Multistage decoding using erasing technique for multilevel coding

Families of BCM (block-coded modulation) that allow the use of suboptimal multistage decoding procedures having performance/complexity advantages over MLD (maximum likelihood decoding) are proposed. The process of decoding is performed in two steps: a first estimate of the codeword is obtained by a hard decision device, and the associated decoding is carried out to correct the eventual errors. The criterion of erasing, i.e. how to define the erasing procedure in the first step of decoding in order to maximize the coding gain, is discussed for both PSK and QAM modulations. The erasing technique is performed by defining some `erasing-areas´. The analytic results show that significant coding gain can be achieved with respect to a nonerased equivalent scheme