• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.150-153
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• 2008

현재 무선 랜 기반의 WMN은 도심지와 같은 통화량이 많은 지역('핫존')에서 서비스 되고 있다. 다수 핫존을 서비스하는 엑세스 포인트(AP)별로 인터넷 망에 유선 접속할 경우, 망 접속 비용이 높지만, WMN 기술을 이용하면 핫존별로 산재한 트래픽의 집중을 통해 자원을 대폭 줄일 수 있다. 또한, IEEE 802.11 표준은 가용한 채널이 다양한 직교주파수로 되어있어 IEEE 802.11b에서는 2.4GHz에서 간섭 없는 3개의 채널을 제공하고 IEEE 802.11a는 5GHz에서 간섭 없는 12개의 채널을 제공한다. 근접한 access point (AP)주변에는 다른 채널을 할당함으로써 근접한 AP사이에서의 간섭을 막을 수 있다. IEEE 802.11 표준은 동시 사용에 1개의 채널만 사용하게 되어있어 가용한 채널을 동시에 간섭 없이 사용함으로써 전체적인 throuput을 증대 시킬 수 있어 IEEE 802.11 표준 기반의 MAC 프로토콜의 수정만으로 상, 하 레이어의 수정 없이 향상된 멀티채널을 위한 MAC 프로토콜을 제시한다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.340-342
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• 2006

본 논문의 연구에서는 IEEE 802.11e HCCA에서 멀티미디어와 같은 트래픽에 대해 보다 안정적인 전송을 위하여 일정 시간 동안 채널을 사용할 수 있도록 HC (Hyper Coordinator)가 허가함에 있어서 IEEE 802.11 PHY (physical layer)의 모듈레이션 변화에 따른 동적인 대응이 필요함을 논하고, 문제 해결을 위한 방안을 제시하였다. IEEE 802.11e의 HC는 멀티미디어와 같은 트래픽의 전송을 위하여 BSS (Basic Service Set) 안에 있는 무선 단말기와 TSPEC (Traffic Specification)을 이용하여 CAP (Controlled Access Phase) 채널을 설정하고 관리한다. 그러나 HC가 TSPEC을 설정할 당시와는 달리 무선 단말기들은 이동하거나 물리적으로 채널 환경의 변화로 IEEE 802.11 PHY의 모듈레이터 변경으로 설정된 TXOP 듀레이션 (duration)이 적절하지 않게 된다. 이와 같은 문제점을 밝히고 해결 방안을 아래와 같이 제안한다. 실험을 위해서는 NS-2와 유사하지만 보다 세련된 시뮬레이터를 활용하였다.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.311-316
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• 2005

The power saving mechanism of IEEE 802.16e operates in two modes; awake mode and sleep mode. While the user terminal transmits and receives packets in awake mode, it sleeps for a given interval to save the power consumption in sleep mode. The IEEE 802.16e specifies that the user terminal increases the sleep interval exponentially unless it has to wake up. In this paper, we analyze the performance of IEEE 802.16e power saving mechanism by considering down link traffic conditions. With the extensive simulations, we observe the trade-off between the power saving performance and the average packet delay. In addition, we observe that various performance parameters of IEEE 802.16e power saving mechanism are affected by the traffic patterns.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.5
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• pp.1108-1130
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• 2013

Wireless Body Area Networks (WBANs) are becoming increasingly important to solve the issue of health care. IEEE 802.15.6 is a wireless communication standard for WBANs, aiming to provide a real-time and continuous monitoring. In this paper, we present our development of a modified Markov Chain model and a backoff model, in which most features such as user priorities, contention windows, modulation and coding schemes (MCSs), and frozen states are taken into account. Then we calculate the normalized throughput and average access delay of IEEE 802.15.6 networks under saturation and ideal channel conditions. We make an evaluation of network performances by comparing with IEEE 802.15.4 and the results validate that IEEE 802.15.6 networks can provide high quality of service (QoS) for nodes with high priorities.

• Journal of Korea Society of Digital Industry and Information Management
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• v.16 no.2
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• pp.27-33
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• 2020

Backward compatibility is one of the key issues for radio equipment supporting IEEE 802.11, the typical wireless local area networks (WLANs) communication protocol. For a successful packet decoding with the backward compatibility, the frame format detection is a core precondition. This paper presents a novel frame format detection method based on a deep learning procedure for WLANs affiliated with IEEE 802.11. Considering that the detection performance of conventional methods is degraded mainly due to the poor performances in the symbol synchronization and/or channel estimation in low signal-to-noise-ratio environments, we propose a novel detection method based on convolutional neural network (CNN) that replaces the entire conventional detection procedures. The proposed deep learning network provides a robust detection directly from the receive data. Through extensive computer simulations performed in the multipath fading channel environments (modeled by Project IEEE 802.11 Task Group ac), the proposed method exhibits superb improvement in the frame format detection compared to the conventional method.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.191-194
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• 2005

In this paper the platform system for IEEE 802.15.4 Low Rate WPAN is designed and fabricated. IEEE 802.15.4 Low Rate WP AN system serves the functions and realization of home-area network. According to the IEEE 802.15.4 standard, there are two modes, One is BPSK modulation in 868/915MHz frequency band. The other is O-QPSK modulation in 2.45GHz frequency band. In this paper we implemented the platform system mounted in one PCB board in 868/915MHz frequency band of IEEE 802.15.4 Low Rate WPAN system. We measured that the platform system which consists of digital part and RF part has good performance. Also RF part is realized by design and fabrication of the RF transceiver IC. The key issue is to make the platform system which provides the function of Low Rate WPAN system to meet the requirement of IEEE 802.15.4 standards.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2007.11a
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• pp.330-340
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• 2007

IEEE 802.11 wireless LANs employ the backoff algorithm to avoid contentions among STAs when two or more STAs attempt to transmit their data frames simultaneously. The MAC efficiency can be improved if the CW values are adaptively changed according to the channel state of IEEE 802.11 wireless LANs. In this paper, we propose a dynamic contention window control algorithm using the genetic algorithm to improve the MAC throughput of IEEE 802.11 wireless LANs.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1558-1562
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• 2005

This paper describes the design and implementation of a wireless home network system using Home Network Control Protocol (HNCP) called the wireless HNCP home network system. For wireless interfaces of HNCP, IEEE 802.11b and IEEE 802.15.4 standard protocols are considered. With the implementation of the wireless HNCP home network system, a simple analysis about coexistence between IEEE 802.11b and IEEE 802.15.4 is achieved. Through the implemented wireless HNCP home network system and the analytical results about the coexistence between both two different wireless protocols, the feasibility of the wireless HNCP home network system is shown.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.247-255
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• 2003

In this paper, an $tan^{-1}$ circuit for the frequency synchronization of OFDM based IEEE 802.11a is presented. The proposed circuit consists of a divider, an $tan^{-1}$ ROM and a phase detector, which can detect frequency offset within 0.0491 rad. The circuit implemented with FPGA shows a pull-in range of under ${\pm}625KHz$ at 5dB AWGN. It may be useful for IEEE 802.11a WLAN standard.

• Information and Communications Magazine
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• v.26 no.12
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• pp.19-27
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• 2009

본 고에서는 IEEE 802.16m 표준 및 기술 동향에 대해서 개관한다. IEEE 802.16m은 현재 상용화되고 있는 IEEE 802.16e 시스템의 진화된 형태로, IMT-2000을 대체해 나갈 차세대 이동 통신 시스템을 목표로 한다. 이를 위해 IEEE 802.16e 시스템과의 호환성이 유지되어야 하며, ITU-R에서 차세대 통신시스템 표준으로 추진중인 IMT-advanced의 요구사항을 만족시킬 수 있어야 한다. 이와 같은 목표를 달성하기 위해 물리적 계층 및 MAC 계층에서 다양한 기술들이 고려되었고, 본 고에서 전반적인 기술들에 대해서 간략히 살펴보도록 한다. 더불어, ITU-R에 제출한 IMT-Advanced 제안서의 결과를 토대로 IEEE 802.16m 시스템의 성능을 살펴보도록한다.