Miyoun Yoon

Placement Algorithm of Web Server Replicas

Recently, contents distribution technologies have been used to cope with the explosive demand for Web services. In this paper, we addressed the issue of the optimal placement of replicas in the environment where Web contents are replicated. We placed replicas so that clients can have access to replicas with the proper delay and bandwidth. We attempted to solve the problem via dynamic programming considering cost of delay and traffic. We have come up with \(O((n-d^{h}).|ch_{vi}|)\) time complexity that is less than O(n 2). We defined the threshold and proved that our algorithm guarantees the reliable services.

Error Recovery Algorithm for Multimedia Stream in the Tree-Based Multicast Environments

This paper describes Tree-based Multicast System which leverages Preceding Error Recovery(PER) algorithm and Media Controller(MC). This mechanism solves jitter and delay problem by reducing control packets over tree-based reliable multicast. Our proposed PER results in suppression of control packets over the network and fast recovery of a buffer space from underflow status by considering constraints of dependency between the frames and the data being played within proper time. Proposed algorithm is operated at improved TMTP(Tree-based Multicast Transport Protocol) and located in each receiver. We also evaluate and simulate the performance of PER. The results are shown that PER much superior to previous works in the point of buffer efficiency and the number of occurred control packet.

A study on efficient key management in real time wireless sensor network

Sensor network technique consists that collecting information, transfer data by sensor nodes and that control sink node. But this sensor node has limited energy power and computing capability, so it has big problem that apply traditional security technique for sensor network. Especially, Research of security technology in real time wireless sensor network is not consisting yet. So we propose about efficient key management mechanism to allow existent secret sharing mechanism and one-way hash algorithm in real time wireless sensor network environment.

On-demand one-time overlay multicast tree for multimedia transmission over large Internet environment

IP multicast has not been deployed because of hardware problems. So a new scheme called end system multicast or overlay multicast for group communication has been emerged. It supports IP multicast functions, which is located on application level. For developing it, we have been focused on efficient overlay tree construction among group members with low stretch and stress. However, we should consider a variety of transmission or receipt condition since a real Internet environment has users with various transmission/receipt rates. Thus, we make on-demand one-time source specific tree depending on required bandwidth information of group members when a member requests data transmission. Our mechanism provides satisfied data quality limited maximum transmission rate of the source to each group members. Furthermore, we manage a large group enough as distributing control information to cores that are designated members for maintaining host member information. Lastly, we prove that our tree guarantees data quality to each group members, and show low tree construction time is required. In addition, for evaluating group scalability, we analyze control information increasing rate via group size, and validate its scalability.

A Replica Placement Algorithm reducing Time Complexity

Recently, contents distribution technologies have been used to cope with the explosive demand for Web services. In this paper, we addressed the issue of the optimal placement of replicas in the environment where Web contents are replicated. We placed replicas so that clients can have access to replicas with the proper delay and bandwidth. We attempted to solve the problem via dynamic programming considering cost of delay and traffic We have come up with time complexity that is less than . We defined the threshold and proved that our algorithm guarantees the reliable services.

Preceding Error Recovery Algorithm for Multimedia Stream in the Tree-based Multicast Environments

IP Multicast is required of more little network resources than one in unicast. Furthermore, reliable multicast has been researched for supporting reliability at IP Multicast mechanism. Although these studies are carried out, they only have focused on general data. In other words, in case that realtime packet, they can not support reliability since they do not consider realtime properties such as dependency of interframe and playback in time. Besides, we also request to support scalability because we are based on Mobile IP network together with internet. Thus, we need a mechanism to guarantee reliability and scalability of realtime stream data. In this paper, we propose PER (Preceding Error Recovery) that reflect characteristics of the realtime data, especially for H.323. PER provides scalable reliability because it is based on tree-based multicast basically and helps to support scalable relibility as reducing control packet and recovers stream buffer space from underflow status as soon as possible. PER shows much better scalable and reliable than existing works.