• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.1-9
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• 2010

This paper offers performance analysis of selection decode and forward (DF) networks with differential modulation/demodulation for an arbitrary number of relays in independent but not identically distributed Rayleigh fading channels. We have shown that the selection DF protocol with differential modulation can achieve full diversity in both independent identically distributed (i.i.d.) and independent but not identically distributed (i.n.d.) Rayleigh fading channels, and the performance loss due to using non-coherent detection is not substantial. Furthermore, we study the impact of combining techniques on the performance of the system by comparing a system that uses selection combining (SC) to one that uses maximum ratio combining (MRC). Simulations are performed and show that they match exactly with analytic ones in high SNR regime.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.2
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• pp.252-258
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• 2000

In this paper, we improve error performance for BPSK and QPSK when the carrier recovery signal is not perfect in the multipath Rician fading channel based on DS-CDMA system. In the case, we use the MRC(Maximal Ratio Combining) diversity and convolutional coding technique in order to overcome this carrier phase error and Rician fading. With results of analysis, we know that the appropriate use of MRC diversity and convolutional code reduced considerably performance degradation due to phase error.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.5
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• pp.1588-1603
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• 2014

In space diversity combining, conventional methods such as maximal ratio combining (MRC), equal gain combining (EGC) and selection combining (SC) are commonly used to improve the output signal-to-noise ratio (SNR) provided that the channel is perfectly estimated at the receiver. However, in practice, channel estimation is often imperfect and this indeed deteriorates the system performance. In this paper, diversity combining techniques based on two evolutionary algorithms, namely genetic algorithm (GA) and particle swarm optimization (PSO) are proposed and compared. Numerical results indicate that the proposed methods outperform the conventional MRC, EGC and SC methods when the channel estimation is imperfect while it shows similar performance as that of MRC when the channel is perfectly estimated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11C
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• pp.1070-1076
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• 2003

This paper presents and analyses the exact and general closed-form expression for the average bit error probability of M-ary square quadrature amplitude modulation (QAM) for maximal ratio combining (MRC) diversity reception in frequency-nonselective Nakagami-m fading. An L-branch Maximal ratio combining diversity technique with independent or correlated fading cases is considered. Numerical results demonstrate the error performance improvement by employing with the use of MRC diversity reception. The new expressions presented here can offer a convenient way to evaluate the performance of an arbitrary square M-W square QAM with an MRC diversity combiner for various cases of practical interest.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.1-11
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• 1998

We present somple block methods for blind maximal ratio combining (MRC) based on a maximum likelihood (ML) principle and finite alphabet properties (FAP) inherent in digital communication systems. The methods can provide accurate estimates of channel parameters even with a small subset of data, thus realizing nearly perfect combining. The channel parameters of diversity branches and the data sequence are estimated simultaneously by using an alternating projection technique. Two different methods, that is, (1) Joint combining and data sequence estimation(JC-DSE) method and (2) Pre-combining and blind phase estimation (PC-BPE) method are presented. Efficient initiallization schemes that can assure the convergence to the global optimum are also presented. Simulation results demonstrate the performance of two methods on the symbol error rate (SER) and the estimated accuracy of the channel parameters.

• Journal of Communications and Networks
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• v.9 no.1
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• pp.67-74
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• 2007

The performance of dual diversity receivers operating over correlated Ricean fading channels is analyzed. Using a previously derived rapidly converging infinite series representation for the bivariate Ricean probability density function, analytical expressions for the statistics of dual-branch selection combining, maximal-ratio combining, and equal-gain combining output signal-to-noise ratio (SNR) are derived. These expressions are employed to obtain novel analytical formulae for the average output SNR, amount of fading, average bit error probability, and outage probability. The proposed mathematical analysis is used to study various novel performance evaluation results with parameters of interest the fading severity, average input SNRs, and the correlation coefficient. The series convergence rate is also examined verifying the fast convergence of the analytical expressions. The accuracy of most of the theoretical performance evaluation results are validated by means of computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4A
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• pp.307-314
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• 2010

In this paper, a receive diversity combining technique is proposed for single-carrier frequency division multiple access (SC-FDMA)-based cooperative relay systems when discrete Fourier transform (DFT) spreading sizes for mobile station (MS) and relay station (RS) are different. The proposed technique is composed of a DFT spreading size adjustment block, a phase rotation compensation block, a channel phase compensation block, and a receive diversity combining block. The proposed technique is robust to multipath channels and can be operated with a relatively small computational complexity because receive diversity combining is performed with scalar operations in the frequency-domain. It is shown by computer simulation that the proposed receive diversity combining techniques achieve a performance gain over the conventional maximal ratio combining (MRC) techniques for SC-FDMA-based cooperative relay systems.

• Journal of Communications and Networks
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• v.11 no.3
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• pp.240-247
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• 2009

The results of performance analysis by adopting the channel scenarios characterized as Weibull fading for an multicarrierdirect sequence-coded division multiple access (MC-DS-CDMA) system are proposed in this investigation. On the other hand, an approximate simple expression with the criterion of bit error rate (BER) versus signal-to-noise ratio (SNR) method is derived for an MC-DS-CDMA system combining with maximal ratio combining (MRC) diversity based on the moment generating function (MGF) formula of Weibull statistics, and it associates with an alternative expression of Gaussian Q-function. Besides, the other point of view on the BER performance evaluation of an MC-DS-CDMA system is not only the assumption of both single-user and multi-user cases applied, but the phenomena of partial band interference (PBI) is also included. Moreover, in order to validate the accuracy in the derived formulas, some of the system parameters, such as Weibull fading parameter (${\beta}$), user number (K), spreading chip number (N), branch number (L), and the PBI (JSR) values, etc., are compared with each other in the numerical results. To the best of author's knowledge, it is a brand new idea which proposes the evaluation of the system performance for an MC-DS-CDMA system over the point of view with Weibull fading channel.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.191-192
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• 2008

We give new definition of the effective-leakage and the signal to effective-leakage plus noise ratio (SELNR) to consider receiver combining motivated by the leakage. We propose a method to find jointly beamforming vector and combining vector for the two linear receivers (maximal ratio combining (MRC) receiver and minimum mean square error (MMSE) receiver) based on the SELNR.

• ETRI Journal
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• v.17 no.4
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• pp.25-35
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• 1996

This paper derives the symbol error probability for quadrature amplitude modulation(QAM) with L-fold space diversity in Rayleigh fading channels. Two combining techniques, maximal ratio combining(MRC) and selection combining(SC), are considered. The formula for MRC space diversity is obtained by averaging the symbol error probability of M-ary QAM in an additive white Gaussian noise(AWGN) channel over a chi-square distribution with 2L degrees of freedom. The obtained formula overcomes the limitations of the earlier work, which has been limited only to deriving the symbol error rate(SER) of QAM with two branch MRC space diversity. The formula for SC space diversity is obtained by averaging the symbol error probability of M-ary QAM in an AWGN channel over the distribution of the maximum signal-to noise ratio among all of the diversity channels for SC space diversity has been reported yet. Analytical results show that the probability of error decreases with the order of diversity gain per additional branch decreases as the number of branches becomes larger. On the other hand, the performance of 16 QAM with MRC becomes much better than that of SC as the number of branches becomes larger. By giving the order of diversity, L, and the number of signal points, M, we have been able to obtain the SER performance of QAM with general space diversity. These results can be used to determine the order of diversity to achieve the desired SER in land mobile communication system employing QAM modulation.