• Journal of KIISE:Information Networking
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• v.33 no.5
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• pp.380-394
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• 2006

Traditional Internet services provide the same level of qualify to all users without considering about their application's QoS (quality of service) requirements. Because the wireless and Internet technologies are evolving rapidly, the powerful mobile devices are more widely used. Therefore, the new applications such as DMB (digital multimedia broadcasting), VoD (video on demand), telemedicine, and etc. demand appropriate QoS and host mobility. To satisfy free mobility and QoS, we deploy Diffserv (differentiated services) model to the mobile IPv6 networks. We propose the operational procedures and cost analyzing models for providing an MN's mobility and QoS. Also its performance is presented by cost analyzing and the future works are described.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.177-179
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• 2009

It is increased that need of broadband multimedia service to make useful environment for user and to support the operation of railway system. So study of integrated data transmission in a subway and railway is activated. The research deals with pass loss characteristics of 18GHz microwave that is assigned frequency of integrated data transmission in a subway and railway. It is used sample integrated transmission system in subway and railway of KRRI(korea railroad research Institute) at the tunnel and road. Specification of test sample system is blow. It use OFDM modulation, Wireless frequency is 18GHz and 19GHz, Maximum output power is 20dBm, Receive sensitivity is -90dBm. The pass loss exponent and standard variation of road and tunnel is analyzed.

• The KIPS Transactions:PartC
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• v.12C no.2 s.98
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• pp.217-222
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• 2005

The IEEE 802.11 based wireless local area networks are candidates to lead the broadband connectivity in the home and office scenarios. Recently IEEE proposed the 802.11e as a new standard to provide appropriate Quality of Services to a plethora of emerging real-time multimedia and high demanding applications such as high definition movie and audio distribution, video-conference and voice over IP. This paper studies the IEEE 802.11e/IEEE 802.11b interactions focusing on potential unfairness problems that might appear in networks with heterogeneous wireless LAN technologies as well as in the IEEE 802.11e deployment phase.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.360-363
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• 2008

현재 통신 시장의 상황은 유무선 통신서비스 시장의 포화, 이동통신 시장의 기존 유선전화 규모 초과, 그리고 유선통신의 서비스 사업자의 영역 확대 도모 등을 특징으로 한다. 유무선 통합 (Fixed Mobile Convergence, FMC) 서비스는 유선통신 사업자를 중심으로 한 비즈니스 모델로 사용자에게 유무선 통신망 종류에 상관없이 일관되고 끊김없는 서비스를 제공하는 것을 목표로 한다. 이동통신망까지 확대하여 고객 기반을 유지하고자 하는 유선사업자들은 FMC 서비스 중 하나의 방안으로 IMS (IP Multimedia Subsystems) 기반의 VCC(Voice Call Continuity) 기능에 주목하고 있다. VCC AS(Application Server)는 이종망 (WiFi-CDMA)간 Seamless 핸드오버기능을 수행하므로, WiFi 와 CDMA를 지원할 수 있는 듀얼단말을 이용하여 사용자가 WiFi 서비스 지역과 CDMA 서비스 지역간 이동시에도 Seamless 한 음성서비스를 제공한다. 이에 본 논문은 IMS/VCC 기반으로 음성 seamless 핸드오버 적용 사례(시범서비스)를 중심으로 유무선 통신사업자 상호 Win-Win을 추구할 수 있는 LG데이콤 특화 VCC 모델을 제시한다. 그리고 LG데이콤이 추구하는 차세대 서비스인 사용자 context 기반의 개인화된 서비스 제공을 위한 IMS 기반 통합 프로파일/인증/과금 연구 동향에 대해 간략히 소개한다.

• Journal of the Institute of Convergence Signal Processing
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• v.12 no.2
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• pp.102-106
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• 2011

The transfer capability of HFC (Hybrid Fiber Coax) network is superior to xDSL. HFC network, however, is not suitable for transferring high quality video due to cable model interfaces. For the services of high quality IPIV or VOD, the extra exclusive downstream transfer system is required without upgrading pre-equipped cable modem and service capability. This paper is aimed to develop the extra exclusive downstream transfer system not changing existing cable modem system but providing same quality of services. This system is composed of the extra exclusive downstream IP-cable sender and modem. This sender and modem have 30 Mbps transfer capability and HDTV stream can be served in the Cable TV network using 21 Mbps HDTV transport stream.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.04a
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• pp.1188-1191
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• 2011

IPTV 방송에서 인터넷 기반 멀티캐스트는 일대다 또는 다대다 통신을 위한 차세대 중요한 서비스로 주목 받고 있다. 멀티캐스트는 네트워크 또는 애플리케이션 레벨에서 서비스할 수 있다. IP 멀티캐스트는 소스노드에서 라우터로 데이터그램을 보내면 라우터가 이를 복제하여 수신노드들에게 전달해 주는 네트워크레벨 서비스로 네트워크 자원을 효율적 사용할 수 있다. 그러나 네트워크에 IP 멀티캐스트 라우터가 설치되어야 하는 등 여러 문제로 인해 널리 사용되지 못하고 있다. 따라서 대안으로 애플리케이션 레벨에서의 오버레이 멀티캐스트가 주목 받고 있다. 오버레이 멀티캐스트는 종단호스트가 라우터처럼 동작하는 것으로 비록 IP 멀티캐스트에 비해서 링크 사용율과 지연 값이 높아질 수 있지만, IP 멀티캐스트의 현실적인 적용의 어려움을 해결할 수 있는 장점을 가지고 있다. 본 논문에서는 IP 멀티캐스트가 제공되지 않는 네트워크에서 효율적인 SVC(Scalable Video Coding) 멀티미디어 방송서비스와 SSENS(SVC Stream Exchange Network Server) 라우팅을 위한 MST(Minimum Spanning tree)를 목적으로 하는 오버레이 멀티캐스트 트리를 구현하는 알고리즘을 설계한다. 제안된 알고리즘의 성능 분석을 위해 시뮬레이션을 통해 패킷 손실 측면에서 Prim 알고리즘에 비해 평균 패킷 손실율이 40% 가까이 향상됨을 증명하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.17-27
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• 2007

The enhanced distributed channel access (EDCA) of IEEE 802.11e has been standardized for supporting Quality of Service (QoS) in wireless LANs. In the EDCA, support of QoS can be achieved statistically by reducing the probability of medium access for lower priority traffics. In other words, it provides statistical channel access rather than deterministically prioritized access to high priority traffic. Therefore, lower priority traffics affect the performance of higher priority traffics. Consequently, at the high loads, the EDCA does not guarantee the QoS of multimedia applications such as voice and video even though it provides higher priority. In this paper, we propose a simple and effective scheme, called deterministic priority channel access (DPCA), for improving the QoS performance of the EDCA mechanism. In order to provide guaranteed priority channel access to multimedia applications, the proposed scheme uses a busy tone for limiting the transmissions of lower priority traffics when higher priority traffic has data packets to send. Performance of the proposed scheme is investigated by numerical analysis and simulation. Our results show that the proposed scheme outperforms the EDCA in terms of throughput, delay, jitter, and drop under a wide range of contention levels.

• Journal of Broadcast Engineering
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• v.27 no.1
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• pp.80-90
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• 2022

Currently, the domestic early warning system is issued differently for each disaster, and is operated independently by relevant organizations from central government to local governments. Representative domestic disaster warning systems include disaster broadcasting using CBS(Cell Broadcasting Service) and DMB(Digital Multimedia Broadcasting) Automatic Emergency Alert Service, DITS(Disaster Information Transform System) transmitted and displayed on TV screens, automatic response system, automated rainfall warning system, and disaster message board. However, due to the difference in the method of issuing each emergency alert at the site of an emergency disaster, the alerts are issued at different times for each media, and the delivered content is also not integrated. If these systems are integrated, it is expected that damage to people's property and lives will be minimized by sharing and integrated management of disaster information such as voice, video, and data to comprehensively judge and make decisions about disaster situations. Therefore, in this study, we present a plan for the integration of the disaster warning system along with the analysis of the operation status of the domestic early warning system.

• The Journal of the Acoustical Society of Korea
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• v.21 no.6
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• pp.566-575
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• 2002

Low-titrate audio coding enables a number of Internet and mobile multimedia streaming service more efficiently. For the help of next-generation mobile telephone technologies and digital audio/video compression algorithm, we can enjoy the real-time multimedia contents on our mobile devices (cellular phone, PDA notebook, etc). But the limited available bandwidth of mobile communication network prohibits transmitting high-qualify AV contents. In addition, most bandwidth is assigned to transmit video contents. In this paper, we design a novel and simple method for reproducing high frequency components. The spectrum of high frequency components, which are lost by down-sampling, are modeled by the energy rate with low frequency band in Bark scale, and these values are multiplexed with conventional coded bitstream. At the decoder side, the high frequency components are reconstructed by duplicating with low frequency band spectrum at a rate of decoded energy rates. As a result of segmental SNR and MOS test, we convinced that our proposed method enhances the subjective sound quality only 10%∼20% additional bits. In addition, this proposed method can apply all kinds of frequency domain audio compression algorithms, such as MPEG-1/2, AAC, AC-3, and etc.

• Journal of Korea Multimedia Society
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• v.7 no.8
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• pp.1066-1077
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• 2004

Dramatic increase in the number of Internet users want highly qualified service of continuous media contents on the web. To solve these problems, we present two network caching schemes(PPC, PPCwP) which consider the characteristics of continuous media objects and user access pattern in this paper. While there are plenty of reasons to create rich media contents, delivering this high bandwidth contents over the internet presents problems such as server overload, network congestion and client-perceived latency. PPC scheme periodically calculates the popularity of objects based on the playback quantity and determines the optimal size of the initial fraction of a continuous media object to be cached in proportion to the calculated popularity. PPCwP scheme calculates the expected popularity using the series information and prefetches the expected initial fraction of newly created continuous media objects. Under the PPCwP scheme, the initial client-perceived latency and the data transferred from a remote server can be reduced and limited cache storage space can be utilized efficiently. Trace-driven simulation have been performed to evaluate the presented caching schemes using the log-files of iMBC. Through these simulations, PPC and PPCwP outperforms LRU and LFU in terms of BHR and DSR.