• Journal of Information Processing Systems
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• v.6 no.4
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• pp.575-596
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• 2010

Video-on-Demand services are increasing rapidly nowadays. The load on servers can be very high, even exceeding their capacity. For popular contents, we can use a Periodic Broadcast (PB) strategy using multicast to serve all clients. Recent development of PB uses multiple channels broadcasting for segments of movies in certain patterns, so that users only need to wait for a small segment to start the service. However, users need higher download capacity to download multiple segments at a time. In order to compensate for this, a proxy server can help to reduce download bandwidth requirements by holding some segments for a certain time. This research will focus on more recent PB schemes that couldn't be covered by previous Proxy-Assisted Periodic Broadcast strategies.

• Journal of Communications and Networks
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• v.18 no.2
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• pp.238-245
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• 2016

A sequence number checking technique is proposed to improve the performance of TCP connections in mobile ad hoc networks. While a TCP connection is initialized, a routing protocol takes the responsibility for checking the hop count between a source and destination pair. If the hop count is greater than a predefined value, the routing protocol decides to use a proxy node. The responsibility of a proxy node is to check the correctness of data packets and inform the missing packets by sending an acknowledgement from a proxy node to the source node. By doing so, the source node is able to retransmit any missing packet in advance without waiting until an end-to-end acknowledgement is received from the destination. Simulation results show that the proposed mechanism is able to increase throughput up to 55% in static network and decrease routing overhead up to 95%in mobile network.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.11a
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• pp.1300-1302
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• 2008

최근 위성을 통한 위치정보서비스를 이용하여 응용서비스를 제공하려는 움직임이 늘고 있다. 이처럼 위치기반서비스(LBS: Location Based Service)를 제공하려는 현재의 추세를 볼 때에 단말에 위치기반을 위한 기능은 필수적인 추가사항이며 이를 위한 단말의 부담은 고려해야 할 사항이다. 그러나 A-GPS(Assisted GPS) 기술 중 A-GPS Server(Assistance GPS Server)을 이용함으로써 단말에 부담을 적게 하면서 위치기반의 서비스를 제공받을 수 있고, 핸드오버 지연을 효과적으로 줄일 수 있다면 1 석 2 조의 효과를 얻을 수 있게 된다. 본 논문에서는 기존 PMIPv6(Proxy Mobile IPv6) 메커니즘에 A-GPS Server 를 두어서 효과적인 핸드오버 수행과정을 거치고, 위치기반서비스(LBS)를 제공하는 메커니즘을 제안한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.1-10
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• 2012

Mobility and quality of service (QoS) are becoming the more important issues in wireless communications. The traditional Internet service is expanding into new access media and applications. Since wireless communication services are accompanied by frequent handovers at remote sites, scalable and fast handover has become a prerequisite for ubiquitous communication. In this paper, the differentiated service (Diffserv) model is deployed in heterogeneous proxy mobile IPv6 (PMIPv6) networks to satisfy the QoS guaranteed service and fast handover requirements. The operational procedures for QoS guaranteed global roaming are presented. In addition, QoS management and handover cost evaluation schemes based on a mobile host's movement scope are proposed. This paper analyzes the reduction in handover delay in a network-based localized mobility management framework. We propose and analyze a PMIPv6 optimized with a global mobile access gateway (G-MAG), which is a network-based entity, to further improve the handover performance in terms of handover delay while maintaining minimal signaling overhead in the air interface among converged heterogeneous wireless networks. The handover signaling procedures with host-based MIPv6 are compared with network-based proxy MIPv6 (PMIPv6) and fast PMIPv6 assisted by G-MAG to show how much handover delay reduction can be achieved. Analytical results show that the handover delay is significantly reduced.