• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.6
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• pp.205-212
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• 2003

Because a wireless ad hoc network does not have fixed infrastructure, a call admission control approach researched in a wireless network is not feasible to this network. In this paper, we propose call admission control scheme to support this problem and the burst handoff traffic due to group mobility in a wireless ad hoc network. This scheme is an adaptive guard channel scheme which adapt the number of guard channels in each MBS(mobile base station) according to the current estimate of the potential handoff call rate derived from the number of ongoing calls within the coverage area of an MBS that initiate group handoff in a wireless ad hoc network. Our simulation studies are performed for comparisons of the proposed scheme with the other channel allocation schemes. Simulation results show that the proposed scheme efficiently reduces handoff call blocking probability in wireless ad hoc networks.

• 전자공학회논문지 IE
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• v.47 no.3
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• pp.41-46
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• 2010

WSN, or Wireless Sensor Network, consists of a multitude of inexpensive micro-sensors. Because the batteries in sensor nodes can not be replaced once they are deployed, the life of a WSN is absolutely determined by the batteries. So, energy efficiency of a network is a critical factor for long-life operation. LEACH protocol which divides WSN into two groups is a typical routing protocol based on the clustering scheme for the efficient use of limited energy. It is composed of round units which are separated into set-up and steady state. In this paper we propose a power saving scheme to minimize set-up phase itself and to involve a data comparison algorithm. We evaluate the performance of the proposed scheme in comparison with original LEACH protocol. Simulation results validate our scheme has better performance in terms of the number of alive nodes as time evolves and average energy dissipated.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.1
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• pp.62-69
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• 2008

In this paper, we proposed the real-time bio-signals monitoring system that is based on the ZigBee wireless sensor network and SIP. This system makes medical team and user easily confirm user's medical state irrelative to their location and time. The communication between medical sensors and the user's end device uses the ZigBee wireless sensor network. The power consumption was decreased because wireless sensor network does not use the Ad-hoc routing protocol but routing protocol that is based on tree structure. Our proposed system includes a wireless user's end device, monitoring console, SIP server and database server. This real-time bio-signals monitoring system makes possible to implement the U-health care services and improving efficiency of medical treatment services.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.44 no.4 s.316
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• pp.79-88
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• 2007

Demand for the technology for access to device control network in industry and for access to building automation system via internet is on the increase. In such technology integration of a device control network with a data network such as internet and organizing wide-ranging DCS(distributed control system) is needed, and it can be realized in the framework of VDN(virtual device network)[1,2]. Specifications for device control network and data network are quite different because of the differences in application. So a router that translates the communication protocol between device control network and data network and efficiently transmits information to destination is needed for implementation of the VDN, This paper proposes the concept of NCS(networked control system) based on VDN(virtual device network) and suggests the routing algorithm that uses embedded system.[3]

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.4
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• pp.337-349
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• 2013

In this paper, we propose a new mobility management scheme, called i-FP(intelligent Fast PMIPv6). Our proposed i-FP scheme is addressed for solving the existing local mobility management problems from legacy frameworks. To move MN(Mobile Node) to other networks in one domain, i-FP employs three network entities which are extended from PMIPv6(Proxy Mobile IPv6), LMA(Local Mobility Anchor), MAG(Mobile Access Gateway) and MN. In i-FP, the three network entities can reduce the handover delay time of MNs. Also, i-FP uses an IP header swapping mechanism to avoid the traffic overhead and improve the throughput of network. To evaluate the performance of i-FP, we analyze our i-FP, HMIPv6(Hierarchical Mobile IPv6) and PMIPv6 which are legacy protocols of local mobility management in terms of various parameters. Finally, our i-FP scheme shows good performance(reduction of routing hops 10.2%, signaling costs 58.5% and handover delay 16.3%) than other network schemes for the total cost.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.839-842
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• 2011

Lately Various researches on energy harvesting techniques for wireless sensor networks have been performed to overcome the power limitation of sensor nodes. In wireless sensor networks with harvesting techniques, sensor nodes exploit environmental energy, such as solar or wind energy, as the power sources of the nodes. Existing energy constrained environment routing protocols may not be suitable for energy harvesting based wireless sensor networks because they do not consider the accumulated energy from harvesting devices. In addition, the paths which aren't dispersed shorten the network lifetime. Therefore, in this paper, the algorithm that the path between each node is dispersed is proposed. In case of using the algorithm to be proposed through the simulator it showed that path of the node is variously reflected.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2249-2261
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• 1999

In this paper, we describe the design and implementation of the Label Distribution Protocol (LDP) for Multiprotocol Label Switching System. We review the implementation issues of LDP that is required to make a gigabit switched router, and propose a detail design of it. We present the data structures and procedures for the LDP as a result, which are based on IETF standard. We present design issues for applying this to carrier class products. The implemented protocol could afford 40,000 entries of the IP routing table that is required for deploying this system to commercialized data network. Furthermore this system implemented using the standard API of Unix, as a result, it has portability. By implementing LDP based on the international standard and these implementation issues, we expect that the implemented LDP will be interoperable with other commercialized products. We prove the validity of the design of the LDP through prototyping, and also verify the prototype with the specification using the process algebra and the performance analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.57-65
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• 2007

The overlay multicast that has been recently presented as IP alternative for the IP multicast has been getting much persuasion by the computing power of the hardware and the advancement of the network techniques to enforce Routing in application-level. In an overlay multicast, the system resource and the network bandwidth must be utilized efficiently to service real-time HDTV images. Specifically, the system must consider the delay and the jitter that can be incurred at the application-level. In this paper, we implement a server and a client to broadcast HDTV, in the session composed by the existing overlay multicast protocol. The broadcasting server performs the service using a TV tuner, An HDTV camcorder, and files, clients constituting a multicast group relay the received data to other clients. At this time, the information that the clients report periodically, including their delay and the network state, to the server is used as an important information to maintain an overlay session. The implementation is based on the DirectX and its performance is evaluated by the LAN test bed that has been set.

• Journal of Satellite, Information and Communications
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• v.9 no.2
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• pp.18-22
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• 2014

Satellite communications consist of communications between base stations of the ground and satellites. For efficient satellite communications, ground networks should be organically utilized. Grid networks are frequently used in and outside the country for wireless communications. The performance of wireless communications is determined by mobility, topography, and jamming signals. Therefore, continuous studies of grid networks are necessary for the utilization of next period satellite networks. Since military communications are used based on wireless systems, they can be considered as a sample of utilization of grid networks. Therefore, this paper presented the results of simulations conducted for the improvement of the performance of the grid networks used in military communications that employing the OSPF, a popular routing protocol for military applications. First we investigate the effects of changing the bit error rate (BER) and number of routers. Then we discuss the effects of maximum segment size (MSS) on network behavior and stability. In this way, we can determine the appropriate MSS for a grid network under various values of BER and number of routers. Such results can be also applied to commercial grid network evaluations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.510-513
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• 2006

Mobile Ad-hoc networks have recently attracted a lot of attention in the research community as well as in industry. Although the previous research mainly focused on various of Ad-hoc in routing we consider, in this paper, how to efficiently support applications such as variable Geocasting basd on Ad-hoc networks. The goal of a geocasting protocol is deliver data packets to a group of nodes that are located within a specified geocasting region. Previous research that support geocast service in mobilie computing based on Ad-hoc have the non-optimization problem of data delivery path, overhead by frequent reconstruction of the geocast tree, and service disruption problem. In this paper, we propose the mobility pattern based geocast technique using variable service range according to the mobility of destination node and resource reservation to solve this problem. The experimental results show that our proposed mechanism has improved performance than previous research.