• 대한전자공학회논문지TC
• /
• 제45권9호
• /
• pp.8-12
• /
• 2008

본 논문에서는 AMC(Adaptive Modulation and Coding)기법을 적용한 D-STTD(Double-Space Time Transmit Diversity) 통신 시스템을 제안하고, 모의실험을 통해 그 성능을 분석한다. AMC기법은 채널 응답의 정보를 바탕으로 적절한 채널 코딩율과 변조 기법을 선택하여 신호를 전송하는 기법으로 에러율과 전송률의 적절한 조화를 이끌어내어 전체 시스템의 전송률과 전송품질의 향상을 가져온다. D-STTD기법은 기존의 STTD(Space Time Transmit Diversity)기법을 전송률 측면에서 보완한 기법으로 STTD기법에 비해 약 2배의 전송률 향상을 가져온다. 모의실험 결과, SNR(Signal to Noise Ratio)이 좋아질수록 높은 MCS(Modulation and Coding Scheme)레벨을 선택하는 확률이 높아지는 것을 볼 수 있었으며, AMC기법을 적용한 D-STTD 통신 시스템은 AMC기법을 적용하지 않은 D-STTD 통신 시스템에 비해 전 SNR구간에서 고른 전송률 분포를 나타냈다. 또한 AMC기법을 적용한 D-STTD 통신 시스템은 기존 AMC 통신 시스템, 혹은 AMC기법이 적용된 STTD 통신 시스템보다 2배 높은 최대 전송률을 나타내었다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권5호
• /
• pp.2379-2397
• /
• 2017

Content distribution technology, which routes content to the cache servers, is considered as an effective method to reduce the response time of the user requests. However, due to the exponential increases of content traffic, traditional content routing methods suffer from high delay and consequent inefficient delivery. In this paper, a content selection policy is proposed, which combines the histories of cache hit and cache hit rate to collaboratively determine the content popularity. Specifically, the CGM policy promotes the probability of possible superior paths considering the storage cost and transmission cost of content network. Then, the content routing table is updated with the proportion of the distribution on the paths. Extensive simulation results show that our proposed scheme improves the content routing and outperforms existing routing schemes in terms of Internet traffic and access latency.

• International Journal of Internet, Broadcasting and Communication
• /
• 제13권3호
• /
• pp.130-136
• /
• 2021

The purpose of this study was to investigate the effect of the intensity of warm-up exercise on the physiological response and exercise performance during resistance exercise. For this purpose, 8 male college students with at least 1 year of experience in resistance movement were selected. The warm-up condition was set to NON condition (preparatory exercise not performed), 3 set condition, 6 set condition, and 9 set condition, and the intensity was different for each set. After warm-up, 75% 1RM of main exercise was performed, and blood pressure and heart rate were measured immediately after exercise to measure RPP. The number of repetitions and total work for each condition were measured as the number of repetitions and momentum during the main exercise. The measured data were analyzed by repeated measures two-way ANOVA. As a result, although there was no difference in Rate Pressure Product according to the warm-up conditions, the number of repetitions and total amount of exercise showed the highest in the 3-set condition. Therefore, it is thought that the number and intensity of warm-up exercises should be set appropriately during resistance exercise, and warm-up of 3 sets or more during resistance exercise is thought to decrease exercise performance.

• 한국정보기술응용학회:학술대회논문집
• /
• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
• /
• pp.161-164
• /
• 2005

As the power of influence of the Internet grows steadily, attacks against the Internet can cause enormous monetary damages nowadays. A worm can not only replicate itself like a virus but also propagate itself across the Internet. So it infects vulnerable hosts in the Internet and then downgrades the overall performance of the Internet or makes the Internet not to work. To response this, worm detection and prevention technologies are developed. The worm detection technologies are classified into two categories, host based detection and network based detection. Host based detection methods are a method which checks the files that worms make, a method which checks the integrity of the file systems and so on. Network based detection methods are a misuse detection method which compares traffic payloads with worm signatures and anomaly detection methods which check inbound/outbound scan rates, ICMP host/port unreachable message rates, and TCP RST packet rates. However, single detection methods like the aforementioned can't response worms' attacks effectively because worms attack the Internet in the distributed fashion. In this paper, we propose a design of distributed worm detection system to overcome the inefficiency. Existing distributed network intrusion detection systems cooperate with each other only with their own information. Unlike this, in our proposed system, a worm detection system on a network in which worms select targets and a worm detection system on a network in which worms propagate themselves cooperate with each other with the direction-aware information in terms of worm's lifecycle. The direction-aware information includes the moving direction of worms and the service port attacked by worms. In this way, we can not only reduce false positive rate of the system but also prevent worms from propagating themselves across the Internet through dispersing the confirmed worm signature.

• 한국통신학회논문지
• /
• 제40권5호
• /
• pp.791-798
• /
• 2015

이동 중의 차량에서 멀티 서비스를 지원받고자 하는 수요가 증가함에 따라 통신시스템과 차량산업을 융합하는 기술에 대한 관심이 증가하고 있다. 이러한 서비스가 성공적으로 수행되기 위해서는 신뢰성 있는 정보의 전달과 우수한 수신성공률이 보장되어야 한다. 따라서 정확한 채널 값을 추정 할 수 있는 기법이 필요하다. 이 논문은 고속주행 환경에서 동작하는 차량용 통신 규격인 IEEE 802.11p에서 시변 채널추정을 위한 PTAU(Pilot Tone Aided Update) 결정지향 기법을 제안한다. 기존의 기법들은 시간영역에서 오류전파가 발생하므로 높은 서비스의 질을 제공하기 어렵다. 이 논문에서는 이러한 문제점의 보완을 위해 파일럿 부반송파들을 사용하였고, 주파수 대역에서 일정한 순서에 따라 추정한 값들을 업데이트시킴을 제안한다. PTAU기법은 기존의 기법들에 비해 낮은 비트오류율을 가져 고속채널에서의 추적 성능을 향상시킴을 검증하였다.

• 한국정보통신학회논문지
• /
• 제17권7호
• /
• pp.1577-1582
• /
• 2013

본 논문에서는 수조에서 실험을 통해 획득한 데이터를 이용하여 MIMO (Multi-Input Multi-Output) 수중음향통신의 성능을 분석하였다. 이를 위하여 먼저 여러 송수신 위치에서 채널 전달 특성을 측정하였다. 송신신호는 QPSK (Quadrature Phase Shift Keying)로 변조하였으며, 수신신호는 Zero Forcing 등화기 등을 포함하는 검출기를 거쳐 복원되었다. 실험이 이루어진 수조 환경이 물리적으로 폐쇄된 매우 심한 다중 경로 전달 환경이어서 최대 30~40 ms의 지연 현상이 나타났다. 실험 결과 송신 및 수신 센서가 각각 두 개인 $2{\times}2$ MIMO 시스템을 사용하였을 때 채널 특성으로 인해 비트 오차율이 비교적 크게 나타났지만 SISO (Single-Input Single-Output) 시스템에 비해 약 15% 정도 향상된 성능을 갖는 것을 확인하였다.

• 대한인간공학회지
• /
• 제30권1호
• /
• pp.237-250
• /
• 2011

The train transportation has a lot of advantages-energy efficiency is high, it is eco-friendly, safety is better than normal roads and it is possible for people to arrive on time. In these days, the valuation of ride comfort, which is only limited to road transportation, is newly recognized in order to having competitiveness from other transportation. Especially, in the development of the Korean high-speed railroad business, the ride comfort enhancement of train is very important problem to be solved. Currently, there are international standards of ride comfort such as UIC13, ISO2631. In Korea case, although it has own standard like KS R9216, it mainly depends on the physical parameter such as vibration and noise. So recently, in the valuation of ride comfort, the movements of living parameter technique introduction are increasing on the base of Japan and many developed countries of Europe techniques. Presently, the method of train ride comfort is mainly based of vibration, that is, mechanical parameter adding selection of variable acceleration and noise. This paper would like to show biological parameter; heart rate and blood pressure variation. This method is more direct, based on human body response, than mechanical parameter method. In this experiment, the variability of heart rate and blood pressure of passengers according to tilting angle change of Train, the Korean tilting train, we are supposed to know that the extent of tilting on the simulation has influence on variability of heart rate and blood pressure, which are living parameter of heart's blood.

• 한국정보통신학회논문지
• /
• 제24권3호
• /
• pp.441-447
• /
• 2020

전 세계적으로 매년 약 5천만 톤의 전기 및 전자 폐기물이 발생하고 있는 상황에서 사물인터넷 디바이스가 2025년 약 750억 개에 달할 것으로 예상하고 있다. 그러나 사물인터넷 디바이스의 폐기 처리에 필요한 식별 기법에 대한 연구는 미미하다. 본 논문에서는 이러한 문제를 해결하기 위해 사물인터넷 디바이스의 재활용 가능률과 재생 가능률, 각 부품의 재활용률 및 재생률 등의 EoLT(End-of-Life Treatment) 정보를 포함한 식별자를 제안하며, 객체 식별자, 모바일 RFID 및 QR 코드로 구현한다. 구현된 객체 식별자와 모바일 RFID는 통신 네트워크를 통해 원격 서버와 연동하여 사용될 수 있고, 구현된 QR 코드는 스마트폰 앱을 통해 간단히 사용될 수 있다.

• 한국정보시스템학회지:정보시스템연구
• /
• 제5권
• /
• pp.115-147
• /
• 1996

1. Introduction The new computing era started with the various computer technologies and services having been used in communication and automation area since 1980's. We call that era information technology(IT) era. In such era, especially communication plays very important roles in every aspect. So Schoderbek named that era the ege of c2. Therefore, communition became widely used in organizations. Now the majority of organizations have computer-aided communication capabilities that facilitate access to people and information, both within and outside organization. So one objective of this study is to assess the effects of these changes in data communication on decision making. Decision making is the essence of management and is too important to organizational success. This dissertation has three basic objectives: 1)to clarify the concept of data communication, who influences on decision making, and the concept of decision types, managerial and operational, may be affected differently by data communication 2)to investigate whether the effects of data communication upon decision making may be organizational variables. 3)to verify that business and decision types may affect different impact on decision making.2. Hypotheses Four attributes are selected to make hypotheses from the information attributes presented by famous scholars. They are as follows. ①effectiveness ②routinization ③communication easiness ④timeliness Hypotheses are developed according to these attributes, which are chosen from the literature study and theory H1 : Data communication is positively related to the effectiveness of DM H2 : Data communication is positively related to the routinization of DM H3 : Data communication is positively related to the communication easiness of DM H4 : Data communication is positively related to the timeliness of information for DM3. Methodology After pilot study, data are collected from the decision makers in 200 companies located at Seoul and the metropolitan area. A random sample of 174 employees sent back their questionnaires(response rate of 87%). Among them, 151 questionnaires was useful to the analysis of this study(useful rate of 75.5%).4. Conclusion and Discussion Among four proposed hypotheses, all hypotheses are fully supported. They are as follows. 1)effectiveness 2)routinization 3)communication easiness 4)timeliness. So, first objective of this study is proved. Namely, to clarify that the effects of data communication upon DM is fully supported. But they are different from the decision types. Second one is not apparently verfied. i.e. the effect of data communication on the decision variables is not moderated by organizational variables. Third is inspected. The effects of data communication differs from the industry and decision types evidently. This study has many limitations to generalize the statistical results. Since the definition of data communication has broad meanings in reality. So allare not contained in this research. Another restrict in this study is like this. Decision types are usually divided into three types-operational, managerial, strategic DM. But in this study, strategic DM is left out.

• 한국정보통신학회논문지
• /
• 제18권8호
• /
• pp.1818-1826
• /
• 2014

해면 상태의 변화는 수중 음향 통신 수신 신호에 전방 산란 및 도플러 확산을 야기하여 수신 신호의 진폭, 주파수 및 위상은 시간적으로 변화한다. 따라서 통신채널의 일관성 대역폭과 페이딩 변화에 의해 고속 동기식 디지털 통신 성능은 장애를 받게 된다. 본 논문에서는 2가지의 해면 상태에서 QPSK의 성능을 평가하였다. 해면 산란이 성능에 미치는 영향은 LFM 신호를 이용하여 구한 채널의 임펄스 응답과 시간 일관성을 기반으로 해석하였다. 잔잔한 해면보다 거친 해면 상태의 임펄스 응답은 불안정하고 일관성 시간은 짧다. 이러한 결과와 수신 신호의 포락선, 진폭 및 위상과의 관계를 해석하여 QPSK의 비트 오류율이 해면 상태와 직접적으로 관계되는 것을 확인하였다.