Low complexity decoding schemes for single-parity-check (spc) based concatenated codes

Abstract

This invention provides an iterative PCZZ data decoder that includes circuitry for utilizing all extrinsic information during iterative decoding by updating likelihood information for parity bits L, i=1, . . . , M during iterations. The extrinsic information for the parity bits is included in iterations by re-calculating soft values for parity bits Lfor each iteration k. In one embodiment the parity bit soft values are re-calculated in a plurality of circuit blocks following Max-Log-APP (MLA) decoder blocks, based on soft values for data bits L. In another embodiment the parity bit soft values are re-calculated recursively within the plurality of MLA decoders. The decoder operates to control the convergence of the decoder by monitoring a soft value of one parity check symbol, e.g., L[p(IM)], where p(IM) represents the last parity check bit in an I×M parity check array. A decoder iteration stopping rule may be implemented by testing a likelihood measure associated with a last parity check symbol in a parity check column. In one case the likelihood measure may be given by L[p(IM]>threshold, and in another case the likelihood measure may be given by L[p(I)]>threshold. The likelihood measure is given in general by: L[p(I)]>threshold, L[p(2I)]>threshold, . . . , L[p(IM)]>threshold, where the value of the threshold is a function of data block size.