1、RECOMMENDATION ITU-R SA.1273* POWER FLUX-DENSITY LEVELS FROM THE SPACE RESEARCH, SPACE OPERATION AND EARTH EXPLORATION-SATELLITE SERVICES AT THE SURFACE OF THE EARTH REQUIRED TO PROTECT THE FIXED SERVICE IN THE BANDS 2 025-2 110 MHz AND 2 200-2 290 MHz (Questions ITU-R 11 8/7 and IT-R i 1319) (1997)
2、 The IT Radiocommunication Assembly, considering I l a service (EESS) and the fixed service (FS) share the bands 2 025-2 110 MHz and 2 200-2 290 MHz; b) that the FS operates and plans to operate a variety of point-to-point and point-to-multipoint (P-MP) systems employing analogue and digital techniq
3、ues in these bands; c) that, because of such sharing, it is necessary to ensure that emissions from satellites do not cause unacceptable interference to FS systems; d) that FS systems can be satisfactorily protected from the emissions from satellites by placing suitable limits on the power flux-dens
4、ity (pfd) produced at the surface of the Earth, in a reference bandwidth; e) that, nevertheless, any limitations of the pfd produced at the surface of the Earth should not be such as to place undue restrictions on the design of systems in the SRS, SOS and EESS services; f) that the performance degra
5、dation for a fixed service system depends on the sum of the degradations due to emissions from all space stations that are visible to it; g) that the band 2025-2 110 MHz is used for Earth-to-space links for both low-Earth orbiting (LEO) and geostationary satellite orbit (GSO) spacecraft; the band is
6、 also used for space-to-space links, typically for radiocom- munications from data relay satellite (DRS) spacecraft to LEO spacecraft; h) that the band 2 200-2 290 MHz is used for space-to-Earth links for both LEO and GSO spacecraft; this band is also used for space-to-space links, typically for rad
7、iocommunications from LEO spacecraft to DRS spacecraft; j) that for systems in the SRS, SOS and EESS, techniques are employed to reduce the radio-frequency spectral power density of satellite emissions, that systems in the space research service (SRS), space operation service (SOS) and Earth explora
8、tion-satellite I recommends that in the band 2 200-2 290 MHz the maximum pfd produced at the surface of the Earth by emissions from a 1 space station operating in the space-to-Earth direction, for all conditions and methods of modulation, should not exceed: - - -130 dB(W/m2) in any 1 MHz for angles
9、of arrival less than 5“ above the horizontal plane; -130 + 0.5 (6-5) dB(W/m2) in any 1 MHz for angles of arrival 6 (degrees) between 5“ and 25“ above the horizontal plane; -120 dB(W/m2) in any 1 MHz for angles of arrival between 25“ and 90“ above the horizontal plane; - * This Recommendation was joi
10、ntly developed by Radiocommunication Study Groups 7 and 9, and future revisions should be undertaken jointly. Rec. ITU-R SA.1273 113 2 that in the band 2200-2290 MHz the maximum pfd produced at the surface of the Earth by emissions from a space station in LEO operating in the space-to-space directio
11、n, for all conditions and methods of modulation, should not exceed: - - -127 dB(W/m2) in any 1 MHz for angles of arrival less than 5“ above the horizontal plane; -127 + 0.5 (6-5) dB(W/m2) in any 1 MHz for angles of arrivai 6 (degrees) between 5“ and 25 above the horizontal plane; -1 17 dB(W/m2) in a
12、ny 1 MHz for angles of arrival between 25“ and 90“ above the horizontal plane; - 3 DRS in GSO, for all conditions and methods of modulation, should not exceed: - - that in the band 2025-2 110 MHz the maximum pfd produced at the surface of the Earth by emissions from a -130 dB(W/m2) in any 1 MHz for
13、angles of arrival less than 5“ above the horizontal plane; -130 + 0.5 (6-5) dB(W/m2) in any 1 MHz for angles of arrival 6 (degrees) between 5“ and 25“ above the horizontal plane; -120 dB(W/m2) in any 1 MHz for angles of arrivai between 25“ and 90“ above the horizontal plane; - 3.1 for not more than
14、5% of the time to compensate for background interference; that the value of -130 dB(W/m2) in any 1 MHz may need to be exceeded in rare occasions by up to 6 dB but 4 propagation conditions; that the above limits relate to the pfd and angles of arrivai which would be obtained under free-space 5 NOTE 1
15、 - In deriving 9 2 of recommends, it has been determined that space-to-space transmissions of the space radiocommunication services control the sharing environment with the FS. that Annex 1 should be referred to for additional guidance relating to this Recommendation. ANNEX 1 Interference considerat
16、ions from the SRS, SOS and EESS into the FS in the bands 2 025-2 110 MHz and 2 200-2 290 MHz 1 Introduction This Annex provides additional consideration in support of the pfd values given in 1, 2 and 3 of recommends. The values presented in this Annex have been derived either from a calculation of t
17、he effects of continuous interference from the emissions of geostationary DRS or from Monte Carlo simulations of the effect of emissions from geostationary DRS satellites and LEO satellites on FS stations using the principles of Recommendations IT-R F.1107 and -R F.1108. Orbital locations for DRS sa
18、tellites were obtained from Recommendation ITU-R SA. 1275; FS system parameters were obtained from Recommendations IT-R M.1143 and IT-R F.759, and the orbital characteristics of the LEO satellite space science services satellites were derived from the Report of the Space Science Services Steering Gr
19、oup (Annex 4 to Document 7B/26-9D/54 dated 16 November 1994). Paragraph 2 summarizes the results applicable to the emissions of GSO satellites in the band 2200-2290 MHz. Paragraph 3 summarizes the results applicable to the emissions of LEO satellites in the band 2 200-2 290 MHz, and 4 applies to the
20、 emissions of DRS satellites in the band 2 025-2 1 i O MHz. Each paragraph contains its own conclusion that supports the value of pfd in the associated recommends. STD-ITU-R RECMN SA-LZ73-ENGL 1997 m 9855212 0531980 72b - STD-ITU-R RECMN SA.1273-ENGL 1997 4855212 0531481 662 W 114 Rec. ITU-R SA.1273
21、 Power density into antenna (dB(W/Hz) Transmit gain (dBi) Receive gain (dBi) Antenna pattern 2 Pfd levels applicable to geostationary satellite emissions in the band 2 200-2 290 MHz DRS LEO -57.7 -83.5() 34.7 28.5 36.0 28.5 Recommendation IT-R S.672 (-20 dB sidelobe) Recommendation IT-R S.672 (-20 d
22、B sidelobe) A number of GSO satellites operating in the ground network of the space science services use the band 2 200-2 290 MHz (space-to-Earth) for tracking, telemetry and command verification (TTC) either on an operational or on a contingency basis. Scientific satellites tend to use the band ope
23、rationally, whereas if the band is used by application satellites, such as fixed-, broadcasting-, or mobile-satellites, it tends to be on a contingency basis. Data gathered on a number of such GSO satellites have indicated that their numbers vary over a ten year span to the year 2005 between 87 and
24、117. At a particular orbit location there will only be a few assignments and there will be significant spans of the GSO orbit where there are no assignments existing or planned. The e.i.r.p. of 96% of existing GSO satellite assignments is less than +10dBW, resulting in a total pfd of less than -153
25、dB(W/m2) on the surface of the Earth. Taking into account the necessary bandwidths of the GSO satellites, with the exception of only a few assignments, the e.i.r.p. density of the GSO satellite transmissions is less than -10 dB(W/4 kHz), resulting in a pfd on the surface of the Earth of less than -1
26、73 dB(W/m2) in any 4 kHz (-149 dB(W/m2) in any 1 MHz) for all angles of arrival. Based on this data, it may be concluded that emissions from GSO satellites in the band 2200-2290 MHz are not significant sources of potential interference to the FS. To ensure that sufficient flexibility is afforded DRS
27、 applications in future while also protecting the FS, a pfd level equivalent to -154/-144 dB(W/(m2 .4 kHz) as identified in the Radio Regulations No. S21.16, Table S21-4 for the band 2 200-2 300 MHz (Mask A) and referenced to 1 MHz will be adequate for sharing of this band. 3 Pfd levels applicable t
28、o LEO satellite emissions in the band 2 200-2 290 MHz 3.1 Simulation studies considered the downlink interference from 24 DRS-LEO combinations, where each DRS was treated as transmitting/receiving simultaneously to/from two LEOS (while they were visible). All DRS-LEO combinations were considered as
29、operating together and Co-channel. The transmission parameters used for the modelling are summarized in Table 1. TABLE 1 Satellite transmission parameters used for the modelling The interference was simulated into a variety of fixed systems. As the only element of the receive system that will alter
30、the value of received interference is the antenna, it was necessary only to model interference into each antenna type, rather than each system type. Consequently interference was modelled only into system types DH (digital high capacity), DL (digital low capacity), MLCS (digital point-to-multipoint
31、central station), MLOS (digital point-to-multipoint out station) and T (analogue or digital tropospheric), representing 33 dBi dish, Yagi, omnidirectional, flat-plate and 45 dBi dish antennas, respectively. Interference was calculated at each of 60 locations (at 20“ and 50“ North, and at 30“ longitu
32、de increments) and for 8 FS antenna azimuths at each location. For the results presented, the two worst-case results were then selected for each system type (excluding those locations far from land). Rec. ITU-R SA.1273 115 2- Figure 1 shows that the Yagi antenna (DL system) experiences the most seve
33、re interference at approximately -184 dB(W/4 kHz) for 20% of the time. This is, however, well within the long-term performance objective (20%) for most fixed link systems, i.e., around -170 dB(W/4 kHz). This protection level corresponds to a degradation in FS receiver threshold of approximately 1 dB
34、 (see Recommendation ITU-R F.759). I r y I l I j, i, - - FIGURE 1 Interference from LEO into various FS systems h v 10-2 i 5: , - l I .% 1 -.-. 2 1 I l 1 o- O 15 30 45 60 75 90 105 120 135 150 165 180 FS Azimuth (degrees) Lowihigh angle pfd = - 152/ - 142 dB(W/(rn2 . 4 kHz) at 5“/25“ angles of arriv
35、al 127344 Rec. ITU-R SA.1273 119 FIGURE 5 FDP as a function of azimuth angle for a digital radio-relay station located at 50 N, antenna elevation = OS0 from 8 satellites at 800 krn altitude and 98“ orbit inclination FS Azimuth (degrees) Low/high angle pfd = - 1521- 142 dB(W/(m2 . 4 kHz) at 5“/25“ an
36、gles of arrivai 1273-05 FIGURE 6 FDP as a function of azimuth angle for a digital radio-relay station located at 20 N, antenna elevation = 0.5 from 6 satellites at 333 km altitude and 28.5O orbit inclination FS Azimuth (degrees) Lowhigh angle pfd = - 150/- 140 dB(W/(m2 . 4 kHz) at 5“/25“ angles of a
37、rrival 1273-06 STDmITU-R RECMN SA-1273-ENGL 1997 m 4855212 053148b 144 m 120 Rec. ITU-R SA.1273 a FIGURE 7 FDP as a function of azimuth angle for a digital radiu-relay station located at 50 N, antenna elevation = 0.5O from 6 satellites at 333 km altitude and 28.5O orbit inclination id 5 2 10 5 2 1 L
38、owhigh angle pfd = - 1501- 140 dB(W/(m2 .4 kHz) at 5“/25“ angles of arrivai 1273-07 3.5 Conclusions related to the band 2 200-2 290 MHz Studies of bandsharing between space stations in LEO and FS stations in the band 2 200-2 290 MHz have demonstrated that pfd levels significantly greater than Mask A
39、 will produce unacceptable performance conditions for the FS. For example, at pfd increases of 4 dB or greater than Mask A, the FS performance degradations approach 25% for large portions of available FS azimuths. However, at modest pfd increases up to about 3 dB, the performance degradations should
40、 be acceptable. Although marginally exceeding the FS bandsharing objectives, these levels in practice should be acceptable since a number of ameliorating elements may be present such as relative channel bandwidths, channel occupancy, and satellite transmission activity factors. In addition, since th
41、e majority of new FS stations will be digital, a 1 MHz reference bandwidth will be acceptable to protect the FS. A pfd level (converted to 1 MHz) ranging from -127 dB(W/(m2 . MHz) at elevation angles less than 5 to -1 17 dB(W/(m2 . MHz) for elevation angles greater than 25 should provide the necessa
42、ry protection to the FS while allowing operational flexibility for existing and planned LEO satellites. 4 Pfd levels applicable to GSO DRS emissions in the band 2 025-2 110 MHz 4.1 In the same analysis that was performed under $ 3.1, interference was also simulated from the DRS constellation. in ter
43、ms of the various interference reduction factors, account was taken of three factors, namely, FS channelization, FS DRS position avoidance (see Note i), and improved FS antenna performance. Figure 8 shows the expected interference from this simulation. NOTE 1 - The orientation of FS stations was all
44、ocated randomly. An inspection of their .pointing showed that none of the stations were directed within 1.5“ of any of the DRS GSO orbital locations. Rec. ITU-R SA.1273 121 FIGURE 8 Interference from DRS into various FS systems ! I l I I I I l I 2 1 o4 -210 -200 -190 -180 -170 -160 -150 (dB(W/4 kHz)
45、 127348 The levels can be seen to lie slightly below or near the -170 dB(W/4 Hz) level for 20% of the time in all cases except that of the Yagi (DL), which exceeds the limit by some 5 dB. Long-term interference levels into the tropospheric antenna are again low, at some 7 dB below the limit, while t
46、he low gain and zenith-pointing null of the omnidirectional antenna ensure even lower interference levels. 4.2 A study was also performed to determine the aggregate interference from all visible DRS satellites into a FS receiver located at 60“ N latitude. The DRS space stations were assumed to trans
47、mit with a pfd Mask A. Orbital positions of the DRS were taken from Recommendation ITU-R SA.1275. FS parameters were taken from Recommen- dation ITU-R M. 1143. The FS antenna radiation pattern employed Note 6 of Recommendation ITU-R F.699. A typical antenna size of 1.8 m was used instead of a 33 dBi
48、 antenna. As DRS systems employ circular polarization, a 3 dB polarization discrimination was used in the calculation of main beam interference. A 2 dB feeder loss for the FS station was also employed. The FS station antenna was positioned at 25“ E longitude and 60“ N latitude and rotated in 5“ step
49、s between 80“ and 280“ azimuth directions. Results indicated that to ensure that an interference level of -170 dB(W/4 kHz) is not exceeded, 81% of available azimuth directions would need to be avoided by the FS. However, this assumed that ali visible DRS space stations were transmitting continuously. Recognizing that this will not be the case for many DRS applications with respect to a given FS station, a further analysis has shown that if one space station was active for a significant time period and ail other DRS space stations active for much sho
