Log-likelihood ratio (LLR) dampening in low-density parity-check (LDPC) decoders

摘要

Described embodiments provide a media controller to read data stored in a media. The media controller determines a value for each bit of a shortened codeword from the media. The shortened LDPC codeword includes a plurality of non-shortened bits of a full codeword, where the full codeword includes the plurality of non-shortened bits and one or more shortened bits. Shortened bits correspond to bits unused in the shortened codeword. The media controller converts the determined values for each bit of the shortened codeword into a first set of log-likelihood ratio (LLR) values. The full codeword is decoded using the first set of LLR values for the shortened codeword. If the LDPC decoding fails, the media controller dampens one or more LLR values corresponding to non-shortened bits of the codeword to produce a second set of LLR values and starts a second LDPC decoding trial using the second set of LLR values. The dampening of LLR values includes scaling by a predetermined scaling factor and decreasing their magnitude by a predetermined amount.