• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.9
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• pp.829-840
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• 2012

Recently, in network communication environments, it is changing very fast from wired to wireless. The open shortest path firtst (OSPF), one of link state routing protocols, mainly used in wired networks, is the routing method to select optimal traffic path as identifying the link state of neighbor routers. The traditional OSPF cost functions performs with first fixed cost permanently, unless the router link is changed. However, in wireless networks, the performance of links show big difference by other environment factors. The bit error rate (BER), a parameter which can quite affect link state in wireless networks, is not considered in the traditional OSPF cost functions. Only a link bandwidth is considered in the traditional OSPF cost functions. In this paper, we verify the various parameters which can affect link performance, whether it is permissible to use as the parameter of proposed cost functions. To propose new cost functions, we use the effective bandwidth. This bandwidth is calculated by proposed formula using the BER of the network link and link bandwidth. As applied by the proposed triggering condition, the calculated effective bandwidth decrease the unstable of network by generating less link state update messages in wireless networks that frequently changes the link state. Simulation results show that the proposed cost functions significantly outperforms the traditional cost functions in wireless networks in terms of the services of VoIP and data transmission.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.599-603
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• 2016

Recently the wireless LAN system is substituting wired LAN system notably as the number of mobile users increases greatly along the advancement of technology. But the wireless LAN has a critical weakness in the security such as data leakage. Thus a safe security system is imperative to avoid threatening from hackers with offering the best convenience to inner users. In this research, we have developed a RADIUS wireless LAN security system for industrial applications, which performs the EAP authentication with the compatibility for any maker of wireless LAN. The system has interfaces based on WEB, providing DB access function for user management so that users can perform authentication of 802.1x in their computers.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1097-1103
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• 2015

In order to build network infrastructure to implement the aforementioned advantages enabling smart device users to work anywhere, professional support and expensive VPN devices are required. This is a barrier to supplying VPN devices to small and medium-sized institutes. To address this issue, this study aims to implement OpenVPN, OpenSSH and iproute based on the OpenWRT platform which is an embedded OS for open networks in affordable open wired/wireless gateway H/W platforms to support the inter-network VPN. In addition, the network environment can be maintained optimal by applying a "multi-queuing real-time traffic shaping technology" to VPN tunnels, although channel quality changes.

• Journal of Digital Convergence
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• v.14 no.10
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• pp.45-51
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• 2016

The purpose of this paper is to plan deployment strategy of public key infrastructure for Malawi by considering the information and communication technology status on it. For this, we will review the information communication technology status on developing and least developed countries focused on Malawi and plan deployment strategy of mobile based public key infrastructure. First of all, we extract out security considerations for public key infrastructure, which is efficient for wireless communication, and design a new lightweight public key infrastructure apt to mobile device by considering Malawi's information communication technology status. Especially, the proposed mobile based public key infrastructure uses smartcards for all the processes of certificate. It could guarantee the same security as the wired counter part based on lightweight mobile device.

• Progress in Medical Physics
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• v.14 no.2
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• pp.124-130
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• 2003

Currently, as a consequence of PACS (Picture Archiving Communication System) implementation many hospitals are replacing conventional film-type interpretations of diagnostic medical images with new digital-format interpretations that can also be saved, and retrieve However, the big limitation in PACS is considered to be the lack of mobility. The purpose of this study is to determine the optimal communication packet size. This was done by considering the terms occurred in the wireless communication. After encoding medical image using JPGE2000 image compression method, This method embodied auto-error correction technique preventing the loss of packets occurred during wireless communication. A PC class server, with capabilities to load, collect data, save images, and connect with other network, was installed. Image data were compressed using JPEG2000 algorithm which supports the capability of high energy density and compression ratio, to communicate through a wireless network. Image data were also transmitted in block units coeded by JPEG2000 to prevent the loss of the packets in a wireless network. When JPGE2000 image data were decoded in a PUA (Personal Digital Assistant), it was instantaneous for a MR (Magnetic Resonance) head image of 256${\times}$256 pixels, while it took approximately 5 seconds to decode a CR (Computed Radiography) chest image of 800${\times}$790 pixels. In the transmission of the image data using a CDMA 1X module (Code-Division Multiple Access 1st Generation), 256 byte/sec was considered a stable transmission rate, but packets were lost in the intervals at the transmission rate of 1Kbyte/sec. However, even with a transmission rate above 1 Kbyte/sec, packets were not lost in wireless LAN. Current PACS are not compatible with wireless networks. because it does not have an interface between wired and wireless. Thus, the mobile JPEG2000 image viewing system was developed in order to complement mobility-a limitation in PACS. Moreover, the weak-connections of the wireless network was enhanced by re-transmitting image data within a limitations The results of this study are expected to play an interface role between the current wired-networks PACS and the mobile devices.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.6
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• pp.92-100
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• 2008

Ad-hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any centralized administration or reliable support services such as wired network and base stations. Recently, Ad-hoc networks are evolving to support multimedia contents according to expansion of ad hoc multi-hop communication system. Wireless ad-hoc network is different from the conventional wired network by frequent changes in network topology, number of routers and resources, there are a number of problems in applying conventional routing protocol to ad-hoc network. The AODV routing protocol is proposed for mobile node in ad-hoc networks. AODV protocol that provides to guarantee QoS for data transmission in ad hoc networks that link break frequently occurs. In this paper, AODV routing protocol based NDIS(Network Driver Interface Specification) is implemented. We design high performance image transmission that can operate with software(AODV) for ad-hoc networks without degradation. and verify operation of AODV routing protocol on the test bed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.2
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• pp.795-800
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• 2012

Recently, as communication is evolved by leaps and bounds through wired/wireless networks, variety of services are routinely made through communication networks. Accordingly, technology that is for protecting data and personal information is required essentially, and study of security technology is actively being make progress to solve these information protection problems. In this paper, to expand selection scope of the key of elliptic curve cryptography, arithmetic items of real number based elliptic curve algorithm among various cryptographic algorithms was studied. The result of an experiment, we could know that elliptic curve cryptography using the real number can choose more various keys than existing elliptic curve cryptography using integer and implement securer cryptographic system.

• The Journal of the Korea Contents Association
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• v.4 no.1
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• pp.1-7
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• 2004

In addition to wired communication technology, wireless communication technology has been driving communication revolution nowadays. Bluetooth technology carries out data/voice communication making pico-net and the various application services are supported by access network connected to public network. This paper presents educational software development of bluetooth protocol stack including HCI, L2CAP, RFCOMM, SDP and profiles including GAP, SPP, GEOP, FTP. This software which supports programming environment of these protocol monitoring and emulation is implemented basically step by step for education based on H connected to the bluetooth device through RS-232-C, UART or USB cable. Application program coded by Visual C is operated over the firmware loaded on the bluetooth device connected to the PC. Additionally ftp and chatting function are developed to enhance educational efficiency.

• Journal of KIISE:Information Networking
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• v.32 no.3
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• pp.415-426
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• 2005

Wireless internet, which becomes a hot social issue, has limitations due to the following characteristics, as different from wired internet. It has low bandwidth, frequent disconnection, low computing power, and small screen in user terminal. Also, it has technical issues to Improve in terms of user mobility, network protocol, security, and etc. Wireless internet server should be scalable to handle a large scale traffic due to rapidly growing users. In this paper, wireless internet proxy server clusters are used for the wireless Internet because their caching, distillation, and clustering functions are helpful to overcome the above limitations and needs. TranSend was proposed as a clustering based wireless internet proxy server but it has disadvantages; 1) its scalability is difficult to achieve because there is no systematic way to do it and 2) its structure is complex because of the inefficient communication structure among modules. In our former research, we proposed the All-in-one structure which can be scalable in a systematic way but it also has disadvantages; 1) data sharing among cache servers is not allowed and 2) its communication structure among modules is complex. In this paper, we proposed its improved scheme which has an efficient communication structure among modules and allows data to be shared among cache servers. We performed experiments using 16 PCs and experimental results show 54.86$\%$ and 4.70$\%$ performance improvement of the proposed system compared to TranSend and All-in-one system respectively Due to data sharing amount cache servers, the proposed scheme has an advantage of keeping a fixed size of the total cache memory regardless of cache server numbers. On the contrary, in All-in-one, the total cache memory size increases proportional to the number of cache servers since each cache server should keep all cache data, respectively.

• Journal of The Korean Association of Information Education
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• v.9 no.1
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• pp.27-37
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• 2005

Advances in the wireless Internet have led to the rise of diverse techniques which can access information regardless of time and place. There are many research efforts to identify the various ways to use a cellular phone in our everyday life. However, it has been rarely used in the elementary school. As an attempt to apply the wireless Internet technology to the elementary school, this study is to design and implement a wireless Internet homepage where the parents would be able to have an easy access to the information any place and any time. The characteristics of the wireless Internet homepage are as follows; first, the images were reduced to the minimum and the text-oriented information is mostly used to deliver the key information, considering the small screen and relatively slow transmission rates. Second, by providing a link set up between the wireless homepage and the wired Internet homepage, users can choose the more convenient access tool. Finally, the SMS (Short Message Service) messages could be used for an immediate delivery of information.