CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Nesta dissertaÃÃo, nosso principal objetivo foi desenvolver uma tÃcnica de resoluÃÃo para um problema na Ãrea de telecomunicaÃÃes. O problema em questÃo à chamado de problema de PonderaÃÃo de Rodadas (PR) e foi inicialmente proposto em [Klasing,Morales,Perennes, 2008]. O contexto do problema envolve uma rede sem fio, onde as comunicaÃÃes sÃo realizadas via ondas de rÃdio e a rede funciona atravÃs de uma operaÃÃo da rede que satisfaz certas restriÃÃes. Inicialmente, explicamos como à formada uma rede de rÃdio e descrevemos a forma de operaÃÃo da rede de rÃdio junto Ãs restriÃÃes usando um modelo matemÃtico. Em seguida, formalizamos o problema PR como um problema de otimizaÃÃo, especificando suas restriÃÃes, correspondente à geraÃÃo do conjunto de possÃveis operaÃÃes da rede, e critÃrio de otimizaÃÃo, referente ao uso dos recursos da rede. Posteriormente, mostramos um estudo preliminar do problema de ColoraÃÃo FracionÃria (CF) e apresentamos uma tÃcnica de resoluÃÃo deste problema atravÃs do uso de uma heurÃstica lagrangeana baseada em uma relaxaÃÃo lagrangeana de uma formulaÃÃo de programaÃÃo inteira do problema. Essa tÃcnica de resoluÃÃo à entÃo adaptada para o problema PR, consistindo na principal contribuiÃÃo de nossa pesquisa. Por fim, mostramos os resultados computacionais e anÃlises das nossas implementaÃÃes para os problemas CF e PR. / In this dissertation, our main objective was to develop a technique for resolution to a problem in the area of telecommunications. The problem in question is called Round Weighting Problem (RWP) and was originally proposed in (KLASING; MORALES; PeRENNES, 2008). The context of the problem involves a wireless network where communications are performed by radio waves and the network operates through a network operation that satises the constraints of the problem. Initially, we explain how a radio network is formed and describe the mode of operation of the radio network with restrictions using a mathematical model. Then, we formalize the RWP as an optimization problem, specifying their restrictions, corresponding to the generation of the set of possible network operations, and optimization criterion, regarding the use of network resources. Subsequently, we show a preliminary study of the Fractional Coloring problem (FC problem) and present a technique to solve this problem through the use of a lagrangian heuristic based on a lagrangian relaxation of an integer programming formulation of the problem. This resolution technique is then adapted to the RWP, consisting in the main contribution of our research. Finally, we show the computational results and analyzes of our implementations for the Fractional Coloring problem and RWP.

Cognitive Radio technologies have been touted to be instrumental in solving resource-allocation problems in resource-constrained radio environments. The adaptive computational intelligence of these radios facilitates the dynamic allocation of network resources--particularly, the spectrum, a scarce physical asset. In addition to consumer-driven innovation that is governing the wireless communication ecosystem, its associated infrastructure is being increasingly viewed by governments around the world as critical national security interests--the US Military instituted the DARPA Spectrum Collaboration Challenge which requires competitors to design intelligent radios that leverage optimization, A.I., and game-theoretic strategies in order to efficiently access the RF spectrum in an environment wherein every other competitor is vying for the same limited resources. In this work, we detail the design of our radio, i.e., the design choices made in each layer of the network protocol stack, strategies rigorously derived from convex optimization, the collaboration API, and heuristics tailor-made to tackle the unique scenarios emulated in this DARPA Grand Challenge. We present performance evaluations of key components of our radio in a variety of military and disaster-relief deployment scenarios that mimic similar real-world situations. Furthermore, specifically focusing on channel access in the MAC, we formulate the spectrum sensing and access problem as a POMDP; derive an optimal policy using approximate value iteration methods; prove that our strategy outperforms the state-of-the-art, and facilitates means to control the trade-off between secondary network throughput and incumbent interference; and evaluate this policy on an ad-hoc distributed wireless platform constituting ESP32 radios, in order to study its implementation feasibility.

Thesis (M.Sc.) -- University of Limpopo, 2021 / Cognitive Radio (CR) is a promising technology designed to solve many issues, especially spectrum underutilisation and scarcity. The requirement for spectrum effectiveness was essential, and consequently, the possibility of CR arrived along and introduced the unlicensed Secondary Users (SU). SU can operate on the unlicensed and licensed spectrum bands on a condition that they avoid interference with the licensed Primary Users (PU). This approach is called the Dynamic Spectrum Allocation (DSA) and has solved the underutilisation of spectrum using the spectrum holes. The United States of America’s telecommunication regulator Federal Communication Commission (FCC) introduces spectrum bands by unlicensed users looking at the rapid growth of wireless applications and devices; therefore, the Fixed Spectrum Allocation (FSA) become inadequate because of the spectrum crowded issues. Accomplishing this design requirement while meeting the Quality of Service (QoS) of SU is a challenge; thus, the cross-layer design (CLD) was introduced to enhance the efficiency and effectiveness of Cognitive Network (CN). CLD arrangements in Cognitive Radio Network (CRN) are empowering; however, there are yet numerous issues and difficulties that must be addressed, such as resource allocation and others that may negatively impact network performance. Routing in CRN also necessitates the cross-layering approach. Therefore, in this work, designing a protocol that will solve routing issues and channel selection will also maximise spectrum opportunistically. In this study, we propose the Optimised Cognitive Cross-layer Multipath Probabilistic Routing (OCCMPR) protocol, which is the optimised version of Cognitive Cross-layer Multipath Probabilistic Routing (CCMPR). We used MATLAB simulation installed in the Windows 10 operating system (OS) tool to generate comparison results. We compared the OCCMPR protocol with the existing protocols, the Cognitive Ad-hoc On-demand Distance Vector (CAODV) and the CCMPR protocols. / Council for Scientific and Industrial Research (CSIR)

Thesis ( M.Sc. (Computer Science)) -- University of Limpopo, 2019 / Cognitive radio network, which enables dynamic spectrum access, addresses the shortage of radio spectrum caused by ever-increasing wireless technology. This allows efficient utilisation of underutilised licenced spectrum by allowing cognitive radios to opportunistically make use of available licenced spectrum. Cognitive radios (CR), also known as secondary users, must constantly sense the spectrum band to avoid interfering with the transmission of the licenced users, known as primary users. Cognitive radios must cooperate in sensing the spectrum environment to avoid environmental issues that can affect the spectrum sensing. However, cooperative spectrum sensing is vulnerable to Byzantine attacks where selfish CR falsify the spectrum reports. Hence, there is a need to design and implement a defence mechanism that will thwart the Byzantine attacks and guarantee correct available spectrum access decisions. The use of extreme studentized deviate (ESD) test together with consensus algorithms are proposed in this study to combat the results of the availability of Byzantine attack in a cognitive radio network. The ESD test was used to detect and isolate falsified reports from selfish cognitive radios during the information sharing phase. The consensus algorithm was used to combine sensing reports at each time k to arrive at a consensus value which will be used to decide the spectrum availability. The proposed scheme, known extreme studentized cooperative consensus spectrum sensing (ESCCSS), was implemented in an ad hoc cognitive radio networks environment where the use of a data fusion centre (DFC) is not required. Cognitive radios make their own data fusion and make the final decision about the availability of the spectrum on their sensed reports and reports from their neighbouring nodes without any assistance from the fusion centre. MATLAB was used to implement and simulate the proposed scheme. We compared our scheme with Attack-Proof Cooperative Spectrum Sensing to check its effectiveness in combating the effect of byzantine attack.

Durant les deux dernières décennies, l'ubiquité et la prolifération des technologies sans fil ont entrainé une forte augmentation de demande de la ressource spectrale. Face à la croissance incessante du nombre d'utilisateurs désirant accéder au réseau, il existera un risque assez élevé de congestion au niveau de l'accès au spectre radio. Pour pallier à ce problème, il devient essentiel de recourir à un partage dynamique du spectre au détriment du mode de gestion statique de la bande de fréquence. L'avènement de la radio cognitive répond pertinemment aux besoins actuels car elle permet à des utilisateurs dits secondaires d'accéder à des bandes de fréquence qui restent affectées à des utilisateurs dits primaires. Les différents algorithmes proposés ont été examinés par simulation sur des scenarios qui illustrent les résultats théoriques obtenus. Les résultats de simulations démontrent que les méthodes proposées permettaient de trouver des solutions qui sont très proches de l'optimale.Au regard de certaines caractéristiques inhérentes aux modulations à porteuses multiples, celles-ci sont très appropriées à la couche physique des réseaux de radio cognitive. Cependant, le manque de coopération active entre les utilisateurs primaires et secondaires est susceptible d'entrainer une communication désynchronisée entre les système primaires et secondaires. En conséquence, une allocation judicieuse en termes de ressource radio et de contrôle de puissance devient impérative pour combattre l'effet négatif propre aux transmissions asynchrones qui devient aussi un défi de taille pour la conception et la mise en œuvre des réseaux de radio cognitive. Dans cette thèse, nous nous intéressons à l'étude de certaines problématiques d'allocation de ressources pour un réseau désynchronisé de radio cognitive qui utilise des modulations à porteuses multiples. Dans un premier temps, nous supposons que la connaissance des informations de canal est disponible à l'émission. Nous étudions des techniques permettant d'optimiser l'allocation de ressources afin de minimiser la somme des puissances émises au niveau des utilisateurs secondaires. Nous nous intéressons aussi à la conception d'algorithmes permettant d'optimiser l'efficacité énergétique des utilisateurs secondaires. La seconde partie de la thèse concerne l'optimisation de la fonction d'utilité des utilisateurs secondaires en tenant compte des contraintes de probabilité de coupure des utilisateurs primaires et secondaires. Cette probabilité de coupure découle de l'hypothèse de la connaissance de la distribution du canal au niveau des stations de base secondaires. Les différents algorithmes proposés ont été examinés par simulation afin d'illustrer les résultats théoriques obtenus. Les résultats de simulations démontrent que les méthodes proposées permettent de trouver des solutions qui sont très proches de l'optimale. / The ubiquity and proliferation of wireless technology and services considerably lead to a sharp increase in the number of individuals requiring access to wireless networks in recent decades. The growing number of mobile subscribers results into a dramatic increasing request for more radio spectrum. Consequently, underutilized yet scarce radio spectrum becomes overwhelmingly crowded. Therefore, the advent of new radio resource management paradigm capable of switching from static licensed spectrum management to dynamic spectrum access is of great importance. Cognitive radio (CR) emerged as a promising technology capable of enhancing the radio spectrum by permitting unlicensed users known as secondary users to coexist with primary users. Meanwhile, multi-carrier modulations that can efficiently overcome the detrimental effect of multipath fading in a wireless channel are very appealing for the physical layer of cognitive radio networks. However, the lack of cooperation between primary and secondary users may lead to asynchronous transmission and consequently result into inter-carrier interferences. Judicious resource allocation frameworks need to be designed in order to maintain the coexistence between primary and secondary users. Guaranteeing secondary users' quality of service (QoS), while ensuring that interferences generated to the primary users are tolerable, poses significant challenges for the design of wireless cognitive radio networks. This dissertation focuses on resource, i.e. subcarrier and power, allocation for multi-carrier-based downlink cognitive radio networks under perfect or statistical channel state information (CSI) with secondary users interact either cooperatively or competitively. Firstly, the problem of margin adaptive and energy-efficiency optimization are investigated considering perfect CSI at the secondary users' side. Secondly, assuming statistical CSI available at the secondary users, we address the problem of utility maximization under primary and secondary outage constraints. We provide some near-optimal resource allocation schemes to tackle the aforementioned problems. The findings and proposed frameworks can eventually be used for performance assessment and design of practical cognitive radio networks.

A research report submitted to the Faculty of Humanities, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Arts (in the field of ICT Policy and Regulation), October 2017 / Spectrum management reforms involve a departure from state-commanded administrative methods to market-driven property rights and or technology-enabled spectrum commons. This study explores spectrum management reforms that have been undertaken in the last decade, between 2006 and 2016, in the Southern African Development Community (SADC) region, with specific focus on the mobile broadband (MBB) industry. As a result, only spectrum bands allocated to terrestrial mobile and identified for International Mobile Telecommunications (IMT) by the International Telecommunication Union (ITU) in ITU Region 1 (Europe, Middle East and Africa) were considered. The purpose was to firstly analyse the progress thus far in reforming spectrum management practice in the region and secondly to critically analyse the effects of these reforms on the MBB industry in SADC within the framework of high demand for more spectrum as the cornerstone for rapid diffusion of MBB. Using a constructivist case study methodology, qualitative research was conducted in three SADC countries, namely, Botswana, Zambia and South Africa, representing small, medium and large markets respectively. The study draws on published documents such as policies, legislation, regulations and directly from individuals tasked with spectrum management in public and private sector organisations in these countries. The findings reveal that several market-driven reforms such as technology and service neutrality, spectrum re-farming and administrative incentive pricing (AIP), together with technology-enabled reforms such as commons or license-exempt spectrum for MBB technologies are all becoming widespread in the region. However, secondary trading and auctions have been stillborn concepts, partly due to market concentration concerns and appropriateness issues. The artificial scarcity of MBB spectrum supply in SADC is laid bare against a backdrop of general scarcity for demand and a discord over how this spectrum should be assigned and to whom. Vast amounts of allocated mobile spectrum in SADC lie fallow or are encumbered by other services such as broadcasting or at times are historically assigned to Fixed Wireless Access (FWA) applications. Analysis of the data from these three country case study provides insights that may be relevant to many other countries in the region. In conclusion, the study advances that the implementation of spectrum management reforms should be nuanced as these can impact, positively or negatively, on the distributive agenda of government. This research further advances knowledge by positing a novel conceptual framework for spectrum management reform based on the finding that the latter is not a binary exercise of a departure from administrative approach to either a market-driven or a technology-enabled one. However, spectrum management reform can be a continuum on which different elements of administrative, market-driven and technology-enabled approaches can be applied to varying degrees, depending on the respective country’s context. / XL2019

Cognitive radio (CR) technology introduces a revolutionary wireless communication mechanism in terminals and network segments, so that they are able to learn their environment and adapt intelligently to the most appropriate way of providing the service for the user's exact need. By supporting multi-band, mode-mode cognitive applications, the cognitive radio addresses an interactive way of managing the spectrum that harmonizes technology, market and regulation. This dissertation gives a complete story of building a cognitive radio. It goes through concept clarification, architecture definition, functional block building, system integration, and finally to the implementation of a fully-functional cognitive radio node prototype that can be directly packaged for application use. This dissertation starts with a comprehensive review of CR research from its origin to today. Several fundamental research issues are then addressed to let the reader know what makes CR a challenging and interesting research area. Then the CR system solution is introduced with the details of its hierarchical functional architecture called the Egg Model, modular software system called the cognitive engine, and the kernel machine learning mechanism called the cognition cycle. Next, this dissertation discusses the design of specific functional building blocks which incorporate environment awareness, solution making, and adaptation. These building blocks are designed to focus on the radio domain that mainly concerns the radio environment and the radio platform. Awareness of the radio environment is achieved by extracting the key environmental features and applying statistical pattern recognition methods including artificial neural networks and k-nearest neighbor clustering. Solutions for the radio behavior are made according to the recognized environment and the previous knowledge through case based reasoning, and further adapted or optimized through genetic algorithm solution search. New experiences are gained through the practice of the new solution, and thus the CR's knowledge evolves for future use; therefore, the CR's performance continues improving with this reinforcement learning approach. To deploy the solved solution in terms of the radio's parameters, a platform independent radio interface is designed. With this general radio interface, the algorithms in the cognitive engine software system can be applied to various radio hardware platforms. To support and verify designed cognitive algorithms and cognitive functionalities, a complete reconfigurable SDR platform, called the CWT2 waveform framework, is designed in this dissertation. In this waveform framework, a hierarchical configuration and control system is constructed to support flexible, real-time waveform reconfigurability. Integrating all the building blocks described above allows a complete CR node system. Based on this general CR node structure, a fully-functional Public Safety Cognitive Radio (PSCR) node is prototyped to provide the universal interoperability for public safety communications. Although the complete PSCR node software system has been packaged to an official release including installation guide and user/developer manuals, the process of building a cognitive radio from concept to a functional prototype is not the end of the CR research; on-going and future research issues are addressed in the last chapter of the dissertation. / Ph. D.

The Virginia Tech Center for Wireless Telecommunications' (CWT) Public Safety Cognitive Radio (PSCR) addresses the radio interoperability issues that plague many of the existing public safety radios — disparate frequency bands, incompatible modulation schemes and lack of active channel detection features. The PSCR allows the operator to scan for active channels, classify the detected channels, connect to any of the recognized waveforms and begin analog audio communication as well as bridge two incompatible waveforms together. The PSCR, although very useful, unfortunately is not portable enough to be used by public safety officials. The power requirement, processing requirement and equipment is respectively large, hungry and bulky. In this thesis, a possible solution to the portability problem is addressed by installing the PSCR in a public safety vehicle and using a Personal Digital Assistant (PDA) for remote access. The PDA allows the user to remotely scan, classify, talk, and bridge waveforms similar in operation to the PSCR. An ergonomically designed interface masks the channel and modulation selection procedure. This architecture can be extended to offer service to any remotely connected device. In the second part of this thesis, the concept of remote access is extended to a wide-area wireless public safety network. A public safety network consisting of heterogeneous devices is proposed utilizing a small number of backbone nodes. The major research focus of this section is the algorithm for distributing services across the network. Service discovery is optimized to reduce the overhead of service messages and multiple service distribution techniques are utilized depending on the location of the services. Simulation is performed to evaluate the performance of the service discovery protocol in terms of overhead, dissemination time and scalability. The proposed protocol is determined to be superior to the competition in the overhead and scalability tests. / Master of Science

The need for interoperability in emergency communication systems has hastened the development of cognitive radio technology. However, even though a cognitive radio system technically interconnects participating agencies, interoperability depends not only on technical matters but also organizational issues related to the different individuals, working contexts and types of cooperative work involved. In order to support public safety workers such as police, firefighters, and Emergency Medical Service (EMS) providers appropriately, it is vital to consider the dynamics of the way they interact in any collaborative situation. The purpose of this study is to develop an in-depth understanding of interoperability and construct a new model based on this understanding, along with a working model of an interoperable communication system to serve as a design framework that (1) supports effective public safety communication and (2) incorporates cognitive radio capabilities to ensure optimal semantic interoperability. An adequate model for interoperability must include multiple dimensions to explain both the concept of interoperability in the public safety domain and its relationships with task characteristics and information needs. This model focuses primarily on the requirements for communication systems. The value perspective reflects the evaluation criteria for effective team communication such as semantic interoperability, task routineness, and information processing aspects. The design framework incorporates the proposed model into Work Domain Analysis (WDA). To achieve these research objectives, a series of studies was conducted. The first was a qualitative exploratory study that identified how the concept of interoperability is manifested in the public safety work domain. Through the use of semi-structured interviews, communication patterns in terms of interoperability were placed in a real world context. The responses from the participants were categorized in terms of the dimensions of interoperability and reinterpreted using sensemaking as a theoretical framework. The dimensions of interoperability identified consisted of information sharedness, communication readiness, operational awareness, adaptiveness, and coupledness. Based on these findings, a new instrument was proposed to measure interoperability for communication systems. This instrument was then statistically validated. The second study identified the effects of different types of operation and types of organization on interoperability, as well as investigating the relationships among interoperability, task routineness and information processing using Structural Equation Modeling (SEM). Based on this understanding and theoretical perspective, a new interoperable communication structure was delineated in the model. A prototype of a public safety cognitive radio communication system was then developed based on the proposed framework and examined using a focus group in order to validate the proposed model and design framework and highlight any usability issues that may affect the prototype's operational effectiveness. / Ph. D.

Reconfigurable computing architectures are well suited for the dynamic data flow processing requirements of software-defined radio. The software radio concept has quickly evolved to include spectrum sensing, awareness, and cognitive algorithms for machine learning resulting in the cognitive radio model. This work explores the application of reconfigurable hardware to the physical layer of cognitive radios using non-contiguous multi-carrier radio techniques. The practical tasks of spectrum sensing, frame detection, synchronization, channel estimation, and mutual interference mitigation are challenges in the communications and the computing fields that are addressed to optimally utilize the capacity of opportunistically allocated spectrum bands. FPGA implementations of parameterizable OFDM and filter bank multi-carrier (FBMC) radio prototypes with spectrum awareness and non-contiguous sub-carrier allocation were completed and tested over-the-air. Sub-carrier sparseness assumptions were validated under practical implementation and performance considerations. A novel algorithm for frame detection and synchronization with mutual interference rejection applicable to the FBMC case was proposed and tested. / Ph. D.