Optimal filter design for fixed delay tree search with decision feedback

Fixed delay tree search with decision feedback (FDTS/DF) is a hybrid detection scheme which incorporates a sequence detector into the decision feedback equalizer (DFE). It has been shown previously that the relatively simple FDTS/DF provides a near optimal detection performance for runlength-constrained data storage channels. This paper introduces a design criterion for choosing tap weights for the constrained-complexity FDTS/DF, which assumes the finite impulse response (FIR) structure for its forward and feedback filters. A method to compute optimal tap weights for the forward and feedback filters is then presented for a magnetic recording channel subject to the popular minimum runlength constraint d=1. Results show that under the d=1 constraint, FDTS/DF with one-bit decision delay achieves a large performance improvement over DFE