Youngtae Jo

Analysis of Vehicle Detection with WSN-Based Ultrasonic Sensors

Existing traffic information acquisition systems suffer from high cost and low scalability. To address these problems, the application of wireless sensor networks (WSNs) has been studied, as WSN-based systems are highly scalable and have a low cost of installing and replacing the systems. Magnetic, acoustic and accelerometer sensors have been considered for WSN-based traffic surveillance, but the use of ultrasonic sensors has not been studied. The limitations of WSN-based systems make it necessary to employ power saving methods and vehicle detection algorithms with low computational complexity. In this paper, we model and analyze optimal power saving methodologies for an ultrasonic sensor and present a computationally-efficient vehicle detection algorithm using ultrasonic data. The proposed methodologies are implemented and evaluated with a tiny microprocessor on real roads. The evaluation results show that the low computational complexity of our algorithm does not compromise the accuracy of vehicle detection.

Energy Effective Time Synchronization inWireless Sensor Network

Advance in processor, memory and wireless communication technique have led to an increase of economical and small wireless sensor nodes. To provide the right responses quickly for the diverse events, wireless sensor nodes have cooperation with together. For successful cooperation, the time synchronization among sensor nodes is an important requirement for application execution. In wireless sensor networks, message packets are used for the time synchronization. However, the transmission of message packets dissipates the battery energy of wireless sensor nodes. Since wireless sensor nodes works on the limited battery capacity, the excessive use of message packets has a negative impact upon their lifetime. In this paper, reference interpolation protocol is proposed for reducing the number of message packets for the time synchronization. The proposed method performs time interpolation between the time of reference packets and the global time of the base station. The proposed method completes the synchronization operation with only two message packets. Due to the simple synchronization procedure, our method greatly reduces the number of synchronization messages. From the decrease in the transmission of message packets, the convergence time among wireless sensor nodes is shortened and the lifetime of wireless sensor nodes is also prolonged as much as the amount of saved battery energy.

Pothole Detection System Using a Black-box Camera

Aging roads and poor road-maintenance systems result a large number of potholes, whose numbers increase over time. Potholes jeopardize road safety and transportation efficiency. Moreover, they are often a contributing factor to car accidents. To address the problems associated with potholes, the locations and size of potholes must be determined quickly. Sophisticated road-maintenance strategies can be developed using a pothole database, which requires a specific pothole-detection system that can collect pothole information at low cost and over a wide area. However, pothole repair has long relied on manual detection efforts. Recent automatic detection systems, such as those based on vibrations or laser scanning, are insufficient to detect potholes correctly and inexpensively owing to the unstable detection of vibration-based methods and high costs of laser scanning-based methods. Thus, in this paper, we introduce a new pothole-detection system using a commercial black-box camera. The proposed system detects potholes over a wide area and at low cost. We have developed a novel pothole-detection algorithm specifically designed to work with the embedded computing environments of black-box cameras. Experimental results are presented with our proposed system, showing that potholes can be detected accurately in real-time.

Traffic Information Acquisition System with Ultrasonic Sensors in Wireless Sensor Networks

Existing systems for traffic information acquisition have high costs and low scalability owing to their characteristics such as large size, wired power supplies, and wired communication. To achieve low costs and high scalability, the use of traffic information acquisition systems based on wireless sensor networks (WSNs) has been suggested. However, WSN-based systems have important issues, such as low computing power, limited battery capacity, and high transmission delay. Existing studies on WSN-based acquisition systems have not considered all three of these problems together. Moreover, most studies have focused on theoretical problems rather than practical ones. Therefore, we propose a new system that considers all three limitations of WSN-based systems. In our experiments, we installed our system on real roads for an accurate evaluation. The results show that our system has a high detection accuracy, low power consumption, and low transmission delay.

Variable Speed Limit to Improve Safety near Traffic Congestion on Urban Freeways

Recently, the convergence of information technology with biotechnology, nano-technology, or other technologies has been creating a new paradigm. In the field of transportation, intelligent transport systems (ITSs)-a convergence of information technologies and transportation systems-have been studied. The VSL is one ITS technologies that aims to improve the safety and efficiency of transportation while controlling the speed limit according to traffic circumstances. Existing studies for VSL algorithms have considered only one station to control the traffic. However, it is not appropriate for an urban freeway to be installed with many stations. In this paper, a new VSL algorithm is proposed to enhance the effectiveness of VSL for multiple stations. It is based on the cooperation of stations and the real-time road information. The proposed algorithm consists of 4 steps: first is a ”searching bottleneck station,” second is a ”calculating a size of congestion,” third is a ”calculating the number of controlled stations,” fourth is a ”calculating VSL.” In our experiments, the microscopic traffic simulator VISSIM performed our modeling works. The results show that the proposed algorithm improves safety on roads with minimum additional travel time.

Variable speed limit to improve safety near traffic congestion on urban freeways

Recently, the convergence of information technology with biotechnology, nano-technology, or other technologies has been creating a new paradigm. In the field of transportation, intelligent transport systems (ITSs) - a convergence of information technologies and transportation systems - have been studied. The VSL is one ITS technologies that aims to improve the safety and efficiency of transportation while controlling the speed limit according to traffic circumstances. Existing studies for VSL algorithms have considered only one station to control the traffic. However, it is not appropriate for an urban freeway to be installed with many stations. In this paper, a new VSL algorithm is proposed to enhance the effectiveness of VSL for multiple stations. It is based on the cooperation of stations and the real-time road information. The proposed algorithm consists of 4 steps: first is a “searching bottleneck station,” second is a “calculating a size of congestion,” third is a “calculating the number of controlled stations,” fourth is a “calculating VSL.” In our experiments, the microscopic traffic simulator VISSIM performed our modeling works. The results show that the proposed algorithm improves safety on roads with minimum additional travel time.

Communication availability-based scheduling for fair data collection with path-constrained mobile sink in wireless sensor networks

To effectively transfer sensing data to a sink node, system designers should consider the characteristic of wireless sensor networks in the way of data transmission. In particular, sensor nodes surrounding a fixed sink node have routinely suffered from concentrated network traffic so that their battery energy is rapidly exhausted. The lifetime of wireless sensor networks decreases due to the rapid power consumption of these sensor nodes. To address the problem, a mobile sink model has recently been chosen for traffic load distribution among sensor nodes. However, since a mobile sink continuously changes its location in sensor networks, it has a time limitation to communicate with each sensor node and unstable signal strength from each sensor node. Therefore, fair and stable data collection policy between a mobile sink and sensor nodes is necessary in this circumstance. In this paper, we propose a new scheduling policy to support fair and stable data collection for a mobile sink in wireless sensor networks. The proposed policy performs data collection scheduling based on the communication availability of data transmission between sensor nodes and a mobile sink.

Cooperative Processing Model for Wireless Sensor Networks

Wireless sensor networks offer a distributed processing environment. Many sensor nodes are deployed in fields that have limited resources such as computing power, network bandwidth, and electric power. The sensor nodes construct their own networks automatically, and the collected data are sent to the sink node. In these traditional wireless sensor networks, network congestion due to packet flooding through the networks shortens the network life time. Clustering or in-network technologies help reduce packet flooding in the networks. Many studies have focused on saving energy in the sensor nodes because the limited available power leads to an important problem of extending the operation of sensor networks as long as possible. However, we focus on the execution time because clustering and local distributed processing already contribute to saving energy by local decision making. In this paper, we present a cooperative processing model based on the processing timeline. Our processing model includes validation of the processing, prediction of the total execution time, and determination of the optimal number of processing nodes for distributed processing in wireless sensor networks. The experiments demonstrate the accuracy of the proposed model, and a case study shows that our model can be used for the distributed application.

Personal multi-angle media broadcasting service system

In this paper, we propose a personal multi-angle media broadcasting service system. The proposed system accepts multiple input streams from the internet, files, and live broadcasts, and provides a personal media broadcast stream for clients. A personal media producer program and client programs of the proposed system are implemented on various platforms. The implemented system is experimented on a real sports event for a live broadcast of multi-angle media.

Pothole Detection Based on the Features of Intensity and Motion

Damage to road surfaces in the form of cracks and potholes increases over time and is compounded by poor maintenance systems. Potholes in particular can cause serious problems, including flat tires, damaged wheels, and car accidents. In a previous study, a pothole detection algorithm that used features of two-dimensional images to detect potholes was developed accurately. However, the algorithm yielded wrong detection in the case of similar objects, such as patches, stains, and shades. In particular, complicated shapes and random variations of similar objects led to misdetection. In this study, a pothole detection algorithm is proposed; it uses motion and the intensity of features to distinguish potholes accurately from similar objects. The motion feature is the source of primary information in the proposed algorithm and provides clear and noise-tolerant data for the extraction of potholes from the background region. The proposed algorithm consists of two steps of segmentation and decision and is much sim...