• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1A
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• pp.1-7
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• 2012

The conventional Zhu's differential space-time modulation(DSTM) based on quasi-orthogonal design adopted a complex precoder in order to allow an independent joint detection of two complex symbols without any channel informations at a receiver. In this paper, by simply replacing the complex precoder used in Zhu's DSTM with a real precoder, a new DSTM is presented for four transmit antennas. The real precoder enables the receiver to decode two real symbols pair separately, and thus the new DSTM has greatly reduced decoding complexity compared to the Zhu's DSTM. By computer simulation results, the proposed scheme is shown to exhibit almost identical or improved error performance compared to the existing DSTMs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.431-439
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• 2010

In this paper, multiple-relay cooperative communication network with multiple antennas is considered. Applying the soft-decision-and-forward protocol to this system, pairwise error probability(PEP) is derived and then symbol error rate(SER) is also calculated. However, in general, signals are transmitted through the orthogonal channel in the multiple-relay cooperative communication network for the prevention of interference, which is inefficient in terms of the throughput. For the improvement of throughput, the relay selection is considered, where the relay having the maximum instantaneous end-to-end signal-to-noise ratio is chosen. Performance of the system is analyzed in terms of PEP and SER. As the number of the relay increases, relay selection method outperforms the conventional multiple-relay transmission system where all relays participate in the second time slot.

• The Korean Journal of Physiology and Pharmacology
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• v.12 no.6
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• pp.337-342
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• 2008

Human bone marrow mesenchymal stem cells (hBM-MSCs) represent a potentially valuable cell type for clinical therapeutic applications. The present study was designed to evaluate the effect of long-term culturing (up to $10^{th}$ passages) of hBM-MSCs from eight individual amyotrophic lateral sclerosis (ALS) patients, focusing on functional ion channels. All hBM-MSCs contain several MSCs markers with no significant differences, whereas the distribution of functional ion channels was shown to be different between cells. Four types of $K^+$ currents, including noise-like $Ca^{+2}$-activated $K^+$ current ($IK_{Ca}$), a transient outward $K^+$ current ($I_{to}$), a delayed rectifier $K^+$ current ($IK_{DR}$), and an inward-rectifier $K^+$ current ($K_{ir}$) were heterogeneously present in these cells, and a TTX-sensitive $Na^+$ current ($I_{Na,TTX}$) was also recorded. In the RT-PCR analysis, Kv1.1,, heag1, Kv4.2, Kir2.1, MaxiK, and hNE-Na were detected. In particular, ($I_{Na,TTX}$) showed a significant passage-dependent increase. This is the first report showing that functional ion channel profiling depend on the cellular passage of hBM-MSCs.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.2
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• pp.179-190
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• 1998

One of the most important topics of recent years is that a multimedia technology such as wireless ATM has been introduced in radio systems for video, voice and data transmission. A major problem in such systems is the occurrence of errors due to multipath fading or interference. To combat this problem, forward error correction (FEC) coding is commonly used as a means of eliminating these errors. This paper has analyzed theoretically the effect of fading to design effective wireless ATM system. The BER, CLR, and CER of wireless ATM system adopting FEC coding and diversity reception techniques have been derived in fading environment. Also, simulations of BER and CLR have been carried out and compared with the above theoretical results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.648-653
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• 2011

In this paper, coordinated space division multiple access(SDMA) technology is proposed to mitigate inter-cell interference by using partial channel state information in cooperative wireless communications system with limited feedback. Each AT selects an optimal cluster transmission mode and sends it back to a cluster scheduler, and at the cluster scheduler, ATs are scheduled within a AT group with the identical cluster transmission mode, and the optimal transmission mode and the corresponding scheduled ATs are determined to maximize scheduling priority. Also, in order to enhance multiuser diversity gain, an extended transmission feedback method is proposed to feed back multiple preferred cluster transmission modes at each AT. It is shown that the proposed coordinated SDMA scheme outperforms existing non-coordinated SDMA schemes in terms of the average system throughput.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.4
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• pp.193-200
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• 2013

Recently, network coding has been actively studied to increase the spectral efficiency of two-way relay wireless channels such as cellular systems as well as broadcasting systems. In this paper, we derive the average transmission capacity and the outage probability of a network coding system, which utilizes two-way data transmission via the best relay rather than multiple relays. Since the data unbalance between the forward and the reverse link in two-way communication systems exists, we include the asymmetric link as well as the symmetric link in the analysis. It is noticed that the space diversity gain increases as the increase of the number of relays. Also we obtain 11.4 dB signal-to-noise ratio (SNR) gain with 9 relays compared to that with single relay in symmetrical link at the given conditions. In asymmetrical links, we denotes that the outage probability is more sensitive to the number of relays rather than data unbalance between the links.

• Journal of Digital Convergence
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• v.18 no.3
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• pp.333-339
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• 2020

The lifestyle of the new consumer class of people with diversified social structures and tastes is affecting society as a whole. As of now, emerging lots of complex cultural space with unique sensibility and individuality, this paper is about proposing the branding of a complex cultural space. I selected Sounds Hannam as a cultural complex and conducted in-depth interviews about brand experience and Ethnography. The study found that Sounds Hannam needs sense of hearing and smell because the sensory factors of the Sounds Hannam are concentrated in the visual field, and also, there is a need to create an appropriate communication channel through SNS. The Sounds Hannam had the characteristic factors of sensibility, relaxation and content based on a diversity different from the existing one. Throughout research, it was derived that planning space as a place to inspire people through spatial composition that triggers behavior and creative thinking is the goal of a complex cultural space and at the same time, an effective way to reflect the lifestyle of those in 20s.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.378-390
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• 2001

In this paper, it is analyzed that the error performance of a Multi-Carrier DS-CDMA system in a single cell with multipath Rician fading and multiple access interference (MAI) and the error performance of the system is compared with that of a Sing1e-Carrier DS-CDMA system. Moreover, the convolutional coding techniques with code rate of 1/2, 1/3, and 1/4 are adopted in order to improve the error performance degraded by the multipath fading and MAI and performance improvement through the coding techniques is analyzed. As a result, it is shown that the number of users in each system can be determined by the number of branches of the rake receiver in a Single-Carrier DS-CDMA system and the number of carriers in a Multi-Carrier DS-CDMA system. Furthermore, the convolutional coding should be chosen with considering the trade-off between coding gain and a power limitation in a Multi-Carrier DS-CDMA system. In case of increasing the number of carriers, the processing gain is decreased but the error performance is improved through the effect of frequency diversity and the system can be possibility implemented due to the low chip rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4A
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• pp.378-383
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• 2004

Orthogonal Frequency Division Multiplexing (OFDM) transmits high-speed data by splitting the transmission bandwidth into a number of subcarriers. The bandwidth of each subcarrier is ensured to be smaller than the coherence bandwidth. This paper presents an OFDM system incorporated with the Carrier Interferometry (CI) codes to improve the performance by enhancing frequency diversity effect. The performances of CI-OFDM with multilevel modulations are investigated in highly dispersive fading channels. For the investigation of performance improvement of CI-OFDM, a simulator has been developed using a well-known SPW simulation platform. The simulation results show that the CI-OFDM provides both performance improvement and robustness against dispersive fading channel behavior. The performance of CI-OFBM with multilevel modulations demonstrates that CI-OFDM outperforms a traditional OFDM system, particularly in highly dispersive channels. With a relatively large delay spread of 151㎱ compared to the guard interval of 800㎱, CI-OFDM provides a BER of 10$^{-3}$ if sufficient signal power is present.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7A
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• pp.640-648
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• 2011

We propose relay selection schemes using STBC (Space Time Block Coding) technique in OFDM (Orthogonal Frequency Division Multiplexing)-based wireless systems. The proposed schemes select the optimum relay having the maximum instantaneous equivalent channel gain among multiple candidate relays. Also, in order to reduce the system overhead, a symbol grouping method which groups some amount of symbols before selecting the optimum relay is proposed. The simulation results show that the proposed relay selection schemes can obtain more selection diversity gain as the number of selectable relay candidates increases. Furthermore, the proposed scheme with the symbol grouping can reduce system overhead without any degradation of the performance in fading channels with low frequency selectivity.