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Дисертації з теми "Informatique omniprésente – Radio cognitive"
Mortada, Mohamad Rida. "Multi-hop routing for cognitive radio sensor network." Thesis, Brest, École nationale supérieure de techniques avancées Bretagne, 2021. http://www.theses.fr/2021ENTA0010.
Повний текст джерелаThe Wireless Sensor Network (WSN) consists of a large number of tiny devices called nodes, and these nodes are generally limited in power and they are randomly deployed in a geographical area for monitoring purpose. Because of the large number of nodes in the WSN, their demand on the frequency resources becomes a real challenge due to the spectrum scarcity. Cognitive Radio (CR) was introduced to enhance the spectral efficiency. The CR classifies users into the Primary User (PU) that holds a license over a spectrum bandwidth, and the Secondary User (SU), i.e., an opportunistic user. The integration of CR into WSN results in a cognitive radio sensor network (CRSN). In CRSN, the nodes behave as SUs. However,the adoption of CRSN may face several challenges. Indeed, network nodes may stop transmitting to avoid any harmful interference for PU. In addition, energy consumption constraint should be respected. Other features may be impacted by the adoption of CRSN, such as the clustering process and the in-network data aggregation, especially in a multi-hop routing based CRSN. In this manuscript, we tackle the challenges of the CRSN from different levels. Firstly, clustering nodes enhances network efficiency. In practice, grouping the network nodes saves energy during data transmission. Thus, we investigate the optimal number of clusters in the network based on energy consumption during data transmission and spectrum sensing to extend network lifespan. Then, we present LIBRO, a new uplink multi-hop routing protocol based on the geographical location information. LIBRO ensures delivery of rectified data packets in dense networks without knowledge of topology or path nodes. Finally, we used LIBRO and the energy harvesting technique to extend the CRSN's lifespan. Thus, by solving an optimization problem jointing the collision probability, energy consumption, packet delivery delay and packet delivery ratio, the appropriate parameters are found
To, Ba Lam. "Contrôle de puissance et routage dans les réseaux ad-hoc à radio cognitive." Paris 6, 2012. http://www.theses.fr/2012PA066294.
Повний текст джерелаA large number of wireless services have been introduced over the last decade to satisfy new demands of mobile users. However, the proliferation of wireless computing and communication devices make the radio spectrum overcrowded. It is revealed in the Federal Communication Commission report that many spectrum bands are used only in bounded geographical areas or over limited periods of time, and that the spectrum utilization varies from 15% to 85%. As a consequence, the Cognitive Radio Networks (CRNs) have been introduced as a new alternative wireless communication paradigm to utilize the radio spectrum more efficiently. In this dissertation, we investigate the power control and routing perspectives to enhance the network performance and power utilization in CRN. First, aiming to enhance the network performance by deploying a proper network topology for a particular communication purpose, we propose a topology deployment oriented power control scheme for cognitive radio ad-hoc network. Second, to tackle the problem of the frequent arrival and leaving of primary users which can lead to the heavy traffic overhead caused by re-routing, we propose a new approach for joint flow maintenance and power control, called flow-based power control, for cognitive radio ad-hoc network. The power control scheme targets on to utilize the power resource more efficiently by only allocating power resource to the maintained flows. Finally, we propose an application-oriented routing protocol (AORP) in cognitive radio ad-hoc network. AORP builds the route for data transmission in combination with channel selection based on the application of the node initializing the data transmission
Rehmani, Mubashir Husain. "Opportunistic Data Dissemination in Ad-Hoc Cognitive Radio Networks." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2011. http://tel.archives-ouvertes.fr/tel-00630214.
Повний текст джерелаWu, Xiguang. "Hierarchical reconfiguration management for heterogeneous cognitive radio equipments." Thesis, CentraleSupélec, 2016. http://www.theses.fr/2016SUPL0002/document.
Повний текст джерелаAs the digital communication systems evolve from GSM and now toward 5G, the supported standards are also growing. The desired communication equipments are required to support different standards in a single device at the same time. And more and more wireless Internet services have been being provided resulting in the explosive growth in data traffic, which increase the energy consumption of the communication devices thus leads to significant impact on global CO2 emission. More and more researches have focused on the energy efficiency of wireless communication. Cognitive Radio (CR) has been considered as an enabling technology for green radio communications due to its ability to adapt its behavior to the changing environment. In order to efficiently manage the sensing information and the reconfiguration of a cognitive equipment, it is essential, first of all, to gather the necessary metrics so as to provide enough information about the operating condition thus helping decision making. Then, on the basis of the metrics obtained, an optimal decision can be made and is followed by a reconfiguration action, whose aim is to minimize the power dissipation while not compromising on performance. Therefore, a management architecture is necessary to be added into the cognitive equipment acting as a glue to realize the CR capabilities. We introduce a management architecture, namely Hierarchical and Distributed Cognitive Radio Architecture Management (HDCRAM), which has been proposed for CR management by our team. This work focuses on the implementation of HDCRAM on heterogeneous platforms. One of the objectives is to improve the energy efficiency by the management of HDCRAM. And an example of a simplified OFDM system is used to explain how HDCRAM works to efficiently manage the system to adapt to the changing environment
Lertsinsrubtavee, Adisorn. "Sélection et transfert de spectre adaptatifs dans les réseaux de radio cognitive." Paris 6, 2013. http://www.theses.fr/2013PA066300.
Повний текст джерелаCognitive radio is proposed as a promising solution for the next generation of wireless communication networks. Cognitive radio users are required to perform spectrum handoff from a wireless channel to another in order to cope with the dynamic spectrum environment imposed by licensed users. Spectrum handoff can cause transmission interruptions leading to the degradation of services. We study and develop efficient spectrum management strategies that aim to provide diverse service requirements for cognitive radio users. First, we propose novel spectrum handoff and selection strategies in order to satisfy a delay requirement. In particular, we estimate the delay of arrival packets based on the prior packets in the queue and compare it to a maximum delay bound. Then, we use the expected delays to estimate a delay violation ratio that guides the spectrum handoff and selection decisions. Our strategies reduce the number of spectrum handoff significantly compared to existing approaches while the delay requirement is guaranteed. Second, we consider the rate requirement by investigating the interaction between spectrum handoff and spectrum sharing through an optimization framework. The results provide useful insights and guidelines for designing efficient spectrum sharing heuristics that take into account spectrum handoff and selection strategies. Finally, we develop a heuristic for spectrum sharing that includes novel static and dynamic spectrum sharing algorithms based essentially on a rate compensation approach and adapted best fit algorithms. Our heuristic reduces the number of handoffs significantly while the achieved rate is fulfilling compared to the optimal
Jin, Xin. "Resource allocation in multicarrier cognitive radio networks." Thesis, Evry, Institut national des télécommunications, 2014. http://www.theses.fr/2014TELE0014/document.
Повний текст джерелаIn view of the wide usage of multicarrier modulation in wireless communications and the prominent contribution of Cognitive Radio (CR) to deal with critical shortage of spectrum resource, we focus on multicarrier based cognitive radio networks to investigate general resource allocation issues: subcarrier allocation, power allocation, routing, and beamforming in this thesis. We investigate two types of multicarrier modulation: Wavelet-based Orthogonal Frequency Division Multiplexing (WOFDM) and Fourier-based Orthogonal Frequency Division Multiplexing (OFDM). WOFDM adopts Wavelet Packet Modulation (WPM). Compared with fourier-based OFDM, wavelet-based OFDM achieves much lower side lobe in the transmitted signal. Wavelet-based OFDM excludes Cyclic Prefix (CP) which is used in fourier-based OFDM systems. Wavelet-based OFDM turns to exploit equalization to combat Inter-Symbol Interference (ISI). We evaluate the performance of WOFDM under different channel conditions. We compare the performance of wavelet-based OFDM using equalization in the time domain to that of fourier-based OFDM with CP and the equalization in the frequency domain
Godard, Loïg. "Modèle de gestion hiérarchique distribuée pour la reconfiguration et la prise de décision dans les équipements de radio cognitive." Rennes 1, 2008. https://tel.archives-ouvertes.fr/tel-00355352.
Повний текст джерелаThis work focuses on the implementation of a management architecture for cognitive radio equipment for applications in the field of radiocommunications. The architecture is named HDCRAM (Hierarchical and Distributed Cognitive Radio Architecture Management). HDCRAM is hierarchically distributed in the equipment to take into account heterogeneity of execution platforms. Thanks to a precise management for both reconfiguration and decision-making leading to a reconfiguration of all or part of the system. Through the use of UML language, for high level of abstraction modeling, we define a platform independent model of HDCRAM which offers an extended opportunity in terms of reusability and modularity. The choice to use an executable metamodeling language as Kermeta for HDCRAM allows describing both structural and behavioral part of our architecture and gives the opportunity to make functional simulation
Dominici, Michele. "Contributing to energy efficiency through a user-centered smart home." Phd thesis, Université Rennes 1, 2013. http://tel.archives-ouvertes.fr/tel-00869455.
Повний текст джерелаHussain, Sajjad. "PEAK TO AVERAGE POWER RATIO ANALYSIS AND REDUCTION OF COGNITIVE RADIO SIGNALS." Phd thesis, Université Rennes 1, 2009. http://tel.archives-ouvertes.fr/tel-00426930.
Повний текст джерелаSekhraoui, Majid. "Concordances : histoire, méthodes et pratique." Paris 3, 1995. http://www.theses.fr/1996PA030040.
Повний текст джерелаThe concordance is a means of exploring a text. This tool provides an alphabetical list of words with their context. The oldest known concordance appears at the beginning of the 13th century. At the end of the 20th century, the concordance remains more alive than ever. Where does its longevity comes from? this long-established tool has always been able to adapt itself and to modernize itself in order to meet the needs of its users. The first of these had in common an interest in the thorough study of the bible which they read either in latin, greek or in hebrew. That is why the concordances were set up in these languages and remained for a long time a tool exclusively linked to the bible. One has to wait until the end of the 18th century for it to be used for other texts besides the scriptures. We have trie d to show why the concordances came to light, what needs the met originally and how they evolved. Since the 13th century , people have been working away at this long and tedious undertaking, first "by hand", then helped by the arrival of of printing and finally by that of the machine. However they always had to face the same problems. Technological progess have imposed the use of the computer which enabled the development of the way the concordance were to be tackled. From now on, people are no longer interested in consulting long lists of words and theirs contexts, but it is the study of the forms and its links with its environment which is of interest. That is what is set out with the software "saint chef". The concordance software can be further improved in the future in order to make them more user-friendly and more flexible