• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.449-452
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• 2018

In this paper, we design a Wibro / WiFi dual band microstrip antenna for wireless broadband communication. The proposed antenna is designed to have the characteristics of FR-4 (er = 4.3), size of $40[mm]{\times}40[mm]$, and usable in 2.31[GHz] and 5.8[GHz] bands of Wibro / WiFi. The simulation is performed by CST Microwave Studio 2014 The simulation result shows that the gain is 2.308[dB] at 2.31[GHz] and 2.985[dB] at 5.8[GHz]. S-parameters were also found to be less than -10[dB] (WSWR2: 1) in the desired frequency band, and a small number of parameters and a compact antenna were designed. It is expected that many users will use the mobile communication antenna for accurate and fast communication for smooth wireless broadband communication.

• 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.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.07a
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• pp.63-64
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• 2012

본 논문에서는 소형 무인 비행체 (Unmanned Aerial Vehicle, UAV)를 스마트폰을 이용하여 제어하기 위한 방법을 제안하고. UAV에 Wi-Fi 통신 모듈 설계 및 개발 과정을 설명한다. 스마트폰과 UAV는 Wi-Fi를 통해 통신하며, 이것의 instruction set은 MCU에서 C언어로 다운로드 된 로직으로 수행하게 된다. 데이터의 송수신은 Serial 포트를 이용하여 흐름을 제어하며 확인할 수 있다. 또한 관련 모듈들을 통합하기 위해 PCB(Printed Circuit Board)과정을 진행, 소형화하여 개발하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.8
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• pp.18-25
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• 2020

With the development of water internet technology, data communication between objects is expanding. Research related to data communication technology between vehicles that incorporates related technologies into vehicles has been actively conducted. For data communication between mobile terminals, data stability, reliability, and real-time performance must be guaranteed. The 5 GHz Wi-Fi band, which is advantageous in bandwidth, communications speed, and wireless saturation of the wireless network, was selected as the data communications network between vehicles. This study analyzes how to design and implement a 5 GHz Wi-Fi network in a vehicle network. Considering the characteristics of the mobile communication terminal device, a continuous variable communications structure is proposed to enable high-speed data switching. We simplify the access point access procedure to reduce the latency between wireless terminals. By limiting the Transmission Control Protocol Internet Protocol (TCP/IP)-based Dynamic Host Configuration Protocol (DHCP) server function and implementing it in a broadcast transmission protocol method, communication delay between terminal devices is improved. Compared to the general commercial Wi-Fi communication method, the connection operation and response speed have been improved by five seconds or more. Utilizing this method can be applied to various types of event data communication between vehicles. It can also be extended to wireless data-based intelligent road networks and systems for autonomous driving.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.34-41
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• 2011

At present wireless internet access service is available through the 3G network, mobile WiMAX and WiFi anytime and anywhere. In this environment where there are various networks, users should be able to select specific networks depending on different situations. And it is necessary to provide mobility support between homogeneous and between heterogenous networks. Given this situation, the many proposals have been presented to link 3G, which has the largest service area among various networks, with mobile WiMAX(IEEE 802.16e), or with WiFi(IEEE 802.11). But, recently, with the increasing volume of wireless internet use and wireless internet data, due to the advents of net-book, e-book and smart phone, the service area of WiFi and mobile WiMAX has rapidly expanded. Especially, the availability of real-time application such as internet phone has led to the relative shrinking of the proportion of 3G mobile communication network giving conventional voice service, and enlargement of those of wireless internet access networks like WiFi and mobile WiMAX. This paper suggests a handover scheme based on PMIPv6, whitch support mobility between WiFi and mobile WiMAX, and minimizes handover delay. In this scheme, the mobile node has a dual stack structure composed of two interfaces-WiFi and mobile WiMAX. Since WiFi dose not support mobility, it is suggested that the mobile node have the capacity to deal with handover signaling between gateway in case of handover between homogeneous networks. This handover scheme, suggested comparing with current handovers between homogeneous networks, has proved, in its analytic evaluation, to be able to reduce handover, transmission, and signaling overhead.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.131-136
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• 2012

In these days, with the diffusion of mobile equipments, the number of WiFi Access Point (AP) is increasing, and the growth of WiFi AP causes the throughput degradation due to interferences between APs. This recent phenomenon demands the method able to be utilized with current WiFi network to improve the throughput of Wireless LANs. This paper studied the channel assignment method and several throughput enhancement methods to optimize Radio Resource Management (RRM) for distributed infrastructure WLANs. As a result, it was able to put AP independently, improve older allocation error, and improve execution speed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.3
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• pp.13-19
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• 2014

Improvement of performances of potable communication devices such as laptops, tablets, and smart-phones enables people to do group meetings in any place. However, even though group members in a meeting locate close, data or information to be shared in the group are exchanged through the cellular networks. This increases unnecessary traffic loads in the wireless/backbone networks and as consequence it increase delays in communications. To resolve the problem, an android-based application is developed in this paper. The application utilizes Wi-Fi Direct so that all members in the meeting can direct exchange materials for the meeting without using cellular networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.565-573
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• 2016

Wi-Fi Direct standard technology(Wi-Fi Peer to Peer Technical Specifications v1.2, 2010) was designed for allowing peer to peer communication between two or more devices and various products which have been currently manufactured such as smart phone and smart TV have already provided this technical function. In this technology the role of Coordinator in Wi-Fi infrastructure would be matched to GO(Group Owner) which needs relatively high energy resource and computation power due to the high probability for allowing 3rd-party connection, however, the current standard specification would be limited in terms of energy distribution because it has not included a process to determine the role of GO. To address above problem, this paper classified considerable parameters into the general parameters for the physicality of devices and the specific parameters for considering the role position depending on use-case scenario, and proposed a new method called DIVA to help efficiently determining GO role from the member devices of Wi-Fi Direct network. Furthermore the effect of this mechanism was proved via simulation-based experiments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.105-111
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• 2017

In this paper, the analysis results are shown about several weights of Weighted K-Nearest Neighbor method, Recently, it is employed for the indoor positioning technologies using WiFi fingerprint which has been actively studied. In spite of the simplest feature, the W-KNN method shows comparable performance to another methods using WiFi fingerprint technology. So W-KNN method has employed in the existing indoor positioning system. It shows positioning error performance according to data preprocessing and weight factor, and the analysis on the weight is very important. In this paper, based on the real measured WiFi fingerprint data, the estimation error is analyzed and the performances are compared, for the case of data processing methods, of the weight of average, variance, and distance, and of the averaging several position of number K. These results could be practically useful to construct the real indoor positioning system.

• Journal of Internet Computing and Services
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• v.14 no.4
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• pp.13-24
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• 2013

IEEE 802.15.4 network and WiFi network are installed to overlap each other and configured to use adjacent frequency bands in which case the communication service required by applications can not be guaranteed because of randomly increased frame transmission delay and frequent frame transmission failures at nodes in IEEE 802.15.4 network. In this paper, transmission delay model at IEEE 802.15.4 nodes and an experimental system to evaluate the interference from WiFi traffic are described, then elements for the evaluation of interference are measured with the analysis of their characteristics. A sequential method of using medium access layer and physical layer elements of IEEE 802.15.4 protocols is proposed to decide interference from WiFi network. With the proposed method, if an evaluation function having frame transmission failures and transmission delay as variables returns a value greater than a threshold, intensive measurements of wireless channel power are carried out subsequently and the final decision of interference is made by the calculated average channel power. Experimental results of the method show that the decision time is reduced with increased frequency of decision in comparison to an other similar method.