• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.689-692
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• 2008

WAVE based on OFDM is made for vehicle to vehicle wireless communication. Its performance is decreased by continual timing delay in multipath fading channels after starting initial timing synchronization. In this paper, the tracking algorithm that synchronizes symbol timing is proposed to continually compensate additional timing delay. Computer simulation of the proposed algorithm is performed in the worst communication environment that applies to maximum timing delay. Computer simulation shows that the proposed algorithm can improve the system performance in various channel conditions.

• Journal of Advanced Navigation Technology
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• v.5 no.1
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• pp.45-53
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• 2001

We present the frame synchronization scheme using the FFT window position restoration algorithm appropriate for wireless OFDM systems under multipath fading environment. From the restoration of the synchronization parameters of previous several frames, the algorithm can extract the synchronization parameters for the next frames. To analyze the performance of the proposed algorithm, we compare the probability of synchronization failure under time and frequency domains, respectively. From the simulation results, one can see that the algorithm in the time domain shows better performance than in the frequency one, for the $E_b/N_o$ of 6.0dB or more.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.135-138
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• 2008

The existing protocol which processes sequentially synchronization has the problem where synchronization tasks which are requested subsequently from multiple client. Should be waited for a long time. In this paper, we propose a implementation of concurrent synchronization protocol that is capable of reducing the waiting time. If there are no update conflicts among different synchronization tasks, the proposed protocol synchronizes using the multi-queue based on the round-robin scheme, in order to reduce the waiting time.

• The KIPS Transactions:PartC
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• v.9C no.6
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• pp.953-960
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• 2002

Rel-time application programs have constraints which need to be met between media-data. It is client-leading synchronization that is absorbing variable transmission delay time and that is synchronizing by feedback control and palyout control. It is the important factor for playback rate and QoS if the buffer level is normal or not. This paper, The method of maintenance buffer normal state transmits in multimedia server by appling feedback of filtering function. And synchronization method is processing adaptive playout time for smooth presentation without cut-off while media frame is skip. When audio frame which is master media is in upper threshold buffer level we decrease play out time gradually, low threshold buffer level increase it slowly.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.1
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• pp.141-146
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• 2011

The GIS service has to provide latest spatio-temporal data for the effective service. The two-way synchronization scheme collects updated spatio-temporal data in the field and synchronizes with a server by using the wireless network. However, since the two-way synchronization scheme processes sequentially synchronizing work of clients, it has the problem that the synchronization of multiple clients takes long time. In this paper, we propose the concurrent synchronizations scheme based on the multi-queue in order to reduce the waiting time of multiple clients. We also build both schemes and evaulate the performance test. The results show that the proposed scheme reduce the waiting time by 31%.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.621-624
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• 2017

In this paper, we propose a protocol synchronizing to packet trains in a underwater acoustic networks with limitations such as long propagation delay, low data rate, high packet loss. The proposed protocol employs an one-way communication scheme to calculate packet arrival time differences of consecutively transferred packets and minimizes uncertain variation effect of long propagation delay. Simulation results shows the superiority of our protocol, compared with a previously proposed one under the given network conditions.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.88-89
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• 2013

본 논문은 영구자석 동기전동기의 동적 특성 개선과 토크 리플 저감 기법을 제안한다. 제안하는 방법은 영구자석 동기전동기의 인가전압과 토크의 관계를 수학적인 분석을 통해 유효 벡터 인가 시간을 결정하는 기법이다. 결정된 유효벡터 인가 시간과 동기전동기의 토크 오차와의 관계를 이용하여 최종적인 지령전압벡터를 계산한다. 계산된 지령전압벡터는 영구자석 동기전동기의 빠른 응답성과 우수한 정상상태 특성을 보인다. 시뮬레이션을 이용하여 제안하는 영구자석 동기기 토크 제어 알고리즘의 타당성을 확인한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.473-478
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• 2008

WAVE is a short-to-medium range communication standard that supports both public safety and private operations in roadside-to-vehicle and vehicle-to-vehicle communication environments. The core technology of physical layer in WAVE is orthogonal frequency division multiplexing (OFDM), which is sensitive to timing synchronization error. Besides, minimizing the latency in communication link is an essential characteristic of WAVE system. In this paper, a robust, low-complexity and small-latency timing synchronization algorithm suitable for WAVE system and its efficient hardware architecture are proposed. The comparison between proposed algorithm and other algorithms in terms of computational complexity and latency has shown the advantage of the proposed algorithm. The proposed architecture does not require RAM (Random Access Memory) which can affect the pipe lining ability and high speed operation of the hardware implementation. Synchronization error rate (SER) evaluation using both Matlab and FPGA implementation shows that the proposed algorithm exhibits a good performance over the existing algorithms.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.10a
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• pp.577-586
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• 1998

본 논문에서는 RLCG 전송선로를 가진 Chua 회로에서의 카오스 동기화 방법에 대하여 연구하였다. 두 개의 동일한 Chua 회로에 전송 선로를 두어 RLCG 전송로를 구성한 후 송신부와 전송선로 사이는 구동-결합 동기 이론을, 전송선로와 수신부 사이는 결합 동기 이론을 적용한 동기화 방법을 제시하였으며, RLCG 전송 선로를 가진 Chua 회로의 카오스 동기화는 전송 선로의 L과 C 영향에 의한 시간 지연이 있는 일반화된 동기화가 이루어짐을 확인하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.11b
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• pp.239-242
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• 1999

본 논문에서는 8VSB수신기가 다중경로신호에 따른 성능이 나쁜 것에 대한 원인 분석과 나아가 개선책을 제시하기 위해 다중경로 신호가 디지털 지상파 TV의 수신성능에 미치는 영향에 대해 수신단의 STR(Symbol Timing Recovery)과 등화기를 중심으로 분석한다. 첫째 등화기의 성능 분석을 위해 에코의지연시간이 7.5 $\mu$sec일 때 시불변 환경에서 전산 모의 실험을 하였다. 등화기 수렴후의 에로 레벨에 따른 TOV(Threshold of Visibility) S/N(Signal to Noise)를 구해보면 호주의 실험실 측정과는 달리 0dB에서도 S/N이 26dB 정도이면 등화기는 안정적으로 수렴한다. 둘째 세그먼트 동기 복원을 세그먼트 싱크 필터(Segment Sync:+1, +1. -1, -1)를 사용했을 때 짧은 시간 지연 에코와 긴 시간 지연 에코에 대해 S 커브를 보면 짧은 시간 지연에코에서는 심볼 타이밍이 어긋났으며 긴 시간 지연 에로에서는 문제가 없이 타이밍 동기가 된다. 셋째 짧은 시간 지연 에코신호가 있을 때 세그먼트 동기 복원과 등화기를 연동한 전산 모의 실험을 하여 에코의 영향을 분석하고 FSE(Fractionally Spaced Equalizer) 등화기 사용에 따른 장점을 분석한다.