1、STD.ITU-R RECMN M-1232-ENGL 1997 Li855212 O527474 852 = 440 Rec. ITU-R M.1232 RECOMMENDATION ITU-R M. 1232 SHARING CRITERIA FOR SPACE-TO-EARTH LINKS OPERATING IN THE MOBILE-SATELLITE SERVICE WITH NON-GEOSTATIONARY SATELLITES IN THE 137-138- BAND (Question ITU-R 83/8) (1997) Summary In this Recommend
2、ation, the sharing criteria for downlinks of FDMA non-GSOhSS networks and SSMA non-GSO/MSS networks are recommended in terms of the maximum single-entry interference levels. The IT Radioconununication Assembly, considering a) by several systems, including those operating in other services; that freq
3、uency bands allocated to the mobile-satellite service (MSS) in the band 137-138 MHz may be shared b) criteria; that Recommendation ITU-R M.1231 specifies the interference criteria needed to determine the sharing C) that sharing criteria may be determined using the methodology described in Recommenda
4、tion IT-R SA. 1023; d) the interference criteria arrived at in Recommendation ITU-R M.1231; that Annex 1 presents the parameters used in the implementation of Recommendation ITU-R SA.1023 using e) the number of systems and revisions to frequency band allocations that are adopted by world radio confe
5、rences; that the typical deployment of interfering stations may change over a period of years as a result of growth in 0 estimated number of systems that generate interference at significant levels; that the sharing criteria derived using the methodology of Recommendation ITU-R SA.1023 is based on a
6、n g) that two general types of modulation are 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 and direct sequence spread spectrum multiple access OS-SSMA),
7、 recommends 1 that the single-entry interference levels presented in Table 1 be used as sharing criteria, or as the basis for alternative forms of sharing criteria (e.g., power flux-density limits), for the protection of stations operating in the MSS in the band 137-138 MHz; 2 stations operating in
8、the MSS in the band 137-138 MHz; that the criteria specified in recommends 1 be used as the basis for coordination thresholds for receiving 3 that the deployment of interferers specified in Annex 1 be reviewed periodically in order to determine whether the typical interference environment and conseq
9、uential sharing criteria should be revised. NOTE 1 - The sharing criteria of Table 1 (including the Notes below) are intended to be applied in frequency sharing analyses and the coordination of frequency assignments (Le as the minimum levels of accepted interference for applicable ground stations).
10、in coordination applications, the actual interference environment seen by the receiving ground station should be compared with that assumed in Annex 1 in order to help determine whether interfering signal power greater than the permissible single-entry level can be accepted. Generally, this consider
11、ation may enable acceptance of single-entry interference levels that may be as high as those specified in the applicable interference criteria (Recommendation ITU-R M.1231). COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesRec. ITU-R M.
12、1232 441 TABLE 1 Sharing entena for stations in the MSS operating in the band 137-138 MHz Frequency band (MHz) 137-1 38 (narrow-band modulation with FDMA) I 137-138 (narrow-band modulation with FDMA) 137-138 (wideband modulation with DS-SSMA) Function and type of receiving antenna Data downlink to g
13、ateway (15 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 (16 dBi antenna) Reference bandwidth is 885 kHz Interfering signal power (dBW) in the channel to be exce
14、eded for no more than 20% of the time() Space-Earth -1 46.2C3) -159.9(3) -138d3) Terrestrial -147.3 -160.6 -141.5 Interfering signal power (dBW) in the channel to be exceeded for no more than p% of the time(*) Space-Earth -133.8(3) p = 0.0625% - 1 44.7(3) p = 0.0625% -1 29) p = 0.0625% Terrestrial -
15、133.8 p = 0.125% -144.8 p=O.l25% -129.5 p=O.125% (i) The interfering signal level is determined during reception at elevation angles equal to or greater than 20. (2) The interfering signal level is determined during reception at elevation angles equal to or greater than 5“. (3) As explained in Table
16、 2, this interference power is to be applied to a single constellation of interfering satellites. Usually this number reflects the anticipated number of single interfering transmitters. However, for this Recommendation, this number reflects the number of anticipated interfering constellations. Any l
17、imits or thresholds that would apply to a single spacecraft of one of these constellations would be handled during detailed and formal coordination. NOTE 2 - The single-entry interfering signal power thresholds in Table 1 are the permissible levels of interfering signal power that fall within the sp
18、ecified reference bandwidth. Accordingly, the total power in interfering signals should be considered in frequency sharing analyses. In cases where the interfering signal bandwidth exceeds the reference bandwidth or does not fully overlap the passband of a specific receiver under study, the availabl
19、e frequency dependent rejection should be applied in conjunction with the specified permissible interference levels. Other pertinent IT-R Recommendations should be consulted for guidance on this matter. NOTE 3 -The sharing criteria presented in Table 1 are based on representative stations having the
20、 specified antenna gain values. Recommendation ITU-R SA.1022 presents a method for scaling the permissible level of total interfering signal power for other antenna gain values. The single-entry criteria also must be scaled in accordance with earth station antenna gain by the same amount of adjustme
21、nt that would occur for interference criteria using the method in Recommendation ITU-R SA. 1022. NOTE 4 - In deriving the above sharing criteria from permissible total levels of interfering signai power, no allowance has been made for interference from spurious emissions. COPYRIGHT International Tel
22、ecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD-ITU-R RECMN M*L232-ENGL 1997 q8552L2 052947b b25 442 Rec. ITU-R M.1232 NOTE 5 - Both the long-term (20% of the time) and short-term (4% of the time) sharing criteria must be met in order for interference to be
23、at or below permissible levels. NOTE 6 - Polarization isolation should also be taken into account in evaluating potential interference sources. NOTE 7 -The values presented in Table 1 are based on two example systems in Recommendations ITU-R M.1230 and IT-R M. 123 1 and may be different for other sy
24、stems. NOTE 8 -In order to show the relationship between the long and short term margins, the interference criteria, the sharing criteria and the development of the associated power levels and time percentages, Figs. 1 and2 have been prepared as an example for a narrow-band modulation with FDMA syst
25、em. (Fig. 2 is also applicable to wideband modulation with DS-SSMA). FIGURE i A power pyramid to assist in applying the methodologies contained in Recommendations ITU-R SA.1021, ITU-R SA.1022 and lTU-R SA.1023* Division of interference power levels among interferers Margin remaining from link budget
26、 / Long-term criteria Short-term margin 5.9 dB Interference criteria Permissible interference level - 155.3 dBW I The long-term Space-Earth Terrestrial interference criteria is divided 70% 30% establish interference power budgets for each interference path on a percentage basis to - 156.9 dBW - 160.
27、6 dBW Short-term criteria Long-term margin 12.6 c3 Permissible interference level - 144.5 dBW I Space-Earth Terrestrial 50% 50% - 144.6 dBW - 144.8 dBW Sharing critena: - 159.9 dBW - 160.6 dBW 2 interfering S-E systems 1 terrestrial system - 144.7 dBW - 144.8 dBW Methodology uses long-term margin fo
28、r calculating the short-term criteria and vice versa Short-term sharing criteria for space-to-Earth (or terrestrial) paths is short-term interference criteria minus the long- term interference allotted for temestrial (or space- to-Earth) systems For the calculation of permissible single-entry interf
29、erence levels see Annex i of Rec. ITU-R SA.1023 * This example uses the values calculated for the subscriber link in a reference bandwidth of 19.2 kHz for the narrow-band FDMA system COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD*
30、ITU-R RECMN M.1232-ENGL 1797 Li855212 0527477 5bL Rec. ITU-R M.1232 FIGURE 2 A power pyramid to assist in applying the methodologies contained in Recommendations ITU-R SA.1021, ITU-R SA.1022 and ITU-R SA.1023* Division of time for short-tem sharing criteria 443 Assumes the margin corresponds Availab
31、le Unavailable to this availability 99% 1% Methodology assumption User assumptions User assumptions P1 P2 Small values of P2 allow the 0.75% 0.25% system designer to retain control Inasy stem Intrasy stem and assumes small probability of enhanced interference and signal fading will be simultaneous I
32、 0.125% 0.125% 50/50 split per service Space-Earth Terrestrial Il O.625% O. 125% 2 interfering S-E systems Per system Per system 1 terrestrial system * This example uses the values calculated for the subscriber link in a reference bandwidth of 19.2 kHz for the narrow-band FDMA system. ANNEX 1 Basis
33、of sharing criteria 1 Introduction This Annex presents the parameters used in the implementation of Recommendation ITU-R SA.1023 using the interference criteria arrived at in Recommendation ITU-R M. 1231. The permissible interference levels are subdivided into space and terrestrial categories of int
34、erfering signal paths and then into the number of anticipated interferers in each category. The basis for these allotments is shown in Table 2 and a discussion of the interference environment in each band is presented below. 2 Sharing criteria The sharing criteria establishes a threshold, based on t
35、he interference criteria, on an individual interfering transmitter. The interference criteria is divided into interference powers for individual categories (e.g. space-based or terrestrial) and is then further sub-divided by the number of interferers to obtain a single-entry interference power thres
36、hold. After an assessment of potential interferers in the band of interest, the permissible level of interference (interference criteria) can be allocated to those interferers based on the service characteristics and usage of the band including geographic and time usage. For example, if a given freq
37、uency band is shared by one meteorological satellite and several mobile networks, it may be prudent to allocate 75% of the long-term interference to the meteorological-satellite service and 25% to the mobile service. A separate allocation can be made for the short-term criteria, when it is assumed t
38、hat the link is not faded. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling ServicesSTD*ITU-R RECMN M-1232-ENGL 1977 4855232 0527478 L1T8 444 Rec. ITU-R M.1232 Frequency band (MHz) 3 137-138 MHz band Equivalent number Eiquivaient number interfe
39、rers interferers Short-term Long-term Function and type apportionment apportionment of interferers of interferers of earth station between categories between categories of short-term of long-term The 137-138 MHz band is allocated to the space operation, meteorological-satellite, and space research s
40、ervices (space-to-Earth) on a primary basis. The MSS (space-to-Earth) is allocated on a primary basis in parts of the band and secondary in other parts. Fixed and mobile (except aeronautical mobile) services are allocated on a secondary basis. For most of the time at a mobile-satellite earth station
41、s, space stations could produce higher levels of interference than terrestrial stations. The gateway earth stations, with their higher gain and discrimination, can be expected to receive less interference from terrestrial stations than the mobile terminals. In the short-term, propagation enhancement
42、s on terrestrial paths and the location variability of mobile terminals may produce similar interference levels from space-to-Earth and terrestrial stations. Interfering signal path 137- 138 Data downlink to gateway (15 or 16 dBi antenna) TABLE 2 Space- Terres- Space- Terres- Space- Terres- Space- T
43、erres- Earth triai Earth trial Earth trial Earth trial path path path path path path path path 50% 50% 80% 20% 2() 1 2( ) 1 Parameters used to derive sharing criteria 137-138 to I 50% 1 50% I 70% 1 30% I 2() 1 1 I 2() 1 1 subscriber terminai (O dBi omni antenna) Usually this number reflects the anti
44、cipated number of single interfering transmitters. However, for this Recommendation, this number reflects the number of anticipated interfering constellations. Any limits or thresholds that would apply to a single spacecraft of one of these constellations would be handled during detailed and formal coordination. COPYRIGHT International Telecommunications Union/ITU RadiocommunicationsLicensed by Information Handling Services
