheric transmissions. Even though the population of those areas may prefer to receive entertainment broadcasts of the highest technical quality, it may be more economical for this type of serv
24、ice to accept monophonic service of medium quality provided it was reliable, and could be received on portablehehicular receivers. For these reasons, quality objectives can range from grade 3 on the 5-point ITU-R scale for a simple monophonic system to grade 4.5 for an advanced digital system. For t
25、he advanced digital systems, the objective is to provide a high-quality stereophonic service, comparable to compact disc quality. These distinct grades of service quality may lead to different system trade-offs. 2.2.2 Availability Traditional methods of planing for terrestrial broadcasting have used
26、 an availability criterion which requires 50% of the locations within the coverage area to meet the quality objectives for at least 50% of the time. It can be expected that the service availability objective for all services will be increased; and, particularly for the high-quality grade service, it
27、 will need to be substantially increased from the criterion stated above. Some possible techniques for increasing, service availability under certain conditions include time diversity, frequency diversity, and space diversity at the receiver, in addition to the use -5 - Rep. ITUT-R B0.2006 of on-cha
28、nnel terrestrial repeaters allowed by some modulations, to fill in shadowed areas which translates into space diversity at the transmission end. 2.3 Service concepts 2.3.1 BSS (sound) concept Service areas are covered by satellite beams. The extent of the beam coverage needed on the Earth determines
29、 the size of The satellite transmit antenna. The transmission power at the satellite has to be large enough to compensate for propagation losses ,and to provide adequate fixed, portable and vehicular reception of the Earth. This concept can be used for covering sub-national, national, supra-national
30、, and even global service areas. The concept of satellite sound broadcasting is well described in Report ITU-R B0.955. 2.3.1.1 Hybrid BSS (sound) concept fillers”) using the same carrier frequency to cover shadowed areas produced by large buildings, tunnels, valleys, etc. This hybrid BSS concept is
31、a special application of the new advanced digital modulation schemes which can make constructive use of echoes and therefore are well suited to operate in a multipath environment. In such cases, active echoes deliberately introduced by co- frequency repeaters to fill the shadowed areas appear to the
32、 receiver as if they were passive echoes. This results ill a reduction of the needed satellite power to the level typically needed to cover rural areas. The retransmitted power can be very low, of the order of a few watts, depending on the size of the shadowed area to be covered. The satellite cover
33、age can be improved through the use of low-power repeaters (“gap- 2.3.2 BS (sound) concept 1203. In the case of conventional AM and FM broadcasting, service areas are covered by one or more transmitters operating on different frequencies. The transmission power and the effective height of the antenn
34、a above average terrain (EHAAT) for terrestrial digital sound broadcasting stations need to be large enough to compensate for propagation losses and to provide adequate fixed, portable and vehicular reception. This concept can be used for covering local service areas with a single transmitter, or su
35、b-national and national service areas using the single frequency network (SFN) concept described later. The concept of terrestrial digital sound broadcasting is well described in Report ITU-R BS. 2.3.2.1 Distributed emission concept for digital terrestrial sound broadcasting receiving the signal fro
36、m the main transmitter and rebroadcasting it on the same frequency in the vicinity of the repeater. On-channel “gap-fillers” within the service area can be seen as a special localized case of the distributed emission concept. This requires that, as in The case of the hybrid concept, the type of modu
37、lation used allows operation in a multipath environment and makes constructive use of passive as well as active echoes. Normal terrestrial broadcasting can also be augmented with the use of Co-channel repeaters The use of repeaters either as gap-fillers or coverage extenders to improve the terrestri
38、al coverage allows a decrease of the required terrestrial transmitter power and, in addition, create a sharper discrimination towards a service area using The same frequency for satellite reception. The same sharper discrimination could be used to reduce the separation distance between two coverage
39、areas using the same frequency, thus allowing greater frequency of reuse. -6- Rep. ITUT-R B0.2006 There exists an upper limit on Co-channel repeater separation (several kilometers), and this limit is set by intersymbol interference occurring when two signals reach a receiver with a time difference w
40、hich exceeds the guard interval between data symbols. Other concepts using spread spectrum signal structures, which could allow repeaters to transmit on a common channel and place fewer constraints on repeater separation, are under study. An alternative concept utilizing frequency translating repeat
41、ers, each transmitting at a different frequency to fill shadowed areas for extended coverage, would not be constrained by the distance between repeater transmitters, but would require more channels. 2.3.2.2 signal and broadcast on the same frequency. As in the previous case, there is a limit on the
42、separation distance between these transmitters ,and this I limits it is set by the intersymbol interference produced at the receiver by the active echoes generated by these multiple transmitters. Single frequency network concept (SFN) In this concept, ideally, regularly spaced transmitters are fed s
43、ynchronously by the same This concept can be used to extend the reach of terrestrial broadcasting to national and even supra-national service areas. 2.3.3 of the same frequency band by both satellite and terrestrial broadcasting services. It can maximize the spectrum use by allowing these two broadc
44、asting services to closely coordinate their service development rather than attempting sharing of the frequency band by totally unrelated services. The assumption is that with a near omnidirectional receiver antenna, the same receiver would capture the emissions of both satellite and terrestrial ser
45、vices. Using modem technology, the same modulation techniques need not be used for terrestrial and satellite transmissions into the same receiver. However, a common modulation technique would reduce receiver complexity and costs. Mixed satelliteherrestrial sound broadcasting service concept The conc
46、ept of a “mixed” satellite/terrestrial sound broadcasting service is based on the use All channels not allocated to the BSS for a service area which could be used for terrestrial broadcasting in this service are subject to the usual Co-channel reuse factor and adjacent channel rejection in the recei
47、vers. Certain precautions will need to be exercised in implementing such mixed satellite/terrestrial broadcasting service where the edge of coverage of a terrestrial system is situated near the edge of a satellite coverage area assigned to the same channel. Such reuse, for terrestrial broadcasting,
48、of the channels of adjacent satellite beams of other countries, or within the same country, maximizes the spectrum usage and provides a flexible way by which a service could evolve from strictly local terrestrial broadcasting to mixed satellite/terrestrial services when wide area national services b
49、y satellite are added. This reuse could also evolve from national (or even supra-national) services carrying national interest programming by and/or specialized services over satellite later complemented by local terrestrial services when this is more economical. This could also be attractive for the future implementation of specialized commercial services over satellite for national coverage when the receivers have reached a high level of penetration. A study was made on the practical implication Of such additional interference from the nearby satellite beam (CCIR, 1990-1994, Doc. IOB/
