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Article
A Balanced Backoff Algorithm for IEEE802.11 Wireless Network

Authors: D.J. Kadhim --- S.H. Abdulhussain --- B.M. Ridha --- A.M. Abbas
Journal: Iraqi Journal of Applied Physics المجلة العراقية للفيزياء التطبيقية ISSN: 18132065 23091673 Year: 2012 Volume: 8 Issue: 1 Pages: 27-33
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.

Keywords

IEEE 802.11 --- DCF --- MAC --- Backoff Algorithm


Article
Traffic Offloading in LTE System Based Heteroge-neous Networks

Author: Mahmood F. Mosleh
Journal: Iraqi Journal for Electrical And Electronic Engineering المجلة العراقية للهندسة الكهربائية والالكترونية ISSN: 18145892 Year: 2017 Volume: 13 Issue: 2 Pages: 152-160
Publisher: Basrah University جامعة البصرة

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Abstract

The continuous growing developments in the traffic of mobile data limits the data throughput and capacity of cellular networks. “Heterogeneous Networks (HetNets)” are efficient solution to realize such demands. However, in HetNets, the congestion on the overloaded cellular network can be increased when the traffic of data is pushed from a cellular network to the Wi-Fi. In practice, offloading the cellular data traffic to a Wireless Local Area Network (WLAN) depending on the signal quality is a broadly deployed method to solve such problem. The use of Device to Device (D2D) communication further enhances the traffic offloading in WLAN systems and helps to obtain better throughput, end-to-end delay and network load. However, the critical offloading potential and its impacts on the whole performance is not totally understood. In this paper, the offloading of Long Term Evolution (LTE) traffic is presented using a WLAN for voice and video applications. A comparison is performed among two WLAN mecha-nisms; Distributed coordination function (DCF) and Point Coordination Function (PCF). As well, the effect of add-ing a D2D technology to the PCF is discussed. The WLAN effectively offloaded nodes at their Signal to Interference and Noise Ratio (SINR) becomes more than a specific threshold. Results presented that the PCF mechanism outper-forms the DCF one in terms of packet loss ratio, throughput and the maximum load of the entire network. In addi-tion, the use of a D2D serviced in the PCF helps in further reduction in the network load.

Keywords

HetNets --- offloading --- LTE --- WLAN --- DCF --- PCF --- D2D --- SINR


Article
Saturation Throughput and Delay Performance Evaluation of the IEEE 802.11g/n for a Wireless Lossy Channel

Author: Salah A. Alabady
Journal: Iraqi Journal for Electrical And Electronic Engineering المجلة العراقية للهندسة الكهربائية والالكترونية ISSN: 18145892 Year: 2018 Volume: 14 Issue: 1 Pages: 51-64
Publisher: Basrah University جامعة البصرة

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Abstract

Non-ideal channel conditions degrade the performance of wireless networks due to the occurrence of frameerrors. Most of the well-known works compute the saturation throughput and packet delay for the IEEE 802.11Distributed Coordination Function (DCF) protocol with the assumption that transmission is carried out via an idealchannel (i.e., no channel bit errors or hidden stations), and/or the errors exist only in data packets. Besides, there areno considerations for transmission errors in the control frames (i.e., Request to Send (RTS), Clear to Send (CTS), andAcknowledgement (ACK)). Considering the transmission errors in the control frames adds complexity to the existinganalysis for the wireless networks. In this paper, an analytical model to evaluate the Medium Access Control (MAC)layer saturation throughput and packet delay of the IEEE 802.11g and IEEE 802.11n protocols in the presence of bothcollisions and transmission errors in a non-ideal wireless channel is provided. The derived analytical expressionsreveal that the saturation throughput and packet delay are affected by the network size (n), packet size, minimumbackoff window size (Wmin), maximum backoff stage (m), and bit error rate (BER). These results are important forprotocol optimization and network planning in wireless networks.


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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