1、 STD-ITU-R RECMN S-2324-ENGL 1997 9 4855212 05304Lb 733 9 Rec. ITU-R S.1324 1 RECOMMENDATION ITU-R S. 1324 ANALYTICAL METHOD FOR ESTIMATING INTERFERENCE BETWEEN AND GEOSTATIONARY FIXED-SATELLITE NETWORKS NON-GEOSTATIONARY MOBILE-SATELLITE FEEDER LINKS OPERATING CO-FREQUENCY AND CODIRECTIONALLY (Ques
2、tion IT-R 206/4) (1997) The IT Radiocommunication Assembly, considering a) that the World Radiocommunication Conference (Geneva, 1995) (WRC-95) identified the need to develop, as a matter of urgency, criteria for determining the necessity to coordinate and calculation methods for determining levels
3、of interference, as well as the required protection ratios between networks in the mobile-satellite service (MSS); b) that the WRC-95 allocated the frequency bands 19.3-19.6 GHz and 29.1-29.4 GHz for feeder links of non-geostationary-satellite orbit (GSO) networks in MSS in co-direction with GSO fix
4、ed-satellite service (FSS) systems; c that WRC-95 Resolution 12 1 identified the need to undertake, as a matter of urgency, studies to develop coor- dination methodologies for GSO FSS networks and non-GSO MSS feeder links operating in the bands 19.3-19.6 GHz and 29.1-29.4 GHz on an equal basis; 4 be
5、tween satellite networks; e) that the estimation of interference between non-GSO MSS feeder links and GSO FSS systems should be based on the interference power levels not to be exceeded for a specified percentage of time, the frequency of occurrence and the duration of single events, that there may
6、be a need in general to develop a methodology that could be used to estimate interference recognizing a) that estimating interference between non-GSO MSS feeder links and GSO FSS systems based on computer methods of simulation features high accuracy of the obtained results but they may require consi
7、derable runtime and may not be commonly available; b) that interference between non-GSO MSS feeder links and GSO FSS systems may be estimated using time percentage for non-GSO satellites staying within an area into certain discrimination angles from a direction to a GSO satellite in relation to the
8、earth station concerned; c) that the time percentage for a specified value of an angle between a GSO satellite and a non-GSO satellite in relation to the earth station concerned may be defined using either simulations or by the analytical method described in Recommendation 1T-R 5.1257 or by using ot
9、her methods, recommends 1 and GSO FSS systems co-frequency operating in the same direction. that the method given in Annex 1 may be used for estimating interference between non-GSO MSS feeder links 2 1 0.06 No STD-ITU-R RECMN SmL324-ENGL 1997 11855212 0530417 877 D Rec. ITU-R S.1324 0.87 ANNEX 1 Des
10、cription of analytical method for estimating interference between non-GSO MSS feeder links and GSO FSS networks operating co-frequency and codirectionally For estimating interference from non-GSO MSS feeder links and GSO FSS systems a criterion is specified according to which: - interference power s
11、pectral density, Zo, from feeder links of an non-GSO MSS network (in uplink from earth station and in downlink from satellite being a result of feeder link transmissions to and from all the satellites in a constellation) at the input of receiver of a GSO FSS earth station shall not exceed a certain
12、fraction, x, of receiver thermal noise power spectral density, No, within a specified time percentage, % t. An example of criteria for interference from non-GSO MSS feeder links to GSO FSS receivers given in Table 1 are used in the example in Appendix 1. TABLE 1 11-14 GHz The present method provides
13、 an estimation of the time percentage, % t, based on acceptable interference power spectral density, IO, without using simulation methods. For estimating interference between feeder links of non-GSO MSS networks and GSO FSS systems four cases of possible interference effects between earth and space
14、stations of the networks discussed are analysed. They are: Case I: emissions from non-GSO MSS feeder-link earth stations interfering into GSO FSS receiving space stations (see Fig. I). Case2: emissions from non-GSO MSS feeder-link space stations interfering into GSO FSS receiving earth stations (see
15、 Fig. 2). Case 3: emissions from GSO FSS earth stations interfering into non-GSO MSS feeder-link receiving space stations (see Fig. 3). Cuse4: emissions from GSO FSS space stations interfering into non-GSO MSS feeder-link receiving earth stations (see Fig. 4). STD-ITU-R RECMN S-1324-ENGL 1777 485523
16、2 0530438 70b Rec. ITU-R S.1324 3 FIGURE 1 Non-GSO MSS feeder link earth stations interfering into GSO FSS receiving space stations n GSO “ GSOSS I i Non-GSOSS d_ 1 Non-GSO TGSO ES FIGURE 3 GSO FSS earth stations interfering into non-GSO MSS feeder link receiving space stations FIGURE 2 Non-GSO MSS
17、feeder link space stations interfering into GSO FSS receiving earth stations Non-GSO Non-GSO SS -pFZ!? FIGURE 4 GSO FSS space stations interfering into non-GSO MSS feeder link receiving earth stations - Wantedsignal *- Interference SS: space station ES: earth station STD-ITU-R RECMN S.1324-ENGL 1997
18、 m 4855212 0530417 b42 m 4 Rec. ITU-R S.1324 The interference power spectral density at the receiver input can be calculated using the following expressions: for the “uplink”: Io = Pli + Gli(Q) - Lu + G2w(b) dB(W/Hz) for the “downlink“: Io = P3i + G3i(b) - Ld + G4w(Q) dB(W/Hz) where: P 1 i : interfe
19、ring earth stations transmit power spectral density (dB(W/Hz) P3i : interfering space stations transmit power spectral density (dB(W/Hz) Cl) : interfering earth station antenna gain in the direction of the wanted space station (dB) G2w(b) : wanted space station antenna gain in the direction of the i
20、nterfering earth station (dB) G3i(b) : interfering space station antenna gain in the direction of the wanted earth station (dB) G4w(Q) : wanted earth station antenna gain in the direction of the interfering space station (dB) Lu : Ld: path loss from the interfering earth station to the wanted satell
21、ite (dB) path loss from the interfering satellite to the wanted earth station (dI3). This method is based on defming a part of space limited by a circular conic surface with a vertex angle 2Q (see Figs. 1 to 4). The vertex of the cone coincides with either the interfering or interfered-with earth st
22、ation location and the axis of the cone is always aimed at the GSO satellite. For interference cases 1 and 4 the interference power spectral density into a receiver changes only as a function of angle Q which varies as the non-GSO satellite moves. For interference cases 2 and 3 the interference powe
23、r spectral density into a receiver changes as a function of angle Q, distance R and angle b. Analysis of variations in the interference power spectral density, lo, as a function of Q, b and R shows that a slight increase in angle Q leads to a sharp decrease in the interference power, o, while small
24、changes in distance R and angle b leads to virtually no change. Variations in Gw(b), G3i(b), Lu, Ld, that are functions of distance R and angle b, are therefore insignificant. Based on these features it is appropriate to assume that G2w(b), G3i(b), Lu and Ld are constant. This assumption leads to an
25、 insignificant error of the interference estimates. Therefore for interference cases 2 and 3 the variations in the received interference power spectral density are mainly a function of the angle Q. The time percentage, %f, that non-GSO satellites are within the cone 2Q is a function of the required
26、separation angle Q. For the specified features of the satellite networks concerned, every value of angle Q corresponds to a certain value of Zo at receivers input. For the purpose of estimating the uplink interference, the interfering earth station antenna pattern is used, while for estimating the d
27、ownlink interference, the wanted earth station antenna gain is used. Step I: An acceptable level of interference power spectral density for a specific earth station is derived using the following expression: Io = 10logx + 10log(kT) dB(W/Hz) (3 1 where: x : fraction of the receiver thermal noise powe
28、r spectral density within a specified time percentage, % f, criteria of Table 1 k : Boltzmanns constant (JK) T: noise temperature of the wanted networks receiving station (K). Step 2: Using expressions (1) or (2) (depending if it is uplink or downlink) and the earth station antenna pattern a value o
29、f angle Q, that corresponds to an acceptable interference power spectral density, lo, defined at Step 1, is calculated. STD*ITU-R RECMN S-1324-ENGL 1997 4855232 0530q20 3b4 Rec. ITU-R S.1324 5 Srep 3: Based on the analytical method presented in Recommendation ITU-R S.1257 or based on other methods,
30、a time percentage %t,(Q) that non-GSO satellites are within a cone with a vertex angle 2Qm is calculated. Step 4: Time percentage values calculated at Step 3 are compared with acceptable values (e.g. those given in Table 1). If the calculated value of time percentage %(e), does not exceed a specifie
31、d %tm then the interference is acceptable (based on the criteria used). An example of the given algorithms application for estimating interference between feeder links of an non-GSO MSS network and GSO FSS system is shown in Appendix 1. APPENDIX 1 TO ANNEX 1 Example of estimating interference betwee
32、n non-GSO MSS feeder links and GSO FSS systems sharing the same frequency bands in the same direction The example deals with a case of estimating interference from non-GSO MSS feeder links into a GSO FSS system. The assumptions used are characteristics of a LEO-G-type non-GSO satellite network (h =
33、1 500 km, i = 74O, N= 48) and typical GSO satellite parameters. Estimations are performed for wanted and interfering earth stations at latitudes of O“ and 60, and with the satellite located at the same longitude as the earth station. Estimation results for interference from the non-GSO MSS feeder li
34、nks to the GSO FSS system are presented in Tables 2a) and 2b) for Earth-to-space and space-to-Earth directions respectively. The estimation sequence is as follows. Stage 1: The first stage is the estimation of the acceptable interference level expressed in fraction, x, of a specific receiver noise p
35、ower spectral density, NO, within the time percentage, % tm, specified for the given frequency band. The following formula was used: Io = 10 logx -t 10 log(kT) dB(W/Hz) In Tables 2a) and 2b) the specified time percentage %t, (column 2) have appropriate values of NO (column 4), x (column 5) and an es
36、timated threshold interference value (xNo), (column 6). Stage 2: At the second stage, using expressions (1) or (2) (depending if it is uplink or downlink) and the earth station antenna pattern, the values of angle (Qm) corresponding to an acceptable noise power spectral density (XNO) defined at the
37、first stage was calculated. The values of Q, are presented in column 11 of Tables 2a) and 2b). Stage 3: At the third stage a time percentage %t(Q), of non-GSO satellites being within a cone with a vertex angle (2Qm) calculated using the analytical method presented in the Recommendation ITU-R S. 1257
38、 (see column 12). Stage 4: At the fourth stage the calculated time percentage values were compared with acceptable values (those given as an example only in Table 1). The estimation results presented in Tables 2a) and 2b) show that the interference levels from the non-GSO MSS feeder link stations into the GSO FSS stations would not comply with the short-term criteria (xN& using in this example. h s .- U y1 .- I! .- I = C O .- *, L 3 m i i : t- I I- II L m O m O
