• Journal of Advanced Navigation Technology
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• v.17 no.6
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• pp.693-699
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• 2013

In this paper, ${\pi}/4$-DQPSK modem according to ITU-R M.1842-1 recommendation Annex1 is investigated and simulated. At first, standardization and technical trend of VHF maritime mobile communication are introduced. The ${\pi}/4$-DQPSK modem defined in the Annex1 should support 28.8Kbps bit transmission rate within 25KHz frequency bandwidth. We describe the system model and simulation process of ${\pi}/4$-DQPSK modem transmitter and receiver design with RRC(Root Raised Cosine) transmitter and receiver filter. Then we suggest various graphical simulation results(time domain signals, constellation, power spectral density according to roll-off factor, eye diagram), and show simulated BER performance of the modem. From the simulation results, it is shown that roll-off factor of RRC filter affects to BER performance according to SNR and the designed simulation model meets the spectrum mask requirement suggested in ITU-R M.1842-1 recommendation.

• International Journal of Computer Science & Network Security
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• v.21 no.6
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• pp.258-268
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• 2021

Online learning systems are becoming an effective educational medium for many universities. The accessibility of online learning system in universities means that every student, including the visually impaired, is able use all the site's services. This research focuses on investigating the accessibility of online learning systems for visually impaired users. The paper purpose is to understand the perception of visually impaired undergraduate students towards Blackboard's accessibility and to make recommendations for a new Blackboard design with accessible features that support their needs. Impact of a new Blackboard design with accessible features on visually impaired students, using Taif University students as a case study is evaluated in this paper, as it is similar to most learning systems used by Saudi universities. A study on Taif University's utilization of Blackboard was conducted using mixed method approaches (an automatic tool and a user study). In the first phase, Taif's use of Blackboard was evaluated by the web accessibility tool called AChecker. In the second phase, we conducted a user study to verify previously discovered accessibility challenges to fully assess them according to the accessibility and usability guidelines. In this study, the accessibility of Taif University's Blackboard was evaluated by thirteen visually impaired undergraduate students. The results of the study show that Blackboard has accessibility issues, which are confusing navigation, incompatibility with assistive technologies, untitled pages or parts, unclear identification for visual elements, and inaccessible PDF files. This paper also introduces a set of recommendations that aim to improve the accessibility of Blackboard and other educational websites developed for this population. It also highlights the serious need for universities to enhance web accessibility for online learning systems for students with disabilities.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.317-318
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• 2022

In accordance with global decarbonization, optimization and productivity improvement using digital twin are being sought, and software development for optimizing ship and marine energy operation is accelerating by selecting digital twin as a future core technology. In order to reduce the operating cost of ships and strengthen the competitiveness of the shipbuilding industry due to the international strengthening of regulations on carbon emissions, it is necessary to predict the carbon emission of ships in advance and provide a carbon reduction operation solution. A plan was carried out for the development of open digital platform technology and the establishment of an environment to support the securing of carbon transparency of the ship and offshore system.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.456-465
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• 2021

For predictive aviation safety management, the establishment of safety performance indicators to measure and manage the safety performance of service providers must be preceded. In particular, leading indicators are significant in that they play an important role in identifying and managing the causes of accident/incident in advance. However, the current safety performance indicators of the domestic aviation industry have limitations in that they focus on lagging indicators based on events that have already occurred. Therefore, the purpose of this study is to construct Korean leading indicators for preventive safety management. In addition, we verify the validity and importance of the indicators based on review of the experts and AHP analysis. This study is meaningful in that it can support the proactive safety management of the domestic aviation industry through the development of leading safety indicators, which have been relatively lacking in research.

• Journal of Advanced Navigation Technology
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• v.28 no.1
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• pp.109-115
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• 2024

The Concept of Operations (ConOps) document issued by the Korean Government (K-UAM ConOps) for urban air mobility (UAM) services takes into account not only aviation voice communication but also the use of 4G and 5G mobile communication to support the initial phase of UAM services. This paper studies a methodology to establish communication performance requirements for UAM traffic management and presents the analyzed results for communication performance requirements. To accomplish this, the operational scenarios of UAM developmental stages outlined in the K-UAM ConOps and FAA ConOps are scrutinized, and the diverse messages that must be communicated among various stakeholders for effective UAM operations are identified. A draft of communication performance requirements is also calculated by considering packet sizes, transmission frequencies, acceptable latencies, and availability. The outcomes of this study are expected to stand as a pioneering effort in defining communication requirements for UAM services, providing a crucial foundation for future initiatives such as the design of dedicated communication networks for UAM and the determination of required frequency bandwidth.

• Journal of Advanced Navigation Technology
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• v.28 no.4
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• pp.393-399
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• 2024

The digital map computer for advanced air vehicles (AAV) must be high-performance, lightweight, portable, and modular. It should receive data on terrain, weather, and obstacles from external modules to display digital maps accurately. This necessitates robust communication capabilities with external devices via an Ethernet interface and the ability to output digital map visuals clearly through an high-defintion multimedia Interface (HDMI) or digital visual interface (DVI) interface. This paper presents the design of both hardware and software architecture that fulfills these critical requirements for an AAV digital map system. Additionally, it establishes the minimum specifications needed and verifies the suitability of the designed digital map computer through rigorous performance measurements and testing. By ensuring these standards, the digital map computer can reliably support the complex navigational needs of AAV, enhancing operational efficiency and safety.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.4
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• pp.84-92
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• 2009

In this paper, using the received signal strength of radio beacon such as Wi-Fi, Bluetooth, CDMA and GPS signal from the satellite, we propose the system of positioning which considered indoor and outdoor based on the Place Lab. Conventional Place Lab utilize the various positioning parameters to estimate the indoor location. However, this conventional system has limitations with respect to the range and efficiency of usage. Therefore, we defined the converged model of multisensor data and re-organized the Place Lab to overcome the limitation of a conventional system. Proposed system uses the radio beacon signal and GPS signal together to estimate the location. Furthermore, it provides the seamless PNS service with many mobile devices because this system realized by the OSGi bundle. This proposed system has evaluated the performance with SAMSUNG T*OMNIA SCH-M490 smart phone and the result shows the system is able to support the PNS service.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1195-1202
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• 2016

Recently, a lot of studies that applying the big data technology to various fields, are progressing actively. In the maritime domain, the big data is the meaningful information which makes and gathers by the navigation and communication equipment from the many ships on the ocean. Also, importance of the maritime safety is emphasized, because maritime accidents are rising with increasing of maritime traffic. To support prevention of maritime accidents, in this paper, we developed a vessel traffic display and statistic system based on AIS messages from the many vessels of maritime. Also, to verify the developed system, we conducted tests for vessel track display function and vessel traffic statistic function based on two test scenarios. Therefore, we verified the effectiveness of the developed system for vessel tracks display, abnormal navigation patterns, checking failure of AIS equipments and maritime traffic statistic analyses.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.11
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• pp.41-47
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• 2005

Even more than 240 commercial geostationary communication satellites currently on orbit at the higher location than the GPS orbit altitude perform their own missions only by the support of the ground segment because of weak visibility from GPS. In addition, the orbit determination accuracy is very low without using two or more dedicated ground tracking antennas in intercontinental ground segment, since the satellite hardly moves with respect to the ground station. In this paper, we propose the GSPS(Geostationary Satellite Positioning System) in circular orbits of two sidereal days period higher than the geosynchronous orbit for orbit determination and autonomous satellite operation. The GSPS is conceived as a ranging system in that unknown positions of a geostationary satellite can be acquired from the known positions of the GSPS satellites. Each GSPS satellite transmits navigation data, clock data, correction data, and geostationary satellite command to control a geostationary satellite.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.11
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• pp.93-100
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• 2005

In this paper, we implement the embedded speech recognition system to support various application services such as audio and video control using speech recognition interface on cars. The embedded speech recognition system is implemented and ported in a DSP board. Because MIC type and speech codecs affect the accuracy of speech recognition. And also, we optimize the simulation and test environment to effectively remove the real noises on a car. We applied a noise suppression and feature compensation algorithm to increase an accuracy of sppech recognition on a car. And we used a context dependent tied-mixture acoustic modeling. The performance evaluation showed high accuracy of proposed system in office environment and even real car environment.