• Journal of information and communication convergence engineering
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• v.1 no.3
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• pp.115-118
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• 2003

This paper analyzes Bit Error Rate (BER) performance of a wireless communication system using BPSK modulation technique with a smart antenna at base station. The channels under consideration are Additive White Gaussian Noise (AWGN) channel or a slow, flat Rayleigh fading channel with AWGN. Under the assumptions that the MMSE beamformer is used and the time delays of all users are approximately equal, we first analytically derive closed-form expressions for the BER of the desired user. Then, computer simulation is carried out to verify the theoretical results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.308-315
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• 2002

This paper proposes new probability models for wideband code division multiple access (W-CDMA) signals. The performance of a W-CDMA system is evaluated by calculating the average bit error rate(BER) which is derived from the probability distribution of the W-CDMA receiver output. If a probability model of the receiver output is available, the performance evaluation becomes much simpler and it enables diverse analyses of the system for channel coding and other purposes. In this paper, probability distributions of W-CDMA signals, more specifically those of the receiver output, are represented as Rayleigh and noncentral chi distribution, considering various bandwidths and channel environments. The adequacy of a probability model is verified by chi-square test of 1% significance level. The BER of the system obtained from the simulation results is compared to that obtained from the probability model to demonstrate the usefulness of the proposed models.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.5A
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• pp.855-862
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• 2001

본 논문에서는 백색잡음과 페이딩 환경하의 통신시스템의 성능평가시 백색잡음에 대해서만 모멘트 기법을 이용조건부 오류확률을 구하고 페이딩에 대해서는 해석적 접근방식을 취함으로써 전체적인 컴퓨터 수행시간을 획기적으로 개선시킬 수 있는 기법을 제안하고, 제안된 기법의 효율성을 컴퓨터 시뮬레이션 수행시간 비교를 통해 입증하였다. 현재 널리 사용되는 Monte Carlo 시뮬레이션 기법은 IS-95 순방향 채널과 같이 많은 샘플수를 필요로 하는 시스템에서 상당한 시뮬레이션 수행시간을 요구하게 된다. 이러한 문제점을 해결하기 위하여, 제안된 방식에서는 백색잡음하의 수신신호의 N차 모멘트를 측정하여 이산확률밀도함수를 구함으로써 수신신호의 확률적 특성을 모사하고, 이로부터 내삽법과 외삽법을 적용하여 조건부 누적확률분포함수를 산출함으로써 채널오류율을 구하게 된다. 그리고 페이딩 성능평가시 조건부 채널오류율을 이용하여 산출된 조건부 누적확률분포함수를 환경조건에 맞춘 후에 페이딩의 확률밀도함수와 수치 해석적으로 간단히 적분하여 성능평가를 함으로써 수행시간의 줄임과 동시에 정확한 채널오류율을 구하게 된다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.694-699
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• 2007

We consider an optimal antenna weighting scheme for a closed-loop transmit antenna diversity system in Rayleigh fading channels. We derive a closed-form expression for the optimal transmitter weights that minimize the average bit error rate (BER) subject to fixed average and peak transmit power constraints. It is shown that the peak power limitation degrades the average BER performance more significantly as the available average power and/or the number of transmit antennas increase.

• ETRI Journal
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• v.35 no.3
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• pp.406-413
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• 2013

In this paper, an orthogonal frequency division multiple access (OFDMA)-based minimum end-to-end delay (MED) distributed routing scheme for mobile backhaul wireless mesh networks is proposed. The proposed scheme selects routing paths based on OFDMA subcarrier synchronization control, subcarrier availability, and delay. In the proposed scheme, OFDMA is used to transmit frames between mesh routers using type-I hybrid automatic repeat request over multipath Rayleigh fading channels. Compared with other distributed routing algorithms, such as most forward within radius R, farthest neighbor routing, nearest neighbor routing, and nearest with forwarding progress, simulation results show that the proposed MED routing can reduce end-to-end delay and support highly reliable routing using only local information of neighbor nodes.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.147-150
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• 2004

In this paper, we propose a reduced-state sequence estimation (RSSE) for trellis coded modulation (TCM) in OFDM with two-stage IDFT/ DFTs, MMSE-LE, and interleaving on frequency selective Rayleigh fading channels. The Viterbi algorithm (VA) is used to search for the best path through the reduced-state trellis combined with equalization and TCM decoding. Computer simulations confirm the bit error probability of the proposed scheme.

• Journal of Communications and Networks
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• v.16 no.1
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• pp.26-35
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• 2014

We consider multiple-input multiple-output decode-and-forward relay systems in Rayleigh fading channels under the partial channel state information (CSI) that the channel statistics of the source-relay (SR) link and the instantaneous CSI of the source-destination and relay-destination links are known at the destination. In this paper, we propose a new near maximum likelihood (near-ML) decoder with two-level pairwise error probability (near-ML-2PEP) which uses the average PEP instead of the exact PEP. Then, we theoretically prove that the near-ML and near-ML-2PEP decoders achieve the maximum diversity, which is confirmed by Monte Carlo simulations. Moreover, we show that the near-ML-2PEP decoder can also achieve the maximum diversity by substituting the average PEP with the values that represent the error performance of the SR link.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.6
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• pp.2567-2582
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• 2016

This paper investigates the impact of outdated channel state information (CSI) on the performance of the incremental amplify-and-forward (AF) opportunistic relaying (OR) over dual-hop Rayleigh fading channels. According to the definition of distribution function, we obtain the cumulative distribution function (CDF) of the actual combined signal-to-noise ratio (SNR) received at the destination. Based on this CDF, the closed-form expressions of the average spectral efficiency and outage probability are derived for the incremental AF OR under outdated CSI. Numerical results show that in the low region of the average SNR of the direct link, outdated CSI deteriorates the system performance, whereas in the high region, outdated CSI has almost no impact on the system performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.4 s.346
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• pp.39-43
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• 2006

In this contribution, the achievable performance of orthogonal multicarrier DS-CDMA systems employing synchronous uplink transmissions is investigated. The bit error ratio (BER) performance is analyzed under dispersive Rayleigh multipath fading conditions as a function of the number of users.

• Journal of electromagnetic engineering and science
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• v.10 no.2
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• pp.56-60
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• 2010

This paper proposes a new cooperative protocol in which Alamouti's scheme is applied to exploit the advantages of both coded cooperation and Alamouti's scheme. It not only has better than direct transmission but also coded cooperation at appropriate cooperation levels. Simulation results show that the proposed protocol can save approximately 6~7 dB of transmit power to achieve the target BER(Bit Error Rate) compared with coded cooperation. Furthermore, the performance of the proposed protocol does not significantly depend on the qualities of inter-user channels.