1,721,077 research outputs found
Solving Fractional Polynomial Problems by Polynomial Optimization Theory
Full text linkThis letter aims at introducing the framework of polynomial optimization theory to solve fractional polynomial problems (FPPs). Unlike other widely used optimization frameworks, the proposed one applies to a larger class of FPPs, not necessarily defined by concave and/or convex functions. An iterative algorithm that is provably convergent and enjoys asymptotic optimality properties is proposed. Numerical results are used to validate its accuracy in the nonasymptotic regime when applied to the energy efficiency maximization in multiuser multiple-input multiple-output communication systems
Secrecy energy efficiency maximization in dual-metasurface-aided wireless networks
Full text linkThis paper investigates the robust secure energy efficiency (SEE) maximization problem in a multiple-input single-output communication system enhanced by two reconfigurable metasurfaces in the presence of a single passive eavesdropper. One metasurface is placed in the near field of the transmit antenna array, forming a reconfigurable holographic beamforming structure. The second metasurface is placed in the environment between the transmitter and receiver, as a reconfigurable intelligent surface. The signal reaches the intended receivers both via a direct and through the two metasurfaces. In this context, we aim at maximizing the minimum SEE among all legitimate users under quality of service requirements, transmit power limitations, and reflection constraints. The resulting problem is non-convex, and we develop a novel algorithm based on alternating maximization, sequential fractional programming, and use of pricing techniques. Numerical results show that the proposed system architecture and radio resource allocation algorithms provide significant SEE gains over conventional alternatives
Opportunistic automotive radar using the IEEE 802.11ad standard
No full textIn this work, we focus on vehicular networks employing the IEEE 802.11ad standard and show the feasibility of an opportunistic radar system. The echo generated by the beacon transmitted during the sector level sweep of the beamforming protocol is exploited to perform target detection and range/velocity estimation. Two solutions, which differ in the amount of prior information on the transmitted waveform, are developed, and numerical results showing their detection and estimation performance are provided
Energy efficiency maximization in MIMO links aided by metasurfaces with global reflection constraints
Full text linkThis work develops two radio resource allocation algorithms to optimize the energy efficiency of a multiple-input multiple-output (MIMO) communication system where a metasurface is deployed near the transmit antenna array to create a reconfigurable holographic beamforming structure. The design involves jointly optimizing the transmit covariance matrix and the reflection coefficients of the reconfigurable holographic surface (RHS). Two methods are proposed for this joint optimization. In both approaches, the RHS matrix is optimized using sequential fractional programming. However, the transmit covariance matrix is optimized differently: the first method employs fractional programming, while the second method utilizes a search within a standard-compliant codebook. The two algorithms are compared, showing that the codebook-based method achieves performance with only a limited gap compared to the more complex sequential fractional programming algorithm. The analysis considers both a nearly-passive RHS and an active one equipped with analog amplifiers
A framework for globally optimal energy-efficient resource allocation in wireless networks
Full text linkState-of-the-art algorithms for energy-efficient power allocation in wireless networks are based on fractional programming theory, and allow to find the global maximum of the energy efficiency only in noise-limited scenarios. In interference-limited scenarios, several sub-optimal solutions have been proposed, but an efficient framework to globally maximize energy-efficient metrics is lacking. The goal of this work is to fill this gap by making use of fractional programming theory jointly with monotonic optimization. The resulting optimization framework is useful for at least two main reasons. First, it sheds light on the ultimate energy-efficiency performance of wireless networks. Second, it provides the means to benchmark the energy efficiency of state-of-the-art, but sub-optimal, solutions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Secrecy Energy Efficiency Maximization in RIS-Aided Wireless Networks with Statistical CSI
Full text linkThis work studies the problem of secrecy energy efficiency maximization in multi-user wireless networks aided by reconfigurable intelligent surfaces, in which an eavesdropper overhears the uplink communication. A provably convergent optimization algorithm is proposed which optimizes the user’s transmit power, metasurface reflection coefficients, and base station receive filters. The complexity of the proposed method is analyzed and numerical results are provided to show the performance of the proposed optimization method.
optimization algorithm is proposed which optimizes the user’s
transmit power, metasurface reflection coefficients, and base
station receive filters. The complexity of the proposed method
is analyzed and numerical results are provided to show the
performance of the proposed optimization method
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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