15,706 research outputs found
A Centralized SDN Architecture for the 5G Cellular Network
In order to meet the increasing demands of high data rate and low latency
cellular broadband applications, plans are underway to roll out the Fifth
Generation (5G) cellular wireless system by the year 2020. This paper proposes
a novel method for adapting the Third Generation Partnership Project (3GPP)'s
5G architecture to the principles of Software Defined Networking (SDN). We
propose to have centralized network functions in the 5G network core to control
the network, end-to-end. This is achieved by relocating the control
functionality present in the 5G Radio Access Network (RAN) to the network core,
resulting in the conversion of the base station known as the gNB into a pure
data plane node. This brings about a significant reduction in signaling costs
between the RAN and the core network. It also results in improved system
performance. The merits of our proposal have been illustrated by evaluating the
Key Performance Indicators (KPIs) of the 5G network, such as network attach
(registration) time and handover time. We have also demonstrated improvements
in attach time and system throughput due to the use of centralized algorithms
for mobility management with the help of ns-3 simulations
Testing the bus guardian unit of the FTMP
Fault-tolerant multiprocessor (FTMP) operation is discussed. Fault-modeling in the bus guardian units (BGUs) is covered. Testing the BGU is discussed. A testing algorithm is proposed
Optical Spectroscopy of Type Ia Supernovae
We present 432 low-dispersion optical spectra of 32 Type Ia supernovae (SNe
Ia) that also have well-calibrated light curves. The coverage ranges from 6
epochs to 36 epochs of spectroscopy. Most of the data were obtained with the
1.5m Tillinghast telescope at the F. L. Whipple Observatory with typical
wavelength coverage of 3700-7400A and a resolution of ~7A. The earliest spectra
are thirteen days before B-band maximum; two-thirds of the SNe were observed
before maximum brightness. Coverage for some SNe continues almost to the
nebular phase. The consistency of the method of observation and the technique
of reduction makes this an ideal data set for studying the spectroscopic
diversity of SNe Ia.Comment: Accepted for publication in the Astronomical Journal, 109 pages
(including data table), 44 figures, full resolution figures at
http://www.noao.edu/noao/staff/matheson/Iaspec.ps.g
Coherent control of atomic excitation using off-resonant strong few-cycle pulses
We study the dynamics of a two-level system driven by an off-resonant
few-cycle pulse which has a phase jump at , in contrast to many
cycle pulses, under non rotating-wave approximation (NRWA). We give a closed
form analytical solution for the evolution of the probability amplitude for the upper level. Using the appropriate pulse parameters like
phase-jump , jump time , pulse width , frequency and
Rabi frequency the population transfer, after the pulse is gone,
can be optimized and for the pulse considered here, enhancement of
factor was obtained.Comment: 5 Pages, 7 Figure
Aircraft control via variable cant-angle winglets
Copyright @ 2008 American Institute of Aeronautics and AstronauticsThis paper investigates a novel method for the control of "morphing" aircraft. The concept consists of a pair of winglets; with adjustable cant angle, independently actuated and mounted at the tips of a baseline flying wing. The general philosophy behind the concept was that for specific flight conditions such as a coordinated turn, the use of two control devices would be sufficient for adequate control. Computations with a vortex lattice model and subsequent wind-tunnel tests demonstrate the viability of the concept, with individual and/or dual winglet deflection producing multi-axis coupled control moments. Comparisons between the experimental and computational results showed reasonable to good agreement, with the major discrepancies thought to be due to wind-tunnel model aeroelastic effects.This work has been supported by a Marie Curie excellence research grant funded by the European Commission
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