• International Journal of Railway
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• v.3 no.3
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• pp.106-112
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• 2010

Accidents at level crossing have large portion on train accidents, and causes economical loss by train delay and operational interruption. Various safety equipments are employed to reduce the accident at level crossing, but existing warning device, and crossing barrier are simple train-oriented protection equipments. In this paper, intelligent railway level crossing system is proposed to prevent and reduce accidents. For train driver's prompt action, image of level crossing and obstacle warning message are continuously provided to train driver through wireless communication in level crossing control zone. Obstacle warning messages, which are extracted by computer vision processing of captured image at level crossing, are recognized by train driver through message color, flickering and warning sound. It helps train driver to decide how to take an action. Meanwhile, for vehicle driver's attention, location and speed of approaching train are given to roadside equipments. We identified the effect of proposed system through test installation at Sea train and Airport level crossing of Yeong-dong line.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1441-1444
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• 2009

In this paper a platform that makes it possible the simulations of the vehicle operational control for PRT (Personal Rapid Transit) is introduced. PRT system has very short headway and requires accurate speed control of the vehicles to avoid the impact between the vehicles. The proposed platform is composed of central control system, station control system, communication control system, AP for wireless communication, and monitoring system. Simple operational test scenarios are presented and the effectiveness of the proposed platform is shown using the test scenarios.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.2
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• pp.483-503
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• 2015

This paper analyzes the optimal user density and power allocation for Device-to-Device (D2D) communication underlaying cellular networks on multiple bands with the target of maximizing the D2D transmission capacity. The entire network is modeled by Poisson point process (PPP) which based on stochastic geometry. Then in order to ensure the outage probabilities of both cellular and D2D communication, a sum capacity optimization problem for D2D system on multiple bands is proposed. Using convex optimization, the optimal D2D density is obtained in closed-form when the D2D transmission power is determined. Next the optimal D2D transmission power is obtained in closed-form when the D2D density is fixed. Based on the former two conclusions, an iterative algorithm for the optimal D2D density and power allocation on multiple bands is proposed. Finally, the simulation results not only demonstrate the D2D performance, density and power on each band are constrained by cellular communication as well as the interference of the entire system, but also verifies the superiority of the proposed algorithm over sorting-based and removal algorithms.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.736-743
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• 2016

In accordance with the trend of higher speed and automation, the Train Control System is building on the technology of control methods using radio in the technology of exchanging information by wire, toward a wireless communication method that will be applied using LTE-R radio communication technology with $4^{th}$ generation LTE mobile communication a $2^{nd}$ generation GSM-R. Therefore, a standard specification suitable for the Korea Radio based Train Control System-2(below KRTCS-2) for the 350km/h class using wireless communication is created; a prototype based on the standard specification is installed on a high-speed train and is installed on a test section(Ik san-Jeong eup) on the Honam high speed line to ensure the reliability and safety of the standard specifications, which are verified through various performance tests. In the future, the standard specification that has been established as a national railway standard, and the standard specifications will be commercialized by applying the train control system to conventional and High speed railway lines.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4240-4258
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• 2016

A practical iterative channel estimation technique is proposed for the multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system in the high-speed mobile environment, such as high speed railway scenario. In the iterative algorithm, the Kalman filter and data detection are jointed to estimate the time-varying channel, where the detection error is considered as part of the noise in the Kalman recursion in each iteration to reduce the effect of the detection error propagation. Moreover, the employed Kalman filter is from the canonical state space model, which does not include the parameters of the autoregressive (AR) model, so the proposed method does not need to estimate the parameters of AR model, whose accuracy affects the convergence speed. Simulation results show that the proposed method is robust to the fast time-varying channel, and it can obtain more gains compared with the available methods.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1008-1013
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• 2011

The importance of broadband wireless communication system at subway tunnels is growing up. At 18GHz wireless video transmission system, the transmitter requires a digital modulation method. At subway tunnel, A 18GHz's influence of the multi-pass padding is strong. OFDM digital modulation that is strong for multi-pass padding is recommended. Duplexing methode uses FDD to transmit and receive broadband data at the same time. In the case of FDD we assign a private use channel each with the transmission at the receiving. In this paper, We implement multiple access wireless OFDM transceiver. We verified that one ground transceiver communicates with two car transceiver at the same time.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.2089-2094
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• 2010

The importance of broadband wireless communication implemented at subway tunnels is growing up. At 18GHz wireless video transmission system, the transmitter requires a digital modulation method. At subway tunnel, A 18GHz's influence of the multi-pass padding is strong. OFDM digital modulation that is strong for multi-pass padding is recommended. In this paper, Suitable to a subway wireless video transmission OFDM receiver is designed. OFDM receiver system has 6dB gaion because uses diversity of space diversity and MRC(Maximum Ratio Combining) diversity. The transmitter system use C&ITechnologies's transmitter board. IF frequency of receiver is 480MHz. OFDM modulation parameter is as follow, The bandwidth is 8MHz, The numuber of carrier if 2,000, The modulation methode is QAM16, The guard interval is 1/32.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.1151-1152
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• 2008

Recently, ubiquitous sensor network forms the self-organization network, and transfers the information among sensor nodes that have computing technology ability. In this paper, we design and implement U-IT system for monitoring the safety of metro railway and underground shopping malls. For this, we implement sensor nodes to support IEEE 802.15.4 wireless communication standard using low power. Also we implement USN gateway node system to transmit the collected data from sensor nodes to database server over CDMA cellular network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.9
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• pp.1172-1179
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• 2020

With the establishment of the railway integrated radio network (LTE-R) environment, radio-based train control transmission and reception and various forms of service are provided. The smooth delivery of these services requires improved performance in a highly reliable and available wireless environment. This paper measured the LTE-R radio communication environment to improve radio communication performance of railway integrated wireless network reliability and availability, analyzed the results, and established the wireless environment model. Based on the built-up model, we also proposed an improved radio-access algorithm to control trains for improved reliability, suggesting a way to improve stability for handover that occur during open-air operation, and proposed an algorithm for frequency auto-heating to improve availability. For simulation, data were collected from the Korea Rail Network Authority (Daejeon), Manjong-Gangneung KTX route, which can measure the actual data of LTE-R wireless environment, and the results of the simulation show performance improvement through algorithm.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.652-659
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• 2011

Due to overuse of commercial network systems such as bluetooth and WI-FI, the problems of frequency interruption and line-crossing may arise. For this reason, wireless communication frequency ISM 2.4GHz, a recently adapted concept in Korea which is employeed by RF-CBTC system, is predicted not to have guarantee for outstanding and continuous performance. Therefore in this study, considering these problems, 5GHz capacity wireless Lans with international standard 802.11a/b/g applied were installed in the underground urban transit areas and it was proved that these lans exceeded the performance level of 2.4GHz with international standard 802.11b which is being introduced in the nation. In addition, it was verified through carrying out an application test that the communication condition was stable in a running train with high speed in the tunnel.