Satellite Communications and Navigation

The lecture concentrates on communication aspects of modern satellite communications systems which play an important role in today's world of wireless communi-cations. A profound understanding of modulation and multiple access techniques and channel models is required.

The lecture starts with a brief sketch of the advent of satellite communications. Then, a detailed treatment of the various satellite orbits and orbit geometries is given followed by the description how to position a satellite in orbit and how to communicate during this procedure (TT&C).

Furthermore, satellite and earth station structures, the suitability of various modulation and multiple access schemes for satellite communication and the satellite channel are described. All relevant parameters affecting the communication link are summarized in a link budget which enables proper design of a satellite communications system.

Finally, as one of the main topics of the lecture, examples of today's operating and of future satellite communications systems are presented. GEO systems as well as the recently introduced LEO mobile satellite systems are described (Iridium, Globalstar and Teledesic).

Moreover, students are given an introduction to satellite navigation systems. They become familiar with orbits, coordinate systems and precise timing. Students learn the ability to compare different radio navigation methods and are familiarized with GPS signals. They discuss position and speed estimation and learn about tracking. Students learn about the various sources of error and the effects of multipath propagation for the navigation signal, which they are already familiar with. They deal with the modernization of satellite signals and interference. Students become familiar with jamming and spoofing and assess their effects.

Depending on availability and interest, the course may be supplemented by an excursion to the DLR.

Topics

Introduction: History, development and potential of satellite communications.
Satellite orbits: Kepler's laws, earth-satellite geometry, types of orbits (GEO, MEO, LEO and others), perturbations of the orbit.
Launch and installation in orbit: Early orbit phase, space environment, satellite (TT&C, station keeping, attitude and orbit control, payload)
Modulation and multiple access: FDMA, TDMA and CDMA for satellite communications, adjacent channel interference, intermodulation, handover, satellite diversity.
Satellite channel: Frequency bands, atmospheric and meteorological effects on received signal power, fade margin design, fade countermeasures, regulatory issues. Mobile satellite channel.
Link budget calculations: Description of all relevant influences on the transmission signal. Examples of link budget calculations focussing on new mobile satellite systems and their specific problems (LEO orbits, transmission in Ka-band, satellite diversity).
Mobile satellite communication systems: Iridium, Globalstar
Satellite navigation: Principle, navigation equation, error budget, GPS, Galileo