• The Journal of the Korea Contents Association
• /
• v.9 no.4
• /
• pp.189-197
• /
• 2009

A digital image usually has 8 bits of depth basically representing pixel intensity ranging for [0 255]. These pixel range allow 256 step levels of pixel values in the image. Thus the greyscale value for a given image is an integer. When we carry out interpolation of a given image for resizing we have to round the interpolated value to integer which can result in loss of quality on perceived color values. This paper proposes a new method for recovering this loss of information during interpolation process. By using the proposed method the pixels tend to regain more original values which yields better looking images on resizing.

• The Journal of the Acoustical Society of Korea
• /
• v.15 no.2
• /
• pp.95-100
• /
• 1996

In this paper, we present an image coder using variable quantizer for newly proposed JPEG extensions which has been standardized as ISO/IEC 10918-3(ITU-T Rec. T.84). It is necessary to alleviate the blocking artifact which is more sensitive to human eye in view of the spatial frequency sensitivity. The blocking artifact arises in the lower activity area rather than in the higher area. Therefore variable quantizer use the horizontal and vertical derivatives for calculating the $8{\times}8$ block activity. We classified nonlinear quantizer parameter into 5 categories in order to finely quantize in the lower active region. As a result of simulation for various images, the proposed coder increases subjective and objective quality at a given bit rate.

• Journal of KIISE:Computing Practices and Letters
• /
• v.5 no.2
• /
• pp.176-184
• /
• 1999

지금까지의 소프트웨어 기반 분산 공유 메모리(이하 DSM이라 칭함)시스템은 유닉스 워크스테이션 클러스터를 목표로 하는 것이 대부분이었다. 그러나 현재 Windows-NT 는 서버급 시스템과 PC 모두를 위한 운영체제로서 유닉스와 더불어 널리 사용되고 있는 실정이다. 본 논문에서는 Windows-NT 워크스테이션 클러스터 환경을 위한 DSM 시스템을 구현하고, 구현된 DSM 시스템의 성능 평가 결과를 제시한다. 구현된 DSM 시스템은 Win32 API와 표준 실행-시간 라이브러리를 이용해 구현되었기 때문에 모든 Windows-NT 워크스테이션에서 실행 가능하며 , 프로그래머는 몇 라인의 코드 추가만으로 DSM 시스템 상에서 수행되는 병렬 응용 프로그램을 작성할 수 있다. 워크스테이션 간의 상호연결망으로 범용성을 위해 이더넷 LAN을 지원하였고, 아울러 성능 향상을 위해 기가비트 SAN(System Area Network)도 지원하였다. 기가비트 SAN을 위한 하드웨어로는 Dolphin 사의 PCI-SCI 타입 제품인 Clustar를 사용하였다. 우리는 성능 평가를 통해, 구현된 DSM 시스템이 정확히 동작함은 물론 확장성이 뛰어나다는 것을 확인하였다. 특히 , 기가비트 SAN을 사용할 경우 일부 병렬 벤치 마크 프로그램에서는 노드 수 증가에 따라 성능이 거의 선형적으로 향상된다는 것을 알 수 있었다. 본 논문이 기여하는 바는 Windows-NT 기반 소프트웨어 DSM 시스템의 원천 기술을 확보함으로써 향후 Windows-NT 워크스테이션 클러스터 환경에서의 분산 및 병렬 처리 연구에 도움을 줄 수 있다는 점이다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.7A
• /
• pp.668-675
• /
• 2002

This paper proposes pre-distorter combined LUT with 2ιpartition interpolation method to reduce nonlinear distortion which was caused by high PAPR and to update LUT quickly. Pre-distorted gain and phase can be found by using LUT which consisted of AM/AM and AM/PM value, and OFDM signal amplitude. The proposed 2ιpartition interpolation can accurately find predistorted gain and phase using bit shift and add component instead of increasing size of LUT which requires increasing the amount of computation. The performance of the proposed method was measured by the difference between HPA input and output characteristics by the LUT size, constellation, SER performance by the HPA, and LUT update error by the HPA characteristic changes. As a result, it is shown that when the size of the LUT is 32 and 64 for 16-QAM and 64-QAM, nonlinear distortion nearly didn't occurred.

• Journal of the Korea Society of Computer and Information
• /
• v.10 no.3 s.35
• /
• pp.151-159
• /
• 2005

Traditional watermarking technologies are symmetric method which embedding and detection keys are same. Although the symmetric watermarking method is easy to detect the watermark, this method has weakness against to malicious attacks to remove or modify the watermark information when the symmetric key is disclosure. Recently, the asymmetric watermarking method that has different keys to embed and detect is watched several researchers as a next generation watermarking technology. In this paper, we have expanded search space of secret key using the solution set of linear simultaneous equations. Secret key is generated by secure linear transformation method to prevent of guessing secret key from public key, and the correlation value between secret key and public key is high. At theresults, the multi bits information can be embedded and high correlation value was detected after JPEG compression.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.49 no.8
• /
• pp.1-11
• /
• 2012

The multi-code spread spectrum communication system, which spreads data bit stream by multiplexing orthogonal codes, can transmit data in high rate. However it needs the high-cost good linear amplifier because of the multi-level output signal. In order to overcome this drawback several systems making the amplitude of output signal constant with Walsh codes have been proposed. Recently constant amplitude pre-coded multi-code spread spectrum systems using extended m-sequence have been proposed. In this paper we consider an extended m-sequence based constant amplitude multi-code spread spectrum system with code set partitioning. By grouping the orthogonal codes into 4 subsets, not only is the computational complexity of the transceiver reduced but BER performance also improves. It has been shown that parity checking on four detected codes at the receiver can correct code detection error and result in BER performance enhancement. In this paper we propose a improved parity check receiver. We carried out computer simulation to verify feasibility of the proposed algorithm.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.13 no.1
• /
• pp.47-57
• /
• 2003

In this paper, we firstly evaluate the resistance of the reduced 5-round version of the block cipher CIKS-1 against linear cryptanalysis(LC) and show that we can attack full-round CIKS-1 with \ulcorner56-bit key through the canonical extension of our attack. A feature of the CIKS-1 is the use of both Data-Dependent permutations(DDP) and internal key scheduling which consist in data dependent transformation of the round subkeys. Taking into accout the structure of CIKS-1 we investigate linear approximation. That is, we consider 16 linear approximations with p=3/4 for 16 parallel modulo $2^2$ additions to construct one-round linear approximation and derive one-round linear approximation with the probability P=1/2+$2^{-17}$ by Piling-up lemma. Then we present 3-round linear approximation with 1/2+$2^{-17}$ using this one-round approximation and attack the reduced 5-round CIKS-1 with 64-bit block by LC. In conclusion we present that our attack requires $2^{38}$chosen plaintexts with a probability of success of 99.9% and about $2^{67-7}$encryption times to recover the last round key.(But, for the full-round CIKS-1, our attack requires about $2^{166}$encryption times)

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.12
• /
• pp.2331-2342
• /
• 2015

In this paper, we design non-linear transmitter and receiver using a uniform channel decomposition (UCD) to take account of inter-cell interference in multi-cell downlink systems. The designed UCD scheme brings forth the same SINR for all sub-channels in each cell. It provides great convenience to modulation/coding process and achieves the maximum diversity gain. The simulation results confirm that it exhibits a lower BER than the conventional method.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.41 no.6
• /
• pp.1-7
• /
• 2004

The rapid growth of digital media and communication networks has created an urgent need for self-contained data identification methods to create adequate intellectual property right(IPR) protection technology. In this paper we propose a new watermarking method that could embed the gray-scale watermark logo in low frequency coefficients of discrete wavelet transform(DWT) domain as the marking space by using our Linear Bit-eXpansion(LBX) interleaving of gray-scale watermark, to use lots of watermark information without distortion of watermarked image quality and particularly to be robust against attack which could remove a part of image. Experimental results demonstrated the high robustness in particular against attacks such as image cropping and rotation which could remove a part of image.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.11 no.10
• /
• pp.1828-1834
• /
• 2007

This study proposes a new digital watermarking technique based on wavelet transformation on color image. First the $YC_bC_r$ coordinates obtain from RGB color space. then, the correlation of watermark is decreased by Arnold transformation. Next, watermark which has been enlarged by Linear Bit-expansion is inserted at a given intensity in Color images' low frequency sub-bands. When detecting the presence of watermark, F-norm function is applied. As a result of the various experiments on color images, the proposed watermarking technique has outstanding quality in regards to fidelity and robustness.