Giuseppe Thadeu Freitas de Abreu

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Cooperative communications via distributed space-time codes has been recently proposed as a way to form virtual multiple-antennas that provide dramatic gains in slow fading wireless environments. In this paper, we consider the design of practical distributed space-time codes for wireless relay networks using the amplify-and-forward (AF) scheme, where each(More)
Wireless sensor networks (WSNs) are considered an adequate solutions for environmental monitoring and surveillance applications, where the physical presence of humans is impossible or costly. In the next future, it is foreseen that nodes will be part of a localization system, that will be able to estimate their locations, aiding the coordination for the(More)
We address the Primary User (PU) detection (spectrum sensing) problem, relevant to cognitive radio, from a finite random matrix theoretical (RMT) perspective. Specifically, we employ recently-derived closed-form and exact expressions for the distribution of the standard condition number (SCN) of uncorrelated and semi-correlated random dual central Wishart(More)
This contribution proposes and investigates a random access Medium Access Control (MAC) - Relay Selection Mechanism - for cluster-based geographic routing in Multi-hop Wireless Sensor Networks (WSNs). The intertwined MAC and network routing solution is derived in a cross-layer approach. The game-theoretical relay selection strategy (random multiple access)(More)
We survey the state-of-the-art on the Internet-of-Things (IoT) from a wireless communications point of view, as a result of the European FP7 project BUTLER which has its focus on pervasiveness, context-awareness and security for IoT. In particular, we describe the efforts to develop so-called (wireless) enabling technologies, aimed at circumventing the many(More)
In this paper Modified Orthogonal Space-Time Block Codes (MO-STBC) were designed as a way to improve the system performance in the presence of “non-quasi-static” fading channels. Loss of orthogonality in symbol decoding is mitigated by a very simple though efficient redesign of the conventional O-STBC encoding scheme. MO-STBC is proven by simulations to(More)
We consider the source and network localization problems, seeking to strengthen the relationship between the Weighted-Least-Square (WLS) and the Maximum-Likelihood (ML) solutions of these problems. To this end, we design an optimization algorithm for source and network localization under the principle that: a) the WLS and the ML objectives should be the(More)