• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1344-1353
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• 2008

The trend is that the wireless communication system, which has specific characteristics ; low cost & limitation for installation, has been developed more actively than the wire communication system. Therefore, the communication system has been changed from the wire system with an optical cable to the wireless system in the various field of life. In the railroad field, lots of researches on the wireless communication system for the safety of infrastructure and the convenience of passenger have been conducted. The WSN(Wireless Sensor Network), which means same concept with USN(Ubiquitous Sensor Network), pursues the ubiquitous environment which means user can access network at anywhere and anytime. In this paper, the wireless communication technologies which are suitable for the WSN of subway station were investigated and the best solution of WSN was suggested.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.229-236
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• 2017

The railway has recently been expanded with the phase of the future transportation. Accordingly, using the new technologies such as smart devices and LTE-R, the needs for reducing operational costs and improving passenger services have emerged. To realize these needs, the government is pushing to build the dedicated wireless network for the railway systems. In this paper, the shunting route indicator was selected for this study because it has the best effect for the wireless system removed lots of wired cables. And the wireless shunting route indicator applied with LTE-R technology was developed to replace the current wired control system. The functional goal(the wireless control function applied LTE-R), the performance goal(less than 300ms for transferring the control information), and the reliability goal(over the 100,000 hours for MTBF) were set, and these goals were achieved and demonstrated through the test and validation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.12
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• pp.1796-1803
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• 2015

Unlike commercial LTE network, LTE-R railway network is arranged along a railroad track and the base stations of the network (RUs) are also installed on the waysides. For urban railway systems that are composed of underground tunnels, the leakage coaxial cables are widely used due to the radio propagation characteristics in tunnels. In theory, the tunnel sections are interpreted as the waveguide with blank spaces and for this reason, the tunnel sections are expected to be better than open ground sections in terms of the radio propagation characteristics. In this paper, we analyze the radio propagation characteristics based on this theory by replacing the leakage coaxial cables in the network with Yagi antennas. The test has been carried out in the 2.2km tunnel in the Daebul test track of KORAIL with 2.6GHz LTE-R Network. The LTE-R applicability in urban railways has been tested through the analysis on the radio propagation characteristics with the unmanned train operation system in Daebul tunnel.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.4
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• pp.379-386
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• 2016

As well as to operate a high-speed rail, our country with capability to produce high-speed train has developed a number of techniques, such as for a riding comfort improvement, automatic diagnosis for major electrical or mechanical parts, on board measurement for catenary systems and noise reduction of running rolling-stocks are still under development. In this paper, we describe the current status of operation technologies not only traditional railway wireless communication systems but also Long Term Evolution systems which would be deployed as soon as possible, like as in Europe, China and the United States. In addition, we produced the domestic wireless communication networks for railway which KORAIL Corp. has been operating and the schemes and the plans of HSR field test for the fourth generation mobile communication which should be enforced by national research and development.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.6
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• pp.661-668
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• 2012

Wireless sensor network is one of prospective methods for railway monitoring due to the long-term operation and low-maintenance performances. How to supply power to the wireless sensor nodes has drawn much attention recently. In railway monitoring, the idea of converting ambient vibration energy from vibration of railway track induced by passing trains to electric energy has made it a potential way for powering the wireless sensor nodes. In this paper, a bimorph cantilever piezoelectric energy harvester was designed based on a single degree-of-freedom model. Experimental test was also performed to validate the design. The first natural frequency of the bimorph piezoelectric energy harvester was decreased from 117.1 Hz to 65.2 Hz by adding 4 gram tip mass to the free end of the 8.6 gram energy harvester. In addition, the power generation of the piezoelectric energy harvester with 4 gram tip mass at resonant frequency was increased from 0.14 mW to 0.74 mW from $2.06m/s^2$ base excitation compared to stand-alone piezoelectric energy harvester without tip mass.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.797-804
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• 2019

The two Koreas agreed to pursue rail and road connections on September 19, 2018 in the Pyongyang Joint Declaration. In December 2018, they launched a joint investigation for the North Korean railway modernization project. The survey confirmed that the track condition is seriously aging so that it is impossible to operate, and the railway network is well connected to major cities. Therefore, it was reasonable to modernize the aging track of the existing railway network rather than construct a new railway network. This paper proposed the railway communication policy for the improvement of railway lines and the construction of the railway wireless network by analyzing the status of roadbeds and tracks in order to enhance interoperability for the inter-Korean railway connection and safety for preventing the railway accidents.

• Journal of the Korean Society for Railway
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• v.17 no.6
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• pp.402-409
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• 2014

Wireless local area network (WLAN) is a widely used wireless access method due to its easy usability and excellent performance. However, its performance degrades significantly as the number of users increases. In busy train stations, where the number of WLAN users are large and, more importantly the number of simultaneous packet transmission attempts is extremely large due to the time synchronization upon train arrival, the packet transmission delay problem is very severe and almost impossible for WLAN stations to initiate communication with WLAN networks. In this paper, a novel distributed WLAN access scheme for efficient WLAN communication in busy train stations is proposed. Using the proposed scheme, WLAN access delay can be significantly reduced under highly congested traffic environments. Therefore, a significant performance enhancement for the WLAN performance used in the Communication Based Train Control (CBTC) can be achieved.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.432-436
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• 2009

This paper is described that advanced study on network design of remote diagnosis system for power facilities of electric railway. In the field, it is very difficult for worker to diagnosis power facilities including catenary because workers should be maintenance on AC power supply. Therefore, to properly design on remote diagnosis system, we have searched the inside and outside of the country-related technology trends. Also we confirmed that required technologies to design interface technology required for the development of sensor devices and the USN network was designed in accordance with required skills. Throughout variety of requirements, we have development iRFS based ZA sensors and iRFM to receive data of sensor. Also CC2420 is applied as single-chip which used 2.4GHz IEEE802.15.4 compliant RF tranciver designed for low-power and low-voltage wireless applications for ZigBee communication.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1321-1326
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• 2008

According to the conventional train control system, the area of each train is detected by plural track circuits located in a constant distance on railway lines in order to control a distance between trains. The conventional train control system has the difficulty in making use of the substructure thoroughly and transmitting enormous amount of information. To solve those problems, the wireless CBTC system has been a global issue. To apply wireless CBTC system to train system, the following two requirements are preferentially necessary: (1) Dualizing wireless CBTC system to control trains ceaselessly in a system accident, (2) Improving dependency of transmitted information for location and velocity to protect collision and derailment of lightweight trains in advance.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.510-518
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• 2013

These days, interest in radio networks for railways has increased both at home and abroad. In response to this trend, not only the existing radio networks which focus on railway control signals but also the next-generation integrated radio network that can send videos and manage mass storage data are actively being investigated. This paper proposes wireless communication methods to establish integrated radio networks for railways. The paper further suggests a candidate frequency band that could be allocated as the frequency band for railways among the frequency bands currently used in Korea. Based on this paper, we can expect that the domestic railroad will operate more efficiently and that security and convenience of the railroad will reach a superior level. In addition, the Korean integrated radio networks for railways, which cope with the changes in the global technology market, will be established.