• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.676-682
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• 2018

As the IoT world including WSNs develops, the number of sensor systems that sense information according to the environment based on the principle of IoT is increasing. In order to perform security for each sensor system in such a complicated environment, the security modules must be varied. These problems make hardware/software implementation difficult when considering the system efficiency and hacking/cracking. Therefore, to solve this problem, this paper proposes a pseudorandom number generator (FLT: Pseudo-random Number Generator with Fixed Length Tap unrelated to the variable sensing nodes) with a fixed-length tap that generates a pseudorandom number with a constant period, irrespective of the number of sensing nodes, and has the purpose of detecting anomalies. The proposed FLT-LFSR architecture allows the security level and overall data formatting to be kept constant for hardware/software implementations in an IoT environment. Therefore, the proposed FLT-LFSR architecture emphasizes the scalability of the network, regardless of the ease of implementation of the sensor system and the number of sensing nodes.

• The KIPS Transactions:PartB
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• v.10B no.2
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• pp.229-236
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• 2003

Named entity recognition is the process indispensable to question answering and information extraction systems. This paper presents an HMM based named entity (m) recognition method using the construction principles of compound words. In Korean, many named entities can be decomposed into more than one word. Moreover, there are contextual relationships among nouns in an NE, and among an NE and its surrounding words. In this paper, we classify words into a word as an NE in itself, a word in an NE, and/or a word adjacent to an n, and train an HMM based on NE-related word types and parts of speech. Proposed named entity recognition (NER) system uses trigram model of HMM for considering variable length of NEs. However, the trigram model of HMM has a serious data sparseness problem. In order to solve the problem, we use multi-level back-offs. Experimental results show that our NER system can achieve an F-measure of 87.6% in the economic articles.

• Journal of Digital Convergence
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• v.11 no.2
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• pp.287-297
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• 2013

In this paper, we propose an efficient variable-length radix-8/4/2 FFT architecture for OFDM systems. The FFT processor is based on radix-8 FFT algorithm and also supports radix-4 or radix-2 FFT computation. We are using efficient "In-place" memory access method to maintain conflict-free data access and minimize memory size. Also we replace a very large lookup table with a twiddle factor generator which consumes less area then a ROM-based lookup table. The proposed FFT processor performs variable-length FFT including 64, 256, 512, 1024, 2048, 4096 and 8192 points which cover all the required FFT lengths used in 802.11a, 802.16a, DAB, DVB-T, VDSL and ADSL.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.202-205
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• 2012

기존의 고정 길이 분할 (FLC: Fixed Length Chunking) 중복 제거 기법은 파일이 조금이라도 수정이 되면 수정된 블록에 대한 해시 정보가 달라져 중복 데이터 임에도 불구하고 중복 블록으로 검색이 되지 않는 문제점이 있다. 본 연구에서는 FLC 기반의 중복 제거 기법에 데이터 위치(offset) 정보를 활용하여 중복 블록을 효율적으로 찾아냄으로써 기존의 FLC 기반의 중복 제거 기법보다 더 좋은 성능을 발휘하는 유사도 정보를 활용하는 중복 제거 기법(FS_FLC: File Similarity based Fixed Length Chunking)을 설계하고 구현했다. 실험 결과 제안한 알고리즘은 낮은 오버헤드로 가변 분할 기법(VLC: Variable Length Chunking)만큼의 높은 중복 데이터 탐색 성능을 보여주었다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.178-181
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• 2012

본 논문에서는 가변 길이 분할을 사용한 파일 동기화 시스템에서 메타 데이터 교환 오버헤드를 최소화 하기위한 효율적인 접근 방식을 제안한다. 본 논문의 주요 아이디어는 해시 압축 알고리즘을 사용하여 여러 개의 해시키를 하나의 해시키로 치환하여 메타 데이터 교환 비용을 최소화 하는 것이다. 본 논문에서는 제안 알고리즘의 타당성을 증명하기 위해 기존의 파일 동기화 프로그램과 비교 실험하였으며 통신비용과 에너지 소모 실험을 통해 메타 데이터를 10배 이상 줄일 수 있음을 보였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.506-512
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• 2018

Unmanned aerial vehicles(UAVs) operating in the military for various purposes are designed to transmit information collected according to the purpose to GCS(Ground Control System), and to transmit/receive the vehicle's operational control and status information using wireless communication(or datalink). Currently, the military UAV systems in operation in Korea use unique communication methods, protocols, and message structures for each system. Among these, the Division UAV is designed to transmit fixed size TM/TC data repeatedly and the Corps UAV is designed to transmit aperiodic TM/TC data to the variable length of the message-based. In this paper, we analyze the TM/TC data protocol of existing military UAV systems and present data protocol design method which is considered to be more efficient in wireless communication environment applied to equipment under development. And we will discuss issues to be considered for standardization of technology for ensuring interoperability with many UAVs or newly introduced UAV systems.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.24 no.4
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• pp.739-751
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• 2014

We are using our smartphone for our business as well as ours lives. Thus, user's privacy data and a company secret are stored at smartphone. By the way, the saved data on smartphone database can be exposed to a malicous attacker when a malicous app is installed in the smartphone or a user lose his/her smartphone because all data are stored as form of plaintext in the database. To prevent this disclosure of personal information, we need a database encryption method. However, if a database is encrypted, it causes of declining the performance. For example, when we search specific data in condition with encrypted database, we should decrypt all data stored in the database or search sequentially the data we want with accompanying overhead[1]. In this paper, we propose an efficient and searchable encryption method using variable length bloom filter under limited resource circumstances(e.g., a smartphone). We compare with existing searchable symmetric encryption. Also, we implemented the proposed method in android smartphone and evaluated the performance the proposed method. As a result through the implementation, We can confirm that our method has over a 50% improvement in the search speed compared to the simple search method about encrypted database and has over a 70% space saving compared to the method of fixed length bloom filter with the same false positive rate.

• Journal of the Korean Society for Library and Information Science
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• v.30 no.1
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• pp.3-18
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• 1996

This article analyzes the record structure, content designation, and the content of UNIMARC, USMARC, and KORMARC formats for authorities, through the comparative investigation, Structure and content designation are almost same with those of the bibliographic formats, being based on those of ISO 2709. The data fields of USMARC and KORMARC are divided into blocks based on the traditional authority card formats, and those of UNIMARC are divided into functional blocks based on the GARE. Record contents of the formers in the fixed-length fields include more elements on the selectioa status and scope of the heading, and those related to the series. And those of the later include more elements for the international exchange. Based on the analysis of the variable fields, it is recommended that KORMARC should include an additional subfield, say $(\blacktriangledown\;j)$ for the processing of the Hanja(Chinese character) data and add the separate classification fields for series.

• Journal of IKEEE
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• v.26 no.4
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• pp.568-576
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• 2022

Automatic modulation classification(AMC) is a core technique in Software Defined Radio(SDR) platform that enables smart and flexible spectrum sensing and access in a wide frequency band. In this study, we propose a simple yet accurate deep learning-based method that allows AMC for variable-size radio signals. To this end, we design a classification architecture consisting of two Convolutional Neural Network(CNN)-based models, namely main and small models, which were trained on radio signal datasets with two different signal sizes, respectively. Then, for a received signal input with an arbitrary length, modulation classification is performed by augmenting the input samples using a self-replicating padding technique to fit the input layer size of our model. Experiments using the RadioML 2018.01A dataset demonstrated that the proposed method provides higher accuracy than the existing methods in all signal-to-noise ratio(SNR) domains with less computation overhead.

• Journal of Internet Computing and Services
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• v.8 no.5
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• pp.161-170
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• 2007

The proposed switch which has separated data plane and switching plane can make parallel processing for packet data storing, memory address pointer switching and simultaneously can be capable of switching the variable length for IP packets. The proposed architecture does not require the complicated arbitration algorithms in VOQ, also is designed for QoS of generic output queue switch as well as input queue. At the result of simulations, the proposed architecture has less average packet delay than the one of the memory-sharing based architecture and guarantees keeping a certain average packet delay in increasing switch size.