くりけん発表論文等

• Y. Kurihara, Y. Takeda, Y. Takaishi, Y. Koizumi, H. Osawa, M.Z. Ahmed, and Y. Okamoto, ``Constructive ITI coded PRML system based on two track model for perpendicular magnetic recording,'' Journal of Magnetism and Magnetic Materials, vol.320, no.22, pp.3140-3143, Nov. 2008.
  [doi : 10.1016/j.jmmm.2008.08.026]

  In this paper, we study not only the new constructive inter-track interference (CITI) code based on the equalized level but also Viterbi detection algorithm taking account of the ITI from adjacent tracks for the perpendicular magnetic recording channel without a differentiator of two track model. Although the investigation of this paper was not practical but theoretical, the result shows that the permissible percentage of ITI for conventional Viterbi detection to attain better performance compared with the case of single track is 26%, while the percentage for proposed one is improved up to 50%. Further investigation has to be required under a more realistic system and moreover may be expanded into patterned media perpendicular magnetic recording.

• P. SHAH, M.Z. AHMED, and Y. KURIHARA, New Method for Generalised PR Target Design for Perpendicular Magnetic Recording, Digest of PMRC 2007, The Eightth Perpendicular Magnetic Recording Conference, Tokyo, Japan, 16pD-01, pp.248-249, Oct. 2007.
• Y. KURIHARA, Y. TAKEDA, Y. TAKAISHI, Y. KOIZUMI, H. OSAWA, M.Z. AHMED, and Y. OKAMOTO, Constructive ITI Coded PRML System Based on Two Track Model for Perpendicular Magnetic Recording, Digest of PMRC 2007, The 8th Perpendicular Magnetic Recording Conference, Tokyo, Japan, 16pD-06, pp.258-259, Oct. 2007.
• Y. Kurihara, M.Z. Ahmed, H. Osawa, Y. Okamoto, `` CITI code based on PR1 equalized level for perpendicular recording[link],'' International Magnetics Conference, 2005 (Intermag Asia 2005), Nagoya, Japan, EP-02, Digests of the IEEE International Conference, 2005: Intermag Asia 2005., p.490(979-980), 4-8 April 2005.
  [doi : 10.1109/INTMAG.2005.1463918]

  In high density perpendicular recording the reduction techniques of the inter-track interference is important. In this paper, we investigate a new CITI code based on the equalized level of class-1 partial response (PR1), which is the simplest PR system whose polynomial is represented by only positive coefficients. The constructive inter-track interference code for the PR1 equalization in perpendicular recording was discussed. The results show that the proposed system exhibits better BER performance than the conventional one.

• Mohammed Zaki Ahmed, Paul J. Davey, and Yoshitake Kurihara, `` Constructive inter-track interference (CITI) codes for perpendicular magnetic recording,'' J. Magnetism and Magnetic Materials, vol.287, pp.432-436, Feb. 2005.
  [doi : 10.1016/j.jmmm.2004.10.072], [link from harvard.edu ハーバード大学サイト], [link from CAT.INIST.fr (フランス)],

  This paper presents new modulation codes to reduce the effect of adjacent track interference (ATI) also known as inter-track interference (ITI). New modulation codes, that is constructive inter-track interference (CITI) codes and partial response (PR) targets, are investigated using computer simulation in perpendicular magnetic channel. CITI codes have been found to increase the resilience of the perpendicular magnetic channel in the presence of ITI and jitter with no increased decoding complexity.

• Constructive Inter-Track Interference (CITI) Codes for Perpendicular Magnetic Recording, 7th Perpendicular Magnetic Recording Conference (PMRC 2004), 02pA-01, p.35 (booklet), pp.235-236 (Digest of PMRC 2004), Jun. 2004.
• H. Osawa, Y. Kurihara, Y. Okamoto, H. Muraoka, and Y. Nakamura, `` PRML Systems for Perpendicular Magnetic Recording,'' Journal of Magnetics Society of Japan, vol.21, no.S2, pp.399-405, Oct. 1997.
  [doi : 10.3379/jmsjmag.21.S2_399], [pdf]

  Partial response maximum-likelihood(PRML) systems using an MR head and a double layer perpendicular medium are studied. The bit-error rate performance of PRML systems characterized by the polynomials with the positive coefficients for the (1,7) code and the negative coefficients for the 8/9 code is evaluated. The PRML system for the (1,7) code has a large minimum Euclidean distance and a small noise spectrum compared with those for the 8/9 code. This results in a significant performance improvement. Among PRML systems discussed in this study, PR(1, 2, 3, 2, 1)ML exhibits the best performance and improves the SNR by about 13.8 dB over that of PR4ML for the 8/9 code at a bit-error rate of 10−4 and a normalized linear density of 2.5. PR(1, 2, 2, 1)ML, PR(1, 3, 3, 1)ML and PR(1, 2, 1)ML also show excellent performance.

• 栗原義武，大沢寿，岡本好弘，村岡裕明，中村慶久， ``複合膜主磁極型単磁極ヘッドによる各種PRML方式のSN比'', 日本応用磁気学会誌, vol.19, no.S2, pp.87-91, Oct. 1995. [doi: 10.3379/jmsjmag.19.S2_87] [joi: JST.JSTAGE/jmsjmag/19.S2_87]
• 大沢寿，栗原義武，岡本好弘，西田靖孝，村岡裕明，中村慶久， `` 垂直記録におけるパーシャルレスポンス方式の誤り率特性''[link], 信学論(C-II), vol.J77-C-II, no.4, pp.190-196, Apr. 1994. from Inter Science , CiNii

  複合膜主磁極形単磁極ヘッドを用いた垂直記録において， パーシャルレスポンス（PR）方式と最ゆう復号法の一種であるビタビ復号法とを 組み合せたPRML（Partial Response Maximum-Likelihood）方式の 誤り率特性について検討している． その際，実験により得られた孤立再生波形に対して波形近似を行い， これをもとにしてシミュレーションにより誤り率を求めている． まず，等化による雑音増大を考慮に入れて，複合膜主磁極形単磁極ヘッドの特性を 利用したいくつかの PR方式の識別点SN比とビットごとの復号法の誤り率を求めている． 次いで，これらのPR方式に対するPRML方式の誤り率を求め， 従来のPR方式の場合と比較検討している． そして，それらPR方式のうちで最良の特性が得られるのは PR（1,0,0,0,-1）方式 であり，10^-4の誤り率において， 従来のPR方式の場合に比べビットごとの復号法の場合で約1.9dB， PRML方式の場合で約4.1dBのSN比改善が得られることを明らかにしている．

• 大沢寿，栗原義武，岡本好弘，西田靖孝，中村慶久， `` 垂直記録におけるPRML方式の検討 [link],'' テレビ学技報, vol.16, no.72, pp.37-42, (19921112).
• H. Osawa, Y. Okamoto, Y. Kurihara, Y. Nishida, Y. Nakamura, `` Performance of partial response system in perpendicular magnetic recording [link],'' Electronics and Communications in Japan (Part II: Electronics), vol.77, no.8, pp.73-81, Aug. 1994.
• Y. Kurihara, H. Osawa, Y. Okamoto, `` Simplification of Viterbi Algorithm for (1,7) RLL,'' IEICE Trans. Electron. vol.E78-C, no.11, pp.1567-1574, Nov. 1995.
  [CiNii], [link from IEICE ]

  Simplification of the Viterbi algorithm and the error rate performance are presented for a partial response maximum-likelihood (PRML) system employing the PR(1, 1) system as a PR system for (1, 7) run-length limited (RLL) code. The minimum run-length of 1's or O's in the output sequence of the precoder for (1, 7) RLL code is limited to 2. Two kinds of simplified Viterbi algorithms using this run-length constraint are proposed. One algorithm requires the path memory length of only two in the Viterbi detector. The Viterbi detector based on the other algorithm is equivalent to the simple PR(1, 1) system followed by a threshold detector. The bit-error rates of PRML systems with Viterbi detectors based on these algorithms are obtained by computer simulation and their performance is compared with that of conventional PRML systems for (1, 7) RLL code. It is shown that the proposed PRML system exhibits better performance than conventional PRML systems at high recording density.

• 栗原義武，小泉祐貴，M.Z. Ahmed, 高石雅章，安藤毅， 大沢寿，岡本好弘， ``垂直磁気記録へのCITI符号の適用[link],'' 新居浜高専紀要, vol.41, pp.51-58, Jan. 2005. [pdf]

  An Application of Constructive Inter-Track Interference (CITI) code to double layer perpendicular magnetic recording is studied for two-track Class I partial response maximum likelihood (PR1ML) system. This computer simulation exploys a hyperbolic tangent function to present an isolated reproducing waveform for each recorded transiton. As a result, it is shown that the two-track PR1ML system with CITI code can mitigate the effect of ITI better than that without CITI code.

• 栗原義武，大沢寿，小西是史，岡本好弘，斎藤秀俊， `` ラン長制約符号に対するビタビ復号法の簡単化 '' 新居浜高専紀要，第36巻, pp.49-, Jan. 2000.

  Yoshitake KURIHARA, Hisashi OSAWA, Yoshifumi KONISHI, Yoshihiro OKAMOTO and Hidetoshi SAITO, `` Simplification of Viterbi Detection for Run-Length Limited code ,'' MEMOIRS OF NIIHAMA NATIONAL COLLEGE OF TECHNOLOGY, vol.36, pp.49-, Jan. 2000. from Science Links Japan[link]

• Y.Kurihara, H. Osawa, Y. Okamoto, H. Muraoka, and Y. Nakamura, `` Performance of PRML systems in perpendicular magnetic recording by a bi-layered main-pole head[link],'' Journal of Magnetism and Magnetic Materials, vol.157/158, pp.262-263, May 1996.

  For perpendicular magnetic recording by a bi-layered main-pole head which shows an excellent linearity, the performance of PRML system combining partial respons e (PR) system with maximum likelihood (ML) decoding is studied. The bit-error ra te of the PRML system using a PR(1,1,0,0,0,0, − 1, − 1) system is obtained by computer simulation and compared with that of the conventional PRML system. It i s shown that our PRML system exhibits better performance than the conventional P RML system in high density recording.

• 栗原義武，大沢寿，岡本好弘，村岡裕明，中村慶久， `` 垂直磁気記録におけるPRML方式のSN比と誤り率特性 '' 新居浜高専紀要，vol.33, pp.80-, Jan. 1997.
• 栗原義武，大沢寿，岡本好弘，村岡裕明，中村慶久， `` 垂直磁気記録におけるパーシャルレスポンス方式とビタビ復号法 '' 新居浜高専紀要(理工)，vol.31, pp.68-75, Jan. 1995.

その他