• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.369-372
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• 2003

This paper describes a design of OFDM (Orthogoanl Frequency Division Multiplexing) based wireless LAN system receiver, defined in IEEE 802.11a standards. Because OFDM system uses several orthogonal sequence sets, it ran avoid selective fading of fast data transfer problem when it is used with error correction code. But if the receiver is not synchronized, the orthogonal of between sub-ralliers will be destroyed and the data interruption will be generated. So it makes error property get worse very murk. For improving the noise error, we use the relationship of phasor between sub-carriers and make system synchronization using one tab equalizer. The designed OFDM block is described by Verilog HDL for the efficient and small size hardware. And we preform the functional verification and evaluation using the vector of standards.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.806-813
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• 2009

This paper presents a modem chip design for high-speed wireless communications. Among the high-speed communication technologies, we design the UWB (Ultra-Wideband) modem SoC (System-on-Chip) Chip based on a MB-OFDM scheme which uses wide frequency band and gives low frequency interference to other communication services. The baseband system of the modem SoC chip is designed according to the standard document published by WiMedia. The SoC chip consists of FFT/IFFT (Fast Fourier Transform/Inverse Fast Fourier Transform), transmitter, receiver, symbol synchronizer, frequency offset estimator, Viterbi decoder, and other receiving parts. The chip is designed using 90nm CMOS (Complementary Metal-Oxide-Semiconductor) procedure. The chip size is about 5mm x 5mm and was fab-out in July 20th, 2009.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4C
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• pp.241-253
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• 2011

In this paper, a CFNC (Complex Field Network Coding) scheme is presented, which focuses on improving transmission efficiency by reducing time slots that are needed to exchange data frames. Conventional CFNC scheme has the advantage of minimizing the number of time slots required for information exchanges. However, there exists serious performance deterioration because the transmit signals are interfered with each other. Moreover, when CFNC scheme is applied, the estimation and compensation performance of fine frequency offset severely deteriorates due to the multiple frequency offsets in received signal of relay node. In order to overcome these critical problems, we propose an improved CFNC scheme with modified maximum likelihood decision method which uses uplink transmit diversity. Also, we propose an enhanced fine frequency offset estimation method and a corresponding compensation method to deal with the multiple frequency offsets. Corresponding simulation results verify that the proposed methods are able to effectively solve the problems of CFNC scheme.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.4
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• pp.307-313
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• 2019

The traveling wave tube amplifier (TWTA), which can be applied to the Ka-band millimeter-wave multi-mode seeker, consists of an high voltage power supply(HVPS), a grid modulator, a command and control, and an RF assembly. We designed a power supply that generates a -17.9 kV high voltage by synchronizing the pulse repetition frequency(PRF) and power supply switching frequency(i.e. synchronization frequency), and a high-speed grid-switching modulator for RF pulse modulation. The TWTA, which is fabricated through miniaturization with a volume of 3.18 L, has high pulse switching characteristics of up to 18.5 ns. The maximum rise/fall time of the grid on/bias signal and peak power is more than 564.9 W. Moreover, an excellent spurious performance of -68.4 dBc or less was confirmed within the range of PRF and PRF/2.

• ETRI Journal
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• v.35 no.3
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• pp.406-413
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• 2013

In this paper, an orthogonal frequency division multiple access (OFDMA)-based minimum end-to-end delay (MED) distributed routing scheme for mobile backhaul wireless mesh networks is proposed. The proposed scheme selects routing paths based on OFDMA subcarrier synchronization control, subcarrier availability, and delay. In the proposed scheme, OFDMA is used to transmit frames between mesh routers using type-I hybrid automatic repeat request over multipath Rayleigh fading channels. Compared with other distributed routing algorithms, such as most forward within radius R, farthest neighbor routing, nearest neighbor routing, and nearest with forwarding progress, simulation results show that the proposed MED routing can reduce end-to-end delay and support highly reliable routing using only local information of neighbor nodes.

• Journal of Institute of Control, Robotics and Systems
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• v.10 no.3
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• pp.239-248
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• 2004

Optical coherence tomography(OCT) is high resolution imaging system which can see the cross section of microscopic organs in the living tissue. In this paper, we analyze the relation between the light source and the resolution of modulated signal in Michelson interferometer. We construct 1-D OCT signal processing hardware such as amplifiers, filters, and demodulate electronic signals from the photo detector. In order to get 2-D OCT image, the synchronization among optical delay line, sample stage and A/D converter is dealt with. In experiments, we verify analog and digital signal processing blocks which apply to the stacks of glasses. Finally we aquire high resolution 2-D OCT image with respect to the onion tissue. We expect that this result can be applied to the medical instrument through performance improvement.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.409-412
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• 2002

The delta modulation used for controlling the speed of an induction motor has high peak of harmonic spectrum at low speed range causing acoustic noises in the induction motor. This paper proposes to suppress the harmonics by synchronizing the reference signal with the hysteresis windows for controlling the distribution of the switching frequency. As a result we can decrease the peak of harmonic spectrum. The simulation results show that the peak spectrum of harmonics can be reduced up to 60%.

• JSTS:Journal of Semiconductor Technology and Science
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• v.9 no.4
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• pp.181-186
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• 2009

This paper presents an efficient synchronizer architecture using a common autocorrelator for Digital Video Broadcasting via Satellite, Second generation (DVB-S2). To achieve the required performance under the worst channel condition and to implement the efficient H/W resource utilization of functional synchronization blocks, we propose a new efficient common autocorrelator structure. The proposed architecture can decrease about 92% of multipliers and 81% of adders compared with the direct implementation. Moreover, the proposed architecture has been thoroughly verified in XilinxTM Virtex IV and R&STM SFU (Signaling and Formatting Unit) broad-cast test equipment.

• IEMEK Journal of Embedded Systems and Applications
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• v.3 no.4
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• pp.207-217
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• 2008

A novel scheme is presented for Traffic Encryption Key (TEK) rekeying with low communication overhead for an Internet Protocol television (IPTV) conditional access system over Data-Over-Cable Service Interface Specifications (DOCSIS) 3.0. The proposed scheme utilizes the DOCSIS system synchronization for periodic TEK rekeying instead of a conventional TEK rekeying negotiation process. Analysis shows that the communication overhead is only 0.012 Kbps when TEK rekeying frequency is 1 second.

• ETRI Journal
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• v.37 no.1
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• pp.186-196
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• 2015

In resource-constrained, low-cost, radio-frequency identification (RFID) sensor-based mobile ad hoc networks (MANETs), ensuring security without performance degradation is a major challenge. This paper introduces a novel combination of steps in lightweight protocol integration to provide a secure network for RFID sensor-based MANETs using error-correcting codes (ECCs). The proposed scheme chooses a quasi-cyclic ECC. Key pairs are generated using the ECC for establishing a secure message communication. Probability analysis shows that code-based identification; key generation; and authentication and trust management schemes protect the network from Sybil, eclipse, and de-synchronization attacks. A lightweight model for the proposed sequence of steps is designed and analyzed using an Alloy analyzer. Results show that selection processes with ten nodes and five subgroup controllers identify attacks in only a few milliseconds. Margrave policy analysis shows that there is no conflict among the roles of network members.