Joint turbo channel detection and RLL decoding for (1, 7) coded partial response recording channels

Runlength limited (RLL) codes are essential in recording systems for minimizing distortions and maintaining bit synchronization. In this paper, we investigate the application of turbo codes on RLL (1,7) coded partial response equalized recording channels. We proposed a ´combined trellis´ approach for doing ´soft-in soft-out´ (SISO) channel detection and RLL decoding jointly. This approach makes the implementation of turbo equalization easier since it eliminates the need for a ´SISO RLL encoder´ in the feedback path from turbo decoder to channel detector. Simulation studies on magnetic recording channels show that our approach provides a coding gain of about 4 dB compared to Viterbi detection at 10^-6 bit error rate.