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Unformatted text preview: e’ 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 the
feedback value, except for the leftmost bit which is ignored.
Constraint Length: In convolutional coding, the number of consecutive input bits that are
needed to determine the value of the output symbols at any time.
Convolutional Code: As used in this document, a code in which a number of output
symbols are produced for each input information bit. Each output symbol is a linear
combination of the current input bit as well as some or all of the previous k1 bits where k is
the constraint length of the code. CCSDS 131.0B2 Page D2 August 2011 CCSDS RECOMMENDED STANDARD FOR TM SYNCHRONIZATION AND CHANNEL CODING Differential Encoding: a signaling technique used to resolve phase ambiguities with certain
modulations, equivalent to NRZM signaling.
Expurgated Code: A subcode of lower rate obtained by deleting some of the codewords
from another code. This may be accomplished by removing rows from a generator matrix, or
adding rows to a paritycheck matrix.
GF(n): The Galois Field consisting of exactly ‘n’ elements.
Inner Code: In a concatenated coding system, the last encoding algorithm that is applied to the
data stream. The data stream here consists of the codewords generated by the outer decoder.
LDPC Code: An error correcting code with codewords taken as the set of vectors in the
nullspace of a sparse matrix, called a lowdensity paritycheck matrix. In this document,
modifications of such codes through puncturing, expurgation, etc., are also considered LDPC
codes.
Modulating Waveform: A way of representing data bits (‘1’ and ‘0’) by a particular
waveform.
NRZL: A data format in which a data ‘one’ is represented by one of two levels, and a data
‘zero’ is represented by the other level.
NRZM: A data format in which a data ‘one’ is represented by a change in level and a data
‘zero’ is represented by no change in level.
Outer Code: In a concatenated coding system, the first encoding algorithm that is appli...
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This document was uploaded on 03/06/2014.
 Spring '14

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