María Simon

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Video coding and ATM statistical bit rate capability

ATM Networks, 1997

This paper analyses the adequacy of the statistical bit rate (SBR) A TM transfer capability for s... more This paper analyses the adequacy of the statistical bit rate (SBR) A TM transfer capability for supporting real time video services, where end to end delay is limited. For these type of services, mean data rates are normally low. However, if a reasonable image quality consistency is imposed, the generated traffic becomes bursty. This results in important bandwidth availability requirements. A method is presented for ensuring that the generated traffic can be transmitted over an SBR connection while respecting the service requirements. Comparison with other transfer capabilities shows that SBR is outstanding in terms of application performance and network resources required.

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Desarrollo de una suite de pruebas para receptores de TV digital

The deployment of digital TV in Uruguay is ongoing, following the ISDB-Tb standard. The channels ... more The deployment of digital TV in Uruguay is ongoing, following the ISDB-Tb standard. The channels allocation process was completed, and after the adoption of a testing protocol, the introduction of decoders and receivers began in early 2014. Testing their compliance with the standards is of paramount importance in order to foster migration towards it and to provide a platform to local developers. The government committed the School of Engineering and the Software Testing Centre to the elaboration of the testing protocol. This article reports the key aspects of this work: the analysis of the standards, the definition of a type approval protocol and the experience gained by applying the testing procedures. Its goal is to share the experience and contribute to the improvement of the digital TV adoption process, hopefully aiding to avoid some problems that were detected during this work, both in regulation and in devices compliance to the standards.

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Combining Full Reference and No Reference Models for Broadcast Digital TV Quality Monitoring in Real Time

IEEE Transactions on Broadcasting, 2016

We present a novel combination of full reference (FR) and no reference (NR) quality models to est... more We present a novel combination of full reference (FR) and no reference (NR) quality models to estimate quality of experience of TV viewers in different locations of a digital TV station coverage area. An NR method is employed at a reference node with optimal reception. In this node the video impairments are only due to the acquisition and the TV station coding process, since the received digital TV signal is the same as the broadcasted. An FR method runs at the other receiving nodes, located at different geographic spots, where signal can be hit by different patterns of packet losses due to the transmission process. The FR method compares the signal received at these nodes with the one received at the reference node. The overall video quality in each geographic spot is calculated by combining the original quality estimation obtained with the NR method and the effects of transmission impairments obtained with the FR method. We show how this design overpasses the performance of previous NR developed methods.

Monitoring QoE on digital terrestrial TV: A comprehensive approach

2016 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting (BMSB), 2016

Deployment of a monitoring system for digital terrestrial television (DTV). It was designed to co... more Deployment of a monitoring system for digital terrestrial television (DTV). It was designed to collect and process information for broadcasters and regulatory bodies, in order to control and improve the quality of the delivered signal in its service area, which is in turn a factor to boost the adoption of DTV by the users. The system continuously measures the signal's RF parameters and transport stream characteristics at many places, using a common time base, in order to assess continuously and automatically the perceived quality, instead of measuring on request of users or broadcasters, when problems are experienced. The article describes the architecture of the system, which is distributed, scalable and very low cost, and shows a functional evaluation of the prototype deployment. Special attention is given to the quality models that emulate the human perception for audio and video, considering both non reference and full reference models. The system is modular, in such a way that different quality models may be used, independently from the acquisition, transmission and recording of quality parameters functionality.

Development of a digital TV receivers test suite

DYNA, 2015

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Studying digital terrestrial TV coverage

2014 IEEE International Symposium on Broadband Multimedia Systems and Broadcasting, 2014

This article presents the development of numerical models to simulate the propagation of the TV s... more This article presents the development of numerical models to simulate the propagation of the TV signal, and a set of measurements of the electromagnetic signal to adjust the models. These tools have been devised to help in the deployment of digital television, ISDB-Tb standard, in Uruguay. The aim is a country coverage as wide as possible. A good estimation of the signal propagation shall be used to choose the best places for transmitters, the transmission modes and to give guidelines for reception antennas installation. The implemented models, which are well known, are briefly described. The measuring method is more thoroughly described as there is no established procedure and the spectrum analyzer's settings are discussed. Spatial validation, using neighbouring points is proposed. The measuring method is validated both by its coincidence with the Friis formula for free space propagation, when this condition arises, and by the consistency between neighbouring points. Okumura-Hata and Recommendation ITU-R P.1546-4 models are well suited for coverage prediction in Montevideo using certain parameters that are justified in the article. The statistical analysis of the set of data issued from the campaign is presented and discussed.

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Quality of service parameters and link operating point estimation based on effective bandwidths

Performance Evaluation, 2005

This work addresses the estimation and calculation of the operating point of a network's link in ... more This work addresses the estimation and calculation of the operating point of a network's link in a digital traffic network. The notion of operating point comes from Effective Bandwidth (EB) theory. The results are valid for a wide range of traffic types. This means that the statistical characteristics of the traffic may be very general. We show that, given a good EB estimator, the operating point, i.e. the values of time and space (or multiplexing) parameters in which the EB gives the asymptotic overflow probability, can also be accurately estimated. Imposing some regularity conditions, a consistent estimator and confidence intervals of the operating point are developed. These conditions are very general, and they are met by commonly used estimators as the averaging estimator presented in or the Markov Fluid model estimator presented in . Using a software package developed by our workgroup that estimates the EB and other relevant parameters from traffic traces, simulation results are compared with the analytical results, showing very good fitting.

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Effective bandwidth estimation and testing for Markov sources

Performance Evaluation, 2002

This work addresses the resource sharing problem in broadband communication networks that can gua... more This work addresses the resource sharing problem in broadband communication networks that can guarantee some quality of service (QoS), and develops some results about data source and traffic modelling, especially in aspects of model testing and parameter estimation. The multiplexing of variable bit rate (VBR) sources poses a mathematical and statistical problem: the estimation of the resource requirements of a source or set of sources. The estimation method shall be simple enough to be practically implemented in the connection acceptance control (CAC) function. In this paper, the VBR video sources are taken as a typical case of variable rate, with real-time constraints. This association of requirements makes the case especially interesting. A Markov model is assumed for the VBR sources. The validity of such models is under research; they seem to be appropriate at least in certain time scales. The model is tested against real video traces. In order to estimate the resource allocation or "channel occupation" of each source, the concept of equivalent bandwidth proposed by Kelly [Notes on effective bandwidth, in: F.P. Kelly, S. Zachary, I.B. Ziedins (Eds.), Stochastic Networks: Theory and Applications, Oxford University Press, Oxford, 1996, pp. 141] is used; it is based on a consistent mathematical theory, and has proven to be robust and useful for technical applications. A calculation of the equivalent bandwidth of a Markov source, given its parameters, can be found in the literature [IEEE ACM Trans. Networking 1 (4) (1993) 424]. But in fact, one can only estimate model and parameters. In this work, an estimation of the equivalent bandwidth is given, which can be obtained from real data. The convergence and the consistency of the estimation are studied, and practical bounds are found. Illustrative calculations are performed from real video traces that were obtained using a software MPEG coder, developed by the authors. The mathematical and statistical results are valid for whatever phenomenon that can be modelled as a Markov process.

End-to-end quality of service-based admission control using the fictitious network analysis

Computer Communications, 2010

The performance analysis of a network link is a well studied problem. However, the most interesti... more The performance analysis of a network link is a well studied problem. However, the most interesting issue for a service provider is to evaluate the end-to-end quality of service (QoS). The evaluation of the end-to-end QoS (e.g. loss probability or delay) depends on the traffic statistic which is constantly modified as the traffic traverse the network, making its analysis a very difficult problem. In this work we use a simplified framework known as fictitious network analysis that allows us to estimate on-line the end-to-end loss ratio from input traffic traces statistics. We prove that the defined estimator is consistent and that a Central Limit Theorem is verified. Based on these estimations an admission control mechanism can be implemented. More precisely, we propose a simply method to estimate the control admission region, i.e. which are the flows that can be accepted in the network that verifies that its end-to-end loss ratio is smaller than a given threshold. While decisions based on the fictitious network analysis are safe, it may lead to network resources under-utilization (it generally overestimates the QoS parameters). In this work we establish sufficient conditions to assure that results obtained by means of the fictitious network coincide with real ones (there is no overestimation). We present first the conditions in the one-link case and extend them to the multilink case, necessary to evaluate the end-to-end loss ratio. When different results are obtained we define a method to find a bound for the overestimation. We also present numerical examples to compare the performance obtained in the real and the fictitious network, validating our main results.

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The Search for QoS in Data Networks: A Statistical Approach

Lecture Notes in Computer Science, 2011

New Internet services like video on-demand, high definition IPTV, high definition video conferenc... more New Internet services like video on-demand, high definition IPTV, high definition video conferences and some real time applications have strong QoS requirements regarding losses, delay, jitter, etc. This work addresses the challenge of guaranteeing quality of service (QoS) in the Internet from a statistical point of view. Three lines of work are proposed. The first one is about the estimation of the QoS parameters from traffic traces (in the context of large deviation theory and effective bandwidth). The second one, address the admission control problem from results of the many sources and small buffer asymptotic. Finally, the third line focuses on the estimation of QoS parameters seen by an application based on end-to-end active measurements and statistical learning tools.

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