• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.25 no.4
• /
• pp.581-587
• /
• 2021

Real-time video streaming scheme for multimedia content delivery and remote conference services is one of technologies that are significantly sensitive to data transmission delay. Recently, because of COVID-19, real-time video streaming contents for the services are significantly increased such as personal broadcasting and remote school class. In order to support the services, there is a growing emphasis on low transmission delay and secure content delivery, respectively. Therefore, our research proposed a packet aggregation algorithm to reduce the transmission delay of selectively encrypted video transmission for real-time video streaming services. Through the application of the proposed algorithm, the selectively encrypted video framework can control the amount of MPEG-2 TS packets for low latency transmission with a consideration of packet priorities. Evaluation results on testbed show that the application of the proposed algorithm to the video framework can reduce approximately 11% of the transmission delay for high and low resolution video.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.9B
• /
• pp.1314-1321
• /
• 2010

This system configures a position Sensor as installing on the ship and a guidance system docking of ship what distinguish of the ship about the use and size. The maintain system is received the result of distinction via UWB reader. This system send a information of ship of docking position to user. Thus it suggests the safety to prevent from crash among ships and saves energy and stop waste. The proposed system periodically updates the information of docking position of the ship and monitors in real-time according to the user's request from personal mobile devices. In this paper, we implement of a guidance system Testbed for docking of the ship using position UWB sensor. And user is provided convenience to find easily user's ship in docking area through user interface with Java. Addedly it is possible to prevent ship theft.

• Structural Monitoring and Maintenance
• /
• v.9 no.4
• /
• pp.359-371
• /
• 2022

Bridges are critical to the civil engineering infrastructure network as they facilitate movement of people, the transportation of goods and services. Given the aging of bridge infrastructure, federal officials mandate visual inspections biennially to identify necessary repair actions which are time, cost, and labor-intensive. Additionally, the expansion joints of bridges are rarely monitored due to cost. However, expansion joints are critical as they absorb movement from thermal effects, loadings strains, impact, abutment settlement, and vehicle motion movement. Thus, the need to monitor bridge expansion joints efficiently, at a low cost, and wirelessly is desired. This paper addresses bridge joint monitoring needs to develop a cost-effective, real-time wireless system that can be validated in a full-scale bridge structure. To this end, a wireless expansion joint monitoring was developed using commercial-off-the-shelf (COTS) sensors. An in-service bridge was selected as a testbed to validate the performance of the developed system compared with traditional displacement sensor, LVDT, temperature and humidity sensors. The short-term monitoring campaign with the wireless sensor system with the internet protocol version 6 over the time slotted channel hopping mode of IEEE 802.15.4e (6TiSCH) network showed reliable results, providing high potential of the developed system for effective joint monitoring at a low cost.

• Journal of Institute of Control, Robotics and Systems
• /
• v.4 no.4
• /
• pp.420-426
• /
• 1998

It is the purpose of this paper to make a preliminary study on the use of repetitive control to improve velocity accuracy by eliminating repetitive disturbances caused by machining inaccuracies of the axis of rotation location. If the control system can be intelligent enough to compensate for such machining errors, then one may be able to improve the accuracy of the velocity control, or alternatively, one may maintain the same accuracy and relax the machining tolerances required. This could decrease cost significantly. Experiments are performed testing repetitive control methods on a constant speed rolling operation testbed. The experimental results show very substantial decreases in the tracking error of the system. Spectral data of the output motion are given to demonstrate the attenuation of the disturbance frequencies and harmonics, related to the bandwidth being used. It is seen that the simplest form of repetitive control which is very easily implemented, can produce striking improvement in control system performance in such belt drive rolling operations, and the learning can be accomplished in a short time.

• Journal of the Institute of Convergence Signal Processing
• /
• v.12 no.3
• /
• pp.212-216
• /
• 2011

Fault detection technique for photovoltaic power systems is significant to dramatically reduce economic damage in industrial fields. This paper presents a novel fault detection approach using Fourier neural networks and stochastic decision making strategy for photovoltaic systems. We achieve neural modeling to represent its nonlinear dynamic behaviors through a gradient descent based learning algorithm. Next, a general likelihood ratio test (GLRT) is derived for constructing a decision malling mechanism in stochastic fault detection. A testbed of photovoltaic power systems is established to conduct real-time experiments in which the DC power line communication (DPLC) technique is employed to transfer data sets measured from the photovoltaic panels to PC systems. We demonstrate our proposed fault detection methodology is reliable and practicable over this real-time experiment.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.8
• /
• pp.3900-3916
• /
• 2019

The modern mobile devices are typically equipped with multiple network interfaces, e.g., 4G LTE, Wi-Fi, Bluetooth, but the current implementation of TCP can support only a single path at the same time. The Multipath TCP (MPTCP) leverages the multipath feature and provides (i) robust connection by utilizing another interface if the current connection is lost and (ii) higher throughput than single path TCP by simultaneously leveraging multiple network paths. However, if the performance between the multiple paths are significantly diverse, the receiver may have to wait for packets from the slower path, causing reordering and buffering problems. To solve this problem, previous MPTCP schedulers mainly focused on predicting the latency of the path beforehand. Recent studies, however, have shown that the path latency varies by a large margin over time, thus the MPTCP scheduler may wrongly predict the path latency, causing performance degradation. In this paper, we propose a new MPTCP scheduler called, choose fastest subflow (CFS) scheduler to solve this problem. Rather than predicting the path latency, CFS utilizes the characteristics of these paths to reduce the overall flow completion time by redundantly sending the last part of the flow to both paths. We compare the performance through real testbed experiments that implements CFS. The experimental results on both synthetic packet generation and actual Web page requests, show that CFS consistently outperforms the previous proposals in all cases.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.2B
• /
• pp.148-158
• /
• 2011

Stationary nodes and mobile nodes co-exist wireless sensor network(WSN) can provide variety of new services. The stationary sensor node acts not only the gathering the environmental sensing data but also a access point to bidirectional communication with numerous mobile sensor nodes(mobile node), and the mobile sensor nodes are installed inside mobile objects and identify the location in real-time and monitor the internal status of the object. However, only using the legacy WSN protocol, it is impossible to set up the stable network due to the several reasons caused by the free-mobility of the mobile nodes. In this paper, we suggest three methods to increase the hit-ratio of the asynchronous message delivery(AMD) among mobile nodes. We verified the performance of the suggested methods under the stationary-mobile co-existed WSN testbed.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.5
• /
• pp.1227-1233
• /
• 2013

The new engineering challenges lead to a control of a vehicle more and more complex. To tackle this issue, Hardware-In-the-Loop (HIL) simulation is used in the development of real-time embedded systems. In this paper, the control of a double parallel hybrid vehicle is validated using a reduced power HIL simulation. A graphical description is used in order to organize the emulation and control. Some experimental results of a versatile testbed are given for the Peugeot $3{\infty}8$ HYbrid4.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.598-601
• /
• 2001

As many sensors and actuators are used in many automated system, various industrial networks are adopted for digital control system. In order to take advantages of the networking, however, the network implementation should be carefully designed to satisfy real-time requirements considering network delays. This paper presents the implementation scheme of a networked control system via Profibus-DP network. More specifically, the effect of the network delay on the control performance was evaluated on a Profibus-DP testbed, and a GA based PID tuning algorithm is proposed to demonstrate the fesibility of the networked control system.

• Journal of Institute of Control, Robotics and Systems
• /
• v.8 no.1
• /
• pp.80-88
• /
• 2002

As many sensors and actuators are used in automated systems, various industrial networks are adopted for digital control system. In order to take advantages of the networking, however, the network implementation should be carefully designed to satisfy real-time requirements considering network delays. This paper presents the implementation scheme of a networked control system via Profibus-DP network. More specifically, the effect of the network delay on the control performance was evaluated on a Profibus-DP testbed, and a GA-based PID tuning algorithm is proposed to design controllers suitable for networked control systems.