1、 Rec. ITU-R M.1141-2 1 RECOMMENDATION ITU-R M.1141-2*,*Sharing in the 1-3 GHz frequency range between non-geostationary space stations operating in the mobile-satellite service and stations in the fixed service (Questions ITU-R 201/8 and ITU-R 118/9) (1995-1997-2005) Scope Levels of power flux-densi
2、ty (pfd) and fractional degradation in performance are presented as thresholds for coordination of frequency assignments for non-geostationary orbit (non-GSO) space station transmitters in the mobile-satellite service MSS and receiving stations in the fixed service (FS) in frequency bands shared bet
3、ween these services in the 1-3 GHz frequency range. In the annexes, the methodology for sharing between constellations of non-GSO space station transmitters and receiving fixed stations is described and a summary of studies of frequency sharing between transmitting fixed stations and non-GSO space s
4、tation receivers is presented. The ITU Radiocommunication Assembly, considering a) that there is a need to study criteria for sharing and coordination between systems in the mobile-satellite service (MSS) and the fixed service (FS) and mobile service; b) that the bands 2 170-2 200 MHz, 2 483.5-2 500
5、 MHz and 2 500-2 535 MHz are allocated to the MSS (space-to-Earth) and fixed service (FS) on a co-primary basis; c) that the bands 1 518-1 525 MHz, 1 525-1 530 MHz and 2 160-2 170 MHz are allocated to the MSS (space-to-Earth) and FS in some regions or by some administrations, on a co-primary basis;
6、d) that for several decades, systems in the FS have been operated by many administrations in the bands newly allocated to the MSS; e) that broadcasters in many countries operate ancillary services which have both fixed and mobile characteristics in certain bands shared with the MSS; f) that the perf
7、ormance of FS systems (analogue point-to-point, digital point-to-point, digital point-to-multipoint including local access systems) needs to be considered when evaluating sharing situations in the 1-3 GHz range; g) that the performance of non-GSO MSS systems need to be considered for sharing in the
8、1-3 GHz range; h) that a specific value of pfd produced by different non-GSO MSS satellite constellations gives rise to different values of fractional degradation of performance (FDP) (Recommendation ITU-R F.1108); *This Recommendation applies only for sharing in the space-to-Earth direction. No spe
9、cific criteria have been developed for sharing in the Earth-to-space direction. *The revision of this Recommendation was jointly prepared by Radiocommunication Study Groups 8 and 9 and any future revision will also be undertaken jointly. 2 Rec. ITU-R M.1141-2 j) that multiple non-GSO MSS systems emp
10、loying code division multiple access (CDMA) techniques have been proposed to share the frequency spectrum in the space-to-Earth direction, in the 2 483.5-2 500 MHz band, on a co-frequency basis; k) that analyses performed with the methodology outlined in Recommendation ITU-R F.1108 indicate that it
11、is feasible for non-GSO MSS systems to share the spectrum with analogue radio-relay systems in the 2 483.5-2 500 MHz band (see Annex 1) and 2 160-2 200 MHz band even when using higher pfd values for coordination threshold than those in Radio Regulations (RR) No. 21.16 in the band 3 400-4 200 MHz; l)
12、 that analyses performed with the methodology outlined in Recommendation ITU-R F.1108 for currently designed digital radio-relay systems indicate that the FDP protection criteria would be exceeded in the 2 483.5-2 500 MHz band where non-GSO MSS systems use pfd values as set forth in RR No. 21.16 in
13、the band 3 400-4 200 MHz (see Annex 1); m) that the presence of interference from industrial, scientific and medical equipment and radio local area network (RLAN) transmitters in the band 2 483.5-2 500 MHz makes this band unattractive in many countries for digital radio-relay systems; n) that Recomm
14、endation ITU-R F.1246 establishes the reference bandwidth of systems in the FS to be used in specifying the coordination threshold levels, recommends 1 that the criteria expressed as FDP values for a 1 MHz reference bandwidth, presented in Table 1, should be used as coordination threshold values bet
15、ween non-GSO MSS (space-to-Earth) and digital systems in the FS, in the bands listed, except as noted in 3 (see Note 2); 2 that the criteria expressed as pfd values using reference bandwidths of 1 MHz, presented in Table 1, and 4 kHz, presented in Table 2, should be used as coordination threshold va
16、lues between non-GSO MSS (space-to-Earth) and analogue systems for telephony in the FS in the bands listed (see Note 1); for analogue systems for television in the FS, only the pfd values using the 1 MHz reference bandwidth, presented in Table 1, should apply (see Notes 1, 3, 4, 5 and 6); 3 that in
17、order to accommodate non-GSO MSS systems in the 2 483.5-2 500 MHz band, new digital point-to-point and point-to-multipoint radio-relay systems may need to be designed and operated to be compatible with the pfd values given in Table 1. Rec. ITU-R M.1141-2 3 TABLE 1 Coordination threshold values for s
18、pecific bands used for non-GSO MSS (space-to-Earth) and FS systems (pfd for analogue and FDP for digital) Frequency band (MHz) pfd per space station at angle of arrival (degrees) (dB(W/(m2 MHz) FDP (%) (See Note 2) 1 518-1525 128 for 0 = =d (9) where: P ( I x) : cdf of the interference power in the
19、telephony channel p ( I ) : either the discrete or continuous pdf. 1.4.2 Digital FS systems The calculation of the FDP described in 1.3 is equal to the first moment of the interference power normalized to the noise at the receiver input in the reference bandwidth. Thus, the FDP due to interference f
20、rom several independent constellations is the sum of the degradations produced by each. Two types of antennas are used for the digital systems: relatively high gain, circularly symmetric antennas; and, low-to-moderate gain antennas with constant gain in the azimuth plane and a directional pattern in
21、 the elevation plane. All digital line-of-sight radio-relay systems and local-access systems using sector antennas are assumed to use antennas that are circularly symmetric. The radiation pattern of this type of antenna is assumed to conform to the antenna pattern having averaged side-lobe levels as
22、 defined in Note 6 of Recommendation ITU-R F.699. 2 Results Several computer simulations using a common methodology have been performed to determine pfd values which ensure that the relevant FS interference objectives are met. This section contains the results of those simulations. Analogue FS syste
23、ms Values of pfd to protect 2 500 km analogue radio-relay routes centred at 15, 40 and 60 latitude from the emissions of non-GSO MSS systems were evaluated. Values were determined by assuming combinations of three non-GSO MSS constellations selected from four representative systems. The analyses use
24、d a base pfd value of 150 dB(W/(m2 4 kHz) for elevation angles less than 5, linearly increasing to 137 dB(W/(m2 4 kHz) at 25 and remaining at that level for elevation angles up to 90. It was shown that, except for one or two route trend lines centred in the higher latitudes, the 150/137 dB(W/(m2 4 k
25、Hz) template provided protection to analogue radio-relay systems consistent with the values contained in Recommendation ITU-R SF.357. Rec. ITU-R M.1141-2 9 It was assumed that the four non-GSO systems used CDMA techniques and that they were all designed such that they could share on a co-frequency,
26、co-coverage basis. Digital FS systems For multiple non-GSO MSS systems interfering, with a digital point-to-point station employing a high-gain receiving antenna, it was shown that the pfd template needed to realize an average FDP on the order of 10% with peaks not much greater than 15% to 20% was 1
27、62 dB(W/(m2 4 kHz) in the 0-5 range of elevation angle, linearly escalating to 149 dB(W/(m2 4 kHz) at 25 elevation angle and remaining at that value up to 90 of elevation angle. At values of pfd sufficient to protect the operation of analogue point-to-point radio-relay systems, i.e., 150 dB(W/(m2 4
28、kHz) escalating to 137 dB(W/(m2 4 kHz), digital point-to-point radio-relay stations would experience an average FDP on the order of 160%, with peaks to 240% and 320% and troughs as low as 80% depending on the latitude of the station. An FDP of 160% is equivalent to a decrease in fade margin of about
29、 4 dB. 2.1 Trends Several trends arising from the results can be observed. The received interference can vary rapidly with the FS pointing azimuth for some non-GSO constellations. Constellations with polar or near polar orbits also impact various FS pointing azimuths differently, but the effect is m
30、uch less pronounced. FS stations at higher latitudes generally experience more interference over time than FS stations located at lower latitudes. This is more true for constellations with polar orbits, however actual operational requirements may include turning off outer beams due to coverage overl
31、ap and hence the interference effect will be reduced. Satellite constellations operating at lower altitudes require different pfd masks to protect the FS than those constellations operating at higher altitudes. As a first order estimate, the levels of interference over time decrease inversely with t
32、he square of the operating frequency. 2.2 Conclusions The selection of a single pfd mask which ensures protection of the FS and which does not simultaneously penalize other non-GSO constellations, is difficult. Selection of a particular pfd mask based on one constellation can result in inadequate pr
33、otection to the FS, as another constellation which could meet those pfd levels could still exceed the FS interference objectives. In other words, two different non-GSO constellations can operate with different pfd masks which both protect the FS equally. The above does not hold true for a pfd mask d
34、erived from several non-GSO constellations which have been designed to share on a co-frequency, co-coverage basis and which use CDMA techniques. The pfd required to protect 2 500 km hypothetical reference circuit (HRC) analogue FS systems from the simultaneous emissions of three non-GSO MSS constell
35、ations was found to be 150 dB(W/(m2 4 kHz) at elevation angles between 0 and 5, linearly escalating to 137 dB(W/(m2 4 kHz) at an elevation angle of 25. The pfd remained constant at this value for elevation angles above 25. Interference to the HRC was consistent with the values given in Recommendatio
36、n ITU-R SF.357. The pfd required to ensure that the FDP as defined in Recommendation ITU-R F.1108, of digital FS systems, did not exceed about 10% was found to be some 9 dB to 10 dB more stringent than the 10 Rec. ITU-R M.1141-2 values of pfd required to protect the performance of analogue FS system
37、s. These lower values, if adopted, will inhibit the introduction of viable non-GSO MSS systems. It was concluded that sharing with these systems would be most readily accomplished by establishing pfd values that, while resulting in an FDP in excess of 10%, for example, would not unduly penalize the
38、design and operation of either FS or non-GSO MSS systems in the 2 483.5-2 500 MHz band. Annex 2 Sharing of frequency bands in the 1-3 GHz range between transmitting stations in the FS and non-GSO space stations operating in the MSS (Earth-to-space) 1 Introduction Studies were required for the sharin
39、g scenario between transmitting stations in the FS and non-GSO MSS space station receivers in the MSS Earth-to-space frequency bands between 1-3 GHz, i.e. 1 610-1 626.5 MHz, 1 668-1 675 MHz, 1 970-2 010 MHz and 2 655-2 690 MHz. However, the sharing studies were limited to the 1 610-1 626.5 MHz and 1
40、 970-2 010 MHz bands, since these bands are of immediate interest for the implementation of non-GSO MSS systems. No inputs were received for the other bands. A study on the specific sharing scenario of FS troposcatter links with non-GSO systems was also considered. In addition to the sharing studies
41、, the possible regulatory options for FS systems are discussed. Sharing studies have shown that co-channel operation of the transmitting stations of the new FS and receivers of non-GSO MSS space stations in the 1 980-2 010 MHz band would not in general be possible. Sharing studies in the 1 610-1 626
42、.5 MHz band (see RR No. 5.359) found that the loss of traffic capacity may be acceptable in the case of very low FS density (e.g. one in 230 000 km2). One option to improve the sharing conditions would be to reduce considerably the permissible e.i.r.p. limits in RR Article 21 for FS transmitters. An
43、y such limits are highly dependent on the assumptions regarding new FS transmitter density and would be based on the assumption of a high FS density. This would lead to extremely stringent limits on new FS stations which may not be practical for their operation. In view of the above, no specific cri
44、teria to facilitate sharing from a technical viewpoint have been developed. 2 Simulation of interference from FS links into MSS satellite receiver 2.1 Point-to-point FS links Studies on the interference from typical multiple FS transmitters (circa 6 000 worldwide) into non-GSO/MSS (medium-Earth orbi
45、t) space station receivers in the band 1 980-2 010 MHz found that unacceptable interference to non-GSO/MSS space station receivers would occur. The assumed target equivalent interference C / I criterion was not met for close to 100% of the time. Based on this Rec. ITU-R M.1141-2 11 study, it can be
46、concluded that co-channel sharing of MSS uplinks to non-GSO MSS satellites in frequency band segments in the 1 980-2 010 MHz band, which are or remain heavily used by, the FS would not be possible. It is noted that a preliminary assessment based on interpolations of actual FS utilization data in a n
47、umber of countries has indicated that the number of point to point FS transmitters could be greater than that assumed in the above study and would only further increase the level of interference. Further studies on the interference from typical multiple FS transmitters (between 700 and 3 000 worldwi
48、de) into non-GSO/MSS (low-Earth orbit) space station receivers in the band 1 610-1 626.5 MHz found that the loss of traffic capacity may be acceptable only in the case of very low FS density (e.g. one in 230 000 km2). 2.2 Troposcatter FS links In the case of sharing between FS troposcatter systems a
49、nd the non-GSO MSS (medium-Earth orbit) system, one study showed that co-channel sharing would not be feasible. In the main beam of a troposcatter transmitter operating at its maximum output power, the MSS satellite receiver could experience interference levels of up to 60 dB higher than is tolerable. In the side lobe region tolerable interference levels are still exceeded. Thus it would be necessary to phase out these systems if the non-GSO MSS is to be implemented in portions of the bands where troposcatter systems operate. 3 Conc
