• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.213-218
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• 2006

In this paper, we analyzed the performance of orthogonal frequency division multiplexing/ frequency hopping multiple access(OFDM/FHMA) hybrid system that in impulsive interference and broadband wireless communication channel then we applied the turbo code scheme to make satisfied in data and voice transmission service. Also, we compared the bit error rate(BER) performance of turbo coded diversity scheme in the OFDM/FHMA hybrid system. As a result of simulation, proposed OFDM/FHMA hybrid system shows the enhancement of 10 times compared to the general OFDM/FHMA system.

• Information and Communications Magazine
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• v.11 no.10
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• pp.170-179
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• 1994

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.3
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• pp.319-325
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• 2004

FHMA(frequency hopping multiple access) communication system has good performance for the LPI and AJ(low probability of intercept and anti-jamming) application. However, high PAPR(peak to average power ratio) happens in the base-station or the repeater system because of a large number of users. In general, predistorter is used to complete the HPA(high power amplifier) nonlinear characteristics. This paper analyzes BER performance when magnitude of IBO(input back oft) and the number of user are considered as the system parameters. In case of the SSPA(solid state power amplifier), the predistorter does not always work as a complete nonlinear compensator. We find that there is a minimum value of IBO for the predistorter to compensate for the nonlinear SSP A, which is changed as the number of user. If IBO is lower than 6 ㏈ at the user number of 16 and p=1, the system with predistorter is poorer than the one without predistorter. Only when the IBO is over 6 ㏈, predistorter does work as a nonlinear compensator. We call it as cross-over IBO value. TWTA improves the more compensation performance than SSPA because characteristic AM/AM of TWTA has more nonlinear than SSPA. At the BER=10$\^$-3/, there are SNR power gains of about 2.5 ㏈ and 3 ㏈ due to the predistorter when the numbers of users are 16 and 32, respectively.

• Electronics and Telecommunications Trends
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• v.11 no.4 s.42
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• pp.49-62
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• 1996

현재 디지털 주파수공용통신시스템(Trunked Radio System: TRS)에 대한 표준화가 진행되고 있다. 기존의 아날로그 TRS에 대한 표준화가 무산된 경험이 있는 국내 실정에서는 표준화를 진행하면서 이에 필요한 각 시스템(모토롤라의 IDEN, 지오텍스 FHMA, 에릭슨의 EDACS PRISM)에 대한 특성과 시스템의 구성에 대하여 살펴보았으며, 또한 미국, 유럽 일본에 추진하고 있는 디지털 TRS의 표준화 동향에 대하여 조사하였다. 이들 디지털 TRS에 대한 기술 동향을 살펴보고 디지털 TRS에 대한 표준화에 도움이 되고자 한다.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.544-547
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• 2003

The owner of water pipeline has a burden of responsibility for the protection of corrosion and the prevention against leakage of water. So, they have been installed a CP(Cathodic Protection) System in odor to protect corrosion. And they also have been measured and analyzed the data about P/S(Pipe to Soil) potential of water pipeline. The P/S potential is basic data of evaluation for water pipeline corrosion. They need remote automatic corrosion monitoring system for easy maintenance. In this paper, The communication method was studied mainly. And the specifications of proposed TRS (Truncked Radio System ) terminal for corrosion monitoring are introduced briefly.