• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.1
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• pp.47-54
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• 1997

New algorithms for frequency channel assignment in small cellular mobile radio system are proposed. The algorithms are for a channel assignment method which control the transmitter power level based on the distance between the cell site and the mobile unit. These algorithms are such that any channel can be used by any cell site and mobile unit, as long as a required threshold level of carrier to interference ratio is maintained. As the cochannel reuse distance decreases, the proposed algorithms have given an increase in capacity in comparison to a fixed channel assignment.

• Journal of information and communication convergence engineering
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• v.2 no.4
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• pp.209-213
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• 2004

With the commercialization of CDMA 2000-1x late in 2000, a high-speed wireless Internet, based on a mobile communication networks, appeared in Korea. This will develop into the next-generation of mobile communications(4G) in the future and the new cell layout will be required the cellular configuration of 4G. We would need the legislation with respect to base-stations and to building the mobile communication networks, as well as the optimization of mobile communication systems. In this study, in order to provide 4G, I examined and analyzed that the current laws & regulations related to licensing and operating a mobile communication base-stations in KOREA.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.9
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• pp.6-13
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• 1993

In is well-known that system performance in the high speed digital radio communication system is usually deteriorted due to the frequency selective fading distortion. In this paper, bit error rate(BER) performance by the reception phase error in cellular mobile communication systems is derived and analyzed. The system is modeled as a frequency selective fast Rayleigh fading channel corrupted by additive white gaussian noise(AWGN) and co-channel interference(CCI). Our numerical results show that for the 24KBaud(48Kb/s) $\pi$/4-DQPSK operated at carrier frequency 800 MHz and C/I<20 dB, the BER will be dominated by CCI if the vehicular speed is below 100 Km/h. The results show that performance, when reception phase error is below $\pi$/12, is deterioreted less than 3 dB, and that performance, when reception phase error is above $\pi$/12, is degraded over 3 dB.

• Korean Journal of Microbiology
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• v.5 no.1
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• pp.1-6
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• 1967

The environmental effects on radio-sensitivities of Lactobacillus and Saccharomyces cerevisiae were studied; Liquid suspensions of Lactobacillus and yeast were gamma-irradiated under various conditions; temperatures, hydrogen ion concentrations, amino acids and vitamins were treated seperately with variations of concentrations. (shown in figures) It is found that simultaneous heat treatment is effective to sterilize microorganisms than pre after treatment, and concentration of hydrogen ion does not affect the lethalty of yeast but or Lactobacilli was affect at the range of pH. 5.0 to 7.0. Ascorbic acid, thiamin and pyridoxine were protective dependently against lethal action of gamma-ray and its protective effects increase with the increasings of concentrations. Glutamic acid, aspartic acid, tyrosine and phenylalanine were proved to be protective for both strains at 0.1 between 1.0 percent. It can be suggested that industrial sterilizing doses of irradiation by gamma-ray for food should be applied more than those dose of saline or buffer suspension, because natural food stuffs are rich of vitamins and amino acids.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.22 no.51
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• pp.139-149
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• 1999

Developed in this paper is a prototype extranet using mobile device such as Personal Digital Assistance(PDA) or Handheld PC(HPC). Especially an adjustment transaction system for auto insurance using wireless data communications is described. Using infrastructures such as PCS, Cellular, Private Radio, wireless communications offers tremendous applications in Korea. A survey of such applications is presented in this paper. Also an analysis of currently available infrastructures of wireless communications is described in this paper. The scheme of an adjustment transaction consists of seven steps: (1) get list of adjustment, (2) obtain insurance information, (3) check police record, (4) get an accident record, (5) get bluebook value, (6) examine the car, (7) file report. Comparing with the previous on-line method that spends much time on gathering data, the proposed system guarantees more rapid transaction using wireless communications.

• Proceedings of the Korea Society for Simulation Conference
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• 2000.04a
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• pp.25-29
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• 2000

핸드오프 영역내에 정해진 RSS(Radio signal strength)에서 핸드오프를 시행하는 기존의 정적 핸드오프방식은 셀룰러 네트워크에서 제어신호가 증가하여 전송지연을 유발한다. 그러므로 핸드오프 수를 줄이는 방안으로 SPPQ(Signal Prediction Priority Queuing)에 기반한 동적 핸드오프를 제안한다.SPPQ는 RSS에 근거하여 선형적으로 핸드오프의 가능성을 예측한 후, 핸드오프 순서를 결정하는 알고리즘이다. 이 때 실제 속도와 호의 위치 분포는 일정하다고 가정하고 RSS에 대한 $\Delta$RSS(신호 세기의 증감)을 이용한다. SPPQ는 핸드오프 결정을 위해 선형적으로 RSS를 예측하며, 시간 구간에서 구한 시그널 평균을 사용한다. 그리고 두 개의 가장 최근 평균 RSS 측정값에 의해 표현되는 선형 방정식이 시간 축과 만나는 교차점을 핸드오프 예상시점으로 결정한다. 이때 각 핸드오프 후보 단말들의 threshold는 다르게 줄 수 있으며 그에 따라 우선순위를 결정한다. 이 우선순위를 기본으로 하여, 핑퐁효과로 인한 불필요한 핸드오프를 줄일 수 있도록 표본화 시간 $\Delta$t만큼 핸드오프를 낮춰 SPPQ의 성능을 높인다.

• Electronics and Telecommunications Trends
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• v.8 no.1
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• pp.69-76
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• 1993

급증하는 이동 통신 수요를 충족시키고, 통신망의 ISDN(Integrated Services Digital Network)화에 부응하기 위해 현 애널로그 방식에 디지틀 방식의 도입, 전환이 불가피하다. 이에 따라 디지틀 이동통신의 한 방식으로 QUALCOMM사에 의해 제안된 CDMA(Code Division Multiple Access) 방식에 대한 표준화 작업이 TIA(Telecommunications Industry Association)의 소위원회 TR45.5 에 의해 진행되고 있다. 본 고에서는 CDMA 방식의 표준화를 위한 미국의 TIA, CTIA(Cellular Telecommunications Industry Association) 소위원회의 구성 및 역할 등에 관해, 그리고 위 소위원회의 요구에 의해 QUALCOMM사, Ericsson Radio System사, 및 SCS Mobilecomm사 등의 3개사가 제안한 방식들을 중심으로 CDMA 기술의 현황을 소개한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2664-2673
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• 1997

The signal fading distortion has effect on the capacity of cellular mobile communication systems. The short term fading is solved by signal processing techniques depending on the radio communication methods, but another distortion compensation techniques are necessary to combat long term fading. in this paper, we have simulated the call processing in DS-CDMA system using distributed antennas to overcome the long term fading. From the simulation results, we have conformed that the blocking probability of a new call andthe forced probability of handoff-request-call have decreased by increasing the number of distributed antennas.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2340-2342
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• 2003

본 논문에서는 최적 전력 제어를 이용하여 이동국과 기지국간 최소의 소비 전력과 최대의 채널용량을 유지할 수 있는 알고리즘을 제안하고자 한다. 이동통신 시스템은 한 기지국 안에 속한 가입자 사이에 간섭이 발생할 뿐 아니라 동일한 대역을 사용하는 기지국 사이에도 간섭이 발생하게 된다. 또한 이동통신 시스템은 열악한 무선 환경을 기반으로 수시로 변화하는 가입자 요구를 수용해야 한다. 따라서 가입자 요구에 적절히 대응하는 최적 전력 제어가 이루어져야 원활한 서비스를 가입자들에게 제공할 수 있다. 즉, 동시 통화를 시도하는 여러 가입자들 간의 간섭을 받지 않고 알맞은 통화의 질을 제공받을 수 있도록 하는 전력 제어의 과정이 필수적이다.

• Journal of Korea Multimedia Society
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• v.11 no.12
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• pp.1697-1705
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• 2008

Several studies made for wireless mesh networks aim to optimize the capacity for wireless networks. Aside from protocol improvements, researches were also done on the physical layer particularly on modulation techniques and antenna efficiency schemes. This paper is concerned with the capacity improvements derived from using spatial diversity with smart adaptive array antennas. The use of spatial diversity, which has been widely proposed for use in cellular networks in order to lessen frequency re-use, can be used in mesh networks both to minimize co-channel interference (CCI) and enable multiple transmissions. This paper aims to study the capacity region and bounds in using smart antennas for single-channel multi-radio systems in relation to the number of spatial diversity or sectors as defined by the beam angle $\beta$.