We are currently observing a discussion about the usefulness of space research and the amount of spin-off we obtain from space programs. One area which is widely overlooked is digital communications, although it is quite clear that the application of space research which has directly affected most people is certainly space communication via satellite. Direct broadcasting satellites, international telephone callsvia geostationary satellites and the growing mobile services by satellites serve more and more users. This book provides an overview of the state-of-the-art in communications systems in space . Leading experts from arount the world the contributions in this book describe advanced features of their fields and give an outlook at the next steps in such communications systems. Special emphasis is on digital modulation and codingwhere progress in technology allows the implementation of sophisticated methods reaching almost the limits of theory. The papers include survey articles as well as advanced research topics.