A method of optimizing the size of blocks of coded data intended to be
subjected to an iterative decoding process, a maximum error rate of the
iterative decoding process being fixed in advance, in which there are
sought, among a plurality of block sizes (N/k) which are submultiples of
the normal block size by an integer factor (k) greater than or equal to 1
and a plurality of integers giving the maximum number of iterations that
can be effected by the said iterative decoding on a block, (1) a
submultiple size, and (2) a maximum number of iterations such that they
are compatible with the maximum error rate, and such that the mean number
of iterations that will be applied by the iterative decoding process on a
block of submultiple size is minimized.