In this paper, we use concepts and results from percolation theory to investigate and characterize the effects of multi-channels on the connectivity of Dynamic Spectrum Access networks. In particular, we focus on the scenario where the secondary nodes have plenty of vacant channels to choose from-a phenomenon which we define as channel abundance. To cope with the existence of multi-channels, we use two types of rendezvous protocols: naive ones which do not guarantee a common channel and advanced ones which do. We show that, with more channel abundance, even with the use of either type of rendezvous protocol, it becomes difficult for two nodes to agree on a common channel, thereby potentially remaining invisible to each other. We model this invisibility as a Poisson thinning process and show that invisibility is even more pronounced with channel abundance. Following the disk graph model, we define and characterize connectivity of the secondary network in terms of the available number of channels, deployment densities, number of transceivers per node, and communication range. When primary users are absent, we derive the critical number of channels which maintains super-criticality of the secondary network. When primary users are present, we characterize and analyze the connectivity for all the regions: channel abundance, optimal, and channel deprivation. Our results can be used to decide on the goodness of any channel rendezvous algorithm by computing the expected resultant connectivity.
Praise be to God, Lord of the worlds, and prayers and peace be upon our master Muhammad and upon his family and companions.
We see human societies differ from one society to another in organizing social life, and each according to the foundations and rules prepared by the main thing in the welfare and prosperity.
That is why we see eastern societies differ from western societies in many patterns and various ways of reaching that sophistication, until Islam came and gave the proper model in raising society at that time to the best and highest social levels, because it is based on heavenly rules and foundations and not status as in previous civilizations.
And when the Islamic community has
Non thermal argon plasma needle at atmospheric pressure was constructed. The experimental set up was based on simple and low cost electric components that generate electrical field sufficiently high at the electrodes to ionize various gases which flow at atmospheric pressure. A high AC power supply was used with 9.6kV peak to peak and 33kHz frequency. The plasma was generated using two electrodes. The voltage and current discharge waveform were measured. The temperature of Ar gas plasma jet at different gas flow rate and distances from the plasma electrode was also recorded. It was found that the temperature increased with increasing frequency to reach the maximum value at 15 kHz, and that the current leading the voltage, which demonstra
... Show MoreA numerical and experimentally investigation for two types of winglets (spiroid and blended), which are used to reduce the induced drag caused by the trailing vortices were presented and discussed in this work. The SOLIDWORK 2016 was used to model a rectangular wing geometry of NACA2415 cross-sectional airfoil with blended and spiroid airfoils (2415 and 0012). The steady, incompressible N.S equations with standard (
the structrual and mechanical properties of thin Ni films of different thicknesses deposited on coring glass substrate using lonbeam sputtering(IBS) technique under vacuum torr have been studied the TEM and electron
The thirties and the early forties and the at end of the World War II of the last century
witnessed several attempts carried out by the Public Health Directorate and by the Iraqi
Ministry of Foreign Affairs to persuade the Rockefeller Foundation to fund Iraq with its
health program which is carried out in several regions in the world to promote the health and
social situations since Iraq during that period in history was badly in need to such plans and
programs because of this lack of financial and technical possibilities necessary for the
advancement of health and social dire situation.
The details of these attempts are deposited in the documents of the diplomatic mail
records of the United States of America , an
A number of juices, jams, canned foods and frozen fishes available in local markets were inspected with respect to microbial contamination. We have determined the total viable bacterial cell counts in these samples and the number of g(-) lactose fermentors as a bacterial indicator of food spoilage. The results indicated that most of the food items inspected, were contaminated with large numbers of different species of g(-) ,g(+), yeast and fungi and some were contained more than the maximum permissible number of pathogenic g(-) enteric E-coli, which render these food items unsafe for human consumption.
In this article, a short review on the feature of reality and locality in quantum optics is given.
The Bell inequality and the Bell states are introduced to show their direct use in quantum computer and
quantum teleportation. Moreover, quantum cryptography is discussed in some details regarding basic
ideas and practical considerations. In addition, a case study involving distillation of a quantum key based
on the given fundamentals is presented and discussed.
The importance of the research lies in developing flexibility exercises (positive and negative) that help improve the level of physical and skill performance, address some weak points, and develop factors that work to implement skills with a wider range of motion, accuracy, and high strength. This is what makes the game of badminton more developed and successful. Performing (dimensions) strokes And the forward projection) by not using the wrist and the correct movement of the striking arm. This makes the player’s performance ineffective, which requires her to practice flexibility and movement flow to address this weakness. The study aims to prepare exercises using flexibility (positive and negative) and to know the e
... Show MoreBlood and urine samples were collected from 203 patients to study the relationship between Diabetes mellitus and urinary tract infections (UTI). Blood and urine specimens were subjected for estimation of random blood sugar, in addition to detection of the most pathogen bacteria which cause urinary tract infection in diabetic patients. The study included the detection of bacterial sensitivity to some antibiotics used in treating urinary tract infections, and also included the study of genetic basis which cause both types of diabetes mellitus. The results can be summarized as follows: The incidence of type ? diabetes in males was (35.8%), and (45.9%) in females . and type 2 diabetes in males was (49.6%), while in females was (40.16%).The inc
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