• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.129-134
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• 2018

Research on the technique for estimating the indoor position has been actively carried out. In particular, the WiFi fingerprint method, which does not require any additional infrastructure, is being partially used because of its high economic efficiency. The KNN method which estimates similar points to the corresponding points by comparing intensity information of the WLAN reception signal measured at various points in advance with intensity information measured at a specific point in the future is simple but has a good performance. However, in the conventional KNN scheme, since the number K of average candidate positions is constant, there is a problem that the position estimation error is not optimized according to a specific point. In this paper, we proposed an algorithm that adaptively changes the K value for each point and applied it to experimental data and evaluated its performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1373-1392
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• 2017

WiFi Direct (WD) is a state of the art technology for a Device-to-Device (D2D) communication in 802.11 networks. The performance of the WD system can be significantly affected by some key factors such as the type of application, specifications of MAC and PHY layer parameters, and surrounding environment etc. It is, therefore, important to develop a system model that takes these factors into account. In this paper, we focus on investigating the design parameters of the PHY layer that could maximize the efficiency of the WD 802.11 system. For this purpose, a basic theoretical model is formulated for a WD network under a 2x2 Multiple In Multiple Out (MIMO) TGn channel B model. The design level parameters such as input symbol rate and antenna spacing, as well as the effects of the environment, are thoroughly examined in terms of path gain, spectral density, outage probability and Packet Error Rate (PER). Thereafter, a novel adaptive algorithm is proposed to choose optimal parameters in accordance with the Quality of Experience (QoE) for a targeted application. The simulation results show that the proposed method outperforms the standard method thereby achieving an optimal performance in an adaptive manner.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2665-2668
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• 2003

초고속 인터넷 망의 발전과 함께 네트워크를 통한 전체 시스템의 통합관리 및 감시가 가능해지고 있다. 본 논문에서는 Windows CE 기반의 무선 인터넷 서비스를 이용한 감시 시스템을 구현하였다. 각각의 웨이블릿 인코더를 가진 원격지 카메라를 이용하여 압축한 데이터를 802.11b(Wi-Fi) 무선 랜 망을 사용하여 전송하고, 전송된 9 채널의 영상 데이터를 각 채널별로 웨이블릿 디코더를 이용하여 압축을 풀고, 고속 데이터 버스를 이용하여 동시에 화면에 디스플레이 하였다. 이러한 시스템을 구현하기 위하여 Geode GXl 프로세서 기반의 Windows CE 서버시스템을 구현하였고, FPGA를 이용하여 9 개의 웨이블릿 디코더를 통하여 입력된 영상 데이터를 제어하였고, 실시간 디스플레이가 가능하도록 하였다. 그리고, Windows CE 기반의 PCI 디바이스를 제어하기 위한 디바이스 드라이버 및 응용 소프트웨어를 작성하였다.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2513-2515
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• 2003

본 논문에서는 Windows CE 기반의 무선 인터넷 서비스를 이용한 감시 시스템을 구현하였다. 원격지 카메라를 이용하여 압축한 데이터를 802.11b (Wi-Fi) 무선 랜망을 사용하여 전송하였다. 그리고, 고속 데이터 버스를 이용하여 전송된 영상 데이터를 웨이블릿 디코더를 이용하여 압축을 풀고 화면에 디스플레이 하였다. Geode GXI프로세서 기반의 Windows CE 서버 시스템을 구현하였고, FPGA를 이용하여 레이블릿 디코더를 제어하여 영상 데이터를 실시간 디스플레이가 가능하도록 하였다. 그리고, Windows CE 기반의 디바이스 드라이버 및 응용 소프트웨어를 작성하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1856-1864
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• 2015

In this paper, the localization algorithm for improving the accuracy of the positioning using the Wi-Fi fingerprint using the normal distribution probability and the built-in typed accelerometer sensor, the gyroscope sensor of smartphone in the indoor environment is proposed. The experiments for analyzing the performance of the proposed algorithm were carried out at the region of the horizontal and vertical 20m * 10m in the engineering school building of our university, and the performance of the proposed algorithm is compared with the fingerprint and the DR (dead reckoning) while user is moving according to the assigned region. As a result, the maximum error distance in the proposed algorithm was decreased to 2cm and 36cm compared with two algorithms, respectively. In addition to this, the maximum error distance was also less than compared with two algorithms as 16.64cm and 36.25cm, respectively. It can be seen that the fingerprint map searching time of the proposed algorithm was also reduced to 0.15 seconds compared with two algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.7
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• pp.553-563
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• 2013

When the IEEE 802.11 wireless LAN-based broadcasting services, we use broadcast packets to broadcast multimedia contents to a large number of users using limited wireless resources. However, broadcast transmission is difficult to recover the loss packets compared with unicast transmission. Therefore, analysis of packet loss characteristics is required to perform efficient packet recovery. The packet loss in wireless transmissions is often bursty with high loss data rate. Even if loss patterns have the same average packet loss, they are different in the recovery rate of random loss and burst loss depending on the nature. Therefore, the analysis and research of the nature of the loss are needed to recover loss packets considering bursty characteristics. In this paper, we experimented Wi-Fi broadcast transmission according to transmission rate and analyzed bursty characteristics of loss patterns using 4-state markov model.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.422-424
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• 2010

Recently the car attached many ECUs and entertainment devices to provide the easiness maintenance and driver's convenience. CAN and MOST networks have been used to manage and control those devices in the car. Wireless network also has been established to receive information from external. These days a car navigation system with GPS is being integrated with CAN, MOST and Wireless network. In these circumstances, the car navigation system can have HMI function to integrate and control the car networks' devices. To solve the GPS problems such as positioning errors or losing signals from satellites in the tunnels and urban canyons, this paper designs and implements a method for positioning vehicle by using the sensing data of sensors and Wi-Fi devices based on this integrated environment.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.33-38
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• 2016

As a communications system and using the wireless devices is increased at the world, the interference among devices at 2.4GHz band become issue. New complex content technology as education, concert, broadcast, thema-park are developed between Virtual Reality technology and tradition. That is expect an annual growth rate of more than 14%. Almost Virtual Reality devices use motion sense or a wireless joystick. Therefore it is necessarily to analyze the coexistence between Virtual Reality devices and Wi-Fi in the ISM band. The interference scenario and propagation of the Extended Hata Model was established to analyze the interference from WLAN into Virtual Reality devices. Through simulation results based on Monte-Carlo principle, separation frequency was obtained to protect WLAN interference from Virtual Reality devices.

• Journal of Practical Engineering Education
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• v.13 no.2
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• pp.321-326
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• 2021

Wireless communication is a core technology constituting the Internet of Things (IoT), but there is no suitable educational equipment to learn various wireless communication technologies used in the Internet of Things through practice. This paper deals with the development of advanced education and training equipment that can perform various IoT wireless communication practices. It uses an Arduino mega board as a device to control various sensors. As wireless network technologies to send and receive the sensing date wirelessly, it makes use of RFID/NFC and Bluetooth among WPAN technologies, WiFi among WLAN technologies and LoRa and 2.4GHz wireless transceiver among WWAN technologies. In addition, GPS, infrared communication, I2C communication, and SPI communication are organized so that various IoT wireless communication technologies can be learned through practice. In addition, since the educational equipment developed in this paper is equipped with two devices, it is designed to perform transmission and reception experiments for wireless network technology within the equipment.

• Journal of Advanced Navigation Technology
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• v.25 no.6
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• pp.536-542
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• 2021

In this paper, we proposed a triple band printed monopole antenna with a bent branch strips for WiFi / 5G. An antenna structure in which bent strips for generating multiple resonance are attached in the form of branches was newly proposed based on a typical monopole strip vertically erected as a triple band antenna structure. The proposed antenna is designed on a FR-4 substrate with dielectric constant 4.3, thickness of 1.6 mm, and size of 28×40 mm². The measured impedance bandwidth is 430 MHz (2.22~2.65 GHz) in the 2.4 GHz WLAN, 450 MHz (3.38~3.83 GHz) in the 3.5 GHz and 2390 MHz (4.95~7.34 GHz), In particular, it has been observed that antenna has a stable omnidirectional radiation patterns as well as gain of 1.537 dBi, 1.878 dBi and 2.337 dBi in the entire frequency band of interest.