Aspects of Satellite Constellation and System Connectivity Analysis

Abstract

Recent years have seen many efforts in the field of communication networks based on constellations of non-geostationary satellites. The paper addresses an in-depth analysis of these systems, from three different viewpoints: geometrical, transmission quality and network connectivity. The geometrical analysis yields the statistics for coverage, frequency of satellite handovers and link absence periods. The transmission quality analysis is based on a general model valid for all access techniques, which is here applied to the case of FDMA. The outage probability as a function of the specification on carrier-to-interference power ratio is evaluated for a few selected constellations, also considering some possible interference-reduction techniques (spot turn-off, intra-orbital plane frequency division, and inter-orbital plane frequency division). The approach is extended to the case of non-ideal propagation conditions, namely non-selective multipath fading and shadowing. Finally, a formal model for networks based on non-geostationary satellite constellations as well as a traffic engineering concept are introduced, both forming a basis for a detailed network connectivity analysis. Given the network topology and the traffic requirements, the main task is the assessment of capacity requirements on the different links within the network, including the radio links from the satellites to mobile users and to gateways, as well as intersatellite links and terrestrial lines. A software tool for the numerical evaluation is presented together with some representative results on worst-case and average link capacity requirements, on-board RF power figures, and propagation delays.