Video transmission over mobile satellite systems

Mobile satellite communication channels are characterized by long transmission delays, variation of these delays, high bit-error-rates, shadowing and the multipath e!ect which severely reduce the quality of video services. Error control techniques including feedback mechanisms, error concealment methods, forward error correction techniques and error resilience schemes are examined in this paper for achieving a highintegrity video transmission over a mobile satellite channel. The application of three di!erent error resilience algorithms, namely Turbo codes, error-resilient entropy codes and two-way decoding using reversible codes is presented. Their joint performance is also examined. Furthermore, a low-delay and low-complexity video transcoding algorithm which fully interconnects two very low bit rate video communication standards: MPEG-4 and H.263 is also elaborated. This transcoder works as a gateway tool which links two heterogeneous multimedia networks, such as a mobile satellite network and a land-based network, with negligible processing delay and complexity. Copyright ( 2000 John Wiley & Sons, Ltd.