• Journal of the Korea Society of Computer and Information
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• v.15 no.3
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• pp.81-89
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• 2010

The research on peer-to-peer streaming schemes has largely focused on tree-push and mesh-pull structures. However, the tree-push structure has a defect that the tree restructuring time is long, and the mesh-pull structure has long startup delay and lag time from source servers. In this paper, we propose a new peer-to-peer live streaming scheme based on a push-mesh structure that takes advantages of tree-push and mesh-pull structure simultaneously. This structure basically provides the mesh-pull mechanism for data transmission and utilizes peers with high network upload capacity. It also supports the push mechanism along with paths from a source server, super peers, and selected general peers. By NS-2 simulation experiments, we finally show that our proposed scheme can achieve shorter startup delay than the mesh-pull structure, similar lag time to tree-push structure and best playback continuity among the three schemes.

• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.30-44
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• 2009

In this paper, we propose the mobile P2P structure supporting content searches for mobile peers efficiently. The proposed mobile P2P structure is a 3-tier structure which consists of a mobile peer, a mobile super peer, and a stationary super peer to reduce the content search cost of mobile P2P service. For content searches, mobile peer searches content in the communication range and performs hierarchical content searches which is using mobile super peer, stationary super peer for expansion of query region. In order to support hierarchial content searches and the continuity of services according to peer mobilities, peer's join/leave processes are explicitly stored by supporting message structures to the upper layer It is shown through experimental evaluation that the proposed structure improves about 32% contents search performance over the existing 2-tier structure. Since it also reduces the messages transferred to the stationary super peers, it reduced about 25% search loads of them.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.74-82
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• 2008

In this paper, we propose a P2P based IPTV system using a multiple chain architecture. Proposed system is robust to the peer churn. As opposed to the internet the IPTV network managed by a single ISP has fewer bandwidth constraints and end-to-end connectivity. So, we emphasize preferentially robustness of a P2P network in IPTV environment. A single chain structure which was proposed previously emphasizes simplicity, however there exists considerable delay time at the end part of peers as the number of peers increasing. As a solution to the problem, we propose the scheme which seperates the chain into several levels and again divides each level into spans to diminish a delay time. Though the chain is separated into level and span, basic structure of proposed scheme is still a chain structure. So the scheme simplifies the recovery procedure caused by join or departure of peers. We will show the improved performance of proposed scheme rather than single chain structure with respect to the delay time and reliability.

• English Language & Literature Teaching
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• v.15 no.2
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• pp.151-168
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• 2009

The present study investigates the impact of trained peer feedback on the quantity and quality of revisions made by EFL students at a low-intermediate level. Peer review training was carried out in experimental group through four in-class training sessions and four peer dyad-instructor conferences after class. Students' $1^{st}$ drafts with written peer feedback and revised drafts prior to and post training were collected and analyzed. Results reveal that after training the students produced more revisions in response to their peer comments (96% of total revisions) and those revisions were counted as enhanced in quality (93% of peer-triggered revisions). In contrast, the results of paired t-test within control group indicate that there was no significant difference between two data collected from week 3 and week 16 (t = -.57, df =19, p = .577 at p < .05). The findings suggest that training as an ongoing process of teacher intervention contributes to effectiveness of the peer feedback activity. The study provides pedagogical implications for how to structure and implement peer review training for the sake of its direct strength in an EFL writing class.

• Journal of Digital Contents Society
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• v.12 no.1
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• pp.133-139
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• 2011

Structured P2P (peer-to-peer) networks have received much attention in research communities and the industry. The data stored in structured P2P networks can be located in a log-scale time without using central severs. The link-structure of structured P2P networks should be maintained for keeping log-scale search performance of it. When nodes join or leave structured P2P networks frequently, some links become unavailable and search performance is degraded by these links. To sustain search performance of structured P2P networks, periodic link recovery scheme is generally used. However, when the link recovery period is short or long compared with node join and leave rates, it is possible that sufficient number of links are not restored or excessive messages are used after the link-structure is restored. We propose the adaptive link recovery determination algorithm to maintain the link-structure of structured P2P networks when the rates of node joining and leaving are changed dynamically. The simulation results show that the proposed algorithm can maintain similar QoS under various node leaving rates.

• The KIPS Transactions:PartA
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• v.13A no.6 s.103
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• pp.501-510
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• 2006

The self-organizing super peer ring P2P search scheme improves search performance of the existing unstructured peer-to-peer systems, in which super peers with high capacity constitute a ring structure and all peer in the system utilize the ring for publishing or querying their keys. In this paper, we further improves the performance of the self-organizing ring by adaptively changing its super peer ratio according to the status of the entire system. By using PSO, the optimized super peer ratio can be maintained within the system. Through simulations, we show that our self-organizing super peer ring optimized by PSO outperforms not only the fixed super peer ring but also the self-organizing super ring with fixed ratio in the aspect of query success rate.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1961-1962
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• 2008

Hybrid Peer-to-Peer structure is sharing resource in each peer, but various resource that is with go peer indexing and segment that search from attained in server who function is solidified that is not attained in peer itself be. Basis algorithm was based on Ethernet protocol and administration of each peer enabled in center server and peer does as can confirm breakdown existence and nonexistence through communication with center server and the internet through this directly expensive test expense and a lot of test times of existing test method of access method necessary problem effectively improve.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.9
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• pp.873-880
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• 2008

This paper deals with the peer-to-peer data communication to connect each distributed levels of developed unmanned system according to the JAUS. The JAUS is to support the acquisition of unmanned system by providing a mechanism for reducing system life-cycle costs. Each of distributed levels of the JAUS protocol divides into a system, some of subsystems, nodes and components/instances, each of which may be independent or interdependence. We have to distribute each of the levels because high performance is supported in order to create several sub-processor computing data in one processor with high CPU speed performance. To complement such disadvantage, we must think the concept that a distributed processing agrees with separating each of levels from the JAUS protocol. Therefore, each of distributed independent levels send data to another level and then it has to be able to process the received data in other levels. So, peer-to-peer communication has to control a data flow of distributed levels. In this research, we explain each of levels of the JAUS and peer-to-peer communication structure among the levels using our developed unmanned ground vehicle.

• Proceedings of the Korean Information Science Society Conference
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• 2010.11a
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• pp.9-10
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• 2010

• International journal of advanced smart convergence
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• v.4 no.2
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• pp.38-45
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• 2015

Peer-to-Peer(P2P) systems are generally classified into two categories; hybrid and pure P2P. Hybrid systems have a single central index server keeping the details of shared information, so that undesirable effects such as heavy load on that server and lack of fault-tolerance can be caused. Pure P2P causes the other problems such as message flooding and scalability although it shows high degree of fault-tolerance. Recently, mobile agent-based distributed computing has been receiving wide attention for its potential to support disconnected operations, high asynchrony, and thus saving network bandwidth. In this paper, a new scheme of peer coordination is proposed for a decentralized P2P network with self-organizing structure. We deployed mobile agents for incorporating the advantages of usage of mobile agents into our P2P network. Proposed P2P network has both advantages of hybrid and pure P2P. The problems of heavy load on the server and lack of fault-tolerance are improved by using multiple special peers called super-peers. And the problems of pure P2P can be reduced by using mobile agents.