1、STD-ITU-R RECMN M.1231-ENGL 1797 Lib55212 0527Lib7 bL2 W RC. ITU-R M.1231 433 RECOMMENDATION ITU-R M. 123 1 INTERFERENCE CRITERIA FOR SPACE-TO-EARTH LINKS OPERATING IN THE MOBILE-SATELLITE SERVICE WITH NON-GEOSTATIONARY SATELLITES IN THE 137-138 MHz BAND (Question ITU-R 83/8) (1997) Summary In this
2、Recommendation, the interference criteria for downlinks of FDMA non-GSO MSS networks and SSMA non-GSO MSS networks are recommended in terms of the maximum aggregate interference levels. The ITU Radiocommunication Assembly, considering a) the presence of interference; b) that interference criteria ma
3、y be determined using the methodology described in Recommen- dation ITU-R SA. 1022 and the performance objectives specified in Recommendation IT-R 1230; that interference criteria are needed to ensure that systems can be designed to achieve adequate performance in c) operating in other services; tha
4、t interference criteria assist in the development of criteria for sharing bands among systems, including those d) equal to the permissible levels; that systems in the rnobile-satellite service (MSS) in the 137-138 MHz band must accept interference at least e) that two general types of modulation are
5、 to be considered for non-geostationary (non-GSO) MSS operating in the 137-138 MHz band, which are: narrow-band modulation with frequency division multiple access (FDMA), and wideband modulation with direct sequence spread spectrum multiple access (DS-SSMA); f) of interference in the mobile-satellit
6、e service in the 137-138 MHz band, that Annex 1 presents the parameters of two representative systems that provide the basis for permissible levels recommends 1 antenna input of receiving stations operating in the MSS in the 137-138 MHz band; that the interference levels specified in Table 1 be used
7、 as the total level of interfering signal power at the 2 NOTE 1 - The total interfering signal power level that may be exceeded forp% of the time, wherep is less than 20% but greater than the specified short-term time percentage, may be determined by interpolation between the specified values using
8、a logarithmic scale (base 10) for percentage of time and a linear scale for interfering signal power or signal power density (a) (see Fig. 1) . NOTE 2 - Using the guidelines in Recommendation ITU-R SA.1022, the permissible levels of interference may be scaled for application to stations with antenna
9、 gain or bandwidth values that differ from the specified values. NOTE 3 - The interference criteria are based on the systems described in Annex 1. The interference criteria for systems using narrow-band modulation with FDMA techniques are given in terms of power levels in the reference bandwidth of
10、the ground station receiver. The interference criteria associated with wideband modulations with DS-SSMA are given in terms of total power contribution of potential interferers in the 137-138 MHz band regardless of the bandwidth of the interferer. NOTE 4 - The interference criteria are specified wit
11、h respect to the percentage of time of reception. that the interference levels defined herein are used as a basis for deriving sharing criteria. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services434 Rec. ITU-R M.1231 NOTE 5 - The interfe
12、rence criteria for the wideband system is predicated on the link budget provided in Table 3. One of the main constraints in developing this link budget is a reduced power flux-density (pfd) required to protect the existing operations of the meteorological-satellite (MetSat) service. This reduction i
13、n pfd necessitates a decreased link margin for the wideband non-GSO MSS system, resulting in more restrictive interference criteria than would result in the absence of the MetSat operations. When the MetSat operations move to the 137.025-137.175 MHz and the 137.825 -138.0 MHz bands, the pfd from the
14、 future wideband non-GSO MSS may be increased with a corresponding increase in the interference criteria. TABLE 1 Interference criteria for stations in the mobile-satellite senice in the 137-138 MHz band Modulation type NmO W-band modulation and FDMA NmO W-band modulation and FDMA Wideband modulatio
15、n and SSMA (see Note 5) Function, and earth station platform and antenna Data downlink to gateway (1 5 dBi horn antenna) Reference bandwidth is 44 kHz Data downlink to subscriber terminal (O dBi monopole antenna with a cos2 pattern) Reference bandwidth is 19.2 kHz Data downlink to gateway (1 6 dBi a
16、ntenna) Reference bandwidth is 885 kHz Interfering signal power (dBW) in the reference bandwidth to be exceeded for no more than 20% of the time() -142.1 -155.3 -134.5 Interfering signal power (dBW) in the reference bandwidth to be exceeded for no more than 2% of the tirnec2) -133.4 -144.5 -128.5 (I
17、) The interfering signal power level is determined during reception at elevation angles equal to or greater than 20“. (2) The interfering signal power level is determined during reception at elevation angles equal to or greater than5“ and for p2 = 0.25. FIGURE 1 Interference criteria model O 20 40 6
18、0 80 100 Time (%) om83 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTDWITU-R RECMN fl.1231-ENGL 3997 4855232 05274b9 Li95 = Rec. ITU-R M.1231 435 ANNEX 1 Basis for interference criteria 1 Introduction This Annex presents the parame
19、ters used as inputs to the methodology described in Recommendation ITU-R SA.1022 to determine the interference criteria. Tables 2 and 3 summarize these parameters. Additionally, 5 5 presents the results of a dynamic analysis which involved computer modelling and simulations which were used to verify
20、 the calculated interference levels for the narrow-band system. 2 Non-GSO MSS in the 137-138 MHz band using narrow-band modulation with FDMA The MSS operating below 1 GHz in non-GSO orbits operates downlinks in the 137-138 MHz band. Typical mobile terminals use an omnidirectional antenna with a O dB
21、i gain at low elevation angles, and typical gateway earth stations use a conical horn antenna with a 15 dBi gain. 3 Non-GSO MSS in the 137-138 MHz band using wideband modulation with DS-SSMA For spread-spectrum transmissions, reception by mobile terminais is not contemplated at the moment. Only gate
22、way earth stations are considered here. They use a directive antenna with a 16 dBi antenna gain. 4 Interference criteria The interference criteria establishes the total power from ail potential interference sources that a system can tolerate and still provide an acceptable grade of service. Using th
23、e systems link budget and the performance objectives specified, the total interference power level is calculated. This level is determined by taking the margin available in the link, making some simplifying assumptions as explained in Recommendation ITU-R SA. 1022 and separating it into a long-term
24、and a short-term interference criteria (see equations (1) and (2), respectively). where: i20 : long-term interference criteria (dBW) npl : noise power for the time the link is unavailable (dBW) Mpl : short-term margin for the time the link is unavailable (dB). $2 = n20 + 10 log (10.M20 - 1) where: $
25、2 : short-term interference criteria (dBW) n20 : noise power to be exceeded for no more than 20% of the time (dBW) M2o : long-term link margin (dB). It is assumed that the long-term interference criteria is to be limited to less than 20% of the time and that the link is faded. In addition, in order
26、to arrive at the long-term criteria, it is assumed that 33% of the short-term intra-system noise power be allowed as inter-system interference (i.e. an IIN = -4.8 dB). The short-term interference criteria is specified as the interfering signal power level that is to be exceeded for no more than some
27、 small percentage of time; it is assumed COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesTABLE 2 Performance factor Performance analysis used as a basis for interference criteria for narrow-band modulation with FDMA mobile-satellite re
28、ceivers operating in the 137-138 MHz band Parameter value Parameter value Frequency range (MHz) Per cent time Link function - 137-138 1 .o I 20 I 1 .o 1 20 Data downlink, subscriber Data downlink, gateway receiver receiver I 1. Transmitter output power (dBW) 2. Filtekable line losses (dB) I Modulati
29、on twe I DPSK I OOPSK I 13.1 7.1 1 1.4 5. Antenna pointing error (dB) 6. Antenna gain (dBi) 7. Eira. (dBW) 0.2 O 3.5 3.1 0.8 15.4 15.0 6.5 8. Antenna elevation angle 9. Satellite altitude (km) 5“ I 20“ 1- 5“ 20“ 775 10. Free-space loss (dB) 11. Excess path loss including fading, etc. (dB) STD*ITU-R
30、RECMN H-LZ3L-ENGL 1997 9855212 0527470 LO7 M 436 Rec. ITU-R M.1231 that the link is not faded. Of the 1% unavailability, 25% of this time is the unavailability allowed due to inter-system interference sources. Also, it is important to note that as explained in the methodology, the long-term interfer
31、ence criteria is calculated using the short-term margin and the short-term interference criteria is calculated using the long-term margin. I 139.9 143.9 139.9 143.9 5 1 1 12. Receiver antenna gain (dBi) 13. Antenna pointing error (dB) 14. Polarization mismatch loss (dB) O -0.5 15 O 0.2 4.1 o. 1 15.
32、Demodulator implementation loss (dB) 16. Received signai power (dBW) 3 -140.6 I -133.5 I -126.7 I -122.72 17. Reference bandwidth (kHz) 18. Reference bandwidth (dB) 19. Received energy Cn (or Eh)(dB(W/Hz) 19.2 44.0 42.8 46.4 -183.5 I -176.4 -173.15 I -169.16 20. Receiver system noise temperature (K)
33、 21. Receiver noise spectral density (dB(W/Hz) 724 955 -200 -198.8 22. Adjacent channel interference power (dB(W/Hz) 23. Total system I+ Npower density (dB(W/Hz) -210.6 -207.1 400 -199.6 -199.2 -198.8 25. Link bit error ratio 27. Data storagehandling error ratio 1 x 10-5 1 x 10-6 _- 28. Total bit er
34、ror ratio 29. Required CdNo I 1 x 10-6 1 x 10-5 10.3 10.6 30. Margin Long-term or short-term margin (dB) 5.9 12.6 15.05 19.04 12.6 5.9 19.04 15.05 (20%) (0.25%) (20%) (0.25% Interference power (dBW in reference bandwidth) Interference power (dB(W/4 kHz) -144.5 -155.3 -133.4 -142.1 -151.3 -1 62.1 -14
35、3.4 -152.1 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTDOITU-R RECMN M-la23L-ENGL 1797 9855212 O529Li7L 041 Rec. ITU-R M.1231 437 TABLE 3 Performance analysis used as a basis for interference criteria - wideband modulation with D
36、S-SSMA Link function: Modulation type: MSK/DS-SSMA Frequency range: 137- 138 MHz Data downlink to gateway receiver Per cent time I 0.1% 20% 1 I I Elevation I 5“ 20“ 1 Transmitter output power (dl3W) -15.5 Uplink noise contribution (dB(W/Hz) -63.1 internal interference contribution (dB(W/Hz) I -59.8
37、I Filterlcable line losses (dB) -1 Antenna gain (dBi) 4 E.i.r.p. (dBW) -12.5 Satellite altinide (km) 1300 Free-space loss (dB) -146.7 -143.6 Multipath loss (dB) -2 -1 Polarization mismatch loss (dB) -0.3 Receiver antenna gain (mi) 16 Received signal power (dBW) -145.5 -141.4 C/Zo internal (dB(Hz) 44
38、.3 C/NO down (dB(Hz) 48 1 52 (dB(Hz) (CWo + ZONT 41.5 42.2 (No + 10) (dB(Wmz) -187.1 -1 83.7 Implementation loss -1.5 Frequency domain adaptive filter (FDAF) loss (dB) EbI(N0 4- b) (dB) 6.2 6.9 -6 Required &/(NO + ZO) (dB) 3.7 I Margin (dB) 2.5 3.2 Long-term or short-term margin (dB) 3.2 (20%) 2.5 (
39、0.25%) bo (dB(WMz) -1 89.4 $2 (dB(WMz) -183.3 R, (chiph) 614400 I R, (dB) 57.9 Maximum interference power -128.5 -134.5 COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD-ITU-R RECMN M-1231-ENGL LI77 E 4855232 0527472 TAT 438 Rec. ITU
40、-R M.1231 NOTE 1 - Maximum interference case corresponds to narrow-band signals at 137.5 MHz: with R, = 614400 chiph. 1 P=-iR, 2 For different values of narrow-band carrier frequency the interference powers can be increased as follows: Centre frequency (MW 137.4 or 137.6 137.3 or 137.7 137.2 or 137.
41、8 137.1 or 137.9 137.05 or 137.95 137 or 138 to.9 +3.6 +9 +20 +36.7 +27.8 5 To assist in validating the results obtained by using the ITU-R methodology, two 90-day computer simulations were conducted. The orbital parameters of two example mobile-satellite constellations were used as inputs to the mo
42、del. The RF characteristics were chosen to represent spread spectrum systems that are likely to operate Co-channel with the narrow-band system. All interferers were assumed to be transmitting ail the time. These simulations calculate the C/(N+ i) ratio (dB) and the cumulative statistics for a given
43、interference scenario. The results of these simulations are shown below in Tables 4 and 5 as cumulative distributions for the subscriber and gateway receiver, respectively. Results of dynamic analysis - narrow-band modulation with FDMA TABLE 4 Cumulative distribution of CI(N+ I) ratio ia subscriber
44、receiver with two interfering constellations Per cent of time Amount of time CI(N + I) I (min) I 0.009259 I O I 7 I I 0.099537 I 117 I 8 I 1 89.148918 I 14 1- 22 I COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services439 TABLE 5 Cumulative
45、distribution of C/(iV+ I) ratio in gateway receiver with two interering constellations I I -I I Per cent of time I c(N+z) (dB1 I Amount of time (min) I 79.726082 1 4 572 I 34 I I 82.802467 I 3 987 35 i I I 85.560188 I 3 514 I 36 I 88.12577 1 I 3 325 I 37 I I I 90.622688 I 3 236 I 38 I 93.172066 I 3
46、304 I 39 I As can be seen for both the subscriber and the gateway, even under worst-case conditions when all interferers are continuously transmitting, the desired CI(N+I) of 10.3 dB for the subscriber (10.6 dB for the gateway) is not maintained for only small percentages of time (less than 1%). COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
