Jk. Moon et S. She, CONSTRAINED-COMPLEXITY EQUALIZER DESIGN FOR FIXED DELAY TREE-SEARCH WITH DECISION-FEEDBACK, IEEE transactions on magnetics, 30(5), 1994, pp. 2762-2768
Fixed delay tree search with decision feedback (FDTS/DF) is a hybrid d
etection scheme which incorporates a sequence detector into the decisi
on feedback equalizer (DFE). When applied to minimum-runlength-limited
channels, the FDTS/DF provides near-optimal detection performance wit
h a reasonable complexity requirement. It has been shown recently that
for the special case of search depth 1 and the channel subject to the
d = 1 run length constraint, a simpler structure arises for the decis
ion elements of the FDTS/DF, which provides asymptotically-equivalent
performance to the originally proposed FDTS/DF structure. We demonstra
te the asymptotic optimality of this reduced FDTS/DF based on a simple
signal-to-noise ratio argument. We also introduce a design criterion
for choosing tap weights for the constrained-complexity FDTS/DF, which
assumes the finite impulse response (FIR) structure for its forward a
nd feedback filters. A method to compute optimal tap weights for the f
orward and feedback filters is then presented for a magnetic recording
channel subject to the popular minimum runlength constraint, d = 1. R
esults show that under the d = 1 constraint, the FDTS/DF with one-bit
decision delay achieves a large performance improvement over the DFE.