• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2012.06a
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• pp.477-479
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• 2012

최근 선박의 사고가 증가하고 해양 환경오염 문제가 대두되면서 운항 중인 선박을 대상으로 하는 다양한 안전운항 솔루션에 대한 필요성이 요구되고 있다. 안전운항 솔루션은 일반적으로 육상과 선박을 연결하는 광대역 무선 데이터 통신기술, 해상 데이터를 처리할 수 있는 메타데이터 기술, 안전운항을 지원하는 서비스의 요소 기술로 구성된다. 본 논문에서는 광대역 애드혹 통신망을 기반으로 하는 선박의 안전 입출항 지원 서비스의 항목을 정의하고, 이를 구현하기 위한 서버 및 클라이언트 시스템에 대하여 기술한다. 본 연구의 안전 입출항 지원 서비스는 교통정보, 환경정보, 충돌회피지원정보로 구성되며, 선박에 탑재된 클라이언트에서 육상에 설치된 서버 시스템으로 서비스를 요청하고 정보를 제공 받도록 설계하였다. 이렇게 설계된 시스템은 테스트 플랫폼을 통해 서비스의 구현 가능성을 검토하며, 실해역(여수항)에서의 시험을 통해 그 실효성을 검증할 예정이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.425-432
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• 2014

The Enhanced Distributed Channel Access (EDCA) function of IEEE 802.11e standard defines contention window (CW) for different Access Category (AC) limits to support Quality-of-Service (QoS). However, it have been remained the problem that the collision probability of transmission is increasing in congested network. Several different solutions have been proposed but the collision occurs among same priority queue within the same station to compete the channel access. This paper presents an APCA (Advanced Priority Collision Avoidance) algorithm for EDCA that increases the throughput in saturated situation. The proposed algorithm use reserved field's bits of FC(Frame Control) using IEEE 802.11e standard's RTS/CTS (Request to Send / Clear to Send) mechanism to avoid data collision. The simulation results show that the proposed algorithm improves the performance of EDCA in packet loss. Using Jain's fairness index formula, we also prove that the proposed APCA algorithm achieves the better fairness than EDCA method under network congested condition.

• Journal of Navigation and Port Research
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• v.28 no.1
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• pp.9-16
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• 2004

The purpose of this study is to examine the algorithm of ship collision avoidance system and to improve its performance. The study on the algorithm of ship collision avoidance system have been carried out by many researchers. We can divide the study according to the adopted theory into two category such as 'collision risk calculation method' and 'risk area method'. It is not so difficult to find heir merit and demerit in the respective method. This study suggested newly modified model, which can overcome a limit in the two method. The suggested model is based on collision risk calculation method and suggests how to solve the threshold value problem, that is, one of the unsolved issues in collision risk calculation method. To solve that problem this study proposed new system under which the users can select appropriate threshold value according to environments such as traffic situations and weathers conditions. Simulation results of new model is schematized using 'risk area method'to examine the relationships between the two method. In addition, in case of 'collision risk method', when TCPA and DCPA are used to determine collision risk, a problem happens, that is, two ships become too close in their stem area, therefore, partial function of 'risk area method'is adopted to solve the problem in suggested model.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.81-83
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• 2023

자율운항선박은 선원의 항해 조작 없이 선박 스스로 운항하는 선박을 의미한다. 자율운항선박의 운항 시 충돌 및 사고 위험도가 큰 지역은 운항 중 선박을 많이 조우하게 되는 항 내 및 연안 지역이다. 실제로 충돌사고의 85% 이상이 항 내 및 연안 지역에서 발생한다. 따라서 자율운항선의 운항 안전성 확보를 위해 항 내 및 연안 지역에서의 운항 안전성을 검토하는 것은 미래 자율운항선 항 내 운용 체계에서 중요한 역할을 하게 된다. 대양에서는 선박 자체의 운항성능이 중요하지만, 항구 입출항 시에는 타선 및 터미널등과의 상호작용이 자율운항선의 입출항 안전성과 직결된다. 따라서 본 연구에서는 자율운항선이 항구 근처에 접근하여 입출항을 위해 대기하고 있는 경우에 입출항 결정을 내릴 수 있는 결정 알고리즘을 위한 해상혼잡도를 예측하는 알고리즘을 개발하는 과정을 소개한다. 혼잡 예측 알고리즘 개발을 위해 선박의 AIS통항데이터를 분석하여 주요 항로를 구분하고 주요 항로의 이용 빈도 및 운항 시점의 선박 집중도 및 충돌위험 상황을 파라미터로 하여 현재 시점부터 2주후 미래까지의 항로 혼잡도를 예측하고, 정확도를 제시한다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.642-648
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• 2019

Vessels sail according to the COLREG to prevent a collision. However, it is difficult to apply COLREG under special situation as heavy traffic, at this time personal skills of the operator are required. In this case, traffic control is required through the maritime traffic monitoring system. Therefore, maritime traffic management is globally implemented by VTS. In this system, VTS of icer uses the VTS system to assess risks and recommends possible safety operation to vessels with radio systems. This study considers that the risk analysis method with AI (Artificial Intelligence) technology from the operator's aspect. In addition, the research explains the Maritime Traffic Safety Monitoring System, Including AR (Augmented Reality) technology to increase vessel control efficiency. This system is able to predict hazards and risk priorities, and it leads to sequential elimination of dangerous situations. Especially, the hazard situations can be analyzed from operator's perspective of each vessel instead of the VTS officer's aspect, which is more practical than the conventional method. Furthermore, the result of analysis enables to comprehend quantitative hazardous areas and support recommended routes to avoid a collision. As a result, I firmly believe that the system will support to prevent a collision in complex traffic waters. In particular, it could be adopted as a collision prevention system for Maritime Autonomous Surface Ship, which occupies a significant proportion in Maritime 4th industrial revolution.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.297-298
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• 2022

본 연구는 울산항 인근 정박지 내 선박의 운항 패턴을 파악하고, 관련 법규 및 준수 실태를 대조하여 자율운항선박의 실제 운항 시에 부차적인 운항 수칙을 수립하는 데 목적을 두고 있다. 일반적으로 항행하는 선박의 해양사고 중 높은 비중을 차지하는 조우 상황에서의 운항 규칙과 관련된 법률이 정박지 내에도 적용되고 있다. 이러한 관점에서 관련 법규들을 토대로, 실제 정박지에서 항행하는 선박들의 운항 패턴들을 관측하였으며, 대부분 정박지 내에서 출항하는 선박들은 항로의 우측에 근접하여 운항하는 양상을 보이며 우측 항행을 준수하고 있음을 확인하였다. 또한, 정박지 및 항내에서 충돌과 같은 예치기 못한 사고가 발생하는 대표적인 운항 패턴들은 정면 조우 상황, 방파제 내 출항 선박 회피, 우측 항행 등으로 분류되며, 정면 조우 상황과 방파제 출항 선박 회피의 경우에는 관련 법규를 준수하며 항행하는 것을 확인하였으나, 우측 항행 상황에서는 조우 상황에 따라 부득이하게 이행할 수 없는 경우가 발생함을 확인하였다. 본 기초 연구를 통하여 정박지 및 항내에서의 항행하는 선박의 운항 패턴을 자율운항선박에 적용 가능성을 타진하고, 항해 지원이 가능한 운항 수칙을 새로 정립하는 데 활용하고자 한다.

• Journal of Korea Multimedia Society
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• v.3 no.3
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• pp.224-233
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• 2000

An important feature of virtual reality is the facility for the user to move around a virtual environment in a natural and easily controlled manner, Navigation. Navigation involves changing the perspective of the user in the virtual environment (VE). Natural locomotion methods are able to contribute to a sense of presence and reality. This paper focuses on the navigation method in the virtual environment, one of the major interfaces for the interactivity between human and virtual environments in virtual reality circumstances and worlds. It proposes a new navigation method: Intelligent Cruise-Control Navigation (ICCN), which provides a natural and user-centered navigation method in virtual environment and can improve the reality and the presence. Intelligent Cruise-Control Navigation is composed of three major phases: Constant Velocity Navigation, Collision Detection and Avoidance, and Path Adjustment. The ICCN can reduce the user's fatigue and improve the user's presence and reality in the virtual environment. Through the experimental study it has been determined that the ICCN will be a natural, straightforward, and useful interface in VE.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.5
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• pp.462-469
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• 2023

In this study, we propose a method for evaluating the risk of collision between ships to support determination on the risk of collision in a situation in which ships encounter each other and to prevent collision accidents. Because several uncertainties are involved in the navigation of a ship, must be considered when evaluating the risk of collision. We apply the Dempster-Shafer theory to manage this uncertainty and evaluate the collision risk of each target vessel in real time. The distance at the closest point approach (DCPA), time to the closest point approach (TCPA), distance from another vessel, relative bearing, and velocity ratio are used as evaluation factors for ship collision risk. The basic probability assignments (BPAs) calculated by membership functions for each evaluation factor are fused through the combination rule of the Dempster-Shafer theory. As a result of the experiment using automatic identification system (AIS) data collected in situations where ships actually encounter each other, the suitability of evaluation was verified. By evaluating the risk of collision in real time in encounter situations between ships, collision accidents caused by human errora can be prevented. This is expected to be used for vessel traffic service systems and collision avoidance systems for autonomous ships.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.9
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• pp.1038-1048
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• 2019

Recently, various systems have been developed to support ship navigation safety. In order to verify the usefulness of such a system, it is most ideal to try it on a real vessel, but there are many difficulties. As an alternative, usability verification methods applied with modelling and simulation (M&S) techniques are required such as FMSS, which is closest to reality, is very expansive to construct, and there needs the specialized operator. For this reason, this paper proposes a method to verify the navigation safety support system by modeling and simulation techniques based on the Discrete Event System Specification (DEVS) formalism. As a first step, we designed the navigation simulation architecture based on the SES/MB framework, and details on modelling ship core equipment and navigator agents based on the DEVS. Through this, we are able to implement the navigation simulation system for vessels, and evaluate the effectiveness of navigation safety support elements such as collision avoidance, etc. using developed scenarios.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.132-138
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• 2012

VANET(Vehicular Ad-hoc Network), standardization of IEEE 802.11p specification is in process. 802.11 MAC protocol grants all nodes equal opportunity to acquire channel without regard to their bit-rates, making it possible for lower bit-rate nodes to occupy communication channel for a fair amount of time thus keeping the higher bit-rate nodes from acquiring connection channel which downward-equalize the overall network performance. Also with the 802.11p MAC protocol, the probability of collision occurring increases as the number of nodes grow. The proposed algorithm is a new MAC protocol that guarantees nodes with acquired channel a firm priority over other nodes for a fixed amount of time with TXOP concept added to 'packet burst' according to the current transmitting speed. This newly designed algorithm allows the construction of wireless network with enhanced network throughput, decreased probability of collisions as well as providing the means to grant each node a fair chance of acquiring connection according to their channel conditions. The algorithm sets the CW's (Contention Window) width wider than the standard's and modulates the continuous transmitting threshold value depending on channel acquired time, thus improving the overall performance of the network.