التصوير باستخدام طريقة المعاوقة الكهربائية كتقنية تستخدم لأخذ صورة مقطعية وذلك من خلال قياس الموصلية على سطح الجسم , بحيث تكون القيمة التقريبية لتوزيع المقاومة النوعية الداخلية مبنية عن طريق حساب فرق الجهد والتيار الكهربائي. التصوير المقطعي بالمعاوقة الكهربائية عند تردد معين يسمح بتصوير التغيرات فقط في الجزء الحقيقي من الموصلية ويهمل الجزء التخيلي منها والقيم المطلقة. وقد أقترح حلاً لهذه المشكلة باستخدام التصوير المقطعي متعدد التردد التصوير المقطعي بالمعوقة الكهربائية متعددة التردد يعطي صورة ثابتة بواسطة تكوين صورة لتغيير مقاومة الأنسجة مع التردد, ولغرض الحصول على كل المعلومات تم الأخذ في الاعتبار الجزء الحقيقي والتخيلي للموصلية في هذا البحت تم تطوير طريقة جديدة للتصوير الطبقي بالمعاوقة الكهربائية متعددة التردد باستخدام دوال لاجير الثنائية , وحيث أن تحسين صورة التصوير المقطعي بالمعاوقة الكهربائية يعتمد على كمية المعلومات التي يمكن الحصول عليها من القياسات الحدودية تم الأخذ في الاعتبار الجزء الحقيقي والتخيلي للموصلية لقد تم تطبيق هذه الطريقة والحصول على نتائج جيدة من حيث جودة الصورة مقارنة بنتائج تم الحصول عليها في أبحاث سابقة. Abstract Electrical Impedance Tomography (EIT) is a technique which allows cross- sectional image related to the electrical impedance within an object to be reconstructed from a set of measurements made on the object surface. EIT aims to image the conductivity distribution within a test object by making electrical measurements on the surface of the object. In single frequency Electrical Impedance Tomography only the change in the real part of the conductivity can be imaged and not those of the imaginary part of the conductivity or of the absolute values. Multi-frequency Electrical Impedance Tomography has been proposed to solve this problem. In this thesis, there is a new method using Laguerre function in multi-frequency Electrical Impedance Tomography which has been developed, and full information contained in the complex tissue conductivity can be obtained.
جلال مفتاح مهلهل (2009)

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.
احمد محمد التانزفتى (2013)

Abstract Wireless local area networks (WLANs) have been rapidly developed in recent years. It is used for various applications. VoWLAN, which transmits VoIP data over WLANs, shows its amazing attraction and constitutes one of the most flourishing applications nowadays in WLANs. One of Wireless Local Area Networks (WLAN) main drawbacks, when compared to wired networks, is that WLANs are less predictable and efficient. Wireless physical medium is harder to be controlled than physical wire. WLAN medium is also unlicensed, and thus susceptible to interferences produced by other devices. Therefore, great effort is being done in order to obtain Quality of Service (QoS) in real-time voice communications using WLANs. This topic has opened plenty of new research lines to upgrade current WLAN standards. In this thesis, a study is carried out for the behavior of new Medium Access Control (MAC) protocols defined in IEEE 802.11e draft standard Enhanced Distributed coordination function EDCF as well as for its subsequent modified versions. The Adaptive Enhanced Distributed coordination function AEDCF, designed to support QoS when providing voice communication services between stations in WLAN. Also presents experimental results obtained from simulations, and compare our results with simulations made using IEEE 802.11 standard MAC. The simulation work was done using NS-2 simulator, with the addition of specific modules for 802.11e. A performance comparison is carried out between the modified MAC scheme and IEEE standard MAC scheme, using Experimental simulation models. It is found that the adaptive technique method not only increases the medium utilization ratio and lowers the collision rate by more than 50%, but also enhances vii the overall throughput by around 20% compared with the basic IEEE 802.11DCF technique.
حسين ابراهيم ازويه (2010)