Concatenated convolutional codes: Applications to deep-space telecommunication

The performance of concatenated convolutional codes used for the Voyager missions to Jupiter and Saturn are examined. The fundamental results are as follows: (1) the codes, called the composite, admit an optimal decoder algorithm; (2) the optimal two stage decoder is degenerate, that is, only the outer member of the decoder pair is necessary, and performance suffers by comparison with the optimal decoder; (3) the examination of the codes defines a burst error of length l and the number of such burst errors is computed for each l; and (4) the error statistics were used to estimate the performance of four suboptimal outer decoder configurations designed to use the burst nature of the inner decoder output. It is concluded that concatenation is best limited to fixed channels required to pass data sets of differing quality requirements. In that way the composite code can be effectively utilized.