105 research outputs found
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
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 cientÃfica 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 cientÃfica na área da saúde, a fim de contribuir para a formação profissional da equipe de saúde. Contem treinamento para a aquisição de conhecimento cientÃfico, 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 cientÃfica na Internet e em Bases de Dados Bibliográficas.Versão 1Organização Pan-Americana da Saúde - OPA
Metodologia cientÃfica II
O presente capÃtulo contempla o estudo da Metodologia CientÃfica. Apresenta um resumo das etapas de construção de projetos acadêmicos e tipos de estudos cientÃficos. Ressalta a importância da leitura especializada, estimulando o raciocÃnio crÃtico para a interpretação do conhecimento cientÃfico 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 clÃnicos, favorecendo a tomada de decisão segura, responsável e consciente.
Apresenta orientação resumida sobre a redação cientÃfica, permitindo aprendizagem autônoma e o desenvolvimento de Trabalho de Conclusão de Curso (TCC). Contem os seguintes tópicos: Metodologia CientÃfica; Leitura crÃtica e redação cientÃfica; Tipos de estudos cientÃficos; 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
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