Diversity, Coding, and Multiplexing Trade-Off of Network-Coded Cooperative Wireless Networks

In this paper, we study the performance of network-coded cooperative diversity systems with practical communication constraints. More specifically, we investigate the interplay between diversity, coding, and multiplexing gain when the relay nodes do not act as dedicated repeaters, which only forward data packets transmitted by the sources, but they attempt to pursue their own interest by forwarding packets which contain a network-coded version of received and their own data. We provide a very accurate analysis of the Average Bit Error Probability (ABEP) for two network topologies with three and four nodes, when practical communication constraints, i.e., erroneous decoding at the relays and fading over all the wireless links, are taken into account. Furthermore, diversity and coding gain are studied, and advantages and disadvantages of cooperation and binary Network Coding (NC) are highlighted. Our results show that the throughput increase introduced by NC is offset by a loss of diversity and coding gain. It is shown that there is neither a coding nor a diversity gain for the source node when the relays forward a network-coded version of received and their own data. Compared to other results available in the literature, the conclusion is that binary NC seems to be more useful when the relay nodes act only on behalf of the source nodes, and do not mix their own packets to the received ones. Analytical derivation and findings are substantiated through extensive Monte Carlo simulations.Comment: IEEE International Conference on Communications (ICC), 2012. Accepted for publication and oral presentatio

A Comprehensive Framework for Performance Analysis of Cooperative Multi-Hop Wireless Systems over Log-Normal Fading Channels

International audienceIn this paper, we propose a comprehensive framework for performance analysis of multi–hop multi–branch wireless communication systems over Log–Normal fading channels. The framework allows to estimate the performance of Amplify and Forward (AF) relay methods for both Channel State Information (CSI–) assisted relays, and fixed–gain relays. In particular, the contribution of this paper is twofold: i) first of all, by relying on the Gauss Quadrature Rule (GQR) representation of the Moment Generation Function (MGF) for a Log–Normal distribution, we develop accurate formulas for important performance indexes whose accuracy can be estimated a priori and just depends on GQR numerical integration errors; ii) then, in order to simplify the computational burden of the former framework for some system setups, we propose various approximations, which are based on the Improved Schwartz–Yeh (I–SY) method. We show with numerical and simulation results that the proposed approximations provide a good trade–off between accuracy and complexity for both Selection Combining (SC) and Maximal Ratio Combining (MRC) cooperative diversity methods

Closed-Form Error Probability of Network-Coded Cooperative Wireless Networks with Channel-Aware Detectors

International audienceIn this paper, we propose a simple analytical methodology to study the performance of multi-source multi-relay cooperative wireless networks with network coding at the relay nodes and Maximum-Likelihood (ML-) optimum channel-aware detectors at the destination. Channel-aware detectors are a broad class of receivers that account for possible decoding errors at the relays, and, thus, are inherently designed to mitigate the effect of erroneous forwarded and network-coded data. In spite of the analytical complexity of the problem at hand, the proposed framework turns out to be simple enough yet accurate and insightful to understand the behavior of the system, and, in particular, to capture advantages and disadvantages of various network codes and the impact of error propagation on their performance. It is shown that, with the help of cooperation, some network codes are inherently more robust to decoding errors at the relays, while others better exploit the inherent spatial diversity and redundancy provided by cooperative networking. Finally, theory and simulation highlight that the relative advantage of a network code with respect to the others might be different with and without decoding errors at the relays

Chapter Flexible Network Codes Design for Cooperative Diversity

Image processin

On the Diversity Order and Coding Gain of Multi-Source Multi-Relay Cooperative Wireless Networks with Binary Network Coding

In this paper, a multi-source multi-relay cooperative wireless network with binary modulation and binary network coding is studied. The system model encompasses: i) a demodulate-and-forward protocol at the relays, where the received packets are forwarded regardless of their reliability; and ii) a maximum-likelihood optimum demodulator at the destination, which accounts for possible demodulations errors at the relays. An asymptotically-tight and closed-form expression of the end-to-end error probability is derived, which clearly showcases diversity order and coding gain of each source. Unlike other papers available in the literature, the proposed framework has three main distinguishable features: i) it is useful for general network topologies and arbitrary binary encoding vectors; ii) it shows how network code and two-hop forwarding protocol affect diversity order and coding gain; and ii) it accounts for realistic fading channels and demodulation errors at the relays. The framework provides three main conclusions: i) each source achieves a diversity order equal to the separation vector of the network code; ii) the coding gain of each source decreases with the number of mixed packets at the relays; and iii) if the destination cannot take into account demodulation errors at the relays, it loses approximately half of the diversity order.Comment: 35 pages, submitted as a Journal Pape

Flexible Network Codes Design for Cooperative Diversity

ISBN 978-953-307-183-1In this book chapter, we have proposed UEP coding theory for the flexible design of network codes for multi-source multi-relay cooperative networks. The main advantage of the proposed method with respect to state-of-the-art solutions is the possibility of assigning the diversity gain of each user individually. This offers a great flexibility for the efficient design of network codes for cooperative networks, as energy consumption, performance, number of time-slots required to achieve the desired diversity gain, and complexity at the relay nodes for performing NC can be traded-off by taking into account the specific and actual needs of each source, and without the constraint of over-engineering (e.g., working in a larger Galois field or using more time-slots than actually required) the system according to the needs of the source requesting the highest diversity gain

Metodologia científica I

O presente conteúdo apresenta orientações para a elaboração da Pergunta de Pesquisa, contribuindo para o desenvolvimento de projetos acadêmicos. Contempla a relevância da leitura e busca de informação científica na área da saúde, a fim de contribuir para a formação profissional da equipe de saúde. Contem treinamento para a aquisição de conhecimento científico, por meio da adoção de métodos de busca, favorecendo a capacitação profissional e pessoal. Com vistas a contribuir para a aprendizagem autônoma dos profissionais de saúde, este conteúdo contempla os seguintes temas, abordados de forma geral: Aquisição de informação científica na Internet e em Bases de Dados Bibliográficas.Versão 1Organização Pan-Americana da Saúde - OPA

Metodologia científica II

O presente capítulo contempla o estudo da Metodologia Científica. Apresenta um resumo das etapas de construção de projetos acadêmicos e tipos de estudos científicos. Ressalta a importância da leitura especializada, estimulando o raciocínio crítico para a interpretação do conhecimento científico na área da saúde. Compreende-se que esta prática, adotada de forma periódica, contribui para a capacitação do profissional de saúde, por meio do uso protocolos clínicos, favorecendo a tomada de decisão segura, responsável e consciente. Apresenta orientação resumida sobre a redação científica, permitindo aprendizagem autônoma e o desenvolvimento de Trabalho de Conclusão de Curso (TCC). Contem os seguintes tópicos: Metodologia Científica; Leitura crítica e redação científica; Tipos de estudos científicos; elaboração do Trabalho de Conclusão de Curso, considerando-se as etapas metodológicas.Versão 1Organização Pan-Americana da Saúde - OPA

Distributed Localization Algorithms for Wireless Sensor Networks: From Design Methodology to Experimental Validation

Recent advances in the technology of wireless electronic devices have made possible to build ad–hoc Wireless Sensor Networks (WSNs) using inexpensive nodes, consisting of low–power processors, a modest amount of memory, and simple wireless transceivers. Over the last years, many novel applications have been envisaged for distributed WSNs in the area of monitoring, communication, and control. Sensing and controlling the environment by using many embedded devices forming a WSN often require the measured physical parameters to be associated with the position of the sensing device. As a consequence, one of the key enabling and indispensable services in WSNs is localization (i.e., positioning). Moreover, the design of various components of the protocol stack (e.g., routing and Medium Access Control, MAC, algorithms) might take advantage of nodes’ location, thus resulting in WSNs with improved performance. However, typical protocol design methodologies have shown signiï¬cant limitations when applied to the ï¬eld of embedded systems, like WSNs. As a matter of fact, the layered nature of typical design approaches limits their practical usefulness for the design of WSNs, where any vertical information (like, e.g., the actual node’s position) should be efï¬ciently shared in such resource constrained devices. Among the proposed solutions to address this problem, we believe that the Platform–Based Design (PBD) approach Sangiovanni-Vincentelli (2002), which is a relatively new methodology for the design of embedded systems, is a very promising paradigm for the efï¬cient design of WSNs