1,721,061 research outputs found
A Very Fast Tags Polling Protocol for Single and Multiple Readers RFID Systems, and its Applications
No full textIn this paper, we present a very fast and simple protocol for polling tags in an RFID system formed by one or more readers, and a multitude of tags. Actually, the protocol is time-optimal for single reader systems, while being very fast for multiple readers systems. The main idea of the protocol described in this paper, is to associate a short and unique number (called “nickname” in the following) to each tag in the reader’s range, and by using such nicknames as the polling order. We first describe the single reader version of the protocol. For this version, the used nicknames are the integers 1,2,...,n1,2,...,n if the set of tags to be polled is formed by n tags. They can be seen as the time slot in which a tag has to communicate with the reader. We also provide a procedure to assign a nickname for a new tag, as well as a way to delete a tag from the polling order, while keeping the above consecutivity property about nicknames. When polled, the tags transmit a proper (usually short) message. Polling protocols, sometime with little changes, sometime with no change, can be efficiently used for solving several practical problems related to the use of RFID systems. Some of the most prominent ones, and those considered in this paper, are the problems of exactly determine missing tags, the collection of information associated to the tags, the probabilistic determination of missing tags (useful for raising a warning), and the determination of the presence of cloned tags, again for raising a proper warning. We formally show that the protocol is time-optimal. Besides, the protocol is privacy preserving since tags ID’s are never transmitted during the polling procedure.
In the protocol version for large, multireader RFID systems, we take an approach completely different from that used so far for any multireader protocol. Up to now, in the proposed protocols for this and related problems, first readers are scheduled so that those with overlapping ranges never operate at the same time. Then, single reader protocol for each so scheduled reader are applied. Here, we schedule the tags instead of the readers so that tags whose transmission can be received by a common reader, never operate at the same time. Then, we show that our polling protocol for single reader systems can be effectively used along with such a tags scheduling strategy, in multireader systems. The time performance improvement of our protocol over the known ones for multireader systems is very large, going from two to seven times, as shown by a simulation experiment we set up, and whose results are also presented
MIMO-OFDM spatial multiplexing technique implementation for GNU radio
No full textMultiple-Input Multiple-Output (MIMO) is a wireless technology allowing a significant increasing of the throughput without the extension of the bandwidth but by means of the use of multiple antennas both in transmission and reception. Currently, Orthogonal Frequency Division Multiplexing (OFDM) is used in conjuction with MIMO to achieve better performance. With OFDM, instead of a single carrier, the main signal is split in a sub-set of independently modulated signals on orthogonal sub-carriers. In this paper, we provide a description of our MIMONet SDR platform for network-level exploitation of MIMO technology. We present the implementation of our OFDM transceiver, developed following the structure of IEEE 802.11n standard and implementing one of the most powerful MIMO technique: spatial multiplexing. In this technique, two (or more) different data streams are simultaneously transmitted over two (or more) antennas. Starting from the original GNU Radio code, we modified and added blocks to achieve a complete implementation of MIMO-OFDM spatial multiplexing. We added some features, such as the concatenation of Forward Error Correction (FEC) in the packet construction, and the use of pilot sub-carriers for channel estimation. We also developed a new synchronization algorithm derived by extending the Van de Beek algorithm to the MIMO setting. We build the framework of the standard IEEE 802.11n. In particular, we put all the preambles needed for synchronization and channel estimation. We have also designed and implemented a fine grained signal-to-noise ratio (SNR) estimation, bit error rate (BER) and packet error rate (PER) computations, that allow us to evaluate the channel conditions and validate performance of the software implementation
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
A novel protocol to evaluate ankle movements during reaching tasks using pediAnklebot
No full textThe aim of the study is to design a novel protocol to characterize the ankle movements during dorsal and plantar flexion reaching tasks using the pediAnklebot. Five healthy children were instructed to control a pointer and hit targets appearing on the monitor, by moving their ankle alternatively up and down. The protocol consisted of 60 targets, 30 up and 30 down, reachable via dorsiflexion and plantarflexion movements, respectively. Ankle angular displacements and torques were gathered by encoders and load cells embedded in the robot. Ankle motor performance was evaluated by means of kinematic, submovements and dynamic indices. Results suggest that (i) plantarflexion movements are faster and more accurate than the dorsiflexion ones, but children are able to perform with a higher level of smoothness the latter ones; (ii) children are able to stop the ankle movement more easily at the end of dorsiflexion rather than plantarflexion; (iii) the central nervous system plans plantarflexion and dorsiflexion movements with the same efficiency; (iv) children apply different torque levels during the two motor tasks and they cannot balance the inversion and eversion moments during dorsiflexion. These findings provide an important starting point for the assessment of a reference baseline of motor indices for the ankle joint
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