1、CCIR RECflN*FLOOb 93 g855212 0520793 231 W Rec. ITU-R SF.1006 31 SECTION 4/9B: COORDINATION AND INTERFERENCE CALCULATIONS RECOMMENDATION ITU-R SF. 1006 DETERMINATION OF THE INTERFERENCE POTENTiAL BETWEEN EARTH STATIONS OF THE FIXEDSATELLITE SERVICE AND STATIONS IN THE FIXED SERVICE (Questions ITU-R
2、3U4 (1990) and 109/9 (1990)* ( 1993) The ITU Radiocommunication Assembly, considering a) that when the coordination area of an earth station, as established by the methods given in Recommendation IT-R IS.847*, includes territory of another administration, mutual consultation between the administrati
3、ons concerned is required; b) that each station in the fixed service within the coordination area must be examined to determine whether it will experience or cause more than a permissible amount of interference; C) interference evaluation; d) allowing for typical terrain and shielding, are achievabl
4、e (see Fig. I); e) administrations concerned; 0 analysis may nonetheless be of value to some in the detailed coordination and interference evaluation, that Recommendation -R PN.452* provides the requisite propagation bases for individual point-to-point that experience has shown that, in many instanc
5、es, separation distances as small as a few kilometres, when that the methodology for determining the level of interference is a matter for agreement between the that guidance to administrations on the detailed determination of these levels for performing a preliminary recommends that the methods des
6、cribed in Annex 1 may be used for assessing interference potential between earth 1. stations and specific stations in the fixed service within the coordination area. Determination of the interference potential between fixed satellite service earth stations and stations in the fixed service The follo
7、wing method may be used for assessing whether interference between earth stations and specific terrestrial stations can be expected to exceed a pre-determined level. 1. Preliminary elimination procedure The method of calculating coordination area as described in Recommendation ITU-R IS.847* assumes
8、certain reference values for the parameters of terresuial stations. A very large percentage of the actual or planned terrestrial stations within a coordination area can be eliminated from further consideration when their actual or planned parameters are known, by using the auxiliary contours as defi
9、ned in Appendix 28 of the Radio Regulations (Geneva, 1979). * * Former CCIR Questions 3U4 and 109/9. Former CCIR Recommendations 847 and 452. CCIR RECMN*100b 93 4855212 0520794 178 32 Rec. ITU-R SF.1006 One set of contours is associated with values of the terrestrial station interference sensitivity
10、 factor, S which is defined as: where: G, : net gain (dBi) (i.e. the gain of the antenna itself minus the feeder loss (dBi) relative to isotropic; where the feeder loss is not known, its value should be assumed to be O dB) of the receiving antenna of the terrestrial station in the direction of the e
11、arth station permissible interference power (dBW) in the reference bandwidth to be exceeded for no more than p percent of the time at the receiver input of a station suffering interference (in this case a terrestrial station). P,(p) : The other set of contours is associated with values of terrestria
12、l station e.i.r.p.: where: Pi : available transmitting power (dBW) in reference bandwidth B at the input to the antenna of an interfering station (in this case a terrestrial station) Gi : gain (dBi relative to isotropic) of the transmitting antenna of the terrestrial station in the direction of the
13、earth station. Each terrestrial station which is located within the coordination area may now be examined to determine for terrestrial stations which may be receiving interference from the earth station, the interference sensitivity factor in the direction of the earth station should be determined.
14、If this value is less than that associated with the nearest contour outside which the station is located, then the station may be excluded. Otherwise, detailed calculations as described in b 2 must be carried out; for terrestrial stations which may be causing interference to the earth station, the a
15、ctual e.i.r.p. in the direction of the earth station should be determined. If this value is less than that associated with the nearest contour outside which the terrestrial station is located, then the station may be excluded. Otherwise, detailed calculations as described in 0 2 must be carried out.
16、 The above method has been based on the assumption that the number of interference entries assumed in Recommendation ITU-R IS.847* for the calculation of the auxiliary contours is not exceeded. Terrestrial stations eliminated by the above procedure from further consideration with regard to great cir
17、cle propagation mechanisms need, nevertheless, to be considered further with regard to rain scatter propagation, when they lie within the rain scatter coordination area. whether it can be excluded from further considerations: - - 2. Determination of interference potential due to great-circle propaga
18、tion mechanisms, mode (1) Terrestrial stations located within the coordination area, which cannot be eliminated from further consideration by the method described in 4 1 must be subjected to a more detailed analysis. * Former CCIR Recommendation 847. CCIR RECMN+LOOb 93 m 4855212 0520795 004 m RC. mu
19、-R SF.1006 33 For each terrestrial station it is necessary to compare the available basic transmission loss for the path and the minimum permissible basic transmission loss value, at which interference is negligible for two time percentages on the one hand equal to 20% of the time pl, and on the oth
20、er, a low percentage of the time ( 1%) designatedpz. Interference is negligible when, for both time percentages, the available basic transmission loss for the path exceeds the minimum permissible basic transmission loss. 2.1 Level of maximum permissible inegerence The level of permissible interferen
21、ce power at the input of the receiver of a terrestrial or an earth station may, in the most general form, be expressed as the unwanted radio-frequency power Pr from any one of n sources of interference, in a reference bandwidth B, to be exceeded for not more than specified percentages of the time, P
22、i. For most practical purposes two such percentages of the time will be adequate; one, pl, chosen to reflect normal (near median) conditions for which interference contributions from all interference sources may be assumed to occur simultaneously and to add on a power basis, given by: Pr(p1) = lOlog
23、(kTrB) + J - W dBW (3) and another p2, chosen to reflect significantly enhanced (small percentages of the time) interference conditions, for which interference contributions from all interfering sources may be assumed to occur non-simultaneously and to add on a percentage-of-the-time basis, given by
24、: Pr(P2 1 n2) = 10 lg (k T,B) + 10 log (10 - 1) + NL- w dBW (4) M,/ 10 where: Pi, P2 : nl : 112 : k: Tr : B: J: Ms : NL : W: percentages of the time during which the interference from all sources may exceed the permissible level; pl represents long-term (pl 2 1%) and p2 short-term conditions (p2 I 1
25、%) effective number of expected simultaneous equal-level interference contributions, associated with pl (see Notes 1 and 2) effective number of expected non-simultaneous equal-level and equal-percentage-of-time, interference contributions, associated with p2 (see Note 1) Boltzmanns constant: 1.38 x
26、10-23 J/K noise temperature of receiving system (for earth stations under clear-sky conditions), (K) reference bandwidth (Hz) (bandwidth, of concern to the interfered-with system, over which the interference power can be averaged) ratio (dB) of the permissible long-term (20% of the time) interfering
27、 power from any one interfering source to the thermai noise power in the receiving system (see Note 2) fade margin of link (see Note 3) link noise contribution (see Note 4) ratio (dB) of incremental thermal noise power to interference power, at radio frequencies, in the reference bandwidth, for equi
28、vaient post-detection signal degradation (see Note 4 of 5 2.3.1 of Annex 1 to Recommendation ITU-R IS.847*). Numerical values for these parameters are listed in Table 1. * Former CCIR Recommendation 847. CCIR RECMN*300b 93 9 4855232 052077b T40 9 34 RC. ITU-R SF.1006 TABLE 1 Values of parameters rel
29、ating to equations (3) and (4) Frequency range (GHz) 15-40 1-10 10-15 10-15 15-40 Fixed- satellite Fixed Radio- relay 1-10 Fixed-satellite Fixed Radio-relay 1-10 Fixed- satellite Fixed Trans- horizon Fixed Fixed Fixed-satellite Service of interfering system Service Modulation Fixed Fixed- Satellite
30、Earth station N Fixed-s atellite Fixed-s atellite Fixed Earth station Earth station Radio-relay A N A N A N 20 20 20 20 20 20 N 20 20 I I 0.01 I 0.005 1 0.01 I I I I I 0.03 1 0.005 I 0.03 I 0.005 1 0.01 I 0.005 0.003 0.005 I I 21311 31312121213 2 I I I I B Hz) 4x1031 106 14x103 106 106 J (dB) -10 I
31、-10 I -8.5 I -8.5 I 13 I -2P) -7 O 41014101010 750 I 750 I 500 100 I 100 I 200 I 200 I1500 I1500 300 3 200 33 I 37 I 26 2 I2 I4 I4 133137 6 25 O 1 1 1 1 O O O O O A: analogue N: digital (1) The trans-horizon systems are assumed to consist of a single hop. (2) These values are appropriate to the gene
32、ral case of uncorrelated fading of wanted and unwanted signals. Where this fading (due to rainfall) can be assumed to be substantially correlated (Le. when the interference follows the same path as the unwanted signal), values for J different from those shown above may be applicable. (3) To be used
33、in case the values are not available. Note I - The number of possible interferers, n, must be apportioned between those likely to be nearby, ni and those likely to be beyond the horizon, n2. For example, for terrestrial systems operating in the band 1-10 GHz, n is 8. According to Recommendation ITU-
34、R IS.847 n2 = 3, and, consequently, nl = 5. Note 2 - J is the ratio (dB) between permissible long-term interference from any one source and thermal noise in a given station. This parameter is dependent upon ni. In the case of terrestrial systems, if 10% of the total amount of noise (analogue systems
35、) or outage (digital systems) is permitted due to earth stations, of which half is due to nearby stations, and half to stations beyond the horizon, the value of J is given by: - for analogue systems: J = 10 log (40 / ni) (5) * Former CCIR Recommendation 847. CCIR RECHN+1006 93 m 4855212 0520797 987
36、m RM. ITU-R SF.1006 35 - for digital systems: J = 1Olog (fi - 1) where: x = 1 + 3/ni With ni = 5, J = 9 dB for analogue and -6 dB for digital signals. In the case of an earth station, assuming that the thermal noise amounts to no more than 70% of the total noise of the receiver, and allowing long-te
37、rm interference to be 10% of the total noise (Recommen- dation ITU-R SF.558*), J = -8.5 dB, assuming a single interfering source. However, if more than one entry is used, this figure is reduced by 10 log nl. At e 10 GHz, nl, can be assumed as being between 1 and 2. At the higher frequencies, where s
38、ome correlation between the fading of the wanted and interfering signals may be anticipated, an increase in interference allowance might be allowed. In such a case, a 25% allowance for interference instead of 10% may be assumed, and a total J of 4 dB is appropriate, or a J of -7 dB for each interfer
39、- ence source. Note 3 - Ms is the fade margin in the link. See Note 3 of 8 2.3.1 of Annex 1 to Recommendation ITU-R IS.847*. Note4-NL is the noise contribution to the link by the satellite transponder, including the up-link noise, intermodulation, etc. Generally: NL = 1 dB for fixed-satellite links;
40、 NL = O dB for links in the fixed service. 2.2 Minimum permissible basic transmission loss The minimum permissible basic transmission loss for 20% of the time is given by: Lb(20) = Pt. + Gt* + Gr - Pr(20) (8) The minimum permissible basic transmission loss for p% of the time is given by: Lb(p) = Ptp
41、 + Gtt + Gr - Pr(P) (9) where, p = pz/n2 (from Table i), Pp and Gtt are the pertinent parameters of the interfering station on the path of minimum transmission loss, and Gr, Pr (p) and Pr (20) are the pertinent parameters of the station suffering interference on the path of minimum transmission loss
42、. 2.3 Available basic transmission loss A method of calculating the available basic transmission loss between an earth station and a terrestrial station is given in Recommendation ITU-R PN.452*. 3. Determination of interference potential in the presence of precipitation scatter, mode (2) In cases wh
43、ere interference may be due to rain scatter propagation, the minimum permissible transmission loss: UP) = Prt - Pr(P) (10) must be calculated and compared with the loss due to rain-scatter propagation. If the first value is less than the second, then interference due to scattering from precipitation
44、 is negligible. A method of calculating the available transmission loss between an earth station and a terrestrial station where the propagation mechanism is scattering due to precipitation, is given in Recommendation ITU-R PN.452*. * Former CCIR Recommendations 558,847 and 452. CCIR RECMN*1006 93 4
45、855232 0520798 813 D 36 Rec. ITU-R SF.1006 4. Summary Interference between an earth station and a terrestrial station can be considered as negligible when the interference power level for great-circle propagation mechanisms does not exceed the maximum permissible level of interference for 20% of the
46、 time, and also when the interference power level for ail propagation mechanisms combined (i.e., great-circle and rain-scatter propagation mechanisms) does not exceed the maximum permissible level of interference for a small agreed percentage of the time, Nevertheless, the methodology for determinin
47、g in detail the levels of interference is a matter of agreement between administrations concerned. The methods described above may be of value for guidance and preliminary evaluation leading to such detailed coordination. APPENDIX 1 TO APPENDIX 1 Auxiliary contours associated with angular discrimina
48、tion Auxiliary contours assist in the evaluation of the large number of stations which are likely to be found in the There is a small probability that the main beam of a terrestrial radio-relay link will be directed towards an earth station so that for the assessment of propagation mode (1) cases, i
49、t is appropriate to take account of the angular directivity of the terrestrial link antenna. Figure 2 provides a series of contours consistent with 5 dB interval reductions in link antenna gain. A terrestrial station which does not point the main beam of its antenna towards the earth station may be eliminated from further consideration when its actual antenna gain (or that of a reference diagram) towards the earth station is less than that assumed for the determination of the coordination area by at least the gain reduction value that corresponds to the auxiliary contour (see
