• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.75-80
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• 2005

A new antenna shuffling scheme for double space time transmit diversity is proposed. The proposed method obtains the shuffling pattern directly from the estimated channel by maximizing minimum post-processing signal to noise ratio(SNR), while the conventional method minimizes channel correlation. Since the minimum post-processing SNR is directly related with error performance, the proposed method shows better bit error rate performance than the conventional method. Monte Carlo simulations showed that the proposed scheme has more 3 dB SNR gain than the conventional scheme for 10/sup -3/ bit error rate in spatially correlated fadingcaused by a single cluster model.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.293-295
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• 2015

AIS의 내부 GPS는 UTC 동기 설정에 사용되며, AIS가 내부 GPS에 직접적으로 동기를 맞추지 못하면 직접동기를 하고 있는 주변 기지국 또는 선박국에 간접동기를 맞추도록 되어 있다. 그러나 내부 GPS 수신 상태가 불량하거나 GPS 접속 설정이 잘못된 경우 미송신이 발생하거나 잘못된 동적정보를 제공하는 등 AIS 동작에 오류가 발생하고 있다. 여기에서는 내부 GPS가 불량할 경우 AIS 작동에 어떤 영향을 미치는지 분석하였다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.3
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• pp.41-49
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• 2003

본 고에서는 휴대 이동단말 시스템의 복합다기능화 및 단말기내 적용되는 주파수 변조 방식의 변화에 따른 핵심부품으로서 표면탄성파필터의 요구 성능의 변화 및 그에 따른 대응방향에 대해서 설명하고 있다. 현재 전세계적으로 널리 보급되고 있는 코드분할다중접속방식(CDMA)의 이동단말기에서는 수퍼헤테로다인 변복조방식의 적용에 따라 표면탄성파 소자로서 듀플렉서, 송신 RF 필터, 수신 RF 필터 및 수신 IF 필터 등이 적용되어 왔다. 하지만 최근 들어 RF 대역에서 기저대역으로 신호의 직접변환(Direct Conversion)이 가능한 Chipset의 보급과 더불어 급속히 Zero-IF화가 추진되고 있으며, 그에 따라 RE 필터부의 고성능화가 요구되고 있다. Zero-IF Chipset은 신호대 잡음비를 크게 하기 위해서 수신 RE 필터에 있어서 Balance 구동을 기본으로 하고 있으며, 듀플렉서에 있어서는 통과대역의 저손실화, 저지대역의 고감쇠화 및 송수신간 높은 격리도를 요구하고 있다. 본 고에서는 이러한 요구사항을 만족시킬 수 있는 표면탄성파 필터의 구현 원리와 향후 동향에 대해 논의하였다.

• Proceedings of the KIEE Conference
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• 2002.07d
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• pp.2831-2833
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• 2002

최근 인터넷의 대중화와 함께 설문조사 기법이 발전하면서 '사이버 설문조사'의 활용범위가 넓어지고 있다. 웹을 중심으로 진행되는 사이버 설문조사는 적은 비용으로 단시간내 여론을 알 수 있는 장점이 있지만, 서버와 네트워크에 과다한 트래픽을 유발한다. 본 논문은 이러한 단점을 보완하기 위해 이메일 방식을 사용한 멀티미디어 웹 설문지 관리 시스템을 설계 및 구현하였다. 본 시스템은 POP3로 수신된 설문메일을 가져와 처리함으로써 기존의 인터텟상에서 이루어지는 설문조사와는 달리 웹 데이터베이스를 사용하지 않는다. 따라서, 서버의 트래픽을 줄이고, 수신된 설문메일의 설문형태에 따른 키워드로 답변을 필터링하여 잘못된 응답메일은 자동으로 발신하고 제대로 수신된 메일은 문항별로 응답을 데이터베이스에 저장한다. 또한, 기존의 단순한 설문형태를 벗어나 동영상과 사운드를 이용한 멀티미디어 설문메일을 통해 다양한 설문조사가 가능하며 이메일을 이용함으로써 사용자가 직접 설문사이트에 전속하지 않아도 되는 편리함을 제공한다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.3 s.309
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• pp.41-50
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• 2006

This paper presents a novel ultrasonic sensor system to overcome limited distance detection range that can be measured only more than 30cm by single ultrasonic transducer. This is accomplished by separation of receiving capacitive ultrasonic transducer from transmitting capacitive ultrasonic transducer. And hardwares and software of the system are described in detail. The system makes very close range as well as long range detect by wireless precisely. Frequency of trigger pulse is 10Hz, but it is very low frequency for transmitting data in wireless module. Therefore, for triggering between receiver and transmitter, an algorithm for mixing and distinguishing trigger pulse from carrier pulse by software is proposed. The system is designed by common microprocessor 8051. The performance of the proposed method has been assessed through two types. The first, transmitting and receiving transducer are put on both sides. And then, distance of two point is measured as far as 0mm. Secondly, transmitting transducer send out ultrasonic pulse and measure the time of flight(TOF) until a first echo from an object detected by the detached receiving transducer. The distance between the detached transducers and a reflecting object is measured as far as 7cm. Images of measured ultrasonic waves and TOF for two methods presented to prove effectiveness of results.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.82-88
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• 2009

An adaptive cooperation system is considered with the cooperation decision strategy based on the differences between instantaneous signal-to-noise ratio (SNR) S-D and R-D channels. Specifically, if the quality of the direct link (S-D) is better than that of the link from the relay to the destination (R-D), the source will transmit to destination directly with all scheme's transmitted power. Otherwise, the source broadcasts the signal with a lower power in the first time slot. Then, in the second time slot, if the relay decodes its received signal correctly, it re-transmits the re-encoded signal to the destination else the source will transmit again with the remaining power. Firstly, the spectral efficiency is derived by calculating the probabilities of direct transmission and cooperation mode. Subsequently, the BER performance for the adaptive cooperation schemes is analyzed by considering the BER routine of each mode. Finally, the Monte-Carlo simulation results are presented to confirm the performance enhancement offered by the proposed schemes.

• Analyses & Alternatives
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• v.8 no.1
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• pp.111-135
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• 2024

This paper classifies the main directions of public diplomacy as 'sender-centered public diplomacy' and 'receiver-centered public diplomacy' and attempts to conceptualize them in the initial stage. In the process, the paper evaluates the specific cases and performance of 'receiver-centered public diplomacy' for posts uploaded by the U.S. Embassy in Seoul on SNS (Facebook) over the past year in 2021. Receiver-centered public diplomacy aims to win the favor of foreign citizens by introducing and experiencing the culture and specificity of the other country. As a result of the analysis, the U.S. Embassy in Seoul is striving to win the favor of the Korean people by directly introducing and experiencing Korean major issues and trends as well as Korean traditional culture such as kimchi and traditional liquor. Furthermore, it can be seen that the values and policies pursued by the United States are effectively promoted through this method. Korea's public diplomacy, which is still in the 'sender-centered', needs to establish a more effective strategy by referring to the case of the United States.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.6 s.324
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• pp.1-7
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• 2004

The development of direct receiver techniques is expected to be a solution for future wideband or multi-band wireless systems based on software defined radio. In this Paper, we study the regeneration of I and Q signals for the SDR based direct conversion receiver, so that we can handle a wide bandwidth and maintain maximal flexibility in system utilization. After modeling the basic system considering the real wireless communication environment, and studying the impact of imperfect phase imbalance on the performance of a direct conversion receiver, we propose a suboptimal I and Q signal regeneration algorithm for the system. The proposed algerian regenerates I and Q signals using a real time early-late compensator which effectively estimates phase imbalances and gives feedback in a directreceiver. The proposed algorithm is shown to mitigate the impact of AWGN and improves performance especially at low SNR channel condition. According to the computer simulation, the BER performance of the proposed system is at least about 4 dB better than conventional systems under $45{\~}55$ degrees random phase errors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5C
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• pp.444-452
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• 2012

The detection performances, in this paper, are derived according to combination of the multiband GNSS signals in broadband jamming environments. The detection probabilities depending on the false alarm probabilities are derived and presented via Monte-Carlo simulation under the assumption as follows: the GNSS signals are perfectly orthogonal and simultaneously received by the receiver using non-coherent correlation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.6
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• pp.1402-1409
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• 2007

In this paper, we propose various types of AGC algorithms for implementing the OFDM communication systems. For the high-speed packet transmission, in this paper, we assume the OFDM system with relatively long and repeated preambles. We propose the maximum sample value counter for counting the number of maximum sample. In the maximum sample value counter, we use the buffer for the digital signal buffering. Finally, the counting value of the maximum sample value counter controls the gain control signal generator by using gain control table automatically.