Accommodation of feeder-links of non-geostationary satellites for personal communications in frequency bands allocated to the fixed-satellite service

Stimulated by industrial developments towards personal communications links via constellations of non-geostationary (NGSO) satellites, the Administrative Radio Conference of 1992 made allocations to the mobile-satellite service (MSS) in the range 1-3 GHz, but no specific provision for the feeder-links to and from such constellations was made at that time, other than to recognise that Radio Regulation (RR) No. 22 allows bands allocated to the fixed-satellite service (FSS) to be used for the feeder-links of other space services. The subsequent increase in the pace of development prompted the World Radiocommunication Conference of 1993 (WRC-93) to request the ITU-R to carry out interference studies in all FSS bands below 30 GHz, to provide a basis for WRC-95 to take appropriate decisions regarding the spectrum for the feeder-links. The ITU-R Study Group 4 therefore investigated the frequency sharing problems which would potentially occur if NGSO MSS feeder-links were implemented alternatively in the 4-7 GHz range, the 11-16 GHz range and the 18-30 GHz range. The paper outlines the scenarios studied, gives examples of the quantitative results obtained, indicates the principal conclusions and summarises the relevant outcomes from WRC-95.