• Journal of Advanced Navigation Technology
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• 제19권6호
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• pp.601-606
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• 2015

Recently wireless data services have widely spread on various multimedia devices such as smart phones and tablets. Existing wired data services have been replaced by wireless data services using mobile devices. Especially domestic mobile devices supporting both Wireless-Fidelity (Wi-Fi) and long term evolution (LTE) services have increased steadily. While Wi-Fi network is provided free of charge, LTE network is offered to pay for. Therefore, mobile devices provide smart network switch to support both preferred Wi-Fi and LTE networks. However, such handover and roaming between Wi-Fi and LTE networks can cause data connection stop in spite of charged data services. This paper has proposed the method to overcome data connection stop for guaranteeing seamless data service during handover and roaming procedures between networks.

• Proceedings of the IEEK Conference
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.74-77
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• 1998

We consider connection-oriented wireless cellular networks. These networks employ dedicated radio channels for the transmission of signaling information. A forward signaling channel is a common signaling channel assigned to carry the multiplexed stream of paging and channel allocation(virtual circuit allocation) packets from a base station to mobile stations. The delay levels experienced by paging and channel allocation packets have serious effect on the utilization level of the limited radio channel capacity. While a slotted mode operation is used to reduce the power consumption level at mobile stations, it may induce an increase in packet delay levels. In this paper, we thus consider a multiplexing scheme for paging and channel allocation packets under which slots are dynamically allocated for the paging packet transmission. For this dynamic scheme, we develop an analytical method for deriving the delay characteristics exhibited by paging and channel allocation packets, and investigate the effect of network parameters on the delay level by using this method.

• Journal of Communications and Networks
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• 제5권3호
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• pp.222-229
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• 2003

In this paper, we propose a delayed multiple copy retransmission (DMCR) scheme for data communication in wireless networks, by which multiple copies of a lost link layer frame are retransmitted one-by-one with a retransmission delay in between. The number of the copies gradually increases with the number of retransmissions. Furthermore, for implementation of the DMCR scheme in practical mobile communication system, we also propose a dynamic retransmission scheme by interleaving and a new round-robin scheduling algorithm. We compare our scheme with the previous non-delayed retransmission schemes on the performance of frame loss probability, channel capacity and total transmission time. Numerical results show that the DMCR scheme can achieve higher performance. The effect of the delay time on endto-end TCP throughput is investigated as well.

• Journal of Ubiquitous Convergence Technology
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• 제1권1호
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• pp.53-59
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• 2007

This paper proposes a new group mobility model for wireless communication. The mobility model considers the psychological and sociological behavior of each node and the perception of other nodes for describing interactions among a set of nodes. The model assumes no permanent membership of a group, capable of capturing natural behaviors as fork and join. It emulates a cooperative movement pattern observed in mobile ad hoc networks of military operation and campus, in which a set of mobile stations accomplish a cooperative motion affected by the individual behavior as well as a group behavior. The model also employs a physic model to avoid a sudden stopping and a sharping turning.

• Journal of the Korean Society for Railway
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• 제18권3호
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• pp.223-231
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• 2015

This paper proposes a new wireless backhaul technology based on MHN(Mobile Hotspot Network) which uses a wide frequency band of millimeter wave to provide wideband Wi-Fi services for subway passengers. Performance analysis of MHN up and down links, based on data: up and down links structure analysis of physical layer and simulation study of the MHN wireless backhaul link model, show that the proposed MHN-based wireless backhaul network can transmit data at a 1.2Gbps data rate and provide Internet service 100 times faster than that of conventional WiBro-based wireless backhaul networks. These results indicate that the proposed MHN technology is appropriate for subway mobile networks.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2002년도 ITC-CSCC -1
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• pp.571-574
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• 2002

In a recent wireless network environments, dynamic host configuration protocol (BHCP) service is used to assign IP addresses to mobile terminals. In IPv6 networks, it is necessary to introduce the concept of handoff to support a seamless service to mobile terminals. In a general soft handoff technique used by code-division multiple acces (CDMA) communication systems, the powers received to base station are simply compared to determine which base station will handle the signal to and from each mobile termins. However, in IPv6 network, to transmit data-oriented services, it is necessary to support an enhanced soft handoff technique with more security and quality of service. In this paper, we propose a scheme to reduce a signaling process of handoff in IPv6 network. Also, we propose a technique to reduce wasted reservation resources and to guarantee quality of service (QoS) using DHCP.

• Journal of Information Processing Systems
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• 제6권2호
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• pp.147-162
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• 2010

In this paper, we present a fine-grained localization algorithm for wireless sensor networks using a mobile beacon node. The algorithm is based on distance measurement using RSSI. The beacon node is equipped with a GPS sender and RF (radio frequency) transmitter. Each stationary sensor node is equipped with a RF. The beacon node periodically broadcasts its location information, and stationary sensor nodes perceive their positions as beacon points. A sensor node's location is computed by measuring the distance to the beacon point using RSSI. Our proposed localization scheme is evaluated using OPNET 8.1 and compared with Ssu's and Yu's localization schemes. The results show that our localization scheme outperforms the other two schemes in terms of energy efficiency (overhead) and accuracy.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권3호
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• pp.477-493
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• 2011

The IEEE 802.16 mobile multi-hop relay (MMR) task group 'j' (TGj) has introduced the multi-hop relaying concept in the IEEE 802.16 Wireless MAN, wherein a relay station (RS) is employed to improve network coverage and capacity. Several RSs can be deployed between a base station and mobile stations, and configured to form a tree-like multi-hop topology. In such architecture, we consider the problem of a path selection through which the mobile station in and outside the coverage can communicate with the base station. In this paper, we propose a new path selection algorithm that ensures more efficient distribution of resources such as bandwidth among the relaying nodes for improving the overall performance of the network. Performance of our proposed scheme is compared with the path selection algorithms based on loss rate and the shortest path algorithm. Based on the simulation results using ns-2, we show our proposal significantly improves the performance on throughput, latency and bandwidth consumption.

• Journal of Korea Society of Industrial Information Systems
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• 제6권1호
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• pp.56-60
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• 2001

An authentication protocol for wireless mobile communication systems is proposed. The protocol employs the keyed hash function to provide mutual authentication and session key distribution. This makes the low computation power of mobile stations. To provide the security architecture with minimal assumption about the security of intermediate transport networks, this protocol has no assumptions about the security of the intermediate, fixed networks.

• Journal of Korea Multimedia Society
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• 제10권2호
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• pp.226-235
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• 2007

Recently, the lETF NEMO working group on network mobility is standardizing a basic support for moving networks. We need a handover scheme for achieving the performance of transparency during the movement of mobile routers in nested mobile networks. But existing handover schemes for a mobile host are not suitable for network mobility because the packet transmission delay and traffic increase during mobile router's handover in nested mobile networks. Therefore, we propose a new seamless handover scheme using the bi-casting based on Mobile IPv6 for nested mobile networks in this paper. Compared with the handover schemes using bi-directional edge tunneling for host mobility support on simulation. And, the results show that the proposed handover scheme reduces the packet delay during a mobile router changes the point of attachment in nested mobile networks.