• 한국정보통신설비학회:학술대회논문집
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• 2005.08a
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• pp.74-84
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• 2005

In this paper, a new coexistence mechanism between IEEE 802.15.4 and IEEE 802.11, ACROS (Active Channel Reservation for coexistence), is proposed. The key idea of ACROS is to reserve the channel for IEEE 802.15.4 transmission. During the reservation, IEEE 802.11 transmissions cannot be occurred. Request-to-send/clear-to-send mechanism of IEEE 802.11 is used to reserve channel. The proposed ACROS mechanism is implemented into PC based prototype. By the experiments, the $e{\pm}ciency$ of ACROS is proved.

• Electronics and Telecommunications Trends
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• v.22 no.4 s.106
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• pp.156-168
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• 2007

1997년에 IEEE 802.11 WG에서 1~2Mbps급의 전송속도를 가지는 근거리 무선 LAN에 대한 규격을 시작으로, 최근 100Mbps 이상 고속의 데이터 전송속도를 지원하는 규격에 이르기까지 무선 LAN에 대한 기술이 지속적으로 발전되고 있다. 최근 무선통신 분야에서는 다양한 멀티미디어 데이터를 고속으로 전송하는 응용서비스가 증가하고 있으며, 이러한 서비스를 지원할 수 있는 무선 QoS MAC 기술이 IEEE 802.11e에서 표준화되었다. 본 고에서는 무선 LAN 관련 국제 표준화기구인 IEEE 802.11 WG에서 진행되고 있는 표준화 내용 중에서 802.11e에서 표준화한 QoS MAC 기술을 중심으로 MAC 기술 및 관련 표준화 동향에 대하여 살펴보고자 한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.199-204
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• 2011

This paper evaluates on the feasibility of MIL-STD-188-220 protocol as a medium access protocol over WNW(Wideband Network Waveform) by simulating and comparing with IEEE 802.11e-based protocol. WNW is newly designed waveform for next-generation broadband tactical communication system. This paper shows the feasibility of using the MIL-STD-188-220 protocol that shows better performance than IEEE 802.11e-based protocol on the particular environment.

• Journal of KIISE:Information Networking
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• v.35 no.3
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• pp.173-182
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• 2008

Promoting quality of streaming service in wireless networks has attracted intensive research over the years. Instable wireless channel condition causes high transmission delay and packet loss, due to fading and interference. Therefore, they lead to degrade quality of video streaming service. The IEEE 802.11 Working Group is currently working on a new standard called IEEE 802.11e to support quality of service in WLANs. And several schemes were proposed in order to guarantee QoS. However, they are not adaptable to network condition. Accordingly, they suffered video quality degradation, due to buffer overflow or packet loss. In this paper, to promote quality of video streaming service in WLANs, we propose a cross-layer architecture based on IEEE 802.11e EDCA model. Our cross-layer architecture provides differentiated transmission mechanism of IEEE 802.11e EDCA based on priority of MPEG-4 video frames and adaptively controls the transmission rate by dropping video frames through the efficient bandwidth estimation based on distinction of each AC. Through the simulation, proposed scheme is shown to be able to improve end-to-end qualify for video streaming service in WLANs.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.212-215
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• 2003

본 논문에서는 IEEE 802.11e MAC (Medium Access Control) 프로토콜을 NS-2 등과 같은 유명한 시뮬레이터들보다도 진보적인 NCTUns 시뮬레이터를 이용하여 개발하고자 하면서, 각 MSDU (MAC Service Data Unit)마다 제공되어야 하는 TID (Traffic Identification) 를 결정하는 방안을 모색하고 있다. 따라서 본론에서는 IEEE 802.l1e MAC 프로토콜과 NCTUns 시뮬레이터 에 대해서 기술하며 본 논문에서 제안하는 방법에 대해서 서술한다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.581-585
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• 2006

무선랜 환경에서의 효율적인 비디오 스트리밍을 하기위해서는 불안정한 네트워크 대역폭과 패킷지연, 패킷손실 등의 문제가 해결 되어야 한다. 본 논문에서는 서비스 품질의 보장을 위해 기존의 Best-effort에 기반한 IEEE 802.11 MAC 프로토콜을 향상시킨 IEEE 802.11e MAC 프로토콜을 이용하여 Cross-layer 기반의 프레임 우선순위화 기법을 제안 하였다. 멀티미디어 트래픽의 프레임 중요도에 따라 다르게 부여한 Priority를 이용해 IEEE 802.11e MAC 프로토콜의 차별화된 데이터 전송을 하였으며, 네트워크 상태 모니터링을 통해 중요도가 낮은 프레임을 우선적으로 폐기하는 적응적 전송율 조절 기법을 제안하였다. 실험 결과는 제안하는 Cross-layer기반의 프레임 우선순위화 기법이 멀티미디어 스트리밍의 종단간 QoS를 향상 시킬 수 있음을 보여준다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1178-1190
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• 2009

IEEE 802.11e proposed by IEEE 802.11 working group to guarantee QoS has contention based EDCA and contention free based HCCA. HCCA, a centralized polling based mechanism of 802.11e, needs a scheduling algorithm to allocate the network resource efficiently. The existing standard scheduler, however, is inefficient to support for QoS guarantee for real-time service having VBR traffic. To efficiently assign resource for VBR traffic, in this paper, we propose TXOP algorithm based on dual leaky bucket using average resource allocation and peak resource allocation. The minimum TXOP of each station is obtained by using statistical approach to maximize number of stations of which performance satisfy QoS target. Simulation results show that the proposed algorithm has much higher performance compared with reference scheduler in terms of throughput and delay.

• Journal of Korean Institute of Industrial Engineers
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• v.37 no.2
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• pp.89-95
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• 2011

The distributed coordination function (DCF) and point coordination function (PCF) protocols are the basic MAC protocols for legacy IEEE 802.11, IEEE 802.11a, IEEE 802.11b, IEEE 802.11e, IEEE 802.11g and IEEE 802.11n wireless LANs. When the DCF protocol is used for the various versions of IEEE 802.11 wireless LANs, the MAC performance seriously degrades due to the collisions among the stations (STAs) as more and more STAs attempt to transmit their data frames. On the other hand, the PCF MAC performance becomes poor when many STAs exist in IEEE 802.11 wireless LANs, however, only small number of STAs actually attempt to transmit their data frames. In this paper, we propose the algorithm for improving the MAC performance by selectively using the DCF and PCF protocols according to the state of IEEE 802.11 wireless LANs. Numerical examples are presented to show the MAC performance improvement by the selective use of the DCF and PCF protocols according to the network state.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.46 no.4
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• pp.31-41
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• 2009

IEEE 802.11e proposed by IEEE 802.11 working group to guarantee QoS has contention based EDCA and contention free based HCCA. HCCA, a centralized polling based mechanism of 802.11e, needs a scheduling algorithm to allocate the network resource efficiently. The existing standard scheduler, however, is inefficient to support for QoS guarantee for real-time service having VBR traffic. To improve these limit, in this paper, we First, we propose priority polling algorithm which additionally considers the size of MSI and TXOP based on EDD algorithm to increase number of QSTAs. We also propose a dual token bucket TXOP allocation algorithm to reduce congestion caused by stations which enters network with considerable delay variance. TSPEC parameters, Maximum Burst Size (MBS) and Peak Data Rate (PR), are applied to design depth and token generation rate of two buckets. Simulation results show that the proposed algorithm has much higher performance compared with reference and SETT-EDD scheduler in terms of throughput and delay.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.421-425
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• 2005

The increasing number of wireless subscribers who can use internet service any time and any place have caused wireless communications networks to flourish. However, since total communication channel bandwidth for wireless communications is limited, it is very important to find the solution for maximizing the channel utilization. Thus, in this work we propose a QoS packet scheduler for IEEE 802.11e EDCA scheme which is able to maximize the channel throughput with changing the CW value considering wireless channel condition. This proposed scheme is evaluated with NS-2 network simulator under various environments and it is easily shown from the numerical results that the proposed scheme provides better performance than that of the original IEEE 802.11e scheme.