Method of reading data from storage device, error correction device and storage system including error correction code decoder

An error correction device comprising:

• a memory configured to store first data received from an external device, store reliability data indicating reliabilities of the first data, and output the received data and the reliability data;
• a log-likelihood ratio mapper configured to output first mapped data by mapping first log-likelihood ratios to the first data output from the memory and output second mapped data by mapping second log-likelihood ratios to the first data and reliability data output from the memory;
• a decision unit configured to perform a low density parity check (LDPC) decoding based on the first mapped data or the second mapped data;
• and
• a log-likelihood ratio reliability updater configured to receive a decoding result based on the first mapped data from the decision unit, compare the decoding result with the first data stored in the memory and generate the reliability data indicating reliability of each bit of the first data according to the comparison result to store the generated reliability data on the memory.

A storage system comprising:

• a storage device;
• and
• a controller configured to receive first data read from the storage device, the controller including a first error correction code decoder correcting an error of the received data,
• wherein the first error correction code decoder includes,
• a memory configured to store the first data and reliability data indicating reliabilities of the first data, and to output the read data and reliability data;
• a log-likelihood ratio mapper configured to map first log-likelihood ratios to the first data output from the memory to output first mapped data, and map second log-likelihood ratios to the first data and the reliability data output from the memory to output second mapped data;
• a decision unit configured to perform a low density parity check (LDPC) decoding based on the first mapped data or the second mapped data;
• and
• a log-likelihood ratio reliability updater configured to receive a first decoding result based on the first mapped data from the decision unit, compare the first decoding result with the first data stored in the memory and generate the reliability data indicating reliability of each bit of the first data according to the comparison result to store the generated reliability data on the memory, the log-likelihood ratio reliability updater being configured to perform a first error correction operation on the first data based on the second decoding result according to the second mapped data.

A method of reading data from a storage device comprising:

• performing a hard decision reading operation to generate hard decision data, the hard decision reading operation including,
• reading data stored in the storage device using first read voltages,
• generating a plurality of reliability bits corresponding to each of a plurality of read bits by performing a decoding operation based on the read data, the read bits being bits of the read data, and
• performing a first error correction operation on the read data based on the read data and the reliability bits;
• generating a comparison result based on the hard decision data;
• and
• determining whether to perform a soft decision reading operation on the data stored in the storage device using fractional read voltages different than the first read voltages, based on the comparison result.