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.

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

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.

Wireless LAN --- IEEE 802.11 --- Distributed Coordination Function DCF --- Opnet Simulator