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The canonical polyadic decomposition (CPD) is one of the most popular tensor-based analysis tools due to its usefulness in numerous fields of application. The Q-order CPD is parametrized by Q matrices also called factors which have to be recovered. The factors estimation is usually carried out by means of the alternating least squares (ALS) algorithm. In the context of multi-modal big data analysis, i.e., large order (Q) and dimensions, the ALS algorithm has two main drawbacks. Firstly, its convergence is generally slow and may fail, in particular for large values of Q, and secondly it is highly time consuming. In this paper, it is proved that a Q-order CPD of rank-R is equivalent to a train of Q 3order CPD(s) of rank-R. In other words, each tensor train (TT)-core admits a 3-order CPD of rank-R. Based on the structure of the TT-cores, a new dimensionality reduction and factor retrieval scheme is derived. The proposed method has a better robustness to noise with a smaller computational cost than the ALS algorithm.

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Over the last two decades, tensor‐based methods have received growing attention in the signal processing community. In this work, the authors proposed a comprehensive overview of tensor‐based models and methods for multisensor signal processing. They presented for instance the Tucker decomposition, the canonical polyadic decomposition, the tensor‐train decomposition (TTD), the structured TTD, including nested Tucker train, as well as the associated optimisation strategies. More precisely, they gave synthetic descriptions of state‐of‐the‐art estimators as the alternating least square (ALS) algorithm, the high‐order singular value decomposition (HOSVD), and of more advanced algorithms as the rectified ALS, the TT‐SVD/TT‐HSVD and the Joint dImensionally Reduction and Factor retrieval Estimator scheme. They illustrated the efficiency of the introduced methodological and algorithmic concepts in the context of three important and timely signal processing‐based applications: the direction‐of‐arrival estimation based on sensor arrays, multidimensional harmonic retrieval and multiple‐input–multiple‐output wireless communication systems.

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Resumo-Comunicações cooperativas surgiram como uma promissora solução para redes sem fio. Em particular, recentemente tem-se presenciado um interesse crescente em sistemas cooperativos do tipo amplifica-e-encaminha com seleção de relay. Por outro lado, a técnica de multiplexação por divisão em frequências ortogonais (OFDM) tem se mostrado ser uma tecnologia chave para os futuros sistemas de comunicação sem fio. Um dos principais problemas de sistemas OFDMé a grande variação da amplitude dos sinais transmitidos, o que pode levarà introdução de distorções não-lineares devidoà presença de amplificadores de potência não-lineares. Neste artigo, uma análise teórica da probabilidade de outage em um sistema OFDM do tipo AF com seleção de relayé desenvolvida, análise esta que leva em conta as distorções não-lineares introduzidas por um amplificador de potência não-linear. A análise mostra como os parâmetros do amplificador alteram a probabilidade de outage para diferentes niveis de SNR. Resultados numéricos são fornecidos para validar os resultados analíticos. Palavras-Chave-Amplifica-e-encaminha, seleção de relay, OFDM, amplificador de potência não-linear, probabilidade de outage.

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