Future developments

For communication by satellite between fixed earth stations the distant future lies in a struggle, technical and economic, with terre­strial systems, cabled or by radio relay system. How fast will the public telecommunications network become converted to a univer­sally available, omni-purpose, global, integrated, synchronised, digital network? To what degree will satellites provide special communication facilities that the world is going to want and which are not available at an acceptable price from that integrated global network?

Who can tell? It seems likely, however, that in the nearer future the use of satellites for main links in the public telecommunications network will grow, as the world economy grows, but perhaps at a slower rate than hitherto and under strong pressure to minimise costs. On the other hand, there may well be considerable growth in the use of powerful satellites and small earth stations for a variety of other purposes. Thin route public network systems will bring modern telecommunications facilities to sparsely populated and under developed areas. Private networks using VSATs may provide cost effective data transmission in some circumstances. Above all, use will be found for satellites for limited access multi-destination transmissions, 'narrow casting' as it is sometimes called, for con­ference television and for other situations where wide bandwidth is required for short periods. Indeed the indications are that the use of satellites for purpose of this kind may be limited, for the developed regions of the World, not by shortage of demand but by difficulties of supply, arising from increasing congestion in the geostationary satellite orbit. These difficulties will, no doubt, lead to the use of the frequency bands allocated to the fixed satellite service around 20GHz and 30GHz (see Table 51.1) for applications where the additional cost of operating in these bands can be absorbed.

It is clear that there will be strong growth in demand for the use of satellites for communication with mobile stations, and in particu­lar with road vehicles in sparsely populated regions. There will also be a considerable demand for communication by satellite with aircraft, to provide telephone services for passengers and probably also for air traffic control purposes. Major growth could not be supplied without an increase in the bandwidth allocated for these purposes in a technically suitable part of the spectrum, and an administrative conference of the ITU, meeting in February 1992, considered proposals for making such an increase. These proposals include provision for low orbiting satellites, which would have advantages for service to road vehicles and in particular to hand portable radio telephones.

Development of high definition television (HDTV) is in progress in many countries. Most of the systems that have been announced so far require much more information to be transmitted than is needed for standard definition TV. In consequence there are no ready means, terrestrial or satellite, of distributing such signals widely and there is interest in securing a new frequency allocation for satellite broadcasting of HDTV, probably around 20GHz. A second broadcasting development looks towards multi channel sound broadcasting of 'CD-quality' that could be received in motor cars; for this purpose another new frequency allocation is being sought, but this would have to be much lower in the spectrum, probably below 3GHz. The ITU Conference in 1992 will consider proposals for both of these developments.

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