Hard Decision Cooperative Spectrum Sensing Based on Estimating the Noise Uncertainty Factor

Spectrum Sensing (SS) is one of the most challenging issues in Cognitive Radio (CR) systems. Cooperative Spectrum Sensing (CSS) is proposed to enhance the detection reliability of a Primary User (PU) in fading environments. In this paper, we propose a hard decision based CSS algorithm using energy detection with taking into account the noise uncertainty effect. In the proposed algorithm, two dynamic thresholds are toggled based on predicting the current PU activity, which can be successfully expected using a simple successive averaging process with time. Also, their values are evaluated using an estimated value of the noise uncertainty factor. These dynamic thresholds are used to compensate the noise uncertainty effect and increase (decrease) the probability of detection (false alarm), respectively. Theoretical analysis is performed on the proposed algorithm to deduce its enhanced false alarm and detection probabilities compared to the conventional hard decision CSS. Moreover, simulation analysis is used to confirm the theoretical claims and prove the high performance of the proposed scheme compared to the conventional CSS using different fusion rules.Comment: 5 pages, 4 figures, IEEE International Conference on Computer Engineering and Systems (ICCES 2015). arXiv admin note: text overlap with arXiv:1505.0558

Harvesting Energy of Radio Frequency

Renewable Energy sources are the center of attraction for research and development all over the world nowadays. Oil and Gas are no more the main source of Energy, consequently the demand of a lasting cheap source of energy that is environmental friendly, is the main challenge recently. During the last decade, power consumption has decreased opening the field for energy harvesting to become a real time solution for providing different sources of electrical power. Energy Harvesting is a new technology that is going to make a revolution in the coming decade. Energy Harvesting is a technique to provide alternative sources of energy that are environmental friendly and low in cost. Radio Frequency Energy Harvesting is one of the methods to provide electrical energy from the ambient Radio Frequency Energy that already exists in the environment. For example Hand phones can be directly charged from Radio frequencies in the environment like 915 MHz. Laptops can be charged by frequencies like 2.45 GHz. RFID passive tags can be powered by these radio frequencies without the supply of any batteries increasing the range of passive RFID tags to longer distances with lower cost. Radio Frequency Energy Harvesting can provide a world with batteryless devices. With RF Energy Harvesting, the true mobility can be achieved where mobile devices do not depend on centralized power sources for charging. Instead they make use of the existing energy in the environment

Analysis of Petri nets by partitioning: Splitting transitions

AbstractIn this paper, a method of analysis of large Petri nets by partitioning is proposed. This method permits a great saving of computation time and storage. Useless efforts spent in the analysis of large Petri nets are spared by a look to the partitions of interest. It is possible to study the characteristics of the required places by involving them in a partition. It was shown that partitioning preserves the characteristics of the main Petri net. The reachability tree method or the matrix equations approach, which were untractable at the whole net level, may be used at the subnet level to get the needed analysis criteria

Soft Decision Cooperative Spectrum Sensing Based Upon Noise Uncertainty Estimation

Spectrum Sensing (SS) constitutes the most critical task i n Cognitive Radio (CR) systems for Primary User (PU) detection. Cooperative Spectrum Sensing (CSS) is introduced to enhance the detection reliability of the PU in fading environments. In this paper, we propose a soft decision based CSS algorithm using energy detection by taking into account the noise uncertainty effect. In the proposed algorithm, two threshold levels are utilized based on predicting the current PU activity, which can be successfully expected using a simple successive averaging process with time. The two threshold levels are evaluated based on estimating the noise uncertainty factor. In addition, they are toggled in a dynamic manner to compensate the noise uncertainty effect and to increase the probability of detection and decrease the probability of false alarm. Theoretical analysis is performed on the proposed algorithm to evaluate its enhanced false alarm and detection probabilities over the conventional soft decision CSS using different combining schemes. In addition, simulation results show the high efficiency of the proposed scheme compared to the conventional soft decision CSS, with high computational complexity enhancements.Comment: 6 Pages, 5 Figures, ICC workshops 201

Attitudes towards Architectural Conservation: The Case of Cairo

This research is arranged in seven chapters, grouped in four parts. The methodology followed in each chapter is explained in its separate introduction. Part one: History of conservation in Cairo, is divided in two chapters. The Napoleonic Expedition to Egypt in 1798AD is used as a symbol for the changes that happened in attitudes. Chapter 1 tackles Pre-Napoleon attitudes, whereas Chapter 2 tackles Post-Napoleon attitude. Methodology used in the two chapters is totally different: The absence of any previous study on attitudes in Pre-Napoleon Cairo, made it necessary to use a method of analysis and observations on certain buildings in order to extract attitudes of the time. Whereas Chapter 2 is a mere collection of observations and writings on Post-Napoleon attitudes. Part two: Different aspects of conservation, is divided in three chapters. Chapter 3, ideological and cultural aspects, discusses the influence of the ideology of Islam and the cultural characteristics of Arabic on attitudes. This chapter is inherently controversial, as it tackles the heart of Speiser's question. And unavoidably it challenges a well established branch of Western academia. Orientalism. Chapter 4, Social, economic and cultural aspects, addresses the particular development / conservation attitudes, problems, and possibilities in Cairo. The main approach of this chapter is to learn from the informal sector how to survive through hardships. Chapter 5, Technical aspects, reviews problems of Cairo on different scales without losing sight of other aspects of conservation, which do affect attitudes. Part three, Attitudes to architectural conservation, consists of one chapter. Chapter 6, Range of possible attitudes, acknowledges the wide range of possible attitudes. A study trip to Cairo, Damascus, Lahore, and San'a' made it possible to meet theoretically possible attitudes with actual existing attitudes. The collection of theoretically possible attitudes, is the result of previous conservation education and experience, as well as the heated discussions with Tony Vogt, lecturers, and students at the Mackintosh School of Architecture. Part four, Case study consists also of one chapter. Chapter 7, The mosque of Ulmas, brings together the findings of the present research in a practical way. It proposes a new approach to the conservation of Ulmas mosque. The proposal is essentially open-ended project which has to be finalised during the course of its application, so that it leaves room for local attitudes to participate. The conclusions highlight the strong and weak points of the research, and summarises its findings. (Abstract shortened by ProQuest.)

Effect of Abutments Design on Wear of Locator Attachments in Implant Retained Mandibular Overdenture.

Purpose: The aim of this study is to compare the effect of abutments design on wear behavior of Locator attachments in implant-retained mandibular overdenture. Materials and Methods: Two epoxy models representing an edentulous mandible were used, two implants were placed in each model. Twenty-four locator attachments were used (twelve in each study group). Cycles of Insertion and removal were performed using a universal testing machine resembling 3 years of clinical use, then each abutment was scanned by scanning electron microscope (SEM) before and after insertion and removal cycles. Data were compared qualitatively using a specialized computer software Results: There was a statistically significant difference in wear between the two studied locator groups P=0000*. Locator F-TX showed 29±1.704 % of surface change. PEEKLOC. Locator showed 21±2.090 %of surface change. Conclusions: PEEKLoc. abutment design showed more wear resistance than the recently introduced Locator F-TX

Staff perceptions of service quality in Egyptian commercial banks : an internal and external perspective

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