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Yier Yan,Moon Lee IEEE 2010 IEEE Communications Letters Vol.14 No.1
<P>In this letter, a simple distributed space-time coding scheme is introduced by allocating random interleavers to each relay node in amplify-and-forward (AF) network. By using multiuser definition each rely node provides an interference to the detected signal, a turbo-like symbol by symbol decoder is also introduced. The complexity involved grows only linearly with the number of relay nodes. Simulation results show an acceptable improvement to previous works in the high SNR region.</P>
Recursive Estimation of the Partial Clipping Noise in IDMA System with Limited Peak
YAN, Yier,LEE, Moon Ho The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.4
<P>Interleave-division multiple access (IDMA) inherits the peak-to-average power ratio (PAPR) problem especially with large number of multiple layers. Clipping transmission is a really simple and efficient method, but clipping noise is a tradeoff [1], [2] to its performance. Due to different weighting factors [2], an ordering technique is considered in this letter to recursively cancel the partial clipping noise at each detection. Simulation results show that the performance is close to that of unclipped IDMA chip in the high SNR region (8-9dB).</P>
A High Rate Transmission for Space-Time Block Coding with One Additional Bit Information
YAN, Yier,LEE, Moon Ho The Institute of Electronics, Information and Comm 2011 IEICE transactions on fundamentals of electronics, Vol.ea94 No.3
<P>In this letter, we propose a set of Space-Time Block Codes (STBC) equipped with 4 transmit antennas to transmit one additional information bit achieving rate-9/8. To maintain full rank property of the coding gain matrix, one new orthogonal STBC code with full rate is proposed in this letter. Simulation results show that this method achieves good bit error rate (BER) performance with a small gap compared to that of the rate-1 case and throughput in the high SNR region.</P>
Amplify-Forward Relay Network의 인터리버에 근거한 협동 다이버시티와 그 효과적 알고리즘
얀이얼(Yier Yan),조계문(Gye Mun Jo),발라카난(Balakannan S.P),이문호(Moon Ho Lee) 대한전자공학회 2009 電子工學會論文誌-TC (Telecommunications) Vol.46 No.6
참고문헌 <SUP>[1]</SUP>에서 full diversity를 달성할 수 있을 뿐만 아니라 각 relay node에서의 시간 지연을 제거하기 위해서 새로운 기법을 제안했다. 그러나 복호 후 전달 (DF) 모델 연산 모드는 relay에 더욱 많은 처리 부담을 준다. 본 논문에서는 <SUP>[2],[3]</SUP>에서 제안한 증폭 후 전달 (AF) model로 확장할 뿐만 아니라 source-relay link와 relay-destination link로 이루어진 모든 채널의 결합 채널 계수의 순서를 정하고 다음 복호 절차에서 이전의 복호된 심벌을 지우는 효율적인 복호 알고리즘을 제안한다. 컴퓨터 모의실험 결과를 통하여 제안한 알고리즘을 이용하면 높은 SNR 영역에서 참고문헌 [1]과 비교하여 상대적으로 2-3㏈의 이득을 가져오기에 효율적으로 성능을 향상시킬 수 있다는 것을 알 수 있었다. 또한 제안한 알고리즘이 원래의 알고리즘과 비교하여 상대적으로 3㏈ 이상의 이득을 얻을 수 있는 복호 후 전달 (DF)에 유용하다는 것을 알 수 있었다. In <SUP>[1]</SUP>, the authors have proposed a novel scheme to achieve full diversity and to combat the time delays from each relay node, but decode-and-forward (DF) model operation mode puts more processing burden on the relay. In this paper, we not only extend their model into amplify and forward (AF) model proposed in <SUP>[2],[3]</SUP>, but also propose an efficient decoding algorithm, which is able to order the joint channel coefficients of overall channel consisting of source-relay link and relay-destination link and cancels the previous decoded symbols at the next decoding procedure. The simulation results show that this algorithm efficiently improves its performance achieving 2-3㏈ gain compared to <SUP>[1]</SUP> in high SNR region and also useful to DF achieving more than 3㏈ gain compared to an original algorithm.
Joint Channel estimation in Asynchronous Amplify-And-Forward Relay Networks based on OFDM signaling
얀이얼(Yier Yan),조계문(Gye Mun Jo),발라카난(Balakannan S.P),이문호(Moon Ho Lee) 대한전자공학회 2009 電子工學會論文誌-SC (System and control) Vol.46 No.1
본 논문에서 증폭 후 전달 전송 기법을 사용하는 중계망의 채널 추정을 하는데 있어서 일어나는 문제점을 해결할 수 있는 방법으로 학습 계열(training sequence)을 이용하는 방법을 제안하였다. 현재의 고속 페이딩 채널 환경에서 기존 파일럿의 추정이 적절하지 않아 송신국(source)과 중계국(relay) 사이의 채널과 중계국(relay)과 수신국(destination) 사이의 채널을 결합하여 추정할 경우 많은 문제점이 초래되기에<SUP>[1-2]</SUP> 전송한 신호의 주파수 영역을 선택하여 얻은 정규(Gaussian) 분포에 대하여 최대 우도 함수의 평균을 내어 채널 추정량(estimator)을 유도해 낼 수 있는, 즉, 파일럿 대신에 하나의 OFDM 신호를 사용하여 모든 채널 충격 응답(CIR)을 추정할 수 있는 새로운 방법을 살펴보았다. 컴퓨터 모의실험으로 높은 SNR 영역에서 제안한 채널 추정기(estimator)의 성능이 [1]과 비교하여 약 1㏈ 정도 높음을 확인할 수 있었다. In this paper, we propose a method on the training sequence based on channel estimation issues for relay networks that employ amplify-and-forward (AF) transmission scheme. In [1] and [2], we have to point out that jointly estimating the channel from source to relay and from relay to destination suffers from many drawbacks in fast fading case because the estimation of previous pilots is not suitable for current channel. In this paper, we consider a new joint estimation of overall channel impulse response (CIR) using one OFDM signal without pilots. Using the maximum likelihood (ML) function, we derive a channel estimator by taking the frequency domain of transmitted signal as Gaussian and averaging the ML function over the resulting Gaussian distribution. Simulation results show that our proposed channel estimator performs a fraction of 1㏈ compared with [1] in high SNR region.
Modified Clipping for Iterative Decoding of Superposition Coding
얀이얼(Yier Yan),김정기(Jeong Ki Kim),진주(Zhu Chen),이문호(Moon Ho Lee) 대한전자공학회 2008 電子工學會論文誌-TC (Telecommunications) Vol.45 No.-
본 논문에서는 클리핑 설계보다 파워를 덜 잃음으로서 중첩 코딩 시스템의 반복 복호를 위한 수정 클리핑 설계를 제안한다. 중첩코딩 시스템에서 제안한 설계는<SUP>[1],[2]</SUP> 특히 저 클리핑율의 경우에서 같은 클리핑 비율로 PAPR과 시스템 성능면에서 좋은 성능을 보였다. 마지막으로 클리핑 잡음 때문에 성능이 열화하는 것을 경감시키기 위해서 <SUP>[1],[2]</SUP>에서 제안한 반복 방법으로 SISO 복호알고리즘과 결합된 연 보상 알고리즘을 제안한다. 시뮬레이션 결과들은 제안한 설계로 대다수의 성능 손실이 회복될수 있다는 것을 보였다. In this paper, we propose a modified clipping scheme for iterative decoding of superposition coding system by losing less power than clipping scheme. Our proposed scheme in superposition coding systems<SUP>[1]. [2]</SUP> shows good performance in peak-to-average power ratio (PAPR) and system performance with the same Clipping Ratio especially in low Clipping Ratio case. Finally in order to alleviate the performance degradation due to clipping noises, we combine a soft compensation algorithm that is combined with soft-input-soft-output (SISO) decoding algorithms in an iterative manner proposed by <SUP>[1][2]</SUP>. Simulation results show that with the proposed scheme, most performance loss can be recovered.
Full-Diversity High-Rate STBC for 2 and 4 TransmittedAntennas
얀이얼(Yier Yan),이문호(Moon Ho Lee),마영단(Yizhou Ma) 대한전기학회 2007 대한전기학회 학술대회 논문집 Vol.2007 No.4
We design a new rate-3/2 full-diversity orthogonal space-time block code (STBC) for QPSK and 2 transmit antennas (TX) and 4 transmit antennas (TX) by enlarging the signalling set from the set of quaternions used in the Alamouti[1] and extendedcode and using additional members of the set of orthogonal matrices or Quasi-orthogonal matrices and higher than rate-5/4. Selective power scaling of information symbols is used to guarantee full-diversity while maximizing the coding gain (CG) and minimizing the transmitted signal peak-to-minimum power ratio (PMPR). The optimum power scaling factor is derived analytically and shown to outperform schemes based only on constellation rotation while still enjoying a low-complexity maximum likelihood (ML) decoding algorithm.
Construction of Multiple-Rate Quasi-Cyclic LDPC Codes via the Hyperplane Decomposing
Xueqin Jiang,Yier Yan,이문호 한국통신학회 2011 Journal of communications and networks Vol.13 No.3
This paper presents an approach to the construction of multiple-rate quasi-cyclic low-density parity-check (LDPC) codes. Parity-check matrices of the proposed codes consist of q×q square submatrices. The block rows and block columns of the parity-check matrix correspond to the hyperplanes (μ-flats) and points in Euclidean geometries, respectively. By decomposing the μ-flats, we obtain LDPC codes of different code rates and a constant code length. The code performance is investigated in term of the bit error rate and compared with those of LDPC codes given in IEEE standards. Simulation results show that our codes perform very well and have low error floors over the additive white Gaussian noise channel.