The poset metrics that allow binary codes of codimension m to be m-, (m - 1)-, or (m - 2)-perfect

A binary poset code of codimension m (of cardinality 2n-m, where n is the code length) can correct maximum m errors. All possible poset metrics that allow codes of codimension m to be m-, (m-1)- or (m - 2)-perfect are described. Some general conditions on a poset which guarantee the nonexistence of perfect poset codes are derived.