4,725 research outputs found
Dispersive Fourier Transformation for Versatile Microwave Photonics Applications
Abstract: Dispersive Fourier transformation (DFT) maps the broadband spectrum of an ultrashort optical pulse into a time stretched waveform with its intensity profile mirroring the spectrum using chromatic dispersion. Owing to its capability of continuous pulse-by-pulse spectroscopic measurement and manipulation, DFT has become an emerging technique for ultrafast signal generation and processing, and high-throughput real-time measurements, where the speed of traditional optical instruments falls short. In this paper, the principle and implementation methods of DFT are first introduced and the recent development in employing DFT technique for widespread microwave photonics applications are presented, with emphasis on real-time spectroscopy, microwave arbitrary waveform generation, and microwave spectrum sensing. Finally, possible future research directions for DFT-based microwave photonics techniques are discussed as well
KERT: Automatic Extraction and Ranking of Topical Keyphrases from Content-Representative Document Titles
We introduce KERT (Keyphrase Extraction and Ranking by Topic), a framework
for topical keyphrase generation and ranking. By shifting from the
unigram-centric traditional methods of unsupervised keyphrase extraction to a
phrase-centric approach, we are able to directly compare and rank phrases of
different lengths. We construct a topical keyphrase ranking function which
implements the four criteria that represent high quality topical keyphrases
(coverage, purity, phraseness, and completeness). The effectiveness of our
approach is demonstrated on two collections of content-representative titles in
the domains of Computer Science and Physics.Comment: 9 page
Data-Driven 3D Placement of UAV Base Stations for Arbitrarily Distributed Crowds
In this paper, we consider an Unmanned Aerial Vehicle (UAV)-assisted cellular
system which consists of multiple UAV base stations (BSs) cooperating the
terrestrial BSs. In such a heterogeneous network, for cellular operators, the
problem is how to determine the appropriate number, locations, and altitudes of
UAV-BSs to improve the system sumrate as well as satisfy the demands of
arbitrarily flash crowds on data rates. We propose a data-driven 3D placement
of UAV-BSs for providing an effective placement result with a feasible
computational cost. The proposed algorithm searches for the appropriate number,
location, coverage, and altitude of each UAV-BS in the serving area with the
maximized system sumrate in polynomial time so as to guarantee the minimum data
rate requirement of UE. The simulation results show that the proposed approach
can improve system sumrate in comparison with the case without UAV-BSs.Comment: 6 pages, 3 figures, accepted by 2019 IEEE Global Communications
Conference: Wireless Communications (Globecom2019 WC
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