Martín Varela

Martín Varela
Profilence

PhD - Université de Rennes 1

About

87
Publications
35,000
Reads
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1,325
Citations
Citations since 2016
24 Research Items
849 Citations
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2016201720182019202020212022020406080100120140
2016201720182019202020212022020406080100120140
2016201720182019202020212022020406080100120140
Additional affiliations
September 2013 - February 2017
VTT Technical Research Centre of Finland
Position
  • Principal Investigator
June 2007 - September 2013
VTT Technical Research Centre of Finland
Position
  • Senior Researcher
September 2006 - May 2007
VTT Technical Research Centre of Finland
Position
  • PostDoc Position
Education
October 2002 - November 2005
Université de Rennes 1
Field of study
  • Computer Science
September 2001 - July 2002
Université de Rennes 1
Field of study
  • Computer Science
March 1996 - April 2001
Universidad de la República de Uruguay
Field of study
  • Computing Engineering

Publications

Publications (87)
Article
Full-text available
Cloud computing is currently gaining enormous momentum due to a number of promised benefits: ease of use in terms of deployment, administration, and maintenance, along with high scalability and flexibility to create new services. However, as more personal and business applications migrate to the cloud, service quality will become an important diffe...
Article
This paper addresses the problem of quantitatively evaluating the quality of a speech stream transported over the Internet as perceived by the end-user. We propose an approach being able to perform this task automatically and, if necessary, in real time. Our method is based on using G-networks (open networks of queues with positive and negative cus...
Article
Full-text available
With Quality of Experience (QoE) research having made significant advances over the years, service and network providers aim at user-centric evaluation of the services provided in their system. The question arises how to derive QoE in systems. In the context of subjective user studies conducted to derive relationships between influence factors and...
Preprint
Full-text available
In the context of QoE management, network and service providers commonly rely on models that map system QoS conditions (e.g., system response time, paket loss, etc.) to estimated end user QoE values. Observable QoS conditions in the system may be assumed to follow a certain distribution, meaning that different end users will experience different co...
Article
With Quality of Experience (QoE) research having made significant advances over the years, increased attention is being put on exploiting this knowledge from a service/network provider perspective in the context of the user-centric evaluation of systems. Current research investigates the impact of system/service mechanisms, their implementation or...
Preprint
Full-text available
For the quantification of QoE, subjects often provide individual rating scores on certain rating scales which are then aggregated into Mean Opinion Scores (MOS). From the observed sample data, the expected value is to be estimated. While the sample average only provides a point estimator, confidence intervals (CI) are an interval estimate which con...
Article
Full-text available
Quality of Experience (QoE) has received much attention over the past years and has become a prominent issue for delivering services and applications. A significant amount of research has been devoted to understanding, measuring, and modelling QoE for a variety of media services. The next logical step is to actively exploit that accumulated knowled...
Conference Paper
Full-text available
Queueing systems following a first-in-first-out (FIFO) strategy are well understood and various results are known for the response time of the system. However, the question arises how the results look like when taking into account a user-centric point of view. To this end, an M/M/1-FIFO system is investigated for the setup of different Internet ser...
Article
Full-text available
Complementing the current paradigm change from QoS to QoE, we address fundamental QoE charging issues for Internet services from an end user perspective. Here, key issues arise from gaps of different information contexts involved, which have to be managed when introducing a QoE product. Hence, this paper analyzes the double role of prices for quali...
Article
Full-text available
The user-centric management of networks and services focuses on the Quality of Experience (QoE) as perceived by the end user. In general, the goal is to maximize (or at least ensure an acceptable) QoE, while ensuring fairness among users, e.g., in terms of resource allocation and scheduling in shared systems. A problem arising in this context is th...
Preprint
IEEE Communications Letters Vol.21 Nr.1, 184-187 ; User-centric service and application management focuses on the quality of experience (QoE) as perceived by the end user. Thereby, the goal is to maximize QoE while ensuring fairness among users, e.g., for resource allocation and scheduling in shared systems. Although the literature suggests to cons...
Article
Full-text available
User-centric service and application management focuses on the Quality of Experience (QoE) as perceived by the end user. Thereby, the goal is to maximize QoE while ensuring fairness among users, e.g., for resource allocation and scheduling in shared systems. Although the literature suggests to consider consequently QoE fairness, there is currently...
Article
Full-text available
While Quality of Experience (QoE) has advanced very significantly as a field in recent years, the methods used for analyzing it have not always kept pace. When QoE is studied, measured or estimated, practically all the literature deals with the so-called Mean Opinion Score (MOS). The MOS provides a simple scalar value for QoE, but it has several li...
Article
Full-text available
This technical report formally defines the QoE metrics which are introduced and discussed in the article "QoE Beyond the MOS: An In-Depth Look at QoE via Better Metrics and their Relation to MOS" by Tobias Hossfeld, Poul E. Heegaard, Martin Varela, Sebastian M\"oller, accepted for publication in the Springer journal "Quality and User Experience". M...
Conference Paper
Full-text available
In this short paper we briefly describe the results of analyzing a large-scale data set of actual YouTube stall patterns collected worldwide as part of Columbia University's YouSlow project, and how we used it to create a simple model for generating realistic stalling patterns with a given number of stalls, a given average stall duration, and a pat...
Chapter
This chapter defines QoE as a user-centric concept of service quality. It provides a definition of QoE in various standardization fora, such as ITU, ETSI, and IETF.
Conference Paper
Full-text available
HTTP video is quickly becoming a dominating type of traffic on the Internet, with popular services such as YouTube and Netflix being used by hundreds of millions of users daily, and showing ever-growing usage numbers. Understanding Quality of Experience (QoE) for these services is an important topic, and one that has been addressed in the literatur...
Conference Paper
The rapid growth of video traffic on the Internet raises many challenges for Internet service providers in managing their network resources. An emerging trend in this regard is the development of network management strategies to enhance the quality experienced by the end-users (Quality of Experience — QoE). In this paper, we introduce an admission...
Conference Paper
Full-text available
Traditionally, Quality of Experience (QoE) assessment results (or objective estimations thereof) are presented as a single scalar value, typically a Mean Opinion Score (MOS). While useful, the limitations of MOS are evident even in its name; for many applications, just having a mean value is simply not enough. For service providers in particular, i...
Conference Paper
Full-text available
Web services and applications are an increasingly pervasive fixture of modern life and business. This paper reports on a Web-based crowdsourced subjective assessment campaign in which we studied the effects of network performance and design aspects of manipulated Web sites on the perceived performance, perceived ease-of-use, visual appeal, as well...
Article
Full-text available
This report provides an overview of the program, discussions and outcomes of Dagstuhl Seminar 15022 "Quality of Experience: From Assessment to Application", which took place from 4 - 7 January 2015 at Schloss Dagstuhl - Leibniz Center for Informatics. The seminar and the challenges that were addressed have their roots in the earlier Dagstuhl Semina...
Conference Paper
Full-text available
Fast growing data traffic over mobile networks pose many challenges for both end systems and networks to satisfy the required service levels of different applications. For end-users, the quality of experience (QoE), and consequently the underlying quality of service (QoS) are the most meaningful criteria for triggering handovers and selecting targe...
Article
Full-text available
In this paper we propose a methodological framework for modeling Quality of Experience (QoE) for media services in a generic manner. We consider QoE as a multi-dimensional concept dependent on several factors related to the service itself, its resource requirements, its users, and its context of use. As a first step, we group these factors into fou...
Conference Paper
Telemedicine applications provide many opportunities for improving health care in a variety of conditions, in particular for people living in remote or geographically isolated areas without fast access to doctors ('medical deserts'), such as some parts of Finland. In many applications, the technologies used are actually off-the shelf solutions for...
Chapter
The Celtic Plus Quality of Experience Estimators in Networks (QuEEN) project was conceived to create a suitable conceptual framework for Quality of Experience (QoE). This chapter presents some of the conceptual results produced so far within QuEEN (and other related activities, such as COST Action IC1003 Qualinet). It provides an overview of the Qu...
Chapter
Full-text available
This chapter proposes an ecosystem that allows the management of customer experience to guarantee the quality levels delivered to end users, which has been defined into the Eureka Celtic internet protocol network monitoring for quality of service intelligent support (IPNQSIS) project and is adapted for over-the-top (OTT) services inside the Eureka...
Article
Multimedia service providers and operators need tools that can estimate the quality of the services delivered to their end-customers. While laboratory-originated data is accurate and reliable, the performance of Quality of Experience (QoE) models could be improved by taking into account the real context of use. This chapter compares results of a la...
Conference Paper
With the availability of cloud computing infrastructures, migrating business-critical functionality to public clouds is becoming commonplace. Cloud providers typically offer a variety of computing capabilities and pricing options. Therefore, the problem of selecting the ones that suit enterprise needs becomes critical. Our major focus is on the mig...
Chapter
Full-text available
It is often the case that in the current literature, the term “QoE” is used in contexts where “QoS” would be more appropriate. This is likely due to several reasons, one of which being the current popularity of all things related with QoE, but more fundamentally it is due to the boundaries between QoS and QoE not being clearly defined—and indeed, s...
Article
Full-text available
Evaluating (audio)visual quality and Quality of Experience (QoE) from the user's perspective, has become a key element in optimizing users' experiences and their quality. Traditionally, the focus lies on how multi-level quality features are perceived by a human user. The interest has however gradually expanded towards human cognitive, affective and...
Article
Full-text available
This program allows the generation of several accurate (with respect to pre-defined target values) loss traces following a simplified Gilbert loss model (2-states, one with no losses, and one with loss probability = 1). For subjective testing, the challenge lies in getting the right stats within a few hundred packets, as test sequences are only ∼ 1...
Conference Paper
Full-text available
Visual appeal (VA), as judged by users accessing different websites, has been shown to impact overall user preferences and satisfaction. In the context of Web Quality of Experience (QoE), we hypothesize that VA has a non-trivial impact on end user quality perception and hence needs to be accounted for when modeling overall Web QoE. In this paper, w...
Conference Paper
Full-text available
In this paper we present a parametric model for audiovisual quality estimation in IPTV and similar services. The proposed model takes advantage of signal characteristics calculated at the sender (in particular related to levels of motion in the content), but is purely parametric on the estimation (i.e. it does not require peeking into the bitstream...
Conference Paper
Full-text available
It is our pleasure to welcome you to QoMEX 2013, the Fifth International Workshop on Quality of Multimedia Experience, in Klagenfurt am Wörthersee, Austria.
Conference Paper
Multimedia service providers and operators need tools that can estimate the quality of the services delivered to their end-customers. To this end, a variety of quality prediction models has been developed. The models are typically built and trained based on data acquired from user studies conducted in laboratories with precisely defined conditions....
Conference Paper
Full-text available
Nowadays service providers focus all their effort on customers' satisfaction although determining the Quality of Experience (QoE) is not a trivial task. In addition, the evolution from traditional networks towards Next Generation Networks (NGN) is enabling service providers to deploy a wide range of multimedia services such as Internet Television (...
Conference Paper
Full-text available
This paper introduces a network access point (AP) control solution in the context of over-the-top (OTT) multimedia services. The solution is designed to provide network-level management mechanisms for packet traffic while using Quality of Experience (QoE) as a performance indicator. The results showed that with customer subscription scheme, traffic...
Article
Full-text available
This special issue cannot be produced without the effort of all the authors that responded to the call for papers and the work of the external reviewers. We are grateful to all of them.
Article
Recently, network researchers have taken a great interest in quality of experience (QoE) and in the new aspects it brings in the study of the link between network conditions and user satisfaction. Also, the realization that the information of users’ satisfaction can be directly applied in the network management in a real-time manner has resulted in...
Article
Full-text available
For several years now, the ITU-T's Perceptual Evaluation of Speech Quality (PESQ) has been the reference for objective speech quality assessment. It is widely deployed in commercial QoE measurement products, and it has been well studied in the literature. While PESQ does provide reasonably good correlation with subjective scores for VoIP applicatio...
Conference Paper
Full-text available
The quality of experience (QoE) is one of the main research lines in ITC industry, which seeks to manage quality as perceived by users. This document analyzes and describes requirements of a QoE driven management system architecture, which has been designed in the Celtic IPNQSIS project. The architecture is grouped into different levels: Data acqui...
Conference Paper
Understanding and modeling the wide range of influence factors that impact end user Quality of Experience (QoE) and go beyond traditional Quality of Service (QoS) parameters has become an important issue for service and network providers, in particular for new and emerging services. In this paper we present a generic ARCU (Application-Resource-Cont...
Conference Paper
Full-text available
One of the most interesting applications of single-sided Quality of Experience (QoE) metrics is their use in improving the quality of the service, as perceived by the user. This can be done either at the application level-by for example changing the encoding in use, or the level of error correction applied-or at the network level, for instance by c...
Article
Full-text available
While the layered OSI model for networks provides a very clean conceptual framework for network design, certain applications are not completely indifferent to what happens at the lower layers. This is particularly true for multimedia and other real–time applications, which usually have stringent constraints on network performance in order to delive...
Conference Paper
While the layered OSI model for networks provides a very clean conceptual framework for network design, certain applications are not completely indifferent to what happens at the lower layers. This is particularly true for multimedia and other real-time applications, which usually have stringent constraints on network performance in order to delive...