| 1. |
- Biyani, Pravesh, et al.
(författare)
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Early Estimation of Voice over IPQuality
- 2003
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Konferensbidrag (refereegranskat)abstract
- Users of Voice over IP (VoIP) applications are sensitive to the quality of an ongoing call. We hypothesize that the quality of a VoIP session can be estimated from the first few seconds of the session and this can be generalized to other VoIP calls. Our approach is an in-band probing mechanism and does not require any external monitoring schemes or network support. We show by post processing VoIP data from globally distributed sites that it is possible to determine the quality after an initial number of seconds. One application is admission control, where it would be possible to reject poor quality calls before they are fully established.
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| 2. |
- Dima, Danai, et al.
(författare)
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Subcortical volumes across the lifespan : Data from 18,605 healthy individuals aged 3-90 years.
- 2022
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Ingår i: Human Brain Mapping. - : Wiley. - 1065-9471 .- 1097-0193. ; 43:1, s. 452-469
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Tidskriftsartikel (refereegranskat)abstract
- Age has a major effect on brain volume. However, the normative studies available are constrained by small sample sizes, restricted age coverage and significant methodological variability. These limitations introduce inconsistencies and may obscure or distort the lifespan trajectories of brain morphometry. In response, we capitalized on the resources of the Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) Consortium to examine age-related trajectories inferred from cross-sectional measures of the ventricles, the basal ganglia (caudate, putamen, pallidum, and nucleus accumbens), the thalamus, hippocampus and amygdala using magnetic resonance imaging data obtained from 18,605 individuals aged 3-90 years. All subcortical structure volumes were at their maximum value early in life. The volume of the basal ganglia showed a monotonic negative association with age thereafter; there was no significant association between age and the volumes of the thalamus, amygdala and the hippocampus (with some degree of decline in thalamus) until the sixth decade of life after which they also showed a steep negative association with age. The lateral ventricles showed continuous enlargement throughout the lifespan. Age was positively associated with inter-individual variability in the hippocampus and amygdala and the lateral ventricles. These results were robust to potential confounders and could be used to examine the functional significance of deviations from typical age-related morphometric patterns.
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| 3. |
- Frangou, Sophia, et al.
(författare)
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Cortical thickness across the lifespan : Data from 17,075 healthy individuals aged 3-90 years
- 2022
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Ingår i: Human Brain Mapping. - : John Wiley & Sons. - 1065-9471 .- 1097-0193. ; 43:1, s. 431-451
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Tidskriftsartikel (refereegranskat)abstract
- Delineating the association of age and cortical thickness in healthy individuals is critical given the association of cortical thickness with cognition and behavior. Previous research has shown that robust estimates of the association between age and brain morphometry require large-scale studies. In response, we used cross-sectional data from 17,075 individuals aged 3-90 years from the Enhancing Neuroimaging Genetics through Meta-Analysis (ENIGMA) Consortium to infer age-related changes in cortical thickness. We used fractional polynomial (FP) regression to quantify the association between age and cortical thickness, and we computed normalized growth centiles using the parametric Lambda, Mu, and Sigma method. Interindividual variability was estimated using meta-analysis and one-way analysis of variance. For most regions, their highest cortical thickness value was observed in childhood. Age and cortical thickness showed a negative association; the slope was steeper up to the third decade of life and more gradual thereafter; notable exceptions to this general pattern were entorhinal, temporopolar, and anterior cingulate cortices. Interindividual variability was largest in temporal and frontal regions across the lifespan. Age and its FP combinations explained up to 59% variance in cortical thickness. These results may form the basis of further investigation on normative deviation in cortical thickness and its significance for behavioral and cognitive outcomes.
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| 4. |
- Giribet, Juan I., et al.
(författare)
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Dual Quaternion Cluster-Space Formation Control
- 2021
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Ingår i: IEEE Robotics and Automation Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 2377-3766. ; 6:4, s. 6789-6796
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Tidskriftsartikel (refereegranskat)abstract
- We present a tracking controller for mobile multi-robot systems based on dual quaternion pose representations applied to formations of robots in a leader-follower configuration, by using a cluster-space state approach. The proposed controller improves system performance with respect to previous works by reducing steady-state tracking errors. The performance is evaluated through experimental field tests with a formation of an unmanned ground vehicle (UGV) and an unmanned aerial vehicle (UAV), as well as a formation of two UAVs.
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| 5. |
- Hagsand, Olof, et al.
(författare)
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Self-Admission Control for IP Telephony using Early Quality Estimation
- 2004
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Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. ; 3042, s. 381-391
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Tidskriftsartikel (refereegranskat)abstract
- If quality of service could be provided at the transport or the application layer, then it might be deployed simply by software upgrades, instead of requiring a complete upgrade of the network infrastructure. In this paper, we propose a self-admission control scheme that does not require any network support or external monitoring schemes. We apply the admission control scheme to IP telephony as it is an important application benefiting from admission control. We predict the quality of the call by observing the packet loss over a short initial period using an in-band probing mechanism. The quality prediction is then used by the application to continue or to abort the call. Using over 9500 global IP telephony measurements, we show that it is possible to accurately predict the quality of a call. Early rejection of sessions has the advantage of saving valuable network resources plus not disturbing the on-going calls.
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| 6. |
- Hagsand, Olof, et al.
(författare)
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Self-admission control for ip telephony using early quality estimation
- 2004. - 1
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Ingår i: NETWORKING 2004, Networking Technologies, Services, and Protocols; Performance of Computer and Communication Networks; Mobile and Wireless Communications (Third International IFIP-TC6 Networking Conference, Athens, Greece, May 9-14, 2004. Proceedings). - Berlin, Heidelberg : Springer. - 9783540219590 ; , s. 381-391
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Bokkapitel (refereegranskat)abstract
- If quality of service could be provided at the transport or the application layer, then it might be deployed simply by software upgrades, instead of requiring a complete upgrade of the network infrastructure. In this paper, we propose a self-admission control scheme that does not require any network support or external monitoring schemes. We apply the admission control scheme to IP telephony as it is an important application benefiting from admission control. We predict the quality of the call by observing the packet loss over a short initial period using an in-band probing mechanism. The quality prediction is then used by the application to continue or to abort the call. Using over 9500 global IP telephony measurements, we show that it is possible to accurately predict the quality of a call. Early rejection of sessions has the advantage of saving valuable network resources plus not disturbing the on-going calls.
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| 7. |
- Karlsson, Gunnar, et al.
(författare)
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Quality of Service and the End-to-End argument
- 2007
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Ingår i: IEEE Network. - 0890-8044 .- 1558-156X. ; 21:6, s. 16-21
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Tidskriftsartikel (refereegranskat)abstract
- Audio-visual services are now commonly used on the Internet. Many of them are based on batch downloading of contents for later replay. Real-time interactive and streaming services are now rapidly becoming popular. These services would benefit from quality of service if it were widely provided. The purpose of this article is to show how QoS solutions may be introduced incrementally. Quality is obtained by means of a probe-based admission control that can be exerted outside the network. The introduction of QoS starts from self-admission control in the application layer, followed by transport layer service differentiation. These two steps do not require any change to the network. If motivated, scheduling for service class separation in the network may be added. We show by proof of concept how QoS may be provided in agreement with the end-to-end argument. The three steps of our proposal are compared and discussed with respect to the possibility of deployment.
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| 8. |
- Karlsson, Gunnar, et al.
(författare)
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Single-Service Quality Differentiation
- 2004
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Ingår i: 2004 Twelfth IEEE International Workshop on Quality of Service, IWQoS 2004. ; , s. 265-272
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a scheme for quality of service differentiation for single-service networks that is based on the use of two separate forms of traffic control at the transport layer: Streams are controlled by means of probe-based admission control and elastic flows are controlled by TCP. The controls allow separation of traffic into two distinct service classes. The stream class is designed to provide a consistent quality for interactive audiovisual communication, as favored by human perception. It is responsive to load variations as an aggregate through blocking of sessions, while TCP is responsive on the flow level. Streams can be isolated against disturbances from probes and TCP flows by means of error-control coding. We show that the two traffic controls can coexist without starvation, and the proposed scheme might thus provide a first step towards differentiated services end-to-end.
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| 9. |
- Kehoe, Laura, et al.
(författare)
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Make EU trade with Brazil sustainable
- 2019
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 364:6438, s. 341-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 10. |
- Lundqvist, Henrik, et al.
(författare)
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Edge-based Differentiated Services
- 2005
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Ingår i: Lecture Notes in Computer Science. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0302-9743 .- 1611-3349. ; 3552, s. 259-270
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Tidskriftsartikel (refereegranskat)abstract
- Network quality of service is traditionally thought to be provided by a combination of scheduling in the network nodes to enforce a capacity sharing policy and traffic controls to prevent congestion that could annihilate that policy. The work presented herein is instead based on an end-to-end argument: A capacity sharing policy is enforced by traffic controls in the hosts at the edges of the network, without any scheduling support in the network. Our proposal is to add a feed-forward control at the transport layer to provide a service that is better suited to conversational and streaming applications than the batch-oriented transfer mode provided by TCP. The paper presents the control and its evaluation: We compare the sharing of capacity between traffic classes and study the loss rate seen by admitted streams. The outcome is that the new control adds a distinctly different service to the service offered by TCP for the Internet.
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