A Study Of Cooperative Spectrum Sharing Schemes For Internet Of Things Systems

The Internet of Things (IoT) has gained much attention in recent years with the massive increase in the number of connected devices. Cognitive Machine-to-Machine (CM2M) communications is a hot research topic in which a cognitive dimension allows M2M networks to overcome the challenges of spectrum scarcity, interference, and green requirements. In this paper, we propose a Generalized Cooperative Spectrum Sharing (GCSS) scheme for M2M communication. Cooperation extends the coverage of wireless networks as well as increasing their throughput while reducing the energy consumption of the connected low power devices. We study the outage performance of the proposed GCSS scheme for M2M system and derive exact expressions for the outage probability. We also analyze the effect of varying transmission powers on the performance of the system

Esquemas de retransmissão baseados no protocolo decodifica-e-encaminha em redes cognitivas do tipo underlay

Orientador: José Cândido Silveira Santos FilhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: O conceito de compartilhamento de espectro do tipo underlay tem sido proposto como uma técnica promissora para contornar o problema da escassez e da subutilização do espectro, permitindo que usuários não licenciados, chamados de usuários secundários, possam acessar simultaneamente uma banda licenciada, alocada aos usuários primários, desde que o nível de interferência sobre os mesmos seja mantido abaixo de um dado limiar aceitável. Entretanto, isso implica que a potência de transmissão na rede secundária deve ser restringida, comprometendo assim a confiabilidade e a cobertura da comunicação. A fim de contornar esse problema, técnicas de retransmissão cooperativa, as quais proveem um novo tipo de diversidade espacial, podem ser exploradas como um meio eficaz para melhorar o desempenho da rede secundária. De fato, a utilização conjunta de ambas as técnicas ¿ compartilhamento de espectro do tipo underlay e retransmissão cooperativa ¿ em redes cooperativas e cognitivas tem recebido especial atenção, já que a eficiência espectral do sistema e o desempenho da rede secundária podem ser melhorados significativamente. Esta tese apresenta quatro contribuições principais na referida área. Em particular, estuda-se o efeito conjunto de duas restrições de potência importantes sobre o desempenho de outage de redes cooperativas e cognitivas, especificamente, o nível máximo de potência interferente tolerada pelo receptor primário e o valor máximo de potência transmitida nos usuários secundários. Foca-se em esquemas de retransmissão baseados no protocolo decodifica-e-encaminha, abordando cenários em que o enlace direto entre fonte e destino está disponível para transmitir informação útil. Como uma primeira contribuição, analisa-se o desempenho de dois esquemas baseados no protocolo de retransmissão half-duplex incremental, os quais exploram a diversidade espacial dos enlaces diretos em redes cooperativas e cognitivas multiusuário. A segunda contribuição investiga o impacto de estimativas desatualizadas do canal sobre o mecanismo de seleção de destino para um desses esquemas anteriores, focando-se apenas no aspecto cooperativo da rede, ou seja, desconsiderando-se o uso de compartilhamento espectral. A terceira contribuição estuda o desempenho de redes cooperativas e cognitivas baseadas no modo full-duplex. Para esse cenário, avalia-se o impacto tanto da autointerferência residual, que é inerente ao modo full-duplex, bem como das restrições de potência que caracterizam o compartilhamento de espectro do tipo underlay. Como contribuição final, motivada pelo compromisso entre a perda de eficiência espectral e o problema da autointerferência residual, próprios dos modos half-duplex e full-duplex, respectivamente, propõe-se e analisa-se um esquema de transmissão adaptativo para redes cooperativas e cognitivas, através do qual, antes de cada processo de comunicação, um dos seguintes modos de transmissão é selecionado: retransmissão half-duplex, retransmissão full-duplex ou transmissão direta. Para todos os cenários considerados, expressões analíticas exatas para a probabilidade de outage são obtidas. Adicionalmente, uma análise assintótica é realizada a fim de caracterizar a ordem de diversidade e o comportamento de outage da rede secundária no regime assintótico de alta relação sinal-ruído. Simulações de Monte Carlo validam os resultados analíticos apresentadosAbstract: Underlay spectrum sharing has been proposed as a promising technique to alleviate the problem of spectrum scarcity and underutilization, by enabling secondary (unlicensed) users to concurrently access a licensed band, provided that the resulting interference on the primary (licensed) users remains below a given acceptable level. However, such a technique implies that the transmit power at the secondary network must be constrained, thereby compromising the communication reliability and coverage. To counteract this, cooperative relaying techniques, which provide a new form of spatial diversity, can be exploited as an effective means to boost the performance of the secondary network. Indeed, the joint use of both techniques¿underlay spectrum sharing and cooperative relaying¿in cognitive relaying networks has drawn special attention, since the overall spectral efficiency and the secondary-network performance can be significantly improved. This dissertation comprises four main contributions in this field. In particular, we examine the combined effect of two crucial power constraints on the outage performance of cognitive relaying networks, namely, the maximum tolerable interference power at the primary receiver and the maximum transmit power at the secondary users. We focus on relaying schemes operating under the decode-and-forward protocol, for scenarios in which the direct link between source and destination is available to convey useful information. As a first contribution, we analyze the performance of two incremental half-duplex relaying schemes, which exploit the spatial diversity of the direct links in a multiuser scenario. Our second contribution investigates the impact of outdated channel estimates on the destination-scheduling mechanism of one of those incremental schemes, from the perspective of a cooperative network only, that is, in the absence of spectrum sharing. The third contribution addresses cognitive full-duplex relaying networks. More specifically, we assess the system performance as a function of both the residual self-interference, which is inherent to the full-duplex relaying mode, and the underlay spectrum-sharing power constraints. As a final contribution, driven by the tradeoff between the spectral-efficiency loss and the residual self-interference problem, intrinsic to the half- and full-duplex relaying modes, respectively, we propose and analyze an adaptive transmission scheme whereby, before each communication process, one out of the following transmission modes is selected: half-duplex relaying, full-duplex relaying, or direct transmission. For all the considered scenarios, exact analytical expressions for the outage probability are derived. In addition, an asymptotic analysis is performed to obtain further insights on the diversity order and outage behavior of the secondary network at the high signal-to-noise ratio regime. Monte Carlo simulations corroborate the accuracy of the presented mathematical analysisDoutoradoTelecomunicações e TelemáticaDoutor em Engenharia ElétricaCAPE

Time-slot based architecture for power beam-assisted relay techniques in CR-WSNs with transceiver hardware inadequacies

Over the past two decades, numerous research projects have concentrated on cognitive radio wireless sensor networks (CR-WSNs) and their benefits. To tackle the problem of energy and spectrum shortfall in CR-WSNs, this research proposes an underpinning decode-&-forward (DF) relaying technique. Using the suggested time-slot architecture (TSA), this technique harvests energy from a multi-antenna power beam (PB) and delivers source information to the target utilizing energy-constrained secondary source and relay nodes. The study considers three proposed relay selection schemes: enhanced hybrid partial relay selection (E-HPRS), conventional opportunistic relay selection (C-ORS), and leading opportunistic relay selection (L-ORS). We present evidence for the sustainability of the suggested methods by examining the outage probability (OP) and throughput (TPT) under multiple primary users (PUs). These systems leverage time switching (TS) receiver design to increase end-to-end performance while taking into account the maximum interference constraint and transceiver hardware inadequacies. In order to assess the efficacy of the proposed methods, we derive the exact and asymptotic closed-form equations for OP and TPT & develop an understanding to learn how they affect the overall performance all across the Rayleigh fading channel. The results show that OP of the L-ORS protocol is 16% better than C-ORS and 75% better than E-HPRS in terms of transmitting SNR. The OP of L-ORS is 30% better than C-ORS and 55% better than E-HPRS in terms of hardware inadequacies at the destination. The L-ORS technique outperforms C-ORS and E-HPRS in terms of TPT by 4% and 11%, respectively

Hybrid satellite-terrestrial relay network: proposed model and application of power splitting multiple access

The development of hybrid satellite-terrestrial relay networks (HSTRNs) is one of the driving forces for revolutionizing satellite communications in the modern era. Although there are many unique features of conventional satellite networks, their evolution pace is much slower than the terrestrial wireless networks. As a result, it is becoming more important to use HSTRNs for the seamless integration of terrestrial cellular and satellite communications. With this intent, this paper provides a comprehensive performance evaluation of HSTRNs employing non-orthogonal multiple access technique. The terrestrial relay is considered to be wireless-powered and harvests energy from the radio signal of the satellite. For the sake of comparison, both amplify-and-forward (AF) and decode-and-forward (DF) relaying protocols are considered. Subsequently, the closed-form expressions of outage probabilities and ergodic capacities are derived for each relaying protocol. Extensive simulations are performed to verify the accuracy of the obtained closed-form expressions. The results provided in this work characterize the outage and capacity performance of such a HSTRN.publishe

New Approaches Using Cognitive Radio in Green Networking

The green networks are energy-efficient network architectures and we consider them as the basis of the wireless communication optimizing energy usage. Indeed, future communication technologies are moving in this direction, meaning that they will be less energy-intensive and, in some cases, even energy self-sufficient. Specifically, cognitive radio (CR) networks, cooperative relay networks, and non-orthogonal multiple access (NOMA) techniques have been considered as effective means to facilitate energy harvesting (EH) and a power spectrum allocation for the minimization of total transmit power, hence, making the wireless communication greener. The dissertation consists of three research sections corresponding to the aims. The first aim deals with an radio frequency (RF) wireless energy transfer model for D2D systems. In order to harvest more energy, a multiple-antenna base station and a power beacon are adopted for the D2D transmission network. We derive expressions outage probability in closed-forms. Further, independent simulations are used to validate the exactness of the theoretical expressions. In the second aim, new cooperative system models are proposed and studied. To reach the second aim, the secondary source acts as a relay and employs Amplify and Forward (AF) mode to serve distant NOMA users under a given interference constraint. To provide a detailed examination of the system performance metrics, we derived closed-form formulas for the outage probability and average throughput of the multi-users in the presence of interference constraints. In the last aim of the dissertation, we designed a new system model for a hybrid satellite-terrestrial cognitive network (HSTCN) relying on NOMA interconnecting a satellite and multiple terrestrial nodes. Reliability and security of transmission were studied to minimize the total transmit power. To reach the third aim, we examined the following performance factors: outage probability, hardware impairment, intercept probability, and average throughput. The novel closed-forms expressions of these performance factors are derived. The last but not at least, we simulated the new HSTCN system model. The achieved results figured that the new proposed approaches make it possible to take into account service quality requirements and are applicable in future green networking.Zelené sítě jsou energeticky efektivní síťové architektury a považujeme je za základ bezdrátové komunikace optimalizující spotřebu energie. Tímto směrem se ubírají budoucí komunikační technologie, což znamená, že budou méně energeticky náročné a v některých případech dokonce energeticky soběstačné. Kognitivní rádiové (CR) sítě, kooperativní relay sítě a neortogonální vícenásobné přístupové (NOMA) techniky jsou považovány za účinný prostředek k usnadnění získávání energie (EH) a přidělování výkonového spektra pro minimalizaci celkového vysílacího výkonu, díky čemuž je bezdrátová komunikace zelenější. Disertační práce se skládá ze tří výzkumných částí odpovídajících cílům. První cíl se zabývá modelem bezdrátového přenosu radiofrekvenční (RF) energie pro systémy D2D. Aby bylo možné získat více energie, jsou pro přenosovou D2D síť použity základnové stanice s více anténami a napájecím radiomajákem. Pro navržený model jsou odvozeny pravděpodobnosti výpadků, kdy tyto výrazy jsou v uzavřené formě. Dále jsou k ověření platnosti získaných teoretických výrazů použity nezávislé simulace. Ve druhém cíli jsou navrženy a zkoumány nové modely kooperativního systému. Aby bylo dosaženo druhého cíle, sekundární zdroj funguje jako relay uzel a využívá režim AF (Amplify and Forward), který slouží vzdáleným NOMA uživatelům za specifických interferenčních podmínek. Abychom poskytli podrobné zhodnocení výkonnostních metrik systému, odvodili jsme vztahy v uzavřené formě pro pravděpodobnost výpadků a průměrnou propustnost více uživatelů za přítomnosti interferenčních omezení. V posledním cíli disertační práce jsme navrhli nový systémový model pro hybridní satelitně-terestrickou kognitivní síť (HSTCN) založenou na neortogonálním vícenásobném přístupu (NOMA) propojující satelit a více terestrických uzlů. Zkoumána byla spolehlivost a zabezpečení přenosu s důrazem na minimalizaci celkového vysílacího výkonu. Pro dosažení třetího cíle jsme zkoumali následující výkonnostní faktory: pravděpodobnost výpadku, poškození hardwaru, pravděpodobnost zachycení a průměrnou propustnost. Pro tyto výkonnostní faktory jsou odvozeny v uzavřených formách nové výrazy. V neposlední řadě jsme rovněž simulovali nový systémový HSTCN model. Dosažené výsledky potvrdily, že nově navržené přístupy umožňují zohledňovat požadavky na kvalitu služeb a jsou použitelné v budoucích zelených sítích.440 - Katedra telekomunikační technikyvyhově

Outage analysis of the power splitting based underlay cooperative cognitive radio networks

In the present paper, we investigate the performance of the simultaneous wireless information and power transfer (SWIPT) based cooperative cognitive radio networks (CCRNs). In particular, the outage probability is derived in the closed-form expressions under the opportunistic partial relay selection. Different from the conventional CRNs in which the transmit power of the secondary transmitters count merely on the aggregate interference measured on the primary networks, the transmit power of the SWIPT-enabled transmitters is also constrained by the harvested energy. As a result, the mathematical framework involves more correlated random variables and, thus, is of higher complexity. Monte Carlo simulations are given to corroborate the accuracy of the mathematical analysis and to shed light on the behavior of the OP with respect to several important parameters, e.g., the transmit power and the number of relays. Our findings illustrate that increasing the transmit power and/or the number of relays is beneficial for the outage probability.Web of Science2122art. no. 765