Abstract Ad-hoc networking is a concept in computer communications, which means that users wanting to communicate with each other form a temporary network, without any form of centralized administration. Each node participating in the network acts both as host and a router and must therefore be willing to forward packets for other nodes.In a multi-hop wireless packet network, a packet traverses more than one wireless link in traveling from its source to its destination. Such wireless networks have received considerable attention recently in the context of ad hoc networks. Ad-Hoc networks are self-organizing multi-hop wireless networks where not all links along the path of a packet can be activated simultaneously. Hence the performance of a higher level mechanism, such as congestion window or Transport Layer protocol (TCP) will depend crucially on how the links are scheduled for transmission. In multiple access networks, such as the IEEE802.11 wireless LAN, the scheduling of transmissions is done by the medium access control (MAC) protocol. This transmission scheduling is completely unaware of the needs of the TCP congestion window protocol. This thesis is concerned with the poor interaction between the TCP adaptive window protocol, the IEEE 802.11 MAC protocol, and the IEEE 802.11 Ad-Hoc routing protocol. Our thesis follow on the work done by the researchers K. Nahm and C. Kuo in the paper entitled “TCP over 802.11 Multihop networks issues and Performance Enhancement” [1]. Our contributions are two-fold. First we have repeated and confirmed the simulation results reported by K.Nahm and C.Kuo using NS-2 network simulator. Second we have introduced a simple modification in the 802.11 DSR routing protocol which reduces the unnecessary VI reroutings triggered by MAC packet collisions and enforces the TCP to enter the fast retransmit / fast recovery phase to quickly recover the packet loses. This modification has been simulated using NS-2 network simulator and from the results we have found that it provides a substantial improvement in TCP performance in the situations that we have considered in the simulation models
يحي الشارف المبروك (2009)

Free space optical (FSO) communication is a promising solution to deliver the last mile communication and to guarantee a high data rate. However, the performance of FSO links can be significantly degraded by adverse weather conditions. Recently, machine learning algorithms (MLAs) have emerged for robust prediction to optimize the network performance. In this work, the Quality factor (Q) of FSO systems is estimated by means of four MLA models, namely, multi-linear regression, support vector regression, decision tree regression, and random forest regression. The synthetic data is used for training and testing these MLAs models, and several atmosphere conditions are considered with multiple transceivers FSO link system. The results of decision tree and random forest models demonstrated high coefficient of determination (R 2 ) and low mean square error (MSE) as compared to the other models.
Amal A. Algedir, Taissir Y. Elganimi(10-2020)

إن معدل البيانات والقدرات و التغطية و الكفاءة الطيفية في نظم الاتصالات اللاسلكية يمكن أن تتعزز مع الناقل متعدد الحوامل والهوائي المتعدد، وبالتالي يتعزز الأداء العام لمنظومات الاتصالات اللاسلكية بشكل كبير من خلال الجمع بين تقنيات أنظمة تساعد تقنية الهوائيات متعددة المداخل والمخارج في ، تجميع تقسيم ترددي متعامد و أنظمة الهوائيات متعددة المداخل والمخارج زيادة سرعة تدفق البيانات وحيث أن تقنية تجميع تقسيم ترددي متعامد تعمل على نشر القناة الترددية انتقائية التلاشى على العديد من الرموز في هذه الأطروحة، سيتم تقييم الاداء بالاعتماد على مستوى الوصلة ومستوى النظام، حيث يتمثل قياس الأداء في مقدار حصيلة البيانات ، ونصف قطر الخلية وقوة الإشارة بالنسبة إلى التداخل الضوضاء، كما يعتمد على معيار القدرة المستخدمة آخذا في الإعتبار نوع التضميين والترميز .في هذه الأطروحة تبدأ السيناريوهات من الوصلة وتمتد الي مستوى النظام في تقنية التطور طويل الأمد. لتحقيق ما ورد أعلاه: من خلال تحليل المعادلات وبرنامج المحاكاة لحساب صافي البيانات عند حافة الخلية وتغطية الخلية والسعة على الوصلة الهابطة، ثم بعد تنفيذ برنامج المحاكاه، لاحظنا الهوائيات المتعددة الإرسال تؤثر على سرعة وصول النقل وأخذا في الاعتبار أسلوب التضمين فعند الزيادة في عدد الهوائيات فان صافي البيانات تزداد أيضا ولكن يجب أن تكون متناسبة مع احتمالية الخطأ وكذلك تتحسن التغطية مع نقصان رتبة التضمين المستخدم. ان مستوى النظام مع حركة المرور المختلفة الإنتاجية للنظم وقدرة الشبكة تتحدد بواسطة عدد كتل الموارد ، حيث ان عدد هذه الكتل تعتمد على معدل سرعة بيانات الخدمة ومعدل سرعة البيانات لكل كتلة. تنتهي هذه الأطروحة بخاتمة وملخص للنتائج وكذلك بعض التوصيات وبعض المواضيع لدراسات مستقبلية كإمتداد لما تم في هذه الأطروحة. Abstract In wireless communication systems the data rate, capacity, coverage, and spectral efficiency; can be enhanced with multi-carrier transmission and multi-antenna, then the overall wireless communication system performance is greatly enhanced by combining OFDM and MIMO schemes, MIMO helps in increasing the throughput where as OFDM spreading out the frequency selective fading channel over many symbols. In this thesis evaluating performance of the system depends on both link and system levels, where the measure of performance is represented in the throughput, cell radius and the effective signal to interference plus noise ratio (SINR). It also depends on the employed capacity criterion and it takes into account the impact of adaptive modulation and coding. The worked scenarios start from a link level extending to a system level in 3GPP LTE. To achieve the above a number of tasks followed by observations are carried out. They start by analysis of the equations and a Matlab program is written to calculate the cell edge throughput, cell coverage and DL capacity. After the programs implementation, the multi antenna transmission effect is noted on the arrival throughput when taking into account the modulation technique. When increasing the order of the antenna and the throughput is also increased, but it must be traded off with the probability of error; Coverage has also improved by decreasing the order of the modulation technique. For the system level with different traffic, the overall throughput of the system and the capacity of the network are determined by the number of resource blocks (RBs). These RBs depend on the bit rate of the service and bit rate for each RB. The adopted scenarios in this thesis start from link to system, where the features are represented in a flexible base station and user configurations, channel modeling with path loss, user mobility, also at different transmitter and receiver (MIMO). The approaches are useful in single user and multi-user MIMO, then all of the above can be standardized by metrics: capacity, throughput, spectral efficiency, user QoS etc. Finally thesis conclusion and some future work as an extension of this work are presented.
هبه مدحت الزقلعى (2014)