1,721,402 research outputs found
Adaptive Detection and Localization Exploiting the IEEE 802.11ad Standard
No full textIn this work, we exploit the sector level sweep of the IEEE 802.11ad communication standard to implement an opportunistic radar at mmWaves and derive an adaptive procedure for detecting multiple echoes and estimating their parameters (namely, amplitude, delay, and Doppler shift). The proposed detector/estimator extracts the prospective echoes oneby-one from the received signal, after removing the interference caused by the previously detected (stronger) reverberations from the environment. Examples are provided to assess the system performance, also in comparison with other detectors/estimators and the Cramér-Rao bounds on the localization accuracy. Results indicate that the proposed method is robust against the interference induced by the imperfect ambiguity function and can achieve a delay resolution approximately equal to the inverse of the signal bandwidth, corresponding to a range offset of about 17 cm. Instead, the Doppler resolution is inherently limited by the short duration of the data packet and, in the most favorable case, is approximately 3.26 KHz, corresponding to a relative radial velocity off-set of about 8.16 m/s for a wavelength of 5 mm
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
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
Detection and localization of multiple targets in IEEE 802.11ad networks
No full textIn this work we consider the IEEE 802.11ad communication standard operating at 60 GHz and exploit the echoes generated during the sector level sweep for target detection and localization. We propose a novel adaptive procedure that extracts the prospective echoes one-by-one from the received signal, after removing the interference caused by the previously detected (stronger) targets. The proposed detector/estimator is robust against the signal spillover and the near-far problem caused by the imperfect auto-correlation of the probing signal. Numerical examples are provided to validate the proposed solution
An Iterative Interference Cancellation Algorithm for Opportunistic Sensing in IEEE 802.11AD Networks
No full textIn this work, we study the problem of detecting multiple targets (echoes) and estimating their parameters by using the sector level sweep of the IEEE 802.11ad communication standard in order to realize an opportunistic radar at mmWaves. We derive an adaptive detector/estimator which extracts the prospective echoes one-by-one from the received signal, after removing the interference caused by the previously detected (stronger) targets. The numerical analysis indicates that the proposed solution can achieve detection and estimation performances close to those obtained in a single-target scenario
Joint Design of Surveillance Radar and MIMO Communication in Cluttered Environments
Full text linkIn this study, we consider a spectrum sharing architecture, wherein a multiple-input multiple-output communication system cooperatively coexists with a surveillance radar. The degrees of freedom for system design are the transmit powers of both systems, the receive linear filters used for pulse compression and interference mitigation at the radar, and the space-time communication codebook. The design criterion is the maximization of the mutual information between the input and output symbols of the communication system, subject to constraints aimed at safeguarding the radar performance. Unlike previous studies, we do not require any time-synchronization between the two systems, and we guarantee the radar performance on all of the range-azimuth cells of the patrolled region under signal-dependent (endogenous) and signal-independent (exogenous) interference. This leads to a non-convex problem, and an approximate solution is thus introduced using a block coordinate ascent method. A thorough analysis is provided to show the merits of the proposed approach and emphasize the inherent tradeoff among the achievable mutual information, the density of scatterers in the environment, and the number of protected radar cells
Energy efficient communication with radar spectrum sharing
No full textIn this work, we consider the joint design of a surveillance radar and a multiple-input multiple-output communication system sharing the same bandwidth. In this framework, we maximize the energy efficiency at the communication system (i.e., the amount of information reliably delivered per unit of consumed energy) under a constraint on the minimum signal-to-disturbance ratio for each inspected range-azimuth resolution cell of the radar. The transmit powers of both systems, the space-time linear communication codebook, and the radar receive filters are the degrees of freedom for joint system optimization. The block coordinate ascent method is used to find an approximate solution to this optimization problem, and a numerical example is provided to show the merits of the proposed design strategy
Dynamic programming techniques for sequential detection and tracking of moving targets in radar systems
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