• 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.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.6 no.3
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• pp.75-79
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• 1995

This paper derives the symbol error rate (SER) for quadrature amplitude modulation (QAM) with L-fold selection combining (SC) space diversity in Rayleigh fading channel. No analysis has been reported yet for theoretical SER performance of QAM with SC space diversity in Rayleigh fading channels. The formula is obtained by averaging the symbol error probability of M-ary QAM in an additive white Gaussian noise channel over the distribution of the maximum signal-to-noise ratio among all of the diversity channels. 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 SC space diversity. Analytical results show that the probability of error decreases with the order of diversity. We can also see that the incremental diversity gain per additional diversity decreases as the number of branches becomes larger.

• Journal of electromagnetic engineering and science
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• v.6 no.4
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• pp.222-228
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• 2006

In this paper, the performance of a multiuser diversity system combined with a multi-element transmit antenna system is analyzed under the assumption of independent Rayleigh fading. A measure of system .level performance is an average channel capacity as a function of the number of users and antennas. Average channel capacity is obtained from the instantaneous signal-to-noise ratio(SNR) distribution combined by both transmit diversity(TD) at each link and multiuser diversity at system level. Numerical results show that closed-loop antenna techniques provide an additional gain with multiuser diversity system due to array gain, even though space diversity gain reduces multiuser diversity gain. On the other hand, the space-time block coding(STBC) that provides full order space diversity gain only has a destructive influence on multiuser diversity.

• Journal of electromagnetic engineering and science
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• v.6 no.3
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• pp.189-195
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• 2006

In this paper, the derivation of the protection ratio for the digital microwave system with diversity is newly suggested for a basic guidance of initial planning for frequency coordination, and computational results are presented for an actual radio frequency band. The net filter discrimination has been also examined to see the effect of the adjacent channel protection ratio caused by adjacent channel interference. In addition, the protection ratios for the space or frequency diversity system are analyzed in terms of diversity improvement factors to find out an equivalent allowable noise-to-interference ratio (N/I) from degraded fade margin. According to results for 6.2 GHz system, with the space diversity of 25 m distance between antennas or the frequency diversity of ${\Delta}f/f=0.05$, under 64-QAM and 60 km at BER $10^{-6}$, the protection ratio can be greatly reduced in comparison to the non-diversity system. So, assuming that only the same protection ratio as the non-diversity system is kept, it is shown that the system with diversity may get more interference level of N/I allowing from 9.0 to - 5.9 dB or from 6.0 to - 4.3 dB for the space or frequency diversity. In consequence, it is concluded that the diversity system is more robust or tolerable for interferences or fades, which may play an important role in overcoming N/I to some extent.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.6
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• pp.989-1005
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• 2010

Cooperative diversity is a technique with which a virtual multiple antenna array is established among the single antenna users of the wireless network to realize space diversity. Signal space diversity (SSD) is a bandwidth-efficient diversity technique, which uses constellation rotation and interleaving techniques to achieve diversity gain. A new cooperative diversity scheme with rotated constellations (RCCD) is proposed in this paper. In this scheme, data are modulated by using a rotated constellation, and the source and the relays transmit different components of the modulated symbols. Since any one of the components contains full information of the symbols, the destination can obtain multiple signals conveying the same information from different users. In this way, space diversity is achieved. The RCCD scheme inherits the advantage of SSD - being bandwidth-efficient but without the delay problem of SSD brought by interleaving. The symbol error rate of the RCCD scheme is analyzed and simulated. The analysis and simulation results show that the RCCD scheme can achieve full diversity order of two when the inter-user channel is good enough, and, with the same bandwidth efficiency, has a better performance than amplify-and-forward and detect-and-forward methods.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.4
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• pp.200-205
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• 2011

In multipath fading channel, diversity is essential to mitigate the impairments. In this paper, we have proposed the angle diversity scheme called ATTD(Angle Time Transmit Diversity) instead of Alamouti's STTD(Space Time Transmit Diversity) and have analyzed the performance of the proposed scheme when signal powers caused by the transmission to different angles are different. Based on it, we have measured the wireless vector-channel in the urban area, which has lots of high-story buildings, using the data collected from the 8 by 4 smart array antenna system that we made. According to the measured data, the received signals from different angles have different signal powers. Our performance analysis results show that the proposed scheme has better performance than the space diversity scheme when the received path signal power is at least -7dB compare to the strongest path signal power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11A
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• pp.1043-1052
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• 2008

This paper compares the performances with space time coding and cyclic delay diversity techniques for OFDM systems in interference-limited environments. While a communication system usually use a diversity technique to improve its own performance, it is also necessary to consider the interference effects to other users as well if the system is operated in interference-limited environments. When there is no interference from or to other users, space time coding technique results in better performance than cyclic delay diversity. However, cyclic delay diversity can be better than space time coding if interferences to other users are considered.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.766-776
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• 1999

In this paper to evaluate the performance of the polarization diversity and the space diversity in the indoor environment, we used 3D Ray-tracing simulation. This model is capable of predicting small scale fading characteristics of the channel for evaluating the performances of both the polarization and the space diversity scheme. The measurement and simulation results show that the polarization diversity and the space diversity are expected to be efficiently used for the indoor environments. Moreover, the results show that the proposed polarization diversity technique using directional dual polarization microstrip array antennas has more diversity gain than the conventional polarization and space diversity using dipole antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12A
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• pp.1145-1151
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• 2010

Hochwald et al. introduced unitary space-time codes for quasi-static Rayleigh fading channels which allows for noncoherent decoding when the channel response is not known at the receiver. However, when reliable information on the channel response is available, coherent decoding is preferable for improved performance. Here, we study the relationship between the performance criteria on the diversity and coding advantages provided by unitary space-time codes with noncoherent and coherent decoding. We show that when a unitary space-time code achieves full spatial diversity with noncoherent decoding, full spatial diversity is also guaranteed with coherent decoding.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.6
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• pp.81-88
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• 2012

Space diversity and space multiplexing gain can be achieved with MIMO system. This paper proposes spatial coding method to MIMO system using data information and antenna selection technique. This technique provides coding gain as well as space diversity gain. For MIMO system with BPSK modulation, BER performance is analyzed and space diversity gains are compared through simulation in terms of data maldistribution degree.