1、 Rec. ITU-R SF.1602 1 RECOMMENDATION ITU-R SF.1602 Methodology for determining power flux-density statistics for use in sharing studies between fixed wireless systems and multiple fixed-satellite service satellites (Questions ITU-R 217/9-250/4 and ITU-R 206/9-237/4) (2002) The ITU Radiocommunication
2、 Assembly, considering a) that it is necessary to ensure that emissions from satellites do not exceed permissible interference to fixed wireless systems (FWS) in the bands shared between FS and FSS; b) that FWS can be adequately protected from the aggregate emissions from multiple satellites (non-GS
3、O constellations or fully populated GSO arc) by placing suitable limits on the power flux-density (pfd) in a reference bandwidth produced by individual satellites at the surface of the Earth; c) that any limitations of the pfd produced at the surface of the Earth should not place undue restrictions
4、on the design of GSO and non-GSO FSS; d) that Recommendations ITU-R SF.1482 and ITU-R SF.1483 provide maximum allowable values of pfd at the surface of the Earth produced by non-GSO satellites in the FSS to protect the FS in, respectively, the 10.7-12.75 GHz and the 17.7-19.3 GHz bands; e) that the
5、pfd levels specified in the Recommendations mentioned in considering d) were developed from a pfd mask analysis used to calculate the statistics of aggregate power levels received at an FS station by applying pfd levels under consideration to each visible satellite of the non-GSO FSS constellation;
6、f) that, when considering a multi-satellite environment, such as non-GSO constellation or fully populated GSO arc, all the visible satellites may not simultaneously radiate the maximum pfd limit in the direction of the FS system under consideration, recommends 1 that the methodology described in Ann
7、ex 1 may be used for determining pfd statistics for use in sharing studies between FWS and multiple FSS satellites, taking into account satellite systems characteristics. 2 Rec. ITU-R SF.1602 Annex 1 1 Introduction This Annex presents statistical methodology concerning the impact of non-GSO and GSO
8、satellites on FWS. It takes into account realistic satellite characteristics and is intended for use as guidance in sharing analysis between FS and satellite services. It should also be noted that Recommendations ITU-R SF.1482 and ITU-R SF.1483 dealing with maximum allowable values of pfd at the sur
9、face of the Earth produced by non-GSO satellites in the FSS to protect the FS provides general background to this methodology. 2 Description of the pfd mask analysis The existing methodology for evaluating the pfd mask used either for GSO or non-GSO satellite systems, such as in the above-mentioned
10、Recommendations ITU-R SF.1482 and ITU-R SF.1483, aggregates the interference from all visible satellites to the FS using a regulatory pfd mask such as defined in Article 21 of the Radio Regulations. In a typical application of this methodology for the case of GSO satellites, the geostationary arc is
11、 filled with a given number of satellites (e.g. 1 every 4) which produces permanent interference. Representative results produced by the application of this methodology are shown on Fig. 1 for all the FS azimuths. 1602-010 50 100 150 200 250 300 35025 75 125 175 225 275 3252116116149141924FIGURE 1In
12、terference produced by a GSO satelliteFS azimuth (degrees)20 elevation10 elevationI/N(dB)Rec. ITU-R SF.1602 3 For the case of non-GSO systems, and on the basis of the characteristics of each single constellation (number of satellites, number of planes, inclination(s), altitude, .), the statistics of
13、 the theoretical aggregate power levels received at an FS station are calculated by applying pfd limits under consideration to each visible satellite of the non-GSO FSS constellation (see Recommendation ITU-R F.1108). In a typical application of this methodology, the interference distribution is cal
14、culated for the FS azimuth (and for a single elevation angle) that represents the constellation worst-case, which results in distribution of interference level versus percentage of time such as given in Fig. 2. 1602-0255 50 45 40 35 30 25 20 15 10 5 501510 20100101101102FIGURE 2Interference distribu
15、tion produced by a non-GSO systemI/N (dB)Per centofoccurence20 elevation10 elevationThis methodology has typically been used as a basis in inter-service sharing studies. This has the advantage of being a simple calculation but also represents an overestimation of the real interference that could be
16、suffered by FS stations. With regard to the FSS characteristics, the analysis assumes that all the visible satellites radiate simultaneously at the maximum pfd limits, in the direction of the FS system under consideration. Such an assumption does not take into account the patterns of the real satell
17、ite antenna, the power limitations of each satellite or the restrictions that self-interference (as a result of frequency reuse) would impose on an FSS system as well as the fundamental operational constraints of FSS systems. The methodology described in 3 provides a statistical approach toward acco
18、mmodating the FSS operational characteristics. 3 pfd analysis and satellite models This methodology takes into account realistic satellite antenna patterns, the power limitations of each satellite and the restrictions that self-interference would impose on a non-GSO FSS system, as well as the fundam
19、ental operational constraints of non-GSO FSS systems. This methodology assumes that, in a multi-satellite environment, all the satellites visible from a given point on the Earth do not simultaneously produce the maximum pfd allowed by a mask. 4 Rec. ITU-R SF.1602 The parameters necessary to accurate
20、ly model the pfd produced by a given satellite (maximum power, number of beams, antenna gain and antenna pattern) can generally be found in ITU-R documentation. The following is an analytical model of some of the possible parameters of a GSO FSS and a non-GSO FSS system. The values of such parameter
21、s depend on the considered frequency band and the type of satellite (GSO or non-GSO). It is possible to derive a general equation linking them together. In the main beam, for single beam coverage satellites, which could be implemented in certain frequency bands, the radiated power of the satellite n
22、ecessary to produce the maximum pfd in the main beam is: )4log(102dGpfdPsms+= (1) where: Ps: power density of the satellite (dB(W/MHz) pfdm: the maximum value of the pfd mask Gs: antenna gain of the satellite (dBi) d : range from the satellite to its sub-satellite point (m). However, in high frequen
23、cy bands such as the 20/30 GHz or 40/50 GHz bands, most satellites will more likely deploy multiple beams with higher antenna gain, transmitting on several channels. In this case, the power density of each individual beam can be calculated as: =tottottottotffdsBWNPNBWNNPBWPP log10log10log10 (2) wher
24、e: Pds: satellite power density per beam (dB(W/MHz) Pf: power per beam (W) BWf: beam bandwidth (MHz) Ptot: total radiated power available on the satellite (W) BWtot: total bandwidth of the satellite (MHz) N: number of frequency channels in BWtotN : number of co-frequency beams. On this basis, equati
25、ons (1) and (2) allow to derive the following general equation: )4log(10log102dBWNPpfdGtottotmb+= which gives: )4log(10)log(10)log(10)log(102dBWNPpfdGtottotmb+= (3) Rec. ITU-R SF.1602 5 where: Gb: beam antenna gain (dBi) pfdm: the maximum value of the pfd mask (dB(W/(m2 MHz) Ptot: total radiated pow
26、er available on the satellite (W) N : number of co-frequency beams BWtot: total bandwidth of the satellite (MHz) d : distance from the satellite to the centre of its pointing zone (m). Therefore, based on this equation (3) and using existing typical values that can generally be found in ITU-R texts,
27、 it is possible to define simple satellite models which could be used in sharing studies between FSS and terrestrial services. As an example, and in order to facilitate the understanding of and support the statistical methodology presented in this Annex, example satellite models below, assumed to be
28、 consistent with equation (3) (with a 105 dB(W/(m2 MHz) high elevation angle pfd level), have been considered: GSO satellites: Model GEO1: beam antenna gain: 60 dBi number of co-frequency beams: 6 total transmit power (for all beams): 3.5 kW total bandwidth: about 1 000 MHz Model GEO2: beam antenna
29、gain: 55 dBi number of co-frequency beams: 4 total transmit power (for all beams): 3.5 kW total bandwidth: about 500 MHz Non-GSO satellites (10 000 km altitude assumed): Model MEO1: beam antenna gain: 50 dBi number of co-frequency beams: 4 total transmit power (for all beams): 1.1 kW total bandwidth
30、: about 700 MHz Model MEO2: beam antenna gain: 45 dBi number of co-frequency beams: 3 total transmit power (for all beams): 1.1 kW total bandwidth: about 300 MHz 6 Rec. ITU-R SF.1602 4 pfd distribution 4.1 Principles As already stated above, the pfd produced by a given satellite, at any point on the
31、 surface of the Earth, depends on its transmitted power, antenna gain and antenna pattern. Furthermore, as shown in Fig. 3, the maximum pfd available in the main beam is mainly controlled by the regulatory pfd limit and the antenna pattern. In many cases, depending on the pointing elevation of the s
32、atellite, the pfd in the main beam is lower than the one given by the pfd mask in order to stay within the mask for lower elevation (such as for Elevations a and c in Fig. 3). 1602-03FIGURE 3Elevation aElevation cElevation bMain beamdirection0 elevationFurthermore, as described in Figs. 4 and 5, a s
33、atellite seen from a given point A on the Earth with an Elevation x, does not generally produce a constant pfd at A. The received pfd level at A varies based on the satellite downlink beam pointing direction and may also vary based upon traffic load. However, this latter characteristic is not taken
34、into account in this methodology. 1602-04AFIGURE 4Sub-satellite pointMain beam directionElevation xRec. ITU-R SF.1602 7 1602-05AFIGURE 5Sub-satellite pointMain beam directionElevation xIn Fig. 4, it can be seen that the pointing direction of the satellite beam is close to point A and that the antenn
35、a discrimination angle, , is relatively small. On the other hand, in Fig. 5, the pointing direction of the satellite beam is different and the antenna discrimination angle, , is bigger than . Furthermore, and as explained above, the pfd in the main beam for these two examples can be different. There
36、fore, the pfd produced at point A can be different even though the satellite is at exactly the same position. The pfd radiated in A can be easily calculated as follows: AdiscrimaxmbmbALGGLpfdpfd += (4) where: pfdA: pfd radiated in A (dB(W/MHz) pfdmb: pfd radiated in the main beam (dB(W/MHz) Lmb: fre
37、e space losses between the satellite and the centre of its beam at the Earths surface (dB) Gmax: maximum satellite antenna gain (dBi) Gdiscri: relative antenna gain in the direction of point A (dBi) LA:free space losses between the satellite and A (dB). On this basis, and by varying the pointing dir
38、ection of the satellite in all possible directions from its position, it is possible to determine the distribution of the pfd values that a satellite can produce for a given elevation as described in Fig. 6. 8 Rec. ITU-R SF.1602 1602-06010100101001 000159 154 149 144 139 134 129 124 119 114 109 104F
39、IGURE 6pfd distributions at 30 elevation for GEO1 model (60 dBi multibeam)pfd levels (dB(W/(m2 MHz)Per centofoccurenceIn addition, considering all the elevation angles for a given case (see calculation in Appendix 1), it is possible to draw the worst-case pfd mask by combining the maximum from each
40、distribution and to compare it, such as on Fig. 7, with the regulatory pfd mask. It is also possible, such as on Fig. 7, to plot a similar combined pfd mask representing a given percentage (e.g. 99.9% and 99.5% of the cases). 1602-070 102030405060708090104107110113116119122125128131134137140143FIGUR
41、E 7Aggregate pfd masks for GEO1 model (60 dBi multibeam)Elevation angle (degrees)pfd level(dB(W/(m2 MHz)Regulatory maskMaximum99.9%99.5%Rec. ITU-R SF.1602 9 4.2 Antenna models 4.2.1 Single beam satellite models For a single beam satellite, Figs. 4 and 5 give an adequate representation of the situati
42、on, but the resulting pfd depends on the assumed antenna pattern. Recommendation ITU-R S.672 provides satellite antenna radiation pattern for use as a design objective in the fixed-satellite service employing geostationary satellites. For non-GSO satellites, there is no such general Recommendation,
43、but Recommendation ITU-R S.1528 provides patterns for non-GSO satellites below 30 GHz and guidance for the bands above 30 GHz. It has to be noted that the single beam satellite model may not be appropriate for use in all frequency bands. 4.2.2 Multibeam satellite models For multibeam satellite model
44、s such as the GEO or MEO models described in 3, the representation of the situation is different since in this case the aggregate impact of all the antennas has to be taken into account, as shown on Fig. 8. 1602-08AFIGURE 8Sub-satellite pointMain beam directionElevation xThe pfd value at point A is
45、the aggregation of the pfd produced by each single beam antenna in the direction of point A, each with a specific antenna discrimination (,or in the above example). Based on the regulatory pfd mask, this pfd radiated to A can be calculated as follows: )(1=+=NjAdiscrijmaxmbjmbjLGGLpfdpfdA(5) 10 Rec.
46、ITU-R SF.1602 where: pfdA: pfd radiated to A (dB(W/(m2 MHz) N :number of co-frequency beams per satellite pfdmbj: pfd radiated in the main beam j (dB(W/(m2 MHz) Lmbj: free space losses between the satellite and the centre of the spot beam j at the Earths surface (dB) Gmax: maximum satellite antenna
47、gain (dBi) Gdiscrij: relative antenna gain in the direction of point A for the beam j (dBi) LA:free space losses between the satellite and A (dB). Since these beams are assumed to be co-frequency and due to self-interference issues, their main beams will not cover the same zone at the same time. The
48、refore, except in some cases where (for which none of the main beams covers point A) for which the aggregate pfd is only produced by far side lobes of all the beams, this aggregate pfd will be dominated by one beam at each time. Instead of running complicated calculations involving multibeams scenar
49、ios, the pfd at A can hence be approximated considering one single beam as follows: AdiscrijmaxmbmbALGGLpfdpfd += (6) where: pfdA: pfd radiated in A (dB(W/(m2 MHz) pfdmb: pfd radiated in the main beam (dB(W/(m2 MHz) Lmb: free space losses between the satellite and the centre of the spot beam j at the Earths surface (dB) maxG : maximum satellite aggregate antenna gain (dBi) iscrijdG : relat
