Optimal time sharing in underlay cognitive radio systems with RF energy harvesting

Due to the fundamental tradeoffs, achieving spectrum efficiency and energy efficiency are two contending design challenges for the future wireless networks. However, applying radio-frequency (RF) energy harvesting (EH) in a cognitive radio system could potentially circumvent this tradeoff, resulting in a secondary system with limitless power supply and meaningful achievable information rates. This paper proposes an online solution for the optimal time allocation (time sharing) between the EH phase and the information transmission (IT) phase in an underlay cognitive radio system, which harvests the RF energy originating from the primary system. The proposed online solution maximizes the average achievable rate of the cognitive radio system, subject to the $\varepsilon$-percentile protection criteria for the primary system. The optimal time sharing achieves significant gains compared to equal time allocation between the EH and IT phases.Comment: Proceedings of the 2015 IEEE International Conference on Communications (IEEE ICC 2015), 8-12 June 2015, London, U

Performance analysis of a novel decentralised MAC protocol for cognitive radio networks

Due to the demand of emerging Cognitive Radio (CR) technology to permits using the unused licensed spectrum parts by cognitive users (CUs) to provide opportunistic and efficient utilisation of the white spaces. This requires deploying a CR MAC with the required characteristics to coordinate the spectrum access among CUs. Therefore, this paper presents the design and implementation of a novel Medium Access Control (MAC) protocol for decentralised CRNs (MCRN). The protocol provides efficient utilisations of the unused licensed channels and enables CUs to exchange data successfully over licensed channels. This is based on the observation procedure of sensing the status of the Licensed Users (LUs) are ON or OFF over the licensed channels. The protocol is validated with the comparison procedure against two different benchmark protocols in terms of the network performance; communication time and throughput. Therefore, performance analysis demonstrated that the proposed MCRN perform better and achieve higher throughput and time benefits than the benchmarks protocols

Software-defined routing protocol for mobile cognitive radio networks : a cross-layer perspective

The growing demand for wireless applications, combined with inefficient spectrum use, necessitates developing a new wireless communication paradigm that focuses on dynamic spectrum access rather than the fixed spectrum using cognitive radio technology. The unlicensed user, known as secondary user or cognitive user, uses cognitive radio technology to grow opportunistic communication over licensed spectrum bands and improve spectrum management performance. The routing protocol in Cognitive Radio Networks (CRNs) serves as a communication backbone, allowing data packets to transfer between cognitive user nodes through multiple paths and channels. However, the problem of routing in CRNs is to create a robust-stable route over higher channel availability. The previously developed protocols missed opportunities to exploit the time-variant channel estimation technique, which selects the best route using the cross-layer routing decision engine to track the adverse impact of cognitive user mobility and primary user activity. This study aims to construct a robust routing path while limiting interference with primary user activity, delaying routing, and maximizing routing throughput. Here, a new routing framework is created in this study to explore new extended routing functions and features from the lower layers (Physical layer and Data Link layer) feedback to improve routing performance. Then, the link-oriented channel availability and channel quality have been developed based on two reliable metrics, which are channel availability probability and channel quality, to estimate and select a channel that maximizes link-throughput. Furthermore, this study proposes a novel cross layer routing protocol, namely, the Software-Defined Routing Protocol. It is a cross-layer method to combine the lower layer (Physical layer and Data Link layer) sensing derived from the channel estimation model. It periodically updates the routing table for optimal route decision making. The output simulation of the channel estimation method has shown that it has produced a powerful channel selection strategy to maximize the average rate of link throughput and achieved a channel estimate under the time-variant effect. Extensive simulation experiments have been performed to evaluate the proposed protocol in compression with the existing benchmark protocols, namely, dual diversity cognitive Ad-hoc routing protocol and cognitive Ad-hoc on-demand distance vector. The proposed protocol outperforms the benchmarks, resulting in increasing the packet delivery ratio by around (11.89%-12.80%), reducing delay by around (2.74%-4.05%), reducing overhead by around (14.31%-18.36%), and increasing throughput by around (23.94%-28.35%). The software-defined routing protocol, however, lacks the ability to determine the better idle channel at high-speed node mobility. In conclusion, the cross-layer routing protocol successfully achieves high routing performance in finding a robust route, selecting high channel stability, and reducing the probability of interference with primary users for continued communication

MITIGACIÓN DE TORMENTA DE BROADCAST EN LA TRANSMISIÓN DE MENSAJES DE EMERGENCIA USANDO COMPARTICIÓN DE ESPECTRO EN VANETS DE RADIO COGNOSCITIVO (BROADCAST STORM MITIGATION IN EMERGENCY MESSAGES TRANSMISSION USING SPECTRUM SHARING IN COGNITIVE RADIO VANETS)

El denominado fenómeno de tormenta de broadcast presente en las redes inalámbricas y con gran número de nodos; es importante atacarlo durante la implementación de aplicaciones de seguridad en las redes vehiculares de radio cognoscitivo (COG-VANETs). En este trabajo se presenta una breve introducción a las COG-VANETs y radio cognoscitivo, y como es que estas dos tecnologías se pueden conjuntar para ayudar a la transmisión eficiente de mensajes de seguridad. Se presenta el modelo matemático que utiliza la banda de Comunicaciones Dedicadas de Rango Corto (DSRC) y la banda de Espacios en blanco de TV (TVWS) para la transmisión de los mensajes de seguridad. Se muestran los resultados del modelo bajo condiciones de saturación de la densidad, y se abordan la discusión y conclusiones de los efectos de la densidad y como se relaciona directamente con el problema de tormenta de broadcast, además se sugieren líneas de solución y mejora.The so-called broadcast storm phenomenon which is common at wireless networks and in other networks with high number of users; it is important to attack it in the implementation of security applications in the cognitive radio vehicle networks (COG-VANETs). This paper presents a brief introduction to COG-VANETs and cognitive radio and how these two technologies can be combined to help the efficient transmission of safety messages. In this work is presented the mathematical model that incorporates the Dedicated Short-Range Communications (DSRC) and TV White Spaces (TVWS) bands for the transmission of safety messages. Also the results of the model under conditions of saturation of density are shown, and the discussion and conclusions of the effects of density and how it relates directly to the problem of broadcast storm are addressed. Lines of solution and improvement are also suggested in order to mitigate this phenomenon

Survey of Spectrum Sharing for Inter-Technology Coexistence

Increasing capacity demands in emerging wireless technologies are expected to be met by network densification and spectrum bands open to multiple technologies. These will, in turn, increase the level of interference and also result in more complex inter-technology interactions, which will need to be managed through spectrum sharing mechanisms. Consequently, novel spectrum sharing mechanisms should be designed to allow spectrum access for multiple technologies, while efficiently utilizing the spectrum resources overall. Importantly, it is not trivial to design such efficient mechanisms, not only due to technical aspects, but also due to regulatory and business model constraints. In this survey we address spectrum sharing mechanisms for wireless inter-technology coexistence by means of a technology circle that incorporates in a unified, system-level view the technical and non-technical aspects. We thus systematically explore the spectrum sharing design space consisting of parameters at different layers. Using this framework, we present a literature review on inter-technology coexistence with a focus on wireless technologies with equal spectrum access rights, i.e. (i) primary/primary, (ii) secondary/secondary, and (iii) technologies operating in a spectrum commons. Moreover, we reflect on our literature review to identify possible spectrum sharing design solutions and performance evaluation approaches useful for future coexistence cases. Finally, we discuss spectrum sharing design challenges and suggest future research directions

A Self-Learning MAC Protocol for Energy Harvesting and Spectrum Access in Cognitive Radio Sensor Networks

The fusion of Wireless Sensor Networks (WSNs) and Cognitive Radio Networks (CRNs) into Cognitive Radio Sensor Networks (CRSNs) is quite an attractive proposal, because it allows a distributed set of low-powered sensor nodes to opportunistically access spectrum bands that are underutilized by their licensed owners (called primary users (PUs)). In addition, when the PUs are actively transmitting in their own bands, sensor nodes can switch to energy harvesting mode to obtain their energy needs (for free), to achieve almost perpetual life. In this work, we present a novel and fully distributed MAC protocol, called S-LEARN, that allows sensor nodes in a CRSN to entwine their RF energy harvesting and data transmission activities, while intelligently addressing the issue of disproportionate difference between the high power necessary for the node to transmit data packets and the small amount of power it can harvest wirelessly from the environment. The presented MAC protocol can improve both the network throughput and total harvested energy, while being robust to changes in the network configuration. Moreover, S-LEARN can keep the cost of the system low, and it avoids the pitfalls from which centralized systems suffer

Secure MAC protocols for cognitive radio networks

A thesis submitted in partial fulfilment for the degree of Doctor of PhilosophyWith the rapid increase in wireless devices, an effective improvement in the demand of efficient spectrum utilisation for gaining better connectivity is needed. Cognitive Radio (CR) is an emerging technology that exploits the inefficient utilisation of the unused spectrum dynamically. Since spectrum sharing is responsible for coordinating channels’ access for Cognitive Users (CUs), the Common Control Channel (CCC) is one of the existing methods used to exchange the control information between CUs. However, the unique characteristics and parameters of Cognitive Radio Networks (CRNs) present several possible threats targeting spectrum sensing, spectrum management, spectrum sharing, and spectrum mobility leading to the deterioration of the network performance. Thus, protection and detection security mechanisms are essential to maintaining the CRNs. This thesis presents a novel decentralised CR MAC protocol that successfully utilises the unused portion of the licensed band. The protocol achieves improved performance; communication time and throughput when compared to two benchmark protocols. Less communication time and higher throughput are accomplished by the protocol due to performing fast switching to the selected available data channel for initiating data transmission. The proposed protocol is then extended to two different versions based on two authentication approaches applied to it; one using Digital Signature and another is based on Shared-Key. The two proposed secure protocols address the security requirements in CRNs leading to subsequent secure communication among CUs. The protocols function effectively in providing defence against several attacks related to the MAC layer such as; Spectrum Sensing Data Manipulation/Falsification, Data Tempering and Modification, Jamming attacks, Eavesdropping, Forgery and Fake control information attacks, MAC address spoofing, and unauthorised access attacks. The associated security algorithms ensure the successful secure communication between CUs in a cooperative approach. Moreover, the security protocols are investigated and analysed in terms of security flows by launching unauthorised access and modification attacks on the transmitted information. The testing results demonstrated that two protocols perform successful detection of threats and ensure secure communication in CRNs

Um protocolo de controle de acesso baseado em rede neural recorrente para comunicação oportunística em redes wifi

Trabalho de Conclusão de Curso (graduação)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, 2019.A Cisco estima que em 2021 haverá 5.5 bilhões de celulares no mundo [1]. O tráfego de dados móveis ao redor do mundo chegará aos 49 Exabytes mensais, estimando uma taxa de crescimento anual de 47% entre 2016 e 2021. Esse amplo crescimento trouxe a dúvida, se seria possível acomodar todos esses novos usuários no espectro disponível. Pois este, mesmo podendo ser utilizado diversas vezes, possui uma quantidade limitada de frequências disponíveis para este fim. O principal causador dessa problemática é a forma como o espectro é gerenciado atualmente. Hoje o espectro de frequência para comunicações sem fio é dividido em blocos de fre- quências que são licenciados para usuários que têm prioridade no uso (usuários primários) [2]. Essa abordagem mostra sua ineficiência ao permitir que certas porções do espectro fiquem ociosas quando usuários primários estão inativos. Surgiu então a ideia de per- mitir que usuários que não possuem o direito licenciado ao uso do espectro (usuários secundários), usem essas porções ociosas do espectro, desde que não interferissem nas comunicações dos usuários primários [3]. Com isso tecnologias como o uso de Rádios Cognitivos surgiram para gerenciar essas comunicações e aumentar o uso eficiente do canal. Este trabalho estudará uma forma mais eficiente de utilizar o espectro propondo um protocolo que possibilita o acessá-lo de forma oportunística usando uma Rede Neural desenvolvida nos trabalhos [4] [5], apresentando dados comparativos com o protocolo 802.11, que é o mais usado para gerenciamento do espectro por dispositivos móveis, através de simulações.Cisco estimates mobile data traffic around the world will reach 49 monthly Exabytes, estimating an annual growth rate of 47% between 2016 and 2021 [1]. The question is: it would be possible to accommodate all these new users in the spectrum available. Even it can be used several times, has a limited amount of frequencies available for this purpose. The main cause of this problem is the way the spectrum is currently managed. Today the frequency spectrum for wireless communications is divided into frequency blocks licensed to users who have priority in using them (primary users) [2]. This is inefficient because some parts of the spectrum become idle when users are inactive. One solution was to allow users who do not have the license to use the spectrum (secondary users), to use these idle portions of the spectrum, as long as they do not interfere with the primary users’ communications [3]. Technologies like Cognitive Radios have emerged to manage these communications and increase the efficient use of the channel. This work will study a more efficient way to use the spectrum. We will propose a protocol that implements opportunistic access to the channel using a trained Neural Network developed in the works [4] [5]. We will compare with simlations, the proposed protocol and the 802.11 protocol, which is the most used for spectrum management by mobile devices