• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.717-724
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• 2005

In this paper, we Propose an efficient scheduler well suited for the next-generation wireless networks that can support multimedia traffic having various requirements. The scheduler is designed to provide each of multimedia classes with differentiated services. In particular, the scheduler is intended to maximize throughput and minimize packet loss ratio. To apply the scheduler, we suppose that the wireless network is based on TDD/CDMA system The scheduler assigns a packet in a dedicated uplink-slot to the user within a frame to operate scheduling of packets transmitted by the users belonging to the specific class in an efficient manner. Such a manner also enables the scheduler to meet different QoS requirements. The paper also includes performance comparison with other schemes and analysis of the proposed scheduling algorithm by using simulation. We also analyze the proposed scheme by using simulation. The simulation compares the proposed scheduling algerian with previously proposed schemes in terms of the performance.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.5
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• pp.1153-1164
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• 2012

In this paper, we propose an efficient car management system based on object-oriented modeling using car number recognition and smart phone. The proposed system perceives car number of repair vehicle after recognizing the licence plate using an IP camera in real time. And then, existing repair history information of the recognized car is be displayed in DID. In addition, maintenance process is shooting video while auto maintenance mechanic repairs car through IP-camera. That will be provide customer car identification and repairs history management function by sending key frames extracted from recorded video automatically. We provide user graphic interface based on web and mobile for your convenience. The module design of the proposed system apply software design modeling based on granular object-oriented considering reuse and extensibility after implementation. Car repairs center and maintenance companies can improve business efficiency, as well as the requested vehicle repair can increase customer confidence.

• The Journal of the Korea institute of electronic communication sciences
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• v.2 no.1
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• pp.10-18
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• 2007

In this paper, we extend the multiple time scale control framework to window-based congestion control, in particular, TCP. This is performed by interfacing TCP with a large time scale control module which adjusts the aggressiveness of bandwidth consumption behavior exhibited by TCP as a function of "large time scale" network state. i.e., conformation that exceeds the horizon of the feedback loop as determined by RTT. Performance evaluation of multiple time scale TCP is facilitated by a simulation bench-mark environment which is based on physical modeling of self-similar traffic. If source traffic is not extended exceeding, when RTT is 450ms, in self similar burst environment, performance gain of TCP-SSC is up to 45% for ${\alpha}$=1.05. However, its is acquired only 20% performance gain for ${\alpha}$=1.95 relatively. Therefore we showed that by TCP-MTS at large time scale into a rate-based feedback congestion control, we are able to improve two times performance significantly.

• Journal of Advanced Navigation Technology
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• v.11 no.1
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• pp.118-126
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• 2007

An ad hoc network is a system of wireless mobile nodes that dynamically self-organize in arbitrary and temporary network topologies allowing people and devices to internetwork without any preexisting communication infrastructure. Although ad hoc network is attractive solution, there are still some major flaws that prevent commercial growth. Security is one of these main barriers; ad hoc networks are known to be particularly vulnerable to security attack. It is difficult to establish a centralized key distribution center and a trusted certification authority to provide cryptographic keys and digital certificates to nodes. To prevent attacks in ad hoc routing protocols, many algorithms have been used. In this paper, we have depicted a secure framework for multipath routing in wireless multihop network, which is comprehensive solution for secure data forwarding in wireless multihop networks. With the simulation results, the proposed scheme is compared with existing source routing scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2315-2320
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• 2006

A real-time frame-layer rate control algorithm with a token bucket traffic shaper is proposed for low bit rate video coding. The proposed rate control method uses a non-iterative optimization method for low computational complexity, and performs bit allocation at the frame level to minimize the average distortion over an entire sequence as well as variations in distortion between frames. In order to reduce the quality fluctuation, we use a sliding window scheme which does not require the pre-analysis process. Therefore, the proposed algorithm does not produce time delay from encoding, and is suitable for real-time low-complexity video encoder. Experimental results indicate that the proposed control method provides better visual and PSNR performances than the existing rate control method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2215-2222
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• 2010

A Wireless Access for Vehicular Environment (WAVE) system based on Orthogonal Frequency Division Multiplexing (OFDM) is made for vehicle to vehicle wireless communications. The physical layer standard of the WAVE system is very similar to that of the IEEE802.11a wireless local area network (WLAN). Therefore, the performance of the WAVE system is degraded by continual channel variation in the WAVE multipath fading channels after starting initial channel estimation. In this paper, we research the performance improvement of equalization in 64 Quadrature Amplitude Modulation (QAM) transmission in WAVE environment. The proposed algorithms use the training sequence and the midamble sequence which is used for fast channel variation such as WAVE environments. Additionally, various interpolation methods are also used for the channel tracking.

• The KIPS Transactions:PartC
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• v.12C no.4 s.100
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• pp.589-596
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• 2005

The objective of this paper lies in the design and implementation of a home gateway supporting live video streaming which flows from the Non-SIP video camera in home to the mobile SIP device outside. We developed the home gateway on the OSGi framework and employed the RTC technology which embeds an SIP stack so that the multimedia session can be established from the home device to the mobile user outside. And also we developed an RTC bundle to manage the session and a virtual capture device driver to read the video stream from the Non-SIP video camera in the home network, and installed them on the home gateway. Finally, we constructed the experimental environment that has the windows messenger as the SIP mobile device and an AXIS 2100 UPnP video camera as a video source, and then tested if the session establishment to the mobile user from the camera and live video streaming work well between them.

• The KIPS Transactions:PartD
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• v.8D no.2
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• pp.181-192
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• 2001

XML/EDI is different from traditional EDI because it offers the framework necessary for electronic commerce and extends the scope of the traditional EDI which focuses on data transfer. Since existing EDI services are moved to Internet platform and again to Web platform, users can use EDI in the integrated environment without inconvenience of using different EDI softwares, which have their own configurations. This paper describes the overall design and implementation of a Web-based XML/EDI system that is a core component for the electronic commerce. The constructed XML/EDI system in this paper is comprised of document generation module, document storage module, document search module, document management module, template document management module and e-mail transmission module. Requirements and design goal of XML/EDI system are introduced, detailed functionalities of modules and design facts are described and execution and execution procedures of the implemented system are explained.

• KIISE Transactions on Computing Practices
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• v.23 no.9
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• pp.550-556
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• 2017

Due to the rapid growth and development of Internet of Things (IoT), various devices are now accessible and controllable anytime from anywhere. However, the current IoT system requires a series of complex steps (e.g., launch an application, choose a space and thing, control the thing, etc.) to control the IoT devices; therefore, IoT suffers from a lack of efficient and intuitive methods of interacting with users. To address this problem, we propose a novel IoT control framework based on IoT tags and social messages. The proposed system provides an intuitive and efficient way to control the device based on the device ownership: 1) users can easily control the device by IoT tagging, or 2) users can send an IoT social message to the device owner to request control of the tagged device. Through the development of the prototype system, we show that the proposed system provides an efficient and intuitive way to control devices in the IoT environment.

• Journal of Advanced Navigation Technology
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• v.6 no.3
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• pp.203-210
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• 2002

In this paper, the BER performance of IEEE 802.11a OFDM WLAN system is obtained by simulation and it is shown that the proposed modified channel estimation algorithm improves the channel estimation performance of the system. The wireless channel used in channel simulation includes AWGN and delay spread channel implemented by TDL model. At first, the performance of OFDM WLAN system according to data rate and coding rate defined in standard is evaluated in AWGN channel. Then, imperfect channel estimation in indoor wireless channel is considered. After the performance of conventional channel estimation scheme using only two long training symbols is evaluated, and that of proposed modified channel estimation scheme using additional 8 short training symbol is compared with it. From the simulation results, it is shown that modified channel estimation scheme provides reduced channel estimation error and improves the channel estimation performance due to noise averaging effect with the same preamble format as defined in specification.