• 한국통신학회논문지
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• 제33권11A호
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• pp.1053-1062
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• 2008

본 논문은 레일리 페이딩 채널에서 확률밀도함수와 최대비 결합기 출력의 최대모멘트 생성 함수를 일반적이고 간결한 수식적 접근을 통해 보여주었다. 또한, 이를 이용하여 M-PSK, M-PAM, M-QAM의 closed form BER을 증명하였다. 마지막으로 다양한 모의 실험을 통해 증명한 수식이 모의 실험 결과와 정확하게 일치함을 알 수 있다.

• Journal of Information Processing Systems
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• 제13권5호
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• pp.1071-1088
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• 2017

For dual-hop multiple-input multiple-output (MIMO) decode-and-forward relaying systems, we propose a selective relaying scheme that uses orthogonal space-time block code (OSTBC) and transmit antenna selection with maximal-ratio combining (TAS/MRC) or vice versa at the first and second hops, respectively. The aim is to achieve an asymptotically identical performance to the dual-hop relaying system with only TAS/MRC, while requiring lower feedback overhead. In particular, we give the selection criteria based on the antenna configurations and the average channel powers for the first and second hops, assuming Rayleigh fading channels. Also, the numerical results are shown for the outage performance comparison between the dual-hop DF relaying systems with the proposed scheme, only TAS/MRC, and only OSTBC.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.102-122
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• 2017

Nanotechnology has provided a set of tools that the engineers can use to design and manufacture integrated nano devices, which are capable of performing sensing, computing, data storing and actuation. One of the main hurdles for nano devices has been the amount of power that it can generate for transmission of data. In this paper, we proposed cooperative nano communication in the Terahertz (THz) Gap frequency band to increase the range of transmission. Outage probability (OP) performances for the proposed cooperative nano communication networks in the THz band (0.1 - 10THz) have been evaluated for the following scenarios; A) A single decode-and-forward (DF) relay over independent identically distributed (i.i.d.) Rayleigh fading channels, B) DF multi-relay network with best relay selection (BRS) over i.i.d. Rayleigh fading channels, and C) DF multi-relay network with multiple hops with BRS over i.i.d. Rayleigh fading channels. The results show that the transmission distance can be improved significantly by employing DF relays. Also, it is shown that by increasing the number of hops in a relay the OP performance is marginally degraded. The analytical results have been verified by Monte-Carlo simulation.

• 한국통신학회논문지
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• 제35권4C호
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• pp.321-328
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• 2010

본 논문에서는 이동 통신에서 주로 쓰이는 하향/상향링크(downlink/uplink)처럼 상호 간의 상관관계가 존재하는 두 개의 채널에 대한 시뮬레이션 방법을 제안한다. 제안된 방법은 기존 방법의 문제점인 채널 간의 상관관계가 수학적 기준모델과 일치하지 않는 점을 개선한 방법이다. 레일리 페이딩 채널 시뮬레이션 모델은 유한개의 삼각함수의 합을 이용한 SOS(Sum-of-Sinusoids) 방법을 사용하였다. 이 방법은 페이딩 신호의 샘플들을 발생할 때 효율적인 방법으로 알려져 있으며 수학적 기준모델에 대한 정확한 시뮬레이션 결과를 얻을 수 있다. 제안된 모델은 기준모델의 이론적인 상관관계와 시뮬레이터로부터 얻은 채널 간의 상관관계의 오차를 줄이기 위해 MSE를 최소화하는 방식을 이용하면서 평균전력을 이론치와 같게 유지하는 방법이다. 실험결과를 통해 제안한 방법이 기존의 방법보다 기준모델의 수학적 상관관계를 더욱 정확히 모사하는 것을 확인하였다.

• 한국통신학회논문지
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• 제35권1A호
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• pp.1-9
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• 2010

본 논문을 통해 i.n.d 레일리 패이딩 체널에서 서로 다른 변조/복조 기법을 사용하는 중계기들로 구성된 선택적 복호 후 재전송 네트워크의 성능평가를 보여준다. 본 논문은 i.i.d와 i.n.d 레일리 패이딩 채널 모두에서 선택적 복호 후 전송 프로토콜이 최대 다이버시티를 얻을 수 있다는 것을 보여준다. 또한 SC(selection combining)기법을 사용하는 시스템과 MRC(maximal ratio combining)기법을 사용하는 시스템의 성능을 비교하여 결합기술의 효과를 연구하였다. 높은 SNR에서 시뮬레이션 결과와 수식적 분석 결과가 정확하게 일치하는 것을 보여준다.

• 한국통신학회논문지
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• 제38A권5호
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• pp.416-425
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• 2013

A hybrid PN code phase acquisition system based on a least-mean-square adaptive filter, interpreted as a channel estimator is proposed and analyzed for direct-sequence spread-spectrum systems under frequency selective Rayleigh fading channels. Closed form expressions are derived for the filter tap weights and detection/false alarm probabilities. Compared to previously proposed systems, the proposed system achieves smaller mean acquisition times, is more robust to the operating signal-to-noise ratio and allows for multiplication free tap weight updates.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.780-783
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• 1999

This paper gives channel estimation of W-CDMA reverse link using 2-point second-order algorithm over Rayleigh fading channels. The proposed algorithm is compared with the existing interpolation algorithms, i.e., WMSA, linear and second-order Gaussian interpolation, by obtaining HER performance through computer simulations. The BER performance of 2-point second-order interpolation is superior to other algorithms in fading channels. The proposed algorithm also has relatively-simple structure and similar processing delay in comparison to the existing algorithm, Therefore, this algorithm is more suitable for high speed mobile communication environments.

• Journal of Communications and Networks
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• 제11권5호
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• pp.480-488
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• 2009

Cooperative transmission is an effective solution to improve the performance of wireless communications over fading channels without the need for physical co-located antenna arrays. In this paper, selection combining is used at the destination instead of maximal ratio combing to optimize the structure of destination and to reduce power consumption in selective decode-and-forward relaying networks. For an arbitrary number of relays, an exact and closed-form expression of the bit error rate (BER) is derived for M-PAM, M-QAM, and M-PSK, respectively, in both independent identically distributed and independent but not identically distributed Rayleigh fading channels. A variety of simulations are performed and show that they match exactly with analytic ones. In addition, our results show that the optimum number of relays depend not only on channel conditions (operating SNRs) but also on modulation schemes which to be used.

• 대한전자공학회논문지
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• 제26권12호
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• pp.1910-1917
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• 1989

This paper shows the performances of asynchronous binary direct-sequence spread-spectrum multiple access communication systems with Rayleigh fading and White Gaussian noise. The performance measures considered are worst-case bit error probability and average SNR depending on code sequences and chip waveforms. The code sequences used are m-sequence and Gold sequence with period 31.The chip waveforms employed are rectangular, sinusoidal and something other chip waveforms.

• 한국통신학회논문지
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• 제34권2A호
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• pp.91-98
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• 2009

This paper provides new exact-closed form expressions for average SER and average BER as well as outage probability for M-PSK signaling with selection combining over independent but non-identically distributed Rayleigh fading paths. The validity of these expressions is verified by the Monte-Carlo simulations. All of numerical results are in excellent agreement with simulation results.