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Search Results: 1 - 10 of 97 matches for " Gorry Fairhurst "
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Analysing TCP for Bursty Traffic  [PDF]
Israfil Biswas, Arjuna Sathiaseelan, Raffaello Secchi, Gorry Fairhurst
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.37078
Abstract: The Transmission Control Protocol has been designed to support interactive and bulk applications, with performance tuned to support bulk applications that desire to continuously send data. In contrast, this paper analyses TCP performance for a class of applications that do not wish to send continuous data, but instead generate bursts of data separated by application-limited periods in which little or no data is sent. In this context, the paper evaluates an experimental method, Congestion Window Validation (CWV), proposed to mitigate the network impact of bursty TCP applications. Simulation results show that TCP-CWV exhibits a conservative behaviour during application-limited periods. The results also show that TCP-CWV is able to use the available capacity after an idle period over a shared path and that this can have benefit, especially over long delay paths, when compared to slow-start restart specified by standard TCP. The paper recommends the development of CWV-like algorithms to improve the performance for bursty applications while also providing an incentive for application designers to use congestion control.
A Framework for an IP-Based DVB Transmission Network
Nimbe L. Ewald-Arostegui,Gorry Fairhurst,Ana Yun-Garcia
International Journal of Digital Multimedia Broadcasting , 2010, DOI: 10.1155/2010/394965
Abstract: One of the most important challenges for next generation all-IP networks is the convergence and interaction of wireless and wired networks in a smooth and efficient manner. This challenge will need to be faced if broadcast transmission networks are to converge with IP infrastructure. The 2nd generation of DVB standards supports the Generic Stream, allowing the direct transmission of IP-based content using the Generic Stream Encapsulation (GSE), in addition to the native Transport Stream (TS). However, the current signalling framework is based on MPEG-2 Tables that rely upon the TS. This paper examines the feasibility of providing a GSE signalling framework, eliminating the need for the TS. The requirements and potential benefits of this new approach are described. It reviews prospective methods that may be suitable for network discovery and selection and analyses different options for the transport and syntax of this signalling metadata. It is anticipated that the design of a GSE-only signalling system will enable DVB networks to function as a part of the Internet. 1. Introduction The first generation of DVB standards [1–3] uses a time-division transmission multiplexing method derived directly from the Moving Pictures Expert Group-2 Transport Stream (MPEG-2 TS) standards [4]. The MPEG-2 specifications define the Program Specific Information (PSI), a Table-based signalling system that is multiplexed with the content and allows a receiver to identify MPEG-2 Programs and to demultiplex their Program Elements from the TS. These Tables are segmented in Sections and directly encapsulated into MPEG-2 TS packets, as shown in Figure 1. The Digital Video Broadcasting (DVB) project specified additional types of Table, DVB-Service Information (SI) [5] while the Advanced Television System Committee (ATSC) also defined a set of Tables for the US market [6]. Figure 1: Current DVB MPEG-2 TS architecture. Current signalling metadata relies on this TS packet format [4]. The 2nd generation of DVB systems, DVB-S2/C2/T2 [7–9], preserved this signalling framework utilising MPEG-2 encoded Tables. Some transmission systems use IP-based Service Discovery and Selection (SD&S) procedures to obtain content metadata, for example, acquisition of an Electronic Service Guide (ESG), the network signalling necessary for the initial bootstrapping is sent using MPEG-2 encoded Tables, for example, in DVB-Handheld (DVB-H) and DVB-Satellite to Handheld (DVB-SH) systems [10, 11]. SD&S is a generic term that has been used to describe various discovery and selection procedures for, mainly,
Triangulation of gravitational wave sources with a network of detectors
Stephen Fairhurst
Physics , 2009, DOI: 10.1088/1367-2630/13/6/069602
Abstract: There is significant benefit to be gained by pursuing multi-messenger astronomy with gravitational wave and electromagnetic observations. In order to undertake electromagnetic follow-ups of gravitational wave signals, it will be necessary to accurately localize them in the sky. Since gravitational wave detectors are not inherently pointing instruments, localization will occur primarily through triangulation with a network of detectors. We investigate the expected timing accuracy for observed signals and the consequences for localization. In addition, we discuss the effect of systematic uncertainties in the waveform and calibration of the instruments on the localization of sources. We provide illustrative results of timing and localization accuracy as well as systematic effects for coalescing binary waveforms.
Improved source localization with LIGO India
Stephen Fairhurst
Physics , 2012, DOI: 10.1088/1742-6596/484/1/012007
Abstract: A global network of advanced gravitational wave interferometric detectors is under construction. These detectors will offer an order of magnitude improvement in sensitivity over the initial detectors and will usher in the era of gravitational wave astronomy. In this paper, we evaluate the benefits of relocating one of the advanced LIGO detectors to India.
Source localization with an advanced gravitational wave detector network
Stephen Fairhurst
Physics , 2010, DOI: 10.1088/0264-9381/28/10/105021
Abstract: We derive an expression for the accuracy with which sources can be localized using a network of gravitational wave detectors. The result is obtained via triangulation, using timing accuracies at each detector and is applicable to a network with any number of detectors. We use this result to investigate the ability of advanced gravitational wave detector networks to accurately localize signals from compact binary coalescences. We demonstrate that additional detectors can significantly improve localization results and illustrate our findings with networks comprised of the advanced LIGO, advanced Virgo and LCGT. In addition, we evaluate the benefits of relocating one of the advanced LIGO detectors to Australia.
Cuban maternity homes: a model to address at-risk pregnancy
Conner Gorry MA
MEDICC Review , 2011,
Over the hills & far away: rural health in Cuba
MA Conner Gorry
MEDICC Review , 2012,
Cuba's Latin American medical school: can socially-accountable medical education make a difference?
MA Conner Gorry
MEDICC Review , 2012,
Interpreting the results of searches for gravitational waves from coalescing binaries
Stephen Fairhurst,Patrick Brady
Physics , 2007, DOI: 10.1088/0264-9381/25/10/105002
Abstract: We introduce a method based on the loudest event statistic to calculate an upper limit or interval on the astrophysical rate of binary coalescence. The calculation depends upon the sensitivity and noise background of the detectors, and a model for the astrophysical distribution of coalescing binaries. There are significant uncertainties in the calculation of the rate due to both astrophysical and instrumental uncertainties as well as errors introduced by using the post--Newtonian waveform to approximate the full signal. We catalog these uncertainties in detail and describe a method for marginalizing over them. Throughout, we provide an example based on the initial LIGO detectors.
Extremality conditions for isolated and dynamical horizons
Ivan Booth,Stephen Fairhurst
Physics , 2007, DOI: 10.1103/PhysRevD.77.084005
Abstract: A maximally rotating Kerr black hole is said to be extremal. In this paper we introduce the corresponding restrictions for isolated and dynamical horizons. These reduce to the standard notions for Kerr but in general do not require the horizon to be either stationary or rotationally symmetric. We consider physical implications and applications of these results. In particular we introduce a parameter e which characterizes how close a horizon is to extremality and should be calculable in numerical simulations.
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