1、 Rec. ITU-R S.1526-1 1 RECOMMENDATION ITU-R S.1526-1 Methodology to assess the interference environment in relation to Nos. 9.12, 9.12A and 9.13 of the Radio Regulations when non-geostationary-satellite orbit fixed-satellite service systems are involved*(Question ITU-R 231/4) (2001-2002) The ITU Rad
2、iocommunication Assembly, considering a) that some non-geostationary-satellite orbit fixed-satellite service (non-GSO FSS) systems are at the early stage of development and as a result some modifications to their design are likely; b) that changes to one non-GSO FSS system may affect other operation
3、al or planned FSS systems; c) that other operational or planned FSS systems affected by changes to a non-GSO FSS system must retain the flexibility to operate within the limits of their notifications; d) that Recommendation ITU-R S.1431 describes several mitigation techniques to enhance sharing betw
4、een non-GSO FSS systems; e) that it is desirable for the designers of non-GSO FSS systems to have metrics that permit an assessment of the impact of these various mitigation techniques on the system design; f) that it is common for administrations coordinating their FSS systems to change system para
5、meters of their filed system as a result of their coordination efforts; g) that provision No. 11.43B of the Radio Regulations (RR) and the associated Rules of Procedure allow for changes in the system characteristics of recorded frequency assignments, including those of non-GSO FSS systems, while re
6、taining the original date of entry in the Master Register, as long as the changes do not increase the probability of harmful interference to assignments already recorded; h) that resolves 2 of Resolution 132 (WRC-97) states that in the bands 18.8-19.3 GHz and 28.6-29.1 GHz for non-GSO FSS systems no
7、tified before 18 November 1995 when coordination was not required (before that date) no coordination is required when the characteristics of the modified frequency assignment are within the limits of those of the original notification; _ *Further study is required concerning the applicability of thi
8、s Recommendation to non-GSO FSS sharing with GSO FSS (RR Nos. 9.12A/9.13) in the bands 19.3-19.7 GHz and 29.1-29.5 GHz. 2 Rec. ITU-R S.1526-1 j) that, in the bands in considering h), RR Nos. 9.12, 9.12A and 9.13 apply; k) that, in some other bands non-GSO FSS, epfdand epfdlimits have been adopted in
9、 RR Article 22 to limit the interference into GSO FSS and BSS systems, and RR No. 9.12 applies between non-GSO FSS systems; l) that, in the sharing situations in considering j), Recommendation ITU-R S.1323 provides the maximum permissible levels of interference in an FSS satellite network; m) that i
10、t is desirable to have a methodology in the ITU-R to determine whether modifications to the characteristics of a non-GSO FSS system will improve the sharing situation with another FSS system or will worsen this situation, recommends 1 that the methodology in Annex 1 can be used to assist non-GSO FSS
11、 system designers in the evaluation of the impact of various mitigation techniques; 2 that the methodology in Annex 1 may be used (by administrations and system designers) as a way to determine whether a modification introduced to the design of a non-GSO FSS system will improve or worsen the interfe
12、rence environment with respect to another FSS system sharing the same frequency band. ANNEX 1 Methodology to assess the interference environment generated by a non-GSO FSS system 1 Introduction A procedure is proposed here for the assessment of how modifications introduced to a non-GSO FSS system (S
13、ystem A) affect the interference environment created by this system with respect to another FSS system (System B). It is recognized that the affected system has a wide degree of operational freedom within the filed parameters of the system, taking into account constraints imposed by previously filed
14、 systems. To draw general conclusions about changes to a system, the procedure below would be applied separately using all available transmission parameters for the two systems. In addition, both systems may employ mitigation strategies involving a variety of mitigation techniques in various combina
15、tions in order to deal with each of the four interference scenarios. Possible mitigation strategies for consideration include: avoidance leading to loss of service during in-line events, satellite diversity, earth station site diversity, satellite selection strategies, frequency channelization, link
16、 balancing, alternate polarization, and improved antenna characteristics. The procedure can be summarized by the following steps: Step 1: Determine the mitigation strategies (e.g. avoidance angle values) to be used by the given systems to protect all relevant scenarios of interference to System A (w
17、ith its parameters prior to the modification). Rec. ITU-R S.1526-1 3 Step 2: Calculate relevant performance statistics (e.g. visibility, satellite handoffs, satellite track time, availability, etc.) throughout the service area of System B, employing the mitigation strategies determined in Step 1. St
18、ep 3: Repeat Steps 1 and 2, substituting the new system parameters for System A. Step 4: Compare the performance statistics of System B before and after the change to System A. Step 5: If all statistics have improved, conclude that the design change in System A has made sharing easier for System B.
19、Step 6: If all statistics have worsened, conclude that the design change in System A has made sharing more difficult for System B. Step 7: If some statistics have improved and some have worsened, no immediate conclusions about the sharing situation can be made. Consideration may be given to addition
20、al factors affecting the distribution of the interference variations for the various earth station locations of System B, such as weighted averaging. However, it would ultimately be necessary for the parties involved (i.e. the operators of Systems A and B), in any resultant coordination agreement, t
21、o agree on the details of the approach to be used, specifically, the calculation/simulation assumptions used in the analysis and the application of any weighted averaging technique. The four interference scenarios referred to above are described in Fig. 1. The angle Trepresents the transmit discrimi
22、nation angle (i.e. the angle off-boresight between the transmitters signal path and the interference path), and the angle Rrepresents the receive discrimination angle. Examples of the application of the methodology, including statistics characterizing visibility, satellite handoffs, satellite track
23、time and availability are described in 2 and 3. More details on how visibility statistics can be weighted by population or GDP can also be obtained from these examples. The impact of modifications introduced to a non-GSO FSS system on the sharing with another non-GSO FSS system assumed to be using s
24、atellite diversity is considered in 2. The impact of these modifications on the sharing with a GSO FSS system is addressed in 3. 4 Rec. ITU-R S.1526-1 1526-01TRTRTRTRSystem BSystem B System ASystem ACase 1System BSystem B System ASystem ACase 2System BSystem B System ASystem ACase 3System BSystem B
25、System ASystem ACase 4FIGURE 1Four interference scenariosNOTE 1 Dotted lines indicate interference paths. Solid lines indicate wanted signal paths. 2 Example for the sharing between non-GSO FSS systems: Impact of modifications to LEOSAT-1 on USAMEO-1 The following illustrates through a particular ex
26、ample an application of the methodology in a situation where USAMEO-1 is assumed to mitigate using satellite diversity and both systems have chosen to use Recommendation ITU-R S.1323 to determine the avoidance angles. The performance statistics considered here are visibility, satellite handoffs, and
27、 satellite track time. Other performance statistics could also be considered. Other examples may include the case where the mitigating non-GSO FSS system does not employ satellite diversity and suffers loss of service during in-line events. In that case the performance statistics relating to the los
28、s of service can be calculated as illustrated in 3.3. Rec. ITU-R S.1526-1 5 2.1 LEOSAT-1 system parameters and assumptions The basic modelling characteristics for LEOSAT-1 are summarized in Table 1a. TABLE 1a LEOSAT-1 system characteristics Characteristic LEOSAT-1 Constellation parameters Number of
29、satellites 288 Number of planes 12 Number of satellites per plane 24 Plane spacing (degrees) 15.36 Walker phase factor Not available Inclination (degrees) 84.7 Orbit altitude (km) 1 375 Inter-plane phasing (degrees) Random Elevation mask angle (degrees) 40 Uplink transmission parameters Access metho
30、d MF/TDMA Carrier bandwidth (MHz) 3.096 Power control Yes Power control value (dB) 13.5 Earth station transmit peak gain (dB) 35.2 Earth station transmit antenna pattern RR Appendix 8 Earth station transmit antenna diameter (m) 0.3 Satellite receive peak gain (dB) 33.2 Satellite receive antenna patt
31、ern 3 EoC, 25 near side lobe 30 far side lobe Receive beam adapted for constant cell size? Yes Noise temperature (K) 832 Number of receive beams 364/polarization Downlink transmission parameters Access method ATDMA Carrier bandwidth (MHz) 500 Power control No Earth station receive peak gain (dB) 34.
32、1 Earth station receive antenna pattern RR Appendix 8 6 Rec. ITU-R S.1526-1 TABLE 1a (end) Table 1b shows the basic system parameters for two hypothetical variations of the LEOSAT-1 system, designated as LEO-XX and LEO-YY. These modifications each contain less than half the number of satellites of t
33、he LEOSAT-1 system. This reduction in the number of satellites is accomplished in LEO-XX by maintaining the minimum elevation angle and near-polar configuration, while raising the altitude to 2 500 km. The decrease in the number of satellites is accomplished in LEO-YY by maintaining the altitude whi
34、le decreasing the elevation mask angle to 25 and changing to a Walker Delta orbit configuration. TABLE 1b LEO-XX and LEO-YY system characteristics Characteristic LEOSAT-1 Downlink transmission parameters (cont.) Earth station receive antenna diameter (m) 0.3 Satellite transmit peak gain (dB) 34.7 to
35、 35.7 Satellite transmit antenna pattern 0.5 EoC, 25 near side lobe 30 far side lobe Satellite transmit e.i.r.p. at EoC (dB) 53.9 Transmit beam adapted for constant cell size? Yes Noise temperature (K) 288 Number of transmit beams 16 ATDMA: adaptive TDMA e.i.r.p.: equivalent isotropically radiated p
36、ower EoC: edge of coverage TDMA: time division multiple access Characteristic LEO-XX LEO-YY Constellation parameters Number of satellites 128 120 Number of planes 8 10 Number of satellites per plane 16 12 Plane spacing (degrees) 23 36 Walker phase factor Not available 1 Inclination (degrees) 84.7 58
37、 Orbit altitude (km) 2 500 1 375 Inter-plane phasing (degrees) Random 3 Elevation mask angle (degrees) 40 25 Uplink transmission parameters Access method MF/TDMA FDMA/TDMA Carrier bandwidth (MHz) 3.1 3.1 Rec. ITU-R S.1526-1 7 TABLE 1b (end) Characteristic LEO-XX LEO-YY Uplink transmission parameters
38、 (cont.) Power control Yes Yes Power control value (dB) 13.5 13.5 Earth station transmit peak gain (dB) 39.4 39.4 Earth station transmit antenna pattern RR Appendix 8 RR Appendix 8 Earth station transmit antenna diameter (m) 0.4 0.4 Satellite receive peak gain (dB) 37.1 with adjusts for free space l
39、oss and scan loss 36.0 with adjusts for free space loss and scan loss Satellite receive antenna pattern Rec. ITU-R S.672, L= 25 dB, Beamwidth = 2 Rec. ITU-R S.672, LN= 25 dB, Beamwidth = 2.3 Receive beam adapted for constant cell size? No No Noise temperature (K) 832 832 Number of receive beams 364/
40、polarization 364/polarization Downlink transmission parameters Access method ATDMA ATDMA Carrier bandwidth (MHz) 500 500 Power control No No Earth station receive peak gain (dB) 36.6 36.6 Earth station receive antenna pattern RR Appendix 8 RR Appendix 8 Earth station receive antenna diameter (m) 0.4
41、 0.4 Satellite transmit peak gain (dB) 37.2 with adjusts for free space loss and scan loss 36.1 with adjusts for free space loss and scan loss Satellite transmit antenna pattern Rec. ITU-R S.672, LN= 25 dB, Beamwidth = 2 Rec. ITU-R S.672, LN= 25 dB, Beamwidth = 2.3 Satellite transmit e.i.r.p. at EoC
42、 (dB) 57.7 54.6 Transmit beam adapted for constant cell size? No No Noise temperature (K) 288 288 Number of transmit beams 16 16 FDMA: frequency division multiple access 8 Rec. ITU-R S.1526-1 2.2 USAMEO-1 system parameters and assumptions 2.2.1 Basic characteristics In this example, a particular lin
43、k from USAMEO-1 has been selected for analysis. Its basic modelling characteristics are summarized in Table 2. TABLE 2 USAMEO-1 system characteristics Constellation parameters Number of satellites 32 Number of planes (for each of 2 subconstellations) 4 ( 2 subconstellations) Number of satellites per
44、 plane 4 Plane spacing (degrees) 90 Walker phase factor 3 Inclination (degrees) 50 Orbit altitude (km) 10 352 Inter-plane phasing (degrees) 67.5 Delta phase between subconstellations (degrees) 30 Delta ascending node between subconstellations (degrees) 0 Elevation mask angle (degrees) 20 Uplink tran
45、smission parameters Access method TDMA/FDMA Carrier bandwidth (MHz) 0.562 Power control Yes Power control value (dB) 20.7 Earth station transmit peak gain (dB) 44.16 Earth station transmit antenna pattern Rec. ITU-R S.465 Earth station transmit antenna diameter (m) 0.65 Satellite receive peak gain (
46、dB) 37.48 Satellite receive antenna pattern Rec. ITU-R S.672, Beamwidth = 2.3, LN= 25 dB Receive beam adapted for constant cell size? No Noise temperature (K) 577.98 Number of receive beams 20 Downlink transmission parameters Access method TDM/FDM Carrier bandwidth (MHz) 96.162 Power control No Eart
47、h station receive peak gain (dB) 40.78 Rec. ITU-R S.1526-1 9 TABLE 2 (end) 2.2.2 Frequency usage The USAMEO-1 system proposes to use 1 GHz of spectrum in the bands 28.6-29.1 GHz and 29.5-30.0 GHz for the uplink, and 1 GHz of spectrum in the bands 18.8-19.3 GHz and 19.7-20.2 GHz for the downlink. The
48、 frequency bands are divided into 125 MHz channels. It is assumed that multiple channels, to cover the 500 MHz overlapping with LEOSAT-1 (XX, YY) spectrum, can be assigned to the same spot beam for worst-case peaking conditions. 2.2.3 Satellite antenna and earth station model The satellite uses fixe
49、d transmit and receive spot beams. The antennas and beams are maintained in a fixed orientation relative to the spacecraft to allow the beams to move across the surface of the Earth as the satellite moves. Even though the beams are fixed relative to the satellite, the simulation uses tracking beams with each earth station, so that the worst potential interference is caught. The satellite antenna is modelled using Recommendation ITU-R S.672, with a half power beamwidth of 2.3 and side lobe level of 25 dB. Twenty user stations ar
