• Journal of Communications and Networks
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• v.13 no.3
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• pp.240-249
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• 2011

Cooperative diversity protocols have attracted a great deal of attention since they are thought to be capable of providing diversity multiplexing tradeoff among single antenna wireless devices. In the high signal-to-noise ratio (SNR) region, cooperation is rarely required; hence, the spectral efficiency of the cooperative protocol can be improved by applying a proper cooperation selection technique. In this paper, we present a simple "cooperation selection" technique based on instantaneous channel measurement to improve the spectral efficiency of cooperative protocols. We show that the same instantaneous channel measurement can also be used for relay selection. In this paper two protocols are proposed-proactive and reactive; the selection of one of these protocols depends on whether the decision of cooperation selection is made before or after the transmission of the source. These protocols can successfully select cooperation along with the best relay from a set of available M relays. If the instantaneous source-to-destination channel is strong enough to support the system requirements, then the source simply transmits to the destination as a noncooperative direct transmission; otherwise, a cooperative transmission with the help of the selected best relay is chosen by the system. Analysis and simulation results show that these protocols can achieve higher order diversity with improved spectral efficiency, i.e., a higher diversity-multiplexing tradeoff in a slow-fading environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.6
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• pp.13-19
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• 2008

In this paper, the new cooperative communication techniques is proposed for multi-input multi-output(MIMO)-orthogonal frequency division multiplexing (OFDM) system using the relay with multiple antenna. As the MIMO channel is formed by space time coding at the MS(mobile station)-RS(relay station) and RS-BS(base station), we can get the cooperative diversity and MIMO diversity gain simultaneously. Therefore, the performance of MIMO-OFDM system using the relay with multiple-antennas is very improved. And the simple power allocation technique is Proposed for the transmitting power of the mobile station and the relay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.9
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• pp.1573-1595
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• 2011

In this paper, the outage performance of multiuser multiple-input single-output (MISO) systems exploiting joint spatial and multiuser diversities is investigated for Rayleigh fading channels with outdated feedback. First, we derive closed-form exact outage probabilities for the joint diversity schemes that combine user scheduling with different spatial diversity techniques, including: 1) transmit maximum-ratio combining (TMRC); 2) transmit antenna selection (TAS); and 3) orthogonal space-time block coding (OSTBC). Then the asymptotic outage probabilities are analyzed to gain more insights into the effect of feedback delay. It is observed that with outdated feedback, the asymptotic diversity order of the multiuser OSTBC (M-OSTBC) scheme is equal to the number of transmit antennas at the base station, while that of the multiuser TMRC (M-TMRC) and the multiuser TAS (M-TAS) schemes reduce to one. Further by comparing the asymptotic outage probabilities, it is found that the M-TMRC scheme outperforms the M-TAS scheme, and the M-OSTBC scheme can perform best in the outage regime of practical interest when the feedback delay is large. Theoretical analysis is verified by simulation results.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.121-126
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• 2015

This paper proposes a novel reconfigurable microstrip antenna based on alternating a perturbation structure to achieve circular polarization diversity. The proposed antenna consists of an annular ring microstrip radiator for simultaneously loading stub and slot perturbations which support right- and left-handed circular polarization senses and two PIN diodes for choosing the operating polarization sense. By controlling the states of two PIN diodes between perturbing slot and stub at one diagonal corner of the radiator, reconfigurable circular polarization senses of the proposed antenna are successfully obtained and alternated. The proposed antenna has been theoretically analyzed and experimentally demonstrated at 2.4 GHz of S-band for satellite communication system. The simulation and measurement results of the proposed antenna show in good agreement with the reflection coefficients, axial-ratios, realized antenna gains, and radiation patterns.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.298-307
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• 2002

This paper concentrates on developing and analyzing an advanced space-time multiuser receiver for WCDMA forward link. Through exploring the interference caused by co-channel users and delayed multipaths in CDMA, a constrained linear adaptive filter is adopted to cancel the interference. Furthermore, by utilizing the space-time diversity, an optimum diversity receiver, called a constrained adaptive space-time interference canceller (C-ASTIC), is proposed. For comparison, the statistical analysis of multiuser performance for WCDMA system with space-time diversity is described. The result of the simulation showed that C-ASTIC performs better than both the space-time diversity combining maximal ratio combiner (MRC) and the single-antenna adaptive interference canceller in a multipath fading channel. Also, the efficiency of the C-ASTIC in the multimedia communication environment is investigated under the multiuser, multi-transmit antenna, and multirate WCDMA system in a multipath fading channel. From the results, the C-ASTIC was validated to be useful for multi-rate WCDMA system through improving the performance gain by more than 3 dB at BER of 10$\^$-3/ in a half or more loaded system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1626-1631
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• 2004

OFDM are digital modulation techniques where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of OFDM systems with various antenna structure are analyzed, where data is transmitted over multi-path Rayleigh fading channel. The performance of this technique, gauged by the average bit error rate, is analyzed for the OFDM systems dependent upon the various antenna diversities.

• ETRI Journal
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• v.34 no.2
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• pp.264-267
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• 2012

This letter analyzes the performance of a two-hop MIMO multiuser relay network with a fixed gain amplify-and-forward protocol and antenna selection at the transmitter and receiver. A new expression for the cumulative distribution function of the highest instantaneous end-to-end signal-to-noise ratio is derived. Based on the above result, closed-form expressions for outage probability and bit error rate are presented. Also, the diversity order of the system is determined. Finally, computer simulations are compared to the analytical results, and insights and observations are provided.

• Journal of information and communication convergence engineering
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• v.3 no.2
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• pp.67-71
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• 2005

Interference occurs by signals received from directions that were different from the signals of the users in a mobile communication system. Various studies have been undertaken, including diversity, equalizer, etc., in order to reduce interference. In this study, the weighted value of the array antenna was obtained to improve signal-to-noise ratio. The weighted value was obtained as an eigen value and an eigen vector by using the correlation coefficient of the signal. The weighted value obtained was then applied to the CDMA system to increase system performance and capacity. Both QPSK and OQPSK modulation systems were applied to analyze performance.

• Animal Systematics, Evolution and Diversity
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• v.20 no.1
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• pp.1-8
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• 2004

The first zoea of R. uritai is described in detail, based on laboratory-hatched material. The first zoea of R. uritai can be distinguished from that of R. conspiciocellus and R. durbanensis by the rostrum downwards, overreaching distal margin of the outer flagellum of the antenna, the endopod of the antenna with short seta as well as long plumose seta distally, and the scale of the antenna six-segmented. The shape of the telson can be a distinguishing character of the first zoea of Rhynchocinetes from that of Cinetorhynchus.

• ETRI Journal
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• v.44 no.1
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• pp.117-124
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• 2022

In this paper, the performance of precoding-aided differential spatial modulation (PDSM) systems with optimal transmit antenna subset (TAS) selection is examined analytically. The average bit error rate (ABER) performance of the optimal TAS selection-based PDSM systems using a zero-forcing (ZF) precoder is evaluated using theoretical upper bound and Monte Carlo simulations. Simulation results validate the analysis and demonstrate a performance penalty < 2.6 dB compared with precoding-aided spatial modulation (PSM) with optimal TAS selection. The performance analysis reveals a transmit diversity gain of (N_T-N_R+1) for the ZF-based PDSM (ZF-PDSM) systems that employ TAS selection with N_T transmit antennas, N_S selected transmit antennas, and N_R receive antennas. It is also shown that reducing the number of activated transmit antennas via optimal TAS selection in the ZF-PDSM systems degrades ABER performance. In addition, the impacts of channel estimation errors on the performance of the ZF-PDSM system with TAS selection are evaluated, and the performance of this system is compared with that of ZF-based PSM with TAS selection.