EBU • UER - Technical Review

EBU Technical Review : No. 278 (Winter 1998)

Signal analysis using transforms

A central goal in signal analysis is to extract useful information from signals, such as those representing speech and images, in order to achieve a better understanding of the underlying physical phenomena. However, another vital use of signal analysis is to find compact representations of such signals, so that they can be stored and transmitted more readily - a goal being pursued fervently in the broadcasting world and elsewhere.

The methods of analyzing signals are many, ranging from classical Fourier analysis to various types of linear time-frequency transforms, and from model-based to non-linear approaches. This book concentrates mainly on transform methods.

The first five chapters cover the classical concepts of signal representation. Chapter 1 contains an introduction to signals and signal spaces: it explains the basic tools for classifying signals and describing their properties. Chapter 2 provides an introduction to integral signal representation (e.g. Fourier, Hartley and Hilbert transforms), and Chapter 3 discusses the concepts and tools for discrete signal representation. Examples of discrete transforms are given in Chapter 4, while the following chapter is devoted to the processing of stochastic processes, using discrete transforms and model-based approaches.

The remaining four chapters are dedicated to transforms that provide time-frequency signal representations. A complete chapter is focused on filter banks, which are arrangements of low-pass, band-pass and high-pass filters used for the spectral decomposition and composition of signals. They play an important role in many modern signal-processing applications such as audio and image coding.

Another chapter is dedicated to the wavelet transform. Wavelets have generated a tremendous amount of interest over the past few years, in many fields of science. The number of researchers continues to grow, so progress with this transform is being made at a rapid pace. In fact, advancements in the area are occurring at such a rate that the very meaning of "wavelet analysis" keeps changing to incorporate new ideas. The wavelet transform has many useful features including: a time-frequency resolution that is matched to many real-world phenomena; a multiscale representation, and a very efficient implementation based on multi-rate filter banks.

Chapter 8 discusses the continuous wavelet transform, the discrete wavelet transform, and the wavelet transform of discrete-time signals. The final chapter is devoted to quadratic time-frequency analysis tools such as Wigner distribution, the distributions of Cohen's class, and the Wigner-Ville spectrum.

Although described as an introduction to the topic, this book contains many complex equations. It is aimed mainly at signal-processing engineers, and researchers, students and lecturers in electrical and computer engineering.

Signal Analysis: Wavelets, Filter Banks, Time-Frequency Transforms and Applications
Alfred Mertins
Hardback volume of 317 pages
John Wiley and Sons, UK, 1999
Ref: ISBN 0-471-98626-7. Price £55.00

Mostafa Bibak

Network communications

Modeling and Simulating Communication Networks is a series of laboratory experiments using network analysis software tools from "Modeling Technologies for the Third Millennium" (MIL3): OPNET. The book has identified a niche in the teaching of network communications where the theory of network protocols can be simulated in a practical environment. The author seeks to bridge the gap between this theory and practice, by implementing particular network protocols and network design parameters, and examining the associated trade-offs.

The book is aimed at students of network communications and it recommends that it be used in conjunction with a text on network communications. It comes with a CD-ROM that contains all the on-line documentation (in Acrobat PDF format) for the OPNET software package.

The book is divided into a series of practical exercises on particular areas of communication networks. It starts with a guide to the features of OPNET that are required for carrying out these exercises. The first of these exercises, described in Chapter 2, is basically an exercise in using the software to design a simple communications network. Subsequent chapters deal with other types of protocols in communications networks.

Chapter 3 describes exercises using Automatic Request Repeat protocols that are examples of issues involved in the data-link layer of a communications network. Chapter 4 deals with multiple access protocols, which would be typical of what are termed "broadcast channels" such as Ethernet. Chapter 5 is about "Frame Delay", which is a connection-oriented packet-switched protocol used to pass information across digital interfaces, and which operates at the two lower layers of the OSI (Open Systems Interconnection) reference model. Chapter 6 is a series of laboratory exercises on FDDI (Fibre Distributed Data Interface), a general purpose network protocol operating at 100 Mbits/s. It examines the key parameters in an FDDI network and seeks to investigate trade-offs in the design of such networks. Chapter 7 examines a set of models dealing with a single critical resource in a network and examines the interaction between this and the network traffic.

Each of the experiments is well described in the book. Important in any series of laboratory exercises is how well structured and relevant they are. The book presents a good series of rounded exercises, dealing with many of the key areas of network communications. In each exercise, the author offers extensions which allow those using the book to examine each topic in greater detail.

In conclusion, Modelling and Simulating Communication Networks is a well-structured series of experiments using the OPNET software from MIL3. It is aimed at students of communications networks, and where the OPNET software is installed, it can be a useful companion to a theory-based network communications course.

Modeling and Simulating Communication Networks
Irene Katzela
Bound volume of 116 pages
Prentice Hall, New Jersey, 1999
Ref: ISBN 0-13-915737-1

Peter McAvock

Information and communication technologies

This is a very nice reference book on the digital information and communication technologies that are widely used today to achieve convergence of the audio, video and data media. Available only in German, the text is based on several two-year university/college courses that the author has developed over a period of time. These courses are aimed at students in economics, to give them a better understanding of the objectives being pursued in the development of these new technologies.

What is new and unusual with this book is that it summarizes many complex technical issues – without going too much into detail, but always putting emphasis on the functionality that the technology is aiming at. Objectives to be achieved thus become easily understandable and one can view the issues covered in the context of complete systems or network architectures. This makes the book not only suitable as a powerful learning tool for the target group it was initially created for, but also for professionals working at the management level of an enterprise; the general up-to-date technical knowledge that the book offers is usually much needed by such professionals but isdifficult to attain for the individual, due to the limited time that such people can spend on learning about issues other than those of immediate concern.

Literature on this subject matter is usually very complex, which greatly limits its accessibility to non-specialists in this area. The author is very much aware of this and what he presents in this book does not have the same disadvantage. He has clearly spent much time in collecting and extracting the information from many other and definitely much-more-complex reference sources. Each chapter contains a list of those sources for further reading and to this is usually added a list of Internet web sites that are recognized as giving new updated reference material, specifically in the field of standards and specifications. It is also interesting to note that all 11 chapters of the book extensively use informative charts or other illustrative material. Furthermore, each little paragraph or section has a well-identified summary, consisting of one or two phrases which describe the key issues being dealt with in that section. Only reading these alone will readily provide the reader with a quick overview of what this book is all about.

The book starts with two chapters covering the strategic and theoretical issues that relate to the terms "information" and "communication". The next section (chapters three to five) deals with the basic functionality of the computer technology used for databases, and by the intranet of an enterprise. The following section (chapters six to nine) deals with telephone networks used for wide-area communication, ATM networks and also Internet technologies.

The last two chapters deal with what probably interests us most in the broadcasting environment – the up-coming convergence of various media (i.e. audio, video and data services) within the new means now available for their distribution: DVD, ATM, DAB and DVB. The problems relating to the use of data compression techniques in these digital technologies are also well explained. As already mentioned, the book concentrates only on the applied principles, leaving the related technical details mostly aside. This makes it very pleasant to use this unusual book, which can be much recommended to those interested in this type of reference source.

Information & Kommunikation: Technik und Anwendung in Wirtschaft und Medien
Hardbound volume of 507 pages
Springer, Berlin, 1998
Ref: ISBN 3-540-64057-6

Dietmar Kopitz