• Journal of Institute of Control, Robotics and Systems
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• v.4 no.5
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• pp.561-566
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• 1998

This paper presents an algebraic approach to optimal control for time invariant continuous system using STWS(single term Walsh series). In optimal control, it is well known that the design problem with quadratic performance criteria often involves the determination of time-varying feedback gain matrix by solving the matrix nonlinear Riccati equation and of command signal by solving the integral equation, which makes design procedure quite difficult. Therefore, in order to resolve this problem, this paper is introduced to STWS. In this paper, the time-varying feedback gains and command signals are determined by piecewise constant gains which can be easily obtained from algebraic equation using STWS.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.5
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• pp.579-584
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• 1998

This paper presents an efficient algorithm which determines the parameters of discrete PID controller. The proposed algorithm is an algebraic method to obtain controller parameters using ROM(Reduced Order Model), which can not only make design procedure simple but also reduce the computational burden required for controller implementation. Also, by solving a set of linear equations based on least squares method, the proposed method can make the controller design procedure systematic. Simple examples are given to demonstrate the effectiveness of our method when compared with widely-used conventional method.

• Journal of applied mathematics & informatics
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• v.29 no.1_2
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• pp.145-159
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• 2011

The numerical solution to the linear and nonlinear and linear system of Fredholm and Volterra integral equations of the second kind are investigated. We have used crooked lines which includ the nodes specified by modified rationalized Haar functions. This method differs from using nominal Haar or Walsh wavelets. The accuracy of the solution is improved and the simplicity of the method of using nominal Haar functions is preserved. In this paper, the crooked lines with unknown coefficients under the specified conditions change the system of integral equations to a system of equations. By solving this system the unknowns are obtained and the crooked lines are determined. Finally, error analysis of the procedure are considered and this procedure is applied to the numerical examples, which illustrate the accuracy and simplicity of this method in comparison with the methods proposed by these authors.

• The KIPS Transactions:PartB
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• v.8B no.3
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• pp.305-310
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• 2001

본 논문에서는 직접행렬 대역확산 방식을 사용하여 Hadamard-Walsh 행렬을 워터마크 영상에 첨가한 후, 주파수 영역에서 원 영상에 삽입하고 복원하는 새로운 이미지 워터마킹 기법을 제안한다. 워터마크 영상은 시각적으로 인식 가능한 패턴(마크, 로고, 심볼, 인장 또는 서명)을 사용한다. 워터마크가 삽입된 영상의 화질저하를 추정하기 위해 PSNR(Peak Signal to Noise Ratio)을 계산하고, 복원된 워터마크의 복원률(reconstructive rate)을 구하여 외부공격에 대한 워터마크의 강인성을 확인한다. 표준영상에 적용해 본 결과, 워터마크가 삽입된 영상의 PSNR은 93.2dB로 우수한 화질을 얻을 수 있었으며 JPEG 손실 압축에서는 78.1% 이상의 워터마크 복원률을 얻을 수 있었고 영상변형 및 임펄스 잡음하에서도 효과적인 워터마크 복원 능력을 보였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.05a
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• pp.1481-1484
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• 2005

In this paper, we propose a novel OFDM-based system structure to reduce PAPR (Peak-to-Average Power Ratio) and improve BER for OFDM system in which BER enhancement is obtainable based on WH (Walsh-Hadamard) transform to transmit concurrently each data symbol on all subcarriers so as to take advantage of frequency diversity and remedy the effect of channel's frequency-selectivity. By doing so, we also attain a low PAPR. Moreover, DGT (Data Grouping Technique) that is independent on the side information is also applied to further reduce PAPR. The simulation programs have been also performed to verify the validity of the proposed system.

• Journal of Biomedical Engineering Research
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• v.11 no.1
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• pp.163-170
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• 1990

In this paper, fast Fourier transform and fast Walsh transform algorithm are studied for ECG data compression. ECG data-12 bit samples digitized at 480 samples-are segmented into QRS complexes and 50 intervals by di%ital derivative filter, which used for detection of QS width and difrerenre compressed in Fourler or welsh domain. And also the existing techniques for data compression-TP, MTP, CORTES, AZTEC, MCORTES, which have not been evaluated with a common measurement of goodness, were processed to get absolute terms of values in the same condition.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.10 no.1
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• pp.31-37
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• 1985

An interesting area of application which makes use of the unique features of the walsh series is that on non-linear stochastic problems. In particular, some success has been obtained in improving the efficiency of signal detection for those transducers which are essentially non-linear in operation. The set of harmonically-related nonorthogonal triangle waves is shown to form a basis apanning the same function space representable by fourier(trigonometric) series. A method for generating nonorthogonal bases for signal representation is presented tailor-made basis function can be used for specific purposes. Fundamental proofs of the basis properties of the representation are examined along with examples illustrating the techniques and computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1590-1598
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• 1997

The paper first introduces the new concept of potential diversity and signal decomposability, which establish a foundaton to generalize the existing concepts of path and frequency diversities. Then it presents a new DS/CDMA system called chip-spreading OCDM system, which is an embodiment of the petential diversity concept that combines the path diversity of the DS/CDMA system and the frequency diversity of the OFDM/CDMA system. In the chip-spreading OCDM system the chip sequences in each symbol interval are first converted into aralled streams, which then simultaneously modulate different orthogonal Walsh basis functions. In the receiver, the received signal is matched to each extended basis-function which is the union of the transmitter basis-functions and their delayed replicas, and the matched-filtered chip samples are combined together after individual channel compensation. The conventional DS/CDMA system using the maximal ratio combining. In addition, it effectively resolves the high PAR and high sensitivity to frequency offset problems which are critical in multi-carrier systems.

• The Journal of the Acoustical Society of Korea
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• v.6 no.1
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• pp.15-22
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• 1987

Fast Walsh-Hadamard Transform algorithm is discussed for secreting digital signals in ISDN. 16 characters are used for the password to control the coefficients of FWHT. And it gives above $3\times10^{38}$ codes. The FWHT module in presented in machine language. So it is applicable to compact cipher system or firmware system. Computer simulation showed secreting characteristics in printed data for N=128.

• The Pure and Applied Mathematics
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• v.6 no.2
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• pp.79-86
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• 1999

A Boolean function generates a binary sequence which is frequently used in a stream cipher. There are number of critical concepts which a Boolean function, as a key stream generator in a stream cipher, satisfies. These are nonlinearity, correlation immunity, balancedness, SAC (strictly avalanche criterion), PC (propagation criterion) and so on. In this paper we construct an algorithm for finding the correlation immune order of a Boolean function, and check how long to find the correlation immune order of a given Boolean function in our algorithm.