• Journal of Korean Society of Transportation
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• v.24 no.2 s.88
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• pp.157-168
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• 2006

Spatial detection system such as AVI, GPS, and Beacon etc. can provide spatial travel time only after a vehicle Passes through a road section. In this context, majority of the existing studies on the link travel time estimation area has focused on the arrival time-based link travel time estimation. rather than departure time-based link travel time estimation. Even if some of the researches on this area have developed departure time-based link travel time estimation algorithms, they are limited in that they are not applicable in a real-time mode. The objective of this study is to develop an departure time-based link travel time estimation algorithm which is applicable in a real-tine mode. Firstly, this study discussed the tradeoff between accuracy and timeliness of the departure time-based on-line link travel time estimates. Secondly, this study developed an departure time-based on-line link travel time estimation algorithm which utilizes the Baysian inference logic. It was found that the proposed approach could estimate departure time-based link travel times in a real-time context with an acceptable accuracy and timeliness.

• Journal of Industrial Technology
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• v.23 no.A
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• pp.41-46
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• 2003

Because the quality of a radio link in real environment is generally varied with time, there is a difference between the delay in the real environment and one obtained from the analytic model where a time-varying link model is not used as a link model for a Bluetooth. This paper analyzes the transmission delay of a message in the time-varying radio link model for the Bluetooth. The time-varying radio link is modeled with a two-state Markov model. The mean transmission delay of the message is analytically obtained in terms of the arrival rate of the message, the state transition probability in the Markov model, and the packet error rate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5D
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• pp.739-746
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• 2006

The bus probe-based link travel times were more readily available due to bus' fixed route schedule and it was different from that of taxi-based one in its value for the same link. At the same time, the bus-based one showed less accurate information than the taxi-based link travel time, in terms of reliability expressed by 1-RMSE(%) measure. The purpose of this thesis is to develop a heuristic algorithm for mixing both sources-based link travel times. The algorithm used both real-time and historical profile travel times. Real-time source used 4 consecutive periods' average and historical source used average value of link travel time for various congestion levels. The algorithm was evaluated for Seoul urban arterial network 3 corridors and 20 links. The results based on the developed algorithm were superior than the mere fusion based link travel times and the reliability amounted up to 71.45%. Some limitation and future research agenda have also been discussed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4429-4445
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• 2019

As low-power and low-rate WSNs are being widely used for industrial applications, the scheduling of such applications becomes a critical issue to guarantee meeting the stringent requirements of determinism and tight latencies. This paper studies the link scheduling problem for real-time industrial applications in time-slotted channel hopping (TSCH) networks. We propose a heuristic algorithm for centralized link scheduling referred to as path-collision aware least laxity first (PC-LLF) algorithm, which dynamically prioritizes the packets based on the laxity time to the end-to-end deadlines and the amount of collisions that messages might deal with along their designated paths to the destination device. We propose schedulability analysis of real-time applications scheduled under our prioritization approach over TSCH networks, based on the literature on real-time schedulability analysis of multiprocessors and distributed systems. We show that our methodology provides an improved schedulability condition with respect to the existing approaches. Performance evaluation studies quantify to quantify the performance of our proposed approach under a variety of scenarios.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.97-100
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• 1997

Fieldbuses are used as the lowest level communication network for real-time communication in factory automation and process control systems. Data generated from field devices can be divided into three categories: sporadic real-time, periodic real-time and non real-time data. Since these data share one fieldbus network medium, it needs a method that allocate the limited bandwidth of fieldbus network to the sporadic real-time, periodic real-time and non real-time traffic. This paper introduces an implementation method of bandwidth allocation scheme introduced in [51 on PROFIBUS. Using the modified PROFIBUS FDL(Fieldbus Data Link layer), the bandwidth allocation scheme introduced in [51 is verified by the experiments.

• Journal of Korea Multimedia Society
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• v.17 no.4
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• pp.478-489
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• 2014

Recently, flood damage by frequent localized downpours in cities are on the increase on account of abnormal climate phenomena and growth of impermeable area by urbanization. In this study, we are focused on flooding on roads which is the basis of all means of transportation. To calculate real-time accumulated rainfall on a road link, we use the Coefficient of Correlation Weighting method (CCW) which is one of the revised methods of missing rainfall as we consider a road link as a unobserved rainfall site. CCW and real-time accumulated rainfall entered through the Internet are used to estimate the real-time rainfall on a road link. Together with the real-time accumulated rainfall, flooding history, rainfall range causing flooding of a road link and frequency probability precipitation for road design are used as factors to determine the Flood Risk Index on roads. We simulated two cases in the past, July, 7th, 2009 and July, 15th, 2012 in Busan. As a result, all of road links included in the actual flooded roads at that time got the high level of flood risk index.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.6
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• pp.789-796
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• 2013

Next Generation Weapon system from the center of the platform to share information in real-time Network Centric Warfare(NCW: Network Centric Warfare) has been changed. Data link system is defined as a network. That is, all in real-time battlefield information is to enable sharing. Data link system is classified as a precision strike, Monitoring/control, control of a Patriot missile battery systems. These systems are most effective in a Joint warfare and precision strike. Data Link Systems(Data Communications) implementation is accomplished by using the KDLM(Korean Data Link Modem) and Radio Transceiver. KDLM is operated in conjunction with the legacy Radios(re-using fielded HF/VHF/UHF radio systems). In this paper, we describe in terms of KDLM system design. In this paper, the proposed design structure is how to effectively interact with legacy various radio. First, The results provide an analysis of that Dynamic TDMA system and apply modem structure. Radio characteristics data are necessary for an effective TDMA system design. This article analyzes the test results and describes the structure to improve the receive performance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.146-154
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• 2007

In this paper, we have presented a real-time transfer mechanism for the delay-sensitive data in WSNs (Wireless Sensor Networks). The existing methods for real-time data transfer select a path whose latency is shortest or the number of hops is least. Although the approaches of these methods are acceptable, they do not always work as efficiently as they can because they had no consideration for the link error rates. In the case of transmission failures on links, they can not guarantee the end-to-end real-time transfer due to retransmissions. Therefore, we have proposed an algorithm to select a real-time transfer path in consideration of the link error rates. Our mechanism estimates the 1-hop delay based on the link error rate between two neighboring nodes, which in turn enables the calculation of the expected end-to-end delay. A source node comes to choose a path with the shortest end-to-end delay as a real-time route, and sends data along the path chosen. We performed various experiments changing the link error rates and discovered that this proposed mechanism improves the speed of event-to-sink data transfer and reduces delay jitter. We also found that this mechanism prevents additional energy consumption and prolongs network lifetime, resulting from the elative reduction of transmission failures and retransmissions.

• 전기의세계
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• v.23 no.2
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• pp.23-27
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• 1974

On-line real time system은 보통 중앙장치(computing center), 단말장치(remote terminal) 및 통신회선(communication link)의 세부분시스템(subsystem)으로 구성되어 있는데, 이들 각각에 대한 구성요소와 그 기능에 대하여 약술하려고 한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.5
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• pp.454-460
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• 2012

DTC(Data Terminal Controller) for UAV has been developed using FPGA. It provides the functions of Error Correction and Time-division Mux/Demux for stable data-link. RTOS VxWorks also has been used for real-time control of data-link. FPGA Design of DTC facilitates the modification and extension of various I/O device, and VxWorks ensures real-time availability of data-link control and provides flexibilities of changes of S/W design. The DTC is expected to be deployed easily for various UAV systems.