Empirical Data from Mobile and IP Telephony

Over the recent years enormous changes in the telecommunication services, techniques, regulations and markets have taken place. However, even with many new exciting services the telephony service is still popular. This paper provides empirical traffic data and observations of telephony traffic patterns in mobile and IP telephony. They are presented and compared with old telephony patterns from Public Switched Telephone Networks (PSTN). The question is whether the characterization of telephony traffic should be reconsidered because new technology and markets might have changed the service and usage. How is the telephony usage patterns influenced by technology changes from fixed to mobile phones, changes in quality from fixed-line phone to mobile and IP telephone, changes in tariffs from usage based to flat-rate subscriptions, and appearance of alternative message based communication means? This paper presents a comparison between recent mobile and IP telephony measurements and telephony measurement obtained nearly four decades ago. The traffic patterns are compared and significant changes in the daily and weekly traffic profiles are observed. In particular, the profile of international calls has significantly changed and does not resemblance any of the standard traffic profiles from ITU E.523. The busy hour call holding times are fitted a log-Normal distribution for domestic and Hyper Exponential for international calls. Furthermore, the average call holding times show significant variations over the day in flat-rate subscriptions. Finally, the results indicate that the Short Message Service (SMS) seems to serve as a supplement to phone calls, in particular in the evenings, which might change call holding time distribution and traffic intensities

STOCHASTIC MODELING AND TIME-TO-EVENT ANALYSIS OF VOIP TRAFFIC

Voice over IP (VoIP) systems are gaining increased popularity due to the cost effectiveness, ease of management, and enhanced features and capabilities. Both enterprises and carriers are deploying VoIP systems to replace their TDM-based legacy voice networks. However, the lack of engineering models for VoIP systems has been realized by many researchers, especially for large-scale networks. The purpose of traffic engineering is to minimize call blocking probability and maximize resource utilization. The current traffic engineering models are inherited from the legacy PSTN world, and these models fall short from capturing the characteristics of new traffic patterns. The objective of this research is to develop a traffic engineering model for modern VoIP networks. We studied the traffic on a large-scale VoIP network and collected several billions of call information. Our analysis shows that the traditional traffic engineering approach based on the Poisson call arrival process and exponential holding time fails to capture the modern telecommunication systems accurately. We developed a new framework for modeling call arrivals as a non-homogeneous Poisson process, and we further enhanced the model by providing a Gaussian approximation for the cases of heavy traffic condition on large-scale networks. In the second phase of the research, we followed a new time-to-event survival analysis approach to model call holding time as a generalized gamma distribution and we introduced a Call Cease Rate function to model the call durations. The modeling and statistical work of the Call Arrival model and the Call Holding Time model is constructed, verified and validated using hundreds of millions of real call information collected from an operational VoIP carrier network. The traffic data is a mixture of residential, business, and wireless traffic. Therefore, our proposed models can be applied to any modern telecommunication system. We also conducted sensitivity analysis of model parameters and performed statistical tests on the robustness of the models’ assumptions. We implemented the models in a new simulation-based traffic engineering system called VoIP Traffic Engineering Simulator (VSIM). Advanced statistical and stochastic techniques were used in building VSIM system. The core of VSIM is a simulation system that consists of two different simulation engines: the NHPP parametric simulation engine and the non-parametric simulation engine. In addition, VSIM provides several subsystems for traffic data collection, processing, statistical modeling, model parameter estimation, graph generation, and traffic prediction. VSIM is capable of extracting traffic data from a live VoIP network, processing and storing the extracted information, and then feeding it into one of the simulation engines which in turn provides resource optimization and quality of service reports

A Bayesian approach to Hybrid Choice models

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2010-2011Les modèles microéconométriques de choix discrets ont pour but d’expliquer le processus du choix individuel des consommateurs parmi un ensemble limité et exhaustive d’options mutuellement exclusives. Les modèles dits de choix hybrides sont une généralisation des modèles de choix discrets standard, où des modèles indépendants plus sophistiqués sont considérés simultanément. Dans cette thèse des techniques d’estimation simultanée sont analysées et appliquées pour un modèle de choix hybride qui, sous la forme d’un système complexe d’équations structurelles généralisées, intègre à la fois des choix discrets et des variables latentes en tant que facteurs explicatifs des processus décisionnels. Ce qui motive l’étude de ce genre de modèles est que pour comprendre le processus du choix il faut incorporer des attitudes, des perceptions et des attributs qualitatifs à l’intérieur de modèles décisionnels économiques conventionnels, tout en prenant ce qui dit la recherche en sciences cognitives ainsi qu’en psychologie sociale. Quoique l’estimation du système d’équations d’un modèle de choix hybride requière l’évaluation d’intégrales multidimensionnelles complexes, on résoudre empiriquement ce problème en applicant la méthode du maximum de vraisemblance simulée. Ensuite on dérive une procédure d’échantillonnage de Gibbs pour l’estimation simultanée bayésienne du modèle qui offre des estimateurs convergents et efficaces. Ceci devient une méthode plus avantageuse comparativement aux méthodes classiques dans un cadre analytique avec un grand nombre de variables latentes. En effet, en vertu de l’approche bayésienne il suffit de considérer des régressions ordinaires pour les variables latentes. Par ailleurs, dériver les intervalles de confiance bayésiennes pour les parts de marché ainsi que pour des dispositions à payer devient trivial. De par sa grande géneralité, le modèle de choix hybride est capable de s’adapter à des situations pratiques. En particulier, la réponse des consommateurs suite à l’innovation technologique est analysée. Par exemple, on étudie les préférences pro-environnementales dans un modèle économique des décisions d’achat de véhicules verts selon lequel les consommateurs soucieux de l’environnement sont prêts à payer davantage pour des véhicules à faibles émissions, en dépit des inconvénients potentiels. En outre, en utilisant un noyau probit et des indicateurs dichotomiques on montre que des connaissances préalables ainsi que des attitudes positives envers l’adoption de nouvelles technologies favorisent l’adoption de la téléphonie IP.Microeconometric discrete choice models aim to explain the process of individual choice by consumers among a mutually exclusive, exhaustive and finite group of alternatives. Hybrid choice models are a generalization of standard discrete choice models where independent expanded models are considered simultaneously. In my dissertation I analyze, implement, and apply simultaneous estimation techniques for a hybrid choice model that, in the form of a complex generalized structural equation model, simultaneously integrates discrete choice and latent explanatory variables, such as attitudes and qualitative attributes. The motivation behind hybrid choice models is that the key to understanding choice comes through incorporating attitudinal and perceptual data to conventional economic models of decision making, taking elements from cognitive science and social psychology. The Bayesian Gibbs sampler I derive for simultaneous estimation of hybrid choice models offers a consistent and efficient estimator that outperforms frequentist full information simulated maximum likelihood. Whereas the frequentist estimator becomes fairly complex in situations with a large choice set of interdependent alternatives with a large number of latent variables, the inclusion of latent variables in the Bayesian approach translates into adding independent ordinary regressions. I also find that when using the Bayesian estimates it is easier to consider behavioral uncertainty; in fact, I show that forecasting and deriving confidence intervals for willingness to pay measures is straightforward. Finally, I confirm the capacity of hybrid choice modeling to adapt to practical situations. In particular, I analyze consumer response to innovation. For instance, I incorporate proenvironmental preferences toward low-emission vehicles into an economic model of purchase behavior where environmentally-conscious consumers are willing to pay more for sustainable solutions despite potential drawbacks. In addition, using a probit kernel and dichotomous effect indicators I show that knowledge as well as a positive attitude toward the adoption of new technologies favor the adoption of IP telephony

The Measure and Regulation of Competition in Telecommunications Markets

The development of the canadian telecommunications web is significantly influenced by the regulatory framework put in place to oversee the evolution of the web toward a competitive system. This paper has two specific objectives: first, to develop a methodological framework, which will allow a proper characterization of the level of competition in the telecommunications industry, more specifically in the residential local access market and second, to recommend some (significant) changes in the CRTC approach to the regulation of the Canadian Telecommunications industry. I argue that the current approach to the regulation of telecommunications in Canada is likely to generate significant harms to consumers and businesses as well as efficiency losses for the Canadian economy. I conclude that there is a urgent need for a telecommunications regulatory reform, with a stronger accent put on three crucial roles of the telecommunications regulator as the trusted generator of information for the consumers, as the manager of the level playing field conditions, and as the promoter of efficient investment programmes. Le développement du réseau canadien des télécommunications est influencé de façon significative par le cadre réglementaire adopté pour régir l’évolution de ce réseau vers la concurrence. Cet article a deux objectifs principaux : d’une part, développer un cadre méthodologique adéquat pour caractériser le niveau de concurrence dans l’industrie des télécommunications, plus particulièrement du marché des services résidentiels locaux, et, d’autre part, de proposer des changements (importants) au cadre réglementaire actuel. Je montre que le cadre réglementaire actuel peut engendrer des problèmes importants pour les consommateurs et l’industrie ainsi que des pertes d’efficacité pour l’économie canadienne. Il existe un besoin urgent de réformer le cadre réglementaire actuel, en mettant l’accent sur trois rôles essentiels de l’agence de régulation des télécommunications comme fournisseur d’informations aux consommateurs, comme gestionnaire des conditions de concurrence loyale pour toutes les entreprises et comme promoteur de programmes d’investissement efficaces.competition, regulatory reform, telecommunications , concurrence, réforme de la réglementation, télécommunication

Broadband prices in the European Union : competition and commercial strategies

This paper analyses the determinants of broadband Internet access prices in a group of 15 EU countries between 2008 and 2011. Using a rich panel dataset of broadband plans, we show the positive effect of downstream speed on prices, and report that cable and fibre-to-the-home technologies are available at lower prices per Mbps than x DSL technology. Operators’marketing strategies are also analysed as we show how much prices rise when the broadband service is offered in a bundle with voice telephony and/or television, and how much they fall when download volume caps are included. The most insightful results of this study are provided by a group of metrics that represent the situation of competition and entry patterns in the broadband market. We show that consumer segmentation positively affects prices. On the other hand, broadband prices are higher in countries where entrants make greater use of bitstream access and lower when they use more intensively direct access -local loop unbundling-. However, we do not find a significant effect of inter-platform competition on prices

Quality aspects of Internet telephony

Internet telephony has had a tremendous impact on how people communicate. Many now maintain contact using some form of Internet telephony. Therefore the motivation for this work has been to address the quality aspects of real-world Internet telephony for both fixed and wireless telecommunication. The focus has been on the quality aspects of voice communication, since poor quality leads often to user dissatisfaction. The scope of the work has been broad in order to address the main factors within IP-based voice communication. The first four chapters of this dissertation constitute the background material. The first chapter outlines where Internet telephony is deployed today. It also motivates the topics and techniques used in this research. The second chapter provides the background on Internet telephony including signalling, speech coding and voice Internetworking. The third chapter focuses solely on quality measures for packetised voice systems and finally the fourth chapter is devoted to the history of voice research. The appendix of this dissertation constitutes the research contributions. It includes an examination of the access network, focusing on how calls are multiplexed in wired and wireless systems. Subsequently in the wireless case, we consider how to handover calls from 802.11 networks to the cellular infrastructure. We then consider the Internet backbone where most of our work is devoted to measurements specifically for Internet telephony. The applications of these measurements have been estimating telephony arrival processes, measuring call quality, and quantifying the trend in Internet telephony quality over several years. We also consider the end systems, since they are responsible for reconstructing a voice stream given loss and delay constraints. Finally we estimate voice quality using the ITU proposal PESQ and the packet loss process. The main contribution of this work is a systematic examination of Internet telephony. We describe several methods to enable adaptable solutions for maintaining consistent voice quality. We have also found that relatively small technical changes can lead to substantial user quality improvements. A second contribution of this work is a suite of software tools designed to ascertain voice quality in IP networks. Some of these tools are in use within commercial systems today

Costs and benefits of superfast broadband in the UK

This paper was commissioned from LSE Enterprise by Convergys Smart Revenue Solutions to stimulate an open and constructive debate among the main stakeholders about the balance between the costs, the revenues, and the societal benefits of ‘superfast’ broadband. The intent has been to analyse the available facts and to propose wider perspectives on economic and social interactions. The paper has two parts: one concentrates on superfast broadband deployment and the associated economic and social implications (for the UK and its service providers), and the other considers alternative social science approaches to these implications. Both parts consider the potential contribution of smart solutions to superfast broadband provision and use. Whereas Part I takes the “national perspective” and the “service provider perspective”, which deal with the implications of superfast broadband for the UK and for service providers, Part II views matters in other ways, particularly by looking at how to realise values beyond the market economy, such as those inherent in neighbourliness, trust and democrac