Turbo Equalization With Single-Parity Check Codes and Unequal Error Protection Codes

The performance of turbo equalization with interleaved single-parity check codes on partial-response channels is evaluated. Single-parity check codes are weak codes, but are shown to have modest performance gain. The proposed system achieves gains of 3.5, 3.4, 2.7, and 2.4 dB with code rates of 19/20,24/25,49/50, and 63/64, respectively, at a BER of 10^-5. The complexity of the proposed decoder is significantly lower than that of turbo equalization using standard low-density parity-check codes. These single-parity check codes are modified to be unequal error protection codes, designed to decrease the probability that Viterbi error events span Reed-Solomon symbol boundaries, resulting in a decrease of the sector error rate. Once such code gains an additional 0.1 dB over a single-parity check code of the same code rate of 24/25