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[Author] Hisakazu KIKUCHI(54hit)

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  • Edge-Based Image Synthesis Model and Its Synthesis Function Design by the Wavelet Transform

    Makoto NAKASHIZUKA  Hidetoshi OKAZAKI  Hisakazu KIKUCHI  

     
    PAPER-Digital Signal Processing

      Vol:
    E85-A No:1
      Page(s):
    210-221

    In this paper, a new image synthesis model based on a set of wavelet bases is proposed. In the proposed model, images are approximated by the sum of synthesis functions that are translated to image edge positions. By applying the proposed model to sketch-based image coding, no iterative image recovery procedure is required for image decoding. In the design of the synthesis functions, we define the synthesis functions as a linear combination of wavelet bases. The coefficients for wavelet bases are obtained from an iterative procedure. The vector quantization is applied to the vectors of the coefficients to limit the number of the synthesis functions. We apply the proposed synthesis model to the sketch-based image coding. Image coding experiments by eight synthesis functions and a comparison with the orthogonal transform methods are also given.

  • Iterative Design of Constrained IIR Digital Filters Requiring No Initial Values

    Hisakazu KIKUCHI  Hiromichi WATANABE  Takeshi YANAGISAWA  

     
    PAPER-Circuit Theory

      Vol:
    E69-E No:5
      Page(s):
    601-609

    An iterative design of constrained recursive digital filters is developed. The designing scheme requires no initial values. The constraints are subjected to degrees of both numerator and denominator, transmission zeros and poles, if any, and passband and stopband shaping. The resulting filter completes a prescribed magnitude of either passband or stopband ripples. The optimality property of the filters is examined in detail with emphasis on specifications. The designing scheme involves the elliptic design as a special case. Illustrative examples are also given.

  • Interpolated FIR Filters Based on the Cyclotomic Polynomials

    Hisakazu KIKUCHI  Yoshito ABE  Hiromichi WATANABE  Takeshi YANAGISAWA  

     
    PAPER-Digital Signal Processing

      Vol:
    E70-E No:10
      Page(s):
    928-937

    Based on the cyclotomic polynomials, this paper describes a family of efficient and practical interpolators for interpolated FIR filters. The family can be applied to bandpass filters as well as lowpass/highpass filters without any multiplications. It also mitigates the inconvenience to select a practical interpolation factor, and gains a further saving in computational complexity required. Several examples are given to demonstrate the effectiveness for reducing the computational complexity required.

  • Impact of Chip Duty Factor in DS-UWB Systems over Indoor Multipath Environment

    Chin Sean SUM  Shigenobu SASAKI  Hisakazu KIKUCHI  

     
    LETTER

      Vol:
    E89-A No:11
      Page(s):
    3152-3156

    This paper investigates the impact of chip duty factor (DF) in DS-UWB system with Rake receiver over AWGN and UWB indoor multipath environment corresponding to system parameters such as spreading bandwidth and chip length. Manipulating DF in DS-UWB system offers several advantages over multipath channel and thus, capable of improving system performance for better quality of communication. Although employing lower DF generally improves performance, in some exceptional cases on the other hand, degradation can be observed despite decreasing DF. Therefore, the objective of this paper is to clarify the relationship between DF and DS-UWB system performance. We discovered that with constant processing gain and spreading bandwidth, performance improvement can be observed at DF lower than 0.17. Additionally, with spreading bandwidth as tradeoff parameter, significant performance improvement can only be observed below DF of 0.85.

  • FOREWORD

    Hisakazu KIKUCHI  

     
    FOREWORD

      Vol:
    E82-A No:8
      Page(s):
    1385-1385
  • A Simple Exact Error Rate Analysis for DS-CDMA with Arbitrary Pulse Shape in Flat Nakagami Fading

    Mohammad Azizur RAHMAN  Shigenobu SASAKI  Hisakazu KIKUCHI  Hiroshi HARADA  Shuzo KATO  

     
    LETTER

      Vol:
    E92-B No:5
      Page(s):
    1808-1812

    A simple exact error rate analysis is presented for random binary direct sequence code division multiple access (DS-CDMA) considering a general pulse shape and flat Nakagami fading channel. First of all, a simple model is developed for the multiple access interference (MAI). Based on this, a simple exact expression of the characteristic function (CF) of MAI is developed in a straight forward manner. Finally, an exact expression of error rate is obtained following the CF method of error rate analysis. The exact error rate so obtained can be much easily evaluated as compared to the only reliable approximate error rate expression currently available, which is based on the Improved Gaussian Approximation (IGA).

  • Equivalent Parallel Structure of Deinterlacer Banks and Its Application to Optimal Bit-Rate Allocation

    Minoru HIKI  Shogo MURAMATSU  Takuma ISHIDA  Hisakazu KIKUCHI  

     
    PAPER-Digital Signal Processing

      Vol:
    E90-A No:3
      Page(s):
    642-650

    In this paper, theoretical properties of deinterlacer banks are analyzed. Deinterlacer banks are novel filter banks in the sense that a progressive video sequence is separated into two progressive video sequences of a half frame rate and, furthermore, interlaced sequences are produced as intermediate data. Unlike the conventional filter banks, our deinterlacer banks are constructed in a way unique to multidimensional systems by using invertible deinterlacers, which the authors have proposed before. The system is a kind of shift-varying filter banks and it was impossible to derive the optimal bit-allocation control without any equivalent parallel filter banks. This paper derives an equivalent polyphase matrix representation of the whole system and its equivalent parallel structure, and then shows the optimal rate allocation for the deinterlacer banks. Some experimental results justify the effectiveness of the optimal rate allocation through our theoretical analysis.

  • Error Rate Analysis of Coherent and Differential Multiphase Parallel Combinatorial Spread Spectrum Systems

    Shigenobu SASAKI  Hisakazu KIKUCHI  Jinkang ZHU  Gen MARUBAYASHI  

     
    PAPER

      Vol:
    E80-A No:7
      Page(s):
    1196-1203

    This paper investigates the error rate performance of parallel combinatorial spread spectrum (PC/SS) communicaion systems that use coherent and differential multiphase modulation: multiphase parallel combinatorial spread spectrum (MPC/SS) communication systems. The PC/SS systems are multicode SS systems based on orthogonal pseudo-noise (PN) sequences. Data is transmitted by delivering a combination of multiple PN sequences among a set of pre-assigned PN sequences. In the MPC/SS systems, every PN sequence on transmission is modulated by q-ary coherent or differential phase shift keying (PSK). Symbol error rate (SER) and average bit error rate (BER) in coherent and differential MPC/SS systems are investigated. The BER comparison between the MPC/SS systems and simple multicode SS systems with q-ary coherent and differential PSK is also presented. Numerical results show that the MPC/SS systems are superior to the conventional q-ary PSK systems, if they have equal spectral efficiency.

  • Reversible Implementations of Irreversible Component Transforms and Their Comparisons in Image Compression

    Junghyeun HWANG  Hisakazu KIKUCHI  Shogo MURAMATSU  Kazuma SHINODA  Jaeho SHIN  

     
    LETTER-Digital Signal Processing

      Vol:
    E95-A No:4
      Page(s):
    824-828

    Reversible color component transforms derived by the LU factorization are briefly described. It is possible to obtain an reversible implementation to a given component transform, even if the original transform is irreversible. Some examples are presented and their performances are compared in image compression.

  • Performance Investigation of Two Transmit Diversity Schemes with Perfect/Imperfect Channel Evaluation in Wireless Communications

    Jie ZHOU  Hisakazu KIKUCHI  Shigenobu SASAKI  Shogo MURAMATSU  Yoshikuni ONOZATO  

     
    PAPER

      Vol:
    E85-B No:10
      Page(s):
    1957-1965

    Transmit diversity, a key technique derived against multi-path mitigation in wireless communication system, is examined and discussed. Especially, we present an approach to investigate perfect/imperfect channel detection when the maximal ratio receiver combined scheme (MRRC) and a simple transmit diversity scheme (STD) are used in the wireless systems, which provide remarkable schemes for diversity transmission over Rayleigh-fading channels using multiple antennas. In order to effectively make use of the transmit diversity techniques, the same approach is extended to process the situation of one transmit antennas and N receive antennas in MRRC scheme (1 N MRRC) and two transmit antennas and N receive antennas in STD scheme (2 N STD). The effects of perfect/imperfect channel detection and the diversity reception with independent and correlated Rayleigh-fading signals are evaluated and compared carefully.

  • Efficient Prefiltering for FIR Digital Filters

    Hisakazu KIKUCHI  Yoshito ABE  Hiromichi WATANABE  Takeshi YANAGISAWA  

     
    PAPER-Digital Signal Processing

      Vol:
    E70-E No:10
      Page(s):
    918-927

    This paper presents three types of prefiltering for FIR digital filters to decrease the number of multipliers required. The first type is based on cyclotomic polynomials. It can be applied to any types of band-selective filters. The second is a mirror-image quadratic polynomial to make a passband shaping. Both types of the prefilters are used with the interpolation technique, and this improves each primitive characteristic in terms of the sharp transition. In the prefilter-equalizer design approach, these prefilterings bring about the reduction of the number of multipliers required in hardware implementation. The prefiltering efficiency is demonstrated by a few examples.

  • ECG Data Compression by Matching Pursuits with Multiscale Atoms

    Makoto NAKASHIZUKA  Kazuki NIWA  Hisakazu KIKUCHI  

     
    PAPER-Biomedical Signal Processing

      Vol:
    E84-A No:8
      Page(s):
    1919-1932

    In this paper, we propose an ECG waveform compression technique based on the matching pursuit. The matching pursuit is an iterative non-orthogonal signal expansion technique. A signal is decomposed to atoms in a function dictionary. The constraint to the dictionary is only the over-completeness to signals. The function dictionary can be defined to be best match to the structure of the ECG waveform. In this paper, we introduce the multiscale analysis to the implementation of inner product computations between signals and atoms in the matching pursuit iteration. The computational cost can be reduced by utilization of the filter bank of the multiscale analysis. We show the waveform approximation capability of the matching pursuit with multiscale analysis. We show that a simple 4-tap integer filter bank is enough to the approximation and compression of ECG waveforms. In ECG waveform compression, we apply the error feed-back procedure to the matching pursuit iteration to reduce the norm of the approximation error. Finally, actual ECG waveform compression by the proposed method are demonstrated. The proposed method achieve the compression by the factor 10 to 30. The compression ratio given by the proposed method is higher than the orthogonal wavelet transform coding in the range of the reconstruction precision lower than 9% in PRD.

  • Image Contour Clustering by Vector Quantization on Multiscale Gradient Planes and Its Application to Image Coding

    Makoto NAKASHIZUKA  Yuji HIURA  Hisakazu KIKUCHI  Ikuo ISHII  

     
    PAPER

      Vol:
    E81-A No:8
      Page(s):
    1652-1660

    We introduce an image contour clustering method based on a multiscale image representation and its application to image compression. Multiscale gradient planes are obtained from the mean squared sum of 2D wavelet transform of an image. The decay on the multiscale gradient planes across scales depends on the Lipshitz exponent. Since the Lipshitz exponent indicates the spatial differentiability of an image, the multiscale gradient planes represent smoothness or sharpness around edges on image contours. We apply vector quatization to the multiscale gradient planes at contours, and cluster the contours in terms of represntative vectors in VQ. Since the multiscale gradient planes indicate the Lipshitz exponents, the image contours are clustered according to its gradients and Lipshitz exponents. Moreover, we present an image recovery algorithm to the multiscale gradient planes, and we achieve the skech-based image compression by the vector quantization on the multiscale gradient planes.

  • FOREWORD

    Hisakazu KIKUCHI  Masakazu SENGOKU  

     
    FOREWORD

      Vol:
    E80-A No:3
      Page(s):
    439-440
41-54hit(54hit)