This document discusses the history and basics of satellite communication systems. It covers: - The first satellites launched in the 1940s-1990s and the development of satellite phone systems. - The types of satellite orbits including LEO, MEO, and GEO and how factors like altitude and inclination determine satellite period and coverage areas. - How satellite systems extend cellular networks to provide global mobile communication through techniques like inter-satellite links and handovers between satellites and gateways. - The challenges of satellite systems including higher latency compared to terrestrial networks and the need for complex routing and localization as satellites move.

4. Classical satellite systems base station or gateway Inter Satellite Link (ISL) Mobile User Link (MUL) Gateway Link (GWL) footprint small cells (spotbeams) User data PSTN ISDN GSM GWL MUL PSTN: Public Switched Telephone Network

6. Satellite period and orbits 10 20 30 40 x10 6 m 24 20 16 12 8 4 radius satellite period [h] velocity [ x1000 km/h] synchronous distance 35,786 km

8. Inclination inclination   satellite orbit perigee plane of satellite orbit equatorial plane

9. Elevation Elevation: angle  between center of satellite beam and surface  minimal elevation: elevation needed at least to communicate with the satellite footprint

11. Atmospheric attenuation Example: satellite systems at 4-6 GHz elevation of the satellite 5° 10° 20° 30° 40° 50° Attenuation of the signal in % 10 20 30 40 50 rain absorption fog absorption atmospheric absorption 

13. Orbits II earth km 35768 10000 1000 LEO (Globalstar, Irdium) HEO inner and outer Van Allen belts MEO (ICO) GEO (Inmarsat) Van-Allen-Belts: ionized particles 2000 - 6000 km and 15000 - 30000 km above earth surface

20. Overview of LEO/MEO systems