• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.700-702
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• 2003

최근 고속 무선 네트워크에 대한 사용자의 요구가 증가함에 따라, 낮은 전송속도를 가지는 이동통신 시스템의 대안으로 무선 네트워크 시스템이 부각되고 있다. 무선 네트워크 기술의 보안 취약점은 무선 네트워크 사용의 중요한 장애요인이다. IEEE 802.1x, IEEE 802.11i에서는 인증과 데이터 프라이버시 제공을 위한 표준을 내고 있으나, 무선 네트워크 보안을 완벽하게 지원하지는 않는다. 본 논문에서는 무선 네트워크 환경의 트래픽을 모니터링하고. 통합 관리 서버를 통하여 여러 무선 네트워크를 통합적으로 관리하는 시스템을 설계하고 구현한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1741-1748
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• 2005

In this paper, we describe VLSI design and performance evaluation of OCB-AES crytographic algorithm that simulataneously provides privacy and authenticity. The OCB-AES crytographic algorithm sovles the problems such as long operation time and large hardware of conventional crytographic system, because the conventional system must implement the privancy and authenticity sequentially with seqarated algorithms and hardware. The OCB-AES processor with area-efficient modular offset generator and tag generator is designed using IDEC Samsung 0.35um standard cell library and consists of about 55,700 gates. Its cipher rate is about 930Mbps and the number of clock cycles needed to generate the 128-bit tags for authenticity and integrity is (m+2)${\times}$(Nr+1), where m and Nr represent the number of block for message and number of rounds for AES encryption, respectively. The OCB-AES processor can be applicable to soft cryptographic IP of IEEE 802.11i wireless LAN and Mobile SoC.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.1
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• pp.16-27
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• 2012

In multi-interface multi-channel(MIMC) based tactical ad hoc networks, QoS support for required operational capacity is one of the main challenging issues for multi-hop transmissions. To support QoS in such a harsh environment, we propose a novel MAC scheme to minimize multi-hop as well as per-hop delay. The current IEEE 802.11 MAC protocols should contend to reserve the channel resource at every hop by each sender. The every-hop channel contention results in a degradation of end-to-end delay for multi-hop transmissions. The basic idea of our scheme is to make a "multi-hop reservation" at the MAC layer by using the modified RTS frame. It contains additional information such as destination information, packet priority, and hop count, etc. In addition, we differentiate the contention window area according to the packet priority and the number of hops to deliver packets in the predefined allowed latency. Our scheme can minimize the multi-hop delay and support the QoS of the critical data in real time(i.e., VoIP, sensing video data, Video conference between commanders). Our simulation study and numerical analysis show that the proposed scheme outperforms the IEEE 802.11 MAC.

• Proceedings of the KIEE Conference
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• 2001.11c
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• pp.380-382
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• 2001

This paper presents the implementation of IEEE 802.11 Medium Access Control and Physical Layer Protocol that can be applied to wireless LAN system. We have used PRISM2 chipsets from Intersil to build the baseband, IF, and RF parts. DSSS(Direct Sequence Spread Spectrum) physical layer at 2.4GHz ISM band is adopted in the hardware prototype. To meet the high-speed requirement of physical layer, we have designed the MAC protocol layer with embedded firmware and FPGA. The prototype board is shown to be able to support the physical layer of 5GHz and 600Hz wireless LAN systems.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.4
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• pp.80-85
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• 2015

The era of intelligent transportation system(ITS) has been arrived by applying information and communication technology(ICT) to the traffic. One of these technological advances is a wireless communication technology for a high speed vehicle to be connected to an infrastructure(V2I). A variety of road traffic safety services and operator comfort services are being developed by means of WAVE(Wireless Access in a Vehicular Environment) based on IEEE802.11p Standard. In this paper, the link budget is analyzed to provide a reliable quality of these ITS services. Log-distance model and two-ray model is employed for the wave propagation path loss model which is adequate for a highway environment. Reliable cell coverage is suggested for ITS services from the link budget.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.113-118
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• 2012

In this paper, we discuss the design of the Digital Down Converters for the IEEE 802.11 wireless LAN receiver, which can be used for the customized receiver. The customized receiver can be used for special puropsed services which cannot be realized using the general custom chip. In the OFDM receiver, DDC receives the up sampled Inphase/Quadrature signal from the AD converter and process down sampling and filtering procedures using the Cascaded Intergrator Filter and FIR filters. We discuss the structure and design methodology of DDC's and analyze the simulation results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.3
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• pp.51-57
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• 2010

A dual-mode direct conversion receiver is developed in $0.13\;{\mu}m$ RF CMOS process for IEEE 802.11n based wireless LAN and IEEE 802.16e based mobile WiMAX application. The RF receiver covers the frequency band between 2.3 and 2.7 GHz. Three-step gain control is realized in LNA by using current steering technique. Current bleeding technique is applied to the down-conversion mixer in order to lower the flicker noise. A frequency divide-by-2 circuit is included in the receiver for LO I/Q differential signal generation. The receiver consumes 56 mA at 1.4 V supply voltage including all LO buffers. Measured results show a power gain of 32 dB, a noise figure of 4.8 dB, a output $P_{1dB}$ of +6 dBm over the entire band.

• Journal of Digital Convergence
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• v.11 no.7
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• pp.201-207
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• 2013

The chirp signaling has been mainly used in radar systems due to its good correlation characteristics, and nowadays it is applied to real time locating system(RTLS). The RTLS with chirp signaling was chosen as a standard such as ISO/IEC 24730-5 and IEEE 802.15.4a. In this paper, the performance of a real time locating system with chirp signaling was evaluated and simulated with relative distance error rates. We considered three cases of S/I = -30[dB], -20[dB], and -10[dB] with Rician factor K=10 and K=20. The performance was enhanced with K factor improvement by 25%, 27% and 50% for respective three cases of S/I. As results, in case of S/I < -20[dB], the minimum signal power is required for performance improvement even though the line of sight component is helpful. And also, in case of S/I ${\geq}$ -20[dB], as the line of sight component is stronger the better performance is obtained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.502-513
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• 2004

This paper proposes a symbol synchronization method in the IEEE 802.11a wireless OPDM system, which uses only signs of the in-phase and the quadrature signals in the short preamble. The short preamble is sampled with 2 tines of Nyquist sampling rate and both of the autocorrelation and the cross-relation are used in the proposed method. This method has some advantages that the ACG (Automatic Gain Control) can be processed concurrently during the short preamble and its implementation is not much complicated. The proposed symbol synchronization method is verified through simulations on frequency offset, multi-path and white Gaussian noise.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.440-440
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• 2004