From Measurements to Modeling The Trade-off between Energy Efficiency and System Performance

In this thesis, the work is based on experimental and modeling methodologies. I applied this starting from measurements of Asymmetric Digital Subscriber Line (ADSL) technology, which is the preferred high-speed access to the Internet. The work focuses on the problem of determining the maximum stable bandwidth that an Internet Service Provider (ISP) can offer. This task was accomplished by monitoring and analyzing a large set of ADSL end-users. Huge amount of collected data allowed us to get a detailed statistical analysis of the behavior of ADSL lines, such as the distribution, variable dependencies and correlation of effective bitrate with the physical measurements exposed by network devices. Analysis of collected data suggest that there is no clear trend to predict a downstream bandwidth of ADSL line based on line conditions, and thus requires an intelligent way of analyzing the ADSL lines. Thus, a Neural Network (NN) was employed, which is an intelligent machine learning tool to (i) learn the behavior of ADSL lines, (ii) extract useful information from huge set of measurements, (iii) automatically suggest maximum stable bandwidth. The results indicate that NN performs well in predicting end-users available bandwidth. However, NN is required to be properly trained, as well as needs careful selection of design parameters. Later, the focus of the work was centered over the energy efficiency of telecommunication systems using mathematical modeling approach. Motivation of first work was to know how much energy efficient is Voice over Internet Protocol (VoIP) architecture as compared to traditional Public-Switched Telephone Network (PSTN) architecture used for voice communication. To answer this, these two architectures already implemented at our campus were extensively examined by means of measuring real power consumption. To generalize or estimate power consumption for any given number of users, a mathematical model of power consumption for both the architectures is built. The results indicate that VoIP architecture consumes a lot of power, yet VoIP system have the flexibility to be made energy efficient by adding some sort of energy-wise schemes. The last part of the work investigates the interaction between the Transmission Control Protocol (TCP) and rate adaptation mechanism. Where rate adaptation is an approach to save energy by adapting the transmission rates or capacity according to traffic dynamics. To have deep insight of the interaction, a mathematical model based on fluid based framework is built to depict the behavior of TCP and rate adaptation scheme. The model is then tested for its accuracy and stability by conducting simulation experiments and steady state analysis. Later, the model is used to study the impact of tuning the parameters on system performance. The results suggest that the implementation of rate adaptation scheme can be effective but a careful parameter setting is needed to avoid undesired disruptive interaction among controllers at different levels, that impair QoS

From Measurements to Modeling The Trade-off between Energy Efficiency and System Performance

In this thesis, the work is based on experimental and modeling methodologies. I applied this starting from measurements of Asymmetric Digital Subscriber Line (ADSL) technology, which is the preferred high-speed access to the Internet. The work focuses on the problem of determining the maximum stable bandwidth that an Internet Service Provider (ISP) can offer. This task was accomplished by monitoring and analyzing a large set of ADSL end-users. Huge amount of collected data allowed us to get a detailed statistical analysis of the behavior of ADSL lines, such as the distribution, variable dependencies and correlation of effective bitrate with the physical measurements exposed by network devices. Analysis of collected data suggest that there is no clear trend to predict a downstream bandwidth of ADSL line based on line conditions, and thus requires an intelligent way of analyzing the ADSL lines. Thus, a Neural Network (NN) was employed, which is an intelligent machine learning tool to (i) learn the behavior of ADSL lines, (ii) extract useful information from huge set of measurements, (iii) automatically suggest maximum stable bandwidth. The results indicate that NN performs well in predicting end-users available bandwidth. However, NN is required to be properly trained, as well as needs careful selection of design parameters. Later, the focus of the work was centered over the energy efficiency of telecommunication systems using mathematical modeling approach. Motivation of first work was to know how much energy efficient is Voice over Internet Protocol (VoIP) architecture as compared to traditional Public-Switched Telephone Network (PSTN) architecture used for voice communication. To answer this, these two architectures already implemented at our campus were extensively examined by means of measuring real power consumption. To generalize or estimate power consumption for any given number of users, a mathematical model of power consumption for both the architectures is built. The results indicate that VoIP architecture consumes a lot of power, yet VoIP system have the flexibility to be made energy efficient by adding some sort of energy-wise schemes. The last part of the work investigates the interaction between the Transmission Control Protocol (TCP) and rate adaptation mechanism. Where rate adaptation is an approach to save energy by adapting the transmission rates or capacity according to traffic dynamics. To have deep insight of the interaction, a mathematical model based on fluid based framework is built to depict the behavior of TCP and rate adaptation scheme. The model is then tested for its accuracy and stability by conducting simulation experiments and steady state analysis. Later, the model is used to study the impact of tuning the parameters on system performance. The results suggest that the implementation of rate adaptation scheme can be effective but a careful parameter setting is needed to avoid undesired disruptive interaction among controllers at different levels, that impair Qo

Traffic Profiles and Performance Modelling of Heterogeneous Networks

This thesis considers the analysis and study of short and long-term traffic patterns of heterogeneous networks. A large number of traffic profiles from different locations and network environments have been determined. The result of the analysis of these patterns has led to a new parameter, namely the 'application signature'. It was found that these signatures manifest themselves in various granularities over time, and are usually unique to an application, permanent virtual circuit (PVC), user or service. The differentiation of the application signatures into different categories creates a foundation for short and long-term management of networks. The thesis therefore looks from the micro and macro perspective on traffic management, covering both aspects. The long-term traffic patterns have been used to develop a novel methodology for network planning and design. As the size and complexity of interconnected systems grow steadily, usually covering different time zones, geographical and political areas, a new methodology has been developed as part of this thesis. A part of the methodology is a new overbooking mechanism, which stands in contrast to existing overbooking methods created by companies like Bell Labs. The new overbooking provides companies with cheaper network design and higher average throughput. In addition, new requirements like risk factors have been incorporated into the methodology, which lay historically outside the design process. A large network service provider has implemented the overbooking mechanism into their network planning process, enabling practical evaluation. The other aspect of the thesis looks at short-term traffic patterns, to analyse how congestion can be controlled. Reoccurring short-term traffic patterns, the application signatures, have been used for this research to develop the "packet train model" further. Through this research a new congestion control mechanism was created to investigate how the application signatures and the "extended packet train model" could be used. To validate the results, a software simulation has been written that executes the proprietary congestion mechanism and the new mechanism for comparison. Application signatures for the TCP/IP protocols have been applied in the simulation and the results are displayed and discussed in the thesis. The findings show the effects that frame relay congestion control mechanisms have on TCP/IP, where the re-sending of segments, buffer allocation, delay and throughput are compared. The results prove that application signatures can be used effectively to enhance existing congestion control mechanisms.AT&T (UK) Ltd, Englan

The 30/20 GHz fixed communications systems service demand assessment. Volume 2: Main report

A forecast of demand for telecommunications services through the year 2000 is presented with particular reference to demand for satellite communications. Estimates of demand are provided for voice, video, and data services and for various subcategories of these services. The results are converted to a common digital measure in terms of terabits per year and aggregated to obtain total demand projections

Critical Connections: Communication for the Future

The U.S. communication infrastructure is changing rapidly as a result of technological advances, deregulation, and an economic climate that is increasingly competitive. This change is affecting the way in which information is created, processed, transmitted, and provided to individuals and institutions. The report analyzes the implications of new communication technologies for business, politics, culture, and individuals, and suggests possible strategies and options for congressional consideration