1、 Rec. ITU-R F.1494 1 RECOMMENDATION ITU-R F.1494 INTERFERENCE CRITERIA TO PROTECT THE FIXED SERVICE FROM TIME VARYING AGGREGATE INTERFERENCE FROM OTHER SERVICES SHARING THE 10.7-12.75 GHz BAND ON A CO-PRIMARY BASIS (Question ITU-R 127/9) (2000) Rec. ITU-R F.1494 The ITU Radiocommunication Assembly,
2、considering a) that it is desirable to determine the protection criteria of fixed service (FS) systems operating in the 11/12 GHz (10.7-12.75 GHz) band with respect to aggregate interference from systems operating co-primary, especially short-term interference; b) that in interference situations inv
3、olving non-geostationary satellites (non-GSO) space stations, FS systems are potentially exposed to high levels of interference for short periods of time which could affect the performance or availability of these systems; c) that the FS link design in the 11/12 GHz band is controlled by multipath f
4、ading, which can be modelled using Recommendation ITU-R P.530; d) that in the 11/12 GHz band, some administrations employ automatic transmit power control (ATPC) on some FS links and that the use of ATPC will increase the susceptibility of FS systems especially with regard to short-term interference
5、; e) that some FS systems employing small net fade margins may not be fully protected from interference from non-GSO satellite systems without unduly constraining those services; f) that typical FS links using ATPC will require tighter protection criteria than those needed for FS links with large fa
6、de margin that do not use ATPC; g) that it is desirable to derive the aggregate FS protection criteria based on the calculation of the allowable degradation of error performance objective (EPO) due to interference, considering typical FS links using ATPC features; h) that the determination of the ma
7、ximum degradation of EPO allowable to interference from other services sharing the same frequency band on a co-primary basis is given in Recommendation ITU-R F.1094; j) that Recommendations ITU-R F.1092 and ITU-R F.1189 give the EPO allowable for constant bit rate digital path at or above the primar
8、y rate carried by digital radio-relay systems which may form part of, respectively, the international and national portion of a 27 500 km hypothetical reference path (HRP); k) that the allowable degradation in performance of FS systems due to interference from other services sharing the same frequen
9、cy bands on a primary basis, expressed as a permissible fraction of the total EPO is defined in Recommendations ITU-R F.1241 and ITU-R F.1398 for the FS systems which may form part of, respectively, the international and national portion of a 27 500 km HRP, recognizing a) that the application of the
10、 criteria in this Recommendation may be subject to further consideration within sharing studies with other services; b) that any further development of this Recommendation that may be necessary is unlikely to require further study of the appropriateness of the non-GSO satellite fixed satellite servi
11、ce (FSS) power flux-density (pfd) limits in this band, 2 Rec. ITU-R F.1494 recommends 1 that the following interference criteria should be used to protect the FS from time varying aggregate interference from other services in the 10.7-12.75 GHz band on a co-primary basis: 1.1 for the short term, the
12、 I/N at the input of the FS receiver should not exceed +20 dB; 1.2 for the long term, the FDP (fractional degradation of performance as described in Recommenda-tion ITU-R F.1108) or DltEPO(long-term degradation on error performance objectives), should not exceed 10%: %100d)(89,01106Gf7Gf7Gf7Gf8Gf6Ge
13、7Ge7Ge7Ge8Ge6Gf2tNtIDltEPO2 that the information contained in Annex 1 should be used as guidance for the use of this Recommendation. ANNEX 1 Derivation of FS aggregate protection criteria in the 11/12 GHz band 1 Introduction This Annex aims to give numerical examples concerning the assessment of int
14、erference criteria in the 11/12 GHz band. The interference is considered to be aggregate from all co-primary services. These examples (see Recommendation ITU-R P.530) are based on the following typical FS links (the fade margins are given for a 1 10 3BER): link with 37 dB fade margin, part of the in
15、ternational portion of the hypothetical reference path (HRP) (qt= 4.2); link with 47 dB fade margin, part of the international portion of the HRP (qt= 2.2); link with 37 dB fade margin, part of the national portion of the HRP (qt= 2.2). The methodology proposes to calculate the performance degradati
16、on due to a given short-term criterion (i.e. I/N = 20 dB for 1 10 4% of the time) in order to verify its adequacy and then to give the rest of the interference allowance to the long term on the basis of an integration of the interference distribution with the fading. 2 Short-term criterion The degra
17、dation due to a given interference short-term criterion (i.e. I/N = 20 dB for not more than 1 10 4% of the time) is the probability of the simultaneous effect of this criterion and a fading higher than the net fade margin (F), defined as follows: F = FM ATPCrange I/N dB where, for example: FM: fade
18、margin ATPCrange= 13 dB I/N = 20 dB. Rec. ITU-R F.1494 3 Therefore, the degradation due to this short-term interference, DstEPO, is given by the following formula as a percentage of the EPO allowance: DstEPO= A% p(I/N 20 dB)/EPO where: EPO: error performance objective F: net fade margin A% = p(f F):
19、 the percentage of time that a fade depth F is exceeded (see Recommendation ITU-R P.530). Tables 1 and 2 give the results of the calculation for the three typical links considering the errored second (ES) and severely errored second (SES) objectives. These calculations show that the proposed short-t
20、erm interference criterion (i.e. I/N = 20 dB for 1 10 4% of the time) never leads to an EPO degradation greater than 10% which is the total EPO degradation allowable to total interference and, except in one case, is much lower than 1% which is representative of an apportionment of 10%/90% for, respe
21、ctively, short term and long term. It has to be noted that, for the 37 dB FM international link, which already represents a worst-case calculation as far as it leads to a qtvalue of 4.2 dB, the percentage drops to 1.2% when considering an ATPC range of 12 dB instead of 13 dB. TABLE 1 TABLE 2 Link pa
22、rt of an international portion Link part of a national portion FM (SES) (dB) 37 47 37 FM 1 dB (for SES) (dB) 36 46 36 Net margin (for SES) (dB) 3 13 + 13 3 A = % fading net margin (%) 3.3 1.2 1026.7 Probability of event = A 10 4(%) 3.3 10 61.2 10 86.7 10 6Total EPO allowable to the link (%) 1.2 10 4
23、1.2 10 47.5 10 3Degradation (DstEPO) (%) 2.7 0.01 0.09 Link part of an international portion Link part of a national portion FM (ES) (dB) 37 47 37 FM 5 dB (SES) (dB) 32 42 32 Net margin (ES) (dB) 0 9 0 A = % fading net margin (%) 63 5.2 10163 Probability of event = A 10 4(%) 6.3 10 55.2 10 76.3 10 5
24、Total EPO allowable to the link (%) 9.6 10 39.6 10 36 10 1Degradation (DstEPO) (%) 0.65 0.005 0.01 4 Rec. ITU-R F.1494 Furthermore, and since the low percentage of time associated to this criterion is equivalent to less than 3 s/month, the I/N level (20 dB) of this criterion can be considered as a h
25、ard limit. 3 Long-term interference criteria Based on the above consideration, it is proposed, in the case where I/N statistics never reach the maximum short-term interference level (+20 dB), to allocate the full interference allowance (10%) to the long-term interference. In the particular case wher
26、e the I/N statistics reach the +20 dB maximum value (without exceeding it), then it is proposed to calculate the long-term interference criteria by subtracting the EPO degradation due to short-term interference, i.e. DstEPO, from the full interference allowance (10%). As an example, considering the
27、worst case given in Table 2 (37 dB FM/international link), this leads to a long-term objective of: 10 2.7 = 7.3%. The degradation due to a long-term interference DltEPOcould then be estimated using the FDP approach (see Recommendation ITU-R F.1108) or by the following equation: %100d)(89.01106Gf7Gf7
28、Gf7Gf8Gf6Ge7Ge7Ge7Ge8Ge6Gf2tNtIDltEPO4 Further considerations of ATPC in long-term interference criteria Although FDP as provided in Recommendation ITU-R F.1108 may be sufficient for receivers without ATPC, the FDP for receivers employing ATPC may require additional consideration if I/N values excee
29、d the full-power working range, Aw, of the ATPC. The full-power working range of the ATPC is defined as: ThresholdRangewAAFMA = For receivers employing ATPC, it can be shown that the FDP may be expressed as: FDPFDPFDP +=0where FDP0is the usual FDP as derived in Recommendation ITU-R F.1108 and given
30、here as: Ge5=kAllkknifFDP )/(0and the contribution due to ATPC and interference is given by: Ge5+=cwkkkkAnifFDP )/(1()110(1.0It is assumed here that (i/n)k+1is greater than (i/n)kand that kcis the largest index for which: ()wkAni + )/(1log10 Some calculations show that, for the cases considered, an
31、additional long-term I/N criterion of I/N to exceed 15 dB for no more than 0.001% of the time would lead to an additional degradation, FDP, of about 1%. Thus, this I/N criterion would limit the sharing burden of receivers employing ATPC to about 1%. Rec. ITU-R F.1494 5 An alternative approach to det
32、ermining DltEPOfor receivers employing ATPC is given as follows: DltEPO %100d)(10d)(89.06101.01GfaGfaGfaGfbGf9GeaGeaGeaGebGe9Gf7Gf7Gf7Gf8Gf6Ge7Ge7Ge7Ge8Ge6+Gf2Gf2fwftAttNtItNtIwhere: I(t): interference power (W) that is exceeded for the fraction of time t tf: fraction of time that I(t)/N (dB) exceeds Aw. It should be noted that in some of these cases where high I/N values are considered, the long-term criteria as described in 3 may provide the required FS protection.
