Doctoral Dissertations


"Multiple-input multiple-output (MIMO) wireless communication systems have attracted a lot of interest in the past decade due to their capability in delivering high spectral efficiency as well as their robust performance against fading. In MIMO inter-symbol interference (lSI) channels, a severe interference problem occurs due to the lSI and co-channel interference. Thus, the error propagation problem becomes more serious, and its mitigation has to be considered when designing the receiver. In this regard, a turbo equalizer which exchanges soft information between the equalizer and the decoder has been shown to be an effective method to combat the lSI caused by frequency-selective channels. By iteratively exchanging soft extrinsic information between a soft-input soft-output equalizer and a decoder, turbo equalizer can achieve large performance gains over a separated equalizer and decoder structure. In its original form, Douillard employed maximum a posteriori probability (MAP) equalization and decoding methods in an iterative fashion. However, the computational complexity required to derive the a posteriori log likelihood ratio (LLR) for the MAP decoder is prohibitive. Therefore, the design of low-complexity turbo equalizers based on minimum mean square error (MMSE) criterion has attracted considerable attention in the past few years. In this work, a new soft decision feedback equalizer (SDFE) is proposed for MIMO Communication systems. The computational complexity of the proposed algorithm only linearly grows with the number of equalizer coefficients, compared with the quadratic complexity of minimum mean square error (MMSE)-based linear turbo equalizer with time-varying coefficients. The performance of our proposed algorithm is tested by extensive undersea trial data collected in two medium-range undersea experiments"--Abstract, page iv.


Xiao, Chengshan

Committee Member(s)

Zheng, Y. Rosa
Grant, Steven L.
Moss, Randy Hays, 1953-
Liu, Xiaoqing Frank


Electrical and Computer Engineering

Degree Name

Ph. D. in Electrical Engineering


Missouri University of Science and Technology

Publication Date

Fall 2012

Journal article titles appearing in thesis/dissertation

  • Low complexity soft-decision feedback turbo equalization for MIMO systems with multilevel modulations
  • Soft-decision feedback turbo equalization for LDPC-coded MIMO underwater acoustic communications
  • Soft feedback turbo equalization for underwater acoustic communications
  • Turbo equalization using reduced state map algorithm


xi, 101 pages

Note about bibliography

Includes bibliographical references.


© 2012 Amirhossein Rafati, All rights reserved.

Document Type

Dissertation - Restricted Access

File Type




Subject Headings

MIMO systems -- Design
Feedback control systems -- Design
Equalizers (Electronics) -- Mathematical models
Underwater acoustics

Thesis Number

T 10146

Print OCLC #


Electronic OCLC #


Link to Catalog Record

Electronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.

Share My Dissertation If you are the author of this work and would like to grant permission to make it openly accessible to all, please click the button above.