Shuichi Ohno | Hiroshima University (original) (raw)

Papers by Shuichi Ohno

EURASIP Journal on Advances in Signal Processing, Feb 29, 2016

Optimal finite impulse response (FIR) error feedback filters for noise shaping in modulators are ... more Optimal finite impulse response (FIR) error feedback filters for noise shaping in modulators are designed by using weighting functions based on the system norms. We minimize the weighted norms of the quantization error in the output of a modulator, which corresponds to the minimization of the system norm. Three norms, the H 2 system norm, the H ∞ system norm, and the l 1 norm of the impulse response of the system, are adopted. The optimization problem for three types of FIR filters are evaluated by using linear matrix inequalities (LMIs) and then solved numerically via semi-definite programming. Design examples are provided to demonstrate the effectiveness of our proposed methods.

EURASIP Journal on Advances in Signal Processing, Feb 17, 2017

Standardized wireless transmissions include fixed-size fragments per packet. Relying on this stru... more Standardized wireless transmissions include fixed-size fragments per packet. Relying on this structure, two schemes for distributing redundancy across fragments are considered in this paper to enable blind identification without higher-order statistics of received signals. We prove that both schemes guarantee blind identifiability as well as symbol detectability and propose a subspace based blind identification method. We test their relative merits, and compare them with existing alternatives using simulations.

Proceedings of the ISCIE International Symposium on Stochastic Systems Theory and its Applications, 2015

In this paper, a demand side management (DSM) technique for minimizing the peak load of the elect... more In this paper, a demand side management (DSM) technique for minimizing the peak load of the electric grid is proposed. The grid optimization problem is formulated and analyzed to find the optimized strategies. A smart power system with multi-residential end-users connected to a single energy source is considered. The end-users attempt to minimize peak-to-average ratio (PAR) of the electric grid by using energy scheduler (ES) as well as their energy production and storage strategies. Some end-users posses renewable energy sources (RESs), distribution generators (DGs), storage devices or both. Users charge their storage devices at low-demand periods and discharge them at high-demand periods. Likewise, end-users produces electricity during the peak hours to minimize their energy cost.

Asia-Pacific Signal and Information Processing Association Annual Summit and Conference, Dec 1, 2012

In this paper, preamble design for estimation of frequency selective channels and In-phase/Quadra... more In this paper, preamble design for estimation of frequency selective channels and In-phase/Quadrature-phase (I/Q) imbalance in multiple input multiple output orthogonal frequency division multiplexing (MIMO-OFDM) systems is proposed. First we utilize convex optimization to optimize power of all active subcarriers, then we employ cross entropy (CE) optimization techniques to select optimal preamble sequence that minimizes the channel estimate mean squared error (MSE) while suppressing the effect of I/Q mismatch. To mitigate interantenna interferences, disjoint preamble sequences are utilized for each transmit antenna. An algorithm to guarantee that the preamble sequences are disjoint for each transmitter is proposed. Numerical simulations are provided to verify the advantages and effectiveness of the proposed preamble sequences over the conventional sequences.

Proceedings of International Conference on Artificial Life and Robotics, 2018

Proportional-integral-derivative (PID) controllers have been widely used for process systems. How... more Proportional-integral-derivative (PID) controllers have been widely used for process systems. However, a good control result is not always obtained with fixed PID gains when a controlled object has nonlinearity. This paper proposes a design method for a nonlinear PID controller that utilizes a neural network to overcome the problem. In the proposed controller, PID gains are tuned online by a neural network and a controlled object is manipulated by the PID controller with the tuned PID gains. The neural network is learned by an offline learning algorithm based on the Extended Fictitious Reference Iterative Tuning (E-FRIT) and the backpropagation. E-FRIT is a method that tunes control parameters directly by using operating data and evaluates not only a controlled output but also the difference of manipulated variable. Simulation examples are provided to show the effectiveness of the proposed method. Moreover, the experimental result of a level control of a tank system is also given to demonstrate the performance of the proposed method.

ArXiv, 2017

In a networked control system, quantization is inevitable to transmit control and measurement sig... more In a networked control system, quantization is inevitable to transmit control and measurement signals. While uniform quantizers are often used in practical systems, the overloading, which is due to the limitation on the number of bits in the quantizer, may significantly degrade the control performance. In this paper, we design an overloading-free feedback quantizer based on a Delta-Sigma modulator,composed of an error feedback filter and a static quantizer. To guarantee no-overloading in the quantizer, we impose an linftyl_{\infty}linfty norm constraint on the feedback signal in the quantizer. Then, for a prescribed linftyl_{\infty}linfty norm constraint on the error at the system output induced by the quantizer, we design the error feedback filter that requires the minimum number of bits that achieves the constraint. Next, for a fixed number of bits for the quantizer, we investigate the achievable minimum linftyl_{\infty}linfty norm of the error at the system output with an overloading-free quantizer. Numerical...

Proceedings of the 1998 IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP '98 (Cat. No.98CH36181)

In order to attain multichannel blind deconvolution of linear time-invariant nonminimum-phase dyn... more In order to attain multichannel blind deconvolution of linear time-invariant nonminimum-phase dynamic systems, Inouye and Habe proposed in 1995 a single-stage maximization criterion. The criterion function is the sum of squared forthorder cumulants of the equalizer outputs, and the coefficients of the equalizer are determined at once. On the other hand, one of possible approaches for multichannel blind deconvolution is to construct an equalizer based on the system identified by higher-order cumulant-matching. In this paper, it is shown that the single-stage maximization criterion is equivalent to a least-squares fourth-order cumulantmatching criterion after multichannel pre-whitening of channel outputs. This result provides us with an important interpretation of the single-stage maximization criterion.

2011 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), 2011

We develop a closed-form approximation algorithm for designing IIR digital filters with linear ph... more We develop a closed-form approximation algorithm for designing IIR digital filters with linear phase and guaranteed stability. In this algorithm, the stopband and passband edge frequency can be specified in the frequency domain and the filter coefficients can be easily obtained for approximating the given frequency response. Additionally, there is a property that the maximum of absolute values of all poles can be controlled, so we can avoid the risk that the designed filters under finite word-length effects become unstable. Finally, a numerical example is given to illustrate the utility of the proposed method.

Transactions of the Institute of Systems, Control and Information Engineers, 1994

IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, 2011

For copyright protection, a watermark signal is embedded in host images with a secret key, and a ... more For copyright protection, a watermark signal is embedded in host images with a secret key, and a correlation is applied to judge the presence of watermark signal in the watermark detection. This paper treats a discrete wavelet transform (DWT)-based image watermarking method under specified false positive probability. We propose a new watermarking method to improve the detection performance by using not only positive correlation but also negative correlation. Also we present a statistical analysis for the detection performance with taking into account the false positive probability and prove the effectiveness of the proposed method. By using some experimental results, we verify the statistical analysis and show this method serves to improve the robustness against some attacks.

Digital Signal Processing, 2010

We study the problem of estimating the impulse responses of multiple FIR channels driven by an un... more We study the problem of estimating the impulse responses of multiple FIR channels driven by an unknown impulsive signal. A deterministic method which deals with arbitrarily short excitation signals is proposed by utilizing subspace properties of the data covariance matrix. A variant of the proposed method is also presented which exploits the L 1-norm convex optimization to improve the estimation accuracy when the impulse responses of the system to be identified are sparse. The proposed methods have the potential to improve the performances of communication, exploration seismology and mechanical signature analysis systems.

9th European Signal Processing Conference (EUSIPCO 1998), 1998

We give an algorithm for the single-stage maximization criterion to attain multichannel blind dec... more We give an algorithm for the single-stage maximization criterion to attain multichannel blind deconvolution. This criterion determines the coefficients of equalizers for all channels simultaneously. However, the original maximization criterion has many constrains so that it is difficult to directly implement it as a numerical algorithm. By exploiting pre-whitening and lattice representations of paraunitary systems, we can reduce the original maximization problem into a simple constraint-free one and then present a stochastic gradient algorithm.

Proceedings of the ISCIE International Symposium on Stochastic Systems Theory and its Applications, 1999

2003 IEEE International Conference on Acoustics, Speech, and Signal Processing, 2003. Proceedings. (ICASSP '03).

Publication in the conference proceedings of EUSIPCO, Aalborg, Denmark, 2010

IEICE Proceeding Series

Single carrier cyclic prefixed transmissions between a base station having multiple antenna and a... more Single carrier cyclic prefixed transmissions between a base station having multiple antenna and a terminal having one antenna are considered. We propose two antenna selections based on the channel norm and on the worst channel gain. Our selection schemes do not always yield the optimal selection but have less computational complexities. The channel norm criterion has the least complexity, while the channel gain criterion exhibits almost the same performance with the optimal selection.

Proceedings of the ISCIE International Symposium on Stochastic Systems Theory and its Applications, 2011

Two problems on the blind detection of phase shift keying (PSK) signals are studied. One is the d... more Two problems on the blind detection of phase shift keying (PSK) signals are studied. One is the detection of the existence of PSK signals and the other is the detection of the transmitted PSK symbols. From the probability density function of the absolute values of the received signals, a likelihood ratio test is derived for the detection of the existence. Then, when PSK signals are present, a method to determine the decision regions to detect PSK symbols is developed. It is shown that the estimation can be approximated as a least squares problem that can be numerically solved. Simulation results show that our detector for the existence of QPSK signals slightly outperforms the energy detector. The bit error rates of the detection of QPSK symbols using the estimated decision regions are also provided to demonstrate the performance of our estimator.

In this paper a method that mixes tone reservation (TR) techniques and phase information of the p... more In this paper a method that mixes tone reservation (TR) techniques and phase information of the pilot tones to efficiently reduce the peak to average power ratio (PAPR) of the multiple input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) signals is presented. First, we utilize convex optimization techniques to design dummy symbols to unused or reserved set of subcarriers to reduce the PAPR of the transmitted data in an OFDM symbol. Then, to the pilot tones dedicated for channel estimation, we design phase information to further reduce the PAPR. To design phase information of the pilot tones in MIMO-OFDM systems, we resort to the previously proposed cross entropy (CE) optimization techniques used for pilot phase design in single input single output (SISO) OFDM systems. Simulation results show that, by mixing the dummy symbols and pilot phase information the PAPR of the MIMOOFDM signals can be effectively reduced.