• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.360-363
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• 2008

현재 통신 시장의 상황은 유무선 통신서비스 시장의 포화, 이동통신 시장의 기존 유선전화 규모 초과, 그리고 유선통신의 서비스 사업자의 영역 확대 도모 등을 특징으로 한다. 유무선 통합 (Fixed Mobile Convergence, FMC) 서비스는 유선통신 사업자를 중심으로 한 비즈니스 모델로 사용자에게 유무선 통신망 종류에 상관없이 일관되고 끊김없는 서비스를 제공하는 것을 목표로 한다. 이동통신망까지 확대하여 고객 기반을 유지하고자 하는 유선사업자들은 FMC 서비스 중 하나의 방안으로 IMS (IP Multimedia Subsystems) 기반의 VCC(Voice Call Continuity) 기능에 주목하고 있다. VCC AS(Application Server)는 이종망 (WiFi-CDMA)간 Seamless 핸드오버기능을 수행하므로, WiFi 와 CDMA를 지원할 수 있는 듀얼단말을 이용하여 사용자가 WiFi 서비스 지역과 CDMA 서비스 지역간 이동시에도 Seamless 한 음성서비스를 제공한다. 이에 본 논문은 IMS/VCC 기반으로 음성 seamless 핸드오버 적용 사례(시범서비스)를 중심으로 유무선 통신사업자 상호 Win-Win을 추구할 수 있는 LG데이콤 특화 VCC 모델을 제시한다. 그리고 LG데이콤이 추구하는 차세대 서비스인 사용자 context 기반의 개인화된 서비스 제공을 위한 IMS 기반 통합 프로파일/인증/과금 연구 동향에 대해 간략히 소개한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.9
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• pp.4341-4348
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• 2012

This paper presents a web-based real-time monitoring system for a photobioreactor using an WiFi wireless network. An WiFi interface can support high speed data transfer, up to 11Mbps and it can be compatible with commercial wireless LAN environment. Thus, the proposed cell culture based on WiFi network can be easily applied to the reconfigurable system and real-time monitoring system. In this paper, we integrate the commercial WiFi module to the various bio-sensors and sensor control board to configure the wireless network. After we evaluate application S/W for monitoring the environment within incubator, we verify the proposed sensor networks for a cell culture system and its monitoring system. This result can be applicable for various bio-applications that require the network configuration and real-time monitoring system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.5
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• pp.592-597
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• 2012

In this paper, a new small chip antenna for Wi-Fi application of the mobile handset is proposed. To miniaturize the chip antenna, the proposed antenna is designed to have the backside ground. The proposed antenna has S-shaped structure, which is designed on the LCP(Liquid Crystal Polymer) with ${\varepsilon}_r$=3.5. The size of the proposed antenna is $6.0mm{\times}2.5mm{\times}1.2mm$. The measured impedance bandwidth under a voltage standing wave ratio (VSWR) of 2 was 300 MHz(fractional bandwidth: 12.2 % 2.3~2.6 GHz), and peak gain is 1.42 dBi. The proposed antenna was designed using CST Microwave Studio commercial software tool. And the fabricated antenna is measured using a network analyzer and in anechoic chamber.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.17-23
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• 2021

In the present study, a more compact dual-band slot antenna is newly proposed for Wi-Fi application. The proposed antenna is composed of rectangular two stepped slot with open end which can generate standing wave resonance at dual frequency bands and L-type microstrip feed line. The measured impedance bandwidths are 50 MHz(2.412 ~ 2.470 GHz) at low frequency band and 452 MHz(5.451 ~ 5.903 GHz) at high frequency band respectiviely. Furthermore its size of 14 × 21 mm² is reduced by 30% compared to the size of 20 × 21 mm² of a conventional similar compact slot antenna. It has the omni-directional radiation pattern characteristics of a typical dipole antenna on the H-Plane, so it is suitable for commercial wireless network applications such as Wi-Fi.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.1
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• pp.70-75
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• 2022

Accurately measuring location is necessary to provide a variety of services. The data for indoor positioning measures the RSSI values from the WiFi device through an application of a smartphone. The measured data becomes the raw data of machine learning. The feature data is the measured RSSI value, and the label is the name of the space for the measured position. For this purpose, the machine learning technique is to study a technique that predicts the exact location only with the WiFi signal by applying an efficient technique to classification. Ensemble is a technique for obtaining more accurate predictions through various models than one model, including backing and boosting. Among them, Boosting is a technique for adjusting the weight of a model through a modeling result based on sampled data, and there are various algorithms. This study uses Xgboost among the above techniques and evaluates performance with other ensemble techniques.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.11
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• pp.3950-3969
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• 2021

Radio Frequency (RF)-based indoor localization technologies play significant roles in various Internet of Things (IoT) services (e.g., location-based service). Most such technologies require that all the devices comply with a specified technology (e.g., WiFi, ZigBee, and Bluetooth). However, this requirement limits its application scenarios in today's IoT context where multiple devices complied with different standards coexist in a shared environment. To bridge the gap, in this paper, we propose a cross-technology localization approach, which is able to localize target nodes using a different type of devices. Specifically, the proposed framework reuses the existing WiFi infrastructure without introducing additional cost to localize Non-WiFi device (i.e., ZigBee). The key idea is to leverage the interference between devices that share the same operating frequency (e.g., 2.4GHz). Such interference exhibits unique patterns that depend on the target device's location, thus it can be leveraged for cross-technology localization. The proposed framework uses Principal Components Analysis (PCA) to extract salient features of the received WiFi signals, and leverages Dynamic Time Warping (DTW), Gradient Boosting Regression Tree (GBRT) to improve the robustness of our system. We conduct experiments in real scenario and investigate the impact of different factors. Experimental results show that the average localization accuracy of our prototype can reach 1.54m, which demonstrates a promising direction of building cross-technology technologies to fulfill the needs of modern IoT context.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.6
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• pp.1343-1349
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• 2014

Recently feature phones are being replaced by smartphones. Because smartphones have various sensors, there are many applications and research works that utilize them. Very few feature phones have GPS modules but all smartphones are equipped with a GPS sensor. One of the hot issues for smartphone research and development is point interest research. In this paper, we will develop an application which protects children using GPS and WiFi.. If a child gets out of the interest-area which is established by parents or guardian, our system sends them messages.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.30-33
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• 2015

In this paper, we proceeded a study on the Hybrid RF based development of the smart phone Application skin disease monitoring using CMOS camera. we proposed an image transfer technology which can use the CMOS camera and we developed the smart phone application which can be possible to use a remote monitoring for skin disease. Image transfer technology using Hybrid RF communication applied for WiFi using CMOS camera. We implemented the function which can use a remote monitoring using Wi-Fi. These suggestion can be a good example for endoscopic applications using hybrid RF based smart phone application of skin disease monitoring using CMOS camera.

• Journal of Advanced Navigation Technology
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• v.15 no.2
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• pp.197-203
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• 2011

A triple-band antenna which can be used at GSM900, PCS1900 and Bluetooth(or Wi-Fi) frequency band is proposed. The proposed antenna is designed based upon switching between IFA(Inverted F Antenna) that has a resonant length of ${\lambda}/4$ and loop antenna that has a resonant length of ${\lambda}/2$. It can be applied to triple-band only by use of single printed pattern due to the switching characteristic. It is designed by use of the IFA for the application to the GSM900, while it is designed by use of the loop antenna for the application to the PCS1900 and by use of additional pattern of IFA for the application to the Bluetooth(or Wi-Fi) respectively. As a result, it has been observed that the proposed antenna satisfies the required return loss(${\leq}10dB$) and also has efficiency(${\geq}80%$) over the whole band. Moreover the proposed antenna has omni-directional radiation pattern which is suitable to apply to the mobile phone.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1554-1557
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• 2020

Looking at the direction of the recent amendments of 802.11 family, there are two major trends. One is to enable the wireless transceivers to support the extremely high-speed wireless transmissions, which has been the mainstream so far. Another big trend is providing a high-performance wireless application platform that meets the demands of the market. This paper summarizes the brand-new IEEE 802.11 amendments from 11ax to 11bf under development by analyzing the innovative features and use cases on them. We provide the vision and direction for the research on the revolutionary data-hungry Wi-Fi 6 and the IEEE 802.11be, alias Wi-Fi 7.