• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.1
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• pp.65-75
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• 2005

Measurement of network traffic have shown that the self-similarity is a ubiquitous phenomenon spanning across diverse network environments. In previous work, we have explored the feasibility of exploiting the long-range correlation structure in a self-similar traffic for the congestion control. We have advanced the framework of the multiple time scale congestion control and showed its effectiveness at enhancing performance for the rate-based feedback control. Our contribution is threefold. First, we define a modular extension of the TCP-a function called with a simple interface-that applies to various flavours of the TCP-e.g., Tahoe, Reno, Vegas and show that it significantly improves performance. Second, we show that a multiple time scale TCP endows the underlying feedback control with proactivity by bridging the uncertainty gap associated with reactive controls which is exacerbated by the high delay-bandwidth product in broadband wide area networks. Third, we investigate the influence of the three traffic control dimensions-tracking ability, connection duration, and fairness-on performance.

• The KIPS Transactions:PartC
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• v.18C no.1
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• pp.23-30
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• 2011

Recently internet protocol television (IPTV) service is becoming a typical emerging service enabled on broadband networks. Through the Internet which cannot support quality of service (QoS) beyond best-effort (BE) policy, how to manage and maintain its service quality is an important and essential issue for successful deployment and settlement of IPTV service. In particular, the current measurement scheme that mostly depends on specific equipments should be replaced with one that supports realtime and constant measurement achieved on a user's own will. Therefore, this paper proposes a scheme so-called 'user centric realtime measurement' of IPTV service. The developed software, which is installed in a set-top box (STB) at a user's premise, measures and reports the quality of IPTV service in realtime. In order to verify the performance and accuracy of the developed software, a number of tests are performed comparing to the measurement values from two major measurement equipments. The result of the tests shows that the measurement by the implemented software is significantly reliable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.75-80
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• 2008

Measurement of network traffic have shown that the self-similarity is a ubiquitous phenomenon spanning across diverse network environments. In previous work, we have explored the feasibility of exploiting the long-range correlation structure in a self-similar traffic for the congestion control. We have advanced the framework of the multiple time scale congestion control and showed its effectiveness at enhancing performance for the rate-based feedback control. Our contribution is threefold. First, we define a modular extension of the TCP-a function called with a simple interface-that applies to various flavours of the TCP-e.g., Tahoe, Reno, Vegas and show that it significantly improves performance. Second, we show that a multiple time scale TCP endows the underlying feedback control with proactivity by bridging the uncertainty gap associated with reactive controls which is exacerbated by the high delay-bandwidth product in broadband wide area networks. Third, we investigate the influence of the three traffic control dimensions-tracking ability, connection duration, and fairness-on performance.

• Journal of Advanced Navigation Technology
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• v.21 no.1
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• pp.113-118
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• 2017

As interest in mobile devices and networks has increased recently, voice over internet protocol (VoIP) service, which is a technology for transmitting voice data using an existing internet protocol (IP) network, has rapidly spread, Cheap voice call service has become possible. As the digital broadcasting service becomes popular, hybrid fiber coaxial (HFC) network technology, which uses broadband cable network through fusion of broadcasting and communication, utilizes existing communication system and network equipment to provide various new services such as interactive broadcasting service. Therefore, if UGS-AD is applied to VoCM and RTPS is applied to MTA in order to guarantee the quality of voice data in actual HFC Internet service network, it is possible to smoothly perform voice data transmission in narrow upstream band which is a problem in actual commercial HFC network We also proposed a method to improve VoIP service by improving QoS of voice data in HFC Internet service network.

• Journal of Advanced Navigation Technology
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• v.15 no.3
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• pp.412-418
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• 2011

In the airport, digital signage is used to provide the flight-related information for the passengers. Because the current digital signage is based on wired networking or storage medium, its use is limited in terms of the location and the usage of the digital signage. In order to overcome these limitation, we present a WiBro-based digital signage for the wireless broadband networking and the mobility of the digital signage. We perform comparative experiments with the WiBro-based digital signage and WLAN-based digital signage under various locations, datarate, advertisement contents. The experimental results showed that the WiBro-based digital signage is preferred when the mobility is required, while the WLAN-based digital signage has advantage in datarate.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.6
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• pp.823-829
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• 2011

This paper covers the service quality of packet-based voice service that is provided over a wireless broadband (WiBro) network. Using a measurement software that has been developed in the course of preparing a advanced service quality management scheme for the packet-based voice service over a wireless network[2][3], a huge scale of experiment is conducted to measure the real quality of the voice service. Based on our analysis of the measurement result, the service quality of the voice service is supposed to be quite good over WiBro networks. In addition, another experiment to investigate the effect of degradation of wireless transmission conditions on the service quality of the voice service shows the values of wireless service metris in which mean opinion score (MOS) starts to decrease.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.81-88
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• 2012

As the performance of the next-generation broadband wireless networks is dramatically enhanced, various services (i.e., education, Live video streaming, Live video conferencing, online games, etc.) have been provided to users through a smart mobile platform. Those services are usually provided by using the centralized communication server. However, since all multimedia traffic is exchanged through a communication server, it often has the scalability problem with regard to traffic management. Our main purpose is for group smart users to provide scalable live multimedia streaming service based on P2P network. To do this, we have designed an architecture of P2P-based service management for mobile group communication management and service management protocol. In order to verify the performance of the proposed scheme, we have mathematically analyzed the performance in terms of the average transmission delay and bandwid th utilization.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.1
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• pp.78-84
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• 2008

In this paper, the reconfigurable annular ring slot antenna with circular polarization diversity is proposed for SDMB(Satellite Digital Multimedia Broadcasting) system. The proposed antenna consists of a ring slot with four tuning stubs. Four PIN diodes are attached to switch circular polarization diversity. By switching the diodes ON or OFF, the proposed antenna can be operated either RHCP mode or LHCP mode. The experimental result shows that the proposed antenna has an impedance bandwidth(VSWR${\leq}$2) of 570MHz(2.47-3.04GHz) at LHCP mode, an impedance bandwidth (VSWR${\leq}$2) of 560MHz(2.45-3.01GHz) at RHCP mode, a maximum gai of 3.1dBi at RHCP mode, 4.76dBi at LHCP mode. The 3dB CP bandwidth of about 100MHz at both RHCP and LHCP mode is achieved at the center frequency 2.63GHz. The proposed antenna is suitable for application such as mobile satellite communications, WLAN(Wireless Local Area Networks), and broadband wireless communication systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.6
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• pp.516-525
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• 2009

This paper described the design and fabrication of broadband 4-way $90^{\circ}$ power divider which has a $90^{\circ}$ phase difference between output ports in 20${\sim}$100 MHz VHF-band. A 4-way $90^{\circ}$ power divider was designed using 4-way in-phase power divider which consisted of three 2-way in-phase power dividers and two second-order all pass filters which gives $90^{\circ}$ phase difference between output ports. The measured insertion loss was less then 6.6 dB, return loss and isolation were better than 19 dB, and phase error between $90^{\circ}$ phase difference outputs was less than ${\pm}$1$^{\circ}$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.685-688
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• 2008

A Next Generation Network (NGN) is a packet-based network able to provide services including Telecommunication Services and able to make use of multiple broadband, QoS-enabled transport technologies and in which service-related functions are independent from underlying transport-related technologies. It offers unrestricted access by users to different service providers. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users in this paper. we describe the trend of standardization activity related with open services environment capabilities which had been finally approved at September 2008 in ITU-T. ITU-T SG13 is responsible for studies relating to the architecture, evolution and convergence of next generation networks including frameworks and functional architectures, signalling requirements for NGN.