1. A block encoding method, comprising steps of: forming an original block group having n&plus;1 original blocks of m-bit message, “m” being a positive integer and “n” being an odd integer greater than “m”; encoding a first original block of m-bit message of the original block group to a reference block of n-bit codeword; and encoding n original blocks of m-bit message placed after the first original block of m-bit message in the original block group to generate n weighted blocks of n-bit codeword, each of which corresponds to an A type weighted block or a B type weighted block, depending on a bit sequence of the reference block.