Dissertation
Signal detection on two-dimensional intersymbol interference channels: correlated sources and reduced complexity algorithms
Washington State University
Doctor of Philosophy (PhD), Washington State University
12/2008
DOI:
https://doi.org/10.7273/000005885
Abstract
In this dissertation, we present a novel iterative algorithm for detection of binary-valued
2D Markov Random Fields (MRFs) corrupted by 2D intersymbol interference (ISI) and
additive white Gaussian noise (AWGN). We assume a first-order binary MRF as a simple
model for correlated images. We also assume a 2D digital storage channel, where the MRF
is interleaved before being written and then read by a 2D transducer; such channels occur
in recently proposed optical disk storage systems. The detection algorithm is a concatenation
of two soft-input/soft-output (SISO) detectors: an iterative row-column soft-decision feedback (IRCSDF) ISI detector, and a MRF detector. For the 2 £ 2 averaging mask ISI channel, at a bit error rate (BER) of 10¡5, the concatenated algorithm achieves SNR savings up to 2.0 dB over the IRCSDF detector alone; the savings increase as the MRFs become more correlated, or as the SNR decreases. The algorithm is also fairly robust to mismatches between the assumed and actual MRF parameters. The complexity of Bahl-Cocke-Jelinek-Raviv (BCJR) algorithms grows exponentially with the size of the ISI mask and is an important concern with their implementation. We consider BCJR-like iterative detection algorithms for 1D and 2D binary-input ISI channels with AWGN. The proposed new technique reduces the complexity of BCJR algorithms by decreasing the effective number of states in the trellis. It does particularly well for
mixed phase sequence ISI masks, which have higher weights for the center taps and lower weights for the peripheral taps. Other complexity reduction techniques proposed in the literature perform poorly for such masks. Moreover, the complexity of the proposed state reduction technique is comparable to other reduced complexity techniques reported in the literature. Experimental results are provided to demonstrate the advantages of the proposed state reduction technique. This dissertation also addresses the problem of equivalent masks for 4-ary and binary
modulation at the same areal density. The ML bounds for these masks show that when the point spread function (PSF) is more spread, the performance of 4-ary modulation can be better than binary modulation on 2D ISI channels.
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Details
- Title
- Signal detection on two-dimensional intersymbol interference channels
- Creators
- Ying Zhu
- Contributors
- Benjamin Joseph Belzer (Chair) - Washington State University, School of Electrical Engineering and Computer ScienceKrishnamoorthy Sivakumar (Co-Chair) - Washington State University, Voiland College of Engineering and ArchitectureThomas Robert Fischer (Committee Member) - Washington State University, School of Electrical Engineering and Computer Science
- Awarding Institution
- Washington State University
- Academic Unit
- School of Electrical Engineering and Computer Science
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 103
- Identifiers
- 99901055139301842
- Language
- English
- Resource Type
- Dissertation