In this paper, we investigate and characterize the effects of multi-channel and rendezvous protocols on the connectivity of dynamic spectrum access networks using percolation theory. 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-channel, 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 protocols, 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 represent the multiple channels as parallel edges in a graph and build a multi-layered graph (MLG) in R2. In order to study the connectivity, we show how percolation occurs in the MLG by coupling it with a typical discrete percolation. Using a Boolean model and the MLG, we study both cases of primaries' absence and presence. For both cases, we define and characterize connectivity of the secondary network in terms of the available number of channels, deployment densities, number of simultaneous transmissions per node, and communication range. When primary users are absent, we derive the critical number of channels which maintains supercriticality 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. For each region we show the requirement and the outcome of using either type of rendezvous techniques. Moreover, we find the tradeoff between deployment-density versus rendezvous probability which results in a connected network. Our results can be used to decide on the goodness of any channel rendezvous algorithm by computing the expected resultant connectivity. They also provide a guideline for achieving connectivity using minimal resources.
The research came in order to take note of the types of inscription and to clarify its provisions and to show some of the possibilities of Islamic law in the sales side and its ability to influence in Islamic markets, and to achieve the required level and appropriate of the transactional results by activating them in economic life, and give a clear picture of the performance of selling in the law and the possibility of applying one of Its uses in this aspect, and enable them to take advantage of the method of explicitly sell without the injustice of others as one of those useful sales uses.
Al-Manas and Al-Muhais are two words in a close sense of the strange words of the Holy Quran. The word Al-Manas was mentioned once in the Holy Qur'an in Surat (PBUH). ) / 36 .. What we will see in the folds of the search, God willing.
This paper describes the use of microcomputer as a laboratory instrument system. The system is focused on three weather variables measurement, are temperature, wind speed, and wind direction. This instrument is a type of data acquisition system; in this paper we deal with the design and implementation of data acquisition system based on personal computer (Pentium) using Industry Standard Architecture (ISA)bus. The design of this system involves mainly a hardware implementation, and the software programs that are used for testing, measuring and control. The system can be used to display the required information that can be transferred and processed from the external field to the system. A visual basic language with Microsoft foundation cl
... Show MoreBackground: footballers may have poor oral health like elevated levels of dental caries. The purpose of this study was to estimate the prevalence and severity of dental caries in Iraqi footballers and to measure dental treatments needs. Materials and methods: 403 Iraqi males footballers aged from 18-32 years were included in the study. The cases were recruited from 18 clubs in Baghdad city. Results: the results of present study showed increased percent of caries experience according to age increase and decreased dental caries percent as education level increased among Iraqi footballers. Decayed component was found to be the largest of DMFS value compared to MS and FS among all age groups, Caries experience was found to be increased as age
... Show Moreتتبلور فكرة البحث حول التوصل لنوع العلاقة التي تربط التعليم الالكتروني خلال جائحة كورونا برفع المهارات التكنولوجية للأساتذة والطلاب، وتبرز أهمية البحث في ان نجاح الوصول لهذه العلاقة يمكن الإفادة منها في تغيير منهجية تطوير المهارات التكنولوجية مستقبلا وذلك باعتماد الجوانب التطبيقية الفعلية بدلا من الدورات وورش العمل والتي قد لا تضاهي الطريقة العملية في رفع مستوى المهارات المختلفة سواء التدريسية او التكنو
... Show MoreTaliban has returned to the forefront since regaining control of Afghanistan in mid-August 2021, prompting the international community and researchers to speculate whether it has adopted a different political vision and ideology from its previous rule (1996-2001). The previous rule presented a distorted version of governance that lacked clear political and ideological foundations, characterized by impulsive and chaotic decisions, and the absence of a comprehensive theoretical and intellectual framework for governance.
Once again, Taliban returned to power on August 15, 2021, and took control of the country. This raised many questions about Taliban's return, the extent of its flexibility and adaptability that allowed the movement t
... Show MoreIn this work, two different structures are proposed which is fuzzy real normed space (FRNS) and fuzzy real Pre-Hilbert space (FRPHS). The basic concept of fuzzy norm on a real linear space is first presented to construct space, which is a FRNS with some modification of the definition introduced by G. Rano and T. Bag. The structure of fuzzy real Pre-Hilbert space (FRPHS) is then presented which is based on the structure of FRNS. Then, some of the properties and related concepts for the suggested space FRN such as -neighborhood, closure of the set named , the necessary condition for separable, fuzzy linear manifold (FLM) are discussed. The definition for a fuzzy seminorm on is also introduced with the prove that a fuzzy seminorm on
... Show MoreEach Arab Islamic city is distinguished by its distinctive characteristics dictated by the nature of its location and its characteristics, as we see it mountainous in the mountains, deserts in the deserts, and coastal in the coasts, and this is reflected in the models of its buildings and designs and even in its structure. However, this uniqueness did not stand in the way of the emergence of characteristics and common characteristics of these cities over time, the factors derived from the core of the life of the community habits and traditions and beliefs and living requirements and environmental conditions that all piled in the process of building and construction of the Arab Islamic city to draw The features and lines of life of the co
... Show MoreBiped robots have gained much attention for decades. A variety of researches has been conducted to make them able to assist or even substitute for humans in performing special tasks. In addition, studying biped robots is important in order to understand the human locomotion and to develop and improve control strategies for prosthetic and orthotic limbs. Some challenges encountered in the design of biped robots are: (1) biped robots have unstable structures due to the passive joint located at the unilateral foot-ground contact. (2) They have different configuration when switching from walking phase to another. During the singlesupport phase, the robot is under-actuated, while turning into an over-actuated system during the double-support pha
... Show MoreGeneral Background: Deep image matting is a fundamental task in computer vision, enabling precise foreground extraction from complex backgrounds, with applications in augmented reality, computer graphics, and video processing. Specific Background: Despite advancements in deep learning-based methods, preserving fine details such as hair and transparency remains a challenge. Knowledge Gap: Existing approaches struggle with accuracy and efficiency, necessitating novel techniques to enhance matting precision. Aims: This study integrates deep learning with fusion techniques to improve alpha matte estimation, proposing a lightweight U-Net model incorporating color-space fusion and preprocessing. Results: Experiments using the AdobeComposition-1k
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