1、 Rec. ITU-R S.1588 1 RECOMMENDATION ITU-R S.1588 Methodologies for calculating aggregate downlink equivalent power flux-density produced by multiple non-geostationary fixed-satellite service systems into a geostationary fixed-satellite service network*(Question ITU-R 236/4) (2002) The ITU Radiocommu
2、nication Assembly, considering a) that the World Radiocommunication Conference (Istanbul, 2000) (WRC-2000) adopted the combination of single-entry validation, single-entry operational and, for certain antenna sizes, single-entry additional operational downlink equivalent power flux-density (epfd) li
3、mits, contained in Article 22 of the Radio Regulations (RR), along with the aggregate limits in Resolution 76 (WRC-2000), which apply to non-geostationary (GSO) fixed-satellite service (FSS) systems, to protect GSO networks in parts of the frequency range 10.7-30 GHz; b) that WRC-2000 adopted Resolu
4、tion 76 (WRC-2000) which resolved “that, in the event that the aggregate interference levels in Tables 1A to 1D are exceeded, administrations operating non-GSO FSS systems in these frequency bands shall take all necessary measures expeditiously to reduce the aggregate epfd levels to those given in T
5、ables 1A to 1D, or to higher levels where those levels are acceptable to the affected GSO administration”; c) that the single entry epfdvalidation limits in RR Article 22 were derived from the aggregate epfdmasks contained in Resolution 76 (WRC-2000) assuming a maximum effective number of non-GSO FS
6、S systems of 3.5; d) that ITU-R, using software based on the specification in Recommendation ITU-R S.1503, will evaluate each non-GSO FSS system for compliance with the single entry validation epfdlimits; e) that the software referred to in considering d) takes into account worst-case non-GSO FSS op
7、erating conditions; f) that, according to RR No. 22.5K, administrations operating or planning to operate non-GSO FSS systems in parts of the frequency range 10.7-30 GHz will ensure that the actual aggregate interference into GSO FSS and GSO broadcasting-satellite service (BSS) networks caused by suc
8、h systems operating co-frequency in these frequency bands does not exceed the aggregate power levels in Resolution 76 (WRC-2000); _ *This Recommendation should be brought to the attention of Radiocommunication Working Party 6S. 2 Rec. ITU-R S.1588 g) that the actual aggregate non-GSO FSS epfdinterfe
9、rence statistics into GSO FSS and GSO BSS networks can only be assessed through calculation; h) that methodologies are needed by administrations in order to determine compliance with aggregate epfdlimits; j) that non-GSO FSS systems have a variety of orbital and operating characteristics and must co
10、ordinate under the provisions of RR No. 9.12 and are likely to implement interference mitigation techniques in order to operate co-frequency with each other; k) that some of the technical characteristics of the non-GSO FSS constellations are available in RR Appendix 4, ITU-R Recommendations and othe
11、r published information on the non-GSO FSS system; l) that the detailed mitigation techniques used by each non-GSO FSS system as mentioned in considering j), as well as other proprietary information such as the beam switching strategy, and traffic loading on each beam of the non-GSO FSS system may n
12、ot be publicly available; m) that it is likely that the maximum epfdinterference from different non-GSO FSS systems will occur at different locations on the Earth, and since they will have different epfdcharacteristics it is likely that more than 3.5 actual non-GSO systems could operate and still be
13、 below the aggregate epfdlimits in Resolution 76 (WRC-2000); n) that one of the uses of the methodologies given in this Recommendation could be to compare the aggregate epfdlevels produced by multiple non-GSO systems when evaluating the joint compliance of four or more operating or planned non-GSO s
14、ystems with the aggregate epfdlimits; o) that Resolution 76 (WRC-2000) invited ITU-R to develop, as a matter of urgency, a suitable methodology for calculating the aggregate epfdproduced by all non-GSO FSS systems operating or planning to operate co-frequency in parts of the frequency range 10.7-30
15、GHz into GSO FSS and GSO BSS networks, and a recommendation on the accurate modelling of interference from non-GSO FSS systems, recommends 1 that the methodology(ies) described in Annex 1 (see Note 1) be used for calculating the aggregate epfdproduced by multiple non-GSO FSS systems operating or pla
16、nning to operate co-frequency in the frequency bands given in Resolution 76 (WRC-2000) into earth station of GSO FSS networks, and be used to determine whether the systems are in compliance with the aggregate epfdlevels given in Resolution 76 (WRC-2000); 2 that Methods 1A or 1B may be used to perfor
17、m an initial evaluation to determine if the aggregate epfdlevels in Resolution 76 (WRC-2000) are exceeded using the satellite pfd approach of Recommendation ITU-R S.1503, when different earth station test points are available for each non-GSO FSS system; Rec. ITU-R S.1588 3 3 that if the evaluation
18、in recommends 2 indicates that the aggregate epfdlevels given in Resolution 76 (WRC-2000) are exceeded then an evaluation using Methods 2A or 2B should be performed at the same set of earth station test points; 4 that, when the evaluation referred to in recommends 3 indicates that the aggregate epfd
19、levels would be exceeded, a more accurate evaluation using Methods 3A or 3B should be performed using coordination, operating and mitigation strategies employed between non-GSO systems and identifying the maximum pfd levels that could be produced on the Earth. NOTE 1 The methods in Annex 1 may be us
20、ed individually or in the sequence as suggested in recommends 2, 3 and 4. For the determination of the exceedance of the epfdlevels the most accurate methodology in recommends 2 to 4 should be used taking into account the availability of detailed information on the non-GSO systems. ANNEX 1 Methodolo
21、gies for calculating aggregate epfd1 Introduction Three methods for calculating aggregate epfdby simulation alone or simulation and convolution are described in this Annex: Methods 1 and 2 rely on the use of Recommendation ITU-R S.1503 for checking the compliance of a non-GSO system with the validat
22、ion limits in RR Article 22 (Tables 22-1A, 22-1B and 22-1C), and differ in the choice of the set of test points. Method 3 proposes more detailed modelling along the lines of Recommendation ITU-R S.1325 and allows for simultaneous simulations of all the non-GSO systems. In each method, one or more op
23、tions being proposed is based on convolution. The convolution options assume a means of generating single entry epfdcurves for specified locations on the Earth. The additional software to do the convolution merely performs a mathematical function and therefore does not require an additional software
24、 recommendation. However, the convolution options are potentially less accurate than the straightforward simultaneous simulation of non-GSO systems. The convolution options will lead to extremely low probabilities for the highest power epfdlevels. Therefore, it is proposed to truncate the calculated
25、 aggregate curve at epfdlevels exceeded for the shortest percentage of the time somewhere before the 0% point in the aggregate epfdcurve. The convolution options assume that the interference from multiple non-GSO systems is uncorrelated. This may not be a good assumption since all non-GSO systems ar
26、e required to use mitigation techniques to avoid interfering with GSO systems and other non-GSO systems. The use of simultaneous simulations are to be used to cover this case. The three methods that are described in this Annex are increasingly accurate and as a consequence increasingly complex to ru
27、n. The choice of the method to be used is likely to depend on the information available to the party that carries out the calculations. In the case of Methods 1 and 2 4 Rec. ITU-R S.1588 the calculation relies on the information provided to the Radiocommunication Bureau (BR). Method 3 goes into more
28、 detail of the non-GSO system and departs from the satellite pfd mask approach of Recommendation ITU-R S.1503 to permit simulations that take into account the coordination, operating and mitigation strategies agreed between non-GSO system operators. 2 Method 1: Convolution of the envelope of single
29、entry epfdcurves at several test points This method uses single entry epfdcurves generated using Recommendation ITU-R S.1503. These curves will be readily available from the BR validation assessment required of each non-GSO system. The BR will check the compliance of a non-GSO system at a single tes
30、t point as defined in Recommendation ITU-R S.1503. This method, however, also covers the case where several points would be tested for a given non-GSO system, in which case the corresponding single entry epfdcurves would need to be produced. Since this option does not use common test locations for a
31、ll non-GSO systems it can only be used to provide a preliminary check of the aggregate limits. There are two ways that this method can be implemented. The first option is to convolve with each other one single entry epfdcurve from each non-GSO system to generate an aggregate mask. Therefore, if ther
32、e are N non-GSO systems under test then each aggregate epfdcurve is the convolution of N single-entry epfdcurves. The result of this convolution is compared to the aggregate limit to determine if there is an exceedance. This method would require the single entry epfdcurve from each test location of
33、each non-GSO system to be convolved with the single entry epfdcurve from each test location of all other non-GSO systems. Thus if there are M test locations for each of the N non-GSO systems then MNconvolutions are required. In this instance M refers to the test locations examined by BR. As an examp
34、le consider two non-GSO systems each with three single entry epfdcurves generated using the satellite pfd mask approach in Recommendation ITU-R S.1503 at three different test locations. The first non-GSO system is evaluated at test locations A, B and C while the second system is evaluated at test lo
35、cations D, E and F. In this case nine convolutions are required (see Table 1). Before convolving epfdcurves, the power values in dBW must be changed to numeric values. If no exceedance is detected for any of the resulting convolutions, then the non-GSO systems under test meet the aggregate limit req
36、uirement. However, if there is a determination that the limits have been exceeded then further investigation using Methods 2 or 3 will be required. TABLE 1 Example of a MN(M = 3, N = 2) convolution matrix A B C D A*D B*D C*D E A*E B*E C*E F A*F B*F C*F Rec. ITU-R S.1588 5 A second implementation of
37、this method is to produce for each non-GSO system a cumulative density function (CDF) envelope curve that bounds all the single entry epfdcurves (i.e. curves representing all the test locations) for each non-GSO system. This is illustrated in Fig. 1 for a non-GSO system with three test locations. 15
38、88-01200 160epfd(dB(W/(m2 40 kHz)Percentageof timeepfdmay be exceededEnvelopeLocation ALocation BLocation CFIGURE 1Example epfdenvelope CDF curveTest CDF 1Test CDF 2Test CDF 3EnvelopeIn this second implementation option, an aggregate test mask is calculated based on the convolution of the envelope o
39、f all the epfdCDF curves of the non-GSO systems under consideration. The convolution of the epfdenvelope CDF curves is compared to the aggregate limits to determine if there is an exceedance. The example below demonstrates that this second implementation is equivalent to the first and has the advant
40、age that only one convolution is required between the two non-GSO systems. In the case of n non-GSO systems there would be n 1 convolutions. 2.1 Example of method As an example, epfdcurves for two non-GSO satellite systems are shown in Figs. 2 and 3. Each Figure shows curves taken at three separate
41、points, as well as the envelope of the three. For reference, the aggregate limits are also shown. 6 Rec. ITU-R S.1588 1588-02200 150190 180 170 1601101103105107102104106108epfd(dB(W/(m2 40 kHz)CDFFIGURE 2epfdcurve from non-GSO system 1epfd1 EnvelopeAggregate limitsepfd3epfd21588-03200 150190 180 170
42、 1601101104107102105108103106epfd(dB(W/(m2 40 kHz)CDFFIGURE 3epfdcurve from non-GSO system 2epfd4 EnvelopeAggregate limitsepfd5epfd6Rec. ITU-R S.1588 7 The first implementation of this method as discussed above requires nine convolutions. Figure 4 shows the final results using the two implementation
43、 options. For the first one, the envelope of the nine individual convolutions is taken. For the second one, the convolution of the two envelopes shown above in Figs. 2 and 3 is taken. It is seen that the two implementations arrive at the same results. 1588-04200 150190 180 170 1601101104107102105108
44、1031061091010epfd(dB(W/(m2 40 kHz)CDFFIGURE 4Cumulative distributionsMethod 1AMethod 1BAggregate limits3 Method 2: Convolution or simulation to calculate the aggregate epfdat the same earth station test points This option can be implemented in two ways using Recommendation ITU-R S.1503. The first op
45、tion (Method 2A) requires that epfdcurves would be generated at the same GSO FSS earth station test location for each non-GSO system using Recommendation ITU-R S.1503 (BR software). In this case, a non-GSO system epfdcurve, for a test point, would be convolved with the epfdcurves of all other non-GS
46、O systems under consideration at that same test location. Appropriate test locations would be selected according to the characteristics of each constellation. The second option (Method 2B) would be to input the data for multiple non-GSO systems into the BR software (as a single constellation with di
47、ffering orbital planes and satellite pfd masks) to generate an aggregate epfdmask. While the short-term or highest epfdlevels of a non-GSO system are usually the most critical, they do not always reflect the distribution of the long-term epfdlevels of each constellation. In other words, the aggregat
48、ion of the epfdshort-term interference at a location does not mean this location also suffers the worst-case long-term interference. 8 Rec. ITU-R S.1588 Appropriate test locations would be selected according to the goal of the calculation being performed and/or the characteristics of each constellat
49、ion. Since the same test locations are used for each non-GSO system this method is more representative than Method 1 of the maximum aggregate levels that can be received at a given earth station location. 3.1 Assumptions and inputs for Method 2 The single entry epfdcurves for each non-GSO system can be generated using Recommendation ITU-R S.1503. The BR software and the required input data for Recommendation ITU-R S.1503 will be available at the BR for us
