• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.4
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• pp.379-386
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• 2004

OFDM(orthogonal frequency division multiplexing) communications system is very attractive for the high data rate transmissionin the frequency selective fading channel. Since OFDM has high PAPR(peak-to-average power ratio), OFDM signal may be distorted by the nonlinear HPA(high power amplifier). In this paper, we propose an improved dummy sequence scheme for reducing the PAPR in OFDM communication system. This method inserts each different dummy sequence at the predefined sub-carriers fur PAPR reduction. After IFFT, the OFDM data signal with the lowest PAPR is selected to transmit. The complementary sequence is used as dummy sequence. So, it can cut down the computation time and quantity because it dose not require the peak value optimization for finding the phase rotation factor and the transmission of the side information about the rotation factor unlike the PTS method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1239-1247
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• 2003

OFDM(orthogonal frequency division multiplexing) communications system is very attractive for the high data rate transmission in the frequency selective lading channel. Since OFDM has high PAPR(peak-to-average power ratio), OFDM signal may be distorted by the nonlinear HPA(high power amplifier). In this paper, we propose the DSI(dummy sequence insertion) method for OFDM communication system. Some sub-carriers are inserted for PAPR reduction. They carry the specified dummy data sequence which are used for only PAPR reduction and do not work as side information like the conventional PTS(partial transmit sequence) or SLM(selected mapping) method. We use the complementary sequence and the combination of the correlation sequence as the dummy sequence. Flipping technique is used for the DSI method to get the effective PAPR reduction. It is important that BER of the proposed method is independent of the damage of the dummy data sequence. And DSI method has better spectral efficiency than the conventional block coding. On the other hand, threshold PAPR method is applied to cut down the processing time. However, this DSI method is not better than the conventional PTS method in the respect of the PAPR reduction performance. The DSI method includes the threshold PAPR lower than the PAPR of the OFDM signal, reduces the processing time and improves the BER performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4A
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• pp.288-295
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• 2005

OFDM communications system is very attractive for the high data rate wireless transmission. However, it may be distorted in the nonlinear HPA since OFDM signal has high PAPR. So, a new SLM method using dummy sequence is studied for reducing the PAPR, and we call it DSI-SLM method. Unlike the conventional SLM method using the phase rotation, dummy sequences for PAPR reduction are assigned at the predefined sub-carriers. After IFFT, the OFDM data signal of the lowest PAPR is selected to transmit. So, it can cut down the computational complexity because it does not require the transmission and demodulation process of side information about the phase rotation. This proposed method can solve the time delay problem so that PAPR reduction can be made in real time processing.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.6
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• pp.2201-2216
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• 2015

Peak to average power ratio (PAPR) is one of the main imperfections in the broadband communication systems with multiple carriers. In this paper, a new crest factor reduction (CFR) scheme based on interleaved phase sequence called Dummy Sequence Insertion Enhanced Partial Transmit Sequence (DSI-EPTS) is proposed which effectively reduces the PAPR while at the same time keeps the total complexity low. Moreover, the prototype of the proposed scheme in field programmable gate array (FPGA) is demonstrated. In DSI-EPTS scheme, a new matrix of phase sequence is defined which leads to a significant reduction in hardware complexity due to its less searching operation to extract the optimum phase sequence. The obtained results show comparable performance with slight difference due to the FPGA constraints. The results show 5 dB reduction in PAPR by applying the DSI-EPTS scheme with low complexity and low power consumption.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.11 s.102
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• pp.1147-1154
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• 2005

In this paper, we propose some PAPR(Peak to Average Power Ratio) reduction methods using WHT(Walsh Hadamard Transform) to reduce high PAPR generated in OFDM system because of multi carrier modulation. These proposed methods are the methods which has additional PAPR reduction performance without a loss of bandwidth efficiency and a large increment of calculation complexity than common PAPR reduction methods by combining the WHT with some common methods. In this paper, we propose two PAPR reduction methods made by combining a SLM(Selective Mapping) and DSI(Dummy Sequence Insertion) with a WHT. From simulation result, we can find that the PAPR reduction methods using a WHT can get about 1 dB additional PAPR reduction performance than common PAPR reduction methods; they are SLM and DSI. And, because our proposed methods have not only PAPR reduction effect, but also frequency diversity effect, more stabile data transmission is possible in nonlinear HPA and multipath fading channel.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.433-438
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• 2020

Nodes on a data communication path in a wireless network emit electro-magnetic waves whenever they transmit packets; thus, the path can be exposed and identified with capturing and analyzing a sequence of the signals emitted there. One of countermeasures against a malicious eavesdropper is to let certain nodes mimic the nodes on the data path in sending dummy packets. In this paper we propose a packet transfer protocol which establishes the shortest path between source-destination pair a time and restricts heavy generation of dummy packets. We verify the location-privacy of a node on the communication paths through simulation.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.12
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• pp.1260-1268
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• 2009

Three methods(the stepped sine method, the statistical method(random excitation method) and the maximum-length sequence(MLS) method) for head-related transfer functions(HRTFs) are experimentally compared in view point of accuracy and efficiency. First, the stepped sine method has high signal-to-noise ratio, but low efficiency. Second, the statistical method is fast measurement speed, but weak to noise than the other methods. Finally, the MLS method shows both good efficiency and high signal-to-noise ratio, but it needs additional software or equipment such as MLS signal generator. For comparison of measurement accuracy, HRTFs of KEMAR dummy are measured for various azimuths and elevations. Error norms for magnitude and phase of HRTFs are defined and calculated for the measured HRTFs. The calculated error norms show that the methods give similar results in magnitude and phase except a little phase difference in the MLS method.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.65-68
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• 1998

국악의 대중적 공연에 적합한 공연장에 대하여는 아직 그 주관적 객관적 기준이 설립되어 있지 않다. 현재 국립국악원에 있는 예악당은 국악을 위한 대중적 공연장의 기준이 되어야 하나 국악인들과 국악관계자들의 사이에서 국악의 공연에 적합하지 않은 것으로 평가되고 있다. 본 논문에서는 국립국악원의 예악당을, Maximum Length Sequence, 무지향성스피커, dummy head 등을 이용하여 여러 가지 중요한 객관적 지표인 잔향시간, IACC, Initial-time-delay gap등을 측정하고 한 편으로는 컴퓨터 시뮬레이션에 의한 객관적 지표의 추출을 통하여 비교 분석하였다. 그리고, 이를 토대로 예악당의 음향특성을 개선방향과 국악에 대한 주관적 객관적 지표의 설정 방법을 제시하고자 한다.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.2
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• pp.205-213
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• 2017

In order to improve occupant protection in frontal crash, the IIHS introduced a small overlap frontal crash test in 2012. When the front corner of a car collides with another car or object, such as utility pole the test replicated the sequence of events. Because occupants move simultaneously forward and toward the side of the vehicle this test is challenging for some airbag and safety belt designs. In the small overlap frontal test, a car travels at 64 km/h toward a rigid barrier. A hybrid III dummy is positioned in the driver seat. 25% of the total width of the car strikes the barrier on the driver side. After review of small overlap frontal test protocol and overall rating, six run-throughs were performed according to the original test method.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.1118-1123
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• 2005

This paper proposes the CPM bar chart (CBC), a hybrid of the bar chart and the critical path method (CPM). The CBC overcomes shortages of the fence bar chart, while still retaining its advantages. The fence with direction is applied instead of the broken fence, which triggers considerable problems to identify and apply in the fenced bar chart. In addition, the notorious task to find dummy activities is no longer required. Upon the benefits of simplicity in the bar chart and logical work sequence in the CPM network, the CBC provides a relatively easy way to create and understand a schedule, thus improving communication quality between project participants.