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Quality of Service (QoS) is continuously growing in importance in the telecommunications industry because competition is growing fiercer by the day. By drawing on 30 years of experience, William C. Hardy explains how to examine specific tools and techniques that he has developed for the measurement and evaluation of QoS and understand the underlying analysis perspectives and methodologies.
Details the basic concepts of QoS, together with the methodologies for organizing, structuring, and carrying out analyses of QoS from scratch.
Describes the atttributes of the telecommunications service that determine user perception of quality in non-technical terms.
Discusses specific measures, measurement techniques and evaluation criteria for all of the factors that affect user perception of QoS.
Addresses user concerns including:
* Will I be able to get to the service when I want to use it?
* How long does it take before I know a connection is being set up?
* How good will voice sound over a connection?
* Includes valuable tips for QoS analysis and the perspectives vital for describing QoS in ways that are useful and operationally meaningful.
Whether you have a limited technical background or are a telecommunications professional this simple and straightforward approach will be an essential tool to understanding QoS.
The principal value of this concept of the function of measurement and evaluation is that it readily suggests a number of questions that the analyst should address before undertaking any analysis. These include questions of:
(1) Service users. The most obvious class comprises the actual users of the service, who are continually testing its quality by placing calls. The principal uncertainties that they face are ones of how often they will encounter problems that materially impede the act of placing a call and completing the desired exchanges of information. Consequently, users will be very conscious of any difficulties experienced and will synthesize that experience over time to determine whether the incidence and severity of problems actually encountered is acceptable, thereby producing a subjective assessment of perceived quality. On the basis of that subjective assessment, a user then decides tentatively that the service is satisfactory or unsatisfactory. If it is unsatisfactory, the user will initially complain, and then later abandon the service, if the is no improvement. If the service is tentatively found to be satisfactory, the user continues its use and continues to synthesize the experience with it to verify the original subjective assessment. As long as the assessment does not change, the user remains satisfied. However, perceptible changes in the type, incidence, severity, or user's accommodation of problems with the service may result in a different assessment of perceived quality, leading the user to decide to complain about or change the service, when possible. As a possible audience for results of QoS analyses, then, users will be looking for results providing reassurances with respect to uncertainties as to what will be experienced in the unknown future. Such reassurances sought will be of one of two kinds:
(3) Service provider sales and marketing personnel. On the other side of the fence, one of the major consumers of QoS analyses will be the sales and marketing personnel, who are not necessarily decision-makers, but must respond to the concerns with QoS raised by the users and Comm Managers who are their prospective customers. Because of their role in telling prospective customers about telecommunications services, they will want whatever the customer wants, but with the additional feature that the analyses must also show how quality of the services they sell compares with that of competing services offered by other providers. Because of the need to characterize, communicate, and interpret any differences in measures of QoS between the competing telecommunications services, their principal questions with respect to evaluation of QoS is usually (or by all means should be):
(5) System architects and engineers. Last on our list of possible consumers of QoS measurement and evaluation are the persons who must make the decisions as to the technology to be employed in implementing various telecommunications services and the way various assets are to be configured to deliver particular services. Like operations and maintenance personnel, the system architects and engineers are concerned with intrinsic quality. Unlike operations and maintenance personnel, who are constrained to manage performance within the constraints of the existing system and resources, the architects and engineers are responsible for deciding the characteristics of the telecommunications system and the allocation of resources that will achieve intrinsic quality adequate to assure a high likelihood that perceived quality will be acceptable. To do this, they must have hard and fast requirements that can be used as the basis of system design and configuration. Notions of subjectivity and perception must be totally factored out of the equations, and the fuzzy indicators that might be used for operations and maintenance management must be replaced by criteria for acceptability of variations of intrinsic quality that are technical, concrete, specific and completely unambiguous. The need for such criteria, then, generates questions of the form:
Measurement and Evaluation.
The Analysis Process.
EVALUATIVE CONCEPTS, MEASURES, AND QUANTIFIERS.
Connection Quality -
Connection Quality -
The Other Stuff.
The Quality of Service Development Group (QSDG) is a field trial group of QoS professionals from over 130 carriers, service providers, research companies and vendors from around the world. While informal, we operate under the auspices of Study Group 2 of the ITU-T. We gather annually in different geographic regions to discuss QoS issues within our companies. QSDG Magazine (www.qsdg.com) which as well as being our group's official magazine, is also the only periodical in the world about QoS, and is distributed in 201 countries and territories.
William C. "Chris" Hardy is unquestionably among the leading lights in the field of QoS. As chairman of the QSDG I appreciate the contributions Chris has made, both to the QSDG group as a whole, and through his QDSG Magazine column Telecom Tips and Quality Quandaries, on which much of this book is based. If you are coming to grips with QoS in your company, this is the place to start.
Luis Sousa Cardoso
1. The credible, reliable assessment of the likelihood that users will find a particular service to be satisfactory; and
2. The determination of how system performance must be changed when that assessment shows that users are not likely to be satisfied.
This kind of complementary utility in a measurement scheme is not hard to achieve. However, it is, in fact, frequently absent in proposed quality of service (QoS) metrics, because definition and development of particular measures have failed to take into account both the concerns of the users of telecommunications services and the perspectives of the engineers and technicians who must design, build, and operate the systems that deliver those services. It is, therefore, a secondary, but equally important objective of this book to describe the analytical perspectives and discipline that have reliably guided the development of the specific measures that are presented here. To this end, the material in this book is divided into two parts:
This structure allows for a variety of approaches to the material.
Persons who are conversant with telecommunications services and QoS measurement may choose to begin with Part II, and then revert to Part I for purposes of understanding the perspectives that supported development of the measures. Alternatively, a seasoned QoS analyst might read through Part I and readily acquire an understanding of the analytical discipline and techniques sufficient for purposes of developing measures for new services that are useful both to service users and to telecommunications system operators and engineers. Finally, persons with lesser background and experience in QoS will find that reading Part I first to get the grounding in the basics will make it much easier to follow the reasoning that justifies the selection of the measures described in Part II as being particularly well-suited for purposes of measuring and analyzing the particular aspect of QoS each describes.
Whatever the background and experience of the reader, I hope that this book shall clearly convey, both by force of reasoning and by example, three principles to be applied in defining and developing measures of QoS:
Because my career started with such a complete lack of practical experience and technical skills, my analytical efforts have never been marred or impeded by technical expertise or conventional wisdom. Rather, what I discovered was that all I really needed to do to be effective as a problem solver in this area was to:
This book is based on more than 30 years experience in successfully applying this approach in analyzing issues of quality of service of telecommunications systems to produce practicable solutions to quality problems. Because of the very basic nature of the approach, this book is apt to be viewed by some as being short on technical content and long on formulation of evaluative concepts and generic measures. However, I refuse to apologize for this, because the perspectives on quality of telecommunications services that I am trying to lay out here are exactly those that I would want all of my employees to share, were I ever to become the CEO of a telecommunications company, so that, for example:
William C. Hardy