Optimal binary linear codes of length \(18\) containing the \([6, 5, 2]\otimes[ 3, 1, 3]\) product code are presented. It is shown that these are \([18, 9, 5]\) and \([18, 8, 6]\) codes. The soft-decision maximum-likelihood decoding complexity of these codes is determined. From this point of view, these codes are better than the \([18, 9, 6]\) code.
1970-2025 CP (Manitoba, Canada) unless otherwise stated.