• Journal of Broadcast Engineering
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• v.9 no.1
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• pp.32-42
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• 2004

In this paper we apply space-time block code with multiple transmitter/receiver antennas to the Advanced Television Systems Committee (ATSC) terrestrial broadcasting systems. Especially, we apply Aiamouti scheme with two transmitter antennas and multiple receiver antennas to the ATSC broadcasting system. Also. diversity technique with multiple receiver antennas and space-time block code scheme with multiple transmitter/receiver antennas are compared. Our simulation results show that the ATSC broadcasting system with multiple transmitter/receiver antennas has an extremely good performance than the scheme with single transmitter/receiver antenna in the Rayleigh fading channel.

• Journal of Korea Multimedia Society
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• v.21 no.4
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• pp.493-498
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• 2018

In this paper, we provide the performance analyses of a dual-hop amplify-and-forward(AF) relay transmission composed of asymmetric radio-frequence(RF) and free-space optical(FSO) links. In the mixed RF/FSO system, a relay is equipped with two receive antennas for RF signals and one additional transmit antenna for FSO signals. In order to improve a performance of RF link, a switch-and-stay (SSC) diversity technique is applied at the relay which can provide a proper link performance with a low complexity. Specifically, we offer the performance analyses of the proposed system in terms of outage probability and secrecy outage probability. In numerical examples, we compare the system performances with no diversity and selection combining systems and verify our analytical results via computer-based Monte-Carlo simulations.

• ETRI Journal
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• v.26 no.5
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• pp.405-412
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• 2004

MC-CDMA, a multicarrier (MC) modulation scheme based on code division multiple access (CDMA), is the most likely candidate for the next generation of mobile radio communications. The rate compatible punctured turbo (RCPT) coded hybrid automatic repeat request (HARQ) has been found to give improved throughput performance in a direct sequence (DS) CDMA system. However, the extent to which the RCPT HARQ improves the throughput performance of an MC-CDMA system has not been fully understood. In this paper, we apply the RCPT HARQ to MC-CDMA and evaluate by computer simulations its performance in a frequency selective Rayleigh fading channel. We found that the performance of RCPT HARQ MC-CDMA is almost insensitive to channel characteristics. The performance can be drastically improved with receive diversity combined with space-time transmit diversity. In addition, the comparison of RCPT HARQ MC-CDMA, orthogonal frequency division multiplexing, and DS-CDMA shows that under similar conditions the throughput of MC-CDMA is the best in a frequency selective fading channel.

• Journal of electromagnetic engineering and science
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• v.12 no.2
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• pp.135-141
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• 2012

In this paper, we propose a novel cooperative routing protocol (NCRP) for wireless networks. The proposed protocol uses cooperative transmission to improve end-to-end outage probability. The broadcast nature ensures that the destination can receive a packet from the source or from the relays and if it cannot correctly decode the packet, the successful relays will start a retransmission. The NCRP protocol can skip some transmissions from the intermediate relays, thereby reducing the total power consumption. Theoretical results are derived and verified by simulation results.

• Journal of information and communication convergence engineering
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• v.2 no.2
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• pp.67-70
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• 2004

In this paper, we propose two novel high-rate high-performance space-time codes for multiple-input multiple-output (MIMO) systems. When $n_T$ transmit antennas and When $n_R$ ＝ When $n_T$ receive antennas are deployed, the two proposed codes respectively offer transmission rates of (When $n_T$ -1) and (When $n_T$ -2) symbols per channel use and diversity orders of 3 and 5. As a consequence, our proposed codes allow the MIMO systems to employ a simple detection technique based on QR decomposition. Moreover, for equal or even higher spectral efficiencies, our proposed codes always provide much better bit error rate (BER) performances than V-BLAST architecture does when When $n_R$ ＝ When $n_T$. Computer simulation is given to verify performances of our proposed codes.

• Journal of electromagnetic engineering and science
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• v.12 no.4
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• pp.287-289
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• 2012

This paper proposes an alternate time-switched space-frequency block coding transmission technique for orthogonal frequency division modulation systems. There are two antennas in the transmitter but it still has only a baseband and RF and a switch that alternates between the antennas at every symbol timing. Alternating transmit symbols result in zeros that make maximal ratio receive combining possible in the receiver. Simulation results show that it provides better performance than the traditional algorithm at the expense of one additional antenna.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.316-316
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• 2006

• Journal of Communications and Networks
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• v.17 no.3
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• pp.267-274
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• 2015

Due to the difficulty of coordination in the cellular uplink, it is a practical challenge how to achieve the optimal throughput scaling with distributed scheduling. In this paper, we propose a distributed and opportunistic user scheduling (DOUS) that achieves the optimal throughput scaling in a single-input multiple-output interfering multiple-access channel, i.e., a multi-cell uplink network, with M antennas at each base station (BS) and N users in a cell. In a distributed fashion, each BS adopts M random receive beamforming vectors and then selects M users such that both sufficiently large desired signal power and sufficiently small generating interference are guaranteed. As a main result, it is proved that full multiuser diversity gain can be achieved in each cell when a sufficiently large number of users exist. Numerical evaluation confirms that in a practical setting of the multi-cell network, the proposed DOUS outperforms the existing distributed user scheduling algorithms in terms of sum-rate.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.7
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• pp.55-61
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• 2004

This paper proposes an antenna selection and switching system between spatial multiplexing and diversity techniques. The proposed system overcomes spatial correlation by using antenna selection method and improve bit error performance with switching encoding nudes between a spatial multipexing encoder and a diversity encoder. Therefore, in a 4 transmit and 2 receive antenna system first, the proposed system selects 2 transmit antennas, and next, switches encoding modes between Space-Time Transmit Diversity and BLAST according to instantaneous channel information. Computer simulations showed that the proposed system improves about 2 or 3 ㏈ SNR in low correlated channel and about 3 ㏈ SNR in highly correlated channel rather than a 2 by 2 antenna switching system.

• The Korean Journal of Soil Zoology
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• v.3 no.2
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• pp.78-90
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• 1998

This study was carried out from May 1993 to October 1994 to examine diversity of oribatid mites in Namsan and Kwangreung coniferous forests, which were considered to receive different degrees of environmental pressures. Also, environmental factors (pH of soil and rainfall, litter depth, organic matter) were recorded in the two forests. The pH of soil and rainfall were not different between the two forests, but litter depth and organic matter were significantly higher in Namsan than in Kwangreung (p<0.05). The dominant families (>5% of the total densities) were Scheloribatidae(27.3%), Galumnidae(13.4%), Oppiidae (9.9%), Hypochthonidae(7.6%), Suctobelbidae(6.6%), Euphthiracaridae(5.9%) in Namsan and Ceratozetidae(25.9%), Mycobatidae (14.2%), Oppiidae(14.2%), Galumnidae(11.4%), Astegistidae(8.7%) in Kwangreung. The numbers of species were significantly higher in Kwangreung (103 spp.) than in Namsan (74 spp.)(p<0.05). The total densities of oribatid mites were more abundant in Kwangreung (8,709 ind.) than in Namsan (5,899 ind.) and the difference was significant for density in litter layer (p<0.05).