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2006 Fiscal Year Final Research Report Summary

Asynchronous DS/CDMA systems employing spreading codes generated by chaos maps with Markovity

Research Project

Project/Area Number 15360206
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section一般
Research Field Communication/Network engineering
Research InstitutionKYUSHU UNIVERCITY

Principal Investigator

KOHDA Tohru  Kyushu University, Graduate School of Information Science and Electrical Engineering, Professor, 大学院システム情報科学研究院, 教授 (20038102)

Co-Investigator(Kenkyū-buntansha) OOHAMA Yasutada  The University of Tokushima, Faculty and School of Engineering, Professor, 工学部, 教授 (20243892)
JITSUMATSU Yutaka  Kyushu University, Graduate School of Information Science and Electrical Engineering, Associate Professor, 大学院システム情報科学研究院, 助教授 (60336063)
Project Period (FY) 2003 – 2006
KeywordsCDMA communication / spread spectrum codes / pseudorandom number generator / chip waveforms / Markov chain / pulse shaping filter / FIR filter / Welch bound
Research Abstract

In DS-CDMA communications, linear feedback shift register (LFSR) sequences, such as Gold and Kasami codes, are employed as spread spectrum (SS) codes. In mobile cellar systems, propagation delay is randomly spread for uplink channels and synchronization timing error cannot be eliminated. Hence, we have evaluated the chip-asynchronous systems. Our results are summarized as follows 1) Chip-asynchronous version of total square correlation (CA-TSC) was defined as the total value of all users' interference and its lower bound, named chip-asynchronous version of Welch bound, was presented. Mutual interference depends on spreading codes and chip waveforms. They are normally designed independently but joint optimization of them should give better performance. We relaxed the Nyquist condition, which guarantees zero inter symbol interference and is often assumed to be satisfied, to minimize total interference. We showed that the pair of Gaussian pulse and Markov codes give better performance than the conventional pair of raised cosine pulse and LFSR sequences, where both pulses are adjusted to have the same excess-band energies. 2) Based on a posteriori probability calculations, we proposed a new code acquisition algorithm. The proposed method, called "counting method", is very simple and effective; it counts only the number of events that receiver outputs exceed the pre-determined threshold and it realizes faster code acquisition than the serial search. More importantly, this method guarantees the maximum acquisition error rate. 3) Close relation between the associate memory model of neural networks and CDMA system is investigated. Associative memory corresponding to chip-asynchronous CDMA system was proposed, which was shown to memorize Markov patterns better than i.i.d. patterns

  • Research Products

    (12 results)

All 2007 2006 2005 2004 2003 Other

All Journal Article (12 results)

  • [Journal Article] Statistical solution to the capacity problem in Direct-Sequence Code-Division Multiple Access Communication Systems2007

    • Author(s)
      N.Eshima, T.Kohda, M.Tabata
    • Journal Title

      IMA Journal of Mathematical Control and Information (in press)

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Statistical Approach to the Code Acquisition Problem in Direct-Sequence Spread-Spectrum Communication Systems2006

    • Author(s)
      N.Eshima, T.Kohda
    • Journal Title

      IMA Journal of Mathematical Control and Information 23, 2

      Pages: 149-163

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Chip-Asynchronous Version of Welch Bound : Gaussian Pulse Improves BER Performance2006

    • Author(s)
      Yutaka Jitsumatsu, Tohru Kohda
    • Journal Title

      Sequences and Their Applications - SETA 2006 4086

      Pages: 351-363

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Statistical Approach to th Code Acquisition Problem in Direct-Sequenc Spread-Spectrum Communication Systems2006

    • Author(s)
      N.Eshima, T.Kohda
    • Journal Title

      IMA Journal of Mathematical Control and Information 23, 2

      Pages: 149-163

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Chip-Asynchronous Version of Welch Bound : Gaussian Pulse Improves BER Performance,2006

    • Author(s)
      Yutaka Jitsumatsu, Tohru Kohda
    • Journal Title

      Sequences and Their Applications-SETA 2006(Springer, Berlin/Heidelberg) vol.4086

      Pages: 351-363

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Code Acquisition in DS/CDMA Systems by Employing a Detector Based on a posteriori Probability Calculation2005

    • Author(s)
      Tahir, A.K., Eshima, N, Jitsumatsu, Y, Kohda, T
    • Journal Title

      IEICE Transactions on Communication E88-B,10

      Pages: 4047-4055

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Code Acquisition in DS/CDMA Systems by Employing a Detector Based on a posteriori Probability Calculation2005

    • Author(s)
      Tahir, A.K., Eshima, N, Jitsumatsu, Y, Kohda, T
    • Journal Title

      IEICE Transactions on Communication 88

      Pages: 4047-4055

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Reduction of MAI in Asynchronous DS/CDMA Systems Using Post-Filter2004

    • Author(s)
      Y.Jitsumatsu, T.A.Khan, T.Kohda
    • Journal Title

      IEICE Trans. on Fundamentals E87-A, 9

      Pages: 2301-2307

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Reduction of MAI in Asynchronous DS/CDMA Systems Using Post-Filter,2004

    • Author(s)
      Y.Jitsumatsu, T.A.Khan, T.Kohda
    • Journal Title

      IEICE Trans. on Fundamentals E87-A, no.9

      Pages: 2301-2307

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Pursley's aperiodic cross-correlation functions revisited2003

    • Author(s)
      T.Kohda, H.Fujisaki
    • Journal Title

      IEEE Transactions on Circuits and Systems I-Fundamental Theory and Applications 50, 6

      Pages: 800-805

    • Description
      「研究成果報告書概要(和文)」より
  • [Journal Article] Pursley's aperiodic cross-correlation functions revisited,2003

    • Author(s)
      T.Kohda, H.Fujisaki
    • Journal Title

      IEEE Transactions on Circuits and Systems I-Fundamental Theory and Applications 50(6)

      Pages: 800-805

    • Description
      「研究成果報告書概要(欧文)」より
  • [Journal Article] Statistical solution to the capacity problem in Direct-Sequence Code-Division Multiple Access Communication Systems

    • Author(s)
      N.Eshima, T.Kohda, M.Tabata
    • Journal Title

      IMA Journal of Mathematical Control and Information (published in Advance Access).

    • Description
      「研究成果報告書概要(欧文)」より

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Published: 2008-05-27  

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