• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.3
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• pp.336-342
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• 2008

This paper suggests a CPW-fed UWB antenna with new hexagonal slot. To increase the impedance bandwidth of an antenna, the proposed antenna is designed with the hexagonal patch. Polygonal slot is inserted in the hexagonal patch to avoid interference with IEEE 802.11a. The proposed antenna was fabricated on FR-4 substrate with a relative dielectric constant 4.7 and thickness of 1.6 mm and measured for VSWR Characteristic and group delay. The fabricated antenna shows that the gain flatness is 4 dBi except at the band for IEEE 802.11a.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.882-885
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• 2008

Recently, various types of wireless networks have been proliferated. Bluetooth, IEEE 802.11 WLAN, 802.16e Mobile WiMAX (or Wibro) and 3G celluar networks are some examples. Accordingly, research on seamless mobility support mechanisms among homogeneous or heterogeneous networks has drawn significant interests. This paper examines recent research efforts on seamless mobility support mechanisms from link to transport layer. Yet, no single solution meets all the requirements for supporting the seamless mobility and it seems hard to tell which layer is the most appropriate one for supporting mobility. This area is still wide open and needs further research.

• Information and Communications Magazine
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• v.25 no.3
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• pp.60-63
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• 2008

WiBro 기술이 IEEE 802.16e 표준으로 채택되기까지의 과정은 크게, 국내표준이 우선되던 단계(2002. 11$\sim$2004. 6.)와 IEEE 802.16을 중심으로 국제표준에 힘쓰던 단계(2004. 7.$\sim$2005. 12.)으로 나누어서 볼 수 있다. 첫 번째 단계는 정부에 의한 비활성화된 2.3-2.4 GHz WLL용 주파수 대역의 회수 및 활용을 위한 WiBro 개념의 도입부터, ETRI를 중심으로 한 연구개발 프로젝트의 추진, TTA 내의 PG302 프로젝트그룹의 결성 및 적극적 국내표준화 활동을 통한 표준초안의 개발까지의 과정에 해당된다. 이 과정에서 개념의 창출부터, 요구사항의 정의, 방식의 선정, 규격 초안의 개발까지의 과정을 독자적으로 수행하였으며, 독자 기술에 의한 국내 기술의 개발 및 표준화를 바탕으로 국제표준화를 추진하기 위한 꿈과 도전의 시기였다고 할 수 있다. 두 번째 단계는 규모의 경제의 실현 및 국제표준의 중요성에 대한 인식에 따른 IEEE 802.16e를 중심으로 한 국제표준화의 추진을 통한 표준 IPR의 확보 및 시험 규격 등 제반 규격의 정비 등 세계 최초 상용화를 위한 표준선도의 시기였다고 할 수 있다. 나름 아쉬움이 없는 것은 아니나, 우리 힘으로 여러 난관들을 극복하고 상용화 및 IMT-2000 국제표준채택을 통한 세계화의 실현 등을 위한 성숙의 시기였다고 할수 있다. 이제 4세대 이동통신 표준화에서도 대한민국이 주도적인 역할을 수행해야 할 때이다. 좀 더 우리의 역량을 결집하고 발휘할 수 있도록 지혜를 발휘하여야 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.80-83
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• 2010

As the recent development of mobile technology, users want to multi-service in anytime, anywhere, any terminal. To meet the needs of users, it causes a lot of expense that redesign of the entire network or expand the network of services areas. Therefore, IEEE, IETF is offering Handover technology between Heterogeneous Network. In this paper, the IEEE 802.21 MIH Information Server is based on the network. It proposes an improved Handover that L3 layer to optimize the Handover process use of FMIPv6 and executes simulation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.91-96
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• 2019

There are so many low power MAC protocols for wireless sensor network. IEEE802.15.4 among them has disadvantage of a large power consumption for synchronization. To save power consumption it use the superframe operation alternating sleep mode and awake mode. But latency is longer result from superframe operation. Typical asynchronous B-MAC can have shorter latency according to check interval. But transmitter consumes more power because of long preamble. And receiver is suffering from overhearing. In this paper, we propose the adaptive check interval scheme of B-MAC for enhancing the power consumption and delay latency performance. Its power consumption is evaluated by comparing the proposed scheme with a typical IEEE802.15.4.

• Journal of the Korea Society of Computer and Information
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• v.16 no.12
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• pp.227-234
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• 2011

Many technologies for wireless internet are increasing as more and more laptop computers, net books, smart phone and other terminals, which provide wireless network, are created. IEEE 802.11 is computer wireless network technology that used in small area, called wireless LAN or Wi-Fi. IEEE 802.11 is a set of standards for implementing wireless local area network (WLAN) computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee (IEEE 802). AP (Access Point) is installed at cafes and public places providing wireless environment. It is more convenient to use wireless internet, however, It can be seen easily around us and possible to communicate with AP. IEEE 802.11 has many vulnerability, such as packet manipulation and information disclosure, so we should pay more attention when using IEEE 802.11. Therefore this paper developing monitoring system which can find out AP and Stations that connect with it, and capturing AP's information to find out vulnerability. This paper suggests monitoring system which traffic analysis in wireless environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.232-239
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• 2011

IEEE 802.11n standard provides a framework for new link adaptation. A station can request that another station provide a Modulation and Coding Scheme (MCS) feedback, to fully exploit channel variations on a link. However, if the time elapsed between MCS feedback request and the data frame transmission using the MCS feedback becomes bigger, the previously received feedback information may be obsolete. In that case, the effectiveness of the feedback-based link adaptation is compromised. If a station can estimate how fast the channel quality to the target station changes, it can improve accuracy of the link adaptation. The contribution of this paper is twofold. First, through a thorough NS-2 simulation, we show how the coherence time affects the performance of the MCS feedback based link adaptation of 802.11n networks. Second, this paper proposes an effective algorithm for coherence time estimation. Using Allan variance information statistic, a station estimates the coherence time of the receiving link. A proposed link adaptation scheme considering the coherence time can provide better performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.186-188
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• 2014

In recent years, domestic as well as LTE wireless network of Wi-Fi and most used. In addition, mobile-intensive services that used mainly in our society makes it easier, SNS, application (APP), and file downloads. As such, the amount of data requested, while living at the time of mobile users will want to be safe from the earliest. And the wireless network communications mortality (3G, 4G (LTE), LTE-A) and Wi-Fi (802.11 n-2.4 G H z z H a c-5, 802.11 G), and users are mainly used in the death 4G (LTE), communication Wi-Fi, 802.11 n-2.4 GHz are used most frequently. As above, use the wireless network in order to safely and quickly developed the technology of the Li-Fi. Li-Fi light (visible light) technology to communicate with, and Wi-Fi (802.11 n-2.4 G z H) 100 times faster, LTE-A 66 times faster. However, the current Li-Fi to commercialise the big issue exists. In this paper, there are a lot of existing problems in the commercialization of Li-Fi being used in Wi-Fi, and a comparative analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.10A
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• pp.965-970
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• 2005

In this paper, SPDT Tx/Rx MMIC switch applicable to IEEE 802.11a WLAN systems is designed and fabricated using a specific designed epitaxial layered pHEMT wafer and ETRI's $0.5{\mu}m$ pHEMT switch process. The SPDT switch exhibits a low insertion loss of 0.68dB, high isolation of 35.64dB, return loss of 13.4dB, power transfer capability of 25dBm, and 3rd order intercept point of 42dBm at frequency of 5.8GHz and control voltage of 0/-3V. The comparison of the measured performances with commercial products based on the GaAs pHEMT technology for low voltage operating at ${\pm}$ 3V/0V shows that the return loss is somewhat inferior to the commercial products and insertion loss is compatible with each other however, isolation characteristics are much better than in conventional chips. Based on these performances, we can conclude that the developed SPDT switch MMIC has an enough potential for IEEE802.11a standard 5 GHz-band wireless LAN applications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.985-988
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• 2005

The international standards of high-rate WPAN (Wireless Personal Area network) are under development by IEEE802.15 WPAN TG3 (Task Group 3). The study area of TG3 mainly consists of three parts: high rate physical and media access control layer in 2.4GHz ISM (Industrial Scientific Medical) non licensed frequency band; an alternative high rate physical layer by using UWB (Ultra Wide Band); and another alternative high rate physical layer based on millimeter wave. This paper describes the standardization trends of UWB and millimeter wave.