• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.1
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• pp.109-119
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• 2013

This paper presents the design of the Safety Programmable Logic Controller (SPLC) used in the Nuclear Power Plants, an analysis of a reliability for the SPLC using a markov model. The architecture of the SPLC is designed to have the multiple modular redundancy composed of the Dual Modular Redundancy(DMR) and the Triple Modular Redundancy(TMR). The operating system of the SPLC is designed to have the non-preemptive state based scheduler and the supervisory task managing the sequential scheduling, timing of tasks, diagnostic and security. The data communication of the SPLC is designed to have the deterministic state based protocol, and is designed to satisfy the effective transmission capacity of 20Mbps. Using Markov model, the reliability of SPLC is analyzed, and assessed. To have the reasonable reliability such as the mean time to failure (MTTF) more than 10,000 hours, the failure rate of each SPLC module should be less than $2{\times}10^{-5}$/hour. When the fault coverage factor (FCF) is increased by 0.1, the MTTF is improved by about 4 months, thus to enhance the MTTF effectively, it is needed that the diagnostic ability of each SPLC module should be strengthened. Also as the result of comparison the SPLC and the existing safety grade PLCs, the reliability and MTTF of SPLC is up to 1.6-times and up to 22,000 hours better than the existing PLCs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.459-462
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• 2005

In this paper, we investigate the high precision location estimation algorithm in 2.45GHz band RTLS with multiple tags. The location is estimated in LOS environments, 300m ${\times}$ 300m area, and 2D coordinates adopting a TDOA scheme which is not necessitate the transmission time of tags. We evaluate the average estimation error in distance assuming that tags are randomly distributed and the readers(3${\sim}$8) are uniformly(equal space) placed in test area. In results, average estimation error is 3.12m and 1.47m at reader numbers of 4 and 8, respectively. Minimum estimation error is obtained when the accumulated receiving signal from a tag is 3 or 4 regardless of available reader numbers. The error is less than 3m, satisfies the specification of RTLS.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.549-552
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• 2005

Multiple wireless devices in wired and wireless heterogeneous networks communicate with counterparts via a single access point (AP). In this case, the AP becomes a bottleneck of the network, therefore buffer overflows occur frequently and result in TCP performance degradation. In this paper, a new algorithm that prevents buffer overflows at AP and enhances TCP fairness is proposed. Depending on the buffer usage of AP, the new algorithm adaptively controls each TCP senders' transmission rate, prevents buffer overflows and thus guarantees improved TCP fairness. It is proved that the algorithm makes better of TCP throughput and fairness by preventing buffer overflows.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7941-7948
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• 2015

Rolling noises during train operation are caused by vibration excited from irregularities of surface roughness between wheel and rail. Therefore, a proper measurement and analysis techniques of acoustic roughness between wheel and rail surface are required for transmission, prediction, and analysis of the train rolling noise. However, since current measuring devices and methods use trolley-based manual handling devices, the measurements induce unstable measuring speed and vibrational interface that increases errors and disturbances. In this paper, a new automatic rail surface exploring platform with a speed controller has been developed for improving measurement accuracy and reducing inconsistency of measurements. In addition, we propose a data integration method of the rail surface roughness with multiple homogeneous displacement sensors and verified the accuracy of the integrated data through standard test-bed railway track investigation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.51-56
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• 2007

Unitary matrix modulation (UMM) is investigated in multiple antennas system that is called unitary space-time modulation (USTM). When we consider only diagonal components of UMM with splitting over the coherence bandwidth, the system can obtain frequency diversity in a single antenna system. In Rayleigh fading channel, we compared USTM/OFDM with 2Tx-antenna with UMM-S/OFDM with 1Tx-antenna, conventional multi-level OFDM and UMM-S/OFDM with changing bit rate per Hz. Also, we analyzed SNR for between multi-level modulation STBC/OFDM and multi-level modulation UMM-S/OFDM with changing transmission rate. When it was adaptive multi-level modulation to improve SNR, we did the UMM-S/OFDM system performance analysis of N-ary PSK and M-ary QAM.

• The KIPS Transactions:PartC
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• v.10C no.6
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• pp.727-738
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• 2003

Much research efforts are being exerted for the study of intrusion detection system(IDS). However little work has been for the communication medels and performance eveluation of the IDS. Here we present a communication framework for doing hybrid intrusion detection in which agents are used for local intrusion detections with a centralized data anaysis componenta for a global intrusion detection at multiple domains environment. We also assume the combination of host-based and network-based intrusion detection systems in the oberall framework. From the local domain, a set of information such as alert, and / or log data are reported to the upper level. At the root of the hierarchy, there is a global manager where data coalescing is performed. The global manager delivers a security policy to its lower levels as the result of aggregation and correlation of intrusion detection alerts. In this paper, we model the communication mechanisms for the hybrid IDS and develop a simular using OPNET modeller for the performance evaluation of transmission capabillities for the delivery of data and policy. We present and compare simulation results based on several scenarios focuding on communication delay.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.12
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• pp.2653-2663
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• 1997

The successive and parallel interference cancellation schemes are two well-known types of multi-stage interference cancellation schemes using the conventional correlator receivers as a basic building block, which has been known to significantly improve the performance of DS/CDMA system in the multiple access communication. Performance comparison between these two schemes is made strictly based on the analytical and it has been shown that the successive interference cancellation (SIC) scheme is more resistant to fading than the parallel interference cancellation (PIC) scheme. We further investigate the performance of the successive IC scheme subject to the delay constraint, which may be imposed typically on most of service applications with a real-time transmission requirement, including speech and video applications. Our analysis demonstrates that the performance may be significantly improved by the groupwise successive interference cancellation (GSIC) scheme, which can be properly optimized to meet the given delay constraint.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.4
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• pp.692-698
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• 2001

The radio communications by SSB and VHF transceivers are still used very efficiently in coast stations and military base stations. The communication system by the conventional SSB and VHF transceivers between a coast station and a terminal is an one-to-one system. In this dissertation, however, the conventional one-to-one system is expanded to one-to-multiple systems. Then, frequencies can be used effectively for distress, urgency, safety traffic, and military communications. An ICS has been proposed and added, in this dissertation, to the conventional SSB and VHF communication systems, which can realize one-to- several terminal communications. The line switching system by the ICS is to be remote-controlled by ASK modulated PTT signals and audio signals. An ICS can change a connection between terminal and transceiver through a circuit switching system at any time. For this purpose, the author has researched and developed a ASK transmission system, ICS system, control algorithm, multiprocessor system, and moni-toring system. As a conclusion, the developed line switching control systems and equipments can be used effectively for maritime communication, military communication, fishery communication, etc.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2403-2408
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• 2014

We designate multiple target areas for the advertisement disseminations in order to resolve the problem of advertisement transmission efficiency degradation due to overlapped device-to-device (D2D) transmissions and unnecessary advertisement transmissions. We here propose an efficient advertisement dissemination algorithm based on pre-selected target areas considering user density. In our proposed algorithm, relay nodes are gradually selected according to the locations of the target areas. We mathematically analyze D2D advertisement coverages of our proposed algorithm, and compare the various simulation results of the proposed algorithm with those of the conventional algorithm according to the several simulation scenarios via intensive simulations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6160-6168
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• 2015

Hand hygiene(HH)of the health care personnels(HCPs) was the most effective method to prevent the transmission of healthcare associated infections. This study was conducted to measure and analysis the status of the HH compliance of HCPs. Data were collected by the direct observation methods of the World Health Organizations(WHO) using WHO's HH monitoring tool kits from 25th October to 31th December, 2010. Data were analyzed by descriptive statistics, cross analysis, multiple logistic analysis using the SPSS/PC 21 program. A total of 8,644 opportunities for HH were observed, and the overall HH compliance rate was 94.1%. HH rates of physicians was lowest(83.4%; OR: 0.209, 95%CI:0.174-0.252). HH rates were statistically different by the job titles(p<0.001), WHO's 5 moments(p<0.001). HH rates in registered nurses(p=0.003), and medical technicians(p<0.001) were statistically different by the WHO 5Moments. Jobs specific HH strategies and WHO 5Moments should be developed to increase the HH compliances of the HCPs.