• Journal of Communications and Networks
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• v.7 no.2
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• pp.144-156
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• 2005

Video streaming over wireless networks is challenging due to node mobility and high channel error rate. In this paper, we propose a multi-source video streaming (MUVIS) system to support high quality video streaming service over IEEE 802.1l-based wireless networks. We begin by collocating a streaming proxy with the wireless access point to help leverage both the media server and peers in the WLAN. By tracking the peer mobility patterns and performing content discovery among peers, we construct a multi-source sender group and stream video using a rate-distortion optimized scheme. We formulate such a multi-source streaming scenario as a combinatorial packet scheduling problem and introduce the concept of asynchronous clocks to decouple the problem into three steps. First, we decide the membership of the multisource sender group based on the mobility pattern tracking, available video content in each peer and the bandwidth each peer allocates to the multi-source streaming service. Then, we select one sender from the sender group in each optimization instance using asynchronous clocks. Finally, we apply the point-to-point rate-distortion optimization framework between the selected sender-receiver pair. In addition, we implement two different caching strategies, simple caching simple fetching (SCSF) and distortion minimized smart caching (DMSC), in the proxy to investigate the effect of caching on the streaming performance. To design more realistic simulation models, we use the empirical results from corporate wireless networks to generate node mobility. Simulation results show that our proposed multi-source streaming scheme has better performance than the traditional server-only streaming scheme and that proxy-based caching can potentially improve video streaming performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3B
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• pp.462-473
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• 2010

The RFID system has the security problem of location tracking and user privacy. In order to solve this problem, the cryptographic access method using hash function is difficult to in real applications. Because there is a limit of computing and storage capacity of Tag, but the safety is proved. The lightweight authentication methods like HB and LMAP guarantee the high efficiency, but the safety is not enough to use. In this paper, we use the AES for RFID Authentication, and solve the problem of using fixed key with key change step by step. The symmetric keys of the tag and server are changed by the random number generated by tag, reader and server successively. This could prevent the key exposure. As a result, the output of the tag and reader always changes. These key changes could make it possible to prevent eavesdropping, replay attack, location tracking and spoofing.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.3
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• pp.60-67
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• 2011

Visible light communication system transmits data by controlling light emission of LED and receives data through photo detecter, which is considered as one of strong candidates of next generation wireless communication systems. The transmission capacity of visible light communication system depends on light intensity emitted from LED, sensitivity of PD, distance between transmitter and receiver, angle of incidence at the receiver. In particular, the receiver's vertical and horizontal movement changes distance between transmitter and receiver and angle of incidence, which may degrades transmission capacity of system. In this paper, we propose an estimation algorithm of receiver's position and angle based on tracking of received light intensity for indoor visible light communication systems. The performance evaluation of proposed algorithm confirms that the estimation algorithm of receiver's position and angle is quite important for visible light communication system to improve its transmission capacity.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.6
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• pp.24-34
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• 2007

Application systems that easy to access a information have been developed by IT growth and a human life variation. In this paper, we propose a application system to register a 3D footwear model using a monocular camera. In General, a human motion analysis research to body movement. However, this system research a new method to use a foot movement. This paper present a system process and show experiment results. For projection to 2D foot plane from 3D shoe model data, we construct processes that a foot tracking, a projection expression and pose estimation process. This system divide from a 2D image analysis and a 3D pose estimation. First, for a foot tracking, we propose a method that find fixing point by a foot characteristic, and propose a geometric expression to relate 2D coordinate and 3D coordinate to use a monocular camera without a camera calibration. We make a application system, and measure distance error. Then, we confirmed a registration very well.

• Journal of Power Electronics
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• v.11 no.2
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• pp.194-201
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• 2011

The air flow supplied to a fuel cell system is one of the most significant factors in determining fuel efficiency. The conventional method of controlling the air flow is to fix the oxygen supply at an estimated constant rate for optimal efficiency. However, the actual optimal point can deviated from the pre-set value due to temperature, load conditions and so on. In this paper, the maximum efficiency point tracking (MEPT) algorithm is proposed for finding the optimal air supply rate in real time to maximize the net-power generation of fuel cell systems. The fixed step MEPT algorithm has slow dynamics, thus it affects the overall efficiency. As a result, the variable step MEPT algorithm is proposed to compensate for this problem instead of a fixed one. The complete small signal model of a PEM Fuel cell system is developed to perform a stability analysis and to present a design guideline. For a design example, a 1kW PEM fuel cell system with a DSP 56F807 (Motorola Inc) was built and tested using the proposed MEPT algorithm. This control algorithm is very effective for a soft current change load like a grid connected system or a hybrid electric vehicle system with a secondary energy source.

• The KIPS Transactions:PartD
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• v.8D no.5
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• pp.613-622
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• 2001

As logistic environment of digital resources is rapidly changing, protection of the intellectual property for digital resources has been recognized as one of important issues. Digital Rights Management (DRM) has taken much interests from ISP, authors and publishers of digital content as an integrated approach to create a reliable environment for access and the use of digital resource. In this paper we proposed a dynamic digital rights management system based on adaptive agent theory (ARPA : Adaptive Resource Protection Agent) to address problems facing contemporary DRM approaches : static rights management problem solving and strengthened monitoring/tracking system. We introduced a dynamic mission control scheme to realize dynamic digital rights management. We incorporated adaptive agent theory to implement on-and off-line tracking and protection. Through the implementation of protype system, the process, the process dynamic digital rights protection will be demonstrated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1053-1058
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• 2006

In this paper, We proposed a efficient OSA(Optical Sub-Assembly) packaging method in use 1.31/1.49um bi-directional hybrid-integrated PLC chip for low-cost OSA in optical access network system applications as GE-PON in FTTH. Fabricated OSA with passive optical fiber alignment and nonhermetic plastic package method and measured optical coupling efficiency and electric-optical characteristics. Its performance is feasible to satisfy the GE-PON ONU specifications with the results as less than 0.5dB coupling losses within 40um alignment of z-axis and less than -24dBm sensitivity. It also has good temperature characteristics to sustain optical output power more than 1.5mW and 10dB extinction ratio, less than 0.3dB tracking error.

• Journal of the Korea Society of Computer and Information
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• v.26 no.12
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• pp.77-84
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• 2021

In this paper, we propose a system that uses image data and beacon data to classify authorized and unauthorized perosn who are allowed to enter a group facility. The image data collected through the IP camera uses YOLOv4 to extract a person object, and collects beacon signal data (UUID, RSSI) through an application to compose a fingerprinting-based radio map. Beacon extracts user location data after CNN-LSTM-based learning in order to improve location accuracy by supplementing signal instability. As a result of this paper, it showed an accuracy of 93.47%. In the future, it can be expected to fusion with the access authentication process such as QR code that has been used due to the COVID-19, track people who haven't through the authentication process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.180-186
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• 2017

In this paper we propose a traffic aware Demand Wakeup MAC(TADW-MAC) protocol, in which low data delay and high throughput can be achieved, for wireless sensor networks. With the TADW-MAC protocol, the problem of the DW-MAC protocol, which schedules only one packet to deliver during the Sleep period in a multi-hop transmission is resolved. DW-MAC is not adequate for the applications such as object tracking and fire detection, in which busty data should be transmitted in a limited time when an event occurs [6-8]. When an event occurs, duty cycle can be adjusted in the TADW-MAC protocol to get less energy consumption and low latency. The duty cycle mechanism has been widely used to save energy consumption of sensor node due to idle listening in wireless sensor networks. But additional delay in packet transmission may be increased in the mechanism. Our simulation results show that TADW-MAC outperforms RMAC and DW-MAC in terms of energy efficiency while achieving low latency.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.5
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• pp.927-934
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• 2023

With the recent growth of the companion animal market, various social issues related to companion animals have also come to the forefront. Notable problems include incidents of dog bites, the challenge of managing abandoned companion animals, euthanasia, animal abuse, and more. As potential solutions, a variety of training programs such as companion animal-focused broadcasts and educational apps are being offered. However, these options might not be very effective for novice caretakers who are uncertain about what to prioritize in training. While training apps that are relatively easy to access have been widely distributed, apps that allow users to directly engage in training and learn through hands-on experience are still insufficient. In this paper, we propose a more efficient AR-based mobile app for companion animal training, utilizing the Unity engine. The results of usability evaluations indicated increased user engagement due to the inclusion of elements that were previously absent. Moreover, training immersion was enhanced, leading to improved learning outcomes. With further development and subsequent verification and production, we anticipate that this app could become an effective training tool for novice caretakers planning to adopt companion animals, as well as for experienced caretakers.