Dissertations / Theses on the topic 'Mobile and Cognitive Radios'
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Hong, Xuemin. "Secondary mobile access via ultra-wideband and cognitive radio networks." Thesis, Heriot-Watt University, 2008. http://hdl.handle.net/10399/2196.
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He, An. "Power Consumption Optimization: A Cognitive Radio Approach." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77309.
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Power consumption is one of the most important aspects in mobile and wireless communications. Existing research has shown significant power reduction through limited radio reconfiguration based on the channel conditions, especially for short range sensor network applications.
A cognitive radio (CR) is an intelligent wireless communication system which is able to determine the most favorable operating parameters (cognition) based on the radio environment and its own capabilities and characteristics (awareness) and reconfigure the radio accordingly (reconfigurability).
This work leverages the advances in cognitive radio technology to dynamically implement favorable trade-offs in radio parameters to achieve more efficient use of radio resource (e.g., minimizing power consumption) on the required Quality of Service (QoS) of an application and channel. A CR-based approach enables us not only to adjust modulation, coding, and radiated power as in a conventional radio, but also to learn and to control component characteristics (e.g., the power amplifier (PA) efficiency characteristic) to minimize power consumption. Significant power savings using this approach are shown in this work for single input single output (SISO) systems and multiple input multiple output (MIMO) systems.
This work has a broad potential impact on the research of improving power efficiency of communication systems. It establishes a cognitive radio based methodology for system power consumption optimization. It emphasizes the difference between radiated power (power radiated from the transmit antenna) and the consumed power (power drawn from the power source, such as a battery). It provides a way to connect communication (which usually cares about radiated power, received signal to noise ratio, etc.) to hardware (which focuses on speed, efficiency, power consumption, etc.) and software (which emphasizes complexity, speed, etc.). This design methodology enhances the capability to jointly optimize communication, hardware, and software. In addition, this CR-based framework can be adapted for general radio resource management with various radio operation optimization targets, such as spectrum utilization.Ph. D.
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Li, Xue. "Spectrally Modulated Spectrally Encoded Framework Based Cognitive Radio in Mobile Environment." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1365964727.
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Zhou, Ruolin. "The Demonstration of SMSE Based Cognitive Radio in Mobile Environment via Software Defined Radio." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1334421582.
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Raoof, Omar. "Game theory for dynamic spectrum sharing cognitive radio." Thesis, Brunel University, 2010. http://bura.brunel.ac.uk/handle/2438/7371.
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‘Game Theory’ is the formal study of conflict and cooperation. The theory is based on a set of tools that have been developed in order to assist with the modelling and analysis of individual, independent decision makers. These actions potentially affect any decisions, which are made by other competitors. Therefore, it is well suited and capable of addressing the various issues linked to wireless communications. This work presents a Green Game-Based Hybrid Vertical Handover Model. The model is used for heterogeneous wireless networks, which combines both dynamic (Received Signal Strength and Node Mobility) and static (Cost, Power Consumption and Bandwidth) factors. These factors control the handover decision process; whereby the mechanism successfully eliminates any unnecessary handovers, reduces delay and overall number of handovers to 50% less and 70% less dropped packets and saves 50% more energy in comparison to other mechanisms. A novel Game-Based Multi-Interface Fast-Handover MIPv6 protocol is introduced in this thesis as an extension to the Multi-Interface Fast-handover MIPv6 protocol. The protocol works when the mobile node has more than one wireless interface. The protocol controls the handover decision process by deciding whether a handover is necessary and helps the node to choose the right access point at the right time. In addition, the protocol switches the mobile nodes interfaces ‘ON’ and ‘OFF’ when needed to control the mobile node’s energy consumption and eliminate power lost of adding another interface. The protocol successfully reduces the number of handovers to 70%, 90% less dropped packets, 40% more received packets and acknowledgments and 85% less end-to-end delay in comparison to other Protocols. Furthermore, the thesis adapts a novel combination of both game and auction theory in dynamic resource allocation and price-power-based routing in wireless Ad-Hoc networks. Under auction schemes, destinations nodes bid the information data to access to the data stored in the server node. The server will allocate the data to the winner who values it most. Once the data has been allocated to the winner, another mechanism for dynamic routing is adopted. The routing mechanism is based on the source-destination cooperation, power consumption and source-compensation to the intermediate nodes. The mechanism dramatically increases the seller’s revenue to 50% more when compared to random allocation scheme and briefly evaluates the reliability of predefined route with respect to data prices, source and destination cooperation for different network settings. Last but not least, this thesis adjusts an adaptive competitive second-price pay-to-bid sealed auction game and a reputation-based game. This solves the fairness problems associated with spectrum sharing amongst one primary user and a large number of secondary users in a cognitive radio environment. The proposed games create a competition between the bidders and offers better revenue to the players in terms of fairness to more than 60% in certain scenarios. The proposed game could reach the maximum total profit for both primary and secondary users with better fairness; this is illustrated through numerical results.
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Bennis, M. (Mehdi). "Spectrum sharing for future mobile cellular systems." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514260582.
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Spectrum sharing has become a high priority research area over the past few years. The motivation behind this lies in the fact that the limited spectrum is currently inefficiently utilized. As recognized by the World radio communication conference (WRC)-07, the amount of identified spectrum is not large enough to support large bandwidths for a substantial number of operators. Therefore, it is paramount for future mobile cellular systems to share the frequency spectrum and coexist in a more efficient manner.
The present dissertation deals with the problem of spectrum scarcity by examining spectrum sharing paradigms where a migration from fixed to flexible resource allocation is investigated. First, a radio resource management (RRM) architecture is proposed where advanced spectrum functionalities accounting for the short-term variations of the spectrum are examined. The achievable gains are shown in a multi-cell, multi-network environment with realistic traffic patterns from a European operator, enhancing thereby spectrum utilization. Second, inter-operator resource sharing in a broadband network is considered where a packet-based cellular network is developed. It is shown that the obtained gains in terms of quality-of-service (QoS), number of operators and different data rates requirements improve the overall efficiency of the network. Besides and in order to cope with the stringent data rate requirements, direct terminal-to-terminal (T2T) communication is examined in which a realistic algorithm is proposed advocating resource reuse in a cellular system with simultaneous communications between mobiles. Numerical results confirm the advantages of resource reuse in terms of throughput, average frame delays and power consumption.
In this thesis, a proposal is made as how to enhance spectrum sharing. The concept of hierarchy is proposed in which wireless competitive operators share the same spectrum band. The decentralized hierarchical approach is shown to bridge the gap between the selfish and centralized approach.
Interference avoidance is studied for point-to-point communication in a selforganized network where different optimal power allocation strategies are examined along with the impact of frequency reuse on the ergodic capacity of the network.
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Rogers, William James. "Cross-Layer Game Theoretic Mechanism for Tactical Mobile Networks." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/24767.
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In recent years, Software Defined and Cognitive Radios (SDRs and CRs) have become popular topics of research. Game theory has proven to be a useful set of tools for analyzing wireless networks, including Cognitive Networks (CNs). This thesis provides a game theoretic cross-layer mechanism that can be used to control SDRs and CRs. We have constructed an upper-layer Topology Control (TC) game, which decides which links each node uses. A TDMA algorithm which we have adapted is then run on these links. The links and the TDMA schedule are then passed to a lower-layer game, the Link Adaptation Game (LAG), where nodes adjust their transmit power and their link parameters, which in this case are modulation scheme and channel coding rate. It is shown that both the TC game and the LAG converge to a Nash Equilibrium (NE). It is also shown that the solution for the TC game approximates the topology that results from maximizing the utility function when appropriate link costs are used. Also seen is the increase in throughput provided by the LAG when compared to the results of Greedy Rate Packing (GRP).Master of Science
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Bonnefoi, Rémi. "Utilisation de la radio intelligente pour un réseau mobile à faible consommation d’énergie." Thesis, CentraleSupélec, 2018. http://www.theses.fr/2018CSUP0001.
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La réduction de l’empreinte carbone de l’activité humaine est aujourd’hui un enjeu économique et écologique majeur. Les réseaux de communication ont un double rôle à jouer dans cette réduction. En premier lieu, les réseaux mobiles, et en particulier les stations de base, sont un gros consommateur d’électricité. Il est donc nécessaire d’optimiser leur fonctionnement pour réduire leur empreinte carbone. Ensuite, des réseaux de communication sont désormais nécessaires pour mieux gérer la production d’électricité et ainsi pouvoir augmenter la proportion d’électricité produite par des sources d’énergie renouvelables.Dans cette thèse, nous regardons ces deux aspects. Nous commençons par proposer une solution pour réduire la consommation d’énergie des réseaux mobiles. Pour cela, nous proposons des algorithmes pour optimiser l’allocation de puissance lorsque des mécanismes de mise en veille dynamique sont utilisés. Dans un second temps, nous proposons une solution pour améliorer le fonctionnement des réseaux d’objets connectés utilisés pour la gestion de l’électricité. Plus précisément, nous rendons plus fiables ces communications grâce à l’utilisation d’algorithmes de bandit multibras pour l’accès fréquentielThe reduction of the carbon footprint of human activities is one of the current major economic and ecological challenges. Communication networks have a dual role in this reduction. On one hand, mobile networks, and in particular the base stations, are nowadays an important energy consumer. It is, thus, necessary to optimize their behavior in order to reduce their carbon footprint. On the other hand, some communication networks are necessary to better manage the electrical grid. Thanks to this better management, it is possible to improve the proportion of electricity produced by renewable energy sources.In this thesis, we look at both aspects. In a first step, we propose a solution to reduce the energy consumption of wireless mobile networks. For that purpose, we propose algorithms that optimize the power allocation when Cell Discontinuous Transmission is used by the base stations.In a second step, we propose a solution in order to improve the performance of Internet of Things networks used for the electrical grid. More precisely, we use multi-armed bandit algorithm for channel selection in IoT networks as a means of increasing the reliability of communications
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Afgani, Mostafa Z. "Exploitation of signal information for mobile speed estimation and anomaly detection." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/4890.
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Although the primary purpose of the signal received by amobile handset or smartphone is to enable wireless communication, the information extracted can be reused to provide a number of additional services. Two such services discussed in this thesis are: mobile speed estimation and signal anomaly detection. The proposed algorithms exploit the propagation environment specific information that is already imprinted on the received signal and therefore do not incur any additional signalling overhead. Speed estimation is useful for providing navigation and location based services in areas where global navigation satellite systems (GNSS) based devices are unusable while the proposed anomaly detection algorithms can be used to locate signal faults and aid spectrum sensing in cognitive radio systems. The speed estimation algorithms described within this thesis require a receiver with at least two antenna elements and a wideband radio frequency (RF) signal source. The channel transfer function observed at the antenna elements are compared to yield an estimate of the device speed. The basic algorithm is a one-dimensional and unidirectional two-antenna solution. The speed of the mobile receiver is estimated from a knowledge of the fixed inter-antenna distance and the time it takes for the trailing antenna to sense similar channel conditions previously observed at the leading antenna. A by-product of the algorithm is an environment specific spatial correlation function which may be combined with theoretical models of spatial correlation to extend and improve the accuracy of the algorithm. Results obtained via computer simulations are provided. The anomaly detection algorithms proposed in this thesis highlight unusual signal features while ignoring events that are nominal. When the test signal possesses a periodic frame structure, Kullback-Leibler divergence (KLD) analysis is employed to statistically compare successive signal frames. A method of automatically extracting the required frame period information from the signal is also provided. When the signal under test lacks a periodic frame structure, information content analysis of signal events can be used instead. Clean training data is required by this algorithm to initialise the reference event probabilities. In addition to the results obtained from extensive computer simulations, an architecture for field-programmable gate array (FPGA) based hardware implementations of the KLD based algorithm is provided. Results showing the performance of the algorithms against real test signals captured over the air are also presented. Both sets of algorithms are simple, effective and have low computational complexity – implying that real-time implementations on platforms with limited processing power and energy are feasible. This is an important quality since location based services are expected to be an integral part of next generation cognitive radio handsets.
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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.
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Les progrès récents des technologies de communication et la prolifération de l'informatique sans fil et des dispositifs de communication, ont induit 'a une surcharge dans l'utilisation du spectre radio. Cependant, les expériences de la Commission Fédérale de Communication (FCC) ont révélé que l'utilisation du spectre varie entre 15% et 85%. Par conséquent, les réseaux radios cognitifs (Cognitive Radio Networks ou CRNs) sont proposés afin d'utiliser le spectre radio d'une manière opportuniste. Dans ce type de réseaux radios cognitifs, où les fréquences de transmission sont sélectionnées d'une manière opportuniste - également sont appelés réseaux Ad-Hoc à radios cognitives -, la fiabilité de la dissémination des données est difficile 'a réaliser. D'abord, en plus des défis déjà connus dans les environnements sans fils, la diversité dans le nombre de fréquences qu'un noeud à radio cognitif a droit d'utiliser ajoute un autre défi, en limitant l'accessibilité à ses noeuds voisins. Deuxièmement, les noeuds à radio cognitif (CR) doivent conquérir les ressources de fréquences résiduelles avec les noeuds à radio primaire (PR), tout en essayent de les exploiter d'une manière opportuniste. En outre, les noeuds CR ne devraient pas perturber la qualité de réception des noeuds PR durant leur communication, et ce en limitant les interférences entre les deux de noeuds. Par conséquent, une nouvelle méthode de sélection de fréquences est requise afin de réduire le nombre d'interférences nuisibles aux noeuds PR, et maximiser les chances de délivrance des messages aux voisins récepteurs des noeuds CR, et augmenter ainsi la fiabilité des données disséminées. Dans cette thèse nous proposons SURF, une nouvelle méthode distribuée de sélection de fréquences pour la dissémination fiable de données dans un réseau radio cognitif multi-sauts. SURF classifie les fréquences radio disponibles en fonction de l'occupation des fréquences des noeuds à radio primaire et le nombre de noeuds 'a radio cognitive utilisant ces fréquences. Les résultats de simulation obtenus par NS-2 confirment que SURF est une stratégie efficace dans la sélection des meilleures fréquences de diffusion de données, comparée aux autres approches liées. Nous avons aussi constaté que les stratégies de sélection de fréquences sont considérablement influencées par l'activité des noeuds 'a radio primaire. Dans la suite ce cette thèse, nous étudierons et analyserons l'impact des modèles d'activités des noeuds PR sur les différentes stratégies de sélection de fréquences à travers des simulations basées NS-2. Nous avons remarqué que l'activité intermittente de PR est le cas où les solutions intelligentes doivent opérées. C'est dans ce cas où SURF donne les meilleures résultats et la région ciblée se serve des opportunités de communication. Enfin, dans cette thèse, nous allons encore plus loin en vérifiant l'applicabilité et la faisabilité de SURF. Dans cette perspective, d'abord, nous proposons une architecture d'accès à internet basse sur la radio cognitive pour les réseaux partiellement endommagés. Nous discutons les détails architecturaux et le principe de fonctionnement de l'architecture proposée. Nous avons également passé en revue les enjeux et les défis de déploiement de cette nouvelle architecture. Deuxièmement, nous discutons l'applicabilité de SURF dans le contexte de l'agrégation de fréquences et à cet égard, nous discutons une stratégie d'interférence basée sur l'agrégation de fréquences pour les réseaux radios cognitifs.
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Bouallegue, Kaïs. "Contribution à la radio intelligente à forte mobilité : adaptation spectrale et allocation dynamique des ressources." Thesis, Valenciennes, 2017. http://www.theses.fr/2017VALE0023.
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Les objectifs essentiels des opérateurs ferroviaires sont d'augmenter la sécurité, de réduire les coûts d'exploitation et de maintenance, d'accroître l'attrait et le profit en offrant de nouveaux services aux passagers. Ces objectifs seront atteintsgrâce à une énorme augmentation des échanges de flux de données entre les infrastructures existantes et les technologies présentes utilisées au bord du train. L'efficacité spectrale, l'optimisation des ressources radioélectriques ainsi que l'interopérabilité mais aussi la fiabilité des communications sont des éléments majeurs pour les applications ferroviaires. Ces contraintes ainsi que l'utilisation sporadique des bandes fréquentielles à disposition ont donné le jour à la radio intelligente. Cette dernière se présente comme une technologie émergente qui améliore les performances des systèmes radio existants en intégrant l'intelligence artificielle avec la radio logicielle. Un système radio intelligent est défini par sa capacité à être conscient de son environnement radioélectrique. En effet, afin d'optimiser au maximum les opportunités spectrales qui lui sont offerts, le dispositif radio intelligent doit être capable de transmettresur des bandes laissées libres tout en réalisant un sondage spectral afin de ne pas interférer avec les utilisateurs ayant la priorité sur la bande mais aussi pour détecter d'autres fréquences vacantes. Dans le cadre de cette thèse, nous proposons de nous concentrer sur la problématique de détection de spectre dans un environnement à très forte mobilité. Certaines contraintes sont à prendre en compte, telles que la vitesse. À cela s'ajoute les contraintes de réglementation concernant les critères de détection, telles que la norme IEEE 802.22 WRAN qui stipule que la détection d'un utilisateur prioritaire doit être réalisée à -21dB dans un laps de temps de 2 secondes. L'objectif est donc de concevoir un terminal radio intelligent dans les conditions physiques et réglementaires de transmission dans un environnent ferroviaireThe main objectives of railway operators are to increase safety, reduce operating and maintenance costs, increase attractiveness and profit by offering new services to customers. These objectives will be achieved through a huge increase of data fluxes between existing infrastructure and the technologies currently used on the train. Spectral efficiency, optimization of radio resources, interoperability and reliability of communications are major elements for railway applications. These constraints and the sporadic use of available frequency bands have gave rise to cognitive radio. Cognitive radio is an emerging technology that improves the performance of existing radio systems by integrating artificial intelligence with software radio. A cognitive radio system is defined by its ability to be aware of its radio environment. Indeed, to optimize as much as possible the available spectral opportunities, the cognitive radio device must be able to transmit on free bands while performing a spectrum sensing to not interfere with users having priority on the band and to detect other vacant frequencies. As part of this thesis, we propose to focus on the problem of spectrum detection in a highly mobile environment. Some constraints should be considered, such as speed. Added to this, there are regulatory constraints on detection criteria, such as the IEEE 802.22 WRAN standard, which stipulates that detection of a priority user must be performed at -21 dB within a period of 2 seconds. The objective is therefore to design an intelligent radio terminal in the physical and regulatory conditions of transmission in a railway environment
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Abutarboush, Hattan F. "Fixed and reconfigurable multiband antennas." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/9037.
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With the current scenario of development of antennas in the wireless communication field, the need of compact multiband, multifunctional and cost effective antenna is on the rise. The objective of this thesis is to present fixed and reconfigurable techniques and methods for small and slim multiband antennas, which are applicable to serve modern small and slime wireless, mobile and cognitive radio applications. In the fixed designs, independent control of the operating frequencies is investigated to enhance the antennas capabilities and to give the designer an additional level of freedom to design the antenna for other bands easily without altering the shape or the size of the antenna. In addition, for mobile phone antenna, the effect of user’s hand and mobile phone housing are studied to be with minimum effect. Although fixed multiband antennas can widely be used in many different systems or devices, they lack flexibility to accommodate new services compared with reconfigurable antennas. A reconfigurable antenna can be considered as one of the key advances for future wireless communication transceivers. The advantage of using a reconfigurable antenna is to operate in multiband where the total antenna volume can be reused and therefore the overall size can be reduced. Moreover, the future of cell phones and other personal mobile devices require compact multiband antennas and smart antennas with reconfigurable features. Two different types of frequency reconfigurability are investigated in this thesis: switchable and tunable. In the switchable reconfigurability, PIN diodes have been used so the antenna’s operating frequencies can hop between different services whereas varactor diode with variable capacitance allow the antenna’s operating frequencies to be fine-tuned over the operating bands. With this in mind, firstly, a switchable compact and slim antenna with two patch elements is presented for cognitive radio applications where the antenna is capable of operating in wideband and narrow bands depending on the states of the switches. In addition to this, a switchable design is proposed to switch between single, dual and tri bands applications (using a single varactor diode to act as a switch at lower capacitance values) with some fine tuning capabilities for the first and third bands when the capacitance of the diode is further increased. Secondly, the earlier designed fixed antennas are modified to be reconfigurable with fine-tuning so that they can be used for more applications in both wireless and mobile applications with the ability to control the bands simultaneously or independently over a wide range. Both analytical and numerical methods are used to implement a realistic and functional design. Parametric analyses using simulation tools are performed to study critical parameters that may affect the designs. Finally, the simulated designs are fabricated, and measured results are presented that validate the design approaches.
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Musil, Tomáš. "Policy-Based Flexible Spectrum Usage for Next-Generation Mobile Communication Networks." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218764.
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This Master's thesis deals with proposal of Flexible Spectrum Usage (FSU) algorithm based on policy agreed among operators. The introduction presents basic information about properties of next generation mobile communication ITM-Advanced system. After the introductory part the attention is given to the items efficient for FSU implementation as well as parameters used for evaluation of FSU algorithm efficiency. Several variants policy based FSU algorithm utilize value of Signal to Interference plus Noise Ratio (SINR) is designed. The SINR information is used to combat with mutual interference which is caused by coexistence of several operators in the same geographical area sharing over the same spectrum pool. Individual needed as traffic and quality of service requirements of each operator is taken into consideration as well. The main aim is to maximize cell troughput as well as data- rates for each user of HBS. For simulation of proposal algorithm is considered deployment of four Currently Home Base Stations (HBS) in indoor loacal area scenerio with random number of users in given range. Each operator makes independent dicision without signalling exchange among other. The only considered information that HBS can use is gotten by scenning its environment. This problem soliving is considered to use Cognitive Radio (CR)
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Baldo, Nicola. "Cognitive Radios and Networks." Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3425609.
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In recent years, the Cognitive Radio and Cognitive Network paradigms have received significant attention by the research community. Cognitive Radios and Networks, in their initial formulation, are characterized by the addition of cognition capabilities such as reasoning and learning to wireless devices and networks, with the aim of providing enhanced adaptability and reconfigurability to cope with the ever-growing challenges of radio communications.
The concepts of Cognitive Radio and Network have actually been interpreted in several different ways. In this thesis, we will first of all provide an overview of the different interpretations of Cognitive Radios and Networks, as appeared in the recent literature.
We will then focus on the cognitive adaptation and reconfiguration of devices and networks by means of Artificial Intelligence (AI) techniques. In this respect, we will discuss how two well-known AI techniques, i.e., Fuzzy Logic and Neural Networks, can be used within a cross-layer and cross-device knowledge representation and reasoning architecture to become major enabling technologies for Cognitive Radios and Networks. For each technology we will discuss how it can be effectively adopted to implement key functionalities of cognitive systems, and we will present and discuss example applications such as cross-layer parameter optimization, wireless network access selection and channel assignment. For all the discussed applications, we will present performance evaluation results showing the advantages that the proposed techniques provide with respect to state-of-the-art approaches.
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Kataria, Amit. "Cognitive radios spectrum sensing issues /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/5047.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 28, 2008) Includes bibliographical references.
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Sharma, Gaurav. "Adaptive modulation for cognitive radios." Diss., Rolla, Mo. : University of Missouri--Rolla i.e. [Missouri University of Science and Technology], 2008. http://scholarsmine.mst.edu/thesis/pdf/Sharma_09007dcc8046bf0b.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2008.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 13, 2008) Degree granted by Missouri University of Science and Technology, formerly known as University of Missouri--Rolla. Includes bibliographical references (p. 44-45).
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Kaminski, Nicholas James. "Performance Evaluation of Cognitive Radios." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/32092.
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This thesis presents a performance evaluation system for cognitive radio. It considers per-
formance as a complex, multi-dimensional function. Typically such a function would take
some record of actions as an argument; however, a key contribution of this work is the
addition of background information to the domain of the performance function. Including
this information generalizes the performance function across many radios and applications,
with the additional cost of complicating the domain. Thus the presented evaluation system
organizes the domain information into sets. These sets are divided into two categories, one
capturing necessary information that is external to the radio and on capturing necessary
information that internal to the radio. These categories highlight the fact that neither the
true actions nor the true performance is directly observable at the onset of evaluation. This
arises because a cognitive radio can only express its actions in terms of the available knobs
and meters, which together form the radioâ s language. Some understanding of this language
and its limitations is required to fully understand the radioâ s expression of its actions. This
parallelism of actions and performance suggests implementing the evaluation method as a
composite form of the performance function. The composite performance function is made
up of two sub-functions, one of which producing action information and one of which pro-
ducing performance information. Specifically, the first sub-function is used to determine
general measures of the actionsâ influence on performance; these are labeled Measures of Effectiveness. The second sub-function uses these Measures of Effectiveness to determine
application specific performance values, called Measures of Performance. This work covers
both these measures in detail. Each measure is determined as the result of a neural network
based interpolation. This thesis also provides an examination of artificial neural networks
in the scope of performance evaluation. Once these concepts are explored, a walk-through
evaluation is presented. The four phases are the Setup Phase, the Logging Phase, the Train-
ing Phase, and the Evaluation Phase. Each phase is structured to provide the information
necessary to determine the final performance. These phases detail the process of evaluation
and discuss the realization of concepts explored earlier. This work concludes with a compar-
ative evaluation example that proves the worth of the presented approach. A full evaluation
system is outlined by this thesis and the foundational details for the system are explored in detail.Master of Science
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Kaminski, Nicholas James. "Social Intelligence for Cognitive Radios." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25786.
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This dissertation introduces the concept of an artificial society based on the use of an action based social language combined with the behavior-based approach to the construction of multi-agent systems to address the problem of developing decentralized, self-organizing networks that dynamically fit into their environment. In the course of accomplishing this, social language is defined as an efficient method for communicating coordination information among cognitive radios inspired by natural societies. This communication method connects the radios within a network in a way that allows the network to learn in a distributed holistic manner. The behavior-based approach to developing multi-agent systems from the field of robotics provides the framework for developing these learning networks. In this approach several behaviors are used to address the multiple objectives of a cognitive radio society and then combined to achieve emergent properties and behaviors. This work presents a prototype cognitive radio society.
This society is implemented, using low complexity hardware, and evaluated. The work does not focus on the development of optimized techniques, but rather the complementary design of techniques and agents to create dynamic, decentralized self-organizing networksPh. D.
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Guidotti, Alessandro <1983>. "Spectrum Management and Cognitive Radios." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4335/1/GUIDOTTI_ALESSANDRO_TESI.pdf.
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The ever increasing demand for new services from users who want high-quality broadband services while on the move, is straining the efficiency of current spectrum allocation paradigms, leading to an overall feeling of spectrum scarcity. In order to circumvent this problem, two possible solutions are being investigated: (i) implementing new technologies capable of accessing the temporarily/locally unused bands, without interfering with the licensed services, like Cognitive Radios; (ii) release some spectrum bands thanks to new services providing higher spectral efficiency, e.g., DVB-T, and allocate them to new wireless systems. These two approaches are promising, but also pose novel coexistence and interference management challenges to deal with. In particular, the deployment of devices such as Cognitive Radio, characterized by the inherent unplanned, irregular and random locations of the network nodes, require advanced mathematical techniques in order to explicitly model their spatial distribution. In such context, the system performance and optimization are strongly dependent on this spatial configuration. On the other hand, allocating some released spectrum bands to other wireless services poses severe coexistence issues with all the pre-existing services on the same or adjacent spectrum bands.
In this thesis, these methodologies for better spectrum usage are investigated. In particular, using Stochastic Geometry theory, a novel mathematical framework is introduced for cognitive networks, providing a closed-form expression for coverage probability and a single-integral form for average downlink rate and Average Symbol Error Probability. Then, focusing on more regulatory aspects, interference challenges between DVB-T and LTE systems are analysed proposing a versatile methodology for their proper coexistence. Moreover, the studies performed inside the CEPT SE43 working group on the amount of spectrum potentially available to Cognitive Radios and an analysis of the Hidden Node problem are provided. Finally, a study on the extension of cognitive technologies to Hybrid Satellite Terrestrial Systems is proposed.
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Guidotti, Alessandro <1983>. "Spectrum Management and Cognitive Radios." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amsdottorato.unibo.it/4335/.
Full textAbstract:
The ever increasing demand for new services from users who want high-quality broadband services while on the move, is straining the efficiency of current spectrum allocation paradigms, leading to an overall feeling of spectrum scarcity. In order to circumvent this problem, two possible solutions are being investigated: (i) implementing new technologies capable of accessing the temporarily/locally unused bands, without interfering with the licensed services, like Cognitive Radios; (ii) release some spectrum bands thanks to new services providing higher spectral efficiency, e.g., DVB-T, and allocate them to new wireless systems. These two approaches are promising, but also pose novel coexistence and interference management challenges to deal with. In particular, the deployment of devices such as Cognitive Radio, characterized by the inherent unplanned, irregular and random locations of the network nodes, require advanced mathematical techniques in order to explicitly model their spatial distribution. In such context, the system performance and optimization are strongly dependent on this spatial configuration. On the other hand, allocating some released spectrum bands to other wireless services poses severe coexistence issues with all the pre-existing services on the same or adjacent spectrum bands.
In this thesis, these methodologies for better spectrum usage are investigated. In particular, using Stochastic Geometry theory, a novel mathematical framework is introduced for cognitive networks, providing a closed-form expression for coverage probability and a single-integral form for average downlink rate and Average Symbol Error Probability. Then, focusing on more regulatory aspects, interference challenges between DVB-T and LTE systems are analysed proposing a versatile methodology for their proper coexistence. Moreover, the studies performed inside the CEPT SE43 working group on the amount of spectrum potentially available to Cognitive Radios and an analysis of the Hidden Node problem are provided. Finally, a study on the extension of cognitive technologies to Hybrid Satellite Terrestrial Systems is proposed.
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Banerjee, Torsha. "Energy Efficient Data Representation and Aggregation with Event Region Detection in Wireless Sensor Networks." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1196187013.
Full text
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Sun, Xusheng. "Optimal distributed detection and estimation in static and mobile wireless sensor networks." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44825.
Full textAbstract:
This dissertation develops optimal algorithms for distributed detection and estimation
in static and mobile sensor networks. In distributed detection or estimation scenarios
in clustered wireless sensor networks, sensor motes observe their local environment,
make decisions or quantize these observations into local estimates of finite length, and
send/relay them to a Cluster-Head (CH). For event detection tasks that are subject to
both measurement errors and communication errors, we develop an algorithm that
combines a Maximum a Posteriori (MAP) approach for local and global decisions with
low-complexity channel codes and processing algorithms. For event estimation tasks that
are subject to measurement errors, quantization errors and communication errors, we
develop an algorithm that uses dithered quantization and channel compensation to ensure
that each mote's local estimate received by the CH is unbiased and then lets the CH fuse
these estimates into a global one using a Best Linear Unbiased Estimator (BLUE). We then
determine both the minimum energy required for the network to produce an estimate
with a prescribed error variance and show how this energy must be allocated amongst the
motes in the network.
In mobile wireless sensor networks, the mobility model governing each node will affect the
detection accuracy at the CH and the energy consumption to achieve this level of accuracy.
Correlated Random Walks (CRWs) have been proposed as mobility models that
accounts for time dependency, geographical restrictions and nonzero drift. Hence, the
solution to the continuous-time, 1-D, finite state space CRW is provided and its statistical
behavior is studied both analytically and numerically. The impact of the motion of sensor
on the network's performance is also studied.
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Lessinnes, Mathieu. "Resource allocation for cooperative cognitive radios." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209352.
Full textAbstract:
Resource allocation consists in allocating spectrum and power on every link of a network, possibly under power and rate requirements. In the context of cognitive radios, almost 15 years of research produced an impressive amount of theoretical contributions, exploring a wide range of possibilities. However, despite the ever-growing list of imaginable scenarios, we observe in Chapter 2 that most of these studies are based on similar working hypotheses. Our first contribution is to challenge some of these hypotheses, and propose a novel resource allocation scheme. Sticking to realistic assumptions, we show how our scheme reduces both computational complexity and control traffic, compared to other state-of-the-art techniques.Due to a majority of the abovementioned studies making some constraining assumptions, realistic system designs and experimental demonstrations are much more quiet and unharvested fields. In an effort to help this transition from theory to practice, our second contribution is a four-nodes cognitive network demonstrator, presented in Chapter 3. In particular, we aim at providing a modular platform available for further open collaboration: different options for spectrum sensing, resource allocation, synchronisation and others can be experimented on this demonstrator. As an example, we develop a simple protocol to show that our proposed resource allocation scheme is fully implementable, and that primary users can be avoided using our approach.
Chapter 4 aims at removing another working hypothesis made when developping our resource allocation scheme. Indeed, resource alloca- tion is traditionally a Media Access Control (MAC) layer problem. This means that when solving a resource allocation problem in a network, the routing paths are usually assumed to be known. Conversely, the routing problem, which is a network layer issue, usually assumes that the available capacities on each link of the network (which depend on resource allocation) are known. Nevertheless, these two problems are mathematically entangled, and a cross-layer allocation strategy can best decoupled approaches in several ways, as we discuss in Chapter 4. Accordingly, our third and last contribution is to develop such a cross-layer allocation scheme for the scenario proposed in previous chapters.
All conclusions are summarised in Chapter 5, which also points to a few tracks for future research.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Yrjölä, S. (Seppo). "Analysis of technology and business antecedents for spectrum sharing in mobile broadband networks." Doctoral thesis, Oulun yliopisto, 2017. http://urn.fi/urn:isbn:9789526214993.
Full textAbstract:
Abstract Sharing is emerging as one of the megatrends influencing future business opportunities, and wireless communications is no exception to this development. Future mobile broadband networks will operate on different types of spectrum bands including shared spectrum, which calls for changes in the operation and management of the networks. The creation and capture of value by the different players in the mobile broadband ecosystem is expected to change due to regulation, technology, and business landscape related drivers that concern not only spectrum sharing, but also sharing of other resources such as infrastructure, technologies, or data. This thesis examines the key business and technology enablers needed to exploit spectrum sharing in mobile broadband networks, and presents the business model characteristics and strategic choices that spectrum sharing concepts support. Action research and integral scenarios methodologies were applied for strategic and business analysis utilizing the capacity and expertise of the policy, business and technology research communities. The thesis introduces a new approach to analyze the scalability of the spectrum sharing concepts and their business model elements utilizing sharing economy antecedent factors. The results indicate that all analyzed sharing concepts meet basic requirements to scale. The Licensed Shared Access (LSA) leverages existing assets and capabilities of the mobile network operator domain, the Citizens Broadband Radio Service (CBRS) extends the business model dynamics from connectivity to content, context and commerce, and the hybrid usage of Ultra High Frequency (UHF) band by Digital Terrestrial TV (DTT) and downlink Long Term Evolution (LTE) (HUHF) enables new collaborative opportunities between converging communication, Internet and media domains. The thesis validates the feasibility of spectrum sharing between mobile broadband networks and other types of incumbent spectrum users utilizing Finnish cognitive radio field trial environment (CORE), and expands the notion of spectrum sharing beyond the mobile broadband domain to be applied to other wireless systems including the media and broadcasting. The presented results can be used in developing the future mobile broadband systems enhanced with innovative spectrum sharing enabled business models to cope with the growing demand for capacity and new services by humans and machinesTiivistelmä Jakamistalous on yksi suurista tulevaisuuden liiketoimintamahdollisuuksiin vaikuttavista trendeistä, eikä langaton tietoliikenne ole tässä poikkeus. Tulevaisuuden laajakaistaiset matkapuhelinverkot tulevat hyödyntämään erityyppisiä radiotaajuuksia, kuten jaettuja taajuuskaistoja, mikä vaatii muutoksia verkkojen toimintoihin ja hallintaan. Eri toimijoiden arvonluonti- ja ansaintamahdollisuuksien odotetaan muuttuvan näissä liikkuvan laajakaistan ekosysteemeissä regulaation, teknologian ja liiketoimintaympäristön kehittyessä, ei vain taajuuksien jakamisessa, vaan myös kun kyseessä on muiden resurssien kuten infrastruktuurin, teknologioiden tai tiedon jakaminen. Väitöskirja tutkii teknologia- ja liiketoimintaedellytyksiä taajuusjakomenetelmille matkapuhelinverkoissa, sekä esittelee ja analysoi menetelmien mahdollistamia liiketoimintamalleja ja strategisia valintoja. Strategia- ja liiketoiminta-analyyseissä käytettiin toimintatutkimus- ja skenaariomenetelmiä poikkitieteellisissä tutkimusprojekteissa yhteistyössä reguloinnin, liiketoiminnan ja tekniikan tutkimusyhteisöjen kanssa. Tutkimus esittelee uuden lähestymistavan taajuusjakotekniikoiden liiketoimintamallien skaalautuvuuden analysointiin jakamistalouden määritelmiä hyödyntäen. Tulokset osoittavat, että kaikki tutkitut tekniikat täyttävät perusedellytykset skaalautuvuudelle; Licensed Shared Access (LSA) hyödyntäen matkapuhelinoperaattorin olemassa olevia resursseja ja kyvykkyyksiä, Citizens Broadband Radio Service (CBRS) laajentaen liiketoimintamalleja tietoliikenteestä sisältöön, kontekstiin ja kaupankäyntialustoihin, sekä digitaalitelevision ja langattoman LTE-tekniikan hybridikäyttö UHF-taajuuskaistalla (HUHF) mahdollistaen uusia liiketoimintamahdollisuuksia lähentyvien tietoliikenne-, Internet- ja mediaekosysteemien välillä. Väitöskirja tulokset vahvistivat taajuuden jakamisen soveltuvuuden liikkuvan laajakaistaverkon ja saman taajuusalueen eri teollisuudenalan haltijan välillä suomalaisessa CORE kenttätestausympäristössä, ja laajensivat taajuusjakotekniikan sovellettavuutta myös muihin langattomiin järjestelmiin sisältö- ja mediajakelussa. Esitettyjä tuloksia voidaan hyödyntää tulevaisuuden langattomien laajakaistaverkkojen kehitystyössä vastaamaan ihmisten ja koneiden kasvaviin tietoliikennepalveluiden ja -kapasiteetin tarpeisiin hyödyntäen tehokkaita taajuusjakotekniikoita ja niiden mahdollistamia innovatiivisia liiketoimintamalleja
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Kean, Simon Ralph. "Acoustics of hand portable mobile radios." Thesis, University of Canterbury. Department of Mechanical Engineering, 2005. http://hdl.handle.net/10092/2219.
Full textAbstract:
The aim of the project was to investigate the acoustics of hand portable radios identifying key
parameters contributing to their performance and from these findings develop a design guide.
A systems engineering approach was taken with the project focus on internal and external
acoustic and vibration interactions.
The internal interactions investigated were between electrical and mechanical systems while
the external interactions included the influence of the user and environment on the radio
performance. The interactions provided quantitative verification of the Orca's perceived poor
audio performance and enabled a design guide to be developed to prevent the issues from
recurring.
A significant proportion of the work was experimentally based and provides methodology to
aid future analysis of other products. Commercially available software, LMS SYSNOISE, was
utilised to implement a vibro-acoustic finite and boundary element model of the radio. The
results were verified against experimental measurements. It was found that SYSNOISE was
suitable as a design tool for predicting modes and trends but was unsuccessful at predicting
the magnitude of acoustic radiation. The reason for this was attributed to difficulties in
modelling damping.
The design guide contains a design procedure and recommendations for acoustic information
management. To realise the full benefit of acoustic analysis procedures need to be
implemented to incorporate the information into mechanical design, electrical design and also
sales and marketing.
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Kharbech, Sofiane. "Application de la radio intelligente dans le contexte ferroviaire : identification aveugle du type de modulation pour les canaux à grandes vitesses." Thesis, Valenciennes, 2015. http://www.theses.fr/2015VALE0010.
Full textAbstract:
Un système de transport ferroviaire intelligent est essentiellement caractérisé par son niveau d'autonomie de prise de décision en fonction des conditions qui lui sont extérieurs. Afin de renforcer son intelligence et son autonomie, cette nouvelle génération de systèmes de transport intègre des multiples technologies et standards de communication et de traitement de l'information. L'intégration de ces technologies permet aux opérateurs du transport ferroviaire de réduire les coûts d'exploitation et de maintenance et d'attirer un plus grand nombre de passagers en leur facilitant l'accès ainsi que l'exploitation du transport ferroviaire tout en leur offrant des nouveaux services à bord. Cependant l'utilisation de plusieurs standards de communication ainsi que l'augmentation du trafic (le nombre de passagers et le nombre de véhicules mis en service) déclenchent un besoin sans précédent des ressources radio, notamment au niveau du spectre fréquentiel. En effet, avec la demande croissante des ressources radio, la Radio Intelligente (RI) se présente comme une technologie émergente qui améliore les performances des systèmes radio existants en intégrant l'intelligence artificielle avec la radio logicielleAny intelligent railway transport system is mainly characterized by its autonomy in making decisions in terms of its external conditions. In order to improve its cognition and autonomy, this new generation of transport systems integrates multiple technologies and standards of communication and information processing. The integration of these technologies allows rail operators to reduce operational and maintenance costs and attracts more passengers by making easier rail transport access and use while offering new services on board. However, using multiple communication standards and increasing traffic (number of passengers and vehicles in service) trigger an unprecedented need for radio resources, particularly frequency spectrum. Indeed, with the growing of radio resources demand, Cognitive Radio (CR) is an emerging technology that improves the performance of existing radio systems by the integration of artificial intelligence and software defined radio (SDR)
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Jia, Peng. "Spectrum-sensing threshold designs for cognitive radios." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97121.
Full textAbstract:
This thesis presents a study of optimal threshold designs for energy-detection based spectrum sensing in a cognitive-radio network with a pair of Primary-User (PU) transmitter-receiver and a pair of Secondary-User (SU) transmitter-receiver uniformly distributed in their corresponding transmission and interference ranges. Both large-scale path-loss and small-scale fading are considered in the wireless channel model. At first, the optimization problems under three criteria: Risk Minimization, Cost Minimization, and Capacity Maximization are formulated for SU with narrowband sensing capability. Derived under Bayesian framework, Risk Minimization threshold aims to minimize the sum of the miss detection and false alarm probabilities while Cost Minimization threshold considers minimizing the losses in PU and SU link rates due to miss detection and false alarm. On the other hand, Capacity Maximization thresholds are derived to achieve the maximum weighted sum of the PU and SU link rates. The performance of the derived optimal sensing thresholds is investigated and compared in terms of the achieved PU, SU link rates, and the sum capacity of the network for different PU transmission activity factors. Advantages of knowledge of PU and SU locations are also evaluated. Illustrative results show that SU opportunistic capacity can be obtained at the costs of some degradation in the PU link rate. In the narrowband sensing case, the Bayesian-based Risk Minimization and Cost Minimization thresholds are found to be more PU-link protective (i.e., introduce less degradation in PU link rate, especially at high PU transmission activity factor) while Capacity Maximization threshold can achieve the highest sum capacity of the network. The optimal threshold designs for narrowband sensing are further examined to include the constraint on guaranteed minimum degradation in the achieved PU rate. Under this constraint, the advantage in protecting the PU link of the Bayesian-based thresholds is no longer useful, and Capacity Maximization threshold is the better choice as it offers higher SU link rate and sum capacity. Furthermore, the study of optimum sensing thresholds for three criteria and without and with constraint is extended to consider the case of SU with wideband sensing capability along with a spectrum access algorithm, aiming at reducing the miss detection probability. Results show that, compared to the narrowband sensing, for all three criteria, the wideband sensing approach offers much better SU and PU link rates over the whole range of PU transmission activity factor and the resulting sum rate increases monotonically with the number of subcarriers. It is also confirmed that, for wideband sensing, Capacity Maximization threshold again outperforms the Bayesian-based thresholds to meet a much more stringent constraint on guaranteed PU rates while providing better SU link rates and sum rates.Ce mémoire présente une étude de la conception de seuils optimaux pour les méthodes de perception du spectre basées sur le test d'énergie dans un réseau de radio cognitive, dans lequel se trouve une paire émetteur-récepteur pour l'Utilisateur Primaire (PU) et une paire émetteur-récepteur pour l'Utilisateur Secondaire (SU) uniformément distribuées dans leurs plages de transmission et d'interférence respectives. L'affaiblissement de propagation et l'évanouissement à petite échelle sont tous deux considérés dans le modèle du canal sans fil. En premier lieu, les problèmes d'optimisation sont formulés pour le PU avec possibilité de perception du spectre en bande étroite selon trois critères: minimisation du risque, minimisation du coût et maximisation de capacité. Obtenus grâce à un cadre bayésien, le seuil de minimisation du risque cherche à minimiser la somme des probabilités de détection manquée et de fausse alerte tandis que le seuil de minimisation du coût considère les pertes de débit du PU et SU dues à la détection manquée et à la fausse alerte. En revanche, les seuils de maximisation de capacité sont dérivés pour atteindre la somme pondérée maximum de débit du PU et SU. La performance des seuils optimaux dérivés est enquêtée et comparée selon le débit atteint par le PU et SU, ainsi que la somme des débits du réseau pour différents facteurs d'activités de transmission pour le PU. Les avantages apportés par la connaissance de la localisation du SU sont aussi évalués. Les résultats illustratifs démontrent que la capacité opportuniste du SU peut être obtenue au détriment du débit du PU. Dans le cas d'écoute en bande étroite, les seuils bayésiens obtenus avec la minimisation du risque et la minimisation du coût protègent mieux le PU (i.e., introduisent moins de dégradation du débit du PU, en particulier lorsque le facteur d'activité du PU est élevé) tandis que les seuils de maximization de capacité peuvent atteindre la plus haute capacité combinée du réseau. La conception de seuils optimaux pour la perception du spectre en bande étroite est examinée d'avantage pour inclure la contrainte qui garantit la dégradation minimale du débit atteignable du PU. Avec cette contrainte, il n'est plus avantageux de protéger le lien du PU des seuils bayésiens, et le seuil de maximisation de capacité représente un meilleur choix puisqu'il offre un plus haut débit pour le SU ainsi qu'une capacité combinée augmentée. De plus, l'étude des seuils optimaux pour les trois critères, avec et sans contrainte, est étendue pour considérer le cas du SU avec possibilité de perception du spectre en bande large ainsi qu'un algorithme pour accéder au spectre, visant à réduire la probabilité de détection manquée. Les résultats démontrent que, comparée à la perception du spectre en bande étroite, la perception du spectre en bande large offre de meilleurs débits aux SU et PU sur toute la plage de facteurs d'activité du PU et le débit combiné est en augmentation monotonique avec le nombre de sous-porteurs. Il est aussi confirmé que, pour la perception du spectre en bande large, le seuil pour la maximisation de capacité est plus performant que les seuils bayésiens pour permettre une contrainte beaucoup plus stricte sur les débits guarantis au PU tout en fournissant de meilleurs débits au PU et SU.
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Rehman, Ateeq Ur. "Hybrid automatic repeat request assisted cognitive radios." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/419585/.
Full textAbstract:
It is widely known that the Cognitive Radio (CR) paradigm has the potential of improving the exploitation of the earmarked but momentarily unoccupied spectrum, which is exclusively allocated to the primary users (PUs) based on the conventional fixed spectrum allocation policy. The CR systems first have to sense, whether the PU’s band is unoccupied and then dynamically access it. Naturally, CR systems suffer from the same propagation impairments as the traditional wireless communication systems, such as interference, fading and noise, which affect both the reliability and the attainable data rate. In order for the CR system to achieve both reliable data transmission as well as a high throughput and low delay, we propose novel CR-aided Hybrid Automatic Repeat Request (HARQ) protocols, which intrinsically amalgamate the CR functions with HARQ protocols and study their performance. Both perfect and imperfect spectrum sensing are considered. Specifically, we propose the cognitive stop-and-wait-HARQ (CSW-HARQ), cognitive Go-Back-N-HARQ (CGBN-HARQ) as well as the cognitive selective-repeat (CSR-HARQ) schemes and study their throughput and delay both by analysis and simulation. To protect the PUs legal rights, we model their activity of occupying a primary radio (PR) channel as a two-state Markov chain consisting of ‘ON’ and ‘OFF’ states. In order to use the PR channel, the CR system first senses the presence of the PUs and once the PR channel is found to be free (i.e., in the OFF state), the CR system transmits its data packets relying on the principles of SW-HARQ, GBN-HARQ and SR-HARQ. Otherwise, the CR system continues sensing the channel until finding a free one. Naturally, the PR channel may be sensed erroneously, which results either in false alarm or in misdetection. Therefore, the channel may be modelled by a two-state Markov chain, provided that sensing is ideal, or by a four-state Markov chain, if sensing is non-ideal. Here, the four states are determined by the actual state of the PR channel and the state sensed by the CR system. We analyse both the throughput and delay of CR systems relying on different HARQ schemes. We invoke a pair of analytical approaches, namely the probability based approach and the Discrete Time Markov Chain (DTMC) based approach. Closed-form expressions are derived for the throughput, average packet delay and the end-to-end packet delay. Furthermore, for the end-to-end packet delay, we derive both the probability distribution and the average end-to-end packet delay. In the DTMCbased approach, we propose a state generation algorithm for eliminating the illegitimate states, which helps reduce both the dimensionality of the related state transition matrices and the associated computational complexity. All the equations obtained by analysis are validated by numerical simulations. Our performance results reveal that both the achievable throughput and delay of the CSWHARQ, CGBN-HARQ and the CSR-HARQ schemes are substantially affected by the activity of the PUs, by the reliability of the PR channels, by the unreliable sensing decisions and by the number of packets transmitted per time-slot (TS). Specifically, when the probability of the PR channel being busy is high and/or its reliability is relatively low, the throughput attained by these HARQ schemes becomes relatively low and their packet delay increases. Furthermore, for the CGBN-HARQ and CSR-HARQ, our results show that when the propagation environment is time-variant, the number of packets transmitted within a TS should be adapted accordingly, in order to attain the highest throughput and the shortest average transmission delay.
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Tang, Liang. "Performance analyses and design for cognitive radios." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/56288/.
Full textAbstract:
Cognitive radio has been proposed as a promising solution to the conflict between the spectrum scarcity and spectrum under-utilization. As the demand increases for wireless communication services, cognitive radio technology attracts huge attention from both commercial industries and academic researches. The purpose of this thesis is to provide an analytical evaluation of the cognitive radio system performance while taking into consideration of some realistic conditions. Several problems are investigated in this thesis. First, by adopting a dynamic primary user traffic model with one primary user occupancy status change and exponentially distributed channel holding times, its effect on the cognitive radio system performance is evaluated. In the evaluation, the sensing-throughput tradeoff of the cognitive radio is used as the examination criteria, while energy detection is applied during the spectrum sensing. The thesis then takes the investigation further by establishing a primary user multiple changes traffic model which considers multiple primary user occupancy status changes and any reasonable channel holding time distributions. The effect of the primary user multiple changes traffic on the spectrum sensing performance is investigated while the channel holding times are assumed to be exponential, Gamma, Erlang and log-normal distributed. The analytical evaluation of cognitive radio is also carried out from the secondary user transmission perspective, where the performance of the adaptive modulation in cognitive radio system is investigated. The effect of the cognitive radio distinctive features on the performance of both the adaptive continuous rate scheme and the adaptive discrete rate scheme of the adaptive modulation are examined. The BER performance and the link spectral efficiency performance are derived for both schemes. A novel frame structure where the spectrum sensing is performed by using the recovered received secondary frames is also evaluated in this thesis. A realistic scenario which considers the secondary user signal decoding errors is examined for the novel structure, while an ideal upper bound performance is given when the decoding process is assumed perfect. By extending the system to include multiple consecutive secondary frames, the performance of the novel structure is compared to the performance of the traditional frame structure proposed by the IEEE 802.22 WRAN standard. The effect of the primary user multiple changes traffic is also examined for the novel structure. Several major findings are made from the analytical evaluations presented in this thesis. Through numerical examinations, it was shown that, first, the dynamic primary user traffic degrades the performance of cognitive radio systems. Second, the degree of the performance degradation of the cognitive radio systems is related to the number of primary user status changes and the primary user traffic intensity. Different primary user channel holding times distributions also lead to different sensitivities of the system performance to the primary user traffic. Third, cognitive radio distinctive features degrades the performance of the adaptive modulation. When the novel structure is applied for cognitive radio, a higher secondary achievable throughput can be obtained with a limited saturation threshold.
30
Zhao, Youping. "Enabling Cognitive Radios through Radio Environment Maps." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27826.
Full textAbstract:
In recent years, cognitive radios and cognitive wireless networks have been introduced as a new paradigm for enabling much higher spectrum utilization, providing more reliable and personal radio services, reducing harmful interference, and facilitating the interoperability or convergence of different wireless communication networks. Cognitive radios are goal-oriented, autonomously learn from experience and adapt to changing operating conditions. Cognitive radios have the potential to drive the next generation of radio devices and wireless communication system design and to enable a variety of niche applications in demanding environments, such as spectrum-sharing networks, public safety, natural disasters, civil emergencies, and military operations.
This research first introduces an innovative approach to developing cognitive radios based on the Radio Environment Map (REM). The REM can be viewed as an integrated database that provides multi-domain environmental information and prior knowledge for cognitive radios, such as the geographical features, available services and networks, spectral regulations, locations and activities of neighboring radios, policies of the users and/or service providers, and past experience. The REM, serving as a vehicle of network support to cognitive radios, can be exploited by the cognitive engine for most cognitive functionalities, such as situation awareness, reasoning, learning, planning, and decision support. This research examines the role of the REM in cognitive radio development from a network point of view, and focuses on addressing three specific issues about the REM: how to design and populate the REM; how to exploit the REM with the cognitive engine algorithms; and how to evaluate the performance of the cognitive radios. Applications of the REM to wireless local area networks (WLAN) and wireless regional area networks (WRAN) are investigated, especially from the perspectives of interference management and radio resource management, which illustrate the significance of cognitive radios to the evolution of wireless communications and the revolution in spectral regulation. Network architecture for REM-enabled cognitive radios and framework for REM-enabled situation-aware cognitive engine learning algorithms have been proposed and formalized. As an example, the REM, including the data model and basic application programmer interfaces (API) to the cognitive engine, has been developed for cognitive WRAN systems. Furthermore, REM-enabled cognitive cooperative learning (REM-CCL) and REM-enabled case- and knowledge-based learning algorithms (REM-CKL) have been proposed and validated with link-level or network-level simulations and a WRAN base station cognitive engine testbed. Simulation results demonstrate that the WRAN CE can adapt orders of magnitude faster when using the REM-CKL than when using the genetic algorithms and achieve near-optimal global utility by leveraging the REM-CKL and a local search. Simulation results also suggest that exploiting the Global REM information can considerably improve the performance of both primary and secondary users and mitigate the hidden node (or hidden receiver) problem. REM dissemination schemes and the resulting overhead have been investigated and analyzed under various network scenarios. By extending the optimized link state routing protocol, the overhead of REM dissemination in wireless ad hoc networks via multipoint relays can be significantly reduced by orders of magnitude as compared to plain flooding. Performance metrics for various cognitive radio applications are also proposed. REM-based scenario-driven testing (REM-SDT) has been proposed and employed to evaluate the performances of the cognitive engine and cognitive wireless networks. This research shows that REM is a viable, cost-efficient approach to developing cognitive radios and cognitive wireless networks with significant potential in various applications. Future research recommendations are provided in the conclusion.Ph. D.
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Sharma, Guarav. "Game Theory and Adaptive Modulation for Cognitive Radios." International Foundation for Telemetering, 2008. http://hdl.handle.net/10150/606210.
Full textAbstract:
ITC/USA 2008 Conference Proceedings / The Forty-Fourth Annual International Telemetering Conference and Technical Exhibition / October 27-30, 2008 / Town and Country Resort & Convention Center, San Diego, CaliforniaIn a multi-user cognitive radio network, there arises a need for coordination among the network users for efficient utilization of the available electromagnetic spectrum. While adaptive modulation alone helps cognitive radios actively determine the channel quality metric for the next transmission, Game theory combined with an adaptive modulation system helps them achieve mutual coordination among channel users and avoids any possible confusion about transmitting/receiving through a channel in the future. This paper highlights how the concepts of game theory and adaptive modulation can be incorporated in a cognitive radio framework to achieve better communication for telemetry applications.
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Zamat, Hassan. "Practical implementation of sensing receiver in cognitive radios." Diss., Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1346.
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Navalekar, Abhijit C. "Distributed Digital Radios for Land Mobile Radio Applications." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/4.
Full textAbstract:
The main objective of this dissertation is to develop the second generation of Distributed Digital Radio (DDR) technology. A DDR II modem provides an integrated voice/data service platform, higher data rates and better throughput performance as compared to a DDR I modem. In order to improve the physical layer performance of DDR modems an analytical framework is first developed to model the Bit Error Rate (BER) performance of Orthogonal Frequency Division Multiplexing over Frequency Modulation (OFDM/FM) systems. The use of OFDM provides a spectrally efficient method of transmitting data over LMR channels. However, the high Peak-to-Average (PAR) of OFDM signals results in either a low Signal-to-Noise Ratio (SNR) at FM receiver or a high non-linear distortion of baseband signal in the FM transmitter. This dissertation presents an analytical framework to highlight the impact of high PAR of OFDM signal on OFDM/FM systems. A novel technique for reduction of PAR of OFDM called Linear Scaling Technique (LST) is developed. The use of LST mitigates the signal distortion occurring in OFDM over FM systems. Another important factor which affects the throughput of LMR networks is the Push-to-Talk (PTT) delay. A PTT delay refers to the delay between the instant when a PTT switch on a conventional LMR radio is keyed/unkeyed and a response is observed at the radio output. It can be separated into a Receive-To-Transmit Switch Interval (RTSI) or a Transmit-To-Receive Switch Interval (TRSI). This dissertation presents the typical RTSI delay values, distributions and their impact on throughput performance of LMR networks. An analytical model is developed to highlight the asymmetric throughput problem and the unintentional denial of service (UDOS) occurring in heterogeneous LMR networks consisting of radios with different PTT delay profiles. This information will be useful in performance and capacity planning of LMR networks in future.
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Marojevic, Vuk. "Computing resource management in software-defined and cognitive radios." Doctoral thesis, Universitat Politècnica de Catalunya, 2010. http://hdl.handle.net/10803/78033.
Full textAbstract:
Our research aims at contributing to the evolution of modern wireless communications and to the development of software-defined radio (SDR) and cognitive radio, in particular. It promotes a general resource management framework that facilitates the integration of computing and radio resource management. This dissertation discusses the need for computing resource management in software-defined and cognitive radios and introduces an SDR computing resource management framework with cognitive capabilities. The hard real-time computing requirements of software-defined digital signal processing chains (SDR applications), the associated radio propagation and quality of service (QoS) implications, and heterogeneous multiprocessor platforms with limited computing resources (SDR platforms) define the context of these studies.
We examine heterogeneous computing techniques, multiprocessor mapping and scheduling in particular, and elaborate a flexible framework for the dynamic allocation and reallocation of computing resources for wireless communications. The framework should facilitate partial reconfigurations of SDR platforms, dynamic switches between radio access technologies (RATs), and service and QoS level adjustments as a function of the environmental conditions. It, therefore, assumes the facilities of the platform and hardware abstraction layer operating environment (P-HAL-OE).
We suggest a modular framework, distinguishing between the computing system modeling and the computing resource management. Our modeling proposal is based on two computing resource management techniques, which facilitate managing the strict timing constraints of real-time systems. It is scalable and can account for many different hardware architectures and computing resource types. This work focuses on processing and interprocessor bandwidth resources and processing and data flow requirements.
Our computing resource management approach consists of a general-purpose mapping algorithm and a cost function. The independence between the algorithm and the cost function facilitates implementing many different computing resource management policies. We introduce a dynamic programming based algorithm, the tw-mapping, where w controls the decision window. We present a general and parametric cost function, which guides the mapping process under the given resource constraints. An instance of it facilitates finding a mapping that meets all processing and data flow requirements of SDR applications with the available processing and bandwidth resources of SDR platforms. Several SDR reconfiguration scenarios and analyses based on simulations demonstrate the suitability and potentials of our framework for a flexible computing resource management.
We extend our SDR computing resource management concepts to the cognitive radio context. The two primary objectives of cognitive radio are highly reliable communications whenever and wherever needed and the efficient use of the radio spectrum. We formulate a third objective as the efficient use of computing resources. We analyze the cognitive capabilities of our framework─the cognitive radio’s interface to SDR platforms─and indicate the potentials of our cognitive computing resource management proposal.
The cognitive computing resource management needs to be coordinated with the radio resource management. We, therefore, introduce the joint resource management concept for cognitive radios. We present three cognitive cycles and discuss several interrelations between the radio, computing, and application resources, where application resources refer to the available SDR and user applications. Our approach potentiates flexibility and facilitates radio against computing resource tradeoffs. It promotes cognition at all layers of the wireless system for a cooperative or integrated resource management that may increase the performance and efficiency of wireless communications.El objetivo de las investigaciones que se están llevando a cabo dentro del grupo de investigación es contribuir a la evolución de las radiocomunicaciones modernas y, en particular, al desarrollo de los conceptos software radio (SDR) y cognitive radio. El planteamiento general es el de extender la flexibilidad global del sistema de comunicaciones planteando la definición y desarrollo de un entorno en el que pudiesen explorarse las relaciones entre la computación y las prestaciones del sistema de comunicaciones móviles facilitando la integración de los recursos de computación con los recursos radio. Dentro de este marco, la presente tesis plantea la discusión de la necesidad de la gestión de los recursos de computación en entornos SDR y cognitive radio y define un entorno de operación que asume las características especificas del concepto SDR a la vez que incorpora capacidades cognitivas en la gestión de los recursos de computación de las plataformas que den soporte a las nuevas generaciones de sistemas móviles. Los estrictos requerimientos de procesado en tiempo real de las cadenas de procesado digital de la señal definidas por software (aplicaciones SDR), las implicaciones asociadas con la propagación radio y el concepto de calidad de servicio (QoS) y plataformas heterogéneas de múltiples procesadores con recursos de computo limitados (plataformas SDR) definen el contexto de estos estudios. Se examinan técnicas de cómputo de propósito general para definir un entorno de operación que fuese capaz de asignar de forma flexible y dinámica los recursos de cómputo necesarios para facilitar las radiocomunicaciones a los niveles de QoS deseados. Ello debería facilitar los cambios dinámicos de una tecnología de acceso radio a otra, permitiendo el ajuste del tipo de servicio o calidad de servicio en función de las preferencias de los usuarios y las condiciones del entorno. Dicho entorno de operación asume las potencialidades del platform and hardware abstraction layer operating environment (P-HAL-OE). La estructura del entorno de operación se define de forma modular y consiste en un modelado genérico y flexible de las plataformas de computación SDR y en una gestión de recursos de computación abierta y capaz de ajustarse a diferentes objetivos y políticas. En el trabajo se exponen dos técnicas de gestión que pretenden asegurar la consecución estricta de los límites temporales típicos de los sistemas en tiempo real. En cuanto al modelado, este es escalable y capaz de capturar un amplio abanico de arquitecturas hardware y recursos de computación. En el presente trabajo nos centramos en los recursos y requerimientos del procesado y transferencia de datos. Se introduce un algoritmo de mapeo genérico e independiente de la función de coste. La independencia entre el algoritmo y la función de coste facilita la implementación de diferentes políticas de gestión de recursos computacionales. El tw-mapping es un algoritmo basado en dynamic programming, donde w controla la ventana de decisión. Se presenta una función de coste genérica y parametrizable que permite guiar el proceso de gestión de los recursos. Una instancia de ella facilita encontrar una solución al proceso de asignación de recursos que cumpla todos los requerimientos de procesado y trasferencia de datos de las aplicaciones SDR con los recursos disponibles de las plataformas SDR. Diferentes escenarios y varios análisis basados en simulaciones demuestran la adecuación del entorno de trabajo definido y desarrollado, así como sus potencialidades para una gestión flexible de los recursos de cómputo. Se extienden los conceptos mencionados previamente para entornos cognitive radio. Los principales objetivos del concepto cognitive radio son la disponibilidad de comunicaciones altamente robustas en cualquier lugar y momento en que sean necesarias y el uso eficiente del espectro. Como tercer objetivo formulamos el uso eficiente de los recursos de cómputo. Analizamos las capacidades cognitivas de nuestro entorno de operación─la interfaz del sistema cognitive radio a las plataformas SDR─y resaltamos las potencialidades de nuestra propuesta de gestión cognitiva de los recursos computacionales. Dicha gestión cognitiva de los recursos computacionales plantea una integración con la gestión de los recursos radio. Para ello introducimos el concepto de gestión de recursos conjunta para entornos cognitive radio. Se presentan tres ciclos cognitivos y se discuten algunas interrelaciones entre los recursos radio, de cómputo y de aplicación, donde los recursos de aplicación se refieren a las aplicaciones SDR y de usuario disponibles. Nuestra propuesta de gestión de recursos conjunta potencia la flexibilidad y facilita los intercambios entre recursos radio y de computación
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Cabrejos, David. "Implementation of a channel selection algorithm using cognitive radios." Thesis, Wichita State University, 2011. http://hdl.handle.net/10057/3945.
Full textAbstract:
With the increase of wireless devices, the wireless spectrum is becoming overloaded
causing users to experience delays and performance degradation. Typically, a device will start
transmitting data on a frequency and continue transmitting on that frequency regardless of the
channel being overloaded or not. Some smarter devices such as routers are able to sense when
their channel is becoming overloaded by observing delays and amount of devices transmitting on
that frequency. Spectrum analyzers are usually very expensive and usually do not provide many
functionalities other than analysis. Utilizing newer alternatives for sensing the spectrum such as
Software Defined Radios (SDR) can address frequency allocation problems and allow users to
decide the best frequency to use for communication. A promising SDR such as GNU Radio will
be covered in this thesis, as well as the hardware components needed for its functionality. In this
thesis, a cognitive radio approach is taken in designing a channel selection algorithm by scanning
and monitoring the wireless spectrum on IEEE 802.11 b/g through the use of GNU Radio and
USRP. Tests are performed as a proof of concept and to help future research with the use of
cognitive radios.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering.
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Kim, Kyou Woong. "Exploiting Cyclostationarity for Radio Environmental Awareness in Cognitive Radios." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27928.
Full textAbstract:
The tremendous ongoing growth of wireless digital communications has raised spectrum shortage and security issues. In particular, the need for new spectrum is the main obstacle in continuing this growth. Recent studies on radio spectrum usage have shown that pre-allocation of spectrum bands to specific wireless communication applications leads to poor utilization of those allocated bands. Therefore, research into new techniques for efficient spectrum utilization is being aggressively pursued by academia, industry, and government. Such research efforts have given birth to two concepts: Cognitive Radio (CR) and Dynamic Spectrum Access (DSA) network. CR is believed to be the key enabling technology for DSA network implementation. CR based DSA (cDSA) networks utilizes white spectrum for its operational frequency bands. White spectrum is the set of frequency bands which are unoccupied temporarily by the users having first rights to the spectrum (called primary users). The main goal of cDSA networks is to access of white spectrum. For proper access, CR nodes must identify the right cDSA network and the absence of primary users before initiating radio transmission. To solve the cDSA network access problem, methods are proposed to design unique second-order cyclic features using Orthogonal Frequency Division Multiplexing (OFDM) pilots. By generating distinct OFDM pilot patterns and measuring spectral correlation characteristics of the cyclostationary OFDM signal, CR nodes can detect and uniquely identify cDSA networks. For this purpose, the second-order cyclic features of OFDM pilots are investigated analytically and through computer simulation. Based on analysis results, a general formula for estimating the dominant cycle frequencies is developed. This general formula is used extensively in cDSA network identification and OFDM signal detection, as well as pilot pattern estimation. CR spectrum awareness capability can be enhanced when it can classify the modulation type of incoming signals at low and varying signal-to-noise ratio. Signal classification allows CR to select a suitable demodulation process at the receiver and to establish a communication link. For this purpose, a threshold-based technique is proposed which utilizes cycle-frequency domain profile for signal detection and feature extraction. Hidden Markov Models (HMMs) are proposed for the signal classifier.
The spectrum awareness capability of CR can be undermined by spoofing radio nodes. Automatic identification of malicious or malfunctioning radio signal transmitters is a major concern for CR information assurance. To minimize the threat from spoofing radio devices, radio signal fingerprinting using second-order cyclic features is proposed as an approach for Specific Emitter Identification (SEI). The feasibility of this approach is demonstrated through the identification of IEEE 802.11a/g OFDM signals from different Wireless Local Area Network (WLAN) card manufactures using HMMs.Ph. D.
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Ramkumar, Barathram. "Automatic Modulation Classication and Blind Equalization for Cognitive Radios." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28666.
Full textAbstract:
Cognitive Radio (CR) is an emerging wireless communications technology that addresses the inefficiency of current radio spectrum usage. CR also supports the evolution of existing wireless applications and the development of new civilian and military applications. In military and public safety applications, there is no information available about the signal present in a frequency band and hence there is a need for a CR receiver to identify the modulation format employed in the signal.
The automatic modulation classifier (AMC) is an important signal processing component that helps the CR in identifying the modulation format employed in the detected signal.
AMC algorithms developed so far can classify only signals from a single user present in a frequency band. In a typical CR scenario, there is a possibility that more than one user is present in a frequency band and hence it is necessary to develop an AMC that can classify signals from multiple users simultaneously. One of the main objectives of this dissertation is to develop robust multiuser AMC's for CR. It will be shown later that multiple antennas are required at the receiver for classifying multiple signals. The use of multiple antennas at the transmitter and receiver is known as a Multi Input Multi Output (MIMO) communication system. By using multiple antennas at the receiver, apart from classifying signals from multiple users, the CR can harness the advantages offered by classical MIMO communication techniques like higher data rate, reliability, and an extended coverage area. While MIMO CR will provide numerous benefits, there are some significant challenges in applying conventional MIMO theory to CR. In this dissertation, open problems in applying classical MIMO techniques to a CR scenario are addressed.
A blind equalizer is another important signal processing component that a CR must possess since there are no training or pilot signals available in many applications. In a typical wireless communication environment the transmitted signals are subjected to noise and multipath fading. Multipath fading not only affects the performance of symbol detection by causing inter symbol interference (ISI) but also affects the performance of the AMC. The equalizer is a signal processing component that removes ISI from the received signal, thus improving the symbol detection performance. In a conventional wireless communication system, training or pilot sequences are usually available for designing the equalizer. When a training sequence is available, equalizer parameters are adapted by minimizing the well known cost function called mean square error (MSE). When a training sequence is not available, blind equalization algorithms adapt the parameters of the blind equalizer by minimizing cost functions that exploit the higher order statistics of the received signal. These cost functions are non convex and hence the blind equalizer has the potential to converge to a local minimum. Convergence to a local minimum not only affects symbol detection performance but also affects the performance of the AMC. Robust blind equalizers can be designed if the performance of the AMC is also considered while adapting equalizer parameters. In this dissertation we also develop Single Input Single Output (SISO) and MIMO blind equalizers where the performance of the AMC is also considered while adapting the equalizer parameters.Ph. D.
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Fayez, Almohanad Samir. "Design Space Decomposition for Cognitive and Software Defined Radios." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23180.
Full textAbstract:
Software Defined Radios (SDRs) lend themselves to flexibility and extensibility because theydepend on software to implement radio functionality. Cognitive Engines (CEs) introduce
intelligence to radio by monitoring radio performance through a set of meters and configuring
the underlying radio design by modifying its knobs. In Cognitive Radio (CR) applications,
CEs intelligently monitor radio performance and reconfigure them to meet it application
and RF channel needs. While the issue of introducing computational knobs and meters
is mentioned in literature, there has been little work on the practical issues involved in
introducing such computational radio controls.
This dissertation decomposes the radio definition to reactive models for the CE domain
and real-time, or dataflow models, for the SDR domain. By allowing such design space
decomposition, CEs are able to define implementation independent radio graphs and rely on
a model transformation layer to transform reactive radio models to real-time radio models
for implementation. The definition of knobs and meters in the CE domain is based on
properties of the dataflow models used in implementing SDRs. A framework for developing
this work is presented, and proof of concept radio applications are discussed to demonstrate
how CEs can gain insight into computational aspects of their radio implementation during
their reconfiguration decision process.
Ph. D.
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Sethi, Amita. "Potential denial of service threat assessment for cognitive radios." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453572.
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NAWAZ, TASSADAQ. "Wideband cyclostationary spectrum sensing and characterization for cognitive radios." Doctoral thesis, Università degli studi di Genova, 2018. http://hdl.handle.net/11567/930815.
Full textAbstract:
Motivated by the spectrum scarcity problem, Cognitive Radios (CRs) have been proposed as a solution to opportunistically communicate over unused spectrum licensed to Primary users (PUs). In this context, the unlicensed Secondary users (SUs) sense the spectrum to detect the presence or absence of PUs, and use the unoccupied bands without causing interference to PUs. CRs are equipped with capabilities such as, learning, adaptability, and recongurability, and are spectrum aware. Spectrum awareness comes from spectrum sensing, and it can be performed using different techniques.
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Deshpande, Amol Anant. "Policy Reasoning for Spectrum Agile Radios." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/32396.
Full textAbstract:
DARPAâ s neXt Generation (XG) communication program proposes the use of Dynamic Spectrum
Access (DSA) wherein intelligent radios can realize opportunistic usage of frequency
bands by identifying the under-utilized spectrum and reasoning about it. Implementing such
a flexible scheme requires changes in the current static spectrum management approach. As
a result, declarative spectrum management through policy-based dynamic spectrum access
has garnered significant attention recently.
Policy-based dynamic spectrum access decouples the Spectrum Access Policies and Policy
Processing Components from the Radio Platform. The Policies define conditions under which
the radios are allowed to transmit in terms of frequencies used, geographic locations, time etc.
The Policy Processing Components include a reasoning engine called the Policy Reasoner,
which is responsible for enforcing these policies.
This thesis describes the design and implementation of a novel policy reasoner called Bi-
nary Decision Diagram based Reasoner for processing Spectrum Access Policies (BRESAP).
BRESAP processes spectrum policies efficiently by reframing the policy reasoning problem
as a graph based Boolean function manipulation problem. BRESAP uses Binary Decision
Diagrams (BDDs) to represent, analyze and process the policies. It uses a set of efficient
graph-theoretic algorithms to merge these policies into a single meta-policy and compute
opportunity constraints.
Our policy reasoner has the capability to respond to invalid and under-specified transmission
requests sent by the System Strategy Reasoner (SSR). In case of invalid or under-specified
transmission requests, BRESAP returns a set of opportunity constraints which inform the
SSR of the changes needed to the transmission parameters in order to make them conform
to the policies. We also propose three algorithms for computing the opportunity constraints.
The complexity of the first algorithm is proportional to the number of variables in the metapolicy
BDD, while the complexities of the second and third algorithms are proportional to
sum of number of variables and the size (i.e., number of nodes) of the meta-policy BDD.Master of Science
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Bouallegue, Seifeddine. "Mobility and Security Management in Femtocell Networks." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066084/document.
Full textAbstract:
Les réseaux de télécommunications sont soumis à des processus d'amélioration et d'optimisation continue. Chaque nouvelle itération apporte son lot de défis et limites. En effet, la croissance exponentielle des appareils de télécommunication, des stations de base aux équipements utilisateurs conduisent à de sérieux problèmes d'economie d'énergie. En plus des menaces à la vie privée, en particulier pour les réseaux sans fil car les canaux utilisés par les opérateurs peuvent également être utilisés par une oreille indiscrète quelconque. L'optimisation de l'utilisation du spectre est également un défi en raison du fait que le spectre disponible dans les systèmes de communication sans fil est devenu une ressource très rare en raison de la demande croissante. Les réseaux émergents, tels que les femtocells, souffrent également des défis mentionnés précédemment. Le travail de thèse actuel se concentre sur la proposition de solutions aux défis cités précédemment: l'efficacité énergétique, le partage du spectre et la sécurité. Le travail de recherche présenté dans cette thèse a porté sur trois axes principaux: Premièrement, trouver un moyen de réduire au minimum la consommation d'énergie des femtocellules dans les reseaux BWA femto/macro-cellulaire en diminuant le nombre d'événements de mobilité non désirées et l'introduction de nouveaux états de puissance pour la femtocellule. En second lieu, proposer une solution qui vise à réduire le temps de transmission prévu dans le temps de séjour de l'utilisateur secondaire (SU) dans la couverture d'une femtocellule en utilisant un algorithme basé sur le temps minimum prévu de transmission dans le temps de séjour de l'équipement utilisateur (UE). Enfin, introduire un nouveau modèle qui basé sur la sélection du meilleur relais qui maximise le taux de confidentialité et les avantages de l'augmentation du nombre de relais sous la contrainte de qualité de service à la destinationTelecommunications networks are subject to continuous improvement and enhancement processes. Every new iteration brings its set of challenges and limitations. In fact, the exponential growth in telecommunication devices, from base stations to user equipments lead to serious energy efficiency issues. Along with the privacy threats, especially for wireless networks as the channels used by operators can also be used by any eavesdropper. Spectrum usage optimization is also a challenge due to the fact that the available spectrum in wireless communications systems has been a very rare resource because of the increasing demand. Emerging networks, such as femtocells, suffer also from the previously mentioned challenges. The current thesis work focuses on proposing several solutions to the previously cited challenges: energy efficiency, spectrum sharing and security. The research work introduced in this thesis has focused on three main axes: First, find a way to minimize the energy consumption of femtocells in macro/femto-cellular BWA networks by decreasing the number of unwanted mobility events and introducing new power states for the femtocell device. Second, propose a solution that aims to reduce the expected transmission time within the dwell time of Secondary User (SU) in the coverage of a femtocell using an algorithm based on the minimum expected transmission time within the dwell time of the User Equipment (UE) in the coverage of the femtocell. Finally, introduce a new scheme that is based on best relay selection method that maximizes the secrecy rate and benefits from increasing the number of relays under QoS constraint at the destination
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Renard, Julien. "Spectrum Sensing for Cognitive Radios: Improving Robustness to Impulsive Noise." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58285.
Full textAbstract:
Many different types of promising spectrum sensing algorithms for Cognitive Radio (CR) have already been developed. However, many of these algorithms lack robustness with respect to signal statistical parameters uncertainties, such as the noise variance or the shape of its distribution (often assumed to be simply Gaussian). In conjunction with the low Signal-to-Noise Ratio (SNR) requirements, this lack of robustness can often render interesting sensing algorithms impractical for real-life applications. In this thesis, we primarily focus on the impact of heavy-tail noise distributions on different CR detectors and the use of signal limiters (mostly the spatial sign function) to improve their robustness to such noise distributions. Introducing a non-linear transformation of the received signal prior to its processing by the detector fundamentally changes the signal distribution which in turn modifies the distribution of the detector statistic. In order to parametrize the detector and study its performance, it is then necessary to know the shape of the modified distribution. Three types of detectors are investigated: a generic second-order cyclic-feature detector, a Scaled-Largest Eigenvalue (SLE) detector studied in the context of stationary time-series and a new Sequential Likelihood Ratio Test (SLRT) detector. The analysis conducted for each detector revolves around the influence of its parameters, the distribution of the detector statistic and several comparisons with similar detectors for various detection scenarios. Our results indicate that at the cost of a moderate performance loss in a Gaussian noise environment, all the detectors fitted with a signal limiter become robust to impulsive noise and noise parameters uncertainties. We provide analytical approximations for the detectors
statistical distribution that allow us to use the detectors in such configurations as well as to study their performance for different signal limiters and noise distributions.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Hanif, Muhammad Fainan. "Aspects of Design and Analysis of Cognitive Radios and Networks." Thesis, University of Canterbury. Department of Electrical and Computer Engineering, 2010. http://hdl.handle.net/10092/5072.
Full textAbstract:
Recent survey campaigns have shown a tremendous under utilization of the bandwidth allocated to various wireless services. Motivated by this and the ever increasing demand for wireless applications, the concept of cognitive radio (CR) systems has rendered hope to end the so called spectrum scarcity. This thesis presents various different facets related to the design and analysis of CR systems in a unified way. We begin the thesis by presenting an information theoretic study of cognitive systems working in the so called low interference regime of the overlay mode. We show that as long as the coverage area of a CR is less than that of a primary user (PU) device, the probability of the cognitive terminal inflicting small interference at
the PU is overwhelmingly high. We have also analyzed the effect of a key parameter governing the amount of power allocated to relaying the PU message in the overlay mode of operation in realistic environments by presenting a simple and accurate approximation. Then, we explore the possibilities of statistical modeling of the cumulative
interference due to multiple interfering CRs. We show that although it is possible to obtain a closed form expression for such an interference due a single CR, the problem is particularly difficult when it comes to the total CR interference in lognormally faded environments. In particular, we have demonstrated that fitting a
two or three parameter lognormal is not a feasible option for all scenarios. We also explore the second-order characteristics of the cumulative interference by evaluating
its level crossing rate (LCR) and average exceedance duration (AED) in Rayleigh and Rician channel conditions. We show that the LCRs in both these cases can be evaluated by modeling the interference process with gamma and noncentral χ2 processes, respectively. By exploiting radio environment map (REM) information, we have presented two CR scheduling schemes and compared their performance with the naive primary exclusion zone (PEZ) technique. The results demonstrate the significance of using an intelligent allocation method to reap the benefits of the tremendous information available to exploit in the REM based methods. At this juncture, we divert our attention to multiple-input multiple-output (MIMO) CR systems operating in the underlay mode. Using an antenna selection philosophy, we solve a convex optimization problem accomplishing the task and show via analysis and simulations that antenna selection can be a viable option for CRs operating in relatively sparse PU environments. Finally, we study the impact of imperfect
channel state information (CSI) on the downlink of an underlay multiple antenna CR network designed to achieve signal-to-interference-plus-noise ratio (SINR) fairness
among the CR terminals. By employing a newly developed convex iteration technique, we solve the relevant optimization problem exactly without performing any relaxation on the variables involved.
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Soubachov, Boyan Ventzislavov. "Pilot patterns and power loading in NC-OFDM cognitive radios." Doctoral thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/5099.
Full textAbstract:
Includes abstract.Includes bibliographical references.
The implementation of cognitive radios is widely proposed through the use of Orthogonal Frequency Division Multiplexing (OFDM) modulation. In the special case of cognitive radios however, the OFDM modulation scheme cannot simply be implemented without modification due to the huge change in the basic laws of the transmission paradigm. The main reason behind this is that the modulation scheme can no longer assume the contiguousness of its band as well as the interference that may be caused by the cognitive radio users operating in such close proximity to the licensed users. The research presented in this thesis namely identified two areas of cognitive radio which addressed these issues. These were the power loading and channel estimation areas.
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Baban, Shaswar Tharwat Mohammed. "Context-aware cognitive radios learning from data using machine learning techniques." Thesis, King's College London (University of London), 2016. https://kclpure.kcl.ac.uk/portal/en/theses/contextaware-cognitive-radios-learning-from-data-using-machine-learning-techniques(674aef35-8640-41d2-97b2-922182f096cc).html.
Full textAbstract:
Wired or wireless, connectivity has been a vital commodity of life and more so recently in the realm of information age. Those who have access to faster, more reliable and more ubiquitous connectivity—put simply, those who are “better connected”—will have significant advantages in commerce, research and a host of other arenas. In regards to wireless communications, due to the explosion in demand for higher capacity networks, availability of free spectrum resources have become increasingly scarce. The UHF spectrum band in particular, due to its excellent electromagnetic properties, has been reported as inefficiently used and congested by many spectrum regulators of the world. This spectrum resource scarcity issue combined with the ongoing research and development for more intelligent, autonomous and self-aware radio communication led to a vast amount of research on the concept of Cognitive Radio. This thesis researches the learning unit of cognitive radios. The learning unit is responsible for processing information and autonomous decision making. In particular, the research is focused on the extraction and usage of contextual information from the radio environment (e.g. Radio Access Technology type, channel access pattern learning/recognition) and how such information could be exploited to improve the performance of the cognitive radio. The key metrics discussed will be based on information extraction under noise, channel blocking and interference reduction to primary users. We present a set of novel works involving Machine Learning, which is a branch of Artificial Intelligence. New implementation and use cases of state-of-the-art machine learning algorithms are presented that learn from real-life data. In a testbed setup we program software defined radios to recognize different Radio Access Technologies and their channel access patterns. The main technique used in the majority of the thesis is Artificial Neural Networks, concretely: Multi-Layer Perceptron Neural Nets, Self-Organizing Neural Nets, and Deep Auto-Encoders. In some of the works these neural network architectures have been combined in a novel way with Support Vector Machines, and Reinforcement Learning algorithms for channel classification and access. In this thesis we show that it is possible to achieve 95% correct classification at -25 dB among three different radio access technologies, namely, DVB-T, WCDMA and IEEE 802.11a, where, consequently, we can reason over the outcome of this classification to differentiate between primary and secondary transmissions. We also show that, through the use of the proposed autoencoder approximate Q-learning technique, such context-aware cognitive radio can achieve better key performance metrics in dynamic spectrum access as compared to previously researched Q-learning algorithms.
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Trigui, Emna. "Gestion multi-agents du spectre pour des terminaux mobiles à radio cognitive." Thesis, Troyes, 2013. http://www.theses.fr/2013TROY0026/document.
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Cette thèse s’intéresse aux concepts de mobilité et de gestion du spectre dans les réseaux à radio cognitive. Ainsi, nous avons proposé deux approches décentralisées basées sur les systèmes multi-agents (SMA). Nous avons, tout d’abord, intégré des agents au sein des utilisateurs secondaires (n’ayant pas de licence pour l’accès au spectre) et des utilisateurs primaires (disposant d’une licence) et nous avons défini leurs comportements au moment du handover. Notre première solution NESAM propose un mécanisme de négociation entre les agents permettant aux utilisateurs secondaires de se voir allouer une bande de spectre avec un bon rapport prix par durée d’allocation. Nous avons, par ailleurs, proposé une deuxième solution LASMA qui se base sur l’enchère combinée avec de l’apprentissage pour assurer une gestion efficace du spectre ainsi qu’une gestion de la mobilité des utilisateurs à radio cognitive. Nos algorithmes prennent en compte les préférences des utilisateurs, comme la fréquence spectrale, le prix et la durée ainsi que les contraintes de l’environnement spectral telles que les bandes de fréquences disponibles. Nos propositions assurent une exploitation importante des ressources spectrales tout en diminuant le nombre de handovers spectraux. De plus, nos algorithmes offrent un handover spectral transparent et sans interruption lors des déplacements des utilisateurs. Nous avons prouvé également que nos solutions permettent de satisfaire les besoins des utilisateurs et d’améliorer leur utilitéIn this thesis, we are interested in mobile cognitive radio networks while ensuring an efficient spectrum sharing and seamless handover at the same time. Hence, we propose two decentralized approaches based on multi-agents systems. We first deployed agents on each primary (licensed) and secondary (unlicensed cognitive radio) users, respectively. Besides, we define agents’ behaviors during the handover process.Our proposal NESAM defines a novel negotiation mechanism between agents to allow secondary users assigning the appropriate spectrum band giving a good price for the use duration. We have also proposed a second solution LASMA using the learning based auctions. Our algorithms take into account users’ requirements such as spectrum frequency, price and duration as well as environment’s constraints such as available resources.Our proposals improve the overall spectrum utilization and minimize the number of spectrum handovers when users move from one network to another one. This proves that our algorithms ensure efficient spectrum allocation and enable seamless handover during user’s mobility. Besides, we proved that our approaches guarantee users’ satisfaction and improve their utility
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CANAVITSAS, ANGELO ANTONIO CALDEIRA. "PREDICTION OF WHITE SPACES FOR COGNITIVE RADIOS: METHODOLOGY, ALGORITHMS, SIMULATION AND PERFORMANCE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=27066@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROA tecnologia de rádio cognitivo está em pleno desenvolvimento na academia e indústria, sendo apresentada como uma solução para o reduzir o congestionamento do espectro radioelétrico. Dessa forma, diversos estudos têm sido desenvolvidos para obter novas técnicas de compartilhamento do espectro entre usuários ditos primários e secundários. Estas técnicas devem ser robustas o suficiente para minimizar as colisões de ocupação do espectro entre os usuários supracitados, quando o acesso dinâmico ao espectro for aplicado. O presente estudo investigou as soluções de ocupação compartilhada do espectro, em especial nos para serviços de voz na faixa de 450 MHz. A modelagem de ocupação dos canais, a partir de medidas de transmissões reais, permitiu o desenvolvimento de algoritmo robusto que realiza a predição de espaços espectrais (white spaces) dentro de canais destinados a usuários primários. Esse método proposto define, estatisticamente, uma janela de intervalos de tempo futuros que pode ser utilizada por usuários secundários, por apresentar maior probabilidade de possuir espaços espectrais livres, minimizando as possíveis colisões. O emprego do método proposto aumenta a vazão de informações de modo seguro e,com alto desempenho, otimizando,assim,a utilização do espectro radioelétrico.
The cognitive radio technology is being developedin universities and industry as a solution to the radio spectrum scarcity. This technology willallow spectrum sharing between primary and secondary telecommunication users. The techniques employed must be robust enough to minimize spectrum occupancy collisions, when the dynamic spectrum access is applied. This study investigates the trends of spectrum usersoccupation, particularly in voice services in the 450 MHz frequency band.An users occupancy model was developed taking into accountmeasured data of real transmissions. It allowed the development of a robust algorithm that predicts spectral vacancy in channels allocated to primary users. The method selects, statistically, a group of future time intervals that can be used by secondary users, due to a higher probability of having a free spectral space. The use of this new technique minimizes possible collisions, increasing the flow of information in secure way and optimizing the radio spectrum use.
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Stegman, Jason Karl. "Wideband and Narrowband Spectrum Sensing Methods Using Software Defined Radios." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1469.
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The ability to accurately sense the surrounding wireless spectrum, without having any prior information about the type of signals present, is an important aspect for dynamic spectrum access and cognitive radio. Energy detection is one viable method, however its performance is limited at low SNR and must adhere to Nyquist sampling theorem. Compressive sensing has emerged as a potential method to recover wideband signals using sub-Nyquist sampling rates, under the presumption that the signals are sparse in a certain domain. In this study, the performance and some of the practical limitations of energy detection and compressive sensing are compared via simulation, and also implementation using the Universal Software Radio Peripheral (USRP) software defined radio (SDR) platform. The usefulness and simplicity of the USRP and GNU Radio software toolkit for simulation and experimentation, as well as some other application areas of compressive sensing and SDR, is also discussed.
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Artero, Gallardo Guillaume. "Qualité de service dans des environnements réseaux mobiles, contraints et hétérogènes." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/13826/1/artero_gallardo.pdf.
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Les télécommunications sans fil ont connu ces dernières années un immense succès à tel point que le spectre des fréquences est désormais surchargé et nécessite la disponibilité de nouvelles ressources. Pour répondre à ce besoin, des techniques de réutilisation dynamique du spectre ont alors vu le jour sous la dénomination de radio cognitive. Elles consistent à partager de manière opportuniste et efficace certaines fréquences ayant été initialement allouées à d'autres systèmes. Cette thèse se place dans le contexte de réseaux sans fil tactiques hétérogènes comportant des segments de radios cognitives. La difficulté provient alors de la garantie de qualité de service de bout en bout : respect du débit négocié, du délai et de la gigue. Nous nous sommes tout d'abord intéressés au contrôle d'admission dans ce type de réseaux en proposant une méthode de calcul de bande passante résiduelle de bout en bout s'appuyant sur un algorithme de complexité polynomiale et pouvant être implanté de manière distribuée. Nous nous sommes ensuite concentrés sur le routage en proposant une nouvelle métrique tenant compte des particularités de ce type de réseaux. Enfin, nous nous focalisons sur la thématique du routage à contraintes multiples en étudiant et implantant en environnement réel des algorithmes d'approximation proposés dans la littérature.