• Journal of Communications and Networks
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• v.13 no.2
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• pp.86-94
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• 2011

In recent years, there has been a rise in epidemiological evidence suggesting the health benefits of a physically active lifestyle. However, it is not always easy for individuals to personally recognize the optimal conditions for exercise and physical activity. Wearable acceleration-based pedometers have become widely used in estimating the amount of physical activity, and to a limited extent, providing information regarding exercise intensity, but they have never been used to assess adaptation to exercise. In order to realize simultaneous activity monitoring for multiple users exercising outdoors, we developed a prototype wireless local area network (WLAN) based system. In our system, a WLAN is deployed outside, and a user wearing a smart phone and monitoring device exercises freely within the coverage area of the wireless network. By doing so, the developed system is able to monitor the activity of each user andmeasures various parameters including those related to exercise adaptation. In a demonstration experiment, the developed system was evaluated and used to monitor users enjoying a Nordic walk, after which users were immediately able to receive their exercise report. In this paper, we discuss the requirements and issues in developing an activity monitoring system and report the findings we obtained through the demonstration experiment.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.96-99
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• 2002

The dual band meandered PIFA has been designed, fabricated, and measured. The measured impedance bandwidth is 9.24% @2.45㎓ (2.27-2.49㎓) and 16.33% @5.75㎓(4.95-5.83㎓), repectively. The radiation patterns are similar to those of a typical PIFA. The antenna gains of each resonant frequencies are 5.06(@2.38㎓), 5.95(@5.39㎓) ㏈i respectively.

• Electronics and Telecommunications Trends
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• v.17 no.4 s.76
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• pp.1-15
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• 2002

최근 통신 사업자(WISP)들은 공항, 아파트 등 핫스팟 지역에서 무선랜을 공중 액세스망으로 이용한 초고속 무선인터넷 서비스 네트워크를 구축하고 있다. 이러한 가운데 무선랜에서의 보안 결함이 밝혀지고, 무선랜 환경에서의 개인 프라이버시 침해 문제가 사회적인 현안으로 등장하였다. 본 고에서는 무선랜 기반 공중 액세스망의 보안성 강화를 위하여 국제 표준화기구에서 논의하고 있는 가입자 인증 및 키관리 기술의 동향과 향후 전망에 대해서 분석해 보고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.406-408
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• 2004

인터넷 보안에 대한 중요성이 나날이 증가하고 있으며. 이러한 인터넷 보안 문제의 해결책으로 개발된 IPSec은 IP 계층에서 보안서비스를 제공하기 위하여 AH와 ESP를 사용하여 보안연계(Security Association) 서비스를 제공한다. 본 논문에서는 32-bit 데이터 베이스를 이용하여 새로운 AES로 채택된 Rijndael 암호 알고리즘과 HMAC-SHA-1 인증 알고리즘을 통합시킨 IPSec 암호 프로세서를 구현하였다. Xilinx ISE 5.2i를 사용하여 VHDL로 설계하였고, ModelSim으로 시뮬레이션 검증을 수행하였으며, Xilinx사의 Vertex XCV1000E로 구현하였다. 본 논문에서 구현한 IPSec 암호 프로세서는 WLAN이나 VPN, Firewall등에 응용될 수 있을 것이다.

• TTA Journal
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• s.99
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• pp.123-130
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• 2005

초고속 무선인터넷에 대한 요구가 급성장하면서 기존의 무선랜(WLAN: Wireless Local Area Network) 시스템이 초고속 무선인터넷의 기반구조로써 자리잡고 있음은 주지의 사실이다. 그러나 합리적인 가격과 편리성에도 불구하고 보안의 취약성이 문제로 남아있었다. 이 문제의 해결을 위한 노력의 결실로써 IEE 802.11i 표준은 지난 2004년 6월 24일에 IEEE802 SEC(Sponsor Executive Committee)의 투표를 통과하여 2004년 7월에 IEEE 표준으로 확정되었다[2]. 또한 신속한 국제표준화를 위해서 ISO/IEC JTC1 Fast Track DIS(Draft International Standard)로 상정되어 2004년 12월 8일부터 최종 승인을 위한 투표를 진행 중이다[5]. 본 고에서는 IEEE 802.11i 무선랜 보안 표준이 담고 있는 인증 방식, 키 교환 방식 및 암호 알고리즘에 대하여 분석해 보고자 한다.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.549-551
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• 2002

A Wireless Local Area Network (WLAN) is a flexible data communication system implemented as an extension to, or as an alternative for, a wired LAN with in a building or campus. However, communications in an indoor environment present problems not encountered in outdoor wireless communication systems. Since cellular type systems are interference limited, the indoor environment is more hostile than the outdoor environment due to the lower propagation constant. In this paper, the equation for the signal to interference ratio in a multistory building will be derived. Knowing the S/I ratio, the floor frequency reuse can be determined. Finally, the simulation in this research is designed to study the performance (BER) of WLAN system in the multistory environment by applying the 8-PSK Trellis Coded modulation technique. The procedure allows a quick evaluation of BER in Wireless LAN system due to the co-channel interference.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.223-228
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• 2008

Recently, various types of wireless access networks, such as WLAN, WiBro and HSDPA, etc, have been successfully deployed by commercial service providers (i.e., KT, KTF). In this situation, there are many efforts to provide high quality of services to guarantee seamless mobility between heterogeneous networks. The IP layer mobility protocols are efficient mechanisms to provide seamless mobility between IP based heterogeneous networks as well as homogeneous networks. However, to apply IP mobility protocols in real heterogeneous networks (i.e., WiBro and HSDPA), we must consider not only the basic features of techniques of wireless access networks (i.e., Data rate, Coverage, Quality of Service) but also the problem of real environment of service provider (i.e., Expanse cost to change the access network). Due to this reason, it is difficult to satisfy required conditions by using only one IP mobility protocol in real heterogeneous networks. Therefore, in this paper, we propose an efficient mobility protocol to solve the complex problems that are occurred in real heterogeneous networks. The proposed protocol, so-called, "Hybrid Mobile IP" tries to provide a synergy effect by integrating Client Mobile IPv4 (CMIPv4) and Proxy Mobile IPv4 (PMIPv4), and using the two mobility protocols selectively according to the situation of real heterogeneous networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8B
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• pp.751-759
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• 2009

Due to the advance of WLAN technology, the use of the multimedia service such as the video streaming service has been increased in the home network. However, we need to study the method which decreases the transmission delay and the frame loss rate to provide QoS of the video streaming service. Therefore, this paper proposes an active buffer management mechanism to guarantee QoS of the streaming service in IEEE 802.11e EDCA. The proposed protocol discards the frame in the HoL of the buffer based on the importance of each frame and the virtual transmission delay of frame newly arriving at the buffer. In the simulation results, the proposed algorithm not only decreases the frame loss probability of important I and P frames but also stabilizes the transmission delay. It may increase the QoS of video streaming services.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.372-375
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• 2008

IEEE 802.11e standardized the EDCA mechanism to support the priority based QoS. And the virtual collision handler schedules the transmission time of each MAC frame using the internal back-off window according to the access category(AC). This can provides the differentiated QoS to real-time services at the medium traffic load condition. However, the transmission delay of MAC frame for real-time services may be increased as the traffic load of best effort service increases. It becomes more critical when the real-time service uses a compressed mode video codec such as moving picture experts group(MPEG) 4 codec. That is because each frame has the different importance. That is, the I-frame has more information as compared with the P- and the B-frame. In this paper, we proposed a buffer management algorithm based on the frame importance and the delay bound. The proposed algorithm is consisted of the traffic regulator based on the dual token bucket algorithm and the active queue management algorithm. The traffic regulator reduces the transmission rate of lower AC until that the virtual collision handler can transmit an I-frame. And the active queue management discards frame based on the importance of each frame and the delay bound of head of line(HoL) frame when the channel resource is insufficient.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.837-840
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• 1999

In this paper, we design and verify the hardware circuit that performs PLCP(Physical Layer Convergence Protocol) protocol functions of physical layer in IEEE 802.11 frequency hopping WLAN(Wireless Local Area Network). Altera MAX＋PLUS I $I^{〔1〕}$ is used as a design tool. The designed circuit consists of control register module to interface with upper layer, FIFO module to transmit/receive data with upper layer, TX function module, and RX function module. It is verified that the developed circuit conforms well to the IEEE 802.11 standard specification and can support both 1Mbps and 2 Mbps transmission rate by simulation. The developed circuits can be utilized for the implementation of protocol processor in wireless LAN areas.