The IBOC Handbook. Understanding HD Radio™ Technology

491 Pages·2007·27.168 MB·English

by  David P. Maxson (Auth.)

Acquisitions Editor: Angelina Ward
Project Manager: Mónica González de Mendoza
Assistant Editor: Doug Shults
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Printed in the United States of America.
To Diane—my best friend, wife, and #1 cheerleader—
without whom this book and so much else would not have been possible.
TRADEMARK ATTRIBUTIONS
“iBiquity” and “iBiquity Digital” are trademarks of iBiquity Digital Corporation.
“HD Radio,” “HDC,” and “HD BML” are trademarks of iBiquity Digital Corporation.
The iBiquity Digital corporate logo and HD Radio logo are trademarks of iBiquity Digital Corporation.
Tomorrow Radio is a service mark of National Public Radio.
XM is a trademark of XM Satellite Radio.
Sirius is a trademark of Sirius Satellite Radio.
TiVo is a trademark of TiVo Incorporated.
DRM is a trademark of Digital Radio Mondiale.
DAB is a trademark of the WorldDAB Forum.
Split-Level is a trademark of Harris Corporation.
Cam-D is a trademark of Kahn Communications.
All other trademarks referenced in this book are the property of their respective owners.
Acknowledgments
With an undertaking as large and detail-driven as the IBOC Handbook, it will be hard to know
when to stop offering my gratitude for all the support I have received. First, and foremost, this
book began as a collaboration between myself and Don Lockett, author of “The Road to Digital
Radio In the United States” (NAB, 2004). I am grateful for Don’s input, support and graciousness.
Unfortunately, his professional obligations prevented him from participating as much as we both
would have liked. Chapter 1 contains material Don contributed to the effort.
Chapter 12 is about that black art, AM antennas. I am eternally grateful to Grady Moates of Loud
and Clean Broadcast Science, for providing most of the words and meaning to the chapter. His
facility with the hardware of radio broadcasting is legendary, as should also be his generosity of
spirit. Speaking of legendary, I first met Brian Kroeger, D.Sc., now Chief Scientist of iBiquity
Digital Corporation in 1996, then with Westinghouse Wireless. He was presenting a sober, scien-
tific assessment of what the numbers said IBOC could and could not do, and I was hooked. Since
then, he has overseen the technical team that made this amazing IBOC technology possible. For
me, he has always been helpful and informative. Brian, thanks for carving out a little time here and
there to patiently answer my questions. I hope this book does justice to the technology that you and
your team developed. As well, I want to single out Jeff Detweiler and Ashruf El-Dinary of iBiquity,
and of course, “Mr. IBOC,” Glynn Walden, of CBS, iBiquity, and CBS. They have plenty of work
to do and still found time to respond to my occasional inquiries.
There are so many who have been riding the IBOC wave since it was just a ripple, some of whom
I have had the good fortune to meet or work with. Since I bought my first Shively antenna in
the 1980s, I have counted on Bob Surette to fill in the gaps in my knowledge of antennas and
filters. He has been generous in sharing his experience with IBOC combiners and filters. Jerry
ix
Acknowledgments
Westberg of Broadcast Electronics gave Grady and myself very helpful feedback on Chapter 12.
Richard Hinkle of Broadcast Electronics, Tim Holt of Bird Technologies, Geoff Mendenhall of
Harris, and Eric Wandel, formerly of ERI, whether they know it or not, have been resources for
me on topics in IBOC transmission, even before I embarked on writing this book. In particular,
thanks to Tim Hardy of Nautel, who on several occasions spent valuable time jotting down his
explanations on napkins as we’d talk over signal processing and transmission topics. To my friends
at Impulse Radio, particularly Paul Signorelli and David Corts, thanks for the opportunity to
learn about digital networks while I was showing you the ropes in the broadcast industry. Mike
Bergman of Kenwood U.S.A. Corporation has been an invaluable resource on the receiver side of
the IBOC equation. I also sought advice, generously given, from Michael LeClair, Chief Engineer
of Boston’s WBUR Group, and Editor of Radio World Engineering Extra. Ron Rackley, a titan in
the AM array field, was also responsive to my inquiries. Thanks to each of you, and all that I have
not mentioned.
Also, I salute a good-humored, talented, and professional group—my colleagues who represent
their companies on the NRSC subcommittees—who are too many to name here. They have
helped make my experience with the IBOC process rewarding. I appreciate, as well, the moral
support and technical acumen of the people of the National Association of Broadcasters (NAB)
and the Consumer Electronics Association (CEA). In particular, special thanks go to David Layer
of NAB and David Wilson of CEA for their direct input to my effort.
David Layer also filled the role of Technical Editor. He volunteered to go through the manuscript
with a fine-toothed comb, weeding out awkward wording, factual errors, unnecessary informa-
tion, and (yes, I admit it) the occasional a-little-too-strident remark. What remains is so much the
better for his input. However, any mistakes and misdirection that the reader may find lurking in
this work are mine. I encourage you, the reader, to let me know what you think about this book.
On the home front, I am indebted to my family for their perseverance through all the time I stole
for writing, and to my colleagues at Broadcast Signal Lab for their dedication to providing good
service to our customers and supporting my effort on this book. To my fantastic wife, Diane and
my fabulous children, Hilary and Scott, thanks for letting me go for it. To my mom the school-
marm and my dad the philatelist, Jane and Irv, you have been good teachers and parents and I am
grateful for the tools you have given me.
On the business side, in particular, to my business partner since 1982, Rick Levy, thanks for your
constancy, technical and moral advice, and wit over the years. This one’s for you:
There once was an astronomer from Brooklyn,
Who came to the halls of Harvard to book-learn;
He studied galaxies and suns,
And littered the cosmos with puns,
But it was the radio waves that really got him cookin’!
My colleague Lew Collins has been a wellspring of knowledge and sage advice; our paths first
crossed a few years ago, and I only wish it had happened sooner. Another colleague, David
x
Acknowledgments
Peabody, has been a good friend and stalwart for nearly our entire careers. Thanks for your loyalty
and independent thinking.
On the production side, let me start with my colleague Aaron Read. We met through a dialog of
dueling IBOC commentaries in Radio World and hit it off right away. When I needed a creative,
technically oriented, visually astute illustrator, you stepped up and made your magic. Aaron
created, and inspired, much of the art in this book. Supporting me in art and manuscript prepara-
tion were Ann Connors and Maureen Whelan. Thanks not only for this work, but also for helping
me keep my hectic day-job schedule while I was also getting the writing done. At the publisher,
Focal Press, I am indebted to Acquisitions Editor Angelina Ward and Assistant Editor Doug
Shults for their patience and persistence as deadlines loomed and were rescheduled.
Bob Struble, Chairman and CEO of iBiquity Digital Corporation, which made the HD Radio
brand of IBOC technology a reality, responded to my lamentation in 2001 regarding the tremen-
dous possibilities of IBOC and its seemingly slow progress at the time. He asked for my patience
and counseled that HD Radio technology would “let a thousand flowers bloom.” Ironically, this
common paraphrase comes from Mao-Zedong’s hundred flowers movement at the beginning of
the cultural revolution, “let a hundred flowers bloom, and a hundred schools of thought contend.”
This book is one of those flowers. Thanks, Bob.
And finally, to you, the reader, nothing is more gratifying than to hear, “I learned something;
thanks.” I hope I have succeeded in putting the pieces of a huge puzzle together in an interesting
way. Check out www.ibocbook.com for what may develop.
David Maxson
June 2007

xi
Introduction
Until this book was written, there has not been a thorough explanation of the inner workings of
the In-Band On-Channel (IBOC) technology in one place. Dozens of articles in the trade press
and technical papers at industry symposiums constitute the IBOC story. It may be hubris on my
part to think that this technology could be wrapped up in a book, but I have done my best to do so.
Using the National Radio Systems Committee (NRSC) IBOC standard (NRSC-5-A) as a frame-
work, this book introduces the complex layers in what makes it work. The reader does not have
to be a digital signal processing engineer. On the contrary, the book is aimed toward individuals
with a technical bent, and a curiosity about digital radio, American style. The first two chapters
set the context and the history of IBOC. In the following chapters, things get more technical.
The book focuses on IBOC, the generic technology that is the subject of the NRSC standard, and
it integrates the specific implementation that is IBOC, the HD RadioTM technology of iBiquity
Digital Corporation.
Several knowledge threads are woven through the book. First, the role of a standard-setting
process is often misunderstood among those who have not participated in one. This book paints a
picture of the rigorous NRSC process that led to the IBOC standard. Second, to create a standard
requires protocols and specifications. As the book steps through the layers of the NRSC-5 protocol
stack, the relationship between what a standard says, and what a manufacturer’s implementation
does, may become apparent. People often ask questions about why a technology works a certain
way, or why a feature hasn’t developed as expected. The answer often lies in the complex relation-
ship between the standard, the equipment manufacturers, the broadcasters, and the consumers
who are both buyers of radios and listeners of them. Broadcast engineers configuring their equip-
ment and programming their transmission gear may have “Aha!” moments when the reasons for
xiii
Introduction
the way things are become apparent. Individuals listening to their IBOC receivers and looking at
their displays may grasp the subtleties that determine what the technology does in today’s receiver
and what the possibilities are for tomorrow.
Third in the book is the subject of digital systems. A protocol stack invokes multidisciplinary
knowledge. In plainer language, as one progresses from the information input at the top of the stack
to the radio signal that comes out the bottom of the stack, the processing tasks require different
types of engineering. Although this book contains a detailed treatment of the IBOC process, it
is also a case study in digital systems. The principles that apply to IBOC apply as well to other
digital communications media. Protocols that define services must have certain characteristics,
while protocols that define transport mechanisms have other characteristics. Often, the features
of tried-and-true technologies are borrowed and molded to the IBOC application—such as char-
acteristics of the Open Systems Interconnection reference model, the functionality of streaming
modem protocols, the use of virtual ports to establish communications, and the like. The design
of an open system also relies on myriad techniques to balance the reliability of the service with the
information rate it can provide. IBOC technology exploits signal processing techniques common
to digital communications in general. This book presents and explores such concepts such as
scrambling, Forward Error Correction (FEC), convolutional coding, Reed-Solomon coding,
frequency diversity, time diversity, pulse shaping, matched filtering, Fourier Transformation,
quadrature modulation, and the like.
In presenting detailed technical information, I attempt to work the concepts in a manner that will
not tax one’s math skills. There are places where math is what it is all about, and the equations are
there to be dissected. However, even where there are equations, it is my hope that the concepts
will still come across if the reader only gives the math a cursory look.
Finally, there should be plenty of “news you can use” for technical people involved in IBOC tech-
nology. The book is populated with useful tables, figures, and lists, as well as explanations of how
to do things on the transmission side of IBOC.
I crave reader feedback. Check out www.ibocbook.com to see how readers can participate.
—David Maxson
xiv
1 IBOC Digital Radio and the
State of the Digital Radio
Industry
Conversion to Digital Radio Broadcasting is well underway in the United States. The arrival
has been accompanied by a series of technological and regulatory events. This book was written
to provide a look at In-Band On-Channel (IBOC) technology from the inside, out. IBOC tech-
nology is also discussed in the context of its implementation by the company that brought it to
market, iBiquity Digital Corporation (iBiquity). Receiver and transmission equipment manufac-
turers make and market numerous products licensed by iBiquity under the “HD RadioTM” brand
name. At points in the book we thresh out the nature of the IBOC transmission protocol and its
relation to products that bear the HD Radio trademark. The first two chapters provide a top-level
view of the context of IBOC. Chapters 3 through 11 go into the nuts and bolts of the National
Radio Systems Committee’s NRSC-5 IBOC standard and how the technology works. The final
portion of the book touches on other aspects of the technology.
In the first section of this first chapter, “What Is IBOC Radio?” we go over the “services” that
are the foundation of IBOC capabilities. In the next section, “The Digital Radio Environment,”
we take a snapshot of the digital radio broadcasting industry to provide a global picture of DAB
and IBOC technology. In “Digital Radio Transmission Technologies” we look at the other tech-
nologies in the arena. Finally, in “A Context for IBOC,” we discuss IBOC in the context of the
regulatory arena and the marketplace, paving the way to Chapter 2.
Following Chapter 2, we dig deeply into the NRSC-5 Standard and the way IBOC works, begin-
ning with an overview of the standard in Chapter 3. Chapters 4 through 11 break out various
components of the standard and explore them in depth.
3
Chapter 1
What is IBOC Radio?
IBOC is a form of terrestrial radio broadcasting that employs sophisticated digital radio waveforms
that can deliver compact disc-like quality sound, free of interference and noise to radio listeners. The
term IBOC is an acronym for In-Band On-Channel digital radio, a term that describes the use of the
existing AM and FM analog broadcasting bands and channel schemes for the digital transmissions.
“HD Radio” is a trade name for AM and FM IBOC digital radio systems, a trademark of iBiquity
Digital Corporation, the sole proponent for a comprehensive AM/FM digital radio broadcasting
(DRB) technology in the U.S.A. iBiquity licenses the mark to companies that want to use iBiquity
technology and that earn, through rigorous testing, the HD Radio brand identity.
The term Digital Audio Broadcasting (DAB) is a trademark of the Eureka-147 digital radio system,
which originated in Europe and is more commonly used in Europe, Canada and Asia. Eureka-
147 was the first commercially available digital radio broadcasting system. It requires broadcast
spectrum outside the traditional AM and FM bands and as such is characterized as a “new band”
(as opposed to in-band) system. Non-IBOC digital radio solutions, including Eureka-147, often
require more bandwidth or channel space per station than is currently allotted in the U.S. AM
and FM bands, resulting in a requirement for new spectrum. No new radio bands were available
for free over-the-air terrestrial radio broadcasting in the U.S., driving the evolution of an IBOC
technology that operates within existing AM and FM bands.
The IBOC digital radio transmitter system encodes incoming analog sound into a binary form
for transmission. With IBOC radio, a digitally modulated signal shares the radio station’s channel
with the existing analog signal (the analog signal is called the host). See Figure 1.1. In this fashion,
each radio station, AM and FM, is able to broadcast is digital signal.
Figure 1.1 IBOC Digital Radio Transmission
4