0 b 2 page d 1 august 2011 ccsds recommended standard

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Unformatted text preview: 11 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING D3 TERMS Block Encoding: A one-to-one transformation of sequences of length k of elements of a source alphabet to sequences of length n of elements of a code alphabet, n>k. Synchronization and Channel Coding Sublayer: That sublayer of the Data Link Layer used by CCSDS space link protocols which uses a prescribed coding technique to reliably transfer Transfer Frames through the potentially noisy Physical Layer. Channel Symbol: The unit of output of the innermost encoder. Circulant: In LDPC coding, a square matrix with binary entries, where each row is a oneentry right cyclic shift of the preceding row. Codeblock: The aggregation of I codewords, where I is the interleaving depth. In this document, the term Codeblock is used for R-S coding. If I=1, the terms Codeblock and Codeword are used interchangeably. Code Rate: The average ratio of the number of binary digits at the input of an encoder to the number of binary digits at its output. Codeword: In a block code, one of the sequences in the range of the one-to-one transformation (see Block Encoding). A codeword of an (n,k) block code is a sequence of n channel symbols which are produced by encoding a sequence of k information symbols. Concatenation: The use of two or more codes to process data sequentially with the output of one encoder used as the input of the next. Connection Vector (Forward): In convolutional and Turbo coding, a vector used to specify one of the parity checks to be computed by the shift register(s) in the encoder. For a shift register with s stages, a connection vector is an s-bit binary number. A bit equal to ‘one’ in position i (counted from the left) indicates that the output of the ith stage of the shift register is to be used in computing that parity check. Connection Vector (Backward): In Turbo coding, a vector used to specify the feedback to the shift registers in the encoder. For a shift register with s stages, a backward connection vector is an s-bit binary number. A bit equal to ‘on...
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