• Journal of Korea Multimedia Society
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• v.10 no.3
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• pp.401-410
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• 2007

Multimedia streams transmitted through the Internet have a strict playback delay time. Multimedia data arriving aster the playback time cannot be played in the receiver and are discarded. Thus, this paper proposed a protocol, in which the multimedia stream server determines whether data can be played in the receiver before sending the data. The proposed model has a PSCTP sub-layer on top of existing PR-SCTP and decides whether to send data messages, which have come from the multimedia applicationserver, and which PR-SCTP stream the data will be sent to. In addition, the proposed model uses the differentiated retransmission function of PR-SCTP. We evaluated the performance of SCTP, PR-SCTP and PSCTP using NS2 simulator. According to the results of the evaluation, the PSCTP protocol decreased the volume of transmission and increased the video decodable ratio compared to other protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.6
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• pp.545-553
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• 1987

An approximation algorithm has been obtained to analyze the network of single server tandem queues with a finite length. In the queueing network with a finite queue length, the blocking which is mutually dependent, occure due to the limitation of the queue length. Thus, it is difficults to analyze such a queueing network. In this paper each queue has been regarded as the independent M/M/1/K system to analyze the queueing network with the blocking, which is based on the assumption that an arrival rate to the present station is increased by the blocking of the following stations. The performance measures, such as state probability, average queue length and tha waiting time, can be easily obtained using the proposed algorithm. In order to justify this approximation algorithm, comparison of the results of this algorithm with those of state transition simultaneous equations has been made an verified with computer simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.2
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• pp.159-164
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• 2005

When an optical pulse propagates through the atmospheric channel, the atmospheric turbulence attenuates and spreads this pulse. This attenuation and broadening of pulse are occurred by the fluctuation in the arrival time of pulse at the optical receiver. This pulse broadening induces the intersymbol interference (ISI) between the adjacent pulses. finally, the adjacent pulses are overlapped and the bit rate and the repeaterless transmission length are limited by the ISI. In digital communication system, therefore, the pulse broadening is more important factor than the attenuation. In this paper, thus, we find the ISI in the atmospheric turbulence as the function of the structure constant for the refractive index fluctuation that presents the strength of turbulence using the temporal momentum function and present it by numerical analysis.

• Journal of Korea Society of Industrial Information Systems
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• v.6 no.1
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• pp.1-6
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• 2001

This paper proposes a method to reduce the timing gap which causes a type of attack to a network-based intrusion detection system. For this, an intrusion defection system is used in order to measure the round trip tin to the destination system, and the measured round trip time is used for estimation of packet's real arrival time to destination. Socket programings are used on the LAN environments to evaluate the performance of the proposed method. The test results show that an estimation method which uses the latest round trip time has the best performance, and the timing gap can be significantly reduced with small overheads.

• Fire Science and Engineering
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• v.22 no.5
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• pp.137-147
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• 2008

This study has investigated fire safety rules related with traditional temples and main fire causes and cases to traditional temples among traditional wooden buildings so has analyzed fire vulnerability, and through a field probe of three traditional temples in Eunpyeonggu Seoul which have cultural properties, has analyzed geographical conditions, going out path spot reaching time required of a fire brigade, fire protection system, fire prevention administration and security system, factors of fire vulnerability, and has presented about fire safety plans of traditional temples.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.11
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• pp.3104-3109
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• 2009

The technology of direction finding is very important to find the direction of emitters for ELINT(electronic intelligence) system. The principle of TDOA(time difference of arrival) is to receive an emitter signal with two antennas, measure the time difference between two antennas, and converse the time difference to direction difference. This technology can be used in broadband frequency system and make the system very simple because a phase-discriminator and a voltage comparator are not needed. For fine DF accuracy, high time resolution receiver and long basis line antennas are needed. The DF accuracy of noise added signals is simulated with different time

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.1
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• pp.71-80
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• 2011

This paper presents a technique of contstructing and processing the metadata information, which is for UML class authorization tool. Construction of the information authorization tool defines Classes and Relationship based on the elements of the consisting of UML class diagram. Definition of the information class is a visibility of Class, a name of Class, an attribution of Class and an operation of Class. Definition of the relationship with information is a name of Relationship, a type of Relationship, a FromClass and a ToClass. In this paper, for a class authorization tool, it suggests a technique to save and read information from information Storage based on the constructed information.

• Fire Science and Engineering
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• v.19 no.3 s.59
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• pp.37-43
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• 2005

When a fire breaks out in a high-rise building, the firefighters must swiftly arrive at fire area with his equipments ready and use the emergency elevator for a more effective operation. In spite of the legal regulations about the emergency elevator, the ones currently installed show various problems and require improvements related to the fire fighting. This research work in to review the regulations on emergency elevator in Korea and other nations, and to conduct a questionnaire survey on the operation of emergency elevators to the fire officer, and finally to provide new standard and operation methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.303-311
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• 2011

In this paper, we propose the adaptive multibeamforming algorithm to remove the same subcarrier interference and multipath signals in the MIMO(Multi-Input Multi-Out)-OFDMA (Orthogonal Frequency Division Multiplexing Access)system allocated the same subcarrier partially in order to improve spectrum efficiency. In addition to removing the interference, we can get diversity gain and combat the detriment of the performance according to time delay by the proposed approach. BER performance improvement and combating the delay spread detrimental effects of the proposed approach is investigated through computer simulation by applying it to MIMO-OFDMA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.12A
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• pp.1320-1328
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• 2007

In recent year, the popularity of WLAN has generated much interests on improvement and performance analysis of the IEEE 802.11 protocol. In this paper, we analyze two medium access methods of the IEEE 802.11 MAC protocol by investigating the MAC layer packet service times when arrival packet sizes have a general probability distribution. We use the M/G/1/K queueing model to analyze the throughput and the delay performance of IEEE 802.11 MAC protocol in a wireless LAN. We compare the performances of Basic access method and RTS/CTS access method. We take some numerical examples for the system throughput and the queue dynamics including the mean packet delay and packet blocking probability.