Title page for ETD etd-01272000-14010017


Type of Document Master's Thesis
Author Roy, Pulakesh
Author's Email Address proy@vt.edu
URN etd-01272000-14010017
Title Fractionally Spaced Blind Equalizer Performance Improvement
Degree Master of Science
Department Electrical and Computer Engineering
Advisory Committee
Advisor Name Title
Beex, A. A. Louis Committee Chair
Moose, Richard L. Committee Member
Woerner, Brian D. Committee Member
Keywords
  • Blind Equalization
  • Fractionally Spaced Equalizer
  • Recursive Linear Predictor
  • Performance Improvement
Date of Defense 2000-01-17
Availability unrestricted
Abstract
Blind equalization schemes are used to cancel the effects of a channel on the received signal when the transmission of a training sequence in a predefined time slot is not possible. In the absence of a training sequence, blind equalization schemes can also increase the throughput of the overall system. A general problem with blind adaptation techniques is that they have poor convergence properties compared to the traditional techniques using training sequences. Having a multi-modal cost surface, blind adaptation techniques may force the equalizer to converge to a false minimum, depending on the initialization. The most commonly used blind adaptation algorithm is the Constant Modulus Algorithm (CMA). It is shown by simulation that a logarithmic error equation can make CMA converge to a global minimum, if a differential encoding scheme is used. The performance of CMA with different error equations is also investigated for different channel conditions.

For a time varying channel, the performance of an equalizer not only depends on the convergence behavior but also on the tracking property, which indicates the ability of an equalizer to track changes in the channel. The tracking property of a blind equalizer with CMA has been investigated under different channel conditions. It is also shown that the tracking property of a blind equalizer can be improved by using a recursive linear predictor at the output of the equalizer to predict the amplitude of the equalizer output. The predicted value of the amplitude is then used to adjust the instantaneous gain of the overall system.

A recursive linear predictor is designed to predict a colored signal without having a priori knowledge about the correlation function of the input sequence. The performance of the designed predictor is also investigated by predicting the envelope of a flat fading channel under constant mobile velocity and constant acceleration conditions.

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  abstruct.pdf 5.16 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01
  acknowledgment.pdf 4.01 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01
  Appendix.pdf 60.75 Kb 00:00:16 00:00:08 00:00:07 00:00:03 < 00:00:01
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  Biography.pdf 5.10 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01
  chapter1.pdf 13.61 Kb 00:00:03 00:00:01 00:00:01 < 00:00:01 < 00:00:01
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  chapter5.pdf 270.90 Kb 00:01:15 00:00:38 00:00:33 00:00:16 00:00:01
  chapter6.pdf 11.86 Kb 00:00:03 00:00:01 00:00:01 < 00:00:01 < 00:00:01
  coverpage.pdf 3.76 Kb 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01 < 00:00:01
  listoffigures.pdf 9.16 Kb 00:00:02 00:00:01 00:00:01 < 00:00:01 < 00:00:01
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  tableofcontents.pdf 10.04 Kb 00:00:02 00:00:01 00:00:01 < 00:00:01 < 00:00:01

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