• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.2014-2026
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• 1997

In this paper, the performances of wireless asynchronous transfer mode (ATM) cell transmission in mobile work are analyzed. We adopt 16Star QAM as amodulation technique in wireless channel and considered Reed-Solomon, convolutional, and concatenated coding to improve the error rate performances, and also proposed the Partial Concatenated Coding (PCC) technique as UEP(unequal error protection) code for efficient transmission of ATM cell in the air interface. We consider Doppler's effect, Rician fading, and diversity technique of maximal-ratio combining (MRC) for mobile channel model. For performance measure, we analyze bit error rate, ATM cell loss probability, ATM cell error probability, and network performances of ATM cell transmission delay and throughput. The numerical results show that the adoption of PCC is a prospective way for the evolution of future wireless ATM network on mobile environment.

• Annual Conference on Human and Language Technology
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• 2018.10a
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• pp.8-12
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• 2018

구문 분석이란 문장을 단어, 어절, 구 등의 구성 성분으로 분해하고 각각의 구조적 정보를 분석하여 문장의 구조를 알아내는 작업을 말한다. 최근 의존 구문 분석은 심층 신경망을 이용하는 방법이 활발히 연구되고 있다. 특히 포인터 네트워크를 사용하는 방법은 다른 심층 신경망보다 높은 성능을 보이고 있다. 그러나 포인터 네트워크의 사용만으로 의존 관계와 의존 관계명을 예측하는 것은 한계가 존재한다. 본 논문에서는 최근 사용하는 단어 표상 방법 별로 비교 실험을 진행하고 의존 구문 분석에서 GloVe의 성능이 가장 좋음을 보인다. 또한 언어 모델을 통한 단어 표상 방법인 ELMo와 멀티헤드 어텐션을 사용하여 포인터 네트워크만을 사용 했을 때보다 높은 성능(UAS 92.85%, LAS 90.65%)을 보였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.1
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• pp.60-66
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• 2009

A service network in the future ubiquitous environment can consist of a variety of elements, which include different protocols of the network transport. Interwoking different transport protocols can alleviate such problems occurred in accessing network as poverty of facilities, faults, and contention in a path of particular protocol communication. This paper schemes to improve performance of the network constituted of different protocols for the network transport. Interposing an interwork element, like SDR (Software Defined Radio), in the network can raise availability of transport paths, and then improve transport performance of the overall network Simulation analysis justifies such a scheme and this paper presents simulation results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.483-488
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• 2012

With the fast growing data traffic, the performance of the convergent overlay network environment under the cognitive networking environment is crucial for the implementation of the efficient network structure. In order to achieve high capacity and reliable link quality in wireless communication of the overlay convergent networks with the cognitive networking based on the advanced capability of the mobile terminal, a Distributed Wireless Communication System (DWCS) can provide the capability of ambient-aware dual cell system's operation. This paper has considered virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. One is the Active Virtual Cell which exists for user's actual data traffic and the other is the Candidate Virtual Cell which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. The considered system constructs DVC by using cognitive ability of finding useful virtual signals. Also, for multi-user high-rate data transmission, the DWCS system exploits Space-Time Trellis Codes. The effects of changing environments on the system performance has been investigated thereafter.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.7
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• pp.572-580
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• 2013

IEEE 802.15.4e is a prospective standard for low latency control application in industries. This paper proposes a framework to evaluate the closed loop IEEE 802.15.4e based WNCS performance. The framework consists of two models: closed loop control system model and network model. The network model focuses on the PHY parameters of wireless link and takes the channel parameters into consideration. The PHY model combining with MAC model gives the control system model the probability of packet loss in a super-frame. In addition, redundancy mechanism is considered in IEEE 802.15.4e to reduce to data frame loss probability. The simulation is implemented in Matlab, PHY model takes the channel parameters from empirical results. Hence our evaluation gives insight into behavior of WNCS in different environments and it provides us a tool to design wireless network to achieve a good performance for control system.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.6
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• pp.1061-1068
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• 2019

Cooperative networks transmit signals form the source node to the destination node via several relay node where the combining and demodulation of relay aided signals provide the benefit of performance enhancement and data rate increment. In general, a repetitive manner transmission scheme in which the received signal from the source node is amplified/re-generated and forward to the destination node is widely used. In this paper, we analyzed the performance of cooperative networks using the mixed transmission scheme. The conventional modulation scheme is used in the source-relay links, and space-time code is applied in the relay-destination links. To reduce the complexity of the overall system, we adopt differential modulation which bypasses channel state information. We analyze bit error rate (BER) of the proposed system by considering the number of relay nodes, and the performances depending on the strength of transmission signal in the source-relays and rely-destination links are compared. In addition, we also discuss the system performance with the signal strength and the number of relay nodes simultaneously.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.1
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• pp.121-127
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• 2017

In the land mobile satellite (LMS) communication, a hybrid satellite-terrestrial relay networks (HSTRNs) using a maximal ratio combining (MRC) scheme are widely used to enhance the quality of signal from a satellite. In this paper, we derive equations for the TCP throughput and the spectral efficiency in the HSTRN and analyze results of the performance evaluation for TCP in various environments. In the simulation results, it is shown that increasing the number of terrestrial relays can enhance the TCP throughput and spectral efficiency thanks to the MRC scheme. However, the usage of the static number of terrestrial relays considering no channel states would cause the overhead. Furthermore, it has a limitation to enhance the network performance by only MRC scheme in HSTRN because the TCP performance is sensitive to the packet los rate. Therefore, we discuss the possible solutions that can additionally enhance the network performance and reduce the overhead.

• Digital Contents
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• no.8 s.51
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• pp.62-64
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• 1997

네트워크 관리자들은 흔히 네트워크 관리 시스템(NMS)에 모든 것들을 의지해 버리는 특성을 지니고 있다. 장애분석과 성능분석, 보안성 제공 등을 간단히 해결해주기 때문이다. 하지만 이것은 위험천만한 일이다. 그것은 현재 대부분의 NMS가 트래픽 분석 방법론을 제시해 주지 않을 뿐더러 분석이나 해결책 보다는 자료제공의 성격을 많이 띠고 있기 때문이다. 따라서 현재의 NMS로는 네트워크를 총체적으로 관리하기에 부족한 점이 없지 않다. 기존 NMS의 단점을 보완하고 있는 트래픽 분석 시스템을 들여다 보자.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2004.06a
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• pp.3-7
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• 2004

본 연구에서는 학습기능을 갖는 결정론적 볼츠만 머신에 비단조 뉴런을 이용하여 학습 성능을 수치 시뮬레이션을 통하여 분석한다. 먼저 네트워크의 은닉층에 비단조 및 단조뉴런을 이용한 경우에 대하여 각각 활성화 함수로 시그모이드 함수와 end-cut-off 타입의 비단조함수를 사용한 경우에 대하여 성능을 비교한다. 또한, VHDL을 이용해 설계한 DBM 네트워크에 시그모이드 함수와 end-cut-off 타입의 비단조함수를 사용한 경우에 대하여 시뮬레이션을 통해 수치 시뮬레이션과 성능이 같은지 비교하고 그 유용성을 입증한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.625-628
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• 2008

네트워크 서비스를 제공함에 있어서 사용자 인증, 접근 권한 및 요금 처리는 필수적인 기능이다. 이러한 기능을 제공하기 위해 AAA 기술이 정의되었다. AAA의 성능은 네트워크 서비스 전체의 성능에 큰 영향을 줄 수 있다. 현재 AAA 성능에 관련된 이슈와 그 해결책은 알려져 있으나, 이를 통한 성능 향상의 정도는 분석되지 않았다. 본 논문은 AAA 이슈에 대한 분석과 해결책을 설명하고 시뮬레이션을 통해 각 이슈에 대한 성능 향상의 정도를 가시적으로 보여주고 있다. 시뮬레이션 결과에 따르면 AAA의 해결책을 적용한 경우 평균 33%의 성능 향상을 기대할 수 있다.