• Title/Summary/Keyword: contention avoidance point

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Q-Learning based Collision Avoidance for 802.11 Stations with Maximum Requirements

  • Chang Kyu Lee;Dong Hyun Lee;Junseok Kim;Xiaoying Lei;Seung Hyong Rhee
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.17 no.3
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    • pp.1035-1048
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    • 2023
  • The IEEE 802.11 WLAN adopts a random backoff algorithm for its collision avoidance mechanism, and it is well known that the contention-based algorithm may suffer from performance degradation especially in congested networks. In this paper, we design an efficient backoff algorithm that utilizes a reinforcement learning method to determine optimal values of backoffs. The mobile nodes share a common contention window (CW) in our scheme, and using a Q-learning algorithm, they can avoid collisions by finding and implicitly reserving their optimal time slot(s). In addition, we introduce Frame Size Control (FSC) algorithm to minimize the possible degradation of aggregate throughput when the number of nodes exceeds the CW size. Our simulation shows that the proposed backoff algorithm with FSC method outperforms the 802.11 protocol regardless of the traffic conditions, and an analytical modeling proves that our mechanism has a unique operating point that is fair and stable.

Traffic-Adaptive PCF MAC Scheduling Scheme Based on IEEE 802.11b Wireless LAN (IEEE 802.11b 무선랜에서 트래픽 부하에 따른 적응적인 PCF MAC 스케줄링 기법)

  • 신수영;장영민;강신각
    • Proceedings of the IEEK Conference
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    • 2003.11c
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    • pp.191-194
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    • 2003
  • In IEEE 802.11b, Medium Access Control Sublayer consists of DCF (Distributed Coordination Function) and PCF (Point Coordination Function). DCF provides contention based services and PCF provides contention free services for QoS satisfaction. DCF uses CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) as an access protocol. And PCF uses Polling Scheme. In this paper, a modified New-PCF, which gives weights to channels with heavier traffic load, was suggested. NS-2 simulations were conducted to compare the service performances with original DCF, PCF and the modified New-PCF respectively. Simulation results has shown the increased overall throughput with the proposed New-PCF compared with other cases.

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Design and Performance Analysis of an Enhanced MAC Algorithm for the IEEE 802.11 DCF (IEEE 802.11 DCF 성능 개선을 위한 매체접근제어 알고리즘의 설계 및 성능 분석)

  • Hwang, An-Kyu;Lee, Jae-Yong;Kim, Byung-Chul
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.42 no.10 s.340
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    • pp.39-50
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    • 2005
  • In this paper, we propose a performance improving MAC algerian for the IEEE 802.11 DCF. WLAN based IEEE 802.11 uses two control methods called 'Distributed Coordination Function(UF)' and 'Point Coordination Function(PCF)'. The nF controls the Urnsmission based on carrier sense multiple access with collision detection(CSMA/CA), that decides a random backoff time with the range of contention window for each terminal. Normally, each terminal the CW double after collision, and reduces the CW to the minimum after successful transmission. This paper proposes an enhanced DCF algorithm that decreases the CW smoothly after successful transmission in order to reduce the collision Probability by utilizing the current status information of WLAN. We also analyze the throughput and delay performance for the unsaturated case mathematically. Simulation results show that our algorithm enhances the saturation throughput of WLAN. They also coincide well with the analytical results.

Performance Analysis on DCF Considering the Number of Consecutive Successful Transmission in Wireless LAN (무선랜에서 연속적인 전송성공 횟수를 고려한 DCF 성능분석)

  • Lim, Seog-Ku
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.2
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    • pp.388-394
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    • 2008
  • In this paper, MAC(Medium Access Control) algorithm for the IEEE 802.11 DCF(Distributed Coordination Function) improving the performance is proposed and analyzed by simulation. The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF and PCF(Point Coordination function). The DCF controls the transmission based on CSMA/CA(Carrier Sense Multiple Access With Collision Avoidance). The DCF shows excellent performance relatively in situation that competition station is less but has a problem that performance is fallen from throughput and delay viewpoint in situation that competition station is increased. This paper proposes an enhanced DCF algorithm that increases the CW to maximal CW after collision and decreases the CW smoothly after successful transmission in order to reduce the collision probability by utilizing the current status information of WLAN. To prove efficiency of proposed algorithm, a lots of simulations are conducted and analyzed.

A Study on New DCF Algorithm in IEEE 802.11 WLAN by Simulation (시뮬레이션에 의한 IEEE 802.11 WLAN에서의 새로운 DCF 알고리즘에 관한 연구)

  • Lim, Seog-Ku
    • Journal of Digital Contents Society
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    • v.9 no.1
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    • pp.61-67
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    • 2008
  • In this paper, MAC algorithm for the IEEE 802.11 DCF improving the performance is proposed and analyzed by simulation. The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF(Distributed Coordination Function) and PCF(Point Coordination Function). The DCF controls the transmission based on CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance), that decides a random backoff time with the range of CW(Contention Window) for each station. Normally, each station increase the CW to double after collision, and reduces the CW to the minimum after successful transmission. The DCF shows excellent performance relatively in situation that competition station is less but has a problem that performance is fallen from throughput and delay viewpoint in situation that competition station is increased. This paper proposes an enhanced DCF algorithm that increases the CW to maximal CW after collision and decreases the CW smoothly after successful transmission in order to reduce the collision probability by utilizing the current status information of WLAN. To prove efficiency of proposed algorithm, a lots of simulations are conducted and analyzed.

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QoS-Oriented Handoff Algorithm in IEEE 802.11 Wireless LAN (IEEE 802.11 무선랜에서 서비스 질(QoS) 지향적인 핸드오프 알고리즘에 관한 연구)

  • Choi Haeng-Keol;Kim Il-Hwan;Seo Seung-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.6B
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    • pp.338-348
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    • 2005
  • Currently, IEEE 802.11 Wireless LAN (WLAN) is rising as the most popular means for the broadband wireless access network. In this thesis, we propose a QoS(Quality of Service)-Oriented mechanism using handshaking method of scanning phase in IEEE 802.11 handoff. In conventional process for handoff, the major criterion to select the best AP(Access Point) among candidates is normally based on the RSS(Received Signal Strength), which does not always make the selected network guarantee the maximum achievable performance. Even though the link quality with a neighboring AP is excellent, the AP may not be a good candidate to handoff to simply because MAC(Medium Access Control) protocol of IEEE 802.11 standard is contention-based such as CSMA/CA. Therefore, if we apply network level information to AP selection criteria, we can achieve better handoff efficiency rather than before. The analysis and simulation results applied to our new mechanism show clearly better performance than AP selection based on traditional handoff method.

A Seamless N-Screen Service Technology for Disseminating Disaster Informations (재해정보 확산을 위한 끊김없는 N-스크린 서비스 기술)

  • Kim, Kyungjun;Park, Jonghoon;Kim, Chulwon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.3
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    • pp.587-595
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    • 2015
  • A by-pass path in wireless sensor networks is the alternative path which be able to forward data when a routing path is being broken. One reason of depleting energy is occurred by the path. The method for solving prior to addressed the problem is proposed. However, this method may deplete radio resource. The best path has advantage that network lifetime of sensor nodes is prolonged; on the contrary, in order to maintain the best path it have to share their information between the entire nodes. In this paper, we propose the best path searching algorithm in the distributed three dimensional sensor networks. Through the neighboring informations sharing in the proposed method, the proposed algorithm can decide the best k-path as well as the extension of network lifetime.

An Otimal Path Determination in 3D Sensor Networks (3차원 무선 센서네트워크에서 최적경로 선정)

  • Kim, Kyung-Jun;Park, Sun;Kim, Chul-Won;Park, Jong-Hoon
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.16 no.9
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    • pp.1931-1938
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    • 2012
  • A by-pass path in wireless sensor networks is the alternative path which be able to forward data when a routing path is being broken. One reason of depleting energy is occurred by the path. The method for solving prior to addressed the problem is proposed. However, this method may deplete radio resource. The best path has advantage that network lifetime of sensor nodes is prolonged; on the contrary, in order to maintain the best path it have to share their information between the entire nodes. In this paper, we propose the best path searching algorithm in the distributed three dimensional sensor networks. Through the neighboring informations sharing in the proposed method, the proposed algorithm can decide the best k-path as well as the extension of network lifetime.