• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.475-483
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• 2007

Recently, consumers demand high-quality wireless multimedia services via terrestrial and satellite network. And the interest for new services to sustain its successful commercial deployment grows tremendously. So, the MIMO schemes, such as STCs, MRC, has been used for realizing high reliability. However, MIMO schemes has some limitations. MIMO scheme needs more size, cost, and hardware complexity to employ additional antennas. Moreover, sufficient spaces between antennas are required to guarantee the independence of each channel and the devices which use multiple antennas should be enlarged. A cooperative transmission technique which is detect and forward type applying virtual MIMO with STBC matrix in DVB-RCT(Digital Video Broadcasting with Return Channel via Terrestrial) system based on OFDMA is also proposed.

• International Journal of Advanced Culture Technology
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• v.2 no.1
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• pp.1-13
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• 2014

In next-generation wireless networks, provisioning of IP-based network architecture and seamless transmission services are very important issues for mobile nodes. For this reason, a mobility management mechanism to support global roaming is highly regarded. These technologies bring a broader life by using a global roaming account through the connection of multiple devices or technology to mobile users; they also provide real-time multimedia services. This paper presents a comprehensive performance analysis of fast handover for hierarchical mobile IPv6 (F-HMIPv6), hierarchical mobile IPv6 (HMIPv6), Proxy Mobile IPv6 (PMIPv6), and fast Proxy Mobile IPv6 (FPMIPv6) using the fluid-flow model and random-walk model. As a result, the location update cost of the PMIPv6 and FPMIPv6 is better than that of HMIPv6 and F-HMIPv6. These results suggest that the network-based mobility management technology is superior to the hierarchical mobility management technology in the mobility environment.

• 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 Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.83-86
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• 2003

With the opening of digital broadcast services and development of wire/wireless Internet, the current multimedia broadcasting is provided for has various services. The user will be provided lots of various content through the various channel and media. Content provider and consumer want the various service using content with the better quality which is fit to user preference. For transmitting this content in the limited transmission channel capacity, it needs to transmit the highly compressed content which user wants. The content of 3D mesh model-based on MPEG-4 enables the various content service that provides the lower capacity and the better quality, and Targeting service enables just provide the contents that user more wants and likes. The adaption of Java application program and 3D program can provide the content service utilizing 3D mesh model, so content provider and consumer can share the more information about the content. This paper has presented the study on the targeting service using compression of 3D mesh model-based on MPEG-4 and the adaptation of Java application program using it

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.8A
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• pp.1428-1436
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• 2001

본 논문에서는 무선 이동 ATM 네트워크에서 무선채널 상태를 고려하면서 가상목적지와 가상소스를 이용한 효율적인 ABR트래픽 흐름제거 기법을 제안한다. ABR서비스는 높은 우선순위를 갖는 실시간 서비스에 의해 사용되지 않는 유휴대역폭을 효율적으로 사용하는 서비스로, 셀손실에 특히 민감하다. ABR서비스는 대역폭의 효율적인 활용으로 기존ATM네트워크에서 널리 사용되고 있으며, 무선 이동ATM네트워크에서도 이러한 ABR서비스의 제공이 중요하다고 하겠다. 기존 ATM네트워크에서는 효율적인 ABR서비스를 위한 흐름제어기법으로서 RM(Resource Management)셀의 피드백을 이용한 전송율기반 폭주제어 기법을 사용하고 있으나, 이 방식을 무선네트워크에 그대로 적용했을 경우, 심각한 대역폭의 낭비를 가져올 수 있다. 따라서 제안된 기법은 무선 이동네트워크에서 RM셀의 전송을 억제하고 ATM스위치에 의해 MT(Movile terminal)의 ACR을 결정하게 하여 기지국을 통해 단말기로 전송하도록 하였다. ABR트래픽은 MT에서 고정호스트로 전송된다고 가정하고 시뮬레이션을 수행하여, 그 성능을 분석하였다. 성능분석 결과, 제안된 기법은 무선네트워크의 대역폭을 낭비하지 않으면서 링크의 혼잡도를 최소화하여 채널상태에 따라 효율적으로 전송율을 조절할 수 있음을 확인하였다.

• Journal of information and communication convergence engineering
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• v.14 no.1
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• pp.21-25
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• 2016

N-screen is a promising technology to improve support for multimedia multicasting, content sharing, content mobility, media scalability, and seamless mobility. In this paper, the WiMedia distributed-MAC (D-MAC) protocol is adopted for development of a seamless N-screen wireless service. Furthermore, to provide a multi-hop, one source multi-use N-screen service through point to point streaming in a seamless D-MAC protocol, a dynamic multi-frame transmission technology is proposed. In this technology, a dynamic time slot allocation scheme and a multi-hop resource reservation scheme are combined. In the proposed dynamic time slot allocation scheme, two thresholds, a hard threshold and a soft threshold, are included to satisfy the power consumption and delay requirements. A multi-frame DRP reservation scheme is proposed to minimize end-to-end delay during the multi-hop transmissions between N-screen devices. The proposed dynamic multi-frame transmission scheme enhances N-screen performance in terms of the multi-hop link establishment success rate and link establishment time compared to the conventional WiMedia D-MAC system.

• 한국HCI학회:학술대회논문집
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• 2008.02a
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• pp.262-268
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• 2008

Recently, as the demand for multimedia services based on the wireless technologies and mobile devices increases, Full-touch screen mobile devices adopting touch screen keyboards are emerging to cope with the limited display size and take advantage of the flexibility in the design of user interfaces. However, the text entry task, which is one of the main features of the mobile devices, decreases the competitive advantages of the touch screen keyboards over the physical keyboards or keypads due to the lack of physical feedbacks and the frequent occurrence of mistyping. This study aims to introduce a novel text entry method named Fuzzy Touch and compare this method with the conventional text entry method on a touch screen keyboard in terms of the performance (time, number of touch) and the subjective ratings (ease of use, overall preference).

• Proceedings of the Korea Contents Association Conference
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• 2003.05a
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• pp.245-250
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• 2003

Of all wireless technologies for personal communications, CDMA(Code Devision Multiple Access) offers the best combination of good signal quality, high security and system reliability. CDMA2000 provides Internet and internet services for variable multimedia aplications. However, good educational CDMA web contents, which focus on the easy understability and good readability, are rare dute to the difficulties and the broad range of CDMA technologies. This content is developed based upon the following two aspects. First, a basic CDMA communication theoy, which contains much color figures and animation, is introduced combing the experimental results and corresponding explanations utilizing the information obtained by the TIMS CDMA equitments. It can improve the understabiliy virtual experience of the site visitors interested in the CDMA. Secondly, the recent CDMA coverage prediction and engineering technology is introduced using the RF plan tool C24 combined for the CDMA engineers

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.769-771
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• 2001

본 논문은 인터넷 전화 (Internet Telephony)의 대표적 프로토콜인 SIP에 이동성을 제공하기 위한 방안에 대한 연구이다. 이를 위해 가장 쉽고 계층화된 방법은 IP (네트워크) 계층에서 이동성을 지원하는 mobile IP를 사용하여 상위 계층에 투명한 핸드오프를 제공하도록 하는 것이다. 그러나 기존 연구들은 mobile IP가 아직 보편화되지 않았고 삼각 라우팅 (triangular routing) 지연 및 캡슐화 오버헤드와 같은 단점을 이유로 SIP 자체를 확장하는 방법을 제안해 왔다. 그러나 이 방법은 향후 all IP 추세와 함께 mobile IP가 지원되면서 그 의미를 상실하게 될 것이고 어떤 방법으로도 조화를 이룰 필요성이 대두된다. 또한 SIP 자체의 확장을 통한 이동성 지원은 해당 응용에만 적용되는 것으로 인터넷의 근본적 이동성 제공과는 독립한다. 우리는 본 연구를 통해 mobile IP 기반의 SIP 환경을 구축하고 다양한 실험을 통해 그 가능성을 보인다. 또한 mobile IP 망의 효율적인 관리에 적합한 패킷 당 오디오 프레임 수를 제시한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.3
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• pp.459-464
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• 2001

We propose a transmit beamforming algerian for array antenna in FDD (Frequency Division Duplex) environments. The proposed method estimates the directions and spectra of the users, and constructs the spatial covariance matrix of the interferences at the downlink frequency. The weights are computed by that covariance matrix and desired user's direction vector Simulations are performed under Rayleigh fading environments. The proposed method don't need the data feedback, has the enhanced performance in BER (Bit Error Rate).