1,721,019 research outputs found
Scheduling in Partially Buffered Crossbar Switches
No full textIntensive studies have been conducted to identify the most suitable architecture for high-performance packet switches. These architectures can be classified by queuing schemes, scheduling algorithms and switching fabric structures. The crossbar based switching fabric has been widely agreed to be the most suitable one, for its low cost, scalability and native multicast support. Large numbers of commercial implementations and literature studies have been conducted on the unbuffered crossbar switching architecture. Due to the requirement of the centralized scheduler, scheduling algorithms in the unbuffered crossbar have generally high complexities. This leads to time-consuming scheduling processes that prevent the unbuffered architecture from scaling up with the modern optical link operating at the Gb/S range. The buffered crossbar architecture has been proposed to overcome the scheduling complexity bottleneck faced by the unbuffered crossbar. The introduction of cross point buffers decouples the centralized scheduling process and lowers the scheduling complexity. However, the drawback of the buffered crossbar lies in the fact that it requires expensive on-chip memories, being the size of the switch, limiting the scalability of the buffered crossbar architecture. To provide the scheduling simplicity brought by the buffered crossbar while having a cost close to the unbuffered one, the partially buffered crossbar architecture has been proposed. With the combination of advantages of the previous two architectures, the Partially Buffered Crossbar (PBC) is deemed as one of the competitive candidates for next-generation switching architectures. However, the previously proposed algorithms did not fully exploit its potential. In this thesis, we: i) propose a unicast scheduling algorithm that further pushes the performance of the PBC switch under various non-uniform traffic settings, while using as few as 2 internal buffers per output. ii) study the multicast traffic support by the partially buffered crossbar switch and come up with an effective multicast scheduling algorithm.Embedded SystemsMicroelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Hardware design and implementation of a network-on-chip based high performance crossbar switch Fabric
No full textHigh-performance routers have the task of transmitting traffic in between the nodes of the Internet, the network of networks that carries the vast amount of information among billions of users. The switch fabric is the key building block of every router, and various switch fabric architectures are used in the market products. The crossbar-based switch fabric architectures (both buffered and unbuffered) offer very high performances and are widely used for high-performance routers. However their cost grows quadratically with the input/output port count, since they require internal crosspoints (and buffers) for every input/output port pair. Recently, a functional-level design of two novel Network-on-Chip based switch fabric architectures was proposed, Unidirectional NoC (UDN) and Multidirectional NoC (MDN), as a replacement of the buffered crossbar switch fabric architecture. In this thesis, we propose the hardware design and implementation of the aforementioned architectures for the FPGA platform. We further improve the routing and scheduling algorithms of these architectures for feasible hardware design. The synthesis and simulations are carried out over a wide range of switch sizes and traffic scenarios. The simulation results are also validated on the FPGA platform, by generating pseudo-random destination addresses for the packets on LFSR based test modules. The results show that UDN outperforms MDN in terms of throughput, whereas MDN offers greater performance-cost ratio. Both architectures offer scalability, flexibility and high performance, confirming the ideas in the original proposal.Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Scheduling in high performance buffered crossbar switches
No full textHigh performance routers are the basic building blocks of the Internet. Most high performance routers built today use crossbars and a centralized scheduler. Due to their high scheduling complexity, crossbar-based routers are not scalable and cannot keep pace with the explosive growth of the Internet. This dissertation studies a slight variation to the crossbar, a buffered crossbar switching architecture. A scalable buffered crossbar switch design is proposed, using embedded unicast scheduling. Furthermore, an efficient buffered crossbar-based switching architecture is described for multicast traffic support as well as the integration of unicast and multicast traffic flows. Finally, a partially buffered crossbar switching architecture is proposed. This architecture is shown to exhibit high performance, comparable to that of fully buffered crossbars, and a low cost, comparable to that of unbuffered crossbars.Electrical Engineering, Mathematics and Computer Scienc
Reliable In-Vehicle FlexRay Network Scheduler Design
No full textFlexRay is the new generation in-vehicle network protocol that enable fast data rate, reliability and fault-tolerant. It is developed by BMW, DaimlerChrysler, Bosch, Philips and other semiconductor companies. Because of the rapid development of the automotive industry, the need for in-vehicle communication is growing beyond the capability of simple FlexRay network. The idea of switched FlexRay network emerges to adapt the needs of growing capacity. This thesis aims at solving the problems of schedulers design for both simple and switched in-vehicle networks using FlexRay protocol. This thesis presents the corresponding FlexRay protocol specifications and the real-time scheduling theory. Furthermore, the system schedulability and the optimizations of bus configuration are analyzed. Finally, we provide the scheduling algorithms for these two types of networks.TelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
On the Integration of Unicast and Multicast Cell Scheduling in Buffered Crossbar Switches
No full textInternet traffic is a mixture of unicast and multicast flows. Integrated schedulers capable of dealing with both traffic types have been designed mainly for Input Queued (IQ) buffer-less crossbar switches. Combined Input and crossbar queued (CICQ) switches, on the other hand, are known to have better performance than their buffer-less predecessors due to their potential in simplifying the scheduling and improving the switching performance. The design of integrated schedulers in CICQ switches has thus far been neglected. In this paper, we propose a novel CICQ architecture that supports both unicast and multicast traffic along with its appropriate scheduling. In particular, we propose an integrated round-robin-based scheduler that efficiently services both unicast and multicast traffic simultaneously. Our scheme, named multicast and unicast round robin scheduling (MURS), has been shown to outperform all existing schemes under various traffic patterns. Simulation results suggested that we can trade the size of the internal buffers for the number of input multicast queues. We further propose a hardware implementation of our algorithm for a 16 times 16 buffered crossbar switch. The implementation results suggest that MURS can run at 20 Gbps line rate and a clock cycle time of 2.8 ns, reaching an aggregate switching bandwidth of 320 Gbps.Microelectronics & Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc
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
Physical activity and insulin sensitivity: the RISC study
No full textOBJECTIVE—Physical activity is a modifiable risk factor for
type 2 diabetes, partly through its action on insulin sensitivity.
We report the relation between insulin sensitivity and physical
activity measured by accelerometry.
RESEARCH DESIGN AND METHODS—This is a cross-sec-
tional study of 346 men and 455 women, aged 30–60 years,
without cardiovascular disease and not treated by drugs for
diabetes, hypertension, dyslipidemia, or obesity. Participants
were recruited in 18 clinical centers from 13 European countries.
Insulin sensitivity was measured by hyperinsulinemic-euglyce-
mic clamp. Physical activity was recorded by accelerometry for
a median of 6 days. We studied the relationship of insulin
sensitivity with total activity (in counts per minute), percent of
time spent sedentary, percent of time in light activity, and activity
intensity (whether the participant recorded some vigorous or
some moderate activity).
RESULTS—In both men and women, total activity was associ-
ated with insulin sensitivity (P 0.0001). Time spent sedentary,
in light activity, and activity intensity was also associated with
insulin sensitivity (P 0.0004/0.01, 0.002/0.03, and 0.02/0.004,
respectively, for men/women) but lost significance once adjusted
for total activity. Adjustment for confounders such as adiposity
attenuated the relationship with total activity; there were no
interactions with confounders. Even in the 25% most sedentary
individuals, total activity was significantly associated with better
insulin sensitivity (P 0.0001).
CONCLUSIONS—Accumulated daily physical activity is a ma-
jor determinant of insulin sensitivity. Time spent sedentary, time
spent in light-activity, and bouts of moderate or vigorous activity
did not impact insulin sensitivity independently of total activit
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