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이동통신시스템의 링크 성능분석을 위한 페이딩마진에 관한 연구
오의교 호남대학교 2004 호남대학교 학술논문집 Vol.25 No.2
For the mobile communication, there is at least one LOS (Line-of-sight) component, so the fading components are distributed according to the Rician distribution. The statistical representation of the pdf (probability density function) , LCR(Level crossing rate) and AFD(average fading duration) in the mobile communication and the fading margin are presented. Using these results, the link budget of the mobile communication system will be considered for preventing the fading margin.
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ARQ 프로토콜을 이용한 시스템의 throughput 향상에 관한 연구
오의교 호남대학교 1998 호남대학교 학술논문집 Vol.19 No.2
ARQ scheme has been used for error correction method in the data communication system as satellite or mobile communication system. In this paper, the system throughput can be increased by adapting the data block sizes according to the channel bit error rate. The algorithm has been designed to estimate the channel BER by the number of the correct transmitted blocks. The increasement of the throughput according to the proper selection of block size is verified by computer simulation for various channel conditions.
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오의교 湖南大學校 1996 호남대학교 학술논문집 Vol.17 No.2
Direct Broadcasting Satellite receiver should have the capability of the Conditional Access System for preventing the unsubscribed users. Scrambling and descrambling are the major roll of the Conditional Access System in the DBS. DVB suggested the new secrity algorithm for these purpose and Koreasat receiver adapted the DVB algorithm for the domestic DBS. In this paper, the design of the descrambler based on the DVB algorithm is described. The modular design and parallel processing are the main characteristic of the design, and the high speed processing for MPEG 2 signal is possible with these procedure. The ASIC will be fabricated and used for the DBS reciever.
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오의교 호남대학교 산업기술연구소 2000 산업기술연구논문집 Vol.8 No.-
전형적인 변조방식은 제한된 주파수 스펙트럼과 효율적인 전력을 만족하기 위한 조건을 구비한 방식을 사용하며, 각 방식은 통신채널 환경의 변화에 대응하기 위해 여유 마진을 가지고 있다. 이러한 여유 마진을 이용하여 동일 전력으로 효율적인 전송을 하기 위한 변조방식이 적응변조 방식이다. SDR에서는 여러 변조방식을 소프트웨어 다운로드를 받아 DSP 및 ASIC을 이용하여 사용목적에 따라 각기 다른 방식을 사용하도록 하고 있지만, DSP를 이용한 소프트변조방식이 적용되는 SDR에는 효율적인 적응변조 방식이 가능하며, 본 논문에서는 이러한 적응변조방식의 구조를 제안한다. Typical modulation method is used for the limited frequency spectrum and efficient power consumption. And these methods have the marginal power for the worst environment. Adaptive modulation method is using the marginal power for the throughput increasement. Software Defined Radio use the Digital signal processing and ASIC for the software modulation via downloading from the horst. Adaptive modulation method is properly used in this case because it should be modulated as software method.
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오의교 호남대학교 2008 학술논문집 Vol.29 No.2
Software radio technology is merging as the new generation technology for the mobile communication. For this technology, totally all the system components need to be digitalized. But the current ADCs are not supported for the fast speed and low power consumption. Bandpass sampling, using undersampling theory, can be used for the RF receiver instead of the current superheterodyne receivers. A few problems are questioned to use the bandpass sampling. On this paper, three major problems are discussed. Folding, Analog bandwidth, jitter are described and simulated as the receiver noise. Simulation result showed the bandpass sampling is the good choice for the new generation RF receiver architecture to apply the software radio systems. Some issues should be solved, such as the ADC speed, low power consumption, etc, But they are expected to realize soon.
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적응변조방식을 사용한 이동국의 전송효율 개선방안에 관한 연구
오의교 호남대학교 정보통신연구소 2004 정보통신연구 Vol.14 No.-
A new adaptive modulation scheme is proposed for a DS-CDMA based system where power control and high mobility are main performance-decision factors. The main feature of the proposed scheme is to control the power level adaptively by monitoring and adjusting time-varying signal-to-noise ratio (SNR) change rate and thus improving the system stability performance with minimal change of the existing hardware, while maintaining system throughput performance.. Many researches have been focused on efficient methods in order to increase spectral efficiency by applying adaptive modulation. However, since most of these proposed methods are limited to the half-duplex slow adaptation, it is difficult to monitor and track rapidly changing SNR. The full duplex system model is taken into account in order to monitor a time-varying mobility of the targeted mobile station. The mobile station with high mobility is monitored and controlled by the proposed SNR level control algorithm, which is performed by adjusting SNR level to change rapidly. With this reasoning, the proposed algorithm maintains the current level with rapid SNR change. Moreover, it can change a modulation level (M-ary modulation level) to the lowest level to overcome the worst channel quality environment by decreasing SNR level rapidly. Thus, the proposed algorithm can overcome the major drawback of the conventional SNR level changing algorithm which causes fatal system error and thus, degrades overall system stability performance.
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VSAT 시스템의 버스트데이타 전송 알고리즘에 관한 연구
오의교 호남대학교 1997 호남대학교 학술논문집 Vol.18 No.4
VSAT system is used for the low rate data transmission by the packet network via satellite. The inbound access scheme from the remote stations to HUB is the TDMA, and the inbound data should be sent by burst mode. Therefore the HUB should be synchronized with the remote stations. This paper describes the burst data transmission algorithm for the VSAT system to synchronize and proper operation. The algorithm is tested under the test environment, and used for the VDS-100 system via Koreasat satellite. The algorithm may be modified to operate optimally for the new VSAT system.
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오의교 호남대학교 정보통신연구소 1998 정보통신연구 Vol.8 No.-
The low power devices are used for the wireless communication in the small area with low power which does not interfere to the other applications. According to the increasing need for the LPDs rapidly, the recommendation for each applications are necessary. The universal european standard is recommended by CEPT, and the technical characteristics to each application is made by the ETSI. In this paper, the trend of the standard of the european low power devices are introduced. To meet the increasing requests for the low power devices, the effort for the standard will be needed among the government, company and university.
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