• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1989.10a
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• pp.37-40
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• 1989

In the thesis reserch on the C.T.I. in phenolic resin as a parameter of atmospheric (IEC publication 112) 1) In according as one's decrease atmosph-eric, A number of drops with this as the start for a formative dry band and be pro-duced scintillation increased in a voltage over 300[V]. 2) In a 900[mb] increased this best a num-ber of drops for tracking. In accoding as one's decrease atmospheric increased C.T.I. value.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.270-274
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• 2002

본 논문은 고속 무선랜에 적용하고 있는 OFDM시스템에서 국부발진기의 위상잡음에 의해서 기저대역의 채널에서 나타나는 위상변위특성을 해석하고, 국부발진기를 포함하는 PLL시스템에서 위상잡음 변화를 수치적인 해석을 하였다. OFDM신호를 QPSK, 16QAM 변조신호로 전송하였을 경우, 위상잡음에 따른 관계를 변조신호의 성상도 및 BER관계로써 분석하였다.

• 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.

• 전자공학회논문지 IE
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• v.45 no.1
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• pp.44-49
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• 2008

In this paper, the performance for the non-linear satellite channel including the characteristics of group delay and gain ripple of transponder is analyzed with multi-level QAM-OFDM schemes. Comparing the BER performances between general OFDM and CI(Carrier Interferometry)-OFDM for various QAM schemes, the degree of performance improvement is presented in AWGN environments for specified nonlinear characteristics. The simulations are performed with the 36MHz bandwidth of transponder channel and 120Mbps transmission rate for QPSK, 8QAM, 16QAM, 32QAM, 64QAM schemes between normal and worst case condition. It is shown that the improvement measure by the CI-OFDM for the group delay of channel and nonlinear characteristic of HPA outperforms that for the gain ripple in the case of higher level QAM scheme in normal condition. And the simulation results show that the additional techniques like the channel coding and compensation scheme against the nonlinear characteristic are required for 32QAM and higher level QAM in worst case condition.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.1
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• pp.66-74
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• 2013

This paper introduces the improvement of QoS to compensate the decreasing LED performance by temperature characteristic in the LED-ID communication system. LED does not only use as a lighting device, but also uses as a communication device. The conventional system is transmitted by RGB of LED following the mixture color ratio, which determined the color of lighting, and the BER performance of each RGB signals. However, when the LED used consistently, it has occurred the heat temperature. As a result, LED is degraded the performance by increased temperature each device. To solve this problem, we proposed the adaptive modulation and coding scheme by temperature of device to improve the performance of system and satisfied the QoS in the LED-ID system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.76-84
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• 2007

In this paper, we measured the propagation characteristics of I-UWB channel in time domain and in frequency domain. The measurements carried out in apartment environment while furniture and household electric appliance. Typical indoor scenarios, including line-of-sight(LOS), non-line-of-sight(NLOS) in room-to-room, within-the-room. A transmitting and receiving antenna is a biconical antenna. Results for indoor propagation measurements are presented for power delay profiles(PDP). We extracted the channel characteristic parameters from a power delay profile. Finally, we designed I-UWB channel model in indoor environment, and I-UWB simulator. The results of simulation shows BER characteristics below $10^{-5}$ for SNR over 20[dB].

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.845-854
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• 2003

In this paper, the characteristics of compensation for WDM channel signal distortion due to both chromatic dispersion and Ken effect in 1,000 km 200 Gbps(5${\times}$40 Gbps) WDM systems was investigated. The WDM system has a path-averaged intensity approximation(PAIA) mid-span spectral inversion(MSSI) as a compensation method. This system has a highly nonlinear dispersion shifted fiber(HNL-DSF) optical phase conjugator(OPC) in the mid-way of transmission line. In order to evaluate the degree of compensation, 1 dB eye opening penalty(EOP), bit error rate(BER) characteristics and power penalty of 10$\^$-9/ BER are used. It is confirmed that HNL-DSF is an useful nonlinear medium in OPC fur wideband WDM system with PAIA MSSI and that the optimal compensation for WDM channel distortion is achieved by the selection of pump light power of OPC, which equalize the conjugated light power into the second half fiber section with the input WDM signal light power depending on total transmission length, dispersion coefficient of fiber, OPC pump light wavelength, conversion efficiency of WDM channel in OPC.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.2 no.4
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• pp.531-538
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• 1998

In this paper the system performance degradation resulting from nonlinear transmitter power amplifier which is essential to increase the efficiency is analysed in a CDMA system. The power amplifier is modeled by its AM-AM, AM-PM characteristics. The effects of power amplifier's nonlinearity such as intersymbol interference, phase distonion on the RF system performance were visualized by examining the distorted time domain waveforms, signal vector constellation. And through the investigation of the power spectrum density of the transmitted signal, spectral regrowth or sideband regrowth which is result from amplitude distortion can be seen. All these characteristics result in BER performance degradation due to other user interferences and intersymbol interference. The analysis technique described here applies not only to power amplifier but also to any other nonlinear components such as mixers and switches. Also the effects of adjacent channel interference and supurious emission can be analysed between different systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.479-486
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• 1999

In this paper the system performance degradation resulting from nonlinear transmitter power amplifier which is essential to increase the efficiency is analyzed in a forward link CDMA system. The power amplifier is modeled by power series model which includes only odd-order terms. The effects of power amplifier's nonlinearity such as intersymbol interference, phase distortion on the RF system performance were visualized by examining the distorted time domain waveforms, signal vector constellation. And through the investigation of the power spectrum density of the transmitted signal, spectral regrowth or sideband regrowth which is result from amplitude distortion can be seen. All these characteristics result in BER performance degradation due to other user interferences and intersymbol interference. The analysis technique described here applies not only to power amplifier but also to any other nonlinear components such as mixers and switches. Also the effects of adjacent channel interference and supurious emission can be analysed between different systems.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.5
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• pp.181-186
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• 2008

Wireless data transmission is vulnerable to attackers and hackers. Recently, the fast development of wireless communication systems seamlessly increase the demand for security in this area. Moreover, error correction is especially important because various kinds of interferences among wireless devices. In order to solve two above problems, we propose to apply MCC (M-sequence Convolutional Code) in the system which is able to protect information and correct errors. The proposed system can obtain higher secure property by randomly changing the output connections by the proposed M-sequence. Performance of the system is analyzed according to BER (Bit Error Rate) and secure levels. The simulation results revealed that we can get the coding gain of 0.1 dB over conventional convolution coding technique. The proposed algorithm is installed in physical layer and easily implemented. Another advantage of our proposed (M-sequence and convolutional code) is that it can be applied to CDMA (Code Division Multiple Access) communication system.