• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 추계종합학술대회 논문 초록집
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• pp.127-127
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• 2004

• 한국통신학회논문지
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• 제25권3A호
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• pp.362-374
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• 2000

In this paper, trellis coded 16 QAM Multi-Carrior CDMA system is proposed, Using the equivalent signal-to-noise plus interference Power ratio (SNIR) of Multi-Carrier CDMA system in the reverse link, capacity and BER performance of trellis coded 16 QAM Multi-Carrier CDMA system are analyzed taking into account the number of multi-carrier, the number of multiple access user, the number of SC/MRC diversity branch, and Rician fading parameter in multiuser interference and Rician fading channel. And the capacity and the BER performance of trellis coded 16 QAM Multi-Carrier CDMA system using selection combining (SC) and maximal ratio cabining (MRC) diversity are numerically compared. Obtained results show that the capacity of proposed system depends on the number of multi-carrier. ti is found that the trellis coded 16 QAM Multi-Carrier CDMA system with SC/MRC antenna diversity scheme is efficient to combat multipath fading and to increase the maximum number of users in high speed data communication. With the results of analysis. MRC diversity technique provides the performance fro high speed data communications. Finally, we present a numerical approach to derive the capacity and the BER performance and to find the maximum number of multiple access user for Multi-Carrier system in multiuser interference and Rician fading channel.

• Journal of Communications and Networks
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• 제16권1호
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• pp.10-17
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• 2014

This work investigates two important performance metrics of underlay cooperative cognitive radio (CR) networks: Interference cumulative distribution function of licensed users and outage probability of unlicensed users. These metrics are thoroughly analyzed in realistic operating conditions such as imperfect fading channel information and strict transmit power constraint, which satisfies interference power constraint and maximum transmit power constraint, over Nakagami-m fading channels. Novel closed-form expressions are derived and subsequently validated extensively through comparisons with respective results from computer simulations. The proposed expressions are rather long but straightforward to handle both analytically and numerically since they are expressed in terms of well known built-in functions. In addition, the offered results provide the following technical insights: i) Channel information imperfection degrades considerably the performance of both unlicensed network in terms of OP and licensed network in terms of interference levels; ii) underlay cooperative CR networks experience the outage saturation phenomenon; iii) the probability that the interference power constraint is satisfied is relatively low and depends significantly on the corresponding fading severity conditions as well as the channel estimation quality; iv) there exists a critical performance trade-off between unlicensed and licensed networks.

• 한국전자파학회논문지
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• 제12권2호
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• pp.208-216
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• 2001

고속무선 이동통신에서 가장 문제가 되는 것이 전파의 다중경로에 의한 페이딩 잡음이며, 이러한 페이딩의 문제점을 이동성을 보장하면서도 효율적으로 해결할 수 있는 방법이 최근 제안된 STTD (Space Time Transmitter Diversity) 기법이다. STTD 방법은 2개의 송신 안테나와 1개의 수신안테나로 쉽게 2차 다이버시티를 제공할 수 있다. 본 논문에서는 상관된 레이레이 페이딩 채널환경에서 적용될 수 있는 확률 밀도함수를 유동하고 유도된 확률밀도함수를 이용하여 비동기 M-ray FSK, DPSK 및 ASK 송신 다이버시티 시스템의 정확한 오류확률을 유도하고 그 성능을 비교 분석한다.

• 디지털콘텐츠학회 논문지
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• 제5권2호
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• pp.121-127
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• 2004

본 논문은 주파수 선택성 라이시안 페이딩으로 모델링되는 다중경로 페이딩 환경에서 수신되는 직교주파수분할다증 (OFDM : Orthogonal Frequency Division Multiplexing 16 QAM (Quadrature Amplitude Modulation) 신호의 오율 성능을 해석하였다. 주파수 선택성 라이시안 페이딩으로는 라이시안의 심도 (K)를 이용하여 three-path 페이딩 모델을 사용하였으며, 성능 개선을 위하여 BCH 채널 부호화 기법을 채용하였다. 수치 해석에 의해, BCH채널 부호화에 의한 오율 성능의 개선 정도와 에러정정능력에 따른 개선 효과를 확인하였다. 결과적으로 채널 부호화 기법만으로는 무선 멀티미디어 통신에서 요구되는 오율 (10-6 정도)을 얻을 수 없으므로, 새로운 성능 개선 기법을 함께 채용하여야 하겠다.

• ETRI Journal
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• 제39권5호
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• pp.718-728
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• 2017

Empirical modeling of wireless fading channels using common schemes such as autoregression and the finite state Markov chain (FSMC) is investigated. The conceptual background of both channel structures and the establishment of their mutual dependence in a confined manner are presented. The novel contribution lies in the proposal of a new approach for deriving the state transition probabilities borrowed from economic disciplines, which has not been studied so far with respect to the modeling of FSMC wireless fading channels. The proposed approach is based on equal portioning of the received signal-to-noise ratio, realized by using an alternative probability construction that was initially highlighted by Tauchen. The associated statistical procedure shows that a first-order FSMC with a limited number of channel states can satisfactorily approximate fading. The computational overheads of the proposed technique are analyzed and proven to be less demanding compared to the conventional FSMC approach based on the level crossing rate. Simulations confirm the analytical results and promising performance of the new channel model based on the Tauchen approach without extra complexity costs.

• 한국통신학회논문지
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• 제18권7호
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• pp.959-969
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• 1993

본 논문에서는 페이딩 디스퍼시브 채널에서 시간 및 주락수축상에서의 확산 현상을 고려하여 DS/SS DPSK 통신 시스템의 성능을 분석하었다. WSSUS 채널 모델을 이용하여 채널의 시간과 주파수축상의확산 현상의 정도를 각각 다중 경로 확산량과 도플러 확산량으로 표현하고, DS/SS DPSK 통신의 오율을 채널과 시스템의 파라메터에 대한 식으로 유도하였다. 또한, 계산을 보다 간단히 하기 위하여 주파수축 확산 현상에 대하여 근사적 계산 방법을 제시하고, 이 근사화식을 이용하여 레일리 및 라이시안 페이딩 채널에서 DS/SS DPSK통신 시스템의 오율 특성을 칩 수의 변화에 따라 비교분석하였다.

• Journal of electromagnetic engineering and science
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• 제12권1호
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• pp.77-84
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• 2012

This paper introduces our development of a MIMO-OTA system with simplified configuration. The key element of our proposal is the adoption of an antenna branch-controlled configuration for generating multipath delayed waves. The signal processing is carried out on IF band signal with an FPGA in a fading-emulator-type MIMO-OTA measurement system. The proposed scheme is largely different from available system configurations for the fading simulator method of constructing the OTA test environment. We describe the principle of the proposed scheme, channel model incorporated in the system, basic configuration of the developed system, and its performance.

• 한국정보통신학회논문지
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• 제5권1호
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• pp.52-60
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• 2001

본 논문에서는 나카가미 페이딩 환경에서 다중 반송파 MFSK-DPSK/DS-CDMA 합성 변조기법을 제안하였다. 또한, 다중경로 페이딩에 강한 특성과 주파수 이용 효율이 높은 다중반송파 DS-CDMA 합성변소 방식을 같이 사용하여 분석하였다. 그러한 변조방식은 비동기식 MFSK와 MFSK에 기반한 DPSK를 이용한 결합 주파수 위상 합성변조 방식이다. 결과로부터 전력효율과 대역폭 효율이 일반적인 통신 시스템보다 다중캐리어 합성 변조시스템이 효율을 개선시킬 수 있음을 알았다.

• Journal of Communications and Networks
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• 제5권2호
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• pp.150-156
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• 2003

In this paper, an uplink MC-CDMA system incorporating multiuser detection and smart antennas has been considered. The performance of asynchronous as well as synchronous system is studied over a correlated Rayleigh multipath slow fading channel. A simplified array-processing algorithm suitable for slow fading situation is investigated to overcome the heavy computational complexity associated with Eigen solutions. The effect of variable data rate in the system performance is considered and effectiveness of antenna array to handle high data rate is discussed. A brief investigation on the system performance degradation due to correlated channel is also carried out. Based on the extensive simulation carried out, the performance of the asynchronous uplink system is found dramatically improved with antenna array and multiuser detection. Asynchronicity and channel correlation are found to affect the system performance significantly. The investigated simpli- fied algorithm produces similar results as Eigen solutions in slow fading situation with much reduced complexity.