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Article
New Algorithm for High Throughput of IEEE 802.11 Distributed Coordination Function

Authors: Sadiq H. Abdulhussain --- Dheyaa J. Kadhim --- Basheera M. Ridha --- Amna M. Abbas
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2018 Volume: 14 Issue: 2 Pages: 27-34
Publisher: iraqi society for alternative and renewable energy sources and techniques الجمعية العراقية لمصادر وتقنيات الطاقة البديلة والمستجدة

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Abstract

The Backoff mechanism is a basic part of a Media Access Control (MAC) protocol which provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multi-point network. Since only one transmitting node uses the channel at any given time, the MAC protocol must suspend other nodes while the media is busy. In order to decide the length of node suspension, a backoff mechanism is installed in the MAC protocol. The choice of backoff mechanism should consider generating backoff timers time, which is uniformly selected from the Contention Window (CW) and allow adequate time for current transmissions to finish and, at the same time, avoid unneeded idle time that leads to redundant delay in the network. Moreover, the backoff mechanism used should decide the suitable action to be taken in case of repeated failures of a node to attain the media. Further, the mechanism decides the action needed after a successful transmission since this action affects the next time backoff is needed [2]. Several back-off schemes will be discussed and a new proposed algorithm has been proposed to achieve high throughput of the IEEE 802.11 DCF.


Article
Simulation Study 0f 802.11b DCF Using OPNET Simulator
دراسة لمحاكاة الشبكة اللاسلكية 802.11b باستخدام محاكي الأوبنيت

Authors: Manal Kadhim Odah --- Mohammad Hussian Ali
Journal: Engineering and Technology Journal مجلة الهندسة والتكنولوجيا ISSN: 16816900 24120758 Year: 2009 Volume: 27 Issue: 6 Pages: 1108-1117
Publisher: University of Technology الجامعة التكنولوجية

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Abstract

A simulation study of an IEEE 802.11b which is the most important standard forwireless local area networks was presented in this paper. The simulation is conducted usingOPNET IT Guru Academic Edition 9.1. Wireless network performance depends mainly onthe end to end throughput and average delay. Different applications place differentrequirements on the network. Thus, it is necessary to evaluate and analysis the performanceof IEEE 802.11b WLAN system under the fundamental access mechanism for mediumaccess control (MAC) called distributed coordination function (DCF).This can achieve bystudying the impact of parameters such as Request to Send/ Clear to Send (RTS/CTS),Fragmentation Threshold (FTS) and discuss the best configurations and parameters value incorrespondence to network load and topology to get best performance which is the mainobjective of this paper.

802.11 ) التي تعتبر من أهم مقاييس الشبكات b) هذا البحث يقدم دراسة لمحاكاة الشبكة اللاسلكيةالمحلية اللاسلكية. المحاكاة تمت باستخدام محاكي الأوبنيت. إن أداء الشبكة اللاسلكية يعتمد بصورة. (average delay) ومعدل التأخير (throughput) رئيسية على كمية المعلومات التي يتم معالجتهاالتطبيقات المختلفة تستدعي متطلبات مختلفة للشبكة . لذلك من الضروري إيجاد وتحليل الأداء للتقنيةبدراسة تأثير متغيرات مثل إرسال طلب / إرسال إجابة .(MAC) الأساسية للاتصال بالوسط للمقياسومناقشة أفضل تشكيلة وقيم للمتغيرات بالتوافق (FTS) وعتبة التقطيع RTS/CTSمع حمل الشبكة وهيئتها للحصول على أداء أفضل وهو الهدف الرئيسي من هذا البحث.

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