• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.2
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• pp.54-59
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• 2010

The flight deck crew must manage complexity during daily flight operations. The Airline may obtain data regarding threats and errors through LOSA(Line Operations Safety Audits) on normal flights as predictive safety tool in Safety Management System of the Airline to actively improve the systems such as SOP(Standard Operation Procedure), training, evaluation and the TEM(Threat and Error Management) for the flight deck crew. The flight deck crew make errors when they fail managing threats. The crew mismanage around ten percent of threats and commit errors. The major mismanaged threats are aircraft malfunction, ATC(Air Traffic Communication), and wether threats. The effective countermeasures of TEM for manageing threats are leadership, workload management, monitor & cross check, Vigilance, communication environment and cooperation of the crew. It is important that organizations must monitor for the hazards of threats and improve system for the safer TEM environments.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1451-1453
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• 2000

The automatic/driverless operation which are great important techniques in metro railway are required to increase higher safety, greater reliability, and transport capacity. To satisfy such demands, we must have the system design and testing technique for the railway system operation. These techniques are related to the onboard train control and communication systems which include TCMS(Train Control and Monitoring System), ATO(Automatic train Operation), ATC(Automatic train Control), and TWC(Train to wayside communication). These sub-systems must be interfacing with not only each others but also the signal system on the ground. We tested the train control system on the 7 line that has been developed on the basis of the standardized type EMU for korea railway systems.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.172-179
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• 2000

The automatic/driverless operation which are great important techniques in metro railway are required to increase higher safety, greater reliability, and transport capacity. To satisfy such demands, we must have the system design iかd testing technique for the railway system operation. These techniques are related to the onboard train control and communication systems which include TCMS(Train Control md Monitoring System), ATO(Automatic train Operation), ATC(Automatic train Control), and TWC(Train to wayside communication). These sub-systems must be interfacing with not only each others but also the signal system on the ground. We tested the train control system on Test line that has been developed on the basis of the standardized type EMU for korea railway systems. This test line which is located in Sangju, have been constructed for testing 7 ＆ 8 line of Seoul Metro railway.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.814-817
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• 2003

Assuming that life of urban transit signalling is about 20 years with the flow of technology development, Seoul urban transit will be required to prepare for improvement soon. The highly developed countries preceding several levels rather than Korea are faced with commercial service which uses RF, ATC and ATO in Train Control System. European highly developed countries in the field of railroad have been progressing standardization and technology development of signalling associated with related manufacturers for direct operation between nations. For that, a effective train control system with radio beyond control levels by the existing wayside-onboard communication is in a developed and used stage. The systems which advanced countries have been progressing seem to be applied to domestic within 5 years from now. At present, there are no countries using CBTC for service throughout the world. So, this is investigated to focus on the routes ready to be installed with completed CBTC and trying to introduce the technology. Especially, considerations for economic aspect are mainly reviewed about controlling ability of headway, flexibility, extension aspect and construction cost on the basis of paper examined in NYCT.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.47.4-47
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• 2001

The automatic-driverless operation, a very important technique for metro railways, is necessary for achieving higher safety, greater reliability, and bigger transport capacity. To achieve these things, we have to build up the system design and tasting techniques for the railway system operation. These techniques are related to the onboard train control and communication systems which include TCMS(Train Control and Monitoring System), ATO(automatic train Operation), ATC(Automatic train Control), and TWC(Train to wayside communication). These sub-systems should interface not only with each other but also between the sub-systems and the signal system on the ground. For the saving of energy, we designed coasting strategy of ATO system, In this paper, we developed ATO system and tested on the test line and ...

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4044-4062
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• 2016

We investigate the optimization of energy consumption in Mobile Cloud environment in this paper. In order to optimize the energy consumed by the CPUs in mobile devices, we put forward using the asymptotic time complexity (ATC) method to distinguish the computational complexities of the applications when they are executed in mobile devices. We propose a multi-scale scheme to quantize the channel gain and provide an improved dynamic transmission scheduling algorithm when offloading the applications to the cloud center, which has been proved to be helpful for reducing the mobile devices energy consumption. We give the energy estimation methods in both mobile execution model and cloud execution model. The numerical results suggest that energy consumed by the mobile devices can be remarkably saved with our proposed multi-scale scheme. Moreover, the results can be used as a guideline for the mobile devices to choose whether executing the application locally or offloading it to the cloud center.

• Journal of Communications and Networks
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• v.12 no.2
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• pp.140-149
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• 2010

Green communication is a new paradigm of designing the communication system which considers not only the processing performance but also the energy efficiency. Power control management is one of the approaches in green communication to reduce the power consumption in distributed communication system. In this paper, we propose improved power control schemes for mobile satellite systems with ancillary terrestrial components (ATCs). In order to increase system capacity and reduce the transmitting power of the user's equipment, we propose an efficient channel estimation method consisting of a modified open-loop power control (OLPC) and closed-loop power control (CLPC). The OLPC works well if the forward and reverse links are perfectly correlated. The CLPC is sensitive to round-trip delay and, therefore, it is not effective in a mobile satellite system. In order to solve the above problem, we added monitoring equipment to both the OLPC and CLPC to use information about transmitting power that has not yet been received by the receiver over the satellite/ATC channel. Moreover, we adapted an efficient pilot diversity of both OLPC and CLPC in order to get a better signal to interference plus noise ratio estimation of the received signal.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.404-411
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• 2009

In this paper, in order to increase system capacity and reduce the transmitting power of the user's equipment, we propose an efficient power estimation consisting of a modified open-loop power control (OLPC) and closed-loop power control (CLPC) schemes for mobile/satellite communications systems. The OLPC works well if the forward and reverse links are perfectly correlated and the CLPC is sensitive to round-trip delay (RTD). Therefore, it is not effective in mobile/satellite system. In order to solve the above problem, we added monitoring equipment to both the OLPC and CLPC to use information about transmitting power that has not yet been received by the receiver over the satellite/ATC channel. Moreover, we adapted an efficient pilot diversity of both OLPC and CLPC in order to get a better signal to interference plus noise ratio (SIR) estimation of the received signal.

• Journal of Communications and Networks
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• v.17 no.1
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• pp.58-66
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• 2015

Aeronautical communication networks (ACN) is an emerging concept in which aeronautical stations (AS) are considered as a part of multi-tier network for the future wireless communication system. An AS could be a commercial plane, helicopter, or any other low orbit station, i.e., Unmanned air vehicle, high altitude platform. The goal of ACN is to provide high throughput and cost effective communication network for aeronautical applications (i.e., Air traffic control (ATC), air traffic management (ATM) communications, and commercial in-flight Internet activities), and terrestrial networks by using aeronautical platforms as a backbone. In this paper, we investigate the issues about connectivity, throughput, and delay in ACN. First, topology of ACN is presented as a simple mobile ad hoc network and connectivity analysis is provided. Then, by using information obtained from connectivity analysis, we investigate two communication models, i.e., single-hop and two-hop, in which each source AS is communicating with its destination AS with or without the help of intermediate relay AS, respectively. In our throughput analysis, we use the method of finding the maximum number of concurrent successful transmissions to derive ACN throughput upper bounds for the two communication models. We conclude that the two-hop model achieves greater throughput scaling than the single-hop model for ACN and multi-hop models cannot achieve better throughput scaling than two-hop model. Furthermore, since delay issue is more salient in two-hop communication, we characterize the delay performance and derive the closed-form average end-to-end delay for the two-hop model. Finally, computer simulations are performed and it is shown that ACN is robust in terms of throughput and delay performances.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.8
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• pp.1064-1069
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• 2014

The railway signalling system plays an essential role in the headway and routing control for a safe and efficient train operation. The reliable and safe operation of the system is very important because the failure of the railway signalling system can lead to the collision, derailment, or unexpected stop of a train. So far, the conventional wayside signal mode (ATS: Automatic Train Stop) has been generally used as the railway signalling system. However, this system is highly linked to a risk of major accidents resulted from human mistakes such as missing a signal or careless control of train speed. Accordingly, the onboard signal mode (ATC: Automatic Train Control) as an alternative of ATS has been recently introduced and applied to transmit effectively the information on speed control of a train by using computers and communication equipment. In the process of replacing the obsolete signal system, it is necessary to switch over the system while providing passengers with normal services. Therefore, the integration of a railway signaling system compatible for both ATS and ATC and its interface is discussed in this study. In particular, the implementation scenario required for operation planning of the integrated system was designed, and the results as well as effects of its applicability test were also presented.