• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.17-19
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• 2015

AIS는 데이터 송수신을 위하여 2개의 채널을 사용하고 있으며, 채널 당 2,250개의 시간 슬롯으로 분할하여 사용하는 시분할 다중화 방식을 적용하고 있다. 특히 AIS에서 주로 사용하고 있는 SOTDMA 프로토콜은 데이터를 전송하기 위한 시간 슬롯을 예약하고 예약된 슬롯 정보를 공유함으로써 슬롯 간섭을 피하고 있기 때문에 슬롯의 사용 상태는 매우 중요하다. 여기에서는 해발고가 높은 우리나라 주요 AIS 기지국의 슬롯 점유율과 슬롯 점유율에 영향을 미치는 수신 메시지 비율 및 통신 거리 분포 등에 대하여 분석하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.195-196
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• 2016

In the maritime mobile radiocommunication service, AIS(Automatic Identification System) devices are most widely using for the exchange of ship's navigational information. The AIS time slot usage increases due to increasing number of ships installed with AIS, and thus the reception rate of AIS data decrease. In order to mitigate this problem, international organizations recommend a sectorised receiving technique using directional antenna. This paper analyzed the sectorised receiving effectiveness of AIS data using Yaga antenna.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.10a
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• pp.111-113
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• 2014

AIS의 항해상태 정보는 사용자가 수동으로 변경 입력해야 하는 정보이며, 항해상태 정보에 따라 AIS의 동적정보 전송주기는 자동으로 변하게 된다. 정박 또는 묘박선의 경우 AIS 항해상태 정보를 정확하게 입력하지 않으면 동적정보가 불필요하게 자주 발신되어 AIS의 슬롯 점유율을 높이는 결과를 초래한다. 본 논문에서는 정박선의 AIS 데이터를 수신하여 비정상적으로 동적정보가 전송되는 경우를 분석하였으며, 이를 보완하기 위한 방안으로 AIS 동적정보 전송 주기의 변경을 제안하였다.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.3
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• pp.256-261
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• 2013

The AIS(Automatic Identification System) has been widely used for ship safety at sea over the last 10 years. The AIS traffic load at VDL(VHF Data Link) has been continuously increased. As the traffic load at VDL increases, the quality of AIS service may be deteriorated. In the previous research, the AIS traffic has been analyzed in the major ports of Korea, and its problem due to traffic overload has been suggested. However, no solutions has been given so far. In this paper, the method of autimatically controlling the VDL traffic at AIS base station is represented.

• Journal of the Korea Society of Computer and Information
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• v.29 no.1
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• pp.1-9
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• 2024

This paper proposes an integration of the ED-H scheduling algorithm, known for optimal real-time scheduling, with the LoRaEnergySim simulator. This integration facilitates the simulation of interactions between real-time scheduling algorithms for tasks with time constraints in Class-A LoRaWAN Class-A devices using a super-capacitor-based energy harvesting system. The time and energy characteristics of LoRaWAN status and state transitions are extracted in a log format, and the task model is structured to suit the time-slot-based ED-H scheduling algorithm. The algorithm is extended to perform tasks while satisfying time constraints based on CPU executions. To evaluate the proposed approach, the ED-H scheduling algorithm is executed on a set of tasks with varying time and energy characteristics and CPU occupancy rates ranging from 10% to 90%, under the same conditions as the LoRaEnergySim simulation results for packet transmission and reception. The experimental results confirmed the applicability of co-simulation by demonstrating that tasks are prioritized based on urgency without depleting the supercapacitor's energy to satisfy time constraints, depending on the scheduling algorithm.

• Information Systems Review
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• v.16 no.3
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• pp.49-68
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• 2014

These days, consumers have increasingly preferred to digital real-time streamlining and downloading to listen to music because this is convenient and affordable for the consumers. Accordingly, sales of music in compact disk formats have steadily declined. In this regards, online digital music has become a new communication channel to listen musics, where digital files can be delivered over various online networks to people's computing devices. The majority of online digital music distributors has Music Recommender Systems for sales of digital music on their websites. Music Recommender Systems are parts of information filtering systems that provide the ratings or preferences that users give to music. Korean online digital music distributors have Music Recommender Systems. But those online music distributors didn't provide any rules or clear procedures that recommend music. Therefore, we raise important questions as follows: "Is Music Recommender Systems Fair?", "What is the impact of Music Recommender Systems on online music rankings and sales?" While previous studies have focused on usefulness of Music Recommender Systems, this study investigates not only fairness of Current Music Recommender Systems but also Relationship between Music Recommender Systems and online Music Charts. This study examines these issues based on Bandwagon effect, ranking effect, Slot effect theories. For our empirical analysis, we selected the most famous five online digital music distributors in terms of market shares. We found that all recommended music is exposed to the top of 'daily music charts' in online digital music distributors' websites. We collected music ranking data and recommended music data from 'daily music chart' during a one month. The result shows that online music recommender systems are not fair, since they mainly recommend particular music that supported by a specific music production company. In addition, the recommended music are always exposed to the top of music ranking charts. We also find that recommended music usually appear at the top 20 ranking charts within one or two days. Also, the most music in the top 50 or 100 ranks are the recommended music. Moreover, recommended music usually remain the ranking charts more than one month while non-recommended music often disappear at the ranking charts within two week. Our study provides an important implication to online music industry. Because music recommender systems and music ranking charts are closely related, music distributors may improperly use their recommender systems to boost the sales of music that related to their own companies. Therefore, online digital music distributor must clearly announce the rules and procedures about music recommender systems for the better music industry.