• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2005.11a
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• pp.109-112
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• 2005

ATSC 지상파 DTV 시스템에서 심볼 타이밍 동기 성능 개선을 위한 알고리즘을 제안한다. 일반적으로 심볼 타이밍 동기를 위해 사용되는 가드너 방법은 다중 경로 페이딩 환경에서 성능이 좋지만 지터에 의해 성능 열화가 발생한다. 지터량는 루프 필터 대역폭이 작을수록 작아지지만, 수렴속도는 느려지게 된다. 수렴속도는 빠르면서 수렴 후 지터량를 감소시키기 위해 일정시간마다 루프필터의 출력 값을 평균하고 이 평균값을 이용하여 옵셋량을 추정한 후 추정된 옵셋의 변화율에 따라 루프 필터의 대역폭을 줄여 지터의 크기를 줄이는 알고리즘을 제안한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.74-77
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• 2011

본 논문에서는, 지상파 3D HDTV 방송 전송을 위한 VSB(Vestigial Side Band) 변조방식의 심벌 타이밍 및 반송파 동기부 구조를 제안하고 그 성능을 검증해 보았다. 제안하는 동기부의 동작은 다음과 같다. 먼저 반송파 주파수 옵셋에 독립적인 심벌 타이밍 복구 알고리즘으로 타이밍 동기를 이룬다. 그리고 제안하는 프레임 검출 방법으로 프레임의 시작점을 알아내고, 반송파 주파수 옵셋 복구에 필요한 훈련 열을 얻어낸다. 마지막으로, 얻어진 훈련 열을 이용하여 반송파 주파수 옵셋과 반송파 위상 옵셋을 복구한다. 컴퓨터 모의실험 결과, 제안하는 동기부 구조는 이상적으로 동기를 이루었을 때의 BER(bit error rate)성능과 근접한 성능을 나타내었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.815-820
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• 1998

A new coding algorithm which has spectrum notches at the DC and Nyquist Frequency for maximizing the effect of the in-band pilot insertion in order to make the symbol timing or carrier recovery easy is proposed. It is shown that this algorithm uses one encoder and gives the similar spectrum characteristics to that of the existing OF00 code which uses two encoder. In this paper, the proposed new coding algorithm is explained andits spectrum characteristics is compared with the of OF00 code using computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.516-522
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• 2010

In this paper, the carrier frequency offset estimator is proposed for the China multimedia mobile broadcasting (CMMB). The fractional carrier frequency offset is estimated by utilizing the cyclic prefix in each CMMB symbol. In addition, the integer carrier frequency offset can be estimated with the synchronization signal in every CMMB frame. The proposed estimator is the most suitable for the frame structure of CMMB. It shows a prominent performance even in timing offset and multipath conditions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.687-694
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• 1999

In this paper, to draw out the parameter of synchronization for ADSL(Asymmetric Digital Subscriber Line) chip design, we analyze the performance of STR(Symbol Timing Recovery) and frame synchronization with computer simulation. We analyze and design PLL(Phase Lock Loop) loop for ADSL. As a result, we obtained the optimum parameter of STR to design ADSL chip. Also, when performed frame synchronization with several algorithm, we analyzed the performance of FER(Frame Error Rate) and the effect of frame offset with computer simulation.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.3
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• pp.9-14
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• 1998

The speech recognition on long vowels are carried out by electric circuits. A level compressor is able to transform the wave of voice to serial pulses. The obtained pulses have informations to distinguish the vowels. The sampling of the pulses is carried out by the register which picks up a series of serial signals in a pitch of a vowel as an unit. The timing control pulses such as sampling pulses are generated by using peak pulses in the speech wave. The parallel data in the register assign the phonetic symbol by means of the decision making circuit which carries out the IF-THEN rule.

• ETRI Journal
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• v.35 no.4
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• pp.710-713
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• 2013

We propose a new space-time block coding (STBC) for asynchronous cooperative systems in full-duplex mode. The orthogonal frequency division multiplexing (OFDM) transmission technique is used to combat the timing errors from the relay nodes. At the relay nodes, only one OFDM time slot is required to delay for a pair-wise symbol swap operation. The decoding complexity is lower for this new STBC than for the traditional quasi-orthogonal STBC. Simulation results show that the proposed scheme achieves excellent performances.

• Journal of Communications and Networks
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• v.15 no.2
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• pp.191-197
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• 2013

In this paper, a mobile relay station (MRS) for vehicles with a beamforming antenna is considered to increase the reliability of the transmission link, particularly for the MRS at the cell boundary. A cell searching and direction-of-arrival estimation method for an MRS with a uniform linear array is proposed for OFDM-based cellular systems in a multipath environment, even with the existence of the symbol timing offsets and carrier frequency offsets. The performance of the proposed method is evaluated by computer simulation using the standard profile of IEEE 802.16e.

• ETRI Journal
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• v.43 no.6
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• pp.978-990
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• 2021

This article presents techniques for improved estimation of symbol timing offset (STO) and carrier frequency offset (CFO) for dual-polarization (DP) orthogonal frequency division multiplex (DP-OFDM) systems. Recently, quaternion multiple-input multiple-output OFDM has been proposed for high spectral efficiency communication systems, which can flexibly explore different types of diversities such as space, time, frequency, and polarization. This article focuses on synchronization techniques for DP-OFDM systems using a cyclic prefix, where the application of quaternion algebra leads to new improved estimators. Simulations performed for DP system methods show faster reduction of STO estimator variance with a double-slope line in the logvariance line versus signal-to-noise ratio (SNR) plot compared with singlepolarization (SP) counterparts, and simulations for CFO estimates show a 3-dB gain of DP over SP estimates for same SNR values defined, respectively, for quaternion-valued or complex-valued signals. Cramer-Rao bounds for STO and CFO are derived for the synchronization methods, correlating with the observed gains of DP over SP OFDM systems.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.579-581
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• 2020

최근 DOCSIS 3.1 시스템에서 주파수 이용효율향상을 위해 상향과 하향 신호를 동일대역으로 동시전송하는 DOCSIS3.1 FDX 시스템이 연구되고 있다. 동일대역을 사용할 경우 DOCSIS 3.1 FDX시스템의 하향 송신신호는 높은 전력을 가진 신호로 feedback되어 상향송신기로부터 전송된 낮은 전력의 상향 수신신호와 결합하여 상향수신기에 수신되어진다. 이러한 결합신호는 상향신호와 하향신호간의 심볼타이밍 옵셋이 정확하게 일치하지 않으면 상향신호 성능을 열화시키는 원인이 된다. 본 논문에서는 이러한 문제를 해결하기 위해 주파수영역에서 DOCSIS 3.1 FDX시스템의 상하향신호간 심볼 타이밍 옵셋으로 인한 성능 열화 개선 알고리즘을 제시하고 모의실험을 통해 성능열화를 개선할 수 있음을 보인다.