Esquemas distribuídos para seleção de múltiplas antenas em 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: A seleção de antena na transmissão tem sido apresentada como uma estratégia promissora para explorar os benefícios do uso de múltiplas antenas em sistemas de comunicações com retransmissores. No entanto, essa abordagem pode exigir um montante considerável de estimações de canal, transmissões de realimentação e atraso, dado que a sua implementação ótima e centralizada requer o monitoramento do estado do canal de todos os enlaces. Para aliviar essas deficiências, este trabalho propõe e analisa um conjunto de esquemas subótimos de seleção de antena na transmissão para sistemas com retransmissores do tipo amplifica-e-encaminha, os quais podem ser implementados de uma forma distribuída. Nos esquemas propostos, a antena é selecionada com base na informação local do estado de canal que está disponível na fonte, requerendo, portanto, um atraso e uma carga de realimentação pequenos e constantes. Tal abordagem é considerada em uso conjunto com diferentes técnicas, incluindo métodos de combinação de diversidade (combinação por máxima razão e combinação por seleção) no destino, protocolos de ganho fixo ou variável no relay, e transceptores com múltiplas antenas no relay. Além disso, para o caso particular em que o retransmissor tem ganho fixo e uma única antena, considera-se também o uso de um mecanismo de seleção de enlace na fonte. Para cada caso, o desempenho do sistema é avaliado em termos de probabilidade de outage, eficiência espectral e/ou vazão. O foco principal é direcionado à probabilidade de outage, para a qual são deduzidas expressões exatas e limitantes de desempenho. Uma análise assintótica é também efetuada para enriquecer a compreensão do comportamento do sistema quando operando sob alta relação sinal-ruído. Finalmente, como contribuição isolada, uma estratégia subótima e simples de alocação de potência é elaborada para um sistema com múltiplos retransmissores do tipo decodifica-e-encaminha, considerando-se enlaces com erros e codificação de fonte distribuídaAbstract: Transmit-antenna selection has been presented as a promising strategy for exploiting the benefits of multiple antennas in relaying communication systems. However, this approach may demand a considerable amount of channel estimations, feedback transmissions, and delay, since its optimal centralized implementation requires monitoring the channel state of all links. To alleviate those impairments, this work proposes and analyzes a set of suboptimal transmit-antenna selection schemes for amplify-and-forward relaying systems, which can be implemented in a distributed manner. In the proposed schemes, the antenna is selected based on the local channel-state information that is available at the source, thus requiring a low and constant delay/feedback overhead. Such an approach is considered along with different techniques, including diversity combining methods (maximal-ratio combining and selection combining) at the destination, fixed- and variable-gain protocols at the relay, and multi-antenna transceivers at the relay. A link-selection mechanism at the source is also considered for the special case of a single-antenna fixed-gain relay. For each case, the system performance is assessed in terms of outage probability, spectral efficiency, and/or throughput. The main focus is placed on the outage probability, for which exact or bound expressions are derived. An asymptotic analysis is also performed to provide further insights into the system behavior at high signal-to-noise ratio. Finally, as an isolated contribution, a simple suboptimal power allocation strategy is designed for a decode-and-forward multi-relay system with lossy intra-links and distributed source codingDoutoradoTelecomunicações e TelemáticaDoutora em Engenharia ElétricaCAPE

Multiterminal Source-Channel Coding

Cooperative communication is seen as a key concept to achieve ultra-reliable communication in upcoming fifth-generation mobile networks (5G). A promising cooperative communication concept is multiterminal source-channel coding, which attracted recent attention in the research community. This thesis lays theoretical foundations for understanding the performance of multiterminal source-channel codes in a vast variety of cooperative communication networks. To this end, we decouple the multiterminal source-channel code into a multiterminal source code and multiple point-to-point channel codes. This way, we are able to adjust the multiterminal source code to any cooperative communication network without modification of the channel codes. We analyse the performance in terms of the outage probability in two steps: at first, we evaluate the instantaneous performance of the multiterminal source-channel codes for fixed channel realizations; and secondly, we average the instantaneous performance over the fading process. Based on the performance analysis, we evaluate the performance of multiterminal source-channel codes in three cooperative communication networks, namely relay, wireless sensor, and multi-connectivity networks. For all three networks, we identify the corresponding multiterminal source code and analyse its performance by the rate region for binary memoryless sources. Based on the rate region, we derive the outage probability for additive white Gaussian noise channels with quasi-static Rayleigh fading. We find results for the exact outage probability in integral form and closed-form solutions for the asymptotic outage probability at high signal-to-noise ratio. The importance of our results is fourfold: (i) we give the ultimate performance limits of the cooperative communication networks under investigation; (ii) the optimality of practical schemes can be evaluated with respect to our results, (iii) our results are suitable for link-level abstraction which reduces complexity in network-level simulation; and (iv) our results demonstrate that all three cooperative communication networks are key technologies to enable 5G applications, such as device to device and machine to machine communications, internet of things, and internet of vehicles. In addition, we evaluate the performance improvement of multiterminal source-channel codes over other (non-)cooperative communications concepts in terms of the transmit power reduction given a certain outage probability level. Moreover, we compare our theoretical results to simulated frame-error-rates of practical coding schemes. Our results manifest the superiority of multiterminal source-channel codes over other (non-)cooperative communications concepts