• Title/Summary/Keyword: IEEE802.11s

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무선 LAN에서의 정보보호기술

  • 박영호;김철수;윤정오
    • Review of KIISC
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    • v.12 no.1
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    • pp.66-74
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    • 2002
  • 휴대용 컴퓨터의 보급이 확산됨에 따라 이들을 장소에 상관없이 컴퓨터망에 연결시키는 수단으로 무선 LAN의 사용이 확산되고 있으나 무선 LAN 서비스는 전파라는 무선매체를 사용함으로써 정보도용의 가능성이 높으며 감시도 어렵다는 특징을 가지므로 정보보호가 요구된다. 본 연구에서는 IEEE 802.11 표준안 및 IEEE 802.11 eS 초안에서 제시하는 무선 LAN의 정보보호기술에 관하여 기술한다.

VirtFrame: A Sniffing-based Throughput Estimation Scheme in IEEE 802.11 Wireless LANs (IEEE 802.11 무선랜 환경에서의 스니핑 기반 전송률 측정 기법(VirtFrame)에 관한 연구)

  • Seo, Sung-Hoon;Baek, Jae-Jong;Kim, Dong-Gun;Song, Joo-Seok
    • The KIPS Transactions:PartC
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    • v.18C no.3
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    • pp.187-194
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    • 2011
  • IEEE 802.11 wireless LAN has become the center of attention for one of the most dominant wireless networking technologies nowadays. In densely deployed wireless LANs, mobile stations are exposed to a number of AP, thus it is needed to select the best AP to associate with. The most common approach is to select the AP with the highest received signal strength. However it does not consider traffic load imposed to each AP so that it may cause the poor network performance. Therefore, in this paper, we propose a throughput estimation scheme for neighboring APs by sniffing the traffic within 802.11 networks. We devise a tool, named "VirtFrame", which is to estimate the station's capable throughput from neighbor APs based on the channel access time by virtually combining the sniffed frames. Simulation results show that our proposed scheme well matches that there exists correlation between the channel access time and the actual throughput of the APs.

DCF Throughput Analysis of the MAC Layer in the IEEE 802.11 Wireless LAN (IEEE 802.11a 무선 LAN의 MAC 계층DCF 처리율 분석)

  • Jung, Jin-Wook;Ha, Eun-Sil;Lee, Ha-Chul
    • Journal of Korea Multimedia Society
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    • v.8 no.4
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    • pp.509-515
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    • 2005
  • This paper explores the throughput of DCF protocol with both the traffic intensity and MSDU size at the MAC layer in the 802.11a wireless LAN. By exploring the throughput of DCF protocol with the data rate of 6Mbps, 12 Mbps, 24 Mbps and 54 Mbps, we find the fact that the less the data rate be, the higher the throughput be. We also find, from the throughput calculation by means of traffic intensity and MSDU size, that the longer the MSDU size is, the higher the throughput is. We also found the traffic intensity that the throughput is at the maximum point with the fixed MSDU size.

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IEEE 802.11-based Power-aware Location Tracking System (저전력을 고려한 IEEE 802.11 기반 위치 추적 시스템)

  • Son, Sang-Hyun;Baik, Jong-Chan;Baek, Yun-Ju
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.7B
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    • pp.578-585
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    • 2012
  • Location tracking system through GPS and Wi-Fi is available at no additional cost in an environment of IEEE 802.11-based wireless network. It is useful for many applications in outdoor environment. However, a previous systems used for general device to tag. It is unsuitable for power aware location tracking system because general devices is more expensive and non-optimized for tracking. The hand-off method of IEEE 802.11 standard is not enough considering power consumption. This thesis analyzes the previous location tracking systems and proposes power aware system. First, we designed and implemented tag to optimize location tracking. Next, we propose low-power hand-off method and low-power behavior model in implemented tag. The proposed hand-off method resolve power problem by using the location information and behavior model minimize power consumption of tag through power-saving mode and the concept of duty cycle. To evaluating proposed methods and system performance, we perform simulations and experiments in real environment. And then, we calculate tag's power consumption based on the actual measured current consumption of each operation. In a simulation result, the proposed behavior model and hand-off method reduced about 98%, 59% than the standard's hand-off and default behavior model.

A Scheduling Algorithm for Real-Time Traffic in IEEE802.11e HCCA (IEEE 802.11e HCCA 기반의 실시간 트래픽을 위한 스케줄링 알고리즘)

  • Joung, Ji-Noo;Kim, Jong-Jo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.1
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    • pp.1-9
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    • 2010
  • In this paper we propose a scheduling algorithm for supporting Quality of Service(QoS) in IEEE 802.11e HCCA referred to as ASR-DRR and ASD-DRR, which aims at providing improved performance for the support of multimedia traffic. Although We identify the problem of the current IEEE 802.11e HCCA (Hybrid Coordination Function Controlled Channel Access) scheduler and its numerous variations, that the queue information cannot be notified to the Hybrid Coordinator (HC) timely, therefore the uplink delay lengthens unnecessarily. We suggests a simple solution and a couple of implementation practices, namely the Adaptive Scheduler with RTS/CTS (ASR) and Adaptive Scheduler with Data/Ack (ASD). They are both further elaborated to emulate the Deficit Round Robin (DRR) scheduler. They are also compared with existing exemplary schedulers through simulation, and shown to perform well.

Analysis of Power Amplifier Phase Distortion Characteristics for IEEE 802.11a OFDM Wireless LAM Using Phase Predistortion (사전위상 왜곡을 이용한 IEEE 802.11a OFDM 무선랜 전력증폭기 위상왜곡 특성분석)

  • Oh Chung Gyun;Choi Jae Hong;Koo Kyung Heon
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.42 no.2 s.332
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    • pp.75-80
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    • 2005
  • In this paper, 2-stage power amplifier has been designed for 5.8GHz wireless LAN application. The power amplifier PldB output power has 21.6dBm at 5.8GHz frequency. Also the power amplifier shows 17.6dB gain and -17.8dB input return loss at 5.725GHz to 5.825GHz. The OFDM modulation and transmission block have been modeled in order to analyse the relationship between the power amplifier distortion and output ACPR for the IEEE 802.11a wireless LAN. The nonlinear characteristic of the power amplifier has been modeled as AM-to-AM and AM-to-PM using the behavioral model, and the output spectrum is analysed with the phase distortion variation. Also, amplifier back-off value from PldB to satisfy the required IEEE 802.11a standard spectrum mask has been simulated with phase distortion, and the simulation data have been compared to the measurement result collected by using the pre-distortion technique.

TAS: TCP-Aware Sub-layer over IEEE 802.11-based wireless LANs (IEEE 802.11 기반 무선랜에서 TCP 인진서브 계층 TAS)

  • Choi, Nak-Jung;Jung, Ha-Kyung;Ryu, Ji-Ho;Seok, Yong-Ho;Choi, Yang-Hee;Kwon, Tae-Kyoung
    • Journal of KIISE:Information Networking
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    • v.33 no.5
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    • pp.355-368
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    • 2006
  • This paper introduces a new split-TCP approach for improving TCP performance over IEEE 802.11-based wireless LANs. TCP over wireless LANs differently from wired networks is not aggressive, which is a fundamental reason for poor performance. Therefore, we propose TAS (TCP-Aware Sub-layer) to migigate this problem. Our scheme extends the split-connection approach that divides a connection into two different connections at a split point such as an access point (AP). Using TAS, a wireless node emulates TCP ACK packets using MAC ACK frames, instead of receiving real TCP ACK packets. We compared TAS with both normal TCP and I-TCP (Indirect TCP) by NS2 simulation. Results show that TAS achieves higher throughput, more fair resource allocation and, in power-saving mode, shorter delays.

Load-based Dynamic Backoff Algorithm in Contention-based Wireless Shared Medium (단일 경쟁 매체에서의 새로운 로드 기반 동적 매체 접속 제어 백오프 알고리즘)

  • Seo Chang-Keun;Wang Weidong;Yoo Sang-Jo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.6B
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    • pp.406-415
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    • 2005
  • The standards which use shared medium like IEEE 802.11 wireless LAN have transmission opportunity by contention in contention period. If there are collisions in contention period, medium access control protocol may solve problem by using backoff algorithm. Backoff algorithm is important part in medium access control, but legacy backoff method which is used under IEEE 802.11 standards is not adjusted when load is heavy because of increasing collisions. In this paper, we propose a new load-based dynamic backoff algorithm in contention-based wireless shared medium to improve throughput of medium and to reduce the number of collisions. Proposed backoff algorithm can increase the network utilization about $20\%$ higher than that of binary exponential backoff algorithm.