Transport Layer Protocols for the Land Mobile Satellite Broadcast Channel

An important advantage of satellite transmission is their inherent capability to broadcast data to large audiences. The standard application is thereby to send data streams (i.e. TV) to wide audiences using fixed satellite receivers. An extension to this approach is broadcast to mobile receivers, especially cars. This has been realised in the U.S. by XM-Radio and Sirius. All these system have in common that they broadcast streams to receiver, which are immediately played. In contrast to this traditional broadcast models, other approaches are researched in Europe (e.g. in the ESA project Ku-Mobil and the EU project Maestro), which go away from the traditional thinking of services as streams. Instead, this new approach culminates in the idea of transferring distinguished files. For these systems, unidirectional file based transport protocols are needed, which fit into the very specifics of the land-mobile satellite environment. While broadcasting streams can make use of the well defined MPEG-protocols, file transfer via an unreliable medium is less well specified. In the following an Internet Protocol (IP) based transport scheme is analysed, where the main focus is on protocols from the IETF Reliable Multicast Group. There, the combination of the Layered Coding Transport (LCT) protocol with the Asynchronous Layered Coding (ALC) and the File Delivery over Unidirectional Transport (FLUTE) protocol seems a most promising candidate for this kind of application. The basic mechanism of these protocols and their behaviour in the land mobile environment is shown and analysed.