• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.6
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• pp.98-107
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• 2011

In this paper, we propose the location determination system of an agent mobile device using the information provided by the WLAN(Wireless LAN) infrastructure. This system is configured as a typical ESS(Extended Service Set)-type WLAN structure with real-time location positioning engine and thru AP(Access Point) controller. The positioning engine collects the information of agent devices using SNMP(Small Network Management Protocol) thru AP controller and utilize those information as Cell ID. for LBS(Location Based Service). In the result of a real office environment implementation, the average success rate of inter-AP roaming is measured to 62.5% and the duration time of the device information update within the AP is average of 11 second of time, which means this system is adaptable to the location based service of above average accuracy but somewhat less urgency.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.64-68
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• 2007

Commercial WiBro and 3G HSDPA services are launched last year in order to provide high speed wireless Internet access and multimedia service. Currently mobile communication service providers concentrate on the deployment of indoor mobile network since indoor traffic is remarkably increased. For fine indoor wireless communication, an installation of access point system via Public IP network which is called Femtocell is required. The development of indoor Femtocell system must be considered in the viewpoint of low hardware complexity, cost reduction, interlocking with WiBro/HSDPA network without change of network component and easy element management. In this paper, we review the implementation issue and technology of dual mode AP which provides WiBro and HSDPA signal to the user simultaneously. Especially, we describe on the HSDPA Femtocell standardization status and possible 3 types of HSDPA communication module development design. Furthermore we analyze the merits and demerits of each HSDPA Femtocell design type and propose a system which enables handover between indoor HSDPA Femtocell and outdoor commercial HSDPA mobile network.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.1143-1150
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• 2017

In this paper, we proposed a method to display a hazard warning of hacking in the UX(: User Experience) concept level for non experts in the open Wi-Fi access area. According to the dangers of the AP raised by capture, we developed an application that provides a warning pop-up on the danger of hacking before using for APs that are distinguished by color and selected.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12C
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• pp.1258-1267
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• 2003

As the need for stable and high speed wireless Internet service Brows, the wireless LAN service provider hurries to preempt wireless LAN service market. IAPP(InterAccess Point protocol) is defined to be able to provide a secure handoff mechanism of wireless LAN terminal information between AP(Access Point)s, and the related IEEE standard is IEEE 802.11f. For the secure handoff of wireless LAN terminal, it is necessary to transfer terminal's authentication & accounting information securely from old AP to new AP IEEE 802.11f recommends RADIUS server as IAPP server which authenticates AP and provides information for secure channel between APs. This paper proposes IAPP server using Diameter protocol to overcome the limit of RADIUS sewer, and describes about the interaction between server components and integration method with the current IAPP client system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.549-552
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• 2005

Multiple wireless devices in wired and wireless heterogeneous networks communicate with counterparts via a single access point (AP). In this case, the AP becomes a bottleneck of the network, therefore buffer overflows occur frequently and result in TCP performance degradation. In this paper, a new algorithm that prevents buffer overflows at AP and enhances TCP fairness is proposed. Depending on the buffer usage of AP, the new algorithm adaptively controls each TCP senders' transmission rate, prevents buffer overflows and thus guarantees improved TCP fairness. It is proved that the algorithm makes better of TCP throughput and fairness by preventing buffer overflows.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.83-87
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• 2009

The MAC protocol of HiperLAN/2 is based on TDMA/TDD. Mobile terminal acquires a data transmission opportunity as successfulness in channel competition through RCH (Random CHannel) phase. Therefore, AP (Access Point) be able to dynamically assign optimum RCH at next frame according to the number of success and collision. In this paper, we suggest scheme that fluctuate RCH (Random CHannel) number as fixed value considering success and collision for improvement of performance in HiperLAN/2. To prove efficiency of proposed scheme, a lots of simulations are conducted and analyzed in view of throughput and access delay.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.3
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• pp.997-1005
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• 2010

Recently, there has been a growing interest in the use of WLAN technology due to its easy deployment, flexibility and so on. Examples of WLAN applications range from standard internet services such as Web access to real-time services with strict latency/throughput requirements such as multimedia video and voice over IP on wireless network environments. Fair and efficient distribution of the traffic loads among APs(Access Points) has become an important issue for improved utilization of WLAN. This paper focuses on an AP selection scheme for achieving better load balance, and hence increasing network resource utilization for each user on wireless network environments. This scheme makes use of active scan patterns and the network delay as main parameters of load measurement and AP selection. This scheme attempts to estimate the AP traffic loads by observing the up/down delay and utilize the results to maximize the link resource efficiency through load balancing. We compared the proposed scheme with the original SNR(Signal to Noise Ratio)-based scheme using the NS-2(Network Simulation.2). We found that the proposed scheme improves the throughput by 12.5% and lower the network up/down link delay by 36.84% and 60.42%, respectively. All in all, the new scheme can significantly increase overall network throughput and reduce up/down delay while providing excellent quality for voice and video services.

• Journal of the Korea Society for Simulation
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• v.17 no.4
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• pp.153-158
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• 2008

The technology of Software Defined Radio (SDR) is a possible solution to interwork flexibly between various wireless transport protocols. Ubiquitous network, like u-health service network, includes sensor devices or nodes which do not facilitate all the same transport protocols to access network. As such this may be in such unreachable situations as poverty of all required AP (Access Point)’s, faults or contention in a path of particular protocol communication, etc. This paper presents research results of modeling and simulation to analyze transport performance of multi-protocol ubiquitous network which includes SDR-based interwork nodes and congestion-controlled AP’s. Focusing mainly on dynamics of overall transport performance rather than protocol execution procedures, this paper employs the Zeigler’s DEVS (Discrete Event Systems Specification) methodology and DEVSim++simulation environment to experiment.

• Journal of the Korea Society of Computer and Information
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• v.25 no.1
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• pp.63-69
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• 2020

In this paper, we propose an indoor positioning technique using the landmark based on relative Access Point (AP) signal strengths. The absolute values of AP signals are used to conventional indoor positioning technologies, but they may be different because of the difference of the measuring device, the measuring environment, and the timing of the measurements. However, we found the fact that the flow of the AP's RSSI in certain places shows almost constant patterns. Based on theses characteristics, we identify the relative strength between the APs and store the certain places as landmarks where they show certain patterns. Once the deployment of the landmark map is complete, system calculate position of user using the IMU sensor of smartphone and calibrate it with stored landmarks. Our system shows 75.2% improvement over technology that used only sensors, and 39.6% improvement over technology that used landmarks that were selected with absolute values.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5496-5505
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• 2012

As the IT industry develops, the smart-phone technology and functions which are actively being studied at the moment greatly influence the entire living environment. With the smart-phone technology and functions, people's interest for the wireless LAN which can be used to get access to the Internet anytime anywhere is gradually increasing. However, since the malicious attacker can easily carry out hacking or approach the contents due to the characteristics of the wireless radio wave, the personal information with a high level of importance for data security is easily exposed due to Spoofing, Denial of Service attack and Man in the Middle attack. Therefore, the demand for security is gradually increasing. In this paper, the safe wireless network service environment is provided by supplementing the vulnerability in regard to Spoofing, Session Hijacking and Man in the Middle attack after executing the client's authentication process, the AP authentication process and the Mobile Agency authentication process with the client's information in the USIM, the AP information and the Mobile Agency information when the client uses the wireless Internet through the Mobile Agency AP access in the smart phone environment.