The Experts below are selected from a list of 252 Experts worldwide ranked by ideXlab platform
Leandros Tassiulas - One of the best experts on this subject based on the ideXlab platform.
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end to end bandwidth guarantees through fair Local Spectrum share in wireless ad hoc networks
IEEE Transactions on Automatic Control, 2005Co-Authors: Saswati Sarkar, Leandros TassiulasAbstract:Sharing the common Spectrum among the links in a vicinity is a fundamental problem in wireless ad-hoc networks. Lately, some scheduling approaches have been proposed that guarantee fair share of bandwidth among the links. The quality of service perceived by the applications however depends on the end-to-end bandwidth allocated to the multihop sessions. We propose an algorithm that provides provably maxmin fair end-to-end bandwidth to sessions. The algorithm combines a link scheduling that avoids collisions, a fair session service discipline per link, and a hop-by-hop window flow control. All the stages of the algorithm are implementable based on Local information, except the link scheduling part that needs some network-wide coordination.
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end to end bandwidth guarantees through fair Local Spectrum share in wireless ad hoc networks
Conference on Decision and Control, 2003Co-Authors: Saswati Sarkar, Leandros TassiulasAbstract:Sharing the Locally common Spectrum among the links of the same vicinity is a fundamental problem in wireless ad-hoc networks. Lately some scheduling approaches have been proposed that guarantee fair share of the bandwidth among the links. What really affects the quality of service perceived by the applications though, is the effective end-to-end bandwidth allocated to the different network sessions that span several links. We propose an algorithm that provides fair session rates in that context. The algorithm is based on a combination of a link scheduling method to avoid Local conflicts, a fair session service discipline per link and a hop-by-hop window flow control scheme. It can be shown that the long term rates allocated to the different sessions are maxmin fair. All the stages of the algorithm are implementable based on Local information only, except the link scheduling part that needs some network-wide coordination. Some numerical study is performed to evaluate the impact of various parameter choices on the performance of the algorithm.
Saswati Sarkar - One of the best experts on this subject based on the ideXlab platform.
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end to end bandwidth guarantees through fair Local Spectrum share in wireless ad hoc networks
IEEE Transactions on Automatic Control, 2005Co-Authors: Saswati Sarkar, Leandros TassiulasAbstract:Sharing the common Spectrum among the links in a vicinity is a fundamental problem in wireless ad-hoc networks. Lately, some scheduling approaches have been proposed that guarantee fair share of bandwidth among the links. The quality of service perceived by the applications however depends on the end-to-end bandwidth allocated to the multihop sessions. We propose an algorithm that provides provably maxmin fair end-to-end bandwidth to sessions. The algorithm combines a link scheduling that avoids collisions, a fair session service discipline per link, and a hop-by-hop window flow control. All the stages of the algorithm are implementable based on Local information, except the link scheduling part that needs some network-wide coordination.
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end to end bandwidth guarantees through fair Local Spectrum share in wireless ad hoc networks
Conference on Decision and Control, 2003Co-Authors: Saswati Sarkar, Leandros TassiulasAbstract:Sharing the Locally common Spectrum among the links of the same vicinity is a fundamental problem in wireless ad-hoc networks. Lately some scheduling approaches have been proposed that guarantee fair share of the bandwidth among the links. What really affects the quality of service perceived by the applications though, is the effective end-to-end bandwidth allocated to the different network sessions that span several links. We propose an algorithm that provides fair session rates in that context. The algorithm is based on a combination of a link scheduling method to avoid Local conflicts, a fair session service discipline per link and a hop-by-hop window flow control scheme. It can be shown that the long term rates allocated to the different sessions are maxmin fair. All the stages of the algorithm are implementable based on Local information only, except the link scheduling part that needs some network-wide coordination. Some numerical study is performed to evaluate the impact of various parameter choices on the performance of the algorithm.
Michael J Medley - One of the best experts on this subject based on the ideXlab platform.
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cross layer routing and dynamic Spectrum allocation in cognitive radio ad hoc networks
IEEE Transactions on Vehicular Technology, 2010Co-Authors: Lei Ding, Tommaso Melodia, Stella N Batalama, John D Matyjas, Michael J MedleyAbstract:Throughput maximization is one of the main challenges in cognitive radio ad hoc networks, where the availability of Local Spectrum resources may change from time to time and hop by hop. For this reason, a cross-layer opportunistic Spectrum access and dynamic routing algorithm for cognitive radio networks is proposed, which is called the routing and dynamic Spectrum-allocation (ROSA) algorithm. Through Local control actions, ROSA aims to maximize the network throughput by performing joint routing, dynamic Spectrum allocation, scheduling, and transmit power control. Specifically, the algorithm dynamically allocates Spectrum resources to maximize the capacity of links without generating harmful interference to other users while guaranteeing a bounded bit error rate (BER) for the receiver. In addition, the algorithm aims to maximize the weighted sum of differential backlogs to stabilize the system by giving priority to higher capacity links with a high differential backlog. The proposed algorithm is distributed, computationally efficient, and has bounded BER guarantees. ROSA is shown through numerical model-based evaluation and discrete-event packet-level simulations to outperform baseline solutions, leading to a high throughput, low delay, and fair bandwidth allocation.
Lalu Mansinha - One of the best experts on this subject based on the ideXlab platform.
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Time-Local Fourier analysis with a scalable, phase-modulated analyzing function: the S -transform with a complex window
Signal Processing, 2004Co-Authors: C. R. Pinnegar, Lalu MansinhaAbstract:The S-transform was originally defined as a method of determining the Local Spectrum of a time series, through the use of a translating, real Gaussian window that dilates to accomodate the different cycle durations of different frequencies. The S-transform "wavelet" is obtained by multiplying this real window with the complex Fourier sinusoid. Since the Fourier sinusoid has time-invariant frequency, the S-transform is consequently unsuitable for resolving waveforms whose frequency changes with time. This problem can be addressed by introducing a complex Gaussian window, with a user designed, complex phase function. The phase function modulates the frequency of the Fourier sinusoid to give a specific waveform, leading to better time frequency Localization of similar waveforms on the time series. The complex-window S-transform is similar to a wavelet transform, but has the fixed phase reference of the Fourier transform.
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pattern analysis with two dimensional spectral Localisation applications of two dimensional s transforms
Physica A-statistical Mechanics and Its Applications, 1997Co-Authors: Lalu Mansinha, R G Stockwell, R P LoweAbstract:Abstract An image is a function, f(x, y) , of the independent space variables x and y . The global Fourier Spectrum of the image is a complex function F(k x , k y ) of the wave numbers k x and k y . The global Spectrum may be viewed as a construct of the spectra of an arbitrary number of segments of f(x, y) , leading to the concept of a Local Spectrum at every point of f(x, y) . The two-dimensional S transform is introduced here as a method of computation of the Local Spectrum at every point of an image. In addition to the variables x and y , the 2-D S transform retains the variables k x and k y , being a complex function of four variables. Visualisation of a function of four variables is difficult. We skirt around this by removing one degree of freedom, through examination of ‘slices’. Each slice of the 2-D S transform would then be a complex function of three variables, with separate amplitude and phase components. By ranging through judiciously chosen slice locations the entire S transform can be examined. Images with strictly periodic patterns are best analysed with a global Fourier Spectrum. On the other hand, the 2-D S transform would be more useful in spectral characterisation of aperiodic or random patterns.
Nils Byrial Andersen - One of the best experts on this subject based on the ideXlab platform.
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Local spectral radius formulas for a class of unbounded operators on banach spaces
Journal of Operator Theory, 2013Co-Authors: Nils Byrial AndersenAbstract:We exhibit unbounded operators on Banach spaces having the single-valued extension property, for which the Local Spectrum at suitable points can be determined, and for which a Local spectral radius formula holds, analogous to that for a bounded operator on a Banach space with the singlevalued extension property. Such an operator can occur as (an extension of) a differential operator which, roughly speaking, can be diagonalised on its domain of smooth test functions via a discrete transform which is an isomorphism of topological vector spaces between the domain, in its own topology, and a sequence space. We give examples (constant coefficient differential operators on the d-torus, Jacobi operators, the Hermite operator, Laguerre operators) and indicate further perspectives.
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Local spectral radius formulas for a class of unbounded operators on banach spaces
arXiv: Spectral Theory, 2010Co-Authors: Nils Byrial AndersenAbstract:We exhibit a general class of unbounded operators in Banach spaces which can be shown to have the single-valued extension property, and for which the Local Spectrum at suitable points can be determined. We show that a Local spectral radius formula holds, analogous to that for a globally defined bounded operator on a Banach space with the single-valued extension property. An operator of the class under consideration can occur in practice as (an extension of) a differential operator which, roughly speaking, can be diagonalised on its domain of smooth test functions via a discrete transform, such that the diagonalising transform establishes an isomorphism of topological vector spaces between the domain of the differential operator, in its own topology, and a sequence space. We give concrete examples of (extensions of) such operators (constant coefficient differential operators on the d-torus, Jacobi operators, the Hermite operator, Laguerre operators) and indicate further perspectives.
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Local spectral radius formulas on compact lie groups
arXiv: Representation Theory, 2008Co-Authors: Nils Byrial AndersenAbstract:We determine the Local Spectrum of a central element of the complexified universal enveloping algebra of a compact connected Lie group at a smooth function as an element of L^p(G). Based on this result we establish a corresponding Local spectral radius formula.
