• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1004-1011
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• 2005

In OFDM (Orthogonal Frequency Division Multiplexing) system, sampling frequency offset causes performance degradation due to increase of ICI. Sampling frequency offset can be generally estimated by correlation of the pilot signal or the known pattern within two contiguous OFDM symbol however, this method has the throughput degradation and the difficulty in applying to various OFDM systems. In this paper, we propose a new algorithm for sampling frequency offset estimation which can solve aforementioned issues. The proposed algorithm uses a single OFDM symbol to prevent throughput degradation and to apply to various OFDM-based communication systems flexibly Also, the proposed algorithm can enhance reliability by observing more number of correlations compared to the established algorithm in frequency domain. Extensive computer simulation shows that the proposed algorithm can improve the system performance in various channel conditions.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4A
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• pp.250-258
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• 2005

An initial carrier frequency offset estimation algorithm is proposed for a multi-user frequency bowing orthogonal frequency division modulation-frequency division multiple access (FH-OFDMA) system with a single preamble symbol. To mitigate the effect of the frequency offset, every mobile station needs to accurately and rapidly acquire synchronization. The proposed algorithm uses only one preamble symbol in which two kinds of subcarriers are designed for coarse and fine frequency offset estimation. The non-data aided estimation using the energy spectrum is exploited for fine offset estimation, and maximum likelihood estimation using correlation for coarse offset estimation. By combining the two estimation results, an accurate frequency offset can be estimated with a single symbol. Through simulations, the performance of the proposed algorithm is evaluated by comparing estimation error variance with a conventional method.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.357-365
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• 2009

In an OFDM system, the sampling frequency offset between the transmitter and receiver is known to cause the inter-channel interference (ICI), resulting in performance degradation. Sampling frequency offset can be generally estimated by correlation of the pilot signal within contiguous OFDM symbol. In this paper, we propose sampling frequency offset estimation schemes using various mixture of consecutive symbols. We conduct a simulation in DVB-T(2K mode) system, which shows that the proposed schemes can improve the performance of sampling frequency offset estimation by decreasing noise effect within consecutive symbols in AWGN channel model.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.109-114
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• 2009

An orthogonal frequency division multiplexing(OFDM) system is effective to bandwidth because of orthogonality of subcarriers and robust to multipath fading. However, if there is a frequency offset, we lose the orthogonality of subcarriers and that results in inter-carrier interference(ICI) which increases errors in the system. In this paper, we propose an algorithm that estimates the fine frequency offset using a correlation method in OFDM systems. This scheme compares two correlation values in different frequency offsets with opposite directions. From the difference between two correlation values we can derive a fine frequency offset estimation algorithm. Its performance is verified by computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6C
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• pp.623-628
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• 2006

This paper addresses the frequency offset estimation problem in the presence of the timing error for OFDM systems. When the timing error exists, the correlation value used for the frequency offset estimation could be reduced significantly due to the timing error, resulting in considerable degradation in estimation performance. In this paper, using the coherence phase bandwidth (CPB) and a threshold, a novel frequency offset estimation scheme is proposed and based on which, an efficient timing error estimation scheme is also proposed for the re-estimation of the frequency offset. The performance comparison results show that the proposed frequency offset estimation scheme is not only more robust to the timing error but also has less computational complexity, as compared with the conventional schemes. It is also demonstrated by simulation that theproposed timing error estimation scheme gives a reliable estimate of the timing error.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.11a
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• pp.310-312
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• 2018

In this paper, We stduy addtional consideration and method to treat carrier frquency offset on defined system parameter & requirements in IALA G1139, previous studied consecutively. We studied the method to treat carrier frequency offset by extending length of training symbol and by differential modulation. This study will publish and argue in IALA ENAV22. We will decide a method to treat carrier frequency offset from result of IALA ENAV22.

• Journal of the Korea Society of Computer and Information
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• v.18 no.10
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• pp.63-70
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• 2013

In this paper, we investigated frequency synchronization through computer simulation of digital M/W transmission system in multipath fading channel. we suggested frequency offset correction algorithm against frequency offset between transmitter and receiver, then evaluated the degree of constellation performance enhancement. From the performance evaluation, in case of large frequency offset, although adopting frequency offset correction scheme, residual frequency offset degraded system performance. As a result, according to frequency offset value between transmitter and receiver residual frequency offset affects system performance significantly. The results of this paper should be utilized for frequency synchronization criterion when frequency band of broadcasting system is rearranged.

• Journal of Broadcast Engineering
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• v.8 no.2
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• pp.146-152
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• 2003

ATSC DTV receivers use repetitive data segment syncs or Gardner algorithm as a tuning recovery circuit. Many multipath signals can induce timing-offset in the symbol timing recovery circuit using Gardner algorithm and this timing-offset shifts sampling instant to the wrong points, causing the performance of the equalizer to become nr. When many echoes exist, the optimal sampling instant will be the Point at which the main-path has a peak value. In this paper, by using channel correlation techniques, we find the optimal sampling instant, thereby compensating the timing offset and improving DTV reception performance. We analyzed the Performance enhancement of DTV receivers using the timing offset compensator.

• 기계와재료
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• v.22 no.3
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• pp.30-35
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• 2010

최근 전자소자의 제조공정에 있어서 인쇄전자를 적용하여 고가이면서 화학물질이 많이 배출되는 기존의 제조공정을 대체하기 위한 연구가 활발하게 이루어지고 있다. 인쇄전자를 적용하기 위해서는 기존 공종 대비 생산비의 절감과 대량생산을 요구하고 있으며, 그 요구를 만족시킬 수 있는 인쇄전자 기술로는 롤투롤(R2R, Roll to Roll) 인쇄방식이 대표적이라 할 수 있다. 롤투롤 인쇄방식과 그라비아(Gravure)/그라비아옵셋(Gravure offset) 인쇄방법을 적용하면 낮은 비용으로 대량의 전자소자 생산에 쉽게 접근 할 수 있다. (주)펨스는 인쇄전자 기술의 활성화를 위하여 롤투롤-그라비아/그라비아옵셋 인쇄를 적용한 인쇄전자소자용 인쇄, 코팅장비를 개발 제작하고 있다.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.177-178
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• 2018

본 논문에서는 직렬형 Hot-Swap ESS(Energy Storage System)를 구성하는 전력 변환 시스템에서 전류 센서의 옵셋 오차가 제어 성능에 미치는 영향에 대해 살펴보았다. 양방향 DC-DC 컨버터와 DC-AC 인버터에서 전류 센서 옵셋 오차의 영향에 대해 분석하고, 컴퓨터 모의 시험을 진행하여 그 특성을 파악하였다.