Process for transmitting information bits with error correction coding, coder and decoder for the implementation of this process

DETAILED DESCRIPTION The invention therefore proposes, in a process of the type indicated in the introduction, that a set of Y bits respectively having Y determined positions in the second binary matrix should not be transmitted towards the channel, and that the receiver places in the input matrix, in positions corresponding to the Y determined positions of the second binary matrix, samples the absolute values of which are representative of maximum confidence.
The invention makes use of a technique similar to the puncturing techniques frequently used in the field of convolutional codes.
The puncturing increases the efficiency of the code.
In the case of convolutional codes, its aim is generally to achieve coding efficiencies in excess of 1/2 while using binary codes, i.
e.
those which have the least complex decoding trellis.
In general, a punctured convolutional code has distance properties similar to those of a non-punctured code of identical efficiency.
Puncturing, however, is not normally applied to block codes.
In fact, there are numerous block codes with high efficiencies having optimum distance properties.
It would therefore be expected that puncturing would degrade distance properties without achieving a gain in complexity which would be as appreciable as in the case of convolutional codes.
The inventors were surprised to observe that, in the case of a product code, puncturing applied as indicated above, combined with the soft decision iterative decoding process, does not significantly degrade the performance of the codec.
Let n, k and d be the product code parameters, in the form: ##EQU1## where L is the number of elementary codes the respective parameters of which are (n.
sub.
1, k.
sub.
1, d.
sub.
1) (the case where L=2 is considered below, without limiting generality).
k and n are the respective numbers of bits in the "first" and "second" binary matrices.
The invention allows the number of redundancy bits contained in the matrix to be adapted to any number n-k-Y less than or equal to n-k, the receiver decoding circuit being the same whatever the number Y of punctured bits