QoS: Measurement and Evaluation of Telecommunications Quality of Service / Edition 1 available in Hardcover
- Pub. Date:
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.
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About the Author
William C. Hardy is the author of QoS: Measurement and Evaluation of Telecommunications Quality of Service, published by Wiley.
Read an Excerpt
Chapter 2: Measurement and Evaluation
2.1 Function of Measurement and EvaluationWhat is suggested here, then, is that analysis is a process whose ultimate end is to produce specific answers to specific questions. This point of view is predicated on the modest assertion that:
- The only good reason to measure anything is to reduce uncertainty with respect to some course of action that must be decided.
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:
- Audience: which decision-makers are to be supported by the results of the analysis?
- Utility: what kinds of decisions are to be facilitated? How must measurements be evaluated to produce information that can be used for those decisions?
- Concerns: what are the questions that those decision-makers are likely to want to have answered during the course of making those decisions?
- Objectives: what are the courses of action that will be decided or determined by appeal to the results of the analysis?
2.1.1 Audience and UtilityTo appreciate the importance of addressing these questions at the outset, consider first the diversity of possible audiences for analyses of quality of telecommunications services. As described below, there are at least five distinct classes of decision-makers who might be responsible for actions whose efficacy depends on reliable information of likely user perception of QoS, and the evaluation of measures needed to make the results of the analysis useful to the decision-makers is in each case different.
(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:
- Assurances that a service that has not been experienced, such as a new offering, a less expensive substitute for an existing service of the same kind, or a similar service based on new technology is likely to be found to be satisfactory; or
- Assurances that a service that has been experienced and found to be unsatisfactory will be put right and no longer exhibit the type, severity, or incidence of problems that rendered it unsatisfactory in the first place.
- What is the likelihood that users of a service exhibiting the value x for the QoS measure MP, will find the service to be satisfactory with respect to the attribute measured by MP?
- What is the smallest value x for the QoS measure MP that will keep complaints from my user community as to the quality of service with respect to the attribute measured by MP at manageable levels?
(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):
- What does the difference between the value x for the QoS measure MP for the service we sell and the value y for a competing service really mean to users? Will it be noticeable? Will any noticeable differences be great enough to alter the users' synthesis of their experience to produce an assessment of perceived QoS?
- What values of the measure of intrinsic QoS, M;, will indicate likely user dissatisfaction with the perceived quality of the attributes of service of concern to users affected by the characteristic of operational system performance measured by Mi?
(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:
- What value, x, of the measure of intrinsic QoS, M;, is an upper/lower limit for what must be achieved in the system design to assure the ability to deliver acceptable perceived QoS?
Table of Contents
Measurement and Evaluation.
The Analysis Process.
EVALUATIVE CONCEPTS, MEASURES, AND QUANTIFIERS.
Connection Quality -
Connection Quality -
The Other Stuff.
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:
- Imagine myself using the system I was studying;
- Decide what I would be concerned about if I were using it;
- Research the technology of the system to the extent necessary to under stand the mechanisms affecting performance of the system with respect to those concerns; and
- Formalize the relationships between system performance and user percep tion of quality of service gleaned from this drill.
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:
- My marketing and sales forces would know how to communicate with customers in a way that would demonstrate their understanding of customers' concerns;
- My system engineers would know how to design my networks to satisfy customer expectations, rather than simply meet industry design standards;
- My operations managers would know the comfortable levels of performance affecting quality of services that must be achieved and maintained to assure user satisfaction;
- My service technicians would know how to troubleshoot user complaints with the same competence that they identify, diagnose, and correct technical problems; and
- Everyone involved anywhere in the company would have a very good idea of exactly how their day-to-day activities affect user perception of the quality of our services.
William C. Hardy