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TTL implementation of a CAMB tree network switch
Packet collisions and their resolution create a performance bottleneck in random-access LANs. A hardware solution to this problem is to use a collision avoidance switch. These switches allow the implementation of random access protocols without the penalty of collisions among packets. An architecture based on collision avoidance is the CAMB (Collision Avoidance Multiple Broadcast) Tree network, where concurrent broadcasts are possible.The purpose of this paper is to present two implementations for a CAMB Tree switch. First, a general outline of the CAMB switch is provided. Then, a description of the two implementations is given
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Implementation of a station/network interface for a CAMB tree network
Packet collisions and their resolution create a performance bottleneck in random-access LANs. A hardware solution to this problem is to use collision avoidance switches. These switches allow the implementation of random access protocols without the penalty of collisions among packets. An architecture based on collision avoidance is the CAMB (Collision Avoidance Multiple Broadcast) tree network, where concurrent broadcasts are possible.This paper is a companion to an earlier report. "TTL Implementations of a CAMB Tree Switch," where a tree network architecture was described for two different implementations of a CAMB tree switch. In the pages that follow, a hardware implementation of the interface between the network stations and the packet switches is proposed. This implementation is based on the first switch design in the companion paper
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Design implementation and measurement of a collision avoidance multiple broadcast tree network
Packet collisions and their resolution create a performance bottleneck in random access LANs. Collision avoidance switches are a hardware solution to this problem [1, 2]. Collision avoidance switches allow the implementation of random access protocols without the penalty of collisions among packets.In this paper, we describe a design and implementation of a local area network architecture based on collision avoidance, called the Collision Avoidance Multiple Broadcast (CAMB) tree network. Our implementation follows the protocol layering architecture of the IEEE 802 local area networks, and includes CAMB tree switches, station/network interface boards, and support of transport protocols. We also present the performance measurements of our experimental CAMB tree network
The Cosmic Linear Anisotropy Solving System (CLASS) III: Comparision with CAMB for LambdaCDM
By confronting the two independent Boltzmann codes CLASS and CAMB, we
establish that for concordance cosmology and for a given recombination history,
lensed CMB and matter power spectra can be computed by current codes with an
accuracy of 0.01%. We list a few tiny changes in CAMB which are necessary in
order to reach such a level. Using the common limit of the two codes as a set
of reference spectra, we derive precision settings corresponding to fixed
levels of error in the computation of a CMB likelihood. We find that for a
given precision level, CLASS is about 2.5 times faster than CAMB for computing
the lensed CMB spectra of a LambdaCDM model. The nature of the main
improvements in CLASS (which may each contribute to these performances) is
discussed in companion papers.Comment: 16 pages, 4 figures, 1 table. Typos corrected, comparison extended to
lower precision settings. Code available at http://class-code.ne
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Collision Avoidance Tree networks
The Collision Avoidance Tree is a new local area network based on a hardware device called collision avoidance switch, which arbitrates random access to a shared communications channel. Collision Avoidance Tree combines the benefits of random access (low delay when traffic is light; simple, distributed, and therefore robust, protocols) with concurrency of transmission, excellent network utilization and suitability for the domain of high-speed, optical networking.The Collision Avoidance Tree is classified in two classes: the Collision Avoidance Single Broadcast (CASB) Tree and the Collision Avoidance Multiple Broadcast (CAMB) Tree. The CASB Tree allows only a single transmission on the network at a given time, while the CAMB Tree is more general and allows concurrent transmissions on the network.This paper describes network architectures (e.g., station and switch protocols) and designs and implementations of the CASB and CAMB Trees. Performance results derived from analyses, simulations, measurements of experimental networks are also presented
CMB power spectrum parameter degeneracies in the era of precision cosmology
Cosmological parameter constraints from the CMB power spectra alone suffer
several well-known degeneracies. These degeneracies can be broken by numerical
artefacts and also a variety of physical effects that become quantitatively
important with high-accuracy data e.g. from the Planck satellite. We study
degeneracies in models with flat and non-flat spatial sections, non-trivial
dark energy and massive neutrinos, and investigate the importance of various
physical degeneracy-breaking effects. We test the CAMB power spectrum code for
numerical accuracy, and demonstrate that the numerical calculations are
accurate enough for degeneracies to be broken mainly by true physical effects
(the integrated Sachs-Wolfe effect, CMB lensing and geometrical and other
effects through recombination) rather than numerical artefacts. We quantify the
impact of CMB lensing on the power spectra, which inevitably provides
degeneracy-breaking information even without using information in the
non-Gaussianity. Finally we check the numerical accuracy of sample-based
parameter constraints using CAMB and CosmoMC. In an appendix we document recent
changes to CAMB's numerical treatment of massive neutrino perturbations, which
are tested along with other recent improvements by our degeneracy exploration
results.Comment: 27 pages, 28 figures. Latest CAMB version available from
http://camb.info/. Reduced number of figures, plot legend corrected and minor
edits to match published versio
Motivic invariant of real polynomial functions and Newton polyhedron
We propose a computation of real motivic zeta functions for real polynomial
functions, using Newton polyhedron. As a consequence we show that the weights
are blow-Nash invariants of convenient weighted homogeneous polynomials in
three variables.Comment: 22 pages in Math. Proc. Camb. Phil. Soc, 201
CMB Tensor Anisotropies in Metric f(R) Gravity
We present a description of CMB anisotropies generated by tensor
perturbations in f(R) theories of gravity. The temperature power spectrum in
the special case of is computed using a modified version of CAMB
package.Comment: 4 pages, 1 figure. Contribution submitted to the proceedings of the
Spanish Relativity Meeting ERE2011, September 2011, Madrid, Spai
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