Turbo equalization utilizing soft decision feedback

Abstract

Detection schemes that utilize hard decision feedback (HDF) have not found practical applications in magnetic recording (MR) because of the detrimental impact of error propagation on the performance of the outer error-correcting code. In the context of turbo equalization of high-density MR channels, we study the impact of the error propagation on the performance. Through the extrinsic information transfer chart and the so-called worst case (rather than average) simulated trajectory of mutual information, we demonstrate that under strong residual intersymbol interference, error propagation is efficiently suppressed if soft decision feedback is used in place of HDF.