Performance Investigation of Soft-Decodable Runlength-Limited Codes With Different Minimum Runlength Constraints in High-Density Optical Recording

This paper investigates the performance of runlength-limited (RLL) codes with different d constraints in high-density optical recording, for both the low-density parity-check (LDPC)-coded Bliss scheme and the standard concatenation scheme. For the d = 5 constraint, we propose a low-complexity compression/decompression scenario that maps each 6-bit channel codeword to a 3-bit "compressed codeword" by Gray-alike coding of the position of the transition in the 6-bit codeword, to compensate the density loss introduced by the redundancy of LDPC coding in the LDPC-coded Bliss scheme. Using a scalar diffraction channel model, we ran simulations to compare the performance of RLL codes with four different d constraints: d = 0,1,2, and 5, in near-field optical recording systems. The simulation results address the average bit error number in erroneous symbols after soft-input soft-output channel detection. Further, we evaluated the net density with different sets of simulation parameters, for both the LDPC-coded Bliss scheme and the standard concatenation scheme, considering jitter noise and additive white Gaussian noise, respectively.