• Journal of Communications and Networks
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• 제13권4호
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• pp.400-407
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• 2011

Various air indexing and data scheduling schemes for wireless broadcast of spatial data have been developed for energy efficient query processing. The existing schemes are not effective when the clients' data access patterns are skewed to some items. It is because the schemes are based on flat broadcast that does not take the popularity of the data items into consideration. In this paper, thus, we propose a data scheduling scheme letting the popular items appear more frequently on the channel, and grid-based distributed index for non-flat broadcast (GDIN) for window query processing. The proposed GDIN allows quick and energy efficient processing of window query, matching the clients' linear channel access pattern and letting the clients access only the queried data items. The simulation results show that the proposed GDIN significantly outperforms the existing schemes in terms of access time, tuning time, and energy efficiency.

• 한국통신학회논문지
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• 제38A권1호
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• pp.68-78
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• 2013

본 논문에서는 다양한 무선 접속 기술(Radio Access Technology : RAT)들이 공존하는 클라우드 기지국 시스템에서의 효율적인 무선 접속 방법으로 무선인지기술(Cognitive radio)을 활용한 이른 스펙트럼 감지(Early Spectrum Sensing : ESS) 기법을 제안한다. 다중 모드 단말은 무선 접속 시도에 앞서 다중 무선 접속 시스템의 전체 주파수 대역을 대상으로 스펙트럼 감지를 수행하여 그 결과 스펙트럼 활용도가 가장 낮은, 즉 가용 스펙트럼이 가장 많을 것으로 예상되는 시스템을 선택하여 무선 접속을 시도함으로써 시스템 접속 성공 확률을 높일 수 있다. 제안 기법의 성능 분석을 위해 컴퓨터 시뮬레이션을 수행 했으며 그 과정에서 최대한 다양한 무선 접속 시스템이 혼재하는 상황을 고려하고자 했다. 우선, 서킷과 패킷 시스템으로 구별한 후, 다시 패킷 시스템을 반송파 결합(Carrier Aggregation : CA) 가능 여부에 따라 다시 구별했으며, 단말기의 경우, 서킷 전용, 패킷 전용, 다중 모드로 구별함과 동시에 CA 능력에 따라서 역시 구별하였다. 또한, 패킷 트래픽의 경우, 실시간 트래픽과 3단계의 패킷 지연 허용 정도를 갖는 비실시간 트래픽으로 구분하였다. 이러한 다양한 무선 접속 환경이 고려된 클라우드 기지국 시스템에서 호 발생에서 호의 서비스 품질(Quality of Service : QoS)이 고려된 자원 할당까지의 일련의 과정을 시뮬레이션에 반영하여 시스템 접속 실패 확률, 평균 시스템 접속 시간, 시스템 균형 인수, 패킷 손실 확률 측면에서 제안 방식의 성능을 분석하였다.

• 한국컴퓨터정보학회논문지
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• 제11권6호
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• pp.193-200
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• 2006

RFID의 적용 범위는 점차 그 영역을 확대되고 있으나, 보안과 더불어 개인영역 침해에 대한 연구는 아직은 미흡한 실정이다. 본 논문에서는 기존 RFID 보안 프로토콜을 분석하고 정보보호와 프로토콜의 경량화 문제를 해결하기 위하여 접근시간간격과 경량화 RSA 알고리즘을 이용한 새로운 프로토콜을 제안한다. 제안된 프로토콜을 통해 양방향 정보 송수신에 대한 정보보호 문제를 해결하고 이를 구현하고자 한다.

• 대한임베디드공학회논문지
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• 제9권1호
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• pp.25-32
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• 2014

In this paper, we proposed a partial-way set associative cache memory with an effective memory access time and low energy consumption. In the proposed set-associative cache memory, it is allowed to access only a 2-ways among 4-way at a time. Choosing ways to be accessed is made dynamically via the least significant two bits of the tag. The chosen 2 ways are sequentially accessed by the way selection bits that indicate the most recently referred way. Therefore, each entry in the way has an additional bit, that is, the way selection bit. In addition, instead of the 4-way LRU or FIFO algorithm, we can utilize a simple 2-way replacement policy. Simulation results show that the energy*delay product can be reduced by about 78%, 14%, 39%, and 15% compared with a 4-way set associative cache, a sequential-way cache, a way-tracking cache, and a way cache respectively.

• Journal of Computing Science and Engineering
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• 제8권2호
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• pp.78-86
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• 2014

Aiming to solve the problems of high memory access and big storage space and long matching time in the regular expression matching of extended finite automaton (XFA), a new regular expression matching algorithm based on high-efficient finite automaton is presented in this paper. The basic idea of the new algorithm is that some extra judging instruments are added at the starting state in order to reduce any unnecessary transition paths as well as to eliminate any unnecessary state transitions. Consequently, the problems of high memory access consumption and big storage space and long matching time during the regular expression matching process of XFA can be efficiently improved. The simulation results convey that our proposed scheme can lower approximately 40% memory access, save about 45% storage space consumption, and reduce about 12% matching time during the same regular expression matching process compared with XFA, but without degrading the matching quality.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.121-124
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• 2003

Passive optical networks (PONs) will be the pervasive choice in the design of next-generation access networks. One possible solution to implementing Passive optical access network is to rely on wavelength-division multiplexing (WDM). In this paper, we solve the problem of providing real-time service to both hard and soft real-time messages in conjunction with a conventional vest-effort service in WDM. we propose an adaptive scheduling algorithm to schedule and manage the message transmissions in the optical access network. Proposed algorithm is MLF-MQF. Also, we suggest dynamic bandwidth algorithm(DBA) in Loop-back WDM-PON (LPB-PON).our mechanism based on bandwidth reservation protocol.

• Educational Technology International
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• 제14권2호
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• pp.215-228
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• 2013

In engineering education practical experiments is very important for each student, but due to the limitation of time and available resources such as laboratory equipment, space and instructors enough hands-on real experiments could not be provided to all students enrolled in the program throughout the academic year. In this sense web-based remote experiments through internet become a solution for engineering education and an emerging new paradigm for students and teachers. This paper presents the development of the web-based remote vibration experiment system for mechatronics education. Students can access this experimental equipment through an internet and conduct vibration experiment remotely without any restriction on time and place. IP address for data communication and web-service are assigned in local computer and then students receive experimental results and the captured pictures using network. The developed system provides real-time feedback of the tested results. Ubiquitous access to the system gained popularity from students.

• Journal of Computing Science and Engineering
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• 제9권1호
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• pp.1-8
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• 2015

Accessing and searching in a sequence of numbers are fundamental operations in computing that are encountered in a wide range of applications. One of the applications of the problem is cryptanalytic time-memory tradeoff which is aimed at a one-way function. A rainbow table, which is a common method for the time-memory tradeoff, contains elements from an input domain of a hash function that are normally sorted integers. In this paper, we present a practical indexing method for a monotonically increasing static sequence of numbers where the access and search queries can be addressed efficiently in terms of both time and space complexity. For a sequence of n numbers from a universe $U=\{0,{\ldots},m-1\}$, our data structure requires n lg(m/n) + O(n) bits with constant average running time for both access and search queries. We also give an analysis of the time and space complexities of the data structure, supported by experiments with rainbow tables.

• 한국군사과학기술학회지
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• 제21권3호
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• pp.361-369
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• 2018

This paper proposes a design of asymmetric time division multiple access method for tactical radio communication. Typical tactical radio communication has a limited execution of transmission, because uplink message requires more extended response time than downlink message. In order to solve this problem, this paper analyzes operational environment of Korean tactical radio communication and proposes an asymmetric TDMA based on it for performance of tactical communication. The simulation model is used to investigate constraints of real experiments for proving effectiveness of the proposed approach. Simulations results show that the proposed scheme outperforms the conventional scheme in terms of throughput, response time, and delay.

• 한국컴퓨터정보학회논문지
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• 제24권11호
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• pp.51-59
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• 2019

웹에서 정보 접근에 대한 폭발적인 주문으로 웹 사용자의 다음 접근 페이지를 예측하는 필요성이 대두되었다. 웹 접근 예측을 위해 마코브(markov) 모델, 딥 신경망, 벡터 머신, 퍼지 추론 모델 등 많은 모델이 제안되었다. 신경망 모델에 기반한 딥러닝 기법에서 대규모 웹 사용 데이터에 대한 학습 시간이 엄청 길어진다. 이 문제를 해결하기 위하여 딥 신경망 모델에서는 학습을 여러 컴퓨터에 동시에, 즉 병렬로 학습시킨다. 본 논문에서는 먼저 스파크 클러스터에서 다층 Perceptron 모델을 학습 시킬 때 중요한 데이터 분할, shuffling, 압축, locality와 관련된 기본 파라미터들이 얼마만큼 영향을 미치는지 살펴보았다. 그 다음 웹 접근 예측을 위해 다층 Perceptron 모델을 학습 시킬 때 성능을 높이기 위하여 이들 스파크 파라미터들을 튜닝 하였다. 실험을 통하여 논문에서 제안한 스파크 파라미터 튜닝을 통한 웹 접근 예측 모델이 파라미터 튜닝을 하지 않았을 경우와 비교하여 웹 접근 예측에 대한 정확성과 성능 향상의 효과를 보였다.