S.V. Popov

There are presented the results of global and regional mobile satellite communication systems - construction analysis with regard to radio interfaces of L- and S-bands, which have a number of special features in spatial-frequency allocation of transmission channels. One of the features is a very great transmission range from the subscriber-s terminal (ST) to the spacecraft (S/C), which plays the part of the base station (BS), preserving simultaneously the ST portability and low power. The length of the ST - S/C distance in satellite communication systems (SCS) is ranging from 700 km to 40 000 km. At the present time the low, inclined and polar orbits with altitude of 700-1500 km as well as equatorial orbits with altitude of 2000 km are being assimilated more intensively. The low orbits have essential advantages over other types of orbits on energy characteristics, however they lose on duration of communication sessions and satellite-s life time. Such systems as «Globalstar» and «Iridium» have been created and are now functioning at low orbits. Subscriber terminals of these systems are exploited by wide circle of users, including the governmental and military agencies of the USA and other developed countries, as well as by collective forces (NATO). The route of MEO satellites passes between the first and the second Van-Allen belts, i.e at the altitude of 5 to 15000 km. The satellite-serviced area for each satellite is significantly smaller than the same area of a geostationary satellite, that is why the groups of 8 - 12 satellites are needed for the global single coverage of the densely populated territories of the globe and of navigable waters. Alongside with quick development of global LEO-and-MEO multi-satellite personal communication systems being observed the last years, a number of regional satellite communication systems are successfully developing, which operate within the frequency band under consideration and are deployed on the basis of geostationary satellites. The regional systems are being developed and produced as augmentations to the existing ground telecommunication systems of different countries with the purpose to combine these structures and to expand their capabilities in provision of communication services at the territory of the whole region, including the regions, where the deployment of ground based communication systems is economically disadvantageous. The key guidelines for building the listed systems are considered in the article.