• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.569-578
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• 2002

This paper proposes a new multicarrier code division multiple access (CDMA) system. The proposed multicarrier CDMA system provides the advantages that the transmission bandwidth is more efficiently utilized by using divided spreading sequence, time and frequency diversity is achieved in frequency selective nultipath (acting channel, and inter-carrier interference (ICI) can be minimized by using specific data and code pattern. In this system, transmitted data bits are serial-to-parallel converted to some parallel branches. On each branch each bit is direct-sequence spread-spectrum modulated by divided spreading sequences and transmitted using orthogonal carriers. The receiver providers a Rake for each carrier, and the outputs of Rakes are combined to get time and frequency diversity. This multicarrier CDMA system allows additional flexibility in the choice of system parameters. Upon varying system parameters, bit error rate (BER) performance is examined for the proposed multicarrier CDMA system. Simulation results show that the proposed multicarrier CDMA scheme can achieve better performance than the other types of conventional multicarrier CDMA systems.

• Mycobiology
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• v.43 no.4
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• pp.444-449
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• 2015

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in the rhizosphere and form symbiotic relationships with most terrestrial plant roots. In this study, four strains of Rhizophagus clarus were cultured and variations in their growth characteristics owing to functional diversity and resultant effects on host plant were investigated. Growth characteristics of the studied R. clarus strains varied significantly, suggesting that AMF retain high genetic variability at the intraspecies level despite asexual lineage. Furthermore, host plant growth response to the R. clarus strains showed that genetic variability in AMF could cause significant differences in the growth of the host plant, which prefers particular genetic types of fungal strains. These results suggest that the intraspecific genetic diversity of AMF could be result of similar selective pressure and may be expressed at a functional level.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.110-118
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• 2013

This paper describes the development of DSSS wireless communication uplink system for missile remote control. In consideration of low probability of intercept, low probability of exploitation, anti-jam, low latency, and doppler frequency offset, we used DSSS partially DBPSK. Also we used the selective diversity with two receiving antennas to mitigate multipath interference which is the dominant channel impairment and the turbo product code(TPC) for forward error correction(FEC) to improve bit error rate performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.6C
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• pp.403-411
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• 2011

This paper addresses a cooperative transmission scheme based on Alamouti coding for cognitive radio networks over frequency selective fading channels. In the proposed scheme, the Alamouti coded form at the destination node is constructed through a simple combination of symbols at the source node, instead of the time-reversal operation and the conjugate operation at the relay nodes used in the conventional scheme. Numerical results show that the proposed scheme achieves a higher order cooperative diversity than that of the conventional scheme.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.6
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• pp.43-49
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• 2014

In this paper, we consider the performance evaluation of space time block code (STBC)) with coordinate interleaved orthogonal design (CIOD) over time selective channel. In case of quasi static channel, STBC-CIOD satisfies full rate and full diversity (FRFD) property with the single symbol decoding. However in the time selective channel, the symbol interference degrades the system performance when we employ the single symbol decoding. We derive the union bound of the symbol error probability by evaluating the pairwise error probability in the first order Markov channel. We also present simulation results of STBC-CIOD with QPSK.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.5
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• pp.444-450
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• 2004

In mobile communications environment, STBC-OFDM(Space Time Block Code-Orthogonal Frequency Division Multiplexing) system with transmit diversity obtains the MRRC(Maximal Ratio Receiver Combining) diversity gain in time-invariant channel between two received symbols. But in time-variant channel, due to the interference between received symbols, MRRC diversity gain cant be obtained. So, when the mobile device with transmit diversity moves in high speed, the scheme to reduce the performance degradation due to the interference is needed. In this paper, we propose the receiver architecture with advanced transmit diversity, which improves the performance of STBC-OFDM system. The proposed architecture obtains the diversity gain without the change of transmit bandwidth at the receiver with the interference canceller using ZF(Zero Forcing) algorithm. Simulation results show performance improvement as doppler shift is increasing.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.53 no.4
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• pp.492-498
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• 2020

Despite its economic importance, olive flounder Paralichthys olivaceus aquaculture industry is facing a crisis with a continuous production decline. There have been many solutions to overcome the complicate predicament proposed. Increasing genetic diversity and discovering new commercial value through selective breeding are among them. The aims of the present study are to increase the selection power of the golden flounders. We examined the genetic diversity of the breeder population of golden flounders and developed selective markers for the golden flounder population. The 6 microsatellite (MS) markers were selected from melanogenesis-related genes, which are believed to be involved in the pigmentation of fish. All markers were polymorphic (except PO4) and 5 of them had PIC value of 0.6 or above. All makers had distinctive alleles indicating either normal or golden individuals. For examples, from PO4 marker, the frequency of an allele (316) in the golden population was 100% and in normal population was 0% (P<0.001). Although some more studies with more samples at the later generations should be performed to confirm this result, the 316 allele from PO4 marker could be a distinctive tool for decision of the colors in olive flounders at an early stage of the life cycle.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.3A
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• pp.267-273
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• 2006

This paper improves the effects of clustered OFCDM scheme considering the frequency diversity effect over a frequency selective fading channel. In OFCDM with frequency domain spreading compared to OFDM, we can increase uncorrelated symbols by frequency allocation method of correspondent symbols over the same antenna and different antenna after spreading. The simulation results show that the performance of proposed system is improved by approximately 4 dB in ${\sigma}=0.02{\mu}sec$, the performance is improved by approximately 2.5dB in large delay spread in a 12-path Rayleigh fading channel with overall the root mean squared delay spread and the maximum Doppler frequency of 20 Hz. Also, the required average received Eb/No at the average BER of $10^{-3}$ by optimum method is improved by approximately 2.0 dB, compared to that of STA-OFCDM with frequency rearrange. The new method does not require any bandwidth expansion any feedback from the receiver to the transmitter and its computation complexity is similar to clustered OFCDM.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.102-108
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• 2010

In this paper, we analyse the frequency diversity of BICM-OFDM with extended interleaving. The extended interleaving is an interleaving which is added to the existing BICM-OFDM system to extends the interleaving depth by times to the previous interleaving depth. Using the extended interleaving, the diversity order of the proposed system over -tap frequency selective channels is increased from min($d_{free}$, L) to min($d_{free}$, KL), where $d_{free}$ is minimum Hamming distance of the convolutional code. Simulation is also performed to show that the performance of the proposed system is better than that of the existing system even if the channel is an on-off channel in which the number of multi-paths is varying.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.12
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• pp.1-7
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• 2010

In this paper, the technique for obtaining diversity gain without increasing the antenna is proposed using symbol share in the OFDM systems. Proposed technique groups symbols which are mapped into different sub-carriers and these symbols are modulated by proposed constellation. Proposed constellation has the identical minimum distance with QPSK modulation constellation and obtain more frequency diversity gain. Also, proposed modulation scheme make it possible to increase data rate using subcarriers allocated symbols.