• Journal of Communications and Networks
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• v.17 no.2
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• pp.203-209
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• 2015

Although mobile applications are an essential characteristic of wireless sensor networks, most existing media access control (MAC) protocols focus primarily on static networks. In these protocols, fixed periodic neighbor discovery and schedule updating are used to connect and synchronize neighbors to provide successful data transmission; however, they cannot adapt to mobile speed variation and degrade the network performance dramatically. In this paper, we propose a mobile-supporting mechanism for MAC protocols, in which the decision to update the neighbors of a mobile node is made adaptively according to the mobile speed. Analysis and simulation results demonstrate that the mechanism efficiently avoids the disconnection of amobile node from its neighbors and achieves a better performance as compared with fixed periodic neighbor discovery.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.6 no.5
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• pp.446-452
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• 2005

As the name means, the WiBro is mobile service so that radio internet connection may be possible with high transmission speed using various terminal. Because WiBro is choosing suitable All-lP network architecture in internet service offer, structure of network is simple and the various supplementary service offer is available. This paper presented mobility model of terminal and proposed efficient way to improve existent way that transfer efficiency drops by data padding and analyze the performance by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.9A
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• pp.867-873
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• 2008

Cyclic delay diversity (CDD) is considered as a simple approach to exploit the frequency diversity in OFDM system. In this paper, we apply CDD to the conventional STBC/SFBC/STFBC-OFDM transmit diversity schemes for Rayleigh fading channels. We compare the performances of STBC/SFBC/STFBC with and without CDD schemes. Simulation results show that the combination of block coding with CDD works well when using the ITU-R M. 1225 channel for both Pedestrian A (Ped A) channel with the mobility of 3 km/h, and Vehicular A (Veh A) channel with the mobility of 120km/h. For a BER of $10^{-3}$, compared to the conventional block coding schemes, a gain of 2dB, 4dB, and 5dB is obtained under the Ped A channel environment by STBC-OFDM, SFBC-OFDM and STFBC-OFDM with CDD, respectively Under the Veh A channel. gains by the combined schemes are 6dB, 2dB, and 4dB, respectivcly.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.3 no.2
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• pp.42-50
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• 2004

This paper describes a new approach to Internet host mobility. We argue that local mobility, the performance of existing mobile host protocol can be significantly improved. It proposes Fast Moving Detection schemethat based on neighbor AP channel information and moving detection table. And, it composes Local Area Clustering Path (LACP) domain that collected in AP's channel information and MN interface information. It stored the roaming table to include channel information and moving detection. Those which use the proposal scheme will need to put LACP information into the beacon or probe frame. Each AP uses scheme to inform available channel information to MN. From the simulation result, we show that the proposed scheme is advantageous over the legacy schemes in terms of theburst blocking probability and the link utilization.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.17-20
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• 2008

A clustering scheme for ad hoc networks is aimed at managing a number of mobile devices by utilizing hierarchical structure of the networks. In order to construct and maintain an effective hierarchical structure in ad hoc networks where mobile devices may move at high mobility, the following requirements must be satisfied. The role of each mobile device for the hierarchical structure is adaptive to dynamic change of the topology of the ad hoc networks. The role of each mobile device should thus change autonomously based on the local information. The overhead for management of the hierarchical structure is small. The number of mobile devices in each cluster should thus be almost equivalent. This paper proposes an adaptive multihop clustering scheme for highly mobile ad hoc networks. The results obtained by extensive simulation experiments show that the proposed scheme does not depend on mobility and node degree of mobile devices in the ad hoc network, which satisfy the above requirements.

• Annual Conference of KIPS
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• 2013.11a
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• pp.400-401
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• 2013

Mobility in a network causes link disconnections and link recovery is vital for reliability of a network. A link failure affects all the preceding nodes on a damaged routing path; creates communication delay, throughput degradation, and congestion. This paper proposes link recovery mechanisms in CCN based networks. Packet overhearing is used to update neighboring nodes information. The recovery is done by forwarding node resulting in low control overhead, and better efficiency. The proposed mechanisms increase overall performance of a typical CCN and simulation results show that our proposed scheme works very well in densely populated networks with high mobility.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.12
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• pp.17-27
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• 2011

Most of the previous mobility management protocols such as IETF MIPv4/6 and its variants standardized by the IETF do not support global seamless handover because they require partially changes of the existing network infrastructure. In this article, we propose a simple mobility management protocol (SMMP) which can support global seamless handover between homogeneous or heterogeneous wireless networks. To do this, the SMMP employs separate location management function as DMMS to support global user and service mobility and the bidirectional tunnels are dynamically constructed to support seamless IP mobility by using the IEEE MIH extension server, which is extended the IEEE 802.21 MIH standards. The detailed architecture and functions of the SMMP have been designed. Finally, the mathematical analysis and the simulation have been done. The performance results show the proposed SMMP outperforms the existing MIPv6 and HMIPv6 in terms of handover latency, packet loss, pear signal noise ratio (PSNR).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.35-43
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• 2011

In this paper, we propose a novel architecture for seamless mobility management to provide users with seamless Internet connection when users roam between diverse wireless local area networks (WLANS) controlled by different management entities. There have been many researches in IETF, i.e., MIPv6, HMIPv6, and PMIPv6, to provide the mobility management. However, practically since wireless access points or access routers, which are managed by an individual manager or ISP managers, have different authentication scheme and the supported mobility management, the previous mobility management protocol developed by IETF can not guarantee the quality of service of application services as the mobile node performs the handover. To solve this drawback, we propose the mobility management scheme to provide QoS-guaranteed Internet services during the handover by configurating the wireless networks which is defined by users. More specifically, we present a model, the architecture and an algorithm for user-defined network (UDN) to provide the seamless Internet service. Finally, the performance of the proposed algorithm is evaluated by the network simulation tool.

• Journal of Korea Multimedia Society
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• v.8 no.7
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• pp.953-960
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• 2005

The Network can be easily damaged in the mobile computing environment. Mobile Support Station (MSS) which supports the Mobile Host(MH) could also be unstable too. Therefore, when a critical error occurs the repairing cost can be high. For stable repair, the hand-off strategy should be considered to save the continuing message and checkpoint information, and to reduce the cost of network repair. In this paper, we propose the Switching Trickle(ST) strategy which reduces the repairing cost for the MH's mobility. ST strategy changes the way which stores the information in connection with the number of write events(r) that occur from the hands-off strategy. Accumulated cost by increased mobility has been simulated too. From the results of simulation, the proposed strategy has shown more cost effective than the conventional strategy. The proposed strategy also has shown very supportive in saving checkpoint and message log information stably.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2533-2540
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• 2013

In multihop cellular network environments, the mobility of nodes is a major obstacle to find a reliable routing path between a mobile node (MN) and the access node (AN). Therefore, in this paper, we propose a fast and reliable neighbor discovery protocol that enables the fast and reliable neighbor discovery by considering the node mobility in the multihop cellular network. The proposed neighbor discovery protocol inhibits the transmission of unnecessary control messages to quickly find a suitable neighbor node (NN) and performs a priority-based access control to transmit control messages without collision in the order of NN desirable to be selected. Simulation results show that the proposed neighbor discovery protocol can discover the NNs faster than the conventional scheme and select a more reliable relay node although the number of neighbor nodes increases and the node mobility increases.