Symbol-level synchronization using probability lookup-table for IDS error correction

Insertion/Deletion/Substitution (IDS) error correction will become important for future high-density storage devices, e.g., bit-patterned media. For IDS error correction, concatenated codings of an outer LDPC code and an inner marker code have been proposed. To improve the synchronization capability, marker decoder can employ symbol-level synchronization (SLS) with a large symbol size, while the computational time complexity of the SLS increases exponentially with the symbol size. This paper proposes an SLS using a probability lookup table to reduce the complexity. Probabilities in the table are precomputed for given channel and code parameters, and computationally intensive calculations of the SLS are replaced by table lookups. The proposed method is applicable to both single-path and multipath decodings. The bit error rate (BER) is evaluated for SLS of symbols sizes bS = 1, 2, 4, and 8 bits, and it is confirmed that larger symbol size gives lower BER.