• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4A
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• pp.385-392
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• 2006

It is widely accepted that high user densities in mobile multimedia environments can only be achieved with micro- and pico-cell. The smaller cell size causes frequent handovers between cells, and decreases permissible handover processing delay. This may result in the handover failure, in addition to the loss of some packets during the handover. In these cases, re-transmission is needed in order to compensate errors, which in turn triggers a rapid degradation of throughput. In this paper, we propose a new handover scheme for the next generation mobile communication systems, in which the handover setup process is done in advance before a handover request by predicting the handover cell based on mobile terminal's current position and moving direction. Simulation is performed in order to analyze the handover failure rate and packet loss rate. Simulation results show that our proposed method provides a better performance than the conventional method.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.12
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• pp.1189-1193
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• 2010

Mobility management is one of the most important research issues in 6LoWPAN, Since the IP-WSN application domain is expanded to real-time applications such as healthcare and surveillance systems, a fast and seamless handover becomes an important criterion in 6LoWPAN. However, a draft of IETF 6LoWPAN WG for mobility support does not decrease handover delay. Although LoWMob supports a fast intra-PAN handover. it can be supported when the infrastructure node has the location information of the other nodes in the mobile node's moving direction. In this paper, we propose a fast and seamless mobility protocol to support intra-PAN handover, named intra-MARIO. In intra-MARIO, a parent node of the mobile node preconfigures its handover to the PAN when the parent node detects its movement, thereby reducing the handover delay. Since intra-MARIO also supports route optimization, the mobile node can communicate with its corresponding nodes through the optimal route. In this paper, we analysis the signaling cost and evaluates that the handover can be completed in 20ms by simulation.

• Journal of the Korea Society of Computer and Information
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• v.13 no.7
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• pp.181-188
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• 2008

Nowadays, WiMAX which provides internet service with a middle and low speed serves more function and is wider than Wi-Fi. While they solve the security risks as subscribers do handover by subscriber's re-certification procedure as the Network range is getting wider, there are more security problems making the problems of electric-power consumption and delay. This paper suggests a handover mechanism which simplify the subscriber's re-certification procedure and prevents a security problem as doing handover for solving the problem of delay and the rate of processing. The mechanism can cooperate with PKI structure to increase flexibility and security and minimize network re-entry procedure or re-certification procedure by providing continual service. As a result. the mechanism's throughput as the number of subscribers is lower than IEEE 802.16e and the mechanism proves that it is secure from the attack of man-in-the-middle and reply as doing handover.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.6
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• pp.265-278
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• 2013

With the recent advancements in various wireless communication technologies, the importance of mobile multicasting is coming to the fore, in an effort to use network resources more efficiently. In the past, when various mobile IP-based multicast techniques were proposed, the focus was put on the costs needed for network delivery for providing multicast services, as well as on minimizing the multicast handover delay. For techniques using MIPv6 (Mobile IPv6), a host-based mobility management protocol, however, it is fundamentally difficult to resolve the problems of handover delay and tunnel convergence. To resolve these problems, a network-based mobility management protocol called PMIPv6 (Proxy Mobile IPv6) was standardized. Although performance is improved in PMIPv6 over MIPv6, it still suffers from the problems of handover delay and tunnel convergence. In this paper, to overcome these limitations, a technique called LFH (Low-cost and Fast Handoff) is proposed for fast and low-cost mobility management with multicasting support in PMIPv6 networks. To reduce the interactions between the complex multicast routing protocol and the multicast messages, a simplified proxy method called MLD (Multicast Listener Discovery) is implemented and modified. Furthermore, a TCR (Tunnel Combination and Reconstruction) algorithm was used in the multicast handover procedure within the LMA (Local Mobility Anchor) domain, as well as in the multicast handover procedure between domains, in order to overcome the problem of tunnel convergence. As a result, it was found that LFH has reduced multicast delay compared to other types of multicast techniques, and that it requires lower costs as well.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.11
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• pp.57-66
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• 2004

It is widely accepted that the coverage with high user densities in mobile multimedia environments can only be achieved with small cell such as micro- and pico-cell. The smaller cell size causes frequent handovers between cells and a decrease in the permissible handover processing delay. This may result in the handover failure, in addition to the loss of some packets during the handover. In these cases, re-transmission is needed in order to compensate errors, which triggers a rapid degradation of throughput. In this paper, we propose a new handover scheme in the next generation mobile communication systems, in which the handover setup process is done in advance before a handover request by predicting the handover cell based on mobile terminal's current position and moving direction. Simulation is focused on the handover failure rate and packet loss rate. The simulation results show that our proposed method provides a better performance than the conventional method.

• The KIPS Transactions:PartC
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• v.13C no.1 s.104
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• pp.121-128
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• 2006

In Mobile IPv6, a handover latency is an important issue. To reduce the handover latency, mipshop working group in IETF has studied the fast handover(FMIPv6) which creates and verifies a new care-of address(NCoA) in advance before a layer 2 handover resulting in reduced handover latency. Even in FMIPv6, the NCoA must be registered in a home agent(HA). This registration still creates a significant amount of delay. To reduce registration latency, we propose a tentative and early binding update(TEBU) scheme that the NCoA is registered in the HA in advance during the layer 2 handover based on FMIPv6. We use cost analysis for the performance evaluation. As a result, we found that the TEBU scheme guarantees lower handover latency than FMIPv6 as much as approximately 21%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7B
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• pp.710-720
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• 2009

The Future Generation Networks(FGNs) are proposed to integrate various heterogeneous access technologies, and further expected to support both vertical and seamless handovers. In this motivation, the IEEE 802.21 specifies Media Independent Handover(Mlli) services to enhance the mobile user experience by optimizing handovers between heterogeneous access networks. Additionally, Fast handover for MIPv6(FM1Pv6) is introduced to provide transparent host mobility and to improve handover performance by reducing handover delay as well. This paper focuses on the coordination of FMIPv6 and MIH, and introduces an enhanced mobility management framework suited for FGN. This novel framework replaces handover signaling messages used in wireless networks with novel MIH messages and local primitives. Moreover, Serving Access Router(SAR) performs most of handover processes instead of Mobile Node(MN). Therefore, the proposed mobility management framework reduces handover latency, packet loss, and signaling overhead significantly. We further evaluate the performance of the proposed framework by using both numerical analysis and network simulations.

• KIPS Transactions on Computer and Communication Systems
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• v.1 no.3
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• pp.219-228
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• 2012

As the wireless Internet become more widely accessible, variety of Internet services can be used without limitation of location. However, existing mobility management methods such as MIP and PMIP of IETF requires the load of heavy protocol stack on the mobile nodes or the addition of components such as LMA and MAG. In this paper, we proposed the location management technique in the PMIPv6 and Fast Handover technique. according to the moving pattern of the node, the location management technique proposed in order to adjust the paging area dynamically. The Fast Handover technique applied MIH technology and it reduced the handover signal processing time between heterogeneous network. The location management cost in the environment which the node moves in order to evaluate this and handover delay time was calculate. The proposal technique was efficiently more evaluated than PMIPv6 with the smallest 29% and maximum 83%.

• Korean Journal of Construction Engineering and Management
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• v.9 no.5
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• pp.214-226
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• 2008

Construction delay caused considerable losses to project parties. Avoiding construction delays is important to save costs for project stakeholders. The main objective of this paper is to identify major causes of construction delays of apartment construction projects in Vietnam. Sixteen causes of delay were identified through a questionnaire survey of 166 professionals. Factor analysis was employed to categorize these causes. The results of the survey revealed the main causes of delay of apartment projects in Vietnam are: (1) owner's and contractor'S financial difficulties; (2) lack of experienced contractors; (3) late delivery of materials; (4) late construction site handover; (5) owner's late payments for completed works; (6) low bid prices; (7) inappropriate construction method; and (8) defective works and unnecessary reworks. Factor analysis uncovered that causes of delay can be grouped under five categories labeled the five INs: incompetence, ineffectiveness, inadequateness, inapplicableness and inconceivableness. Comparative analysis between the Vietnam construction industry (VCI) and the Korea construction industry (KCI) has been performed to infer valuable lessons for researchers and practitioners in the VCI and the KCI. Comparative analysis indicated that main causes of delay in the VCI somewhat differ from main causes of delay in the KCI. However, "contractor'S financial difficulties", "late construction site handover", "unnecessary rework", "incapable designers", "site clearance difficulties" are common causes of delay in the VCI as well as the KCI. The findings of this research can be used as a guideline to overcome problems in the VCI as well as in other construction industries. Since Korea has emerged as the first largest foreign investor in Vietnam, the results of this study may be useful not only to practitioners and researchers in Vietnam but also to participants in Korea.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.832-844
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• 1999

In this paper, we analyzed mobile-IP protocol of IETF, and propose new method to improve performance in handover environments. In proposed method, cache agent manages mobility binding information for mobile host. Thus, effective support of mobility is possible. Also, when handover occurs, mobile host recognizes change of foreign agent, and transmits registration message to new foreign agent. However, during registration time, data packet loss is occurs in old foreign agent. Thus, we prevent data loss by using data packet buffering and forwarding in old foreign agent.According to simulation results for data packet transmission performance in the case of handover occurring, proposed method has better performance than previous method in the view of transmission delay and throughput. Especially, if handover occurs very often, data buffering and forwarding method in foreign agent could guarantee better performance.