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  or , respectively, shall be used to validate the Transfer
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.
- Spring '14