• The KIPS Transactions:PartC
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• v.11C no.7 s.96
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• pp.895-904
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• 2004

Due to the frequent and unpredictable topology changes, multicast still remains as challenge and no one-size-fits-all protocol could serve all kinds of needs in mobile ad hoc network. In this paper, we propose a novel scheme of Hierarchical Eulerian Ring Oriented Multicast Architecture (HEROMA) over mobile ad hoc network. It has features that concentrate on efficiency and robustness simultaneously. It is also an application-driven proposal for hazard detection. Architectures including Eulerian ring, hierarchy and multicast agent are investigated in detail Simulation results different level of improvements on control traffic, end-to-end delay and packet delivery ratio by comparing with tree-based and mesh-based multicast protocols.

• The KIPS Transactions:PartA
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• v.15A no.1
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• pp.35-44
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• 2008

It is important to manage access control for secure ubiquitous applications. In this paper, we present an access-control system for executing policy file which includes access control rules. We implemented Context-aware Access Control Manager(CACM) based on Java Context-Awareness Framework(JCAF) which provides infrastructure and API for creating context-aware applications. CACM controls accesses to method call based on the access control rules in the policy file. We also implemented a support tool to help programmers modify incorrect access control rules using static analysis information, and a simulator for simulating ubiquitous applications. We describe simulation results for several ubiquitous applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.11B
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• pp.981-988
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• 2008

In this paper, the efficient AODV routing algorithm in MANET is proposed. Because transmission channel has a high error rate and loss in MANET, the number of hops can't be regarded as an absolute network metric. After measuring FER periodically at the data link layer using cross-layer design, the scheme that every node forwards the weight of link status in the reserved field of AODV protocol is used. In order to find the efficient route, we design AODV to be able to select an optimal route that has a good channel status by evaluating the sum of weight. The proposed AODV improves throughput, routing overhead and average end-to-end delay in comparison with the generic AODV.

• Journal of Internet Computing and Services
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• v.1 no.1
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• pp.27-34
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• 2000

Recently, the use of Geographic Information System in each field of our society is on the increase according to the development of the Internet. But, thereis a problem of the user access latencies, the network traffic, and the server overload in Internet Geographic Information System because spatial data are transferred in large volumes. In this paper, we propose a cache algorithm on client side to solve the above problems. The proposed algorithm demonstrates the performance improvement over known studies by utilizing unit time and spatial proximity. In addition, this paper conducts a performance evaluation to measure the improvement in algorithm efficiency and analyzes the results of the performance evaluation. When spatial data queries are conducted, according to our performance evaluation, hit rate has been improved over the existing algorithms.

• Journal of Internet Computing and Services
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• v.9 no.2
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• pp.61-68
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• 2008

Authentication for inter-NEMO rooming is on important issue for achieving the seamless mobile networking. In this proposal, the technical challenge lies in the fact that a visited network does not initially have the authentication credentials of a roaming mobile router. This paper proposes an efficient approach for providing AAA service in NEMO environment. This approach uses localized authentication based on the roaming agreement between ISPs. A public key certificate structure is proposed, tailored to the business model of wireless internet Service Providers (ISPs). In this approach, the mutual authentication between a visited network and a roaming user can be performed locally without any control with user's home network. In conclusion, our protocol shown that communication delay can be reduced by overuse 45% overhead in communication delay than the previous AAA approach.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 2002.11a
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• pp.400-406
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• 2002

Historically, IP-based internets have been able to provide a simple best-effort delivery service to all applications they carry. Best effort treats all packets equally, with no service level, packet loss, and delay. The best-effort style has generally worked One. But the needs of users have changed. The want to use the new real-time multimedia, and multicasting applications. Thus, there is a strong need to be able to support a variety of traffic with a variety of quality-or-service requirements, within the TCP/IP architecture. This paper propose a framework that offers QoS in a DS domain using dynamic node setting method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.7
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• pp.1744-1754
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• 1998

In this paper, the data service protocol which could support data service more efficiently between mobile host and fixed host in wire network is investigated. Wireless link has high bit error rate compared with wire link. Therefore, TCP performance for the data service is degraded in wire and wireless interworking environment. Thus, to reduce performance degradation. Interworking module withsimple protocol processing function is proposed. This, interworking module analyzes the hearder information of TCP fram. If received TCP freame is a duplicated frame, TCP frame is discared. Also, if interworking moudule receives retransmission request frame is a duplicated frame, TCP freme is discarded. Also, if interworking module receives retansmission request frame, interworking module performs retransmission procedure. According to simulation results, the proposed IWF shows better performance than traditional IWF in view of delay and throughput in the wire and wireless interworking environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3A
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• pp.266-275
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• 2004

Recently, wireless networks require an efficient handover scheme due to increase of mobile devices. But Bluetooth has several problems to support the efficient handover, which are the additional increase of signaling traffic and long time of the initial setup processes of inquiry and paging processes. This paper suggests an efficient Soft Handover method for Bluetooth (eSoHoB), which reduces the eplased time of the inquiry and paging process and supports a soft handover using the anticipation method. This paper implements the eSoHoB using two Bluetooth hardware modules and a testbed to be able to receive streaming data while a Bluetooth terminal is moving. This paper measures handover delays and the operation of the soft handover to verify the proposed mhthod.

• Journal of Digital Contents Society
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• v.10 no.3
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• pp.395-400
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• 2009

The wide spread of the Internet service has brought in web GIS development. But, there are problems of the user access latencies, the network traffic, and the server overload in Internet Geographic Information System because spatial data are transferred in large volumes. In this paper, I propose a cache algorithm on client side to solve the above problems. The proposed algorithm demonstrates the performance improvement over known studies by utilizing unit time and spatial proximity. In addition, this paper conducts a performance evaluation to measure the improvement in algorithm efficiency and analyzes the results of the performance evaluation. When spatial data queries are conducted, according to our performance evaluation, hit rate has been improved over the existing algorithms.

• Journal of Digital Contents Society
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• v.12 no.1
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• pp.11-21
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• 2011

The PMIPv6 protocol that has been recently presented as an alternative for the MIPV6 has been getting much persuasion by the system resource and the network bandwidth and the advancement of the network cost. we propose an effective scheduling for multicast services based on the PMIPv6 with hand-over mechanism. it provides an additional function that is able to change multicast join processes dynamically in accordance with MAG status. in order to evaluate the ability of the proposed scheme's We test the performance of hand-over and node join costs with similar techniques. The result of simulation shows improves about 13~35% of performance.