• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.123-125
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• 2015

Wireless ad hoc network which is comprised of wireless nodes that have the limited communication range is utilized to monitoring disaster area, tracing object, and tactical system. But in the case of wireless node on the ground, a network performance decrease because wireless channel is affected from obstacle or the node deployment is restricted. In this paper, we consider wireless network based on UAV(Unmanned Aerial Vehicle) which has little spatial constraint and quickly deploy a position. We implement test-bed included ground nodes and UAV, and measure throughput and PDR(Packet Delivery Ratio) according to the usage of UAV. We show that network performance is improved by relaying data on UAV.

• The Journal of the Acoustical Society of Korea
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• v.15 no.2
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• pp.79-84
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• 1996

In this paper, adaptive correlator model using backpropagation neural network based on complex multilayer perceptron is presented for suppressing interference of narrow-band of direct sequence spread spectrum receiver in CDMA mobile communication systems. Recursive least square backpropagation algorithm with backpropagation error is used for fast convergence and better performance in adaptive correlator scheme. According to signal noise ratio and transmission power ratio, computer simulation results show that bit error ratio of adaptive correlator uswing backpropagation neural network improved than that of adaptive transversal filter of direct sequence spread spectrum considering of co-channel and narrow-band interference. Bit error ratio of adaptive correlator using backpropagation neural network is reduced about $10^{-1}$ than that of adaptive transversal filter where interference versus signal ratio is 5 dB.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.398-402
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• 2003

In this paper, a VCDRO(Voltage Control Dielectric Resonator Oscillator) applied to FMCW(Frequency Modulated Continuous Wave)Radar as stable source is implemented and constructed with a MESFET for low noise, a dielectric resonator of high frequency selectivity, and high Q varator diode to obtain a good phase noise performance and stable sweep characteristics. The designed circuits is simulated thrash harmonic balance simulation technique to provide the optimum performance. The measured result of a fabricated VCDRO shows that output is 2.22dBm at 12.05GHz, harmonic suppression -30dBc, phase noise -130dBc at 100kHz offset, and sweep range of varator diode $\pm$18.7MHz, respectively. This oscillator will be available to FMCW Radar.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.157-164
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• 2012

This paper introduces an implementation of SVC player which runs on Android platform and can play SVC video stream on line from SVC video server. SVC(Scalable Video Coding) is a scalable video encoding technique which supports three scalability such as temporal scalability, spatial scalability, and quality scalability. To implement the SVC player on Android, we implemented a SVC decoder using JSVM open source written in C/C++ as a native part on Android and developed Android UI in Java. Also we built an SVC encoding system off line and an SVC streaming server to conduct on-line SVC streaming experiments. Finally, after we installed the SVC player developed in this paper on Motoroi mobile phone, we evaluated and analyzed on-line streaming performance of the SVC player. The result showed that the player worked well and it had no jitter in streaming with the size of QCIF and 10fps from a fully encoded SVC video source.

• The KIPS Transactions:PartA
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• v.9A no.4
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• pp.467-478
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• 2002

With the rapid development of wired or wireless Internet, various kinds of resource constrained mobile devices, such as cellular phone, PDA, homepad, smart phone, handhold PC, and so on, have been emerging into personal or commercial usages. Most software to be embedded into those devices has been forced to have the characteristic of flexibility rather than the fixedness which was an inherent property of embedded system. It means that recent technologies require the flexible embedding into the variety of resource constrained mobile devices. A document processor for XML which has been positioned as a standard mark-up language for information representation on the Web, is one of the essential software to be embedded into those devices for browsing the information. In this paper, a framework for configurable XML processor called EmXJ is designed and implemented for flexible embedding into various types of resource constrained mobile devices, and its advantages are compared to conventional XML processors.

• Journal of Energy Engineering
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• v.19 no.4
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• pp.228-233
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• 2010

About 55% of total energy is consumed in the industrial division. The industrial heat pump application will show magnificent energy saving effect as well as higher cost efficiency because of larger energy consuming volume of each facility and longer operation hour and higher stability against seasonal temperature change. Over 90% of dryer for industrial usage has hot wind heat source and hot wind dryer is the representative type covering 68.7% while its 30 ~ 50% lower heat efficiency causes lots of energy loss by exhaust air. Re-usage of exhaust air can improve energy efficiency of dryer because 68% heat energy or 78% of hot air lose in exhaust air. Therefore, high temperature heat pump dryer can be the best alternative. Comparing to the existing dryer with 30% ~ 50% energy efficiency, newly developing high temperature heat pump dryer will enhance energy efficiency up to 60% ~ 80% efficiency. In this paper, heat pump system for high temperature was designed, constructed and tested. The results have shown that system COPh is estimated as 3.3.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.5
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• pp.243-254
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• 2005

Soft real-time applications such as multimedia feature highly variable processor requirements and probabilistic guarantees on deadline misses, meaning that each task in the application meets its deadline with a given probability. Thus, for such soft real-time applications, a system designer may want to improve the system utilization by allocating to each task a processor time less than its worst-case requirement, as long as the imposed probabilistic timing constraint is met. In this case, however, we have to address how to schedule jobs of a task that require more than (or, overrun) the allocated processor time to the task. In this paper, to address the overrun problem, we propose an overrun control method, which probabilistically controls the execution of overrunning jobs. The proposed overrun control method probabilistically allows overrunning jobs to complete for better system utilization, and also probabilistically prevents the overrunning jobs from completing so that the required probabilistic timing constraint for each task can be met. In the paper, we show that the proposed method outperforms previous methods proposed in the literature in terms of the overall deadline miss ratio, and that it is possible to synthesize the scheduling parameters of our method so that all tasks can meet the given probabilistic timing constraints.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.4
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• pp.33-41
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• 2006

RSA cryptosystem is of great use in systems such as IC card, mobile system, WPKI, electronic cash, SET, SSL and so on. RSA is performed through modular exponentiation. It is well known that the Montgomery multiplier is efficient in general. The critical path delay of the Montgomery multiplier depends on an addition of three operands, the problem that is taken over carry-propagation makes big influence at an efficiency of Montgomery Multiplier. Recently, the use of the Carry Save Adder(CSA) which has no carry propagation has worked McIvor et al. proposed a couple of Montgomery multiplication for an ideal exponentiation, the one and the other are made of 3 steps and 2 steps of CSA respectively. The latter one is more efficient than the first one in terms of the time complexity. In this paper, for faster operation than the latter one we use binary signed-digit(SD) number system which has no carry-propagation. We propose a new redundant binary adder(RBA) that performs the addition between two binary SD numbers and apply to Montgomery multiplier. Instead of the binary SD addition rule using in existing RBAs, we propose a new addition rule. And, we construct and simulate to the proposed adder using gates provided from SAMSUNG STD130 $0.18{\mu}m$ 1.8V CMOS Standard Cell Library. The result is faster by a minimum 12.46% in terms of the time complexity than McIvor's 2 method and existing RBAs.

• KIPS Transactions on Computer and Communication Systems
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• v.7 no.10
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• pp.251-258
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• 2018

Ransomware, a malicious software that requires a ransom by encrypting a file, is becoming more threatening with its rapid propagation and intelligence. Rapid detection and risk analysis are required, but real-time analysis and reporting are lacking. In this paper, we propose a ransomware infection detection system using social big data mining technology to enable real-time analysis. The system analyzes the twitter stream in real time and crawls tweets with keywords related to ransomware. It also extracts keywords related to ransomware by crawling the news server through the news feed parser and extracts news or statistical data on the servers of the security company or search engine. The collected data is analyzed by data mining algorithms. By comparing the number of related tweets, google trends (statistical information), and articles related wannacry and locky ransomware infection spreading in 2017, we show that our system has the possibility of ransomware infection detection using tweets. Moreover, the performance of proposed system is shown through entropy and chi-square analysis.

• Journal of the Korea Society of Computer and Information
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• v.14 no.6
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• pp.1-10
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• 2009

Flash memory has the advantages of nonvolatile, low power consumption, light weight, and high endurance. This enables the flash memory to be utilized as a storage of mobile computing device such as PMP(Portable Multimedia Player). Potable device with a mass flash memory can store various multimedia data such as video, audio, or image. Typical index systems for mobile computer are inefficient to search a form of text like lyric or title. In this paper, we propose a new text index system, named EMTEX(Embedded Text Index). EMTEX has the following salient features. First, it uses a compression algorithm for embedded system. Second, if a new insert or delete operation is executed on the base table. EMTEX updates the text index immediately. Third, EMTEX considers the characteristics of flash memory to design insert, delete, and rebuild operations on the text index. Finally, EMTEX is executed as an upper layer of DBMS. Therefore, it is independent of the underlying DBMS. We evaluate the performance of EMTEX. The Experiment results show that EMTEX can outperform th conventional index systems such as Oracle Text and FT3.