1,306 research outputs found
Low latency via redundancy
Low latency is critical for interactive networked applications. But while we
know how to scale systems to increase capacity, reducing latency --- especially
the tail of the latency distribution --- can be much more difficult. In this
paper, we argue that the use of redundancy is an effective way to convert extra
capacity into reduced latency. By initiating redundant operations across
diverse resources and using the first result which completes, redundancy
improves a system's latency even under exceptional conditions. We study the
tradeoff with added system utilization, characterizing the situations in which
replicating all tasks reduces mean latency. We then demonstrate empirically
that replicating all operations can result in significant mean and tail latency
reduction in real-world systems including DNS queries, database servers, and
packet forwarding within networks
人格(パースナリティー)理論に就いて
The aim of this study was to evaluate the ability of new rubbery liners, used as a cervical increment, to relieve contraction stress and thereby reduce the formation of cervical gaps in class II composite restorations. The investigated liners were made of polyester-acrylate (PE(1), PE(2) or PE(3)) or silicone-acrylate (S), mixed with UDMA, without (A, B, C, D) or with HEMA (AH, BH, CH, DH). A silanized filler was added to the mixture, DH, to give composites with 20, 40, 60, and 70% (w/w) of filler (DHF20, DHF40, DHF60, DHF70, respectively). The presence and width of cervical gaps were determined using a light microscope. Statistical analysis showed that six of the 12 rubbery liners (AH-DH, DHF20-DHF40) significantly decreased gap formation in comparison with the control group. In addition, the polymerization shrinkage, flow, and strain capacity of these liners were measured and the influence of these factors on gap formation was examined. Two- and three-dimensional regression analyses showed significantly negative linear correlations between gap formation and strain capacity, and between gap formation and flow, and a significantly positive linear correlation between gap formation and shrinkage
On the infimum attained by a reflected L\'evy process
This paper considers a L\'evy-driven queue (i.e., a L\'evy process reflected
at 0), and focuses on the distribution of , that is, the minimal value
attained in an interval of length (where it is assumed that the queue is in
stationarity at the beginning of the interval). The first contribution is an
explicit characterization of this distribution, in terms of Laplace transforms,
for spectrally one-sided L\'evy processes (i.e., either only positive jumps or
only negative jumps). The second contribution concerns the asymptotics of
\prob{M(T_u)> u} (for different classes of functions and large);
here we have to distinguish between heavy-tailed and light-tailed scenarios
Measurement-Adaptive Cellular Random Access Protocols
This work considers a single-cell random access channel (RACH) in cellular
wireless networks. Communications over RACH take place when users try to
connect to a base station during a handover or when establishing a new
connection. Within the framework of Self-Organizing Networks (SONs), the system
should self- adapt to dynamically changing environments (channel fading,
mobility, etc.) without human intervention. For the performance improvement of
the RACH procedure, we aim here at maximizing throughput or alternatively
minimizing the user dropping rate. In the context of SON, we propose protocols
which exploit information from measurements and user reports in order to
estimate current values of the system unknowns and broadcast global
action-related values to all users. The protocols suggest an optimal pair of
user actions (transmission power and back-off probability) found by minimizing
the drift of a certain function. Numerical results illustrate considerable
benefits of the dropping rate, at a very low or even zero cost in power
expenditure and delay, as well as the fast adaptability of the protocols to
environment changes. Although the proposed protocol is designed to minimize
primarily the amount of discarded users per cell, our framework allows for
other variations (power or delay minimization) as well.Comment: 31 pages, 13 figures, 3 tables. Springer Wireless Networks 201
Decentralised Learning MACs for Collision-free Access in WLANs
By combining the features of CSMA and TDMA, fully decentralised WLAN MAC
schemes have recently been proposed that converge to collision-free schedules.
In this paper we describe a MAC with optimal long-run throughput that is almost
decentralised. We then design two \changed{schemes} that are practically
realisable, decentralised approximations of this optimal scheme and operate
with different amounts of sensing information. We achieve this by (1)
introducing learning algorithms that can substantially speed up convergence to
collision free operation; (2) developing a decentralised schedule length
adaptation scheme that provides long-run fair (uniform) access to the medium
while maintaining collision-free access for arbitrary numbers of stations
A L\'evy input fluid queue with input and workload regulation
We consider a queuing model with the workload evolving between consecutive
i.i.d.\ exponential timers according to a
spectrally positive L\'evy process that is reflected at zero, and
where the environment equals 0 or 1. When the exponential clock
ends, the workload, as well as the L\'evy input process, are modified; this
modification may depend on the current value of the workload, the maximum and
the minimum workload observed during the previous cycle, and the environment
of the L\'evy input process itself during the previous cycle. We analyse
the steady-state workload distribution for this model. The main theme of the
analysis is the systematic application of non-trivial functionals, derived
within the framework of fluctuation theory of L\'evy processes, to workload and
queuing models
Limiting genotype frequencies of Y-linked genes through bisexual branching processes with blind choice
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