z7l7 where each zi is either a zero or a one ccsds

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Unformatted text preview: ch zi is either a zero or a one. CCSDS 131.0-B-2 Page 4-8 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING 5 CONCATENATED CODING 5.1 Concatenated codes shall consist of a combination of a Reed-Solomon code defined in section 4 with one of the convolutional codes defined in section 3. 5.2 The Reed-Solomon code shall be the outer code, and the convolutional code shall be the inner code. CCSDS 131.0-B-2 Page 5-1 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING 6 TURBO CODING 6.1 OVERVIEW Turbo codes are binary block codes with large codewords (hundreds or thousands of bits). Turbo codes may be used to obtain even greater coding gains than those provided by concatenated coding systems. They are systematic and inherently non-transparent. 6.2 GENERAL 6.2.1 DATA RANDOMIZATION The pseudo-randomizer defined in section 9 shall be used unless the system designer verifies that the concerns identified in the note below are resolved by other means. NOTE – The recommended Turbo codes, by themselves, cannot guarantee sufficient bit transitions to keep receiver symbol synchronizers in lock. The pseudorandomizer is also used to aid signal acquisition and to mitigate spectral lines in the transmitted signal. 6.2.2 FRAME VALIDATION When Turbo codes are used with TM or AOS Transfer Frames, the Frame Error Control Field (FECF) specified in references [1] or [2], respectively, shall be used to validate the Transfer Frame. NOTE – While providing outstanding coding gain, Turbo codes may still leave some undetected errors in the decoded output. 6.3 SPECIFICATION NOTE – A Turbo encoder is a combination of two simple encoders. The input is a frame of k information bits. The two component encoders generate parity symbols from two simple recursive convolutional codes, each with a small number of states. The information bits are also sent uncoded. A key feature of Turbo codes is an interleaver, which permutes bit-wise the original k information bits before input to the second encoder. The recommended Turbo code is a sy...
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This document was uploaded on 03/06/2014.

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