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Network Delays (network + delay)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Increasing the throughput of HomePNA

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2008
Aurelio Amodei Jr
Abstract In this paper we propose a new medium access mechanism for HomePNAv2 and HomePNAv3 standards. This mechanism uses a priority aggregation mechanism to avoid collisions, increasing these protocols throughput. Furthermore, this mechanism does not require modifying standards, since it can be implemented over their actual MAC sublayers. Simulation results show that the proposed mechanism is able to increase the throughput up to 44% for HomePNAv2 and 36% for HomePNAv3. Moreover, we also show how this mechanism affects network delay, analyzing average delay and jitter for all protocols presented. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Tracking control for sampled-data systems with uncertain time-varying sampling intervals and delays

INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 4 2010
N. van de Wouw
Abstract In this paper, a solution to the approximate tracking problem of sampled-data systems with uncertain, time-varying sampling intervals and delays is presented. Such time-varying sampling intervals and delays can typically occur in the field of networked control systems. The uncertain, time-varying sampling and network delays cause inexact feedforward, which induces a perturbation on the tracking error dynamics, for which a model is presented in this paper. Sufficient conditions for the input-to-state stability (ISS) of the tracking error dynamics with respect to this perturbation are given. Hereto, two analysis approaches are developed: a discrete-time approach and an approach in terms of delay impulsive differential equations. These ISS results provide bounds on the steady-state tracking error as a function of the plant properties, the control design and the network properties. Moreover, it is shown that feedforward preview can significantly improve the tracking performance and an online extremum seeking (nonlinear programming) algorithm is proposed to online estimate the optimal preview time. The results are illustrated on a mechanical motion control example showing the effectiveness of the proposed strategy and providing insight into the differences and commonalities between the two analysis approaches. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Robotic pyeloplasty using internet protocol and satellite network-based telesurgery

THE INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY, Issue 1 2008
C. Y. Nguan
Abstract Background In North America, the urological community has embraced surgical robotic technology in the performance of complex laparoscopic surgery. The performance of complex long-distance telesurgery requires further investigation prior to clinical application. Methods The feasibility of laparoscopic robot-assisted pyeloplasty in a porcine model was assessed using the Zeus robot and the internet protocol virtual private network (IP-VPNe) and satellite links. Eighteen pyeloplasty procedures were performed, using real-time, IP-VPNe and satellite network connection (six of each). Network and objective operative data were collected. Results Despite network delays and jitter, it was feasible to perform the pyeloplasty procedure without significant detriment in operative time or surgical results compared with real-time surgery. Conclusion The completion of complex tasks such as robotic pyeloplasty is feasible using both land-line and satellite telesurgery. However, the clinical relevance of telesurgery requires further assessment. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Maximum likelihood estimators of clock offset and skew under exponential delays

APPLIED STOCHASTIC MODELS IN BUSINESS AND INDUSTRY, Issue 4 2009
Jun Li
Abstract Accurate clock synchronization is essential for many data network applications. Various algorithms for synchronizing clocks rely on estimators of the offset and skew parameters that describe the relation between times measured by two different clocks. Maximum likelihood estimation (MLE) of these parameters has previously been considered under the assumption of exponentially distributed network delays with known means. We derive the MLEs under the more common case of exponentially distributed network delays with unknown means and compare their mean-squared error properties to a recently proposed alternative estimator. We investigate the robustness of the derived MLE to the assumption of non-exponential network delays, and demonstrate the effectiveness of a bootstrap bias-correction technique. Copyright © 2009 John Wiley & Sons, Ltd. [source]