• 전자공학회논문지 IE
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• v.47 no.3
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• pp.35-40
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• 2010

In this paper, we propose an algorithm to improve the precision of initial carrier-frequency offset estimation for multiband-OFDM (MB-OFDM) UWB system which is considering the quantization-noise effect. In the general OFDM system, the two adjacent and repeated preamble symbols are used for the initial carrier-frequency synchronization while the performance of the frequency-offset estimation is bounded by quantization effect generated from analog-to-digital conversion at the receiver. This paper proposes a method in which one-symbol interval between two adjacent preamble symbols for the initial frequency synchronization is extended to multiple-symbol interval between non-adjacent symbols in an extent that phase ambiguity does not occur. In this paper, we also present '6' as optimal multiple symbol interval for the MB-OFDM system with 30 preamble symbols on 3-band hopping and with 4-bit A/D conversion at the receiver. Under the channel environments for the MB-OFDM UWB system, the simulation results show that the proposed estimation algorithm can achieve the initial estimation in offset precision less than 5 ppm.

• Journal of the Korean Vacuum Society
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• v.20 no.3
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• pp.182-188
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• 2011

Polysilazane and polymethylsilazane based precursor films were deposited on Si-substrate by spin-coating, subsequently annealed at $150{\sim}850^{\circ}C$, and characterized. Structural analysis, shrink, compositional change, etch rate, and gap-filling were observed. Annealing the precursor films led to formation of spin-on dielectric films. C-containing precursor films showed that less loss of N, H, and C while less gain of O than that of C-free precursor films at $400^{\circ}C$, but more loss of N, H, and C while more gain of O at $850^{\circ}C$. Thus polysilazane based precursor films exhibited less reduction in thickness of 14.5% than silazane based one of 15.6% at $400^{\circ}C$ but more 37.4% than 19.4% at $850^{\circ}C$. FTIR indicated that C induced smaller amount of Si-O bond, non-uniform property, and lower resistance to chemical etching.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.673-676
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• 2003

현재 무선 인터넷 컨텐츠는 유선 컨텐츠와 호환이 되지 않으며 다양한 종류의 무선 마크업 언어들로 구성되어 있어 무선 컨텐츠를 재구축해야 하는 문제점이 있다. 본 논문에서는 이를 해결하기 위해 유선 컨텐츠를 재사용하는 방안으로 XML 기반의 유무선 컨덴츠 변환기를 설계한다. 컨텐츠 변환의 중간 표준포맷으로 XML 문서를 생성하므로 새로운 언어로의 변환을 고려할 때 해당 프리젠테이션 변환모듈만 추가시키면 확장 가능하므로 유지보수가 쉽고 효율적인 변환이 가능하다. 따라서 새로운 표준과 기술 변화에 대응이 용이하며 또한 유선 컨텐츠의 재사용으로 인해 개발비용이 절감되고 개발기간이 단축되므로 빠른 무선 인터넷 시장 진입이 가능해진다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10A
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• pp.776-783
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• 2009

Current-cut circuit is an effective method to obtain low power consumption in wireless communication systems as high speed OFDM. For the operation of current-mode FFT LSI with analog signal processing essentially requires current-mode serial-to-parallel/parallel-to-serial converter with multi input and output structure. However, the Hold-mode operation of current-mode serial-to-parallel/parallel-to-serial converter has unnecessary power consumption. We propose a novel current-mode serial-to-parallel/parallel-to-serial converter with current-cut circuit and full chip simulation results agree with experimental data of low power consumption. The proposed current-mode serial-to-parallel/parallel-to-serial converter promise the wide application of the current-mode analog signal processing in the field of low power wireless communication LSI.

• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1441-1456
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• 1998

The concept of a hyperpresmtation, as an extension of a hypermedia, is the presentation in which time-varying multimedia presentations are dynamically linked together and a hyperlink's context can be changed over time at any time during a continuous presentation. Problems caused by integrating the hyperpresentation into an existing multimedia system which handles a sequential presentation only are, how to describe the hyperprcsentation, how to set up a hyperlink on a continuous media, and how to check the consistency of the synchronized presentations. In this paper. a new synchronization description method for the hyperpresentation and a method for setting a hyper link on a continuous media during" presentation are proposed after havin!; SHrvey of existing methods, The proposed method deals with only the DC value in a stream ut a DCT based compressed data for checking a condition of te link. Finally, the method for checking the consistency of mixed presentations before actual play of the hnlerpresentation is described. Proposed methods are implemented on MuX(Multimedia IO Server) where a sample scenario is tested.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.74-81
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• 2007

In this paper, CMOS analog-to-digital converter (ADC) with a 6-bit 1GSPS at 1.8V is described. The architecture of the proposed ADC is based on a folding type ADC using resistive interpolation technique for low power consumption. To reduce the power consumption, a folder reduction technique to decrease the number of folding blocks (NFB) by half of the conventional ones is proposed. further, a novel layout technique is introduced for compact area. With the clock speed of 1GSPS, the ADC achieves an effective resolution bandwidth (ERBW) of 500MHz, while consuming only 60mW of power. The measured INL and DNL were within $\pm$0.5 LSB, $\pm$0.7 LSB, respectively. The measured SNR was 34.1dB, when the Fin=100MHz at Fs=300MHz. The active chip occupies an area of 0.27$mm^2$ in 0.18um CMOS technology.

• The Journal of the Korea institute of electronic communication sciences
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• v.3 no.4
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• pp.260-265
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• 2008

The arc-fault occurring in the customer system becomes the direct cause of electric fire. However, it is very difficult to identify the arc-fault using the existing fault detection mechanism because the magnitude of the fault current is very small. Accordingly, this paper analyzes the causes of arc fault and designs the basic detection mechanism of arc fault. And then, it proposes an signal processing-based arc-fault determination methodology which can enhance the of accuracy of the arc-fault determination by applying DFT/DWT to the voltage and current waveform. Finally, this paper showed the application methodology of the proposed signal processing based fault determination method by applying and analyzing DFT/DWT to an high voltage in-rush current waveform.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1402-1409
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• 2007

In this paper, we propose various types of AGC algorithms for implementing the OFDM communication systems. For the high-speed packet transmission, in this paper, we assume the OFDM system with relatively long and repeated preambles. We propose the maximum sample value counter for counting the number of maximum sample. In the maximum sample value counter, we use the buffer for the digital signal buffering. Finally, the counting value of the maximum sample value counter controls the gain control signal generator by using gain control table automatically.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.1-11
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• 2012

Recently, we have seen several implementations that virtualize the ARM architecture. Since the current ARM architecture is not possible to be virtualized using the traditional technique called "trap-and-emulation", we usually detect all virtualization sensitive instructions during the run-time of a guest kernel and emulate them virtually rather than executing them directly. The emulation for virtualization is usually implemented either by binary translation or interpretation. Our research is about how to improve the performance of emulation for virtualization based on interpretation. The interpretation usually requires a few steps: instruction fetching, instruction decoding and instruction executing. In this paper, we propose a method that decodes all virtualization sensitive instructions during the compilation time of a guest kernel and reduces the time required for interpretation during the run time of the guest kernel. Our method provides both implementation simplicity and performance improvement of emulation for virtualization based on interpretation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.69-78
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• 2017

Shannon of the 5G smartphone and Fourier of the signal processing meet in the sampling theorem (2 times the highest frequency 1). In this paper, the initial Shannon Theorem finds the Shannon capacity at the point-to-point, but the 5G shows on the Relay channel that the technology has evolved into Multi Point MIMO. Fourier transforms are signal processing with fixed parameters. We analyzed the performance by proposing a 2N-1 multivariate Fourier-Jacket transform in the multimedia age. In this study, the authors tackle this signal processing complexity issue by proposing a Jacket-based fast method for reducing the precoding/decoding complexity in terms of time computation. Jacket transforms have shown to find applications in signal processing and coding theory. Jacket transforms are defined to be $n{\times}n$ matrices $A=(a_{jk})$ over a field F with the property $AA^{\dot{+}}=nl_n$, where $A^{\dot{+}}$ is the transpose matrix of the element-wise inverse of A, that is, $A^{\dot{+}}=(a^{-1}_{kj})$, which generalise Hadamard transforms and centre weighted Hadamard transforms. In particular, exploiting the Jacket transform properties, the authors propose a new eigenvalue decomposition (EVD) method with application in precoding and decoding of distributive multi-input multi-output channels in relay-based DF cooperative wireless networks in which the transmission is based on using single-symbol decodable space-time block codes. The authors show that the proposed Jacket-based method of EVD has significant reduction in its computational time as compared to the conventional-based EVD method. Performance in terms of computational time reduction is evaluated quantitatively through mathematical analysis and numerical results.