• Journal of the Korea Society of Computer and Information
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• v.19 no.1
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• pp.77-84
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• 2014

In this paper, we propose the hierarchical network synchronization scheme that is backward compatible for the existing commercial system, efficient for total system performance, and whose hardware modification is minimized. This system performance is, the relationship among bandwidth efficiency, complexity and MODEM performance, and superiority of network system applicability. The proposed structure can remedy the high hardware complexity and the lower accuracy of network sychronization that the existing satellite communication terminal system in the star network based on TDM/MF-TDMA of DVB-S2/RCS standards has. Besides, It has high efficiency in view of cost and system performance if the system designed for satellite broadcast requires system upgrade. In the body section, its hardware complexity and system performance of the proposed algorithm is analysed theoretically and treated with the related parameters(symbol rate, spreading factor, etc.) and the BER performance of control channel through the computer simulation for its verification that it can be applied for communications system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.312-317
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• 2011

In this paper, we studied the frequency hopping(FH) performance on the FH radio communication system via M&S of initial synchronization architecture. It is difficult to test the synchronization performance on the real FH communication environment. Thus, we have modeled the synchronization system similar to the real radio communication structure, and simulated the optimum correlation value and the synchronization performance on AWGN channel. As the result, we could obtain the thresholds of correlation synchronization and the FH synchronization performance under the low SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10A
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• pp.853-858
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• 2003

In the EUROCOM communication system, it defines frame structures as data rate. each frame includes a synchronization bit as frame alignment signal. In my paper proposes a FAS detector for determining state of synchronization as compare received data with FAS pattern, also presents a new detection method for synchronization secession which can decide acquisition state of synchronization with searching a synchronization channel through entire channels in frame.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.161-174
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• 1996

Addressed in this paper is performance analysis of the maximum-likelihood code acquisition technique for slotted-mode preamble search in the CDMA reverse link. The probabilities of detection, miss, and false alarm are derived analytically for a multiple $H_{1}$ cell case in a frequency-selective Rayleigh fading channel, based on the statics of the CDMA noncoherent demodulator output. the probability density function of the decision variable consisting of successive demodulator outputs is also derived by considering the fading characteristics of the received signal for both single and dual antenna cases. The performance of the code acquisition technique is evaluated numerically with an emphasis on investigating the effects of post-detection integration, fading rate, and antenna diversity on the detection performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.1
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• pp.49-56
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• 2006

In this paper, to overcome the effect of nonlinear power amplifier, CE-CPSK(Constant Envelope Continuous Phase Shift Keying)modulation method which has the constant envelope and continuous phase characteristics is proposed. The code acquisition performances of the CE-CPSK modulated system and BPSK system are analyzed. And the performance is evaluated in terms of mean acquisition time and detection probability with the output backoff of the amplifier in multiuser environment. Results performed in a channel having a high degree of AM nonlinearity(AM-to-AM conversion), have shown that the CE-CPSK signal, when passed through class C-nonlinear Amplifier, has a spectrum with greatly reduced sidelobes compared to the conventional BPSK signal. The code acquisition performance of a CE-CPSK modulation system is better than that of BPSK system with nonlinear amplified multiuser environments.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.255-263
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• 2012

In this paper, the performance evaluation results of the timing synchronization schemes are presented for aeronautical mobile airport communication systems (AeroMACS). AeroMACS, which is based on IEEE 802.16e mobile WiMAX standard, uses the aeronautical frequency band of 5GHz with the bandwidth of 5MHz. The simulation model of AeroMACS is constructed and the evaluation for the timing synchronization performance is performed with the various channel models such as apron (APR), runway (RWY), taxiway (TWY), and park (PRK).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.53-58
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• 2007

OFDM (orthogonal frequency division multiplexing) is an effective modulation technique for high speed transmission over fading channels. However, it has a high bit error rate in the receiver if there is an error on frame synchronization because of phase rotation. A coherent OFDM system has to acquire exact timing synchronization of fraction and integer sampling positions. When a sampling offset exist the performance of a receiver will be degraded severely. In this paper, we propose an algorithm that acquires the fractional sampling offset in OFDM systems. This scheme compares the channel impulse responses with the early and late sampled signals having 0.5 sample offset from the estimated sampling positions by correlation with the received and training samples. Its performance is verified by computer simulations in multipath channels.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.281-282
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• 2010

CMMB(China Multimedia Mobile Broadcasting)는 중국에서 개발된 이동 방송 시스템이다. CMMB는 시간 동기와 주파수 동기를 획득하기 위해 프레임에 포함된 두 개의 동기 신호와 OFDM 심볼을 이용한다. 이는 OFDM 심볼의 연속파일럿과 분산 파일럿을 이용하는 기존의 이동 방송시스템과 달리 CMMB를 위한 특화된 동기 알고리듬이 필요하다. 이에 본 논문은 CMMB의 프레임 구조에 적합한 시간 동기 알고리듬에 대하여 연구하였다. 제안 알고리듬은 CMMB의 동기신호를 이용하여 상관값을 구한 후 1차와 2차로 나누어 경계값을 초과 하는 값을 검색하여 프레임의 시작점으로 추정한다. 제안된 알고리듬은 컴퓨터 시뮬레이션으로 검증하였으며 다중 경로 상황에서도 우수한 성능을 보인다.

• Journal of Broadcast Engineering
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• v.13 no.6
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• pp.930-940
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• 2008

This paper proposes a prototype realization of multi-view HD video transport system with synchronized multiplexing over IP networks. The proposed synchronized multiplexing considers the synchronization during video acquisition and the multiplexing for the interactive view-selection during transport. For the synchronized acquisition from multiple HDV camcorders through IEEE 1394 interface, we estimate the timeline differences among MPEG-2 compressed video streams by using global time of network between the cameras and a server and correct timelines of video streams by changing the time stamp of the MPEG-2 system stream. Also, we multiplex a selected number of acquired HD views at the MPEG-2 TS (transport stream) level for the interactive view-selection during transport. Thus, with the proposed synchronized multiplexing scheme, we can display synchronized HD view.

• Information and Communications Magazine
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• v.14 no.3
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• pp.65-74
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• 1997

본 고에서는 IS-95A 방식의 CDMA PCS 시스템과 호환되는 업무용 혹은 가정용 CT 구현을 위한 방안에 관하여 논의한다. 이를 위해 CT시스템의 CDMA 물리동기 및 프레임 동기를 획득하는 방안과 PCS/CT 이중모드의 효과적인 운용 방안을 구체적으로 제시한다. 설계의 접근방식으로는 동기방식을 위주로 하였으나 비동기방식에 대해서도 논의하였다. 제안되는 CT 시스템은 주파수 재활용도를 높이는 측면에서 Upbanded IS-95A PCS 시스템의 스펙트럼 상에서 동작하고 PCS 단말내의 H/W 통신 모듈을 변형없이 그대로 사용하므로 개발기간을 단축시키고 PCS 망과의 간섭을 최소화시킬 수 있을 것으로 기대된다.