1、ITU-R RECMN*S= 741-2 94 Li855212 0523978 5b9 320 Rec. ITU-R 5.741-2 RECOMMENDATION ITU-R S.741-2 CARRIER-TO-INTERFERENCE CALCULATIONS BETWEEN NETWORKS IN THE FIXED-SATELLITE SERVICE (Question ITU-R 49/4) (1992-1993-1994) The ITU Radiocommunication Assembly, considering a) that during the planning st
2、age of a satellite network it may be useful to calculate carrier-to-interference (C/o ratios between carriers of the interfering and interfered-with networks for the purpose of determining levels of interference; b) cl performance degradation; that such calculations depend on the relative geometry o
3、f the satellite network involved; that the carrier-to-interference ratios can be used in the determination of interference levels contributing to d) e) networks in accordance with the Radio Regulations; f) of interference between satellite networks (see for example Recommendation IT-R S.740), that t
4、he carrier-to-interference ratios can be used for all modulation methods and signal types; that the carrier-to-interference calculation may be an element to complete frequency coordination of satellite that alternative methods may be used, by agreement between the administrations concerned, to calcu
5、late levels recommends 1. networks: that when carrier-to-interference ratios (Clis) are used to calculate the levels of interference between satellite - the method shown in Annex 2 of Recommendation ITU-R S.740 be used as the basis for these calculations in so far as geometrical considerations are c
6、oncerned; the methods given in Annex 1 to this Recommendation be used to calculate the interference power in the interfered- with carrier. - ANNEX 1 Determination of carrier-to-interference ratios and baseband noise power for coordination of carriers in the fixed-satellite service (FSS) 1. Types of
7、interfering carriers 1.1 The types of interference experienced by the FSS carriers from adjacent networks can be classified as follows: - noise-like interference; - slowly swept interference arising from a TV-FM carrier modulated only with an energy dispersal (ED) signal; interference from one TV-FM
8、 carrier to another (this category is not addressed in this Annex). - - ITU-R RECMN*S. 741-2 94 4855232 0523980 117 Rec. ITU-R S.741-2 32 1 2. Types of FSS carriers 2. I The types of carriers normally used in FSS networks are: - Analogue: - FDM-FM and CFDM-PM; - TV-FM; - single-channel-per-carrier (
9、SCPC)-FM. - Digitul: - - narrow-band and intermediate bandwidth carriers with and without FEC coding (e.g. SCPC-PSK); large bandwidth carriers (e.&. TDMA, CDMA). 3. Methodologies used to assess interference into FSS carriers 3. I Interference into FDM-FM and CFDM-FM carriers The effect of interferen
10、ce into FDM-FM or CFDM-FM carriers is treated in terms of the baseband interference noise power in a telephony channel and is given by the following expression: 10 log (np) = 87.5 - B - 10 log li) (1) where: tip : i? : c : i : The factor B depends on the signal characteristics of both the desired an
11、d the interfering carriers and the weighted interference power (pWOp) interference reduction factor (dB) power of the desired carrier (W) power of the interfering carrier (W). frequency separation belween the centre frequencies of the two carriers. The expressions for the interference reduction fact
12、or for all types of interfering carriers are given in Recommendation IT17-R SF.766. In the case of CFDM-FM, the applicable value of companding advantage (around 9 dB) should be considered along with the interference power level during speech excitation. 3.2 Interference into a non-FDM-FM carrier The
13、 assessment of interference into a non-FDM-FM carrier depends on the nature (Le. digital or analogue or slowly sweeping) of the interfering carrier and on whether the interfering carrier bandwidth is larger or smaller than the desired carrier occupied bandwidth. Table 1 shows the CI1 ratios for diff
14、erent combinations of the desired and interfering carriers. 3.3 Interference from noise-like digital carriers The ratio of the carrier to interference power in the desired carrier signal bandwidth, for Co-frequency operation of the desired and interfering carriers is given by: C/I = lOlog(c/i) - lOl
15、og(M) fOrBWD Bwia (2) C/Z = 10 log (di) - 10 log (BWD IBWI,) for BWu 5 BWla (3) where: CA : c: 1: ratio (dB) of desired carrier power and the total interference power in the desired carrier bandwidth power of the desired carrier (W) power of one interfering carrier (W) 322 Rec. JTU-R S.741-2 Digital
16、 narrow-band FDM-FM SCPC-FM CFDM-FM BW, occupied bandwidth of the desired carrier TV-FM Digital wide band BW, occupied bandwidth of the interfering carrier Not applicable BW/, : allocated bandwidth of the interfering carrier. C/I= IOlog(c/i)- 10 log (BW,/BW,) Expression (2) takes into account the ef
17、fect of multiple interfering carriers (M) affecting a desired carrier which has a large bandwidth. TABLE I Calculation of carrier-to-interference ratios for FSS carriers interfering carriers FDM-FM or CFDM-FM or with live modulation TV-FM SCPC-FM Or digital narrow- band Digital wideband TV-MF (Energ
18、y dispersal signal modulation only) Case B Wi, wD I Desired carriers I C/I= IOlog(/i)- 10log(BW/BWu) I Not applicable CI1 = 1 O log (di) - A C/I= IOIog(li)- 10 log (BWDIBW) CI1 = I O log (di) - I O log (B W,/ B Wi(,) See details in expression (i) or Rec. ITU-R SF.766 I C/I = 1 o log (di) I (Note i)
19、C/I = 1 o log (di) OW,: BW, : w, : C: i: C/I : A: occupied bandwidth of the desired carrier occupied bandwidth of the interfering carrier allocated bandwidth of the interfering carrier power of the desired carrier (W) power of one interfering carrier (W) ratio (dB) of desired carrier power to the to
20、tal interference power in the desired carrier bandwidth bandwidth advantage factor (dB) as given in expressions (5)-(8). Note I - Use criterion in Recommendation TU-R S.671 if SW, is smaller than energy dispersal bandwidth of the TV-FM carrier and use noise-like interference criterion if BW, is larg
21、er than energy dispersal bandwidth. Noie 2 -The “assigned frequency band” may be used in place of the “occupied bandwidth” and the “allocated bandwidth”, when they are not available. Rec. ITU-R S.741-2 323 For the case of frequency offset between carriers, the resultant C/I can be determined by the
22、following equation: CA 10 log (di) - A where: A : bandwidth advantage factor (dB). The factor A is the ratio of the interfering carrier power contained in the desired signal bandwidth to the total interfering carrier power, under the assumption that the interfering carrier has uniform power spectral
23、 density across its occupied bandwidth. 3.4 Interference from noise-like analogue carriers The ratio of carrier-to-interference power in the desired signal bandwidth due to interfering analogue carriers like FDM-FM or TV-FM modulated by live video is given by: Cl1 = IO log (di) - 10 log (M) for BWU
24、BWI, (4) CIf = 10 log (di) - A for BWn I BWI, (5) where: M 5 BWdBW, A : bandwidth advantage factor (dB). Factor A is the ratio of the interfering carrier power contained in the desired signal bandwidth to the total interfering carrier power. The determination of factor A depends on the spectral char
25、acteristics of the interfering analogue carrier and is the ratio of the integral of the interfering power spectrum over the desired carrier bandwidth to the total power of the interfering carrier. Factor A is the inverse of the frequency-dependent rejection factor (FlX) given in Recommendation ITU-K
26、 SM.337, with the assumption that the receive filter selectivity (H(f) = I. Iowever, if the interfering power spectrum is riot known, a worst case calculation of interference can be iiiatle with the approximation that the power spectral density of the interfering carrier is constant over the bandwid
27、th of tlie desired carrier and is equal to the maximum value. The interfering power can then be calculated as the product of the maximum interfering pciwer spectral density and the occupied bandwidth of the desired carrier, prcivided the result does not exceed the total power of lhe interfering carr
28、ier. Defining the equivalent bandwidth (Wetll) of the interfering carrier as the ratio of its total power to its maximum power spectral density, factor A may be written as: A=O for BWD BW,/ (7) where: i : total power of the interfering carrier io : maximum power spectral density of the interfering c
29、arrier. In the case of interference from FDM-FM or CFDM-FM carriers, the power spectral distribution is very close to Gaussian with an r.m.s. deviation of o and so the equivalent bandwidth can be written as: 3.5 Interference from slowly-swept TV carrier The assessment of interference from slowly swe
30、pt TV is carried out in terms of the ratio of the desired carrier power to the full TV carrier power. 324 Rec. ITU-R S.741-2 ITU-R Recommendations for SEI The criterion for protecting narrow-band carriers from slowly swept TV carrier interference is dealt with in Recommendation ITU-R S.67 1. The noi
31、se-like interference criterion is used for assessing interference potential into wideband carriers whose bandwidths are larger than the energy dispersal bandwidth of the TV-FM carrier. Type of interference The effect of multiple interferers is given by expression (4) if the desired carrier bandwidth
32、 is larger than the allocated bandwidth of the interfering TV-FM carrier. Rec. ITU-R S.466 Rec. ITU-R 5.483 Rec. ITU-R S.523 (1) 4. Protection criteria for FSS carriers Any Noise- like Noise- like Noise-like Recommendations ITU-R S.466, ITU-R S.483, ITU-R S.523, ITU-R S.671 and ITU-R S.735 deal with
33、 the interference noise allowance to be made in the noise budget for FSS carriers. Rec. ITU-R S.671 Rec. ITU-R S.671 Rec. ITU-R S.671 Table 2 shows the single entry interference (SEI) protection criteria for FSS carriers, which have been developed on the basis of the relevant ITU-R Recommendations.
34、Slowly-swept Slowly-swept Slowly-swept TABLE 2 Single entry interference (SEI) protection criteria for FSS carriers FSS carrier FDM-FM CFDM-FM TV-FM Digital SCPC-FM SCPC-FM Digital narrow-band: - with coding - without coding SEI protection criteria API before 1987 I API after 1987 600 pWOp CIN + 14
35、(dB) CIN + I4 (dB) CJN + I4 (dB) 80 pWOp CIN + 14 (dB) CIN + 12.2 (dB) CJN + 12.2 (dB) 13.5 + 2 log (6) - 3 log (ilI0) (dB) CIN + 9.4 + 3.5 log (6) - 6 log (iJ10) (dB) CIN + 6.4 + 3 log (6) - 8 log (il10) (dB) API : Advanced Publication of Information of networks CIN : 6 : ratio (dB) of carrier to t
36、otal noise power which includes all internal system noise and interference from other systems ratio of desired signal bandwidth to peak-to-peak deviation of the TV carrier caused by the energy dispersal signal i : pre-demodulation interference power in the desired signal bandwidth expressed as a percentage of the total pre-demodulation noise power The criteria for noise-like interference are being used for the purposes of coordination. (I)
