• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.557-560
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• 2014

In digital communications systems, an interleaver spreads burst errors occurred in channels and makes it random errors. As a result, the signals are rearranged and encrypted to the 3rd party. Deinterleaving this unknown interleaved signal is very important in electronic warfare and various researches on reconstruction of interleaved signal have been studied in the literature. Unlike previous researches which is mainly about helical scan interleaver or bit unit interleaver, in this paper, we estimate the symbol unit convolutional interleavr and shortened Reed-Solomon code parameters such as the number of stages of interleaver, a codeword length and a data symbol length and propose an specific algorithm to obtain the parameters from the unknown interleaved signal and simulate this algorithm as well.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.13 no.3
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• pp.57-64
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• 2003

Recently, it has been shown that cryptographic devices such as smart cards are vulnerable to power attacks. In this paper, by mixing the randomization concept and the folding in half for secret scalar integer on ECCs, we propose an efficient and fast scalar multiplication algorithm to resist against simple power analysis(SPA) and differential power analysis(DPA) attacks. Our proposed algorithm as a countermeasure against SPA and DPA is estimated as a 33% speedup compared to the binary scalar multiplication.

• Journal of Broadcast Engineering
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• v.28 no.1
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• pp.141-144
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• 2023

Recently, a joint channel estimation, channel quantization, feedback, and precoding system based on deep-neural network (DNN) was proposed. The corresponding system achieved a joint optimization based on deep learning such that it achieved a higher sum rate than the existing codebook-based precoding systems. However, this DNN-based procoding system is not directly applicable for the environments with many users such that a specific user selection can potentially increase the sum rate of the system. Thus, in this letter, we study an appropriate user selection method suitable for DNN-based precoding.

• Smart Media Journal
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• v.12 no.2
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• pp.36-41
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• 2023

With the advent of applicant tracking systems, online recruitment has become more popular, and recruitment fraud has become a serious problem. This research aims to develop a reliable model to detect recruitment fraud in online recruitment environments to reduce cost losses and enhance privacy. The main contribution of this paper is to provide an automated methodology that leverages insights gained from exploratory analysis of data to distinguish which job postings are fraudulent and which are legitimate. Using EMSCAD, a recruitment fraud dataset provided by Kaggle, we trained and evaluated various single-classifier and ensemble-classifier-based machine learning models, and found that the ensemble classifier, the random forest classifier, performed best with an accuracy of 98.67% and an F1 score of 0.81.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.7
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• pp.989-998
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• 1993

In a bursty user traffic mode, ALOHA random multiple access protocol achieves higher performance than any conventional fixed assignment technique. One of central problems in slotted ALOHA is synchronization. Because of the long propagation delay in satellite mobile communication, packet may be spilt over into adjacent slots and thus guard time may be included between packet intervals. In conventional ALOHA channels, simultaneous transmission by two or more users results in a collision : the unsuccessful packets have to be retransmitted according to some retransmission algorithm. However, in a radio environment, users are often at different distances from the receiver : therefore, their received signals have substantially different power levels. The packet arriving with the highest energy now has a good chance of being detected accurately. Similarly, in some spread-spectrum random access systems, the earliest arriving packet dominates later arriving packets and thus captures the channel. In this paper slotted ALOHA channel with non zero guard time and capture probability is studied. Using the Markovian model, the performance of slotted ALOHA with guard time and capture effects is derived and compared with that of the conventional ALOHA via numerical analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.12
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• pp.5036-5041
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• 2010

This paper introduces the complex-version of an Euclidean distance minimization algorithm based on a set of delta functions. The algorithm is analyzed to be able to compensate inherently the channel phase distortion caused by inferior complex channels. Also this algorithm has a relatively small size of Gaussian kernel compared to the conventional method of using a randomly generated symbol set. This characteristic implies that the information potential between desired symbol and output is higher so that the algorithm forces output more strongly to gather close to the desired symbol. Based on 16 QAM system and phase distorted complex-channel models, mean squared error (MSE) performance and concentration performance of output symbol points are evaluated. Simulation results show that the algorithm compensates channel phase distortion effectively in constellation performance and about 5 dB enhancement in steady state MSE performance.

• Journal of Korea Multimedia Society
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• v.10 no.1
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• pp.58-65
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• 2007

This dissertation proposes digital video protection algorithm lot moving image based on MPEG. Shuffling-based encryption algorithms using a fixed random shuffling table are quite simple and effective but vulnerable to the chosen plaintext attack. To overcome this problem, it is necessary to change the key used for generation of the shuffling table. However, this may pose a significant burden on the security key management system. A better approach is to generate the shuffling table based on the local feature of an image. In order to withstand the chosen plaintext attack, at first, we propose a interleaving algorithm that is adaptive to the local feature of an image. Secondly, using the multiple shuffling method which is combined interleaving with existing random shuffling method, we encrypted the DPCM processed 8*8 blocks. Experimental results showed that the proposed algorithm needs only 10% time of SEED encryption algorithm and moreover there is no overhead bit. In video sequence encryption, multiple random shuffling algorithms are used to encrypt the DC and AC coefficients of intra frame, and motion vector encryption and macroblock shuffling are used to encrypt the intra-coded macroblock in predicted frame.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.803-809
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• 2011

In this paper, we present a very useful method for updating digital satellite radio broadcast channel information. When a devices equipped with function to receive Digital Satellite Radio such as Home Theater, MP3 player, mobile phones, car audio system and various other types of Digital Devices, receives new Digital satellite radio (will be mentioned as XM radio onwards) broadcast channel information, only the current received XM radio broadcast channel and N number of pre/post nearby broadcast channels are scanned randomly in zigzag manner. Then the previous XM radio broadcast channel information updated with the newly received XM radio broadcast channel information. Since this method can prevent batch update for all XM radio channel, including some channels which less likely did not select by user, update process for real time frequently changed XM radio broadcast channel information can be performed efficiently with minimal or without delay.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.507-507
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• 2013

유리기판으로 투과되는 빛들 중에는 내부 전반사나 wave-guided mode로 인하여 손실이 일어나 일반적으로 20%의 광추출 효율을 가진다. 이러한 문제점을 해결하기 위한 연구에는 Photonic Crystal과 같은 주기적인 나노 구조물이 있는데 이러한 구조물을 제작하기 위한 마스크 공정 과정은 대부분 복잡하거나 비싼 단점이 있다. 이에 본 발표에서는 마스크 없이 비정질소다라임 유리의 구조물 생성으로 광 추출 효율이 상승하는지 보고자 하였다. M-ICP (Magnetized-Induced Coupled Plasma)란 용량 결합형 플라즈마와 유도 결합형 플라즈마 두 가지 방식의 플라즈마를 이용한 것인데 용량 결합형 플라즈마를 이용해 이온이 sheath에 의해 가속되어 유리표면에 부딪히고 그에 따라 유리가 식각되는 물리적 식각을 이용하였다. 또한 이온의 밀도를 조절하기 위해 유도결합형 플라즈마 방식을 이용하여 식각률을 높였다. 화학적 식각을 위해서는 CF4와 O2혼합 가스를 이용해 F가 Si와 결합하여 SiF4가 되어 사라지고 탄소잔여물인 C는 O2와 반응하여 제거하였다. 그 결과, 랜덤한 분포를 가지는 미세한 구조물(stochastic sub-wavelength structure)을 유리 표면에 형성할 수 있었고, 또한 다양한 가스 종류와 압력, source power와 bias power, 그리고 시간을 바꿔가며 미세 구조물들을 관찰하였다. 실험 결과, 가시광선 파장 이하의 높이를 갖고 수 마이크로미터의 너비를 갖는 구조물이 전반사되는 빛을 효율적으로 추출하는 것을 산란되는 빛의 정도인 diffusive transmittance 가 기존 0%에서 15% 정도로 증가하는 것으로 스펙트로포토미터 측정을 통해 확인하였다. 이러한 유리 기판 위 구조물 생성방법을 OLED에 적용한다면 적은 비용으로 소자의 효율을 크게 향상 시킬 수 있을 것이다. 또한 본 처리 과정의 장점은 기존의 방법에 필요한 스퍼터링이나 RTA 처리 과정이 필요 없어 공정 단가 절감과 제조 공정의 단순화로 높은 생산성을 얻을 수 있으며 대면적화에도 유리하다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4A
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• pp.269-277
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• 2012

When there are mismatches between the beamforming steering vector and the array response vector for the desired signal, the performance can be severely degraded as the adaptive array attempts to suppress the desired signal as well as interferences. In this paper, an robust method is proposed for the adaptive array in the presence of both direction errors and random errors in the steering vector. The proposed method first finds a signal-plus-interference subspace (SIS) from the correlation matrix, which in turn is exploited to extract an interference subspace based on the structure of a uniform linear array (ULA), the effect of the desired signal direction vector being reduced as much as possible. Then, the weight vector is attained to be orthogonal to the interference subspace. Simulation shows that the proposed method, in terms of signal-to-interference plus noise ratio (SINR), outperforms existing ones such as the doubly constrained robust Capon beamformer (DCRCB).