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Mismatched FiniteComplexity MMSE Decision Feedback Equalizers

Summary: Mismatched Finite­Complexity MMSE Decision
Feedback Equalizers
Naofal Al­Dhahir \Lambda , Member, IEEE, and John M. Cioffi, Fellow, IEEE
Closed--form expressions that quantify the degradation in the decision--point signal--to--noise ratio of
the finite--length minimum mean--square--error decision feedback equalizer (MMSE---DFE) due to channel
and noise mismatch conditions are derived. The analysis is further extended to other receiver structures,
namely the MMSE--DFE with an adaptive feedforward filter, the MMSE linear equalizer, and the discrete
multitone transceiver, all under a finite--complexity constraint. The limiting case of infinite--length filters
is also analyzed.
In addition, we present computer simulation results that compare the performance of the various
receiver structures under study, assuming a particular channel and noise mismatch model for the high--
bit--rate digital subscriber loop environment. Finally, several methods that can be used to mitigate the
effects of mismatch are outlined.
I. Introduction
Approaching theoretical performance limits on dispersive noisy channels requires optimization of
both the transmitter and receiver ends of a communication system. This optimization process is
based on accurate knowledge about the channel and noise characteristics. For instance, the optimum
feedforward and feedback filter settings of the minimum mean--square--error decision feedback equalizer
(MMSE--DFE) are a function of the channel impulse response (CIR) coefficients and the noise auto--


Source: Al-Dhahir, Naofal - Department of Electrical Engineering, University of Texas at Dallas


Collections: Engineering