Abstract
This paper describes the limiting behavior of linear and decision feedback equalizers (DFEs) in single/multiple antenna systems employing real/complex-valued modulation alphabets. The wideband frequency-selective channel is modeled using a Rayleigh fading channel model with infinite number of time domain channel taps. Using this model, we show that the considered equalizers offer a fixed post detection signal-to-noise ratio (post-SNR) at the equalizer output that is close to the matched filter bound (MFB). General expressions for the post-SNR are obtained for zero-forcing (ZF)-based conventional receivers as well as for the case of receivers employing widely linear (WL) processing. Simulation is used to study the bit error rate (BER) performance of both minimum-mean-square-error (MMSE) and ZF-based receivers. Results show that the considered receivers advantageously exploit the rich frequency-selective channel to mitigate both fading and inter-symbol interference (ISI) while offering a performance comparable to the MFB.
Highlights
Linear and decision feedback equalizers (DFEs) have been widely studied for the past 50 years
The results show that when the ZF-DFE is initialized using known data, the bit error rate (BER) follows the ideal DFE case while initialization using the zero-forcing linear equalizer (ZF-LE) leads to an error floor
Unlike the ZF case, initialization of the minimum mean-square error (MMSE)-DFE using MMSE-LE does not cause severe error propagation and the BER is within 2.0 dB of ideal MMSE-DFE
Summary
Linear and decision feedback equalizers (DFEs) have been widely studied for the past 50 years. In broadband wireless systems employing high bandwidths, the propagation channel typically exhibits high frequency selectivity. For these systems, link performance measures such as the diversity order and bit error rate (BER) of a conventional minimum mean-square error (MMSE)-based linear equalizers have not yet been fully characterized [4,5,6,7,8,9]. The minimum mean-square error decision feedback equalizer (MMSEDFE) [10,11], on the other hand, is an optimum canonical receiver for channels with ISI. Most of the prior works related to linear and decision feedback equalizers discuss the diversity order of the equalizers and do not quantify the exact performance of the equalizer. Simulation is typically used to determine the link performance
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