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Electronic Systems and Signals Research Laboratory
J. A. O'Sullivan Research Project SPASM

Signal Processing for Advanced Storage Media
We propose and study signal processing methods for information storage systems that have two-dimensional (2D) intersymbol interference (ISI) during read-back. The proposed methods iteratively perform equalization and decoding on the readback signal. We propose schemes that use existing equalization methids with error correction coding and also propose new methods based on message-passing for 2D ISI. Schemes using 2D minimum mean-squared error (MMSE) equalization is used in conjunction with low-density parity-check (LDPC) codes are proposed. Various MMSE-LDPC schemes that trade-off complexity for performance have been studied. These include MMSE filters that are spatially and temporally varying and approximations which are either spatially invariant or temporally invariant or both. Iterative schemes which perform message-passing on the joint graph of the ISI and the error correction code are also proposed. The presence of short cycles in the channel ISI graph motivated a modified message-passing scheme for the 2D ISI channel. Simulations (bit error rate vs SNR) demonstrate the potential of these schemes. The modified full graph message-passing scheme has the best performance among our schemes. The exact MMSE-LDPC scheme has very similar performance to the modified full graph message-passing scheme at a much lower complexity. Analytical methods, like extrinsic information transfer charts and density evolution, have been used to determine the theoretical performance limits of the schemes. Noise tolerance thresholds obtained using density evolution are used to study the trade-off between computational complexity and performance for the schemes. The schemes have been applied to the two-dimensional optical storage medium being developed by Philips research laboratories, Netherlands and simulations show marked improvement in performance over conventional methods.

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Related Talks

  • "Signal Processing for Advanced Storage Media," N. Singla, Oral Qualifying Exam, May 10, 2004. (pdf version)

  • "Iterative Decoding for 2D ISI Channels Using Message-Passing," Joseph A. O'Sullivan, Naveen Singla, Ronald S. Indeck, SIAM Conference on Imaging Science, Salt Lake City, Utah, May 5, 2004. (pdf version)

  • "2D Coding for Future Perpendicular and Probe Recording," Joseph A. O'Sullivan, Naveen Singla, Ronald S. Indeck, 2004. (pdf version)

  • "Ordered Subsets Message-Passing," Joseph A. O'Sullivan, Naveen Singla, International Symposium on Information Theory, Yokohama, Japan, July 3, 2003. (pdf version)

  • "Iterative Decoding and Equalization for Information Storage Systems with Two-Dimensional Intersymbol Interference," N. Singla, Master's Thesis, Washington University, St Louis, Missouri, April 2003. (pdf version)

  • "Joint Detection and Decoding Schemes for Two-Dimensional Data Storage Systems,'' Joseph A. O'Sullivan, Naveen Singla, University of Missouri at Rolla, February 24, 2003. (pdf version)

  • "Nanoimprint Lithography and Joint 2-D Detection and Decoding Schemes for Advanced Recording," N. Singla, Presented as part of the CCIS/IEEE Seminar series at Boulder, Colorado, December 2002. (pdf version)

  • "Joint Iterative Equalization and Decoding for 2-D ISI Channels," Joseph A. O'Sullivan, Naveen Singla, Yunxiang Wu, Ronald S. Indeck, July 2, 2002. (pdf version)

  • "Two-Dimensional Coding for Advanced Recording," N. Singla, Joseph A. O'Sullivan, Y. Wu, Ronald S. Indeck. (pdf version)

  • "Information Theoretic Imaging," J.A. O'Sullivan, Naveen Singla, James Meany. (pdf version)

  • "Signal Processing for Advanced Storage Media," Joseph A. O'Sullivan, Ronald S. Indeck, Naveen Singla. (pdf version)

  • "2D Coding and Iterative Detection Schemes," Joseph A. O'Sullivan, Naveen Singla, Yunxiang Wu, Ronald S. Indeck. (pdf version)

    Related Publications

    Y. Wu, J. A. O'Sullivan, N. Singla, and R. S. Indeck, ``Iterative Detection and Decoding for Separable Two-Dimensional Intersymbol Interference,'' IEEE Transactions on Magnetics, Vol. 39, No.4, pp. 2115-2120, July 2003. (pdf version of paper)

    N. Singla, J. A. O'Sullivan, R. S. Indeck, Y. Wu, ``Iterative decoding and equalization for 2-D recording channels,'' IEEE Transactions on Magnetics, Vol. 38 No. 5, pp. 2328-2330, September 2002. (pdf version of paper)

    J. A. O'Sullivan and N. Singla, ``Ordered Subsets Message-Passing,'' 2003 IEEE International Symposium on Information Theory, Yokohama, Japan, June 29-July 4, 2003. (pdf version of talk) (pdf version of paper)

    Naveen Singla and Joseph A. O'Sullivan, "Minimum mean square error equalization using priors for two-dimensional intersymbol interference," 2004 IEEE International Symposium on Information Theory, Chicago, Illinois, June 27-July 2, 2004. (pdf version of paper)

    Joseph A. O'Sullivan, Naveen Singla, Ronald S. Indeck, "2D Coding for Future Perpendicular and Probe Recording," 2004. (pdf version of paper) (pdf version of talk)

    J. A. O'Sullivan, L. Xu, and N. Singla, ``Coding for High-Density Storage Systems,'' 40th Annual Allerton Conference on Communication, Control, and Computing, October 2-4, 2002. (pdf version of paper) (pdf version of talk)

    J. A. O'Sullivan, N. Singla, Y. Wu, and R. S. Indeck, ``Iterative decoding for two-dimensional intersymbol interference channels,'' Proceedings 2002 IEEE International Symposium on Information Theory, p. 198, Lausanne, Switzerland, June-July, 2002. (pdf version of talk) (pdf version of paper)

    N. Singla, J. A. O'Sullivan, R. S. Indeck, Y. Wu, ``Iterative decoding and equalization for 2-D recording channels,'' 2002 IEEE International Magnetics Conference, Amsterdam, Netherlands, April-May 2002. (pdf version of paper) (pdf version of talk)

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    Edited June 23, 2004

    Washington University in St. Louis     School of Engineering     Deptartment of Electrical and Systems Engineering