• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.667-669
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• 2003

IEEE 802.11 표준에 포함되어 있는 WEP 방식의 무선 랜 보안이 취약한 것으로 알려진 후 WEP을 대치할 새로운 표준이 802.1li 워킹그룹에 의하여 작성되고 있다. Wi-Fi는 중간단계로서 802.1li의 일부만을 구현하는 WPA 규격을 만들었다. 이 규격은 기존의 하드웨어를 그대로 사용하면서 소프트웨어와 펌웨어 갱신만으로 기존의 무선랜 취약점을 제거할 수 있게 한다. WPA규격을 준수하는 무선 랜 액세스포인트의 개발을 위하여 기존의 액세스포인트 디바이스 드라이버를 WPA를 지원하도록 수정하였으며, 사용자 인증 및 키 교환을 수행하는 소프트웨어를 설계 및 개발하였다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.19-24
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• 2010

This paper proposes a unified time-domain channel estimator (UTD-CE) for ubiquitous wireless broadband access based on orthogonal frequency division multiplexing (OFDM) systems. As a part of a software radio platform for ubiquitous services, the proposed UTD-CE can be exploited with the simply changeable parameters, pilot symbols and pilot subcarriers allocation, which are usually different according to the system specifications such as IEEE802.11x WiFI, IEEE802.16x WiMAX, DMB, Media FLO, DVB-H, etc. Given the pilot information, the channel frequency responses (CFRs) of data subcarriers will be analogously estimated by Wiener filtering and discrete Fourier transform (DFT)-based interpolation in the UTD-CE. Simulation results indicate that the proposed method significantly outperforms the conventional time-domain channel estimator when the pilot information is changed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1911-1932
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• 2013

Orthogonal frequency-division multiplexing (OFDM) has become a popular modulation scheme for wireless protocols because of its spectral efficiency and robustness against multipath interference. Although the components of various OFDM protocols are functionally similar, they remain distinct because of the characteristics of the environment. Recently, graphics processing units (GPUs) have been used to accelerate the signal processing of the physical layer (PHY) because of their great computational power, high development efficiency, and flexibility. In this paper, we describe the implementation of parameterized baseband modules using GPUs for two different OFDM protocols, namely, 802.11a and 802.16. First, we introduce various modules in the modulator/demodulator parts of the transmitter and receiver and analyze the computational complexity of each module. We then describe the integration of the GPU-based baseband modules of the two protocols using the parameterized method. GPU-based implementations are addressed to explain how to accelerate the baseband processing to archive real-time throughput. Finally, the performance results of each signal processing module are evaluated and analyzed. The experiments show that the GPU-based 802.11a and 802.16 PHY meet the real-time requirement and demonstrate good bit error ratio (BER) performance. The performance comparison indicates that our GPU-based implemented modules have better flexibility and throughput to the current ones.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.6
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• pp.223-229
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• 2023

This papart proposes single pole double throw (SPDT) switch with six-stage radial stub resonators in the 3.6~4.0 GHz band. The switch was simulated using ADS (Advanced Design Software), a design tool for the wireless communication circuits, and evaluated on a pcb substrate. The measurement results of the radial SPDT switch showed an average 90 dB isolation, and 1.5 dB insertion loss. This isolation characteristic was 20 dB superior to higher than those laboratory or commercial products reported thus far. The proposed SPDT switch is applicable to multi-band RF front-end systems, such as WiMAX, LTE/5G, Wi-Fi, and HyperLAN.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.10a
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• pp.19-20
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• 2018

This paper distinguish between the types of LANs used to connect the internet used by many in the fourth industrial era and compare speeds. 802.11 is fastest and it's running at 300Mbps. And second fastest is running at 54Mbps. In compare second, 802.11n is faster second at six times. So we can prediction the wireless lan's transmission speed will be faster in future.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11c
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• pp.1941-1944
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• 2003

IEEE 802.11 표준에 포함되어 있는 WEP 방식의 무선랜 보안이 취약한 것으로 알려진 후, WEP을 대치할 새로운 표준이 802.11i 워킹그룹에 의하여 작성되고 있으며, Wi-Fi 는 중간단계로서 802.11i의 일부만을 구현하는 WPA 규격을 만들었다. WPA 규격 중 TKIP 알고리즘을 디바이스 드라이버에 소프트웨어로 구현한 액세스포인트와 펌웨어에 구현한 액세스포인트를 개발하여, 시험을 통하여 성능을 비교 분석하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.5
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• pp.1154-1159
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• 2013

Now we are facing various threats as side effects against the growth of smartphone markets. Malicious codes such as mobile worms may bring about disclosures of personal information and confusions to upset a national wireless backbone. In this paper, we examine the existed spreading models and try to describe the correct spread of mobile worms on smartphones. We also analyze the spreading effects, and simulate bluetooth, MMS and Wi-Fi worms by various experiments.

• KIPS Transactions on Computer and Communication Systems
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• v.13 no.1
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• pp.21-30
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• 2024

As the self-driving car market continues to grow, the need for charging infrastructure is growing. However, in the case of a wireless charging system, stability issues are being raised because it requires a large amount of power compared with conventional wired charging. SAE J2954 is a standard for building autonomous vehicle wireless charging infrastructure, and the standard defines a communication method between a vehicle and a power transmission system. SAE J2954 recommends using physical media such as Wi-Fi, Bluetooth, and UWB as a wireless charging communication method for autonomous vehicles to enable communication between the vehicle and the charging pad. In particular, UWB is a suitable solution for indoor and outdoor charging environments because it exhibits robust communication capabilities in indoor environments and is not sensitive to interference. In this standard, the process for building a wireless power transmission system is divided into several stages from the start to the completion of charging. In this study, UWB technology is used as a means of fine alignment, a process in the wireless power transmission system. To determine the applicability to an actual autonomous vehicle wireless power transmission system, experiments were conducted based on distance, and the distance information was collected from UWB. To improve the accuracy of the distance data obtained from UWB, we propose a Single Model and Multi Model that apply machine learning and deep learning techniques to the collected data through a three-step preprocessing process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7B
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• pp.578-585
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• 2012

Location tracking system through GPS and Wi-Fi is available at no additional cost in an environment of IEEE 802.11-based wireless network. It is useful for many applications in outdoor environment. However, a previous systems used for general device to tag. It is unsuitable for power aware location tracking system because general devices is more expensive and non-optimized for tracking. The hand-off method of IEEE 802.11 standard is not enough considering power consumption. This thesis analyzes the previous location tracking systems and proposes power aware system. First, we designed and implemented tag to optimize location tracking. Next, we propose low-power hand-off method and low-power behavior model in implemented tag. The proposed hand-off method resolve power problem by using the location information and behavior model minimize power consumption of tag through power-saving mode and the concept of duty cycle. To evaluating proposed methods and system performance, we perform simulations and experiments in real environment. And then, we calculate tag's power consumption based on the actual measured current consumption of each operation. In a simulation result, the proposed behavior model and hand-off method reduced about 98%, 59% than the standard's hand-off and default behavior model.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1255-1261
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• 2010

An operating information and fault recode of train is very important information for safety driving and maintenance. And these information is increased and need high speed as the number of trains is increased. Wireless LAN or CDMA network is efficient to report more complicated and various information from vehicle to server in control center. Existing wireless transmission system has weakness due to transmission system is separated with TDCS and standalone. At first, standalone system needs space to be installed and cost is increased. And data transmission capacity and speed is limited by complicated structure that transmission system receive data thru serial communication like RS232 and then data transmission system send data to server in control center. This article is study to develop embedded & wireless fault code transmission device to be installed in TDCS to overcome weakness of space and to have more cost effective and simple structure. It is adapted 802.11b/g WiFi for wireless communication and OS is used embedded Linux that can easily implement wireless communication environment and ensure TCP/IP communication’s security. We also implement simple server to test wireless communication between embedded & wireless fault code transmission device and server in control center.