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The recommended turbo code is a systematic code that

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Unformatted text preview: stematic code that shall conform to the following specifications: a) Code type shall be systematic parallel concatenated Turbo code. b) Number of component codes shall be two (plus an uncoded component to make the code systematic). CCSDS 131.0-B-2 Page 6-1 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING c) Type of component codes shall be recursive convolutional codes. d) Number of states of each convolutional component code shall be 16. e) Nominal code rates shall be r = 1/2, 1/3, 1/4, or 1/6 (selectable). NOTE – Because of ‘trellis termination’ symbols (see 6.3j)), the true code rates (defined as the ratios of the information block lengths to the codeblock lengths in table 6-2) are slightly smaller than the nominal code rates. In this Recommended Standard, the term ‘code rate’ always refers to the nominal code rates, r = 1/2, 1/3, 1/4, or 1/6. f) The specified information block lengths k shall be those specified in table 6-1. The corresponding codeblock lengths in bits, n=(k+4)/r, for the specified code rates shall be those specified in table 6-2. NOTE – Information block lengths are chosen for compatibility with the corresponding Reed-Solomon interleaving depths, also shown in table 6-1. CCSDS 131.0-B-2 Page 6-2 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING Table 6-1: Specified Information Block Lengths Information block length k, bits Corresponding Reed-Solomon interleaving depth I Notes 1784 (=223 × 1 octets) 1 For very low data rates or low latency 3568 (=223 × 2 octets) 2 7136 (=223 × 4 octets) 4 8920 (=223 × 5 octets) 5 For highest coding gain Table 6-2: Codeword Lengths for Supported Code Rates (Measured in Bits) Information block length k Codeword length n rate 1/2 rate 1/3 rate 1/4 rate 1/6 1784 3576 5364 7152 10728 3568 7144 10716 14288 21432 7136 14280 21420 28560 42840 8920 17848 26772 35696 53544 g) Turbo code permutation for each specified block length k shall conform to a particular reordering of the integers 1, 2, . . ., k as generated by the following algorithm. NOTE –...
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