Book Explains Digital Audio Broadcasting
by Rick Barnes
A recently published book, edited by Wolfgang Hoeg
and Thomas Lauterbach, provides a much-needed primer for the digital
modulation of radio. Released for publication in the United States
in March, "Digital Audio Broadcasting – Principles and
Applications" offers many answers regarding how digital radio
modulation works.
The main focus of the book is the Eureka-147 version
of DAB, currently in operation in Europe, Canada, Australia, Singapore,
China and South Africa, and under development in other Asian nations
including India.
The in-band, on-channel form of digital radio,
now in research and development in the United States, is mentioned
briefly.
Many of the explanations in subsequent chapters
have practical applications to IBOC, Digital Radio Mondiale and
Integrated Services Digital Broadcasting, the Japanese version
of digital radio, as well as Eureka-147.
Essentials
The system concept chapter provides ample descriptions
of the frame structure of DAB, interleaving and Differential Quadrature
Phase Shift Keying, or DQPSK, all of which have applications in
DAB formats other than Eureka-147.
The chapter on audio services and applications
provides an understandable description of audio masking techniques
and the psychoacoustics of human hearing with their application
to bit-rate reduction in digital radio.
The characteristics of MPEG algorithms are provided.
Of particular interest is the description of error protection
and concealment. The Eureka-147 version of DAB provides for an
"ensemble" of audio and ancillary service in the 1.537
MHz of bandwidth of a DAB channel in this scheme. This concept
is introduced in the audio services and applications chapter and
is described in detail in the following chapter.
The chapter concerning data services and applications
tells the story of Eureka-147’s ability to provide ancillary
services in terms of multimedia transmission. These include HTML
pages, JPEG pictures or slideshows and MPEG movies using the MOT,
Multimedia Object Transfer protocol. Eureka-147 is definitely
not radio as we once knew it, and Hoeg and Lauterbach’s book
definitely prepares us for this new and exciting technology.
A chapter titled "Provision of Services"
provides a detailed description of DAB main services – audio
services, program associated data (PAD) and packet mode data –
data services such as the dynamic label format, MOT protocol and
slide shows – broadcast operating systems and editorial systems
with the management of text and service data.
This chapter also speaks of the compatibility of
digital audio broadcasting with the Radio Data System (RDS/RBDS)
and outlines the differences and similarities between DAB and
RDS. It closes with a discussion of audio services aspects concerning
loudness differences within audio services, DAB/FM switching and
DAB ensembles, signal level alignment, metering and control.
Technical details
"Collection and Distribution Networks"
provides block diagrams of the DAB ensemble multiplexer, the layer
structure of the Service Transport Interface (STI) frame descriptions
and the structure of the DAB collection and distribution networks.
In order for this chapter to make much sense, however, a certain
level of understanding regarding computer and telecom network
architecture is required on the part of the reader.
On the broadcast side, a well-defined description
of Single Frequency Networks (SFN), with their ability to provide
power and frequency economy and why they are possible with DAB,
is provided.
This section also describes Coded Orthogonal Frequency
Division Multiplexing, or COFDM, which, again, has a direct application
to IBOC technology as well as Eureka-147. Frequency management
is addressed in this chapter as well as coverage capabilities
and Bit Error Rate.
The book closes with a chapter on the receiving
side of DAB with block diagrams of DAB receivers, channel decoder
architecture and audio decoders. "Digital Audio Broadcasting
– Principles and Applications" provides an extensive
bibliography of standards and related documents, publications
and Internet links for the further study of DAB.
Team effort
Although Wolfgang Hoeg, formerly head of division
at Deutsche Telekom Berkom, and Thomas Lauterbach, a member of
the faculty at the University of Applied Sciences, Nuremberg,
Germany, edited it, many individuals participated in the writing
of this text. The list of contributors indicates 15 distinguished
engineers who provided information for the eight chapters of this
book.
The book served as the primary resource for an
academic paper that I recently wrote for a graduate level course
in "Introduction to Digital Transmission." I am sure
that I will be poring over this book for months.
If you are a broadcast manager, engineer or a student
intent on being involved with radio for the coming years, I encourage
you to do the same. It will serve you well.
"Digital Audio Broadcasting – Principles
and Applications" is a 280-page hardcover, priced at $75
and available from various online booksellers or from the publisher,
John Wiley and Sons Ltd., Chichester, England. Visit www.wiley.co.uk/wileychi/commstech/hoeg.html.
The book’s ISBN number is 0-471-85894-3.
Rick Barnes, CBRE, is a studio engineer and
Internet news specialist with the Voice of America. He is a graduate
student at Capella University, Minneapolis, where he is working
toward a Ph.D. in communications technology.
