nts and co-operate to determine whether operation, the transmitters on a non-geostationary satellite and at the interference will exceed internationally agreed threshold levels. If associated earth stations must be switched off whenever this is interference problems are foreseen, acceptable solutions must be necessary to avoid causing interference to a geostationary satellite found before assignments are notified for international registration. network. However, for a geostationary satellite network, formal procedures are used to ensure that interference to or from other geostationary 26.4.2.6 Frequency co-ordination between satellite neworks satellite networks will not exceed agreed acceptable limits. These procedures must be completed, to the satisfaction of the IFRB, A mandatory procedure is used to bring together for consultation the before the satellite frequency assignments can be registered in the various administrations responsible for satellite systems that might MIFR. Two different kinds of procedure are used for this purpose, interfere with one another. These consultations are often technically according to the frequency bands in which the new satellite is to complex, since there are likely to be two bi-lateral interference operate. 26/10 Radio spectrum management SATELLITE B SATELLITE C1 Y GHz X GHz INTERFERENCE MODE 8 Y GHz X GHz X GHz INTERFERENCE Y GHz MODE 7 X GHz Y GHz EARTH STATION B EARTH STATION C1 Figure 26.5 Interference modes between fixed-satellite networks having neighbouring satellites, both networks using frequency bands X and Y but in opposite directions of transmission (Wanted signal paths are shown in broken line) A frequency and orbit allotment plan (ITU, 1990, Appendix 30B) broadcasting suffers no significant interference from the fixed sat- ellite service. has been drawn up for geostationary satellite networks of the fixed satellite service operating in the following frequency bands: 26.4.3 Links for mobile stations 1. Up links at 6.725 to 7.025GHz and/or 12.75 to 13.25GHz. 26.4.3