Analysis of system parameters for LEO/ICO-satellite communication networks

Currently many efforts are undertaken to develop and install communication networks based on low Earth orbit (LEO) and intermediate circular orbit (ICO) satellites. However, many problems are to be solved before the final operation of such networks. This paper deals with basic design problems of LEO/ICO-based networks. The topology of the satellite network is considered and estimates for the number of satellites necessary, orbits and number of communication channels per satellite are derived. The features and consequences of intersatellite links are discussed. The number of communication channels per link is derived with a more elaborate model. This includes the radio links from the satellites to mobile users and to gateways, as well as intersatellite links and terrestrial lines. We introduce a formal model for LEO/ICO based networks and propose a method for the evaluation of the link capacities, given the network topology and the traffic requirements. As an example, two constellations are investigated in detail. One of these constellations is the Iridium system proposed by Motorola, the other is the LEONET concept developed in an ESA study. Finally, the influence of unequal traffic distribution is discussed