High-speed satellite mobile communications: Technologies and challenges

The central features of the future fourth-generation mobile communication systems are the provisioning of high-speed data transmissions (up to 1 Gb/s) and interactive multimedia services. For effective delivery of these services, the network must satisfy some stringent quality-of-service (QoS) metrics, defined typically in terms of maximum delay and/or minimum throughput performances. Mobile satellite systems will be fully integrated with the future terrestrial cellular systems, playing important roles as backbones or access satellites, to provide ubiquitous global coverage to diverse users. The challenges for future broadband satellite systems, therefore, lie in the proper deployments of state-of-the-art satellite technologies to ensure seamless integration of the satellite networks into the cellular systems and its QoS frameworks, while achieving, to the extent possible, efficient use of the precious satellite link resources. This paper presents an overview of the future high-speed satellite mobile communication systems, the technologies deployed or planned for deployments, and the challenges. Focusing in particular on the nonlinear downlink channel behavior as well as shadowing and multipath fading, various physical channel models for characterizing the mobile satellite systems are presented. The most prominent technologies used in the physical layer such as coding and modulation schemes, multiple-access techniques, diversity combining, etc., are then discussed in the context of the satellite systems. High-speed and QoS-specific technologies, such as onboard processing and switching, mobility and resource managements, IP routing, and cross-layer designs, employed in the satellite systems are also discussed.