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Abstract-A panoramic view on the study and design of digital designed by the DVB-T2 group. Again, the DVB-T2 specifisatellite communication links is the focus of this paper. Starting cations will be OFDM-based and will include state-of-the-art from the characterization of satellite propagation channel in solutions such as MIMO, low density parity check (LDPC) different application environments (from broadcast to fixed terminals, to broadband mobile satellite access), we address scodin scm,prolayrorte rocreinFC physical layer aspects related to satellite communications in the smart and fast synchronization techniques. attempt of providing the Reader with an overview of the new Satellite communications are not immune from this wave trends and open issues in this field.of innovation. In the DVB forum, after the publication of the DVB-S2 standard and the approval of the DVB-SH specifica-

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Two classes of turbo codes over high-order finite fields are introduced. The codes are derived from a particular protograph sub-ensemble of the (dv=2,dc=3) low-density parity-check code ensemble. A first construction is derived as a parallel concatenation of two non-binary, time-variant accumulators. The second construction is based on the serial concatenation of a non-binary, time-variant differentiator and of a non-binary, time-variant accumulator, and provides a highly-structured flexible encoding scheme for (dv=2,dc=4) ensemble codes. A cycle graph representation is provided. The proposed codes can be decoded efficiently either as low-density parity-check codes (via belief propagation decoding over the codes bipartite graph) or as turbo codes (via the forward-backward algorithm applied to the component codes trellis). The forward-backward algorithm for symbol maximum a posteriori decoding of the component codes is illustrated and simplified by means of the fast Fourier transform. The proposed codes provide remarkable gains (~ 1 dB) over binary low-density parity-check and turbo codes in the moderate-short block regimes.Comment: This paper has been withdrawn by the authors. To be presented at IEEE ICC 2011, Kyoto, Japan. June 201

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