• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4856-4871
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• 2015

Backpressure based scheduling has been considered as a promising technique for improving the throughput of a wide range of communication networks. However, this scheduling technique has not been well studied for heterogeneous wireless networks. In this paper, we propose a virtual-queue based backpressure scheduling (VQB) algorithm for heterogeneous multi-hop wireless networks. The VQB algorithm introduces a simple virtual queue for each flow at a node for backpressure scheduling, whose length depends on the cache size of the node. When calculating flow weights and making scheduling decisions, the length of a virtual queue is used instead of the length of a real queue. We theoretically prove that VQB is throughput-optimal. Simulation results show that the VQB algorithm significantly outperforms a classical backpressure scheduling algorithm in heterogeneous multi-hop wireless networks in terms of the packet delivery ratio, packet delivery time, and average sum of the queue lengths of all nodes per timeslot.

• Journal of Digital Contents Society
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• v.14 no.2
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• pp.161-169
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• 2013

Experiments and practices are critical instructional activities for teaching and learning natural sciences. However, by learning the experimental procedures in advance with the help of Virtual Experiments, natural science majors may address danger of handling chemicals before carrying out experiments in the laboratories. Virtual Experiments, a mobile learning app, provides learners with interactions between the learners and the contents by using the sensor built-in Android-platform smart phones. With the app, learners may handle the chemicals and experiment apparatuses, verify the reactions and assembly of the chemicals and instruments in advance. This paper describes the design and development of the Virtual Experiments in hope to promote the integration of mobile learning apps in order to better engage learners in the laboratories.

• The Journal of the Korea institute of electronic communication sciences
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• v.19 no.2
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• pp.473-482
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• 2024

This study utilized virtual reality to construct a simulated public restroom environment to identify potential hazards. The objective was to discern actual risks in real-world public restrooms through this virtual setup. During the virtual restroom experience, data from the built-in 3-axis accelerometer and gyroscope sensors of testor's smart phones were collected. Analysis of this data helped in identifying spatio temporal factors impacting the users. The determination of these factors as risk elements was based on an evaluation algorithm grounded in data analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.549-559
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• 2015

In this paper, an efficient dynamic reactive motion planning method for an autonomous vehicle in a dynamic environment is proposed. The purpose of the proposed method is to improve the robustness of autonomous robot motion planning capabilities within dynamic, uncertain environments by integrating a virtual plane-based reactive motion planning technique with a sensor fusion-based obstacle detection approach. The dynamic reactive motion planning method assumes a local observer in the virtual plane, which allows the effective transformation of complex dynamic planning problems into simple stationary ones proving the speed and orientation information between the robot and obstacles. In addition, the sensor fusion-based obstacle detection technique allows the pose estimation of moving obstacles using a Kinect sensor and sonar sensors, thus improving the accuracy and robustness of the reactive motion planning approach. The performance of the proposed method was demonstrated through not only simulation studies but also field experiments using multiple moving obstacles in hostile dynamic environments.

• The Journal of Korean Institute for Practical Engineering Education
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• v.3 no.1
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• pp.76-83
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• 2011

In this paper we suggest an effective teaching plan for measurement engineering by utilizing the NI-ELVIS(National Instrument Educational Laboratory Virtual Instrumentation Suite). ELVIS is a development platform for LabVIEW-based design and prototyping environment. It consists of LabVIEW-based virtual instruments, a multifunctional data acquisition device, and a custom-designed benchtop workstation and prototyping board. Therefore it can replace the expensive instruments for the effective education in the area of electrical engineering. This platform can be applicable for the sensor instrumentation engineering study, though it is a multidisciplinary learning including electrical engineering, sensor technology, signal processing and data analysis. We hope this approach can be used for the other educational area related the electrical experimental education.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5442-5463
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• 2016

Designing efficient routing protocols for a wireless sensor network with mobile sinks (mWSN) is a challenging task since the network topology and data paths change frequently as sink nodes move. In this paper, we design a novel lightweight reactive ring based routing protocol called R3, which removes the need of proactively maintaining data paths to mobile sinks as they move in the network. To achieve high packet delivery ratio and low transmission cost, R3 combines ring based forwarding and trail based forwarding together. To support efficient ring based forwarding, we build a ring based structure for a network in a way such that each node in the network can easily obtain its ring ID and virtual angle information. For this purpose, we artificially create a virtual hole in the central area of the network and accordingly find a shortest cycled path enclosing the hole, which serves as base ring and is used for generating the remaining ring based structure. We accordingly present the detailed design description for R3, which only requires each node to keep very limited routing information. We derive the communication overhead by ring based forwarding. Extensive simulation results show that R3 can achieve high routing performance as compared with existing work.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2413-2418
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• 2007

IN wireless sensor networks (WSNs), one challenging issue is to In wireless sensor networks (WSNs), one challenging issue is to construct a virtual backbone in a distributed and localized way while considering energy limitation. Dominating set has been used extensively as core or virtual backbone in WSNs for the purposes like routing and message broadcast. To ensure network performance, a good dominating set construction protocols should be simple and avoid introducing extra message. In addition, the resulting dominating set should be small, connected, and take into account the energy level at each node. This paper studies efficient and simple virtual backbone construction protocol using defer time in IEEE 802.15.4- based WSNs (e.g. Zigbee). The efficiency of our proposed protocol is confirmed through simulation results.

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.4
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• pp.439-444
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• 2009

Recently, a wide range of next-generation's game consoles has been developed by many game makers. Particularly, active interaction between users and games is required more than ever before for giving gamers the fullest pleasure. In this work, an infrared image sensor based position recognition system which can be used for virtual game interface is proposed. Furthermore, two kinds of compensation algorithms and Extended Kalman Filter are utilized to enhance the performance of the proposed system. The proposed system can effectively generate the position of the gamer in the face of the coordinate distortion and noise. To verity the feasibilities of the proposed system, various experiments are carried out.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.2
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• pp.164-171
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• 2010

We have studied the port-automation system which is requested by the steep increment of cost and complexity for processing the freight. This paper will introduce a new algorithm for navigating and controlling the autonomous Guided Vehicle (AGV). The camera has the optical distortion in nature and is sensitive to the external ray, the weather, and the shadow, but it is very cheap and flexible to make and construct the automation system for the port. So we tried to apply to the AGV for detecting and tracking the lane using the CCD camera. In order to make the error stable and exact, this paper proposes new concept and algorithm for obtaining the error is generated by the Virtual Photo-Sensor Array (VPSA). VPSAs are implemented by programming and very easy to use for the various autonomous systems. Because the load of the computation is light, the AGV utilizes the maximal performance of the CCD camera and enables the CPU to take multi-tasks. We experimented on the proposed algorithm using the mobile robot and confirmed the stable and exact performance for tracking the lane.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.84.2-84
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• 2001

To remove the logical error inexpensively, in this paper, we propose new concept of VPLF(Virtual PLC Framework) which consists of VPLE(Virtual PLC Editor), Virtual Machine(Virtual Machine), VMC(Virtual Machine Control panel), Virtual PLC Program Editor(VPLPE) and Object Inspector. VPLC is for PLC hardware and software and VM is for the target to be controlled. VPLC has an individual editor and the screen of configuration. With using individual editor in VPLC, we can edit and compile to PLC ladder program. In VM, there are many kinds of object for machine elements, actuator, sensor and so on. The VPLC and VM are interlinked each other and controlled by the PLC program in real time. So, we can get the powerful realization as the machine is ...