Rec. Itu-r s. 1430

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Rec. ITU-R S.1430



(Questions ITU-R 253/4, ITU-R 231/4 and ITU-R 212/1)


Rec. ITU-R S.1430

The ITU Radiocommunication Assembly,


a) that some frequency bands are allocated to the FSS for use by non-GSO systems in both the Earth-to-space and the space-to-Earth direction of transmission;

b) that these frequency bands are also available for use by GSO systems;

c) that, therefore, there is a possibility of mutual interference between earth stations operating to space stations in both GSO and non-GSO orbits;

d) that such potential interference may be alleviated or avoided through the coordination of such earth stations;

e) that it is desirable to limit the number of coordinations that may have to be undertaken;

f) that it is possible to define an area around a transmitting earth station outside of which a receiving earth station would be subject to only negligible interference;

g) that Radiocommunication Study Group 1 is drawing together the results of studies from all concerned Study Groups in the development of comprehensive texts that may be used to revise RR Appendix S7;

h) that Recommendation ITU-R P.620 contains a propagation model that is intended for coordination of earth stations,


1 that, in frequency bands allocated to the FSS in both the space-to-Earth and the Earth-to-space direction of transmission and utilized by both non-GSO and GSO FSS systems, a bidirectional coordination area be determined for each transmitting earth station;

2 that, for that purpose, Annex 1 to this Recommendation should be used.

Determination of the coordination area for earth stations operating with non-GSO
space stations with respect to earth stations operating in the reverse direction
in frequency bands allocated bidirectionally to the FSS

1 Introduction

This procedure has been developed for the determination of the bidirectional coordination area around an earth station operating with a non-GSO space station in frequency bands used bidirectionally by earth stations operating to non-GSO space stations and GSO earth stations.

The operation of transmitting and receiving non-GSO and GSO earth stations in bidirectionally allocated frequency bands may give rise to interference between stations of the two FSS applications. The magnitude of such interference depends on the transmission loss along the interfering path which, in turn, depends on factors such as length and general geometry of the interference path, the minimum operational elevation angle, antenna gain distribution as a function of time, radio climatic conditions and the percentage of time during which the transmission loss should be exceeded.

The described procedure allows the determination, in all azimuth directions from a transmitting earth station, of a distance beyond which the transmission loss would be expected to exceed a specified value for all but a specified percentage of the time. A distance so determined is called the coordination distance. The end points of coordination distances determined for all azimuths define a coordination contour around the earth station which contains the coordination area. For earth stations located outside the coordination area the probability of causing or experiencing significant interference is considered to be negligible.

Stations located outside the coordination area of a given planned station are eliminated from any coordination consideration. Consequently, the coordination requirements of a station may be strictly domestic, if the coordination area of the planned station lies entirely in the territory of the notifying administration or, domestic and international if the coordination area also includes the territory of another administration in which case the coordination agreement of that administration is required.

Stations located in the coordination area of a planned station need to be examined on a case-by-case basis initially, taking into account the antenna discrimination, separation distance and path profile if necessary.

Although based on technical data, the coordination area is an administrative concept. Since the coordination area is determined before any specific cases of potential interference are examined in detail, it must therefore rely on assumed parameters of the receiving earth stations, while the pertinent parameters of the transmitting earth stations are known.

Once the coordination area around an earth station has been computed, it can be stated, regarding another earth station to be operated in the reverse direction:

– if the earth station is to be located outside the coordination area, then there will be little risk of interference;

– if the earth station is to be located within the coordination area, then it will be necessary to carry out a detailed coordination.

The coordination area will normally be determined for the case where the non-GSO earth station is transmitting and hence capable of interfering with the reception of other earth stations. It may also be necessary to determine the coordination area for the case where the non-GSO earth station is receiving and hence capable of being interfered-with by emissions from other earth stations.

The procedure in this Annex describes the case in which the non-GSO earth station is transmitting. The methodologies apply equally to the case in which the non-GSO earth station is receiving. For the calculation of the coordination area of transmitting earth station the necessary parameters can be found in Recommendation ITU-R SM.1448. For a receiving earth station the methodologies can be used on bilateral basis only, since the parameters of the transmitting earth station with respect to which the coordination area is established will have to be provided by the responsible administration.

The coordination area of an earth station operating with a GSO space station in a slightly inclined GSO orbit should be determined for the minimum angle of elevation and the associated azimuth at which the space station is visible to the earth station.

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