Apparatus for the processing of an information stream with the aid of an error-correcting convolutional code and for the detection of an error still irremediable in this processing.

摘要

A sequence of k-tuples of information elements is converted by means of an error-correcting convolutional code into a sequence of n-tuples (n greater than k) of code elements. In the processing of the code elements use is made first of a syndrome former (226) to form a sequence of (n-k)-tuples of syndrome elementsfrom the n-received sequence of n-tuples of code elements. From a segment of a number of successive (n-k)-tuples of syndrome elements one or more correction bits (f, ) are formed in each case so as to be able to correct the received code bits and also, if a correction is applied, to be able to update a number of further syndrome bits from that same segment. Furthermore an (n-k)-tuple of secondary syndrome bits or a residue bits is formed (at 252) in each case from this updated segment. A first value of such an (n-k)-tuple indicates the state in which the decoder must be provisionally considered as having corrected all errors in a predetermined sequence of n-tuples of code elements. All other values indicate that certainly an error has remained uncorrected. Such an other value is converted into an unreliability signal. The unreliability signal indicates a subsequence of n-tuples of code elements, in which the errors not to be corrected are located. Outside this subsequence the n-tuples can be reliable again.