A necessary and sufficient condition for time-variant convolutional encoders to be noncatastrophic
Linear convolutional encoders whose rate and generator polynomials periodically vary with time are considered. A system of linear recurrent equations defined by the parameters of the encoder is introduced, and it is shown that the encoder is noncatastrophic if and only if there exists an au toregressive filter realizing these equations. A necessary and sufficient condition for encoders to be noncatastrophic, formulated using this fact, may be simpler than a condition that can be obtained from the known result by Massey and Sain.
KeywordsConvolutional Code Residue Class Generator Polynomial Constraint Length Code Trellis
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