• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.334-341
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• 2000

This paper presents an analysis of the capacity, the interference of adjacent cells of a CDMA cellular system, depending on the soft handoff region and log-normal shadowing. The optimum soft handoff region is chosen by using Erlang capacity. It is shown that when the soft handoff region increases, the Erlang capacity increase due to a reduction of the interference power of adjacent cells. But if the region is increased above a certain value, there is no improvement in the system’s capacity. Furthermore as the standard deviation of the log-normal shadowing's normal distribution factor increases, the soft handoff region has to be increased linearly to achieve the same Erlang capacity.

• Journal of Ginseng Research
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• v.34 no.3
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• pp.198-204
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• 2010

Korean ginseng (Panax ginseng C.A. Meyer) preserved in syrup, known as ginseng Jung Kwa (GJK), is a popular traditional snack in Korea. We investigated the effects of heat processing time on total phenolic content and antioxidant capacity of GJK. Water extract was prepared from GJK with different heat processing times, 3 hours (GJK-3), 6 hours (GJK-6), or 12 hours (GJK-12), with sonication for 2 hours. The GJK extract contained total phenolic content in the following order: GJK-12 (2.28%)>GJK-6 (1.57%)>GJK-3 (1.29%). Both the peroxy and hydroxyl radical-scavenging activity and cellular antioxidant capacity of GJK extract was significantly enhanced with increasing heat processing time. The hydroxyl radical-scavenging activity of GJK-12 extract was greater than that of the GJK-3 and GJK-6 extracts, consistent with metal chelating capacity and reducing capacity. In a cellular model, the GJK extract effectively reduced 2,2'-azobis(2-amidinopropane) dihydrochloride, $Cu^{2+}$-, and $H_2O_2$-induced oxidative stress, with GJK-12 and GJK-6 extracts demonstrating greater cellular antioxidant capacity than the GJK-3 extract. These results suggest that heat processing time can contribute to the antioxidant capacity of GJK and that GJK extract may have the potential to be used as an effective dietary antioxidant to prevent oxidative stress-related diseases.

• Proceedings of the IEEK Conference
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• summer
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• pp.10-14
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• 2004

When providing flexible data transmission for future CDMA(Code Division Multiple Access) cellular networks, problems arise in two aspects: transmission rate. This paper has proposed an approach to maximize the cellular network capacity by combining the genetic transmission rate allocation and a rapid power control algorithm. We present a genetic chromosome representation to express call drop numbers and transmission rate to control mobile's transmission power levels while handling their flexible transmission rates. We suggest a rapid power control algorithm, which is based on optimal control theory and Steffenson acceleration technique comparing with the existing algorithms. Computer simulation results showed effectiveness and efficiency of the proposed algorithm Conclusively, our proposed scheme showed high potential for increasing the cellular network capacity and it can be the fundamental basis of future research.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.62 no.4
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• pp.216-222
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• 2013

Handover is a technical methodology to support mobility of wireless communication users, which mainly affects the capacity of wireless communication systems and the quality of service (QoS) of link level signal. However, in OFDMA-based cellular systems, there are few published technical reports investigating handovers with respect to diversity gains and resource consumption depending on what handover technique is adopted. In this paper, we propose handover schemes exploiting transmit diversity and macro-diversity in order to increase capacity of OFDMA-based wireless communication systems, and analyze their performance. In cellular environments, depending on what handover scheme is selected, average signal-to-interference-and-noise ratio is calculated first for a handover user in order to evaluate the link level QoS. Through this technical evaluation for handover schemes, we conclude what handover scheme is suitable for OFDMA-based cellular systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.8C
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• pp.689-695
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• 2007

Wireline relay stations(RS's) are connected to cellular base stations(BS's) via radio-over-fiber(RoF) to enhance system capacity and to reduce shadow areas. Unlike wireless multi-hop systems, BS-to-RS signaling is transmitted out-of-band, thus reducing the effect of interference caused by frequency reuse. In this paper, antenna arrays used in addition to the wireline RS's are considered to evaluate the transmission capacity gain and performance variations according to the may structures. In particular, RS locations to maximize the gain, may distribution patterns for a given number of antenna elements, performance enhancement for a varying number of elements are experimentally determined to suggest a proper utilization of antenna ways in conjunction with wireline RS's.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.6
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• pp.517-532
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• 1991

This paper shows performance analysis for FH/MF나 systems over the cellular mobile communication channel. The Channel capacity over FH/MF나 system is represented as a function of deletion probalblity (Po) and insertion probalbility(Pt). The spectral efficiency of the system serves as a per formance of cellular system is inferior to that of non cellular system. In the case of frequency reuse, we get the best performance when the reuse pattern(N) is 3.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.2
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• pp.471-482
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• 1996

In this paper, we analyze the effect of imperfect power control on the capacity of the reverse channel in CDMA cellular system with antenna arrays in the base station. For imperfect power control, we assume that the received power at the base station from the users within each cell has log-normal distribution, and we also consider the effect of imperfect power control of co-channel interferences which arise from both its own cell and outer cells. From the result of numerical analysis, we show that the degree of power control gives a great influence on the capacity of CDMA celluar system with antenna arrays, and also that antenna arrays at the base station can improve greatly the system capacity even when the power control is imperfect.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.149-152
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• 2000

In this paper, the reverse link performance of an imperfect power controlled DS/CDMA cellular system that uses a base station array antenna which can effectively remove the multiple access interference is analyzed considering both beam forming algorithm and power control error in shadowing. The blocking probability of the DS/CDMA cellular system based on array parameters, Eb/No and statistics of interference is derived, and then the system capacity corresponding to a certain blocking probability is calculated. On the assumption that the blocking probability is set 1 ％, the system capacity using MCGM algorithm with 12 antenna arrays is increased about 59 % than that using 8 antenna arrays when power control error is 2.5 ㏈.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.4
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• pp.37-46
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• 1996

In this paper, we analyzed the performance improvement of the DS-CDMA/dPSK cellular mobile communication system with CCI canceller and RAKE receiver techniques in mobile radio channel which is characterized by AWGN, Multi-user interference (mUI) and frequency-selective rayleigh fading. System capacity i.e., number of user per cell has been derived and the evaluated results are shown in figuraes as a function of PN code sequence length, number of RAKE receiver tap, BER and E$_{b}$/N$_{o}$. The voice activity factor is assumed to be 3/8 the number of sectors in a cell 3 and MUI is modeled as gaussian process. From the results, the capacity of the DS-CDMA/DPSK cellular mobile communication system is improved by adopting CCI canceller. When we adopt the RAKE receiver to mitigate the multipath fading, the error performance is improved and the amount of improvement is proportional ot the number of taps L in the case that each tap contains a signal component and the better of improvement can be obtained, the smaller of the SNR difference in each tap. The system capacity is more increased when the CCI canceller and the RAKE receiver is used in cascade.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.3
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• pp.1-7
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• 1989

A new algorithm for frequency channel assignment in high capacity cellular mobile communication systems is proposed. The algorithm is the advanced type of the fixed channel assignment scheme. It enables calls having all nominal channels busy to be served by adjacent cells have idle channels. Thus, it considerably reduces the blocking probability compared with the fixed channel assignment. Simulation has been performed for a 49-cell system having uniform traffic density hexagonal array as a representative system lay out. Results showed that new algorithm is better than the fixed channel assignment scheme in high capacity cellular mobile communication systems.