Appendix I Radio Regulations Provisions E. D'Andria I. Introduction We summarize the Radio Regulations provisions and pertinent CCIR recommen­ dations and reports which give a more complete description of frequency sharing. To permit development of the fixed-satellite service (FSS), one of the last services introduced into the Radio Regulations, several technical and administra­ tive rules have been established to guarantee the compatibility of this new service with existing ones having the same frequency allocations. The very first rules were evolved by the Extraordinary Administrative Radio Conference for space radio communications, held in Geneva in 1963, and included in the Radio Regulations. The growing demand for space radio-communication services led the World Administrative Radio Conference for Space Telecommunications, WARC­ ST 1971, to revise and broaden previous frequency allocations and to produce improved technical criteria for frequency-sharing and coordination procedures. The WARC-1979 revision produced the provisions now in force; WARC- 1979 also resolved to hold a conference on the use of the GEO and planning of the space services utilizing it. The first session, held in 1985 (WARC-ORB '85), identified the frequency bands allocated to space services, plus principles and methods for planning to guarantee to all countries equal access to the GEO. The second session, held in 1988 (WARC-ORB '88), defined an allotment plan which specifies for each country the satellite nominal orbital position within a predetermined arc, the satellite beam characteristics, including geographical coordinates of the bore sight , and the satellite and earth stations EIRP densities. Each allotment is to have an aggregate C / I of at least 26 dB, although, when considering existing systems, in some cases this value is not reached. E. D'ANDRIA • Telespazio S.p.A., Via Tiburtina 965, 00156 Roma, Italy. Satellite Communication Systems Design, edited by S. Tirro. Plenum Press, New York, 1993. 775 776 E. D'Andria To take into account the growing interest for mobile services, a 1987 conference (W ARC-MOB '87) partially modified the frequency allocation tables in the Radio Regulations to permit the use of the 1.5-1.6 GHz frequency band for the implementation of land-mobile satellite services. The tendency to allow wider use of the spectrum by terrestrial and satellite mobile service in bands below 3 GHz has been confirmed in the recent W ARC '92. The peculiarity of the broadcasting-satellite service (BSS) and the demand for an assignment plan led to W ARC-'77, which defined, for each country into regions 1 (Europe, Africa, northern Asia) or 3 (southern Asia, Australia), a downlink plan specifying satellite orbital position, coverage, polarization, carrier frequencies, EIRP, and other system characteristics for individual and community receptions. The lack of frequency bands for the feeder links, identified by WARC-'79, suggested holding the uplink planning conference during WARC­ ORB'88. In this conference the uplink assignment plan was defined in the 17.3-18.1 GHz band under the general principle of linear transposition between up- and downlink frequency assignments. Moreover, for countries which so requested, some additional frequency assignments have been planned in the 14.5-14.8 GHz band. For countries in region 2 (the Americas) the Regional Administrative Radio Conference for planning the BSS (RARC-'83) defined the uplink and downlink assignment plans. In this appendix only the FSS is considered. The BSS is discussed in Chapter 9, Section VII H. II. Frequency Allocations The allocation of exclusive frequency bands for the FSS has not been generally practicable because the FSS bandwidth has to be wide enough to accommodate many telephone and television channels, and because of propaga­ tion effects and technological developments, which suggested choosing FSS frequency bands from those allocated to the fixed service. The problem of sharing between these two services is simplified by the fact that ES antennas use interfering and interfered-with paths such that it is possible to minimize the interference effects. Figure 1 shows the frequency bands allocated to the FSS up to 30 GHz in the three lTV regions. The division of the world into radio regions is shown in Fig. 2. In general, frequency allocations to the FSS are shared with the fixed service. Only a limited part of the radio spectrum beyond 30 GHz is assigned to the FSS exclusively in all regions of the world. Below 30 GHz exclusive allocations are only on a regional basis (see Fig. 1). An example of exclusive allocation in region 1 is the 12.5-12.75 GHz band for the downlink. Paired with the uplink 14-14.25 GHz band (which is not shared with the fixed service), this band permits implementation of installations at users' premises without any coordination problem. Other exclusive allocations, not included in the Radio Regulations, are also planned in some countries in region 2 on a national basis. Appendix I • Radio Regulations Provisions m FREOUENCY (GHz) 10 15 20 25 30 REG 1 REG 1 J~---- ---. REG 2 ~~ REG 3 " 10 15 20 25 30 FREOUENCY (GHz) pj USE LIMITED TO NATiONAL AND ~ REGIONAL SYSTEMS Fig. 1. Frequency bands allocated to the fixed-satellite service. (Reprinted with permission from the CCIR Handbook.) III. Interference Coordination As shown in Fig. 1 most of the frequency bands for the FSS were also allocated to other services, particularly to the fixed service. In view of this, not only interference between different systems of the FSS should be considered but also THE SHADED PART REPRESENTS THE TROPICAL ZONE Fig. 2. The ITU division of the world in radio regions. (Reprinted with permission from the ITU Radio Regulations.) Appendix I • Radio Regulations Provisions respect can avoid any interference problem, and no interference calculations are required in these cases. B. Modes of Interference between Stations of Different Space Systems in Frequency Bands with Separated Earth-to-Space and Space-to-Earth Allocations Bl Space station transmissions of one space system possibly causing inter­ ference to reception by an ES of another space system B2 ES transmissions of one space system possibly causing interference to reception by a space station of another space system The calculation to determine if coordination is required must be based on the increase in equivalent satellite link noise temperature caused by another satellite link and is treated by Appendix 29 to the Radio Regulations. 2 If the percentage increase exceeds a threshold value of 6% the Administration responsible for the new space system shall require coordination with the administrations owning the space systems which are affected, and detailed interference calculations shall be performed. Modes Bl and B2 generally occur simultaneously in those space systems which adopt the same band pairings (e.g., 4-6GHz, 11-14GHz, 20-30 GHz), if free-space propagation conditions apply. C. Modes of Interference between ESs of Different Space Systems in Frequency Bands for Bidirectional Use In this case modes Bl and B2 are extended as follows: E Space station transmissions of one space system possibly causing inter­ ference to reception by a space station of another space system F ES transmissions of one space system possibly causing interference to reception by an ES of another space system The bidirectional use of the frequency bands allocated to the FSS is generally restricted to the feeder links of the BSS in a limited portion of the radio spectrum. Nevertheless, studies have been carried out to ascertain how much the bidirectional use by the FSS could improve the efficiency of utilization of the GEO. The evaluation of interference for mode E is based on the concept of the increase in equivalent satellite link noise temperature as treated by Appendix 29 to the Radio Regulations. 2 Although no specific provisions have been adopted for mode F in the Radio Regulations, CCIR Report 9993 provides a method for determining the bidirec­ tional coordination area. IV. Radiation Limitations As indicated in Section II it is sometimes possible, imposing radiation limitations, to avoid the cumbersome calculations generally needed to ascertain if 780 E. D'Andria Table I. Maximum AUowable PFD Produced by a Space Station on the Earth's Surface Maximum PFD versus arrival angle dB(W/m2) Frequency range (GHz) 00<0:s5° 5° < 0 :S 2SO 25° < 0 :S 90° Reference bandwidth 1.525-2.5 -154 -154 + 0.5(0 - 5) -144 2.5-2.69 -152 -152 + 0.75(0 - 5) -137 3.4-7.75 -152 - 152 + O. 5( 0 - 5) -142 In any 4-kHz band 8.025-1l.7 -150 -150 + 0.5(0 - 5) -140 12.2-12.75 -148 -148 + 0.5(0 - 5) -138 17.7-19.7 -115 -115 + 0.5(0 - 5) -105 In any I-MHz band 31-40.5 -115 -1l5 + 0.5(0 - 5) -105 coordination is required between space and terrestrial systems (modes Cl and C2). However, this approach must be used with care, since imposition of power limits prevents development of both services, whereas other nonpenalizing approaches, such as consideration of the pertinent paths geometry, can alleviate the possibility of harmful interference. The potential interference to terrestrial stations (mode Cl) is restricted by limitation of the maximum power flux density (PFD) produced by a space station on the earth's surface. An important aspect of this limit is that it varies with the incidence angle of the e.m. wave arriving on the earth. More precisely, the maximum allowable PFD increases with the incidence angle, since at higher angles of arrival the discrimination of the terrestrial station antenna is supposed to be maximum. The PFD limits are given in Section IV of Article 28 of the Radio Regulations. 4 The PFD at the earth's surface produced by emissions from a space station, including emissions from a reflecting satellite, for all conditions and for all methods of modulation, shall not exceed the values summarized in Table I in the reference bandwidth and for arrival angle e degrees above the horizontal plane.