Reduced complexity sequence detection for high-order partial response channels

Detector hardware complexity of high-order partial response magnetic read channels is a major obstacle to high data rate operation and reduced area and power consumption. The method presented here reduces the complexity of single-step and two-step implementations of the Viterbi detector by applying a distance-enhancing code that eliminates some states from the code trellis. The complexity of the detector is further reduced by eliminating less-probable branches from the trellis. This is accomplished by a simple control mechanism that uses the signs of the consecutive input samples. The reduced set of add-compare-select (ACS) units is dynamically assigned to the detector states, decreasing the complexity of the Viterbi detector by roughly 50%. This method is demonstrated on high-order partial response systems with the E²PR4 target and an 11-level/32-state target. The simulation results show negligible bit error rate (BER) degradation for signal-to-noise ratios in the range of operation of contemporary disk drive read channels.