Broadband Satellite Communication Systems and the Challenges of Mobility is an essential reference for both academic and professional researchers in the field of telecommunications, computer networking and wireless networks. Recently the request of multimedia services has been rapidly increasing and satellite networks appear to be attractive for a fast service deployment and for extending the typical service area of terrestrial systems.  In comparison with traditional wide area networks, a characteristic of satellite communication systems is their ability in broadcasting and multicasting multimedia information flows anywhere over the satellite coverage.  The papers presented in this volume highlight key areas such as Satellite Network Architectures, Services and Applications; Mobile Satellite Systems and Services; and Hybrid Satellite and Terrestrial Networks. Mobility will inevitably be one of the main characteristics of future networks, terminals and applications and, thus, extending and integrating fixed network protocols and services to mobile systems represents one of the main issues of present networking.  The secondary focus of this volume is on challenges of mobility, that is, on technologies, protocols and services for the support of seamless and nomadic user access to new classes of applications in person-to-person, device-to-device and device-to-person environments.  The book comprises recent results of research and development in the following areas; Seamless mobility; Mobile ad hoc and sensor networks; Analysis, simulation and measurements of mobile and wireless systems;  Integration and inter-working of wired and wireless networks; QoS in mobile and wireless networks; Future trends and issues concerning mobility. This state -of-the-art volume contains a collection of papers from two of the workshops of the 18th IFIP World Computer Congress, held August 22-27, 2004, in Toulouse, France: the Workshop on Broadband Satellite Communication Systems, and the Workshop on the Challenges of Mobility.