• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.11B
• /
• pp.1879-1883
• /
• 2000

디지털 자기 기록 저장기기에서 채널 밀도가 증가하면 심각한 인접심볼 간섭과 비선형 왜곡이 야기된다. 본 논문에서는 심각한 비선형 인접심볼 간섭과 비선형 왜곡을 극복하기 위한 방법으로 기존의 등화기 대신 NLTE(neural linear transversal equalizer)를 등화기로 사용하고 검출기로는 터보 코드를 사용한 NLTE/TC 구조를 제안한다. 채널 밀도 S=2.5에서 부분 삭제가 0.7 정도 존재할 때, 코드율이 8/9일 때는 $10^{-5}$의 비트 에러율을 18dB 이후에서 만족하며, 코드율이 16/17일 때는 20dB 이후에서 만족함을 알 수 있었다. 채널 밀도 S=3에서 부분 삭제가 0.6 정도 존재할 때 코드율이 8/9일 때는 $10^{-5}$의 비트 에러율을 22dB 이후에서 만족하고, 코드율이 16/17일 때는 24dB 이후에서 만족함을 확인할 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.8C
• /
• pp.1034-1039
• /
• 2004

Since the major reason of the detection failure is from the consecutive data transitions, it is desirable to limit the MTR(maximum transition run) within two. Therefore, we propose a new MTR code that limits the MTR constraint to 2 and k-constraint to 8. In addition, DC-free coding is performed to overcome the media noise that exits in low frequency of perpendicular recording system. We use a GS (Guided Scrambling) for DC-free coding, and the performance of the code is compared with that of the rate 819 code used in the conventional recording channel by a computer simulation.

• Journal of the Korean Society for Precision Engineering
• /
• v.20 no.10
• /
• pp.169-176
• /
• 2003

Genetic algorithm (GA), which has a powerful searching ability and is comparatively easy to use and also to apply, is in the spotlight in the field of the optimization for mechanical systems these days. However, it also contains some problems of slow convergence and low efficiency caused by a huge amount of repetitive computation. To improve the processing efficiency of repetitive computation, some papers have proposed paralleled GA these days. There are some cases that mention the use of gray code or suggest using gray code partially in GA to raise its slow convergence. Gray code is an encoding of numbers so that adjacent numbers have a single digit differing by 1. A binary gray code with n digits corresponds to a hamiltonian path on an n-dimensional hypercube (including direction reversals). The term gray code is open used to refer to a reflected code, or more specifically still, the binary reflected gray code. However, according to proposed reports, gray code GA has lower convergence about 10-20% comparing with binary code GA without presenting any results. This study proposes new Full gray code GA (FGGA) applying a gray code throughout all basic operation fields of GA, which has a good data processing ability to improve the slow convergence of binary code GA.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.4C
• /
• pp.247-252
• /
• 2005

Currently, the decoder receives a 16 bit channel input and restores an 8 bit data symbol in the DVD system. Such modulation code of DVD is the EFMplus code, and it is composed of a main table and a sub table. For reducing the size of the code table, this paper divided the code table into 3 groups and we implemented the decoder using this new code table. After all, this method enables us to reduce the size of ROM as reducing the total number of code from 1376 to 750.

• Proceedings of the KAIS Fall Conference
• /
• 2009.12a
• /
• pp.626-629
• /
• 2009

본 논문에서는 MPEG2(Moving Picture Expert Group 2)비디오 디코더에서 영상데이타를 디코딩하는 기술에 관한 것으로, 종래의 동여상 처리기에서는 허프만 코드화 처리를 하여 정지영상을 부호화한 후 분할기반 부호화 방식의 동영상 처리기법을 사용하였으나 1프레임의 코드화시에도 많은 계산 알고리즘이 필요하고 이미지의 닮음정도를 객관적수치로 표현할 수 없으므로 비슷한 이미지를 중복 코드화 작업 및 전송 작업을 하는 결함이 있었다. 본 눈문에서는 이를 해결하기 위하여 이미지의 닮음정도를 수치화하고 기준값 이하의 영상은 코드화 작업을 하지않고 계산된 영상 변화값에 의해 구현된 영상으로 대체하여 저장 및 전송하도록 하여 시각적으로 전혀 거부감이 없는 동영상을 구현하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38A no.6
• /
• pp.459-464
• /
• 2013

In this paper, we introduce a modulation code design problem where best selection of two-dimensional codewords are determined to reduce two-dimensional (2D) intersymbol interference (ISI) and interpage interference (IPI). Codeword selection problem is formulated as a quadratic integer programming model that minimizes intra- and inter-symbol differences subject to uniform symbol usage and minimal Hamming distance violations. Second integer programming model detects the occurrence of isolated pixel pattern in the selected codewords. The proposed models are applied to 4-level and 2-level 6/8 codes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.18 no.1
• /
• pp.1-9
• /
• 1993

In this paper, a new digital mobile channel has been modeled. And concatenated code systems have been proposed to transmit information reliably in the newly modeled mobile fading channels. The BCH code has been used as the outer code and the convolutional code as the inner code. We have modeled the channels which have multipath fading phenomena and additive white Gaussian noise. As a result, the characteristics of the channels are identical to that of the mobile fading channel. To find the best code system, we have tested (7, 4), (63, 45), (63, 57) and (31.26) BCH codes as an outer code. Results show that the concatenated code with (7, 4) outer code gives the best performance. And if we use the soft decision, we can improve about 2 -6 dB in the SNR

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.30 no.4
• /
• pp.593-603
• /
• 2020

The advent of malicious code has increased exponentially due to the spread of malicious code generation tools in accordance with the development of the network, but there is a limit to the response through existing malicious code detection methods. According to this situation, a machine learning-based malicious code detection method is evolving, and in this paper, the feature of data is extracted from the PE header for machine-learning-based malicious code detection, and then it is used to automate the malware through autoencoder. Research on how to extract the indicated features and feature importance. In this paper, 549 features composed of information such as DLL/API that can be identified from PE files that are commonly used in malware analysis are extracted, and autoencoder is used through the extracted features to improve the performance of malware detection in machine learning. It was proved to be successful in providing excellent accuracy and reducing the processing time by 2 times by effectively extracting the features of the data by compressively storing the data. The test results have been shown to be useful for classifying malware groups, and in the future, a classifier such as SVM will be introduced to continue research for more accurate malware detection.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.25 no.2
• /
• pp.321-330
• /
• 2015

There have been found many modified malwares which could avoid detection simply by replacing a sequence of characters or a part of code. Since the existing anti-virus program performs signature-based analysis, it is difficult to detect a malware which is slightly different from the well-known malware. This paper suggests a method of detecting modified malwares by extending a hash-value based code comparison. We generated hash values for individual functions and individual code blocks as well as the whole code, and thus use those values to find whether a pair of codes are similar in a certain degree. We also eliminated some numeric data such as constant and address before generating hash values to avoid incorrectness incurred from them. We found that the suggested method could effectively find inherent similarity between original malware and its derived ones.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.12
• /
• pp.2363-2369
• /
• 2016

In this paper, we propose three-dimensional (3D) quick-response (QR) code generation technique using passive 3D integral imaging and computational integral imaging reconstruction technique. In our proposed method, we divide 2D QR code into 4 planes with different reconstruction depths and then we generate 3D QR code using synthetic aperture integral imaging and computational reconstruction. In this 3D QR code generation process, we use integral imaging which is one of 3D imaging technologies. Finally, 3D QR code can be scanned by reconstructing and merging 3D QR codes at 4 different planes with computational reconstruction. Therefore, the security level for QR code scanning may be enhanced when QR code is scanned. To show that our proposed method can improve the security level for QR code scanning, in this paper, we carry out the optical experiments and computational reconstruction. In addition, we show that 3D QR code can be scanned when reconstruction depths are known.