![](media/image1.wmf){width="5.375in" height="2.09375in"}

**IBOC FM Transmission Specification**

**August 2001**

**iBiquity Digital Corporation**

+------------------------------------+---------------------------------+
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| 202**                              |                                 |
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| **Columbia, Maryland 21045**       |                                 |
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Table of Contents

Contents

[1 Scope 1](#scope)

[2 Abbreviations, Symbols, and Conventions
2](#abbreviations-symbols-and-conventions)

[2.1 Introduction 2](#introduction)

[2.2 Abbreviations and Acronyms 2](#abbreviations-and-acronyms)

[2.3 Presentation Conventions 3](#presentation-conventions)

[2.4 Mathematical Symbols 3](#mathematical-symbols)

[2.4.1 Variable Naming Conventions 3](#variable-naming-conventions)

[2.4.2 Arithmetic Operators 4](#arithmetic-operators)

[2.5 FM System Parameters 4](#fm-system-parameters)

[3 IBOC Layers 6](#iboc-layers)

[3.1 FM Hybrid Layer 1 6](#fm-hybrid-layer-1)

[3.1.1 Introduction 6](#introduction-1)

[3.2 Waveforms and Spectra 7](#waveforms-and-spectra)

[3.2.1 Hybrid Waveform 7](#hybrid-waveform)

[3.2.2 Extended Hybrid Waveform 7](#extended-hybrid-waveform)

[3.2.3 All Digital Waveform 7](#all-digital-waveform)

[3.3 System Control Channel 7](#system-control-channel)

[3.4 Logical Channels 8](#logical-channels)

[3.4.1 Primary Logical Channels 8](#primary-logical-channels)

[3.4.2 Secondary Logical Channels 8](#secondary-logical-channels)

[3.4.3 Logical Channel Functionality 8](#logical-channel-functionality)

[3.5 Functional Components 9](#functional-components)

[3.5.1 Service Access Points 10](#service-access-points)

[3.5.2 Scrambling 10](#scrambling)

[3.5.3 Channel Encoding 10](#channel-encoding)

[3.5.4 Interleaving 10](#interleaving)

[3.5.5 System Control Processing 10](#system-control-processing)

[3.5.6 OFDM Subcarrier Mapping 10](#ofdm-subcarrier-mapping)

[3.5.7 OFDM Signal Generation 10](#ofdm-signal-generation)

[3.5.8 Transmission Subsystem 10](#transmission-subsystem)

[4 Functional Description 11](#__RefHeading___Toc521851911)

[4.1 Introduction 11](#introduction-2)

[4.2 Functionality 11](#functionality)

[4.3 Transmission Subsystem 12](#transmission-subsystem-1)

[4.3.1 Introduction 12](#introduction-3)

[4.4 Functional Components 14](#functional-components-1)

[4.4.1 Symbol Concatenation 14](#symbol-concatenation)

[4.4.2 Up-Conversion 15](#up-conversion)

[4.4.3 Diversity Delay 15](#diversity-delay)

[4.4.4 Analog FM Modulator 15](#analog-fm-modulator)

[4.4.5 Analog/Digital Combiner 15](#analogdigital-combiner)

[4.4.6 Use of On Channel Repeaters 16](#use-of-on-channel-repeaters)

[4.4.7 GPS Synchronizarion 16](#gps-synchronization)

[5 Waveforms and Spectra 17](#waveforms-and-spectra-1)

[5.1 Introduction 17](#introduction-4)

[5.2 Frequency Partitions and Spectral Conventions
17](#frequency-partitions-and-spectral-conventions)

[5.3 Hybrid Spectrum 19](#hybrid-spectrum)

[5.4 Extended Hybrid Spectrum 20](#extended-hybrid-spectrum)

[5.5 All Digital Spectrum 22](#all-digital-spectrum)

[Supplement A FM Transmission Specifications
24](#supplement-a-fm-transmission-specifications)

[A.1 Introduction 24](#introduction-5)

[A.2 Synchronization Tolerances 24](#synchronization-tolerances)

[A.2.1 Analog Diversity Delay 24](#analog-diversity-delay)

[A.2.2 RF Carrier Frequency and OFDM Symbol Clock
24](#rf-carrier-frequency-and-ofdm-symbol-clock)

[A.2.3 GPS Phase Lock 24](#gps-phase-lock)

[A.3 IBOC Noise and Emissions Limits
24](#iboc-noise-and-emissions-limits)

[A.3.1 Analog Waveform 25](#analog-waveform)

[A.3.2 Hybrid and Extended Hybrid Waveforms
25](#hybrid-and-extended-hybrid-waveforms)

[A.3.3 All Digital Waveform 26](#all-digital-waveform-1)

[A.4 Digital Sideband Levels 27](#digital-sideband-levels)

[Glossary 28](#glossary)

# Scope {#scope .unnumbered}

The iBiquity Digital Corporation's iDAB™ system is designed to permit a
smooth evolution from current analog Amplitude Modulation (AM) and
Frequency Modulation (FM) radio to a fully digital in-band on-channel
(IBOC) system. This system delivers digital audio and data services to
mobile, portable, and fixed receivers from terrestrial transmitters in
the existing Medium Frequency (MF) and Very High Frequency (VHF) radio
bands. Broadcasters may continue to transmit analog AM and FM
simultaneously with the new, higher-quality and more robust digital
signals, allowing themselves and their listeners to convert from analog
to digital radio while maintaining their current frequency allocations.

# Abbreviations, Symbols, and Conventions {#abbreviations-symbols-and-conventions .unnumbered}

## Introduction {#introduction .unnumbered}

Section presents the following items pertinent to a better understanding
of this document:

Abbreviations and Acronyms

Presentation Conventions

Mathematical Symbols

FM System Parameters

**Note:** A glossary defining the technical terms used herein is
provided at the end of this document.

## Abbreviations and Acronyms {#abbreviations-and-acronyms .unnumbered}

AM Amplitude Modulation

BC L1 Block Count

BPSK Binary Phase Shift Keying

DD Analog Diversity Delay Control

DDI Analog Diversity Delay Indicator

EAS Emergency Alert System

FCC Federal Communications Commission

FM Frequency Modulation

GPS Global Positioning System

IBOC In-Band On-Channel

IDS IBOC Data Service

IP Interleaving Process

kbit/sec kilobits per second

L1 Layer 1

L2 Layer 2

MF Medium Frequency

MP1--MP7 Primary Service Modes 1 through 7

MS1--MS4 Secondary Service Modes 1 through 4

N/A Not Applicable

OFDM Orthogonal Frequency Division Multiplexing

OSI Open Systems Interconnection

P1--P3 Primary Logical Channels 1 through 3

PIDS Primary IBOC Data Service Logical Channel

PM Primary Main

PSM Primary Service Mode

PX Primary Extended

QPSK Quadrature Phase Shift Keying

RF Radio Frequency

RSID Reference Subcarrier Identification

S1--S5 Secondary Logical Channels 1 through 5

SAP Service Access Point

SB Secondary Broadband

SCA Subsidiary Communications Authorization

SCCH System Control Channel

SCI Secondary Channel Indicator

SCU Service Control Unit

SDU Service Data Unit

SIDS Secondary IBOC Data Service Logical Channel

SM Secondary Main

SP Secondary Protected

SSM Secondary Service Mode

SX Secondary Extended

UTC Universal Time Coordinated

VHF Very High Frequency

## Presentation Conventions {#presentation-conventions .unnumbered}

Unless otherwise noted, the following conventions apply to this
document:

In this document, all provisions enclosed in braces{ } will either be
provided in the future or are anticipated to be subject to change upon
review.

All items in the glossary are presented in italics upon their first
usage in the text.

All vectors are indexed starting with 0.

The element of a vector with the lowest index is considered to be first.

In drawings and tables, the leftmost bit is considered to occur first.

Bit 0 of a byte or word is considered the least significant bit.

When presenting the dimensions of a matrix, the number of rows is given
first (e.g., an n x m matrix has n rows and m columns).

In timing diagrams, earliest time is on the left.

## Mathematical Symbols {#mathematical-symbols .unnumbered}

## Variable Naming Conventions {#variable-naming-conventions .unnumbered}

The variable naming conventions defined below are used throughout this
document.

  -------------------------------------------------------------------------------------------------------------------
  **Category**                            **Definition**         **Examples**
  --------------------------------------- ---------------------- ----------------------------------------------------
  Lower and upper case letters            Indicates scalar       i, j, J, g~11~
                                          quantities             

  Underlined lower and upper case letters Indicates vectors      [u]{.underline}, [V]{.underline}

  Double underlined lower and upper case  Indicates              u, V
  letters                                 two-dimensional        
                                          matrices               

  \[i\]                                   Indicates the i^th^    [u]{.underline}\[0\], [V]{.underline}\[1\]
                                          element of a vector,   
                                          where i is a           
                                          non-negative integer   

  \[ \]                                   Indicates the contents [v]{.underline} = \[0, 10, 6, 4\]
                                          of a vector            

  \[i\] \[j\]                             Indicates the element  u\[i\]\[j\], V\[i\]\[j\]
                                          of a two-dimensional   
                                          matrix in the i^th^    
                                          row and j^th^ column,  
                                          where i and j are      
                                          non-negative integers  

  ![](media/image2.wmf){width="0.625in"   Indicates the contents ![](media/image3.wmf){width="0.9027777777777778in"
  height="0.4305555555555556in"}          of a matrix            height="0.4305555555555556in"}

  n ...m                                  Indicates all the      3 ...6 = 3, 4, 5, 6
                                          integers from n to m,  
                                          inclusive              

  n:m                                     Indicates bit          Given a binary vector i = \[0, 1, 1, 0, 1, 1, 0,
                                          positions n through m  0\], i~2:5~ = \[1, 0, 1, 1\]
                                          of a binary sequence   
                                          or vector              
  -------------------------------------------------------------------------------------------------------------------

## Arithmetic Operators {#arithmetic-operators .unnumbered}

The arithmetic operators defined below are used throughout this
document.

  ----------------------------------------------------- ----------------------------- ----------------------------------------------------
  **Category**                                          **Definition**                **Examples**

  ∙                                                     Indicates a multiplication    3∙4 = 12
                                                        operation                     

  INT( )                                                Indicates the integer portion INT(5/3) = 1\
                                                        of a real number              INT(-1.8) = -1

  a MOD b                                               Indicates a modulo operation  33 MOD 16 = 1

  ![](media/image4.wmf){width="0.16666666666666666in"   Indicates modulo-2 binary     ![](media/image5.wmf){width="0.5138888888888888in"
  height="0.16666666666666666in"}                       addition                      height="0.18055555555555555in"}

  \|                                                    Indicates the concatenation   [B]{.underline} = \[[S]{.underline} \|
                                                        of two vectors                [F]{.underline}\]\
                                                                                      The resulting vector [B]{.underline} consists of the
                                                                                      elements of [S]{.underline} followed by the elements
                                                                                      of [F]{.underline}.

  J                                                     Indicates the square-root of  j =
                                                        -1                            ![](media/image6.wmf){width="0.3611111111111111in"
                                                                                      height="0.2361111111111111in"}

  Re( )                                                 Indicates the real component  If x = (3 + j4), Re(x) = 3
                                                        of a complex quantity         

  Im( )                                                 Indicates the imaginary       If x = (3 + j4), Im(x) = 4
                                                        component of a complex        
                                                        quantity                      

  Log~10~                                               Indicates the base-10         log~10~(100) = 2
                                                        logarithm                     
  ----------------------------------------------------- ----------------------------- ----------------------------------------------------

## FM System Parameters {#fm-system-parameters .unnumbered}

The FM system parameters defined below are used throughout this
document.

  --------------------- ------------ ----------- -------------------------- ---------------
  **Parameter Name**    **Symbol**   **Units**   **Exact Value**            **Computed
                                                                            Value\
                                                                            (to 4
                                                                            significant
                                                                            figures)**

  OFDM Subcarrier       ∆f           Hz          1488375/4096               363.4
  Spacing                                                                   

  Cyclic Prefix Width   α            none        7/128                      5.469 x 10^-2^

  OFDM Symbol Duration  T~s~         Sec.        (1+α) /∆f =\               2.902 x 10^-3^
                                                 (135/128)∙(4096/1488375)   

  OFDM Symbol Rate      R~s~         Hz          = 1/T~s~                   344.5

  L1 Frame Duration     T~f~         Sec.        65536/44100 = 512∙T~s~     1.486

  L1 Frame Rate         R~f~         Hz          = 1/T~f~                   6.729 x 10^-1^

  L1 Block Duration     T~b~         Sec.        = 32∙T~s~                  9.288 x 10^-2^

  L1 Block Rate         R~b~         Hz          = 1/T~b~                   10.77

  L1 Block Pair         T~p~         Sec.        = 64∙T~s~                  1.858 x 10^-1^
  Duration                                                                  

  L1 Block Pair Rate    R~p~         Hz          = 1/T~p~                   5.383

  Diversity Delay       N~dd~        none        3 = number of L1 frames of 3
  Frames                                         diversity delay            
  --------------------- ------------ ----------- -------------------------- ---------------

# IBOC Layers {#iboc-layers .unnumbered}

The IBOC detailed performance specifications are organized in terms of
the International Standards Organization Open Systems Interconnection
(ISO OSI) layered model. The definitions of this model are summarized
below for reference:

> •**Layer 1: Physical layer**

-   Modem, Interleaving, FEC, Scrambling

> •**Layer 2: Data link layer**

-   Routing Layer 1 Frames to/from Layer 4 \-- Minimal frame integrity
    checking.

> •**Layer 3: Network layer \--** [Not used in IBOC]{.underline}
>
> •**Layer 4: Transport layer \--** Builds services, reliable data
> delivery in format required for specific applications

-   Digital Audio

-   Control Data and Text

-   File & Packet Delivery

> •**Layer 5: Session layer \--** [Not used in IBOC]{.underline}
>
> •**Layer 6: Presentation layer \--** Provides services like
> Encoding/Decoding

-   Images

-   Text

-   Audio, PAC

> **•Layer 7** **Application layer 7: \--** Provides means of exchanging
> information to the user via human machine interface

-   Audio -- blending, audio processing etc..

-   Text -- Processing for display.

-   Video - Video image presentation.

-   Specialized applications like java applets etc..

Each OSI layer of the broadcasting system has a corresponding layer,
termed a peer, in the receiving system. The functionality of these
layers is such that the combined result of lower layers is to effect a
virtual communication between a given layer and its peer on the other
side.

For the purposes of this document covering the IBOC Transmission System
only Layer 1 will be described.

## FM Hybrid Layer 1  {#fm-hybrid-layer-1 .unnumbered}

### Introduction {#introduction-1 .unnumbered}

Layer 1 of the FM system converts information and system control from
Layer 2 (L2) into the FM IBOC waveform for transmission in the VHF band.
The information and control is transported in discrete transfer frames
via multiple logical channels through the Layer 1 service access points
(SAPs). These transfer frames are also referred to as Layer 2 service
data units (SDUs) and service control units (SCUs), respectively.

The L2 SDUs vary in size and format depending on the service mode. The
service mode, a major component of system control, determines the
transmission characteristics of each logical channel. After assessing
the requirements of their candidate applications, higher protocol layers
select service modes that most suitably configure the logical channels.
The plurality of logical channels reflects the inherent flexibility of
the system, which supports simultaneous delivery of various classes of
digital audio and data.

Layer 1 also receives system control as SCUs from Layer 2. System
control is processed in the System Control Processor.

This section presents the following:

An overview of the waveforms and spectra

An overview of the system control, including the available service modes

An overview of the logical channels

A high-level discussion of each of the functional components comprising
the Layer 1 FM air interface

**Note:** Throughout this document, various system parameters are
globally represented as mathematical symbols. Refer to Subsection 2.5
for their values.

## Waveforms and Spectra {#waveforms-and-spectra .unnumbered}

The design provides a flexible means of transitioning to a digital
broadcast system by providing three new waveform types: Hybrid, Extended
Hybrid, and All Digital. The Hybrid and Extended Hybrid types retain the
analog FM signal, while the All Digital type does not. All three
waveform operate well below allocated *spectral emissions mask* as
currently defined by the FCC.

The *digital signal* is modulated using *orthogonal frequency division
multiplexing* (OFDM). OFDM is a parallel modulation scheme in which the
data stream modulates a large number of orthogonal subcarriers, which
are transmitted simultaneously. OFDM is inherently flexible, readily
allowing the mapping of logical channels to different groups of
subcarriers.

Refer to Section 5 for a detailed description of the spectra of the
three-waveform types.

### Hybrid Waveform {#hybrid-waveform .unnumbered}

The digital signal is transmitted in *Primary* *Main* (PM) *sidebands*
on either side of the analog FM signal in the *Hybrid waveform*. The
power level of each sideband is approximately 23 dB below the total
power in the analog FM signal. The *analog signal* may be monophonic or
stereo, and may include subsidiary communications authorization (SCA)
channels.

### Extended Hybrid Waveform {#extended-hybrid-waveform .unnumbered}

In the *Extended Hybrid waveform*, the bandwidth of the Hybrid sidebands
can be extended toward the analog FM signal to increase digital
capacity. This additional spectrum, allocated to the inner edge of each
Primary Main sideband, is termed the *Primary* *Extended* (PX)
*sideband*.

### All Digital Waveform {#all-digital-waveform .unnumbered}

The greatest system enhancements are realized with the *All Digital
waveform*, in which the analog signal is removed and the bandwidth of
the primary digital sidebands is fully extended as in the Extended
Hybrid waveform. In addition, this waveform allows lower-power digital
*secondary sidebands* to be transmitted in the spectrum vacated by the
analog FM signal.

## System Control Channel {#system-control-channel .unnumbered}

The *System Control Channel* (SCCH) transports control and status
information. Primary and secondary service modes and *diversity delay*
control are sent from Layer 2 to Layer 1, while synchronization
information is sent from Layer 1 to Layer 2.

The service modes dictate all permissible configurations of the logical
channels. There are a total of eleven service modes.

The seven primary service modes are MP1, MP2, MP3, MP4, MP5, MP6, and
MP7. They configure the primary logical channels.

The four secondary service modes are MS1, MS2, MS3, and MS4. They
configure the secondary logical channels.

## Logical Channels {#logical-channels .unnumbered}

A logical channel is a signal path that conducts L2 SDUs in transfer
frames into Layer 1 with a specific grade of service, determined by
service mode. Layer 1 of the FM air interface provides ten logical
channels to higher layer protocols. Not all logical channels are used in
every service mode. Refer to subsection through Subsection for details.

### Primary Logical Channels {#primary-logical-channels .unnumbered}

There are four primary logical channels which are used with both the
Hybrid and All Digital waveforms. They are denoted as P1, P2, P3, and
PIDS. Table 0-1 shows the approximate information rate supported by each
primary logical channel as a function of primary service mode.

Table 0‑1 Approximate Information Rate of Primary Logical Channels

  --------- ------------- ------ ------ -------- ----------------------------------
  Service   Approximate                          Waveform
  Mode      Information                          
            Rate (kbps)                          

            P1            P2     P3     PIDS     

  MP1       25            74     0      1        Hybrid

  MP2       25            74     12     1        Extended Hybrid

  MP3       25            74     25     1        Extended Hybrid

  MP4       25            74     50     1        Extended Hybrid

  MP5       25            74     25     1        Extended Hybrid, All Digital (With
                                                 Analog)

  MP6       50            49     0      1        Extended Hybrid, All Digital (With
                                                 Analog)

  MP7       25            98     25     1        Extended Hybrid, All Digital (With
                                                 Analog)
  --------- ------------- ------ ------ -------- ----------------------------------

### Secondary Logical Channels {#secondary-logical-channels .unnumbered}

There are six secondary logical channels that are used only with the All
Digital waveform. They are denoted as S1, S2, S3, S4, S5, and SIDS.
Table 0-2 shows the approximate information rate supported by each
secondary logical channel as a function of secondary service mode.

Table 0‑2 Approximate Information Rate of Secondary Logical Channels

  ---------- ------------- ------- ------- ------- ------- ------- ----------------
  Service    Approximate                                           Waveform
  Mode       Information                                           
             Rate (kbps)                                           

             S1            S2      S3      S4      S5      SIDS    

  MS1        0             0       0       98      6       1       All Digital

  MS2        25            74      25      0       6       1       All Digital

  MS3        50            49      0       0       6       1       All Digital

  MS4        25            98      25      0       6       1       All Digital
  ---------- ------------- ------- ------- ------- ------- ------- ----------------

### Logical Channel Functionality {#logical-channel-functionality .unnumbered}

Logical channels P1 through P3 are designed to convey audio and data. S1
through S5 can be configured to carry data or surround sound audio.
Primary IBOC Data Service (PIDS) and Secondary IBOC Data Service (SIDS)
logical channels are designed to carry IBOC Data Service (IDS)
information.

The performance of each logical channel is completely described through
three characterization parameters: *transfer, latency,* and
*robustness*. Channel encoding, spectral mapping, interleaver depth, and
diversity delay are the components of these characterization parameters.
The service mode uniquely configures these components for each active
logical channel, thereby allowing the assignment of appropriate
characterization parameters.

In addition, the service mode specifies the framing and synchronization
of the transfer frames through each active logical channel.

## Functional Components {#functional-components .unnumbered}

This subsection includes a high-level description of each Layer 1
functional block and the associated signal flow. Figure 0-1 is a
functional block diagram of Layer 1 processing. Audio and data are
passed from the higher OSI layers to the physical layer, the modem,
through the Layer 1 Service Access points.

The flow of the signal is detailed in sections 3.5.1 through 3.5.8.

![](media/image7.wmf){width="5.498611111111111in" height="6.23125in"}

Figure 0‑1 FM Air Interface Layer 1 Functional Block Diagram

### Service Access Points {#service-access-points .unnumbered}

The L1 SAPs define the interface between Layer 2 and Layer 1 of the
*system protocol stack*. Each logical channel and the SCCH have their
own SAP. Each channel enters Layer 1 in discrete transfer frames, with
unique size and rate determined by the service mode. These Layer 2
transfer frames are typically referred to as L2 SDUs and SCUs.

### Scrambling {#scrambling .unnumbered}

This function randomizes the digital data in each logical channel to
"whiten" and mitigate signal periodicities when the waveform is
demodulated in a conventional analog FM demodulator.

### Channel Encoding {#channel-encoding .unnumbered}

This function uses convolution encoding to add redundancy to the digital
data in each logical channel to improve its reliability in the presence
of channel impairments. The size of the logical channel vectors is
increased in inverse proportion to the *code rate*. The encoding
techniques are configurable by service mode. Diversity delay is also
imposed on selected logical channels. At the output of the channel
encoder, the logical channel vectors retain their identity.

### Interleaving {#interleaving .unnumbered}

*Interleaving* in time and frequency is employed to mitigate the effects
of burst errors. The interleaving techniques are tailored to the VHF
*fading* environment and are configurable by service mode. In this
process, the logical channels lose their identity. The interleaver
output is structured in a matrix format; each matrix is comprised of one
or more logical channels and is associated with a particular portion of
the transmitted spectrum.

### System Control Processing {#system-control-processing .unnumbered}

This function generates a matrix of *system control data sequences*
which includes control and status (such as service mode), for broadcast
on the reference subcarriers.

### OFDM Subcarrier Mapping {#ofdm-subcarrier-mapping .unnumbered}

This function assigns the interleaved matrices and the system control
matrix to the *OFDM subcarriers*. One row of each active interleaver
matrix is processed every *OFDM symbol* T~s~ to produce one output
vector [X]{.underline}, which is a frequency-domain representation of
the signal. The mapping is specifically tailored to the non-uniform
interference environment and is a function of the service mode.

### OFDM Signal Generation {#ofdm-signal-generation .unnumbered}

This function generates the digital portion of the time-domain FM IBOC
waveform. The input vectors are transformed into a shaped time-domain
baseband pulse, y~n~(t), defining one OFDM symbol.

### Transmission Subsystem {#transmission-subsystem .unnumbered}

This function formats the baseband waveform for transmission through the
VHF channel. Major sub-functions include symbol concatenation and
frequency up-conversion. In addition, when transmitting the Hybrid
waveform, this function modulates the analog source and combines it with
the digital signal to form a composite Hybrid signal, s(t), ready for
transmission.

# Functional Description {#functional-description .unnumbered}

## Introduction {#introduction-2 .unnumbered}

OFDM Signal Generation receives complex, frequency-domain OFDM symbols
from OFDM Subcarrier Mapping, and outputs time-domain pulses
representing the digital portion of the FM IBOC signal. A conceptual
block diagram of OFDM Signal Generation is shown in Figure 0-2.

![](media/image8.wmf){width="2.854861111111111in"
height="3.229861111111111in"}

Figure 0‑2 OFDM Signal Generation Conceptual Block Diagram

The input to OFDM Signal Generation is a complex vector
[X]{.underline}~n~ of length L, representing the complex constellation
values for each OFDM subcarrier in OFDM symbol n. The output of OFDM
Signal Generation is a complex, baseband, time-domain pulse y~n~(t),
representing the digital portion of the FM IBOC signal for OFDM symbol
n.

## Functionality {#functionality .unnumbered}

Let [X]{.underline}~n~\[k\] be the scaled constellation points from OFDM
Subcarrier Mapping for the n^th^ symbol, where k = 0, 1, ..., L-1
indexes the OFDM subcarriers. Let y~n~(t) denote the time-domain output
of OFDM Signal Generation for the n^th^ symbol. Then y~n~(t) is written
in terms of [X]{.underline}~n~\[k\] as follows,

> ![](media/image9.wmf){width="3.111111111111111in"
> height="0.5138888888888888in"}

where n = 0, 1, ..., ∞, 0 [\<]{.underline} t \< ∞, L = 1093 is the total
number of OFDM subcarriers, and T~s~ and ∆f are the OFDM symbol duration
and OFDM subcarrier spacing, respectively, as defined in Subsection 2.5.

The *pulse-shaping function* h(ξ) is defined as:

![](media/image10.wmf){width="3.763888888888889in"
height="1.5833333333333333in"}

where α is the cyclic prefix width defined in Subsection 2.5, and T =
![](media/image11.wmf){width="0.2638888888888889in"
height="0.4583333333333333in"} is the reciprocal of the OFDM subcarrier
spacing.

## Transmission Subsystem {#transmission-subsystem-1 .unnumbered}

### Introduction {#introduction-3 .unnumbered}

The Transmission Subsystem formats the baseband FM IBOC waveform for
transmission through the VHF channel. Functions include symbol
concatenation and frequency up-conversion. In addition, when
transmitting the Hybrid or Extended Hybrid waveforms, this function
delays and modulates the baseband analog signal before combining it with
the digital waveform.

The input to this module is a complex, baseband, time-domain OFDM
symbol, y~n~(t), from the OFDM Signal Generation function. A baseband
analog signal m(t) is also input from an analog source, along with
optional subsidiary communications authorization (SCA) signals, when
transmitting the Hybrid or Extended Hybrid waveform. In addition, analog
diversity delay control (DD) is input from Layer 2 via the CCH. The
output of this module is the VHF FM IBOC

![](media/image12.wmf){width="6.001388888888889in"
height="5.590972222222222in"}

Figure 0‑3 Hybrid/Extended Hybrid Transmission Subsystem Functional
Block Diagram

.![](media/image13.wmf){width="3.073611111111111in"
height="4.407638888888889in"}

Figure 0‑4 All Digital Transmission Subsystem Functional Block Diagram

## Functional Components {#functional-components-1 .unnumbered}

The functional components of the Transmission Subsystem are specified in
Subsection through Subsection .

### Symbol Concatenation {#symbol-concatenation .unnumbered}

The individual time-domain OFDM symbols generated by OFDM Signal
Generation are concatenated to produce a continuum of pulses over t = 0,
...,![](media/image14.wmf){width="0.16666666666666666in"
height="0.13541666666666666in"}, as follows:

> ![](media/image15.wmf){width="1.0416666666666667in"
> height="0.46875in"}

### Up-Conversion {#up-conversion .unnumbered}

The concatenated digital signal y(t) is translated from baseband to the
RF carrier frequency as follows:

> ![](media/image16.wmf){width="1.4305555555555556in"
> height="0.4583333333333333in"}

where f~c~ is the VHF allocated channel frequency and Re\[ \] denotes
the real component of the complex quantity. For the All Digital
waveform, the output of the up-converter is the transmitted VHF FM IBOC
waveform, and therefore, s(t) = z(t).

The carrier frequency spacing and channel numbering scheme are
compatible with Title 47 CFR §73.201. The carriers retain their 200-kHz
spacing over the 88.0- to 108.0-MHz frequency range. Channels are
numbered from 201 to 300, where channel 201 is centered on 88.1 MHz and
channel 300 is centered on 107.9 MHz. The absolute accuracy of the
carrier frequency is defined in Appendix A.

### Diversity Delay {#diversity-delay .unnumbered}

When broadcasting the Hybrid and Extended Hybrid waveforms, z(t) is
combined with the analog FM signal a(t), as shown in Figure 0-3. The
first step in generating a(t) is the application of diversity delay to
the baseband analog signal m(t).

The analog diversity delay control bit (DD), received from Layer 2 via
the SCCH, is used by upper protocol layers to enable or disable the
diversity delay. If DD is 0, the diversity delay is disabled; if DD is
1, it is enabled. When diversity delay is enabled, an adjustable delay τ
is applied to the baseband analog signal m(t). The delay is set so that,
at the output of the analog/digital combiner, a(t) lags the
corresponding digital signal z(t) by T~dd~. In the IBOC system the
analog and digital signals carry the same audio program with the analog
audio delayed from the corresponding digital audio by T~dd~ at the
output of the analog/digital combiner. The delay is adjustable to
account for processing delays in the analog and digital chains.

The absolute accuracy of the diversity delay, when enabled, is defined
in Appendix A.

### Analog FM Modulator {#analog-fm-modulator .unnumbered}

For the Hybrid and Extended Hybrid waveforms, the appropriately delayed
baseband analog signal m(t-τ) is frequency modulated to produce an RF
analog FM waveform identical to existing analog signals. The
FM-modulated analog signal, including any SCAs, will maintain
compatibility with Title 47 CFR Part 73, Subparts B, C, and H. In
addition, the analog signal will be compatible with the emergency alert
system (EAS) as specified in Title 47 CFR Part 11.

### Analog/Digital Combiner {#analogdigital-combiner .unnumbered}

When broadcasting the Hybrid or Extended Hybrid waveform, the
analog-modulated FM RF signal is combined with the digitally-modulated
RF signal to produce the VHF FM IBOC waveform, s(t). Both the analog and
digital portions of the waveform are centered on the same carrier
frequency.

The levels of each digital sideband in the output spectrum are
appropriately scaled by OFDM Subcarrier Mapping. The subcarrier scale
factors and power ratios with respect to the total power of the analog
FM carrier are provided in Appendix A.

The spectral noise and emission limits of the IBOC digital signal are
defined in Appendix A.

### Use of On Channel Repeaters {#use-of-on-channel-repeaters .unnumbered}

The use of OFDM modulation in the FM IBOC system allows on-channel
digital repeaters to fill areas of desired coverage where signal losses
due to terrain and/or shadowing are severe. A typical application would
be where mountains or other terrain obstructions within the station's
service areas limit analog or digital performance.

iBiquity's FM IBOC system operates with an effective guard time between
OFDM symbols of approximately 150 microseconds[^1]. To avoid significant
intersymbol interference the effective coverage in the direction of the
primary transmission system should be limited to within 14 miles.
Specifically the ratio of the signal from the primary transmitter to the
booster signal should be at least 10 dB at locations more than 14 miles
from the repeater in the direction of the primary antenna. Performance
and distances between on-channel boosters can be improved through the
use of directional antennas to protect the main station. The coverage in
the direction pointing away from the primary antenna can be arbitrarily
large, but must conform to the FCC coverage allocation for that station.

### GPS Synchronization {#gps-synchronization .unnumbered}

In order to ensure precise time synchronization, for rapid station
acquisition and booster synchronization, each station is GPS locked.

This is normally accomplished through synchronization with a signal
synchronized in time and frequency to the Global Positioning System
(GPS)[^2]. Transmissions that are not locked to GPS, will not benefit
from fast tuning since they cannot be synchronized with other
stations[^3].

# Waveforms and Spectra {#waveforms-and-spectra-1 .unnumbered}

## Introduction {#introduction-4 .unnumbered}

This section describes the output spectrum for each of the three digital
waveform types: Hybrid, Extended Hybrid, and All Digital. Each spectrum
is divided into several sidebands, which represent various subcarrier
groupings. All spectra are represented at baseband.

## Frequency Partitions and Spectral Conventions {#frequency-partitions-and-spectral-conventions .unnumbered}

The OFDM subcarriers are assembled into *frequency partitions*. Each
frequency partition is comprised of eighteen data subcarriers and one
reference subcarrier, as shown in Figure 0-5 (ordering A) and Figure 0-6
(ordering B). The position of the reference subcarrier (ordering A or B)
varies with the location of the frequency partition within the spectrum.

![](media/image17.wmf){width="5.136111111111111in"
height="2.5930555555555554in"}

Figure 0‑5 Frequency Partition--Ordering A

![](media/image18.wmf){width="5.281944444444444in"
height="2.6347222222222224in"}

Figure 0‑6 Frequency Partition--Ordering B

For each frequency partition, data subcarriers d1 through d18 convey the
L2 SDUs, while the reference subcarriers convey system control.
Subcarriers are numbered from 0 at the center frequency to ±546 at
either end of the channel frequency allocation.

Besides the reference subcarriers resident within each frequency
partition, depending on the service mode, up to five additional
reference subcarriers are inserted into the spectrum at subcarrier
numbers −546, −279, 0, 279, and 546. The overall effect is a regular
distribution of reference subcarriers throughout the spectrum. For
notational convenience, each reference subcarrier is assigned a unique
identification number between 0 and 60. All *lower sideband* reference
subcarriers are shown in Figure 0-7. All *upper sideband* reference
subcarriers are shown in Figure 0-8. The figures indicate the
relationship between reference subcarrier numbers and OFDM subcarrier
numbers.

![](media/image19.wmf){width="6.41875in" height="1.69375in"}

Figure 0‑7 Lower Sideband Reference Subcarrier Spectral Mapping

![](media/image20.wmf){width="6.459722222222222in"
height="1.761111111111111in"}

Figure 0‑8 Upper Sideband Reference Subcarrier Spectral Mapping

Each spectrum described in the remaining subsections shows the
subcarrier number and center frequency of certain key OFDM subcarriers.
The center frequency of a subcarrier is calculated by multiplying the
subcarrier number by the OFDM subcarrier spacing ∆f. The center of
subcarrier 0 is located at 0 Hz. In this context, center frequency is
relative to the radio frequency (RF) *allocated channel*.

For example, the upper Primary Main sideband is bounded by subcarriers
356 and 546, whose center frequencies are located at 129,361 Hz and
198,402 Hz, respectively. The frequency span of the Primary Main
sideband is 69,041 Hz. (198,402 -- 129,361).

## Hybrid Spectrum {#hybrid-spectrum .unnumbered}

The digital signal is transmitted in PM sidebands on either side of the
analog FM signal, as shown in Figure 0-9. Each PM sideband is comprised
of ten frequency partitions, which are allocated among subcarriers 356
through 545, or -356 through -545. Subcarriers 546 and -546, also
included in the PM sidebands, are additional reference subcarriers. The
amplitude of the subcarrier within Primary Main sidebands are uniformly
scaled by an *amplitude scale factor, a~0~*. The amplitude scaling
factor is described in Appendix A. Table 0-3 summarizes the upper and
lower Primary Main sidebands for the Hybrid waveform.

![](media/image21.wmf){width="5.991666666666666in"
height="3.3847222222222224in"}

Figure 0‑9 Spectrum of the Hybrid Waveform--Service Mode MP1

Table 0‑3 Hybrid Waveform Spectral Summary--Service Mode MP1

+------+-------+-------+-------+--------+-----+----------+----------+
| Side | N     | Freq  | Subca | Subc   | Am  | F        | Comments |
| band | umber | uency | rrier | arrier | pl. | requency |          |
|      | of\   | Part  | Range | Frequ  |     | Span     |          |
|      | Freq  | ition |       | encies | Sc  | (Hz)     |          |
|      | uency | Ord   |       | (Hz    | ale |          |          |
|      | Parti | ering |       | from   |     |          |          |
|      | tions |       |       | c      | Fac |          |          |
|      |       |       |       | hannel | tor |          |          |
|      |       |       |       | c      |     |          |          |
|      |       |       |       | enter) |     |          |          |
+------+-------+-------+-------+--------+-----+----------+----------+
| U    | 10    | A     | 356\  | 12     | a   | 69,041   | Includes |
| pper |       |       | to\   | 9,361\ | ~o~ |          | ad       |
| Pri  |       |       | 546   | to\    |     |          | ditional |
| mary |       |       |       | 1      |     |          | r        |
| Main |       |       |       | 98,402 |     |          | eference |
|      |       |       |       |        |     |          | su       |
|      |       |       |       |        |     |          | bcarrier |
|      |       |       |       |        |     |          | 546      |
+------+-------+-------+-------+--------+-----+----------+----------+
| L    | 10    | B     | -356\ | -12    | a   | 69,041   | Includes |
| ower |       |       | to\   | 9,361\ | ~o~ |          | ad       |
| Pri  |       |       | -546  | to\    |     |          | ditional |
| mary |       |       |       | -1     |     |          | r        |
| Main |       |       |       | 98,402 |     |          | eference |
|      |       |       |       |        |     |          | su       |
|      |       |       |       |        |     |          | bcarrier |
|      |       |       |       |        |     |          | -546     |
+------+-------+-------+-------+--------+-----+----------+----------+

**Note:** Refer to Appendix A for details regarding the amplitude scale
factors shown above.

## Extended Hybrid Spectrum {#extended-hybrid-spectrum .unnumbered}

The Extended Hybrid waveform is created by adding Primary Extended
sidebands to the Primary Main sidebands present in the Hybrid waveform,
as shown in Figure 0-10. Depending on the service mode, one, two, or
four frequency partitions can be added to the inner edge of each Primary
Main sideband.

Each Primary Main sideband consists of ten frequency partitions and an
additional reference subcarrier spanning subcarriers 356 through 546, or
-356 through -546. The upper Primary Extended sidebands include
subcarriers 337 through 355 (one frequency partition), 318 through 355
(two frequency partitions), or 280 through 355 (four frequency
partitions). The lower Primary Extended sidebands include subcarriers
-337 through -355 (one frequency partition), -318 through -355 (two
frequency partitions), or -280 through -355 (four frequency partitions).
The subcarriers within Primary Extended sidebands are uniformly scaled
the same *amplitude scale factor,* a~0,~ as the Primary Main sidebands.
The amplitude scaling factor is described in Appendix A. Table 0-4
summarizes the Upper and Lower Primary sidebands for the Extended Hybrid
waveform.

![](media/image22.wmf){width="5.991666666666666in"
height="3.310416666666667in"}

Figure 0‑10 Spectrum of the Extended Hybrid Waveform--Service Modes MP2
through MP4

Table 0‑4 Extended Hybrid Waveform Spectral Summary--Service Modes MP2
through MP4

+---------+-------+-------+-------+--------+-----+---------+--------+
| S       | N     | Freq  | Subca | Subc   | Am  | Fr      | Co     |
| ideband | umber | uency | rrier | arrier | pl. | equency | mments |
|         | of    | Part  | Range | Frequ  |     | Span    |        |
|         | Freq  | ition |       | encies | Sc  | (Hz)    |        |
|         | uency | Ord   |       | (Hz    | ale |         |        |
|         | Parti | ering |       | from   |     |         |        |
|         | tions |       |       | c      | Fac |         |        |
|         |       |       |       | hannel | tor |         |        |
|         |       |       |       | c      |     |         |        |
|         |       |       |       | enter) |     |         |        |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Upper   | 10    | A     | 356\  | 12     | a   | 69,041  | In     |
| Primary |       |       | to\   | 9,361\ | ~o~ |         | cludes |
| Main    |       |       | 546   | to\    |     |         | addi   |
|         |       |       |       | 1      |     |         | tional |
|         |       |       |       | 98,402 |     |         | ref    |
|         |       |       |       |        |     |         | erence |
|         |       |       |       |        |     |         | subc   |
|         |       |       |       |        |     |         | arrier |
|         |       |       |       |        |     |         | 546    |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Lower   | 10    | B     | -356\ | -1     | a   | 69,041  | In     |
| Primary |       |       | to\   | 29,361 | ~o~ |         | cludes |
| Main    |       |       | -546  | to\    |     |         | addi   |
|         |       |       |       | -1     |     |         | tional |
|         |       |       |       | 98,402 |     |         | ref    |
|         |       |       |       |        |     |         | erence |
|         |       |       |       |        |     |         | subca  |
|         |       |       |       |        |     |         | rrier\ |
|         |       |       |       |        |     |         | -546   |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Upper   | 1     | A     | 337\  | 12     | a   | 6,540   | none   |
| Primary |       |       | to\   | 2,457\ | ~o~ |         |        |
| Ex      |       |       | 355   | to\    |     |         |        |
| tended\ |       |       |       | 1      |     |         |        |
| (1      |       |       |       | 28,997 |     |         |        |
| fr      |       |       |       |        |     |         |        |
| equency |       |       |       |        |     |         |        |
| par     |       |       |       |        |     |         |        |
| tition) |       |       |       |        |     |         |        |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Lower   | 1     | B     | -337\ | -1     | a   | 6,540   | none   |
| Primary |       |       | to\   | 22,457 | ~o~ |         |        |
| Ex      |       |       | -355  | to\    |     |         |        |
| tended\ |       |       |       | -1     |     |         |        |
| (1      |       |       |       | 28,997 |     |         |        |
| fr      |       |       |       |        |     |         |        |
| equency |       |       |       |        |     |         |        |
| par     |       |       |       |        |     |         |        |
| tition) |       |       |       |        |     |         |        |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Upper   | 2     | A     | 318\  | 11     | a   | 13,444  | none   |
| Primary |       |       | to\   | 5,553\ | ~o~ |         |        |
| Ex      |       |       | 355   | to\    |     |         |        |
| tended\ |       |       |       | 1      |     |         |        |
| (2      |       |       |       | 28,997 |     |         |        |
| fr      |       |       |       |        |     |         |        |
| equency |       |       |       |        |     |         |        |
| part    |       |       |       |        |     |         |        |
| itions) |       |       |       |        |     |         |        |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Lower   | 2     | B     | -318\ | -115,  | a   | 13,444  | none   |
| Primary |       |       | to\   | 553    | ~o~ |         |        |
| Ex      |       |       | -355  | to\    |     |         |        |
| tended\ |       |       |       | -1     |     |         |        |
| (2      |       |       |       | 28,997 |     |         |        |
| fr      |       |       |       |        |     |         |        |
| equency |       |       |       |        |     |         |        |
| part    |       |       |       |        |     |         |        |
| itions) |       |       |       |        |     |         |        |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Upper   | 4     | A     | 280\  | 10     | a   | 27,253  | none   |
| Primary |       |       | to\   | 1,744\ | ~o~ |         |        |
| Ex      |       |       | 355   | to\    |     |         |        |
| tended\ |       |       |       | 1      |     |         |        |
| (4      |       |       |       | 28,997 |     |         |        |
| fr      |       |       |       |        |     |         |        |
| equency |       |       |       |        |     |         |        |
| part    |       |       |       |        |     |         |        |
| itions) |       |       |       |        |     |         |        |
+---------+-------+-------+-------+--------+-----+---------+--------+
| Lower   | 4     | B     | -280\ | -101,  | a   | 27,253  | none   |
| Primary |       |       | to\   | 744    | ~o~ |         |        |
| Ex      |       |       | -355  | to\    |     |         |        |
| tended\ |       |       |       | -1     |     |         |        |
| (4      |       |       |       | 28,997 |     |         |        |
| fr      |       |       |       |        |     |         |        |
| equency |       |       |       |        |     |         |        |
| part    |       |       |       |        |     |         |        |
| itions) |       |       |       |        |     |         |        |
+---------+-------+-------+-------+--------+-----+---------+--------+

**Note:** Refer to Appendix A for details regarding the amplitude scale.

## All Digital Spectrum {#all-digital-spectrum .unnumbered}

The All Digital waveform is constructed by removing the analog signal,
fully expanding the bandwidth of the primary digital sidebands, and
adding lower-power secondary sidebands in the spectrum vacated by the
analog signal. The spectrum of the All Digital waveform is shown in
Figure 0-11.

![](media/image23.wmf){width="5.997222222222222in"
height="2.957638888888889in"}

Figure 0‑11 Spectrum of the All Digital Waveform--Service Modes MP5
through MP7, MS1 through MS4

In addition to the ten main frequency partitions, all four extended
frequency partitions are present in each primary sideband of the All
Digital waveform. Each secondary sideband also has ten Secondary Main
(SM) and four Secondary Extended frequency partitions. Unlike the
primary sidebands, however, the Secondary Main frequency partitions are
mapped nearer to channel center with the extended frequency partitions
farther from the center.

Each secondary sideband also supports a small Secondary Protected (SP)
region consisting of 12 OFDM subcarriers and reference subcarriers 279
and -279. The sidebands are referred to as "protected" because they are
located in the area of spectrum *least* likely to be affected by analog
or digital interference. An additional reference subcarrier is placed at
the center of the channel (0). Frequency partition ordering of the SP
region does not apply since the SP region does not contain frequency
partitions as defined in Figure 0-5 and Figure 0-6.

Each Secondary Main sideband spans subcarriers 1 through 190 or -1
through -190. The upper Secondary Extended sideband includes subcarriers
191 through 266, and the upper Secondary Protected sideband includes
subcarriers 267 through 278, plus additional reference subcarrier 279.
The lower Secondary Extended sideband includes subcarriers -191 through
-266, and the lower Secondary Protected sideband includes subcarriers
-267 through -278, plus additional reference subcarrier -279. The total
frequency span of the entire All Digital spectrum is 396,803 Hz. The
subcarriers within the Primary Main and Primary Extended sidebands are
scaled by an amplitude scale factor, a~2~, as indicated in Table 0-5.
The subcarriers within the Secondary Main, Secondary Extended and
Secondary Protected sidebands are uniformly scaled by an amplitude scale
factor having four discrete levels a~4\ --~ a~7~, as indicated in Table
0-5. Table 0-5 summarizes the upper and lower, primary and secondary
sidebands for the All Digital waveform.

Table 0‑5 All Digital Waveform Spectral Summary--Service Modes MP5
through MP7, MS1 through MS4

+-------+-------+-------+-------+--------+-----+---------+----------+
| Sid   | N     | Freq  | Subca | Subc   | Am  | Fr      | Comments |
| eband | umber | uency | rrier | arrier | pl. | equency |          |
|       | of    | Part  | Range | Frequ  |     | Span    |          |
|       | Freq  | ition |       | encies | Sc  | (Hz)    |          |
|       | uency | Ord   |       | (Hz    | ale |         |          |
|       | Parti | ering |       | from   |     |         |          |
|       | tions |       |       | c      | Fac |         |          |
|       |       |       |       | hannel | tor |         |          |
|       |       |       |       | c      |     |         |          |
|       |       |       |       | enter) |     |         |          |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Upper | 10    | A     | 356\  | 12     | a   | 69,041  | Includes |
| Pr    |       |       | to\   | 9,361\ | ~2~ |         | ad       |
| imary |       |       | 546   | to\    |     |         | ditional |
| Main  |       |       |       | 1      |     |         | r        |
|       |       |       |       | 98,402 |     |         | eference |
|       |       |       |       |        |     |         | su       |
|       |       |       |       |        |     |         | bcarrier |
|       |       |       |       |        |     |         | 546      |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Lower | 10    | B     | -356\ | -1     | a   | 69,041  | Includes |
| Pr    |       |       | to\   | 29,361 | ~2~ |         | ad       |
| imary |       |       | -546  | to\    |     |         | ditional |
| Main  |       |       |       | -1     |     |         | r        |
|       |       |       |       | 98,402 |     |         | eference |
|       |       |       |       |        |     |         | su       |
|       |       |       |       |        |     |         | bcarrier |
|       |       |       |       |        |     |         | -546     |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Upper | 4     | A     | 280\  | 10     | a   | 27,253  | none     |
| Pr    |       |       | to\   | 1,744\ | ~2~ |         |          |
| imary |       |       | 355   | to\    |     |         |          |
| Ext   |       |       |       | 1      |     |         |          |
| ended |       |       |       | 28,997 |     |         |          |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Lower | 4     | B     | -280\ | -1     | a   | 27,253  | none     |
| Pr    |       |       | to\   | 01,744 | ~2~ |         |          |
| imary |       |       | -355  | to\    |     |         |          |
| Ext   |       |       |       | -1     |     |         |          |
| ended |       |       |       | 28,997 |     |         |          |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Upper | 10    | B     | 0\    | 0\     | a   | 69,041  | Includes |
| Seco  |       |       | to\   | to\    | ~2~ |         | ad       |
| ndary |       |       | 190   | 69,041 |     |         | ditional |
| Main  |       |       |       |        |     |         | r        |
|       |       |       |       |        |     |         | eference |
|       |       |       |       |        |     |         | su       |
|       |       |       |       |        |     |         | bcarrier |
|       |       |       |       |        |     |         | 0        |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Lower | 10    | A     | -1\   | -363\  | a   | 68,678  | none     |
| Seco  |       |       | to\   | to\    | ~2~ |         |          |
| ndary |       |       | -190  | -      |     |         |          |
| Main  |       |       |       | 69,041 |     |         |          |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Upper | 4     | B     | 191\  | 6      | a~  | 27,253  | none     |
| Seco  |       |       | to\   | 9,404\ | 4\  |         |          |
| ndary |       |       | 266   | to\    | --~ |         |          |
| Ext   |       |       |       | 96,657 | a   |         |          |
| ended |       |       |       |        | ~7~ |         |          |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Lower | 4     | A     | -191\ | -6     | a~  | 27,253  | none     |
| Seco  |       |       | to\   | 9,404\ | 4\  |         |          |
| ndary |       |       | -266  | to\    | --~ |         |          |
| Ext   |       |       |       | -      | a   |         |          |
| ended |       |       |       | 96,657 | ~7~ |         |          |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Upper | N/A   | N/A   | 267\  | 9      | a~  | 4,360   | Includes |
| Seco  |       |       | to\   | 7,021\ | 4\  |         | ad       |
| ndary |       |       | 279   | to\    | --~ |         | ditional |
| Prot  |       |       |       | 1      | a   |         | r        |
| ected |       |       |       | 01,381 | ~7~ |         | eference |
|       |       |       |       |        |     |         | su       |
|       |       |       |       |        |     |         | bcarrier |
|       |       |       |       |        |     |         | 279      |
+-------+-------+-------+-------+--------+-----+---------+----------+
| Lower | N/A   | N/A   | -267\ | -9     | a~  | 4,360   | Includes |
| Seco  |       |       | to\   | 7,021\ | 4\  |         | ad       |
| ndary |       |       | -279  | to\    | --~ |         | ditional |
| Prot  |       |       |       | -1     | a   |         | r        |
| ected |       |       |       | 01,381 | ~7~ |         | eference |
|       |       |       |       |        |     |         | su       |
|       |       |       |       |        |     |         | bcarrier |
|       |       |       |       |        |     |         | 279      |
+-------+-------+-------+-------+--------+-----+---------+----------+

**Note:** Refer to Appendix A for details regarding the amplitude scale
factors.

# Supplement A FM Transmission Specifications

## Introduction

This appendix presents the key transmission specifications for the FM
IBOC system, as described in the body of this document.

## Synchronization Tolerances

The synchronization tolerances are specified in Subsection A.2.1 through
Subsection A.2.3. The system shall support two levels of synchronization
for each broadcaster:

Level I: GPS-locked transmission facilities

Level II: Non-GPS-locked transmission facilities

Normally, transmission facilities will operate as Level I facilities in
order to support numerous advanced system features.

### Analog Diversity Delay

The absolute accuracy of the analog diversity delay in the transmission
signal will be within ±10 microseconds (μsec) for both synchronization
Level I and Level II transmission facilities.

Diversity delay accuracy will be verified with a calibrated test
receiver receiving the RF channel under test. A digitally generated 4
kHz sinusoidal test tone at a level of -6 dB from full scale will be
applied to both the analog and digital transmit signal paths. The tone
will be a pulsed signal, consisting of a repeating pattern of 0.5
seconds on followed by 4.5 seconds off.

### RF Carrier Frequency and OFDM Symbol Clock

For synchronization Level I transmission facilities, the absolute
accuracy of the carrier frequency and OFDM symbol clock frequency will
be maintained to within 1 part per 10^8^ at all times.

For synchronization Level II transmission facilities, the absolute
accuracy of the carrier frequency and OFDM symbol clock frequency will
be maintained to within 2 parts per 10^6^ at all times.

### GPS Phase Lock

For Level I transmission facilities, all transmissions will maintain
phase lock to absolute GPS time within ± 1 μsec.

If the above specification in a synchronization Level I transmission
facility is violated, due to a GPS outage or other occurrence, it will
be classified as a synchronization Level II transmission facility until
the above specification is again met.

## IBOC Noise and Emissions Limits

The noise and emissions limits are as specified in Subsection A.3.1
through Subsection A.3.3.

### Analog Waveform

Analog transmissions will remain within the Federal Communications
Commission (FCC) emissions mask in accordance with CFR Title 47 §73.317
and summarized in Table A-. Measurements of the analog signal are made
at the antenna input by averaging the power spectral density in a 1-kHz
bandwidth over a 10-second segment of time.

Table A- FCC RF Spectral Emissions Mask

  ------------------------ ----------------------------------------------
  **Offset from Carrier    **Power Spectral Density Relative to
  Frequency\               Unmodulated Analog FM Carrier (dBc/kHz)**
  (kHz)**                  

  120 to 240               -25

  240 to 600               -35

  greater than 600         -80, or -43 - (10 ∙ log~10~ \[power in
                           watts\]), whichever is less, where \[power in
                           watts\] refers to the total unmodulated
                           transmitter output carrier power
  ------------------------ ----------------------------------------------

### Hybrid and Extended Hybrid Waveforms

Hybrid and Extended Hybrid waveform transmissions including noise and
spuriously generated signals from all sources, including phase noise of
the IBOC exciter and intermodulation products will remain within the
Noise and Emissions Limit as depicted in Figure A-1 and summarized in
Table A-1. Measurements of the digitally-modulated signals are relative
to the PM sidebands of the digital carriers spectral density in a 1 kHz
bandwidth.

![](media/image24.wmf){width="6.538194444444445in"
height="3.5305555555555554in"} ***Figure A-1 IBOC FM HPA Hybrid Mode
Signal and Noise Emission Limits***

Table A-1 IBOC FM HPA Hybrid Mode Signal and Noise Emission Limits

  ------------------------------ ----------------------------------------
  Frequency, F, Offset Relative  Level, dB/kHz
  to Carrier                     

  0-30 kHz offset                -60 dB

  30-95 kHz offset               \[-60 + (\|frequency in kHz\|-30 kHz) \*
                                 0.3077\] dB

  95-100 kHz offset              \[-20 + (\|frequency in kHz\|-100 kHz)
                                 \* 4.0\] dB

  200-205 kHz offset             \[-20 - (\|frequency in kHz\|-200 kHz)
                                 \* 4.0\] dB

  205-270 kHz offset             \[-40 -- (\|frequency in kHz\|-205 kHz)
                                 \* 0.3077\] dB

  \>270 kHz offset               -60 dB
  ------------------------------ ----------------------------------------

### All Digital Waveform

All Digital waveform transmissions will remain within the Noise and
Emissions Limit as depicted in Figure A-2 and summarized in Table A-2.
Measurements of the digitally-modulated signals are relative to the PM
sidebands of the digital carriers spectral density in a 1 kHz bandwidth.

![](media/image25.wmf){width="6.538194444444445in"
height="3.5305555555555554in"} ***Figure A-2 IBOC FM HPA All-Digital
Mode Signal and Noise Emission Limits***

Table A-2 IBOC FM HPA All Digital Mode Signal and Noise Emission Limits

  ------------------------------ ----------------------------------------
  **Frequency, F, Offset         **Level, dB/kHz**
  Relative to Carrier**          

  0-100 kHz offset               -17dB

  200-207.5 kHz offset           \[-20 - (\|frequency in kHz\|-200 kHz)
                                 \*4.0\] dB

  207.5-270 kHz offset           \[-50 - (\|frequency in kHz\|-207.5 kHz)
                                 \* 0.3200\] dB

  270-600 kHz offset             -70 dB

  \>600 kHz offset               -80 dB
  ------------------------------ ----------------------------------------

## Digital Sideband Levels

The amplitude scaling of each OFDM subcarrier within each digital
sideband is given in Table A-3 for the Hybrid, Extended Hybrid, and All
Digital waveforms. The values for the Hybrid waveforms are specified
relative to the total power of the unmodulated analog FM carrier
(assumed equal to 1). The values for the All Digital waveform are
specified relative to the total power of the unmodulated analog FM
carrier (assumed equal to 1) that would have been transmitted in the
Hybrid and Extended Hybrid modes.

For the Hybrid and Extended Hybrid waveforms, the values were chosen so
that the total average power in a primary digital sideband (upper or
lower) is 23 dB below the total power of unmodulated analog FM carrier.

For the All Digital waveform, the values were chosen so that the total
average power in a primary digital sideband (upper or lower) is at least
10 dB above the total power in the Hybrid primary digital sidebands. In
addition, the values were chosen so that the total average power in the
secondary digital sidebands (upper and lower) is at least 20 dB below
the total power in the All Digital primary digital sidebands.

Table A-3 OFDM Subcarrier Scaling

  -------------------------------------------------------------------------------------------
  **Waveform**   **Mode**   **Sidebands**   **Amplitude   **Amplitude Scale **Scale
                                            Scale Factor  Factor**[^4]**\   Factor**[^5]**\
                                            Notation**    (relative to      (dB, relative to
                                                          total analog FM   total analog FM
                                                          power)**          power)**
  -------------- ---------- --------------- ------------- ----------------- -----------------
  Hybrid         MP1        Primary         a~0~          5.123 x 10^-3^    -41.39

  Extended       MP2 -- MP7 Primary         a~0~          5.123 x 10^-3^    -41.39
  Hybrid                                                                    

  All Digital    MP-5 --    Primary         a~2~          1.67x 10^-2^      -31.39
                 MP7                                                        

                 MS1 -- MS4 Secondary       a~4~          5.123 x10^-3^     -41.39

                            Secondary       a~5~          3.627 x 10^-3^    -44.39

                            Secondary       a~6~          2.567 x 10^-3^    -47.39

                            Secondary       a~7~          1.181 x 10^-3^    -50.39
  -------------------------------------------------------------------------------------------

# Glossary

For the purpose of better understanding this document, the following
definitions apply:

+-----------------------------------------------------------------------+
| **All Digital waveform** - The transmitted waveform composed entirely |
| of digitally modulated subcarriers (subcarrier -546 to +546) without  |
| an analog FM signal. Use of this waveform will normally follow an     |
| initial transitional phase utilizing hybrid waveforms incorporating   |
| both analog and digital modulation (see *Hybrid waveform* and         |
| *Extended Hybrid waveform*).                                          |
+-----------------------------------------------------------------------+
| **allocated channel --** One of the one hundred possible frequency    |
| assignments in the FM band, as defined in Reference \[10\].           |
+-----------------------------------------------------------------------+
| **amplitude modulation (AM) -** Modulation in which the amplitude of  |
| a carrier wave is varied in accordance with the amplitude of the      |
| modulating signal.                                                    |
+-----------------------------------------------------------------------+
| **amplitude scale factor** -- A factor which multiplies the baseband  |
| components of a particular sideband of the transmitted spectrum to    |
| constrain the radiated power to a prescribed level.                   |
+-----------------------------------------------------------------------+
| **analog signal** - refers to signals that are modulated on the main  |
| carrier by conventional high‑modulation‑index frequency modulation.   |
| (see *digital signal*).                                               |
+-----------------------------------------------------------------------+
| **Binary Phase Shift Keying (BPSK) --** A form of digital phase       |
| modulation that assigns one of two discrete phases, differing by 180  |
| degrees, to the carrier. Each BPSK symbol conveys one bit of          |
| information.                                                          |
+-----------------------------------------------------------------------+
| **channel encoding** - The process used to add redundancy to each of  |
| the logical channels to improve the reliability of the transmitted    |
| information.                                                          |
+-----------------------------------------------------------------------+
| **characterization parameters** - The unique set of defining          |
| parameters for each logical channel for a given service mode. The     |
| channel encoding, interleaving, spectral mapping, and diversity delay |
| of the logical channel determine its characterization parameters.     |
+-----------------------------------------------------------------------+
| **code rate** - Defines the increase in overhead on a coded channel   |
| resulting from channel encoding. It is the ratio of information bits  |
| to the total number of bits after coding.                             |
+-----------------------------------------------------------------------+
| **convolutional encoding** - A form of forward error-correction       |
| channel encoding that inserts coding bits into a continuous stream of |
| information bits to form a predictable structure. Unlike a block      |
| encoder, a convolutional encoder has memory; its output is a function |
| of current and previous inputs.                                       |
+-----------------------------------------------------------------------+
| **differential encoding** - Encoding process in which signal states   |
| are represented as changes to succeeding values rather than absolute  |
| values.                                                               |
+-----------------------------------------------------------------------+
| **digital signal** - refers to signals that are digitally modulated   |
| on subcarriers by OFDM (q.v.) (see *analog signal*).                  |
+-----------------------------------------------------------------------+
| **diversity delay** - Imposition of a fixed time delay in one of two  |
| channels carrying the same information to defeat non-stationary       |
| channel impairments such as fading and impulsive noise.               |
+-----------------------------------------------------------------------+
| **Extended Hybrid waveform** - The transmitted waveform composed of   |
| the analog FM signal plus digitally modulated primary main            |
| subcarriers (subcarriers +356 to +546 and -356 to -546) and some or   |
| all primary extended subcarriers (subcarriers +280 to +355 and -280   |
| to -355). This waveform will normally be used during an initial       |
| transitional phase preceding conversion to the All Digital waveform   |
| (see *All Digital waveform* and *Hybrid waveform*).                   |
+-----------------------------------------------------------------------+
| **fading** - The variation (with time) of the amplitude or relative   |
| phase (or both) of one or more frequency components of a received     |
| signal.                                                               |
+-----------------------------------------------------------------------+
| **frequency modulation (FM)** - Modulation in which the instantaneous |
| frequency of a sine wave carrier is caused to depart from the center  |
| frequency by an amount proportional to the instantaneous amplitude of |
| the modulating signal.                                                |
+-----------------------------------------------------------------------+
| **frequency partition** - A group of 19 OFDM subcarriers containing   |
| 18 data subcarriers and one reference subcarrier.                     |
+-----------------------------------------------------------------------+
| **Hybrid waveform** - The transmitted waveform composed of the analog |
| FM-modulated signal, plus digitally modulated Primary Main            |
| subcarriers (subcarriers +356 to +546 and -356 to -546). This         |
| waveform will normally be used during an initial transitional phase   |
| preceding conversion to the All Digital waveform (see *All Digital    |
| waveform* and *Extended Hybrid waveform*).                            |
+-----------------------------------------------------------------------+
| **interleaving** - A reordering of the message bits to distribute     |
| them in time (over different OFDM symbols) and frequency (over        |
| different OFDM subcarriers) to mitigate the effects of signal fading  |
| and interference.                                                     |
+-----------------------------------------------------------------------+
| **interleaving process** - A series of manipulations performed on one |
| or more coded transfer frames (vectors) to reorder their bits into    |
| one or more interleaver matrices whose contents are destined for a    |
| particular portion of the transmitted spectrum.                       |
+-----------------------------------------------------------------------+
| **L1 block -** A unit of time of duration T~b~. Each L1 frame is      |
| comprised of 16 L1 blocks.                                            |
+-----------------------------------------------------------------------+
| **L1 block count --** An index that indicates one of 16 equal         |
| subdivisions of an L1 frame.                                          |
+-----------------------------------------------------------------------+
| **L1 block pair** - Two contiguous L1 blocks. A unit of time duration |
| T~p~.                                                                 |
+-----------------------------------------------------------------------+
| **L1 block pair rate -** The rate, equal to the reciprocal of the L1  |
| block pair duration,                                                  |
| ![](media/image26.wmf){width="0.3888888888888889in"                   |
| height="0.5555555555555556in"}, at which selected transfer frames are |
| conducted through Layer 1.                                            |
+-----------------------------------------------------------------------+
| **L1 block rate -** The rate, equal to the reciprocal of the L1 block |
| duration, ![](media/image27.wmf){width="0.375in"                      |
| height="0.5277777777777778in"}, at which selected transfer frames are |
| conducted through Layer 1.                                            |
+-----------------------------------------------------------------------+
| **L1 frame** - A specific time slot of duration T~f~ identified by an |
| ALFN. The transmitted signal may be considered to consist of a series |
| of L1 frames.                                                         |
+-----------------------------------------------------------------------+
| **L1 frame rate -** The rate, equal to the reciprocal of the L1 frame |
| duration ![](media/image28.wmf){width="0.3888888888888889in"          |
| height="0.5555555555555556in"}, at which selected transfer frames are |
| conducted through Layer 1.                                            |
+-----------------------------------------------------------------------+
| **latency** - The time delay that a logical channel imposes on a      |
| transfer frame as it traverses Layer 1. One of the three              |
| characterization parameters. (see *robustness* and *transfer*).       |
+-----------------------------------------------------------------------+
| **Layer 1 (L1)** - The lowest protocol layer in the OSI Reference     |
| Model (also known as the Physical layer). Primarily concerned with    |
| physical connections and the transmission of data over a              |
| communication channel.                                                |
+-----------------------------------------------------------------------+
| **Layer 2 (L2)** - The Data Link layer in the OSI Reference Model.    |
| Primarily concerned with specific requirements for frames (such as    |
| blocks and packets), synchronization, and error control.              |
+-----------------------------------------------------------------------+
| **logical channel** - A signal path that conducts transfer frames     |
| from Layer 2 through Layer 1 with a specified grade of service.       |
+-----------------------------------------------------------------------+
| **lower sideband** - The group of OFDM subcarriers (subcarriers       |
| number -1 through -546) below the carrier frequency.                  |
+-----------------------------------------------------------------------+
| **OFDM Signal Generation** - The function that generates the          |
| modulated baseband signal in the time domain.                         |
+-----------------------------------------------------------------------+
| **OFDM subcarrier** - One of 1093 possible narrowband PSK-modulated   |
| carriers within the allocated channel, which, taken in aggregate,     |
| constitute the frequency domain representation of one OFDM symbol.    |
+-----------------------------------------------------------------------+
| **OFDM subcarrier mapping** -- The function that assigns the          |
| interleaved logical channels (interleaver partitions) to the OFDM     |
| subcarriers (frequency partitions).                                   |
+-----------------------------------------------------------------------+
| **OFDM symbol** - Time domain pulse of duration T~s~, representing    |
| all the active subcarriers and containing all the data in one row     |
| from the interleaver and system control data sequence matrices. The   |
| transmitted waveform is the concatenation of successive OFDM symbols. |
+-----------------------------------------------------------------------+
| **Open Systems Interconnection (OSI) Layered Model** - A multi-tiered |
| model of network architecture and a suite of protocols (a protocol    |
| stack) to implement it. Developed by the International Standards      |
| Organization (ISO) in 1978 as a framework for international standards |
| in heterogeneous computer network architecture (see Reference \[8\]). |
| The OSI architecture is logically divided into seven protocol layers, |
| from lowest to highest, as follows:                                   |
|                                                                       |
| Layer 1 - Physical layer                                              |
|                                                                       |
| Layer 2 - Data Link layer                                             |
|                                                                       |
| Layer 3 - Network layer                                               |
|                                                                       |
| Layer 4 - Transport layer                                             |
|                                                                       |
| Layer 5 - Session layer                                               |
|                                                                       |
| Layer 6 - Presentation layer                                          |
|                                                                       |
| Layer 7 - Application layer                                           |
|                                                                       |
| Each layer uses the layer immediately below it and provides a service |
| to the layer above.                                                   |
+-----------------------------------------------------------------------+
| **Orthogonal Frequency Division Multiplexing (OFDM)** - A parallel    |
| multiplexing scheme that modulates a data stream onto a large number  |
| of orthogonal subcarriers that are transmitted simultaneously (see    |
| *OFDM symbol*).                                                       |
+-----------------------------------------------------------------------+
| **parity** - In binary-coded data, a condition maintained so that in  |
| any permissible coded expression, the total number of "1"s or "0"s is |
| always odd, or always even.                                           |
+-----------------------------------------------------------------------+
| **Primary Extended (PX) sidebands** - The portion of the primary      |
| sideband that holds the additional frequency partitions (1, 2, or 4)  |
| inside the main partitions in the FM Extended Hybrid and All Digital  |
| waveforms. It consists, at most, of subcarriers 280 through 355 and   |
| -280 through -355.                                                    |
+-----------------------------------------------------------------------+
| **Primary Main (PM) sidebands** - The ten partitions in the primary   |
| sideband consisting of subcarriers 356 through 545 and -356 through   |
| -545.                                                                 |
+-----------------------------------------------------------------------+
| **primitive --** basic definition of control and/or data comprising a |
| service access point.                                                 |
+-----------------------------------------------------------------------+
| **pulse-shaping function** - A time-domain pulse superimposed on the  |
| OFDM symbol to improve its spectral characteristics.                  |
+-----------------------------------------------------------------------+
| **Quadrature Phase Shift Keying (QPSK)** - A form of digital phase    |
| modulation that assigns one of four discrete phases, differing by 90  |
| degrees, to the carrier. Each QPSK symbol conveys two bits of         |
| information.                                                          |
+-----------------------------------------------------------------------+
| **robustness** - The ability of a logical channel to withstand        |
| channel impairments such as noise, interference, and fading. There    |
| are eleven distinct levels of robustness designed into Layer 1 of the |
| FM air interface. One of the three characterization parameters. (see  |
| *latency* and *transfer*).                                            |
+-----------------------------------------------------------------------+
| **Scrambling** - The process of summing the input data bits with a    |
| pseudo-random bit stream to randomize the time domain bit stream.     |
+-----------------------------------------------------------------------+
| **secondary sidebands** - The sidebands to be added in the spectrum   |
| vacated by the analog signal. The secondary sidebands are divided     |
| into the Secondary Main (SM) sidebands containing ten frequency       |
| partitions, Secondary Extended (SX) sidebands containing four         |
| frequency partitions and the Secondary Protected (SP) sidebands       |
| containing two groups of twelve protected subcarriers. The secondary  |
| sidebands consist of subcarriers −279 through +279.                   |
+-----------------------------------------------------------------------+
| **Service Access Point (SAP)** - The interface between Layer 1 and    |
| Layer 2 at which the data from Layer 2 is formatted for delivery to   |
| Layer 1.                                                              |
+-----------------------------------------------------------------------+
| **service control units (SCU) --** Units of system control data       |
| transferred between Layer 2 and Layer 1.                              |
+-----------------------------------------------------------------------+
| **service data units (SDU) --** Units of user content transferred     |
| from Layer 2 to Layer 1.                                              |
+-----------------------------------------------------------------------+
| **service mode** - A specific configuration of operating parameters   |
| specifying throughput, performance level, and selected logical        |
| channels.                                                             |
+-----------------------------------------------------------------------+
| **spectral noise and emissions limit** - A specification limiting the |
| maximum level of out‑of‑band components of the transmitted signal.    |
+-----------------------------------------------------------------------+
| **spectral mapping** -- The association of specific logical channels  |
| with specific subcarriers or groups of subcarriers.                   |
+-----------------------------------------------------------------------+
| **system control -** Data from Layer 2 specifying service mode and    |
| analog diversity delay.                                               |
+-----------------------------------------------------------------------+
| **System Control Channel (SCCH)** - A channel consisting of control   |
| information from Layer 2 and status information from Layer 1.         |
+-----------------------------------------------------------------------+
| **system control data sequence --** A sequence of bits destined for   |
| each reference subcarrier representing the various system control     |
| components relayed between Layer 1 and Layer 2.                       |
+-----------------------------------------------------------------------+
| **system control processing** - The function that generates the       |
| system control data sequence.                                         |
+-----------------------------------------------------------------------+
| **system protocol stack** - The protocols associated with operation   |
| of the layers of the OSI Reference Model.                             |
+-----------------------------------------------------------------------+
| **transfer** -- A measure of the data throughput through a logical    |
| channel. One of the three characterization parameters. (see *latency* |
| and *robustness*).                                                    |
+-----------------------------------------------------------------------+
| **transfer frame** - An ordered, one-dimensional collection of data   |
| bits of specified length originating in Layer 2, grouped for          |
| processing through a logical channel.                                 |
+-----------------------------------------------------------------------+
| **transfer frame modulus** - The number of transfer frames in an L1   |
| frame.                                                                |
+-----------------------------------------------------------------------+
| **transfer frame multiplexer** - A device that combines two or more   |
| transfer frames into a single vector.                                 |
+-----------------------------------------------------------------------+
| **transfer frame rate** - The number of transfer frames per second    |
| entering the SAP and traversing Layer 1.                              |
+-----------------------------------------------------------------------+
| **transfer frame size** - The number of bytes in a transfer frame.    |
+-----------------------------------------------------------------------+
| **transmission subsystem** - The functional component used to format  |
| and up-convert the baseband IBOC waveform for transmission through    |
| the very-high frequency (VHF) channel.                                |
+-----------------------------------------------------------------------+
| **upper sideband** - The group of OFDM subcarriers (subcarriers       |
| number 0 through +546) above the carrier frequency.                   |
+-----------------------------------------------------------------------+
| **vector** - A one-dimensional array.                                 |
+-----------------------------------------------------------------------+

[^1]: 150 microseconds equates to a 28 mile propagation distance.

[^2]: GPS Locked stations are referred to as Level I: GPS-locked
    transmission facilities

[^3]: Level II: Non-GPS locked transmission facilities

[^4]: Amplitude Scale Factor per IBOC subcarrier

[^5]: Amplitude Scale factor in dB measured in 1 kHz bandwidth