145 research outputs found

    Channel parameter tuning in a hybrid Wi-Fi-Dynamic Spectrum Access Wireless Mesh Network

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    This work addresses Channel Assignment in a multi-radio multi-channel (MRMC) Wireless Mesh Network (WMN) using both Wi-Fi and Dynamic Spectrum Access (DSA) spectrum bands and standards. This scenario poses new challenges because nodes are spread out geographically so may have differing allowed channels and experience different levels of external interference in different channels. A solution must meet two conflicting requirements simultaneously: 1) avoid or minimise interference within the network and from external interference sources, and 2) maintain connectivity within the network. These two requirements must be met while staying within the link constraints and the radio interface constraints, such as only assigning as many channels to a node as it has radios. This work's original contribution to the field is a unified framework for channel optimisation and assignment in a WMN that uses both DSA and traditional Wi-Fi channels for interconnectivity. This contribution is realised by providing and analysing the performance of near-optimal Channel Assignment (CA) solutions using metaheuristic algorithms for the MRMC WMNs using DSA bands. We have created a simulation framework for evaluating the algorithms. The performance of Simulated Annealing, Genetic Algorithm, Differential Evolution, and Particle Swarm Optimisation algorithms have been analysed and compared for the CA optimisation problem. We introduce a novel algorithm, used alongside the metaheuristic optimisation algorithms, to generate feasible candidate CA solutions. Unlike previous studies, this sensing and CA work takes into account the requirement to use a Geolocation Spectrum Database (GLSD) to get the allowed channels, in addition to using spectrum sensing to identify and estimate the cumulative severity of both internal and external interference sources. External interference may be caused by other secondary users (SUs) in the vicinity or by primary transmitters of the DSA band whose emissions leak into adjacent channels, next-toadjacent, or even into further channels. We use signal-to-interference-plus-noise ratio (SINR) as the optimisation objective. This incorporates any possible source or type of interference and makes our method agnostic to the protocol or technology of the interfering devices while ensuring that the received signal level is high enough for connectivity to be maintained on as many links as possible. To support our assertion that SINR is a reasonable criterion on which to base the optimisation, we have carried out extensive outdoor measurements in both line-of-sight and wooded conditions in the television white space (TVWS) DSA band and the 5 GHz Wi-Fi band. These measurements show that SINR is useful as a performance measure, especially when the interference experienced on a link is high. Our statistical analysis shows that SINR effectively differentiates the performance of different channels and that SINR is well correlated with throughput and is thus a good predictor of end-user experience, despite varying conditions. We also identify and analyse the idle times created by Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) contention-based Medium Access Control (MAC) operations and propose the use of these idle times for spectrum sensing to measure the SINR on possible channels. This means we can perform spectrum sensing with zero spectrum sensing delay experienced by the end user. Unlike previous work, this spectrum sensing is transparent and can be performed without causing any disruption to the normal data transmission of the network. We conduct Markov chain analysis to find the expected length of time of a sensing window. We also derive an efficient minimum variance unbiased estimator of the interference plus noise and show how the SINR can be found using this estimate. Our estimation is more granular, accurate, and appropriate to the problem of Secondary User (SU)-SU coexistence than the binary hypothesis testing methods that are most common in the literature. Furthermore, we construct confidence intervals based on the probability density function derived for the observations. This leads to finding and showing the relationships between the number of sampling windows and sampling time, the interference power, and the achievable confidence interval width. While our results coincide with (and thus are confirmed by) some key previous recommendations, ours are more precise, granular, and accurate and allow for application to a wider range of operating conditions. Finally, we present alterations to the IEEE 802.11k protocol to enable the reporting of spectrum sensing results to the fusion or gateway node and algorithms for distributing the Channel Assignment once computed. We analyse the convergence rate of the proposed procedures and find that high network availability can be maintained despite the temporary loss of connectivity caused by the channel switching procedure. This dissertation consolidates the different activities required to improve the channel parameter settings of a multi-radio multi-channel DSA-WMN. The work facilitates the extension of Internet connectivity to the unconnected or unreliably connected in rural or peri-urban areas in a more cost-effective way, enabling more meaningful and affordable access technologies. It also empowers smaller players to construct better community networks for sharing local content. This technology can have knock-on effects of improved socio-economic conditions for the communities that use it

    Advances in Information Security and Privacy

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    With the recent pandemic emergency, many people are spending their days in smart working and have increased their use of digital resources for both work and entertainment. The result is that the amount of digital information handled online is dramatically increased, and we can observe a significant increase in the number of attacks, breaches, and hacks. This Special Issue aims to establish the state of the art in protecting information by mitigating information risks. This objective is reached by presenting both surveys on specific topics and original approaches and solutions to specific problems. In total, 16 papers have been published in this Special Issue

    A Survey on the Communication Protocols and Security in Cognitive Radio Networks

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    A cognitive radio (CR) is a radio that can change its transmission parameters based on the perceived availability of the spectrum bands in its operating environment. CRs support dynamic spectrum access and can facilitate a secondary unlicensed user to efficiently utilize the available underutilized spectrum allocated to the primary licensed users. A cognitive radio network (CRN) is composed of both the secondary users with CR-enabled radios and the primary users whose radios need not be CR-enabled. Most of the active research conducted in the area of CRNs has been so far focused on spectrum sensing, allocation and sharing. There is no comprehensive review paper available on the strategies for medium access control (MAC), routing and transport layer protocols, and the appropriate representative solutions for CRNs. In this paper, we provide an exhaustive analysis of the various techniques/mechanisms that have been proposed in the literature for communication protocols (at the MAC, routing and transport layers), in the context of a CRN, as well as discuss in detail several security attacks that could be launched on CRNs and the countermeasure solutions that have been proposed to avoid or mitigate them. This paper would serve as a good comprehensive review and analysis of the strategies for MAC, routing and transport protocols and security issues for CRNs as well as would lay a strong foundation for someone to further delve onto any particular aspect in greater depth

    A cognitive radio-based fully blind multihop rendezvous protocol for unknown environments

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    In Cognitive Radio networking, the blind rendezvous problem is when two or more nodes must establish a link, but where they have no predefined schedule or common control channel for doing so. The problem becomes more challenging when the information about the existence of other nodes in the network, their topology, and primary user activity are also unknown, identified here as a fully blind rendezvous problem. In this paper, a novel and fully blind multihop (FBM) rendezvous framework is proposed with an extended modular clock algorithm (EMCA). The EMCA-FBM is a fully blind multihop rendezvous protocol as it assumes the number of nodes, primary radio activity and topology information as unknown. It is shown to work with different Cognitive Radio operating policies to achieve adaptiveness towards the unknown primary radio activity, and self-organization for autonomously handling the rendezvous process by using transmission schedules. It is capable of working without any information of neighbor nodes and terminating the rendezvous process whenever all or sufficient nodes are discovered. The proposed FBM is also shown to work as a general framework to extend existing single hop rendezvous protocols to work as a multihop rendezvous protocol. In comparison with other modified blind rendezvous strategies for multihop network, the combination of the proposed EMCA-FBM protocol and operating policies is shown to be effective in improving the average time to rendezvous (up to 70%) and neighbor discovery accuracy (almost 100%) while reducing harmful interference

    Storia delle telecomunicazioni

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    Focusing on the history of scientific and technological development over recent centuries, the book is dedicated to the history of telecommunications, where Italy has always been in the vanguard, and is presented by many of the protagonists of the last half century. The book is divided into five sections. The first, dealing with the origins, starts from the scientific bases of the evolution of telecommunications in the nineteenth century (Bucci), addressing the developments of scientific thought that led to the revolution of the theory of fields (Morando), analysing the birth of the three fundamental forms of communication – telegraph (Maggi), telephone (Del Re) and radio (Falciasecca) – and ending with the contribution made by the Italian Navy to the development of telecommunications (Carulli, Pelosi, Selleri, Tiberio). The second section, on technical and scientific developments, presents the numerical processing of signals (Rocca), illustrating the genesis and metamorphosis of transmission (Pupolin, Benedetto, Mengali, Someda, Vannucchi), network packets (Marsan, Guadagni, Lenzini), photonics in telecommunications (Prati) and addresses the issue of research within the institutions (Fedi-Morello), dwelling in particular on the CSELT (Mossotto). The next section deals with the sectors of application, offering an overview of radio, television and the birth of digital cinema (Vannucchi, Visintin), military communications (Maestrini, Costamagna), the development of radar (Galati) and spatial telecommunications (Tartara, Marconicchio). Section four, on the organisation of the services and the role of industry, outlines the rise and fall of the telecommunications industries in Italy (Randi), dealing with the telecommunications infrastructures (Caroppo, Gamerro), the role of the providers in national communications (Gerarduzzi), the networks and the mobile and wireless services (Falciasecca, Ongaro) and finally taking a look towards the future from the perspective of the last fifty years (Vannucchi). The last section, dealing with training and dissemination, offers an array of food for thought: university training in telecommunications, with focus on the evolution of legislation and on the professional profiles (Roveri), social and cultural aspects (Longo and Crespellani) as well as a glance over the most important museums, collections and documentary sources for telecommunications in Italy (Lucci, Savini, Temporelli, Valotti). The book is designed to offer a compendium comprising different analytical approaches, and aims to foster an interest in technology in the new generations, in the hope of stimulating potentially innovative research

    Recent Advances in Wireless Communications and Networks

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    This book focuses on the current hottest issues from the lowest layers to the upper layers of wireless communication networks and provides "real-time" research progress on these issues. The authors have made every effort to systematically organize the information on these topics to make it easily accessible to readers of any level. This book also maintains the balance between current research results and their theoretical support. In this book, a variety of novel techniques in wireless communications and networks are investigated. The authors attempt to present these topics in detail. Insightful and reader-friendly descriptions are presented to nourish readers of any level, from practicing and knowledgeable communication engineers to beginning or professional researchers. All interested readers can easily find noteworthy materials in much greater detail than in previous publications and in the references cited in these chapters

    An artificial intelligence based quorum system for the improvement of the lifespan of sensor networks.

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    Artificial Intelligence-based Quorum systems are used to solve the energy crisis in real-time wireless sensor networks. They tend to improve the coverage, connectivity, latency, and lifespan of the networks where millions of sensor nodes need to be deployed in a smart grid system. The reality is that sensors may consume more power and reduce the lifetime of the network. This paper proposes a quorum-based grid system where the number of sensors in the quorum is increased without actually increasing quorums themselves, leading to improvements in throughput and latency by 14.23%. The proposed artificial intelligence scheme reduces the network latency due to an increase in time slots over conventional algorithms previously proposed. Secondly, energy consumption is reduced by weighted load balancing, improving the network’s actual lifespan. Our experimental results show that the coverage rate is increased on an average of 11% over the conventional Coverage Contribution Area (CCA), Partial Coverage with Learning Automata (PCLA), and Probabilistic Coverage Protocol (PCP) protocols respectively

    Mobile Ad-Hoc Networks

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    Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks
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