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Analysis of challenge-response authentication with reconfigurable intelligent surfaces
Get PDFPhysical-layer authentication (PLA) mechanisms exploit
signals exchanged at the physical layer of communication
systems to confirm the sender of a received message. In this
paper, we propose a novel challenge-response PLA (CR-PLA)
mechanism for a cellular system that leverages the reconfigurability
property of a reconfigurable intelligent surface (RIS) (under
the control of the verifier) in an authentication mechanism. In
CR-PLA, the verifier base station (BS) sets a random RIS configuration,
which remains secret to the intruder, and then checks
that the resulting estimated channel is modified correspondingly.
In fact, for a message sent by an attacker in a different location
than the legitimate user equipment (UE), the BS will estimate a
different channel and the message will be rejected as fake. Such a
solution reduces the communication and computational overhead
with respect to higher-layer cryptographic authentication. We
derive the maximum a-posteriori attack when the attacker
observes a correlated channel and the reconfigurable intelligent
surface (RIS) has many elements, and the attacker transmits
to Bob either directly or through the RIS. Using a generalized
likelihood ratio test to test the authenticity at the base station
(BS), we derive approximate expressions of the false alarm
and misdetection probabilities when both the BS and the UE
have a single antenna each, while the RIS has a large number
of elements. We also evaluate the trade-off between security
and communication performance, since choosing a random RIS
configuration reduces the data rate. Moreover, we investigate
the impact of various parameters (e.g., the RIS randomness, the
number of RIS elements, and the operating signal-to-noise ratio)
on security and communication performance
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Bit error rate evaluation for orthogonal space-time block codes in the presence of channel estimation errors
Get PDFVariations on the Author
Get PDF“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
Get PDFWe 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
Analytical methods to approximate the error performance of LDPC codes in wired access networks
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