Simulator for the evaluation of the mean spectral efficiency of cellular networks in the presence of co-channel interference

Orientador: Celso de AlmeidaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Na próxima geração de redes celulares, a ICC (Interferência de Co-Canal ) constitui a causa principal para a degradação do desempenho, especialmente para os usuários na borda da célula, o que é um grande obstáculo para alcançar amplas áreas de cobertura e alta eficiência espectral. Neste trabalho, o desempenho do enlace reverso de uma rede celular em termos da eficiência espectral média e na presença de ICC é avaliado mediante uma simulação semi-analítica. Foram considerados dois cenários, canal AWGN(Additive White Gaussian Noise) e canal com desvanecimento plano do tipo Rayleigh, além de um modelo de propagação com perda de percurso exponencial. A avaliação é feita para fatores de reuso clássicos e modulações M-QAM (Multi-Level Quadrature Amplitude Modulation). Considera-se também uma estratégia de controle de potência e modulação adaptativa baseada na SIR (Signal-to-Noise Interference) e a BER (Bit Error Rate). Adicionalmente, é analisada a utilização de arranjo de antenas para diminuição dos efeitos da interferência e técnicas de diversidade para mitigação dos efeitos do desvanecimentoAbstract: In the next generation of wireless cellular networks, the CCI (Co-Channel Interference) constitutes the primary cause of performance degradation, specially for cell edge users, which is a big obstacle to attain wide area coverage and high spectral efficiency. In this work, the performance of the uplink of cellular networks in terms of the mean spectral efficiency is evaluated through a semi-analytical simulation, by considering the presence of CCI. It was considered two sceneries, an AWGN (Additive White Gaussian Noise) channel and a Rayleigh flat fading channel, as well as an exponential pathloss propagation model. The evaluation is done for classical reuse factors and M-QAM (Multi-Level Quadrature Amplitude Modulation) modulations. It is also considered a power control strategy and adaptive modulation based on the SIR (Signal-to-Noise Interference) and BER (Bit Error Rate). Besides, it is analyzed the utilization of an antenna array to reduce the interference effects and diversity techniques to mitigate fading effectsMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric

Strategic Deployment of Swarm of UAVs for Secure IoT Networks

Security provisioning for low-complex and constrained devices in the Internet of Things (IoT) is exacerbating the concerns for the design of future wireless networks. To unveil the full potential of the sixth generation (6G), it is becoming even more evident that security measurements should be considered at all layers of the network. This work aims to contribute in this direction by investigating the employment of unmanned aerial vehicles (UAVs) for providing secure transmissions in ground IoT networks. Toward this purpose, it is considered that a set of UAVs acting as aerial base stations provide secure connectivity between the network and multiple ground nodes. Then, the association of IoT nodes, the 3D positioning of the UAVs and the power allocation of the UAVs are obtained by leveraging game theoretic and convex optimization-based tools with the goal of improving the secrecy of the system. It is shown that the proposed framework obtains better and more efficient secrecy performance over an IoT network than state-of-the-art greedy algorithms for positioning and association

Multi UAV-enabled Distributed Sensing: Cooperation Orchestration and Detection Protocol

This paper proposes an unmanned aerial vehicle (UAV)-based distributed sensing framework that uses orthogonal frequency-division multiplexing (OFDM) waveforms to detect the position of a ground target, and UAVs operate in half-duplex mode. A spatial grid approach is proposed, where an specific area in the ground is divided into cells of equal size, then the radar cross-section (RCS) of each cell is jointly estimated by a network of dual-function UAVs. For this purpose, three estimation algorithms are proposed employing the maximum likelihood criterion, and digital beamforming is used for the local signal acquisition at the receive UAVs. It is also considered that the coordination, fusion of sensing data, and central estimation is performed at a certain UAV acting as a fusion center (FC). Monte Carlo simulations are performed to obtain the absolute estimation error of the proposed framework. The results show an improved accuracy and resolution by the proposed framework, if compared to a single monostatic UAV benchmark, due to the distributed approach among the UAVs. It is also evidenced that a reduced overhead is obtained when compared to a general compressive sensing (CS) approach

Impact of outdated channel estimates on a distributed link-selection scheme for AF relaying networks

We investigate the impact of outdated channel estimates on the outage performance of a distributed link-selection scheme recently proposed for variable-gain amplify-and-forward relaying networks. In this scheme, either the direct link or the relaying link is preselected before each transmission, based on a distributed mechanism. We begin by showing that an exact analysis is rather intricate, yielding a multifold integral-form solution. Motivated by this, we then derive a simple closed-form lower bound, which, importantly, proves to be a very tight approximation to the exact outage probability. We also assess the system diversity order via asymptotic analysis42185188COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESnão te

Esquemas espectralmente eficientes para redes com retransmissores do tipo amplifica-e-encaminha

Orientador: José Cândido Silveira Santos FilhoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: As comunicações cooperativas emergiram como uma técnica promissora para combater os efeitos prejudiciais do fenômeno de desvanecimento e ampliar a capacidade e a cobertura das futuras gerações de redes de comunicações sem fio. Essa técnica permite que diferentes nós da rede possam compartilhar suas antenas, emulando um sistema com múltiplas entradas e múltiplas saídas (MIMO) e proporcionando, assim, os benefícios de tal sistema a redes em que a implantação de múltiplas antenas resulta inviável. Nesse sentido, uma variedade de novos desafios tem surgido no intuito de explorar estrategias que permitam obter os ganhos plenos da comunicação cooperativa. Uma limitação importante a ser superada consiste na utilização do convencional modo de transmissão, half-duplex (HD), que acarreta uma perda na eficiência espectral devido à exigência de dois usos de canal por cada transmissão. A presente tese visa avançar nesse campo, contribuindo com técnicas espectralmente eficientes para redes cooperativas baseadas em retransmissores (relay), com ênfase no protocolo amplifica-e-encaminha (AF), o qual tem se mostrado atraente por sua simplicidade e facilidade de implementação. Em particular, duas estratégias são abordadas. A primeira delas contempla o modo de transmissão HD, cuja eficiência espectral é melhorada através da utilização de esquemas distribuídos de seleção de enlace. Tais esquemas evitam o uso contínuo do enlace de relay, pré-selecionando para cada transmissão aquele enlace --direto ou relaying-- que apresenta as melhores condições de canal. Além disso, a implementação distribuída conduz a uma economia na sobrecarga de realimentação decorrente dos requisitos de informação do estado do canal (CSI). Para essa primeira estratégia, são investigados os seguintes cenários: ambiente com múltiplos usuários, múltiplos relays e múltiplas antenas na fonte para ambos os tipos de AF, ou seja, de ganho variável e de ganho fixo; comparação de duas técnicas de seleção de relay para AF de ganho variável com múltiplos usuários e múltiplos relays; e o impacto da CSI desatualizada devido a variações no estado do canal entre o momento de seleção de enlace e o momento de transmissão, para um sistema clássico de três nós (fonte, relay e destino) com o protocolo AF de ganho variável. A análise é efetuada em termos da probabilidade de outage e da eficiência espectral. A segunda estratégia considera o uso do modo de transmissão full-duplex (FD), o qual tem ganhado força nos últimos anos devido aos avanços nos mecanismos para mitigar a autointerferência produzida em transceptores FD por conta da fuga de sinal do transmissor para o receptor. Particularmente, as contribuições se concentram no protocolo AF de ganho variável cujo enlace direto entre a fonte e o destino é também utilizado para transportar informação. Uma combinação por razão máxima (MRC) dos sinais vindos da fonte e do relay é realizada no receptor. Considera-se que o relay é afetado por interferência residual, produto das imperfeições nas técnicas de cancelamento de autointerferência. Em primeira instância, o desempenho em termos da probabilidade de outage é investigado para o modelo básico do sistema de três nós. Posteriormente, um esquema de seleção de modo adaptativo é proposto, que permite selecionar de forma oportunista, de acordo com as condições instantâneas do canal, uma das seguintes opções de transmissão: direta sem cooperação, cooperativa em modo HD com MRC no destino, e cooperativa em modo FD com MRC no destino. Nesse esquema, considera-se uma normalização de energia por bloco e a análise é efetuada em termos da probabilidade de outage e da eficiência energéticaAbstract: Cooperative Communications have emerged as a promising technique to combat the deleterious effects of fading and boost the capacity and coverage of next generation wireless communication networks. By allowing different nodes in the network to share their antennas, this technique emulates a distributed multiple-input multiple-output (MIMO) system, thus providing the benefits of such system to networks in which the deployment of multiple antennas may be unfeasible. In this sense, a variety of new challenges have arisen in order to exploit techniques that permit to achieve the full gains of cooperative relaying. A main limitation to be overcome is the use of the conventional half-duplex (HD) transmission mode, which produces a loss in the spectral efficiency due to the requirement of two channel uses per transmission. This thesis aims to advance in this field, by contributing with spectrally efficient techniques for cooperative relay networks based on the amplify-and-forward (AF) relaying protocol, which is attractive for its simplicity and ease of implementation. In particular, two strategies have been tackled. The first one addresses the HD transmission mode, in which the spectral efficiency is improved by using distributed link selection schemes. Such schemes avoid the continuous use of the relaying link by preselecting for transmission that link --direct or relaying-- with the best channel conditions. In addition, the distributed implementation saves feedback overhead due to the requirements of channel state information (CSI). For this strategy, the following issues are investigated: multiple users, multiple relays, and a multi-antenna source, for both types of AF, i.e., variable gain and fixed gain; two different relay selection techniques for variable-gain AF in the multiuser and multirelay scenario; and the impact of outdated CSI due to feedback delay over the classical three-node system (source, relay, and destination) for variable-gain AF. The analysis is addressed in terms of outage probability and spectral efficiency. The second strategy considers the use of the full-duplex (FD) transmission mode, which has gained increasing attention in the last years due to the recent advances in mechanisms for mitigating the self-interference in FD transceivers caused by the leakage of the transmitted signal into the receiver side. In particular, our contributions focus on the variable-gain AF protocol, in which the direct link between source and destination is also employed to convey information. Maximal-ratio combining (MRC) is carried out at the destination to merge the signals coming from source and relay. It is considered that the relay undergoes a residual self-interference due to imperfections in the cancellation techniques. First, the outage performance is investigated for the basic three-node system model. Then, an adaptive mode-selection scheme is proposed that opportunistically selects, according to the instantaneous channel conditions, among the following options: direct transmission with no cooperation, cooperative transmission in HD mode with MRC at the destination, and cooperative transmission in FD mode with MRC at the destination. In this scheme, an energy normalization per block is assumed, and the analysis is addressed in terms of outage performance and energy efficiencyDoutoradoTelecomunicações e TelemáticaDoutora em Engenharia ElétricaCAPE

An Adaptive Transmission Scheme For Amplify-and-forward Relaying Networks

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)In this paper, an adaptive scheme for amplify-andforward relaying networks is proposed, which selects a certain transmission mode for each communication process. Depending on the instantaneous channel conditions, one of the following modes is selected: direct transmission with no cooperation, cooperative transmission with half-duplex relaying and maximalratio combining at the destination, or cooperative transmission with full-duplex relaying and maximal-ratio combining at the destination. A three-node network is considered, containing a singleantenna source, a two-antenna relay that is able to implement full-duplex communication, and a single-antenna destination. Energy normalization per block is assumed, so that in those modes using cooperation, the system's transmission power is shared between source and relay. The performance analysis is provided in terms of outage probability and energy efficiency. We derive a tight approximate expression in closed form for the outage probability and an approximate expression in integral form for the mean energy consumption. The results show that our scheme outperforms all of transmission modes separately in terms of outage probability, while being more energy efficient than the cooperative transmission modes. In addition, the asymptotic analysis proves that the proposed scheme achieves full diversity order equal to 2, thus outperforming those schemes with direct transmission or full- duplex cooperation only.6516678Brazilian Ministry of Education (CAPES)Finnish Centre for International Mobility (CIMO)Tekes and Academy of Finland (AKA)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

A multi-armed bandit framework for efficient UAV-based cooperative jamming coverage

In this paper, the position control of multiple unmanned aerial vehicles, acting as cooperative jammers, is proposed to improve the security level of a legitimate ground transmission, where a precoder is designed to nullify the jamming signals at the legitimate receiver. In this scenario, the maximisation of the weighted secrecy coverage, which measures the efficiency of cooperative jamming over a confined region, is addressed by following a multi armed bandit-based algorithm. The results show that our proposal converges to the one obtained by exhaustive search, and it shows significant improvent over a projected gradient-descent benchmark, while offering a shorter running-time. It was also shown that the employment of only two UAVs joint with the precoder leads to significant advantages in terms of secrecy performance.</p