Turbo Equalization of Run Length Limited (1,9) and Low Density Parity Check Code for Super Resolution Nearfield Structure Read Only Memory Discs with 60 nm Minimum Mark Length
Oliver Theis, Xiao-Ming Chen, Dietmar Hepper, Gaël Pilard · Japanese Journal of Applied Physics · 2009
Due to severe intersymbol interference and low signal-to-noise ratio of super resolution nearfield structure (SuperRENS) random read-outs, turbo equalization techniques are applied to lower bit error rates. A d 1 k 9 r 5 run length limited (RLL) modulation code having minimum runlength d = 1, maximum runlength k = 9 and repeated minimum transition run limitation of r = 5 has been developed with emphasis on low joint bit detection and demodulation (super-trellis) complexity for use within turbo equalization schemes. Bit error rate (BER) performance of d 1 k 9 r 5 code over partial response-channels is similar to 17pp code while the super-trellis detector complexity of d 1 k 9 r 5 code is reduced. Low-frequency suppression performance of d 1 k 9 r 5 code is similar to that of 17pp code under the same DC control redundancy. BER results for measured data from a 60 nm SuperRENS read only memory disc employing an InSb mask layer, using d 1 k 9 r 5 modulation and a high-rate quasi-cyclic low density parity check (LDPC) code, correspond well to simulation results. Continuously decreasing BERs down to 2 × 10 -5 after five iterations show that a turbo equalization scheme incorporating d 1 k 9 r 5 super-trellis detection can be successfully applied in SuperRENS storage systems together with an LDPC code.