Wirelessly Powered Backscatter Communication Networks: Modeling, Coverage and Capacity

Future Internet-of-Things (IoT) will connect billions of small computing devices embedded in the environment and support their device-to-device (D2D) communication. Powering this massive number of embedded devices is a key challenge of designing IoT since batteries increase the devices' form factors and battery recharging/replacement is difficult. To tackle this challenge, we propose a novel network architecture that enables D2D communication between passive nodes by integrating wireless power transfer and backscatter communication, which is called a wirelessly powered backscatter communication (WP-BackCom) network. In the network, standalone power beacons (PBs) are deployed for wirelessly powering nodes by beaming unmodulated carrier signals to targeted nodes. Provisioned with a backscatter antenna, a node transmits data to an intended receiver by modulating and reflecting a fraction of a carrier signal. Such transmission by backscatter consumes orders-of-magnitude less power than a traditional radio. Thereby, the dense deployment of low-complexity PBs with high transmission power can power a large-scale IoT. In this paper, a WP-BackCom network is modeled as a random Poisson cluster process in the horizontal plane where PBs are Poisson distributed and active ad-hoc pairs of backscatter communication nodes with fixed separation distances form random clusters centered at PBs. The backscatter nodes can harvest energy from and backscatter carrier signals transmitted by PBs. Furthermore, the transmission power of each node depends on the distance from the associated PB. Applying stochastic geometry, the network coverage probability and transmission capacity are derived and optimized as functions of backscatter parameters, including backscatter duty cycle and reflection coefficient, as well as the PB density. The effects of the parameters on network performance are characterized.Comment: 28 pages, 11 figures, has been submitted to IEEE Trans. on Wireless Communicatio

Drone-Assisted Wireless Communications

In order to address the increased demand for any-time/any-where wireless connectivity, both academic and industrial researchers are actively engaged in the design of the fifth generation (5G) wireless communication networks. In contrast to the traditional bottom-up or horizontal design approaches, 5G wireless networks are being co-created with various stakeholders to address connectivity requirements across various verticals (i.e., employing a top-to-bottom approach). From a communication networks perspective, this requires obliviousness under various failures. In the context of cellular networks, base station (BS) failures can be caused either due to a natural or synthetic phenomenon. Natural phenomena such as earthquake or flooding can result in either destruction of communication hardware or disruption of energy supply to BSs. In such cases, there is a dire need for a mechanism through which capacity short-fall can be met in a rapid manner. Drone empowered small cellular networks, or so-called \quotes{flying cellular networks}, present an attractive solution as they can be swiftly deployed for provisioning public safety (PS) networks. While drone empowered self-organising networks (SONs) and drone small cell networks (DSCNs) have received some attention in the recent past, the design space of such networks has not been extensively traversed. So, the purpose of this thesis is to study the optimal deployment of drone empowered networks in different scenarios and for different applications (i.e., in cellular post-disaster scenarios and briefly in assisting backscatter internet of things (IoT)). To this end, we borrow the well-known tools from stochastic geometry to study the performance of multiple network deployments, as stochastic geometry provides a very powerful theoretical framework that accommodates network scalability and different spatial distributions. We will then investigate the design space of flying wireless networks and we will also explore the co-existence properties of an overlaid DSCN with the operational part of the existing networks. We define and study the design parameters such as optimal altitude and number of drone BSs, etc., as a function of destroyed BSs, propagation conditions, etc. Next, due to capacity and back-hauling limitations on drone small cells (DSCs), we assume that each coverage hole requires a multitude of DSCs to meet the shortfall coverage at a desired quality-of-service (QoS). Hence, we consider the clustered deployment of DSCs around the site of the destroyed BS. Accordingly, joint consideration of partially operating BSs and deployed DSCs yields a unique topology for such PS networks. Hence, we propose a clustering mechanism that extends the traditional Mat\'{e}rn and Thomas cluster processes to a more general case where cluster size is dependent upon the size of the coverage hole. As a result, it is demonstrated that by intelligently selecting operational network parameters such as drone altitude, density, number, transmit power and the spatial distribution of the deployment, ground user coverage can be significantly enhanced. As another contribution of this thesis, we also present a detailed analysis of the coverage and spectral efficiency of a downlink cellular network. Rather than relying on the first-order statistics of received signal-to-interference-ratio (SIR) such as coverage probability, we focus on characterizing its meta-distribution. As a result, our new design framework reveals that the traditional results which advocate lowering of BS heights or even optimal selection of BS height do not yield consistent service experience across users. Finally, for drone-assisted IoT sensor networks, we develop a comprehensive framework to characterize the performance of a drone-assisted backscatter communication-based IoT sensor network. A statistical framework is developed to quantify the coverage probability that explicitly accommodates a dyadic backscatter channel which experiences deeper fades than that of the one-way Rayleigh channel. We practically implement the proposed system using software defined radio (SDR) and a custom-designed sensor node (SN) tag. The measurements of parameters such as noise figure, tag reflection coefficient etc., are used to parametrize the developed framework

Design and Performance Analysis of Next Generation Heterogeneous Cellular Networks for the Internet of Things

The Internet of Things (IoT) is a system of inter-connected computing devices, objects and mechanical and digital machines, and the communications between these devices/objects and other Internet-enabled systems. Scalable, reliable, and energy-efficient IoT connectivity will bring huge benefits to the society, especially in transportation, connected self-driving vehicles, healthcare, education, smart cities, and smart industries. The objective of this dissertation is to model and analyze the performance of large-scale heterogeneous two-tier IoT cellular networks, and offer design insights to maximize their performance. Using stochastic geometry, we develop realistic yet tractable models to study the performance of such networks. In particular, we propose solutions to the following research problems: -We propose a novel analytical model to estimate the mean uplink device data rate utility function under both spectrum allocation schemes, full spectrum reuse (FSR) and orthogonal spectrum partition (OSP), for uplink two-hop IoT networks. We develop constraint gradient ascent optimization algorithms to obtain the optimal aggregator association bias (for the FSR scheme) and the optimal joint spectrum partition ratio and optimal aggregator association bias (for the OSP scheme). -We study the performance of two-tier IoT cellular networks in which one tier operates in the traditional sub-6GHz spectrum and the other, in the millimeter wave (mm-wave) spectrum. In particular, we characterize the meta distributions of the downlink signal-to-interference ratio (sub-6GHz spectrum), the signal-to-noise ratio (mm-wave spectrum) and the data rate of a typical device in such a hybrid spectrum network. Finally, we characterize the meta distributions of the SIR/SNR and data rate of a typical device by substituting the cumulative moment of the CSP of a user device into the Gil-Pelaez inversion theorem. -We propose to split the control plane (C-plane) and user plane (U-plane) as a potential solution to harvest densification gain in heterogeneous two-tier networks while minimizing the handover rate and network control overhead. We develop a tractable mobility-aware model for a two-tier downlink cellular network with high density small cells and a C-plane/U-plane split architecture. The developed model is then used to quantify effect of mobility on the foreseen densification gain with and without C-plane/U-plane splitting

Spatial networks with wireless applications

Many networks have nodes located in physical space, with links more common between closely spaced pairs of nodes. For example, the nodes could be wireless devices and links communication channels in a wireless mesh network. We describe recent work involving such networks, considering effects due to the geometry (convex,non-convex, and fractal), node distribution, distance-dependent link probability, mobility, directivity and interference.Comment: Review article- an amended version with a new title from the origina

Modélisation de Réseaux sans Fils de Grandes Dimensions à l'aide de la Géométrie Stochastique

The main goal of this work is to study cooperative aspects of large wireless networks from the perspective of stochastic geometry. This allows the consideration of important effects such as the random spatial distribution of nodes, as well as the effects of interference and interference correlation at receivers, which are not possible when a single link is considered in isolation.First, some aspects of the performance of the relay channel in the context of a large wireless network are considered. Mainly, the performance, in terms of outage probability (OP), of a single full-duplex relay channel utilizing decode-and-forward (DF) or compress-and-forward, when the interference is generated by uniform spatial deployment of nodes, modeled as a Poisson point process. The OP performance of these two protocols is compared with a point-to-point transmission and with a half-duplex DF protocol. Afterwards, the case in which more than one transmitter in the network may use a relay is considered. The effects of cooperation versus interference are studied, when the users use either full-duplex DF, or point-to-point transmissions. In a second phase, this work explores the advantages that could be obtained through out-of-band device-to-device (D2D) video file exchanges in cellular networks. These advantages are measured in terms of the fraction of requests that can be served in a time-block through D2D, thus avoiding a downlink file transfer from the base station. For this, a stochastic geometry framework is introduced, in which the user file-caching policy, user pairing strategy, and link quality and scheduling issues are considered.L'objectif de cette thèse est d'étudier certains aspects des réseaux coopératifs sans fils à l'aide de la géométrie stochastique. Ça permets de considérer la distribution spatiale aléatoire des utilisateurs et les effets adverses de leur interaction, comme l’interférence.Nous étudions la performance, évaluée par la probabilité d'outage, atteignable dans un canal de relai full-duplex quand les nœuds opèrent dans un grand réseau sans fils où les émetteurs interférants sont modelés avec un processus ponctuel de Poisson homogène. Nous trouvons la probabilité d'outage des protocoles décodez-et-renvoyez (decode-and-forward, DF), et comprimez-et-renvoyez (compress-and-forward) et nous faisons une comparaison avec une transmission point à point et un protocole DF half-duplex. Ensuite, nous étudions une situation plus générale dans laquelle les émetteurs qui causent l'interférence peuvent aussi utiliser un relai ou faire des transmissions point à point. Nous étudions la relation entre les avantages de la cooperation et l'interférence qu'elle même génère.Dans la deuxième partie nous étudions la performance des stratégies de partage de vidéos par communications entre dispositifs mobiles (device-to-device, D2D) hors de la bande des communications cellulaires. Nous étudions la fraction des demandes de vidéos qui peuvent être satisfaites par D2D, c’est-à-dire, par le biais des émissions locales, plutôt que par la station de base. Pour étudier ce problème, nous introduisons un modèle de processus ponctuel, qui considère la stratégie de stockage dans les utilisateurs, le problème de comment lier les utilisateurs et les problèmes de la transmission et coordination entre les utilisateurs

Internet of Things and Sensors Networks in 5G Wireless Communications

This book is a printed edition of the Special Issue Internet of Things and Sensors Networks in 5G Wireless Communications that was published in Sensors

Internet of Things and Sensors Networks in 5G Wireless Communications

The Internet of Things (IoT) has attracted much attention from society, industry and academia as a promising technology that can enhance day to day activities, and the creation of new business models, products and services, and serve as a broad source of research topics and ideas. A future digital society is envisioned, composed of numerous wireless connected sensors and devices. Driven by huge demand, the massive IoT (mIoT) or massive machine type communication (mMTC) has been identified as one of the three main communication scenarios for 5G. In addition to connectivity, computing and storage and data management are also long-standing issues for low-cost devices and sensors. The book is a collection of outstanding technical research and industrial papers covering new research results, with a wide range of features within the 5G-and-beyond framework. It provides a range of discussions of the major research challenges and achievements within this topic

Caracterização não-linear de agregados de antenas para aplicações 5G

The present mobile scenario demands are stretching the existing telecom infrastructure to the limit. New technologies centred around antenna arrays and spatial multiplexing have been proposed to overcome the challenges imposed by these demands. This work overviews the mobile scenario, scrutinizing demands, presented solutions, challenges and the industry’s perspective of the Fifth Generation of mobile communications. From a careful analysis, the 5G’s most critical radio frequency hardware issues are detailed, and a long-term approach to address them is presented. On the short-term the work focuses on antenna characterization, because antennas are a central part of future wireless communications. Initially, basic antenna concepts are presented, then emphasis is given to microstrip antennas, going through all the steps of designing, optimizing and measuring a rectangular microstrip antenna and an eight element linear antenna array for 5.67GHz. Array features such as scanning and source synthesis are also explored. Finally, the impact of signal nonlinear distortion on the antenna array pattern is studied, aiming to expand state-of-the-art knowledge on how signal nonlinear distortion can limit spatial multiplexing. A theoretical model of the phenomenon is proposed and validated both by electromagnetic simulation and measurements.As crescentes exigências das redes móveis estão a levar a infraestrutura de telecomunicações ao seu limite. Novas tecnologias centradas em agregados de antenas e multiplexagem espacial têm sido propostas para ultrapassar os desafios impostos por tais exigências. Este trabalho apresenta uma visão abrangente das redes móveis atuais, escrutinando as suas exigências, as soluções apresentadas, os desafios adjacentes, bem como a opinião da indústria. Os problemas mais crı́ticos do hardware de radio frequência para a quinta geração de redes móveis são apurados a partir de uma análise detalhada do cenário das redes sem fios, sendo apresentado um plano a longo prazo para abordar estas problemáticas. A curto prazo o trabalho foca-se em caracterização de antenas, visto que as antenas são um ponto central nas comunicações sem fios do futuro. Inicialmente são apresentados conceitos básicos sobre antenas, dando-se de seguida ênfase às antenas microstrip, sendo apresentado todo o processo de sı́ntese, otimização e caracterização de uma antena microstrip retangular e de um agregado de antenas linear de oito elementos com frequência de operação 5.67GHz. Neste âmbito, algumas propriedades dos agregados, como o varrimento angular do feixe eletromagnético e técnicas de sı́ntese de fonte eletromagnética, são também exploradas. Finalmente, apresenta-se um estudo sobre o impacto que a distorção não linear de sinal pode ter no diagrama de radiação do agregado de antenas. O objetivo é expandir os conhecimentos do estado-da-arte acerca das limitações que a distorção não linear pode impor na multiplexagem espacial. Neste sentido, um modelo teórico descritivo deste fenómeno é proposto e validado por simulação eletromagnética e por medições experimentais.Mestrado em Engenharia Eletrónica e Telecomunicaçõe