• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4B
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• pp.360-367
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• 2009

In this paper, we propose a design methodology of IEEE 802.11n MAC which aims to achieve the higher throughput of more than 100Mbps in downlink as measured at the MAC-SAP and present the implementation results of MAC using the proposed design methodology. With our proposed methodology, different from the conventional design flow which has the separate codes for the protocol validation, for the network simulation, and for the system implementation, the unified code can be used for the network simulation and the implementation of software and hardware. Our MAC architecture is partitioned into two parts, Upper-layer MAC and Lower-layer MAC, in order to achieve the high efficiency for the new features of IEEE 802.11n standard. They are implemented in software and hardware respectively. The implemented MAC is tested on ARM based FPGA board.

• Journal of information and communication convergence engineering
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• v.18 no.2
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• pp.88-93
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• 2020

The IEEE 802.11p-based wireless access in vehicular environments (WAVE) [1] communication is a method used exclusively for wireless communication on the road. This technique enables information sharing not only among moving vehicles but also between vehicles and infrastructure [2]. As part of WAVE communication, data is transmitted to and from vehicles in motion; in this case, it is difficult to determine the channel accurately in an outdoor environment owing to the Doppler shift [3]. This paper proposes a new channel estimation scheme for enhancing the reception performance of the IEEE 802.11p-based WAVE system. The proposed technique obtains the initial channel value by estimating the least square in the time domain by inserting a pilot signal for channel estimation into the IEEE 802.11p virtual subcarrier. Subsequently, a least mean square algorithm is applied to the initial channel value to update the estimated channel value. The simulation results obtained using the proposed channel estimation technique confirm its remarkable efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1047-1055
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• 2005

One of major characteristics in wireless LAN is terminal's frequent mobility, so it makes many overheads in the process of authentications repeatedly at each handoffs. So I propose IAPP(Inter Access Point Protocol) of IEEE 802.11f, modified context block and 4 way handshake of IEEE 802.11i, in order to implement secure and rapid handoff. The context block. I proposed, doesn't makes any communication with RADIUS server at handoff period. Therefore, it guarantee higher efficiency than existing handoff mechanisms. Also it can improve security vulnerability by padding authentication field in the context block for providing in advance against Replay and DoS(Denial of Service) attacks.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.917-920
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• 2007

무선 Ad-hoc 네트워크에서는 주로 IEEE 802.11 MAC 프로토콜을 이용한다. IEEE 802.11 MAC 프로토콜은 제어 메시지인 RTS-CTS를 통해서 채널 예약을 하고 데이터를 전송하는 방식으로 모든 통신에 Omni-directional 안테나를 이용하여 전송한다. 본 논문에서는 기존 IEEE 802.11 MAC 프로토콜보다 성능을 향상시키기 위해서 directional 안테나를 이용한 MAC 프로토콜을 사용한다. Directional 안테나를 사용한 MAC 프로토콜은 IEEE 802.11 MAC 프로토콜에 비해서 Spatial Reuse를 증가함으로서 채널 자원을 더욱 효율적으로 사용하는 것이 가능하다. 또한 Directional 안테나의 사용은 안테나의 지향성에 따른 안테나 이득 및 전송 범위의 증가 그리고 전송 범위를 Omni-directional 안테나와 동일하게 적용할 경우에는 저 전력 통신이 가능하다는 장점을 가지고 있다. 그러나 Directional 안테나의 사용은 IEEE 802.11 MAC보다 좋은 성능을 갖기는 하지만 새로운 문제들이 발생한다. 이러한 문제들로는 New Hidden Terminal, Deafness, Capture, 그리고 위치 인식에 관련된 문제들이 발생한다. 본 논문에서서 위에서 언급한 Directional 안테나의 이점과 그리고 문제점에 대해서 설명하고, 이러한 문제들 중에 Deafness 문제를 완화시킬 수 있는 방법을 제안한다. 그리고 QualNet 4.0을 이용한 시뮬레이션을 통해서 제안된 프로토콜의 성능을 평가한다.

• Journal of the Korean Data and Information Science Society
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• v.19 no.1
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• pp.11-24
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• 2008

In this paper, the patterns of movement used in the mobile communication systems are adopted in the mobile computing environment to reduce handover delay and to support seamless handover for MIPv6 based on IEEE 802.11 networks. That is, RtSolPr message and PrRtAdv message can be treated before handover. As the result, it is possible to assign NCoA to MN and Next Access Router(NAR) before handover starts. This can minimize handover delay and reduce the total handover delay.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.586-589
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• 2001

This paper focuses on a method to connect mobile devices such as mobile robot, Automated Guided Vehicle(AGV) to a fieldbus. In this paper, the IEEE 802.11 wireless LAN is used to extend a Profibus-DP network for the mobile devices. In order to integrate these two networks, a protocol converter is developed with two process(i.e., master process of Profibus-DP and virtual master process of IEEE 802.11) and an transmission buffer. Futhermore, a virtual polling algorithm is developed at the protocol conveter in order to satisfy real-time requirements on data communication.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.4
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• pp.53-58
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• 2012

The roadside unit (RSU) collects vehicle information from vehicles in the intelligent transportation system (ITS). The vehicle density on the road within the communication range of a RSU is a time varying parameter. The higher the vehicle density, the more vehicle information can be collected. Therefore, the probability of packet collision will be raised. In this paper, an adaptive transmission scheme is proposed to improve the probability of packet reception rate by changing the data rate and transmission period according to the vehicle density. The performance of IEEE 802.11p MAC protocol that is a standard for vehicular communications is evaulated in terms of the vehicle density with the ns-2,33 simulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.115-124
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• 2007

In this paper, the I/Q mismatch problem between the transmission line and antenna switch is solved by a new CPW matching circuit for a VoWLAN terminal with 54 Mbps communication speed through the IEEE 802.11 b/g CCK/OFDM. I/Q performances with the new matching circuit are analyzed and improved by the output spectrum mask, the characteristics of the EVM(Error Vector Magnitude) due to the nonlinear CCK/OFDM demodulation data, and receiver's sensitivity.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.5
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• pp.81-86
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• 2011

In this paper, fractal microstrip patch antenna in a semicircle, by designing a multi-resonant antenna was improved by bandwidth issues, including the IEEE 802.11 wireless LAN and IEEE802.16e-band mobile WiMax specification both of which can contain non-directional antenna design and measured characteristics of the antenna for multi-resonant resonant frequency, impedance matching, radiation pattern, brilliantly polarity and multiple independent frequencies that can be controlled to meet the three semicircular wireless communications by inserting fractal patch antenna was designed.

• Journal of IKEEE
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• v.18 no.4
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• pp.502-508
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• 2014

This paper has reviewed the performances of various AGCs which can be adopted in IEEE802.11p modems. IEEE802.11p, a high speed mobile communication standard for vehicles, requires high performance signal detector since the channel impulse responses are varied rapidly in time. In order to select the optimal signal detector, we simulated the performances of three detection methods. One is using RSSI signal, the other is using RSSI signal and I/Q signal, and the third is using I/Q signal through the Monte Carlo simulation. We evaluated the performances of the algorithms using our own system based on MAX 2829 transceiver(MAXIM $Integrated^{TM}$) in a real vehicular environment. As a result, the experiment using Fully I/Q signal derives the most excellent performance with the lowest minimum receiver sensitivity, packet error rate (PER) and false alarm rate (FAR).