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

Claim 1

Apparatus for the reception of a stream of binary code elements which form a sequence of n-tuples of an (n, k, p, u) error-correcting convolutional code, wherein k/n is the coding efficiency, p is the encoding constraint length, and u>p is the decoding constraint length, which apparatus comprises: first-syndrome forming means (220, 222, 224, 226) for forming a sequence of (n-k)-tuples of syndrome elements in synchronism with the reception of n-tuples of code elements; a logic unit (250) having first storage means (228-241) for storing a progressing sequence of u (n-k)-tuples of syndrome elements, and for forming, in synchronism with the reception of the n-tuples of code elements, a further sequence of j-tuples of correction elements (f1) at a first output, wherein j=k for a systematic code and j=n for a non-systematic code; a correction apparatus (250) having second storage means (206-218) for storing at least the information containing part of the sequence of n-tuples of code elements during a time corresponding to at least u bit cells and for bitwise adding this thereafter modulo-2 to the corresponding j-tuple of correction elements; a feedback connection (242-248) for supplying said sequence of j-tuples of correction elements to said logic unit for updating the (n-k)-tuples of syndrome elements stored therein so as to compensate these for the effects of the correction executed on said sequence of n-tuples of code elements; modified-syndrome (252) forming means for forming at a second output, after the correction by means of said j-tuple of correction elements, an element of a sequence composed of (n-k)-tuples of modified-syndrome elements formed as based on the corrected sequence of n-tuples of code elements, where a first signal value of an (n-k)-tuple of modified syndrome elements indicates that a correct correction can have taken place, but all other values thereof that no correct connection can have taken place; signalling means (254-264) connected to said second output for, upon receiving a predetermined amount of said other values, generating an unreliability signal; characterized in that said first storage means constitute an address register to a read-only memory (250) having a plurality of separately addressable word locations and being contained in said logic unit, in that said modified-syndrome forming means comprise at least part of said read-only means co-addressable by outputs from said first storage means, and in that said signalling means comprise third storage means for storing a further sequence of said modified-syndrome (n-k)-tuples, and OR-ing means (264) for OR-ing a predetermined number of said other signal values for thereby producing said unreliability signal.