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 FM Transmission Specification  2001 iBiquity Digital Corporation Doc. No. SY- TN- 5009
 IBOC FM Transmission Specification
 August 2001

 iBiquity Digital Corporation
 8865 Stanford Boulevard, Suite 202 20 Independence Boulevard
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 FM Transmission Specification  2001 iBiquity Digital Corporation Doc. No. SY- TN- 5009
 Columbia, Maryland 21045 (410) 872- 1530 Warren, New Jersey 07059 (908) 580- 7000
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 FM Transmission Specification  2001 iBiquity Digital Corporation Doc. No. SY- TN- 5009
 Table of Contents
 Contents 1 SCOPE .............................................................................................................................................................. 1
 2 ABBREVIATIONS, SYMBOLS, AND CONVENTIONS ................................................................................. 1 2.1 Introduction ............................................................................................................................................... 1
 2.2 Abbreviations and Acronyms .................................................................................................................... 1
 2.3 Presentation Conventions .......................................................................................................................... 1
 2.4 Mathematical Symbols .............................................................................................................................. 1
 2.4.1 Variable Naming Conventions .................................................................................................................. 1
 2.4.2 Arithmetic Operators ................................................................................................................................. 1
 2.5 FM System Parameters .............................................................................................................................. 1
 3 IBOC LAYERS.................................................................................................................................................. 1 3.1 FM Hybrid Layer 1................................................................................................................................... 1

 3.1.1 Introduction ........................................................................................................................................... 1
 3.2 Waveforms and Spectra............................................................................................................................. 1
 3.2.1 Hybrid Waveform ................................................................................................................................. 1
 3.2.2 Extended Hybrid Waveform ................................................................................................................. 1
 3.2.3 All Digital Waveform............................................................................................................................ 1
 3.3 System Control Channel............................................................................................................................ 1
 3.4 Logical Channels ....................................................................................................................................... 1
 3.4.1 Primary Logical Channels ..................................................................................................................... 1
 3.4.2 Secondary Logical Channels ................................................................................................................. 1
 3.4.3 Logical Channel Functionality .............................................................................................................. 1
 3.5 Functional Components............................................................................................................................. 1
 3.5.1 Service Access Points............................................................................................................................ 1
 3.5.2 Scrambling ............................................................................................................................................ 1
 3.5.3 Channel Encoding ................................................................................................................................. 1
 3.5.4 Interleaving ........................................................................................................................................... 1
 3.5.5 System Control Processing.................................................................................................................... 1
 3.5.6 OFDM Subcarrier Mapping .................................................................................................................. 1
 3.5.7 OFDM Signal Generation ..................................................................................................................... 1
 3.5.8 Transmission Subsystem ....................................................................................................................... 1
 4 FUNCTIONAL DESCRIPTION......................................................................................................................... 1 4.1 Introduction ............................................................................................................................................... 1

 4.2 Functionality.............................................................................................................................................. 1
 4.3 Transmission Subsystem ........................................................................................................................... 1
 4.3.1 Introduction ........................................................................................................................................... 1
 4.4 Functional Components............................................................................................................................. 1
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 FM Transmission Specification  2001 iBiquity Digital Corporation Doc. No. SY- TN- 5009
 4.4.1 Symbol Concatenation .......................................................................................................................... 1
 4.4.2 Up- Conversion ...................................................................................................................................... 1
 4.4.3 Diversity Delay ..................................................................................................................................... 1
 4.4.4 Analog FM Modulator........................................................................................................................... 1
 4.4.5 Analog/ Digital Combiner ...................................................................................................................... 1
 4.4.6 Use of On Channel Repeaters ............................................................................................................... 1
 4.4.7 GPS Synchronizarion ............................................................................................................................ 1
 5 WAVEFORMS AND SPECTRA....................................................................................................................... 1 5.1 Introduction ............................................................................................................................................... 1

 5.2 Frequency Partitions and Spectral Conventions ........................................................................................ 1
 5.3 Hybrid Spectrum ....................................................................................................................................... 1
 5.4 Extended Hybrid Spectrum........................................................................................................................ 1
 5.5 All Digital Spectrum.................................................................................................................................. 1
 SUPPLEMENT A FM TRANSMISSION SPECIFICATIONS............................................................................ 1 A. 1 Introduction ............................................................................................................................................... 1

 A. 2 Synchronization Tolerances....................................................................................................................... 1
 A. 2.1 Analog Diversity Delay......................................................................................................................... 1
 A. 2.2 RF Carrier Frequency and OFDM Symbol Clock................................................................................. 1
 A. 2.3 GPS Phase Lock.................................................................................................................................... 1
 A. 3 IBOC Noise and Emissions Limits ............................................................................................................ 1
 A. 3.1 Analog Waveform................................................................................................................................. 1
 A. 3.2 Hybrid and Extended Hybrid Waveforms ............................................................................................. 1
 A. 3.3 All Digital Waveform............................................................................................................................ 1
 A. 4 Digital Sideband Levels............................................................................................................................. 1
 GLOSSARY ............................................................................................................................................................. 1
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 Scope
 The iBiquity Digital Corporations 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.
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 Abbreviations, Symbols, and Conventions
 Introduction
 Section 0 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
 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
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 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
 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

 Variable Naming Conventions
 The variable naming conventions defined below are used throughout this document.
 Category Definition Examples Lower and upper case letters Indicates scalar quantities i, j, J, g11

 Underlined lower and upper case letters Indicates vectors u, V
 Double underlined lower and upper case letters Indicates two- dimensional matrices u, V
 [i] Indicates the i th element of a vector, where i is a non-negative
 integer
 u[ 0], V[ 1]

 [ ] Indicates the contents of a vector v = [0, 10, 6, 4]
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 Diversity Delay Frames Ndd none 3 = number of L1 frames of diversity delay 3
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 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
 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
 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
 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
 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
 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.
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 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
 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 0 through Subsection 0 for details.

 Primary Logical Channels
 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
 Approximate Information Rate (kbps) Service
 Mode P1 P2 P3 PIDS Waveform

 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
 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
 Approximate Information Rate (kbps) Service
 Mode S1 S2 S3 S4 S5 SIDS Waveform

 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
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 Logical Channel Functionality
 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
 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.
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 Layer 2
 Scrambling
 Channel Encoding
 Interleaving
 OFDM Subcarrier Mapping
 OFDM Signal Generation
 Transmission Subsystem

 P1
 X
 System Control
 Processing

 SCCH

 R
 Control/
 Status

 Analog, SCA
 Sources

 P2 P3 PIDS S1 S2 S3 S4 S5 SIDS
 Layer 1 SAP

 y n (t)
 s( t)

 Control/ Status
 Baseband
 Figure 0- 1 FM Air Interface Layer 1 Functional Block Diagram
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 Service Access Points
 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
 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
 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 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
 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
 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 Ts to

 produce one output vector X, 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
 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, yn( t), defining one OFDM

 symbol.
 Transmission Subsystem
 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
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 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.
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 From OFDM Signal Generation
 VHF FM IBOC Waveform
 Symbol Concatenation
 Up- Conversion

 From Analog Source

 Analog FM Modulator
 Diversity Delay (	)

 Hybrid and Extended Hybrid
 waveforms only

 y n (t) m( t)
 +
 m( t- 	)
 a( t)

 s( t)
 z( t)

 From Layer 2
 DD (via SCCH)

 y( t)
 (optional) SCA Subcarriers

 Figure 0- 2 Hybrid/ Extended Hybrid Transmission Subsystem Functional Block Diagram
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 Doc. No. SY- TN- 5009 18
 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
 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 stations service areas limit analog or digital performance.

 iBiquitys 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
 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 .

 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
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 Waveforms and Spectra
 Introduction
 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
 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- 1

 (ordering A) and Figure 0- 2 (ordering B). The position of the reference subcarrier (ordering A or B) varies with the location of the frequency partition within the spectrum.

 Reference
 d1 d2 d3 d4 d5 d6 d7 d8 d9 d10 d11 d12 d13 d14 d1 5 d16 d17 d18

 Reference Subcarrier

 Frequency
 18 Data Subcarriers

 Figure 0- 1 Frequency Partition Ordering A
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 280 299 318 337 356 375 394 413 432 451 470 489 508 527 546 0 19 38 57 76 95 114 133 152 171 190 209 228 247 266 279
 Frequency 30 41 42 43 44 4546 47 48 49 50 51 52 53 54 55 56 57 58 59 60

 Upper Secondary Sideband
 Upper Primary Sideband

 31 32 33 34 35 36 37 38 39 40
 Reference Subcarrier Numbers

 OFDM Subcarrier
 Numbers

 Figure 0- 4 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
 The digital signal is transmitted in PM sidebands on either side of the analog FM signal, as shown in Figure 0- 5. 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, a0. The amplitude scaling factor is described in Appendix A. Table 0- 1 summarizes the upper and
 lower Primary Main sidebands for the Hybrid waveform.
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 Analog FM Signal
 198,402 Hz 129,361 Hz
 0 Hz

 Primary Primary
 Upper Digital Sideband Lower Digital Sideband

 Main Main

 # 356 # 546
 # 0

 -129, 361 Hz # -356 -198, 402 Hz # -546

 10 frequency partitions 10 frequency partitions

 Additional Reference
 Subcarrier

 Additional Reference
 Subcarrier

 Figure 0- 5 Spectrum of the Hybrid Waveform Service Mode MP1
 Table 0- 1 Hybrid Waveform Spectral Summary Service Mode MP1

 Sideband
 Number of Frequency
 Partitions
 Frequency Partition
 Ordering Subcarrier Range

 Subcarrier Frequencies
 (Hz from channel
 center)

 Ampl.
 Scale
 Factor Frequency Span

 (Hz) Comments

 Upper Primary
 Main 10 A
 356 to
 546
 129,361 to
 198,402 ao 69,041

 Includes additional
 reference subcarrier
 546

 Lower Primary
 Main 10 B
 -356 to
 -546
 -129,361 to
 -198,402 ao 69,041

 Includes additional
 reference subcarrier -
 546
 Note: Refer to Appendix A for details regarding the amplitude scale factors shown above.
 Extended Hybrid Spectrum
 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- 6. 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
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 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, a0, as the Primary Main sidebands. The amplitude scaling factor is described in Appendix A. Table 0- 2 summarizes the Upper and Lower Primary sidebands for the Extended
 Hybrid waveform.

 Analog FM Signal
 198,402 Hz 129,361 Hz
 115, 553 Hz (# 318)
 0 Hz (# 0)

 Additional Reference
 Subcarrier
 Primary Primary

 Upper Digital Sideband

 Extended
 Main Main
 Extended

 101,744 Hz (# 280)
 122,457 Hz (# 337) (# 546)
 (# 356) -198, 402 Hz (# -546) -129,361 Hz (# -356)

 -115, 553 Hz (# -318)
 -101, 744 Hz (# -280)

 -122,457 Hz (# -337)

 10 frequency partitions 10 frequency partitions 1, 2, or 4 frequency
 partitions

 1, 2, or 4 frequency
 partitions

 Lower Digital Sideband Additional Reference
 Subcarrier

 Figure 0- 6 Spectrum of the Extended Hybrid Waveform Service Modes MP2 through MP4
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 Table 0- 2 Extended Hybrid Waveform Spectral Summary Service Modes MP2 through MP4
 Sideband
 Number of Frequency
 Partitions
 Frequency Partition
 Ordering Subcarrier Range

 Subcarrier Frequencie
 s (Hz from channel
 center)

 Ampl. Scale
 Factor Frequency
 Span (Hz) Comments

 Upper Primary
 Main 10 A
 356 to
 546
 129,361 to
 198,402 ao 69,041

 Includes additional
 reference subcarrier
 546

 Lower Primary
 Main 10 B
 -356 to
 -546 -129,361 to -198,402 ao 69,041

 Includes additional
 reference subcarrier
 -546
 Upper Primary

 Extended (1 frequency
 partition) 1 A
 337 to
 355
 122,457 to
 128,997 ao 6,540 none
 Lower Primary

 Extended (1 frequency
 partition) 1 B
 -337 to
 -355 -122,457 to -128,997 ao 6,540 none
 Upper Primary

 Extended (2 frequency
 partitions) 2 A
 318 to
 355
 115,553 to
 128,997 ao 13,444 none
 Lower Primary

 Extended (2 frequency
 partitions) 2 B
 -318 to
 -355
 -115, 553 to
 -128,997 ao 13,444 none
 Upper Primary

 Extended (4 frequency
 partitions) 4 A
 280 to
 355
 101,744 to
 128,997 ao 27,253 none
 Lower Primary

 Extended (4 frequency
 partitions) 4 B
 -280 to
 -355
 -101, 744 to
 -128,997 ao 27,253 none
 Note: Refer to Appendix A for details regarding the amplitude scale.
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 All Digital Spectrum
 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- 7.

 198,402 Hz (# 546)
 101,744 Hz (# 280)
 129,361 Hz (# 356)
 0 Hz
 69,404Hz

 97,021 Hz

 Main Extended Extended Main
 Primary Secondary Primary Secondary
 Lower Digital Sideband

 Extended Extended
 Main Main

 Protected Protected

 101,381 Hz (# 279)
 (# 0)
 (# 267)

 (# 191)

 -101,381 Hz (# -279)

 -69,404 Hz (# -191)
 -97,021 Hz (# -267)
 -101,744 Hz (# -280)
 -129, 361 Hz (# -356) -198,402 Hz (# -546)

 10 frequency partitions 10 frequency partitions
 10 frequency partitions 10 frequency partitions

 4 frequency
 partitions
 4 frequency
 partitions

 4 frequency
 partitions
 4 frequency
 partitions

 Upper Digital Sideband
 12
 subcarriers

 Additional Reference
 Subcarrier
 Additional Reference
 Subcarrier

 Additional Reference
 Subcarrier
 Additional Reference
 Subcarrier

 12
 subcarriers

 Figure 0- 7 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- 1 and Figure 0- 2.

 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, a2, as indicated in Table 0- 3. The subcarriers within the Secondary Main,
 Secondary Extended and Secondary Protected sidebands are uniformly scaled by an amplitude scale factor having four discrete levels a4  a7, as indicated in Table 0- 3. Table 0- 3 summarizes
 the upper and lower, primary and secondary sidebands for the All Digital waveform.
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 Table 0- 3 All Digital Waveform Spectral Summary Service Modes MP5 through MP7, MS1 through MS4
 Sideband
 Number of
 Frequenc y
 Partitions
 Frequency Partition
 Ordering Subcarrie r Range

 Subcarrier Frequencie
 s (Hz from channel
 center)

 Ampl. Scale
 Factor Frequency
 Span (Hz) Comments

 Upper Primary
 Main 10 A
 356 to
 546
 129,361 to
 198,402 a2 69,041

 Includes additional
 reference subcarrier 546

 Lower Primary
 Main 10 B
 -356 to
 -546
 -129,361 to
 -198,402 a2 69,041

 Includes additional
 reference subcarrier -
 546
 Upper Primary

 Extended 4 A
 280 to
 355
 101,744 to
 128,997 a2 27,253 none
 Lower Primary

 Extended 4 B
 -280 to
 -355
 -101,744 to
 -128,997 a2 27,253 none

 Upper Secondary
 Main 10 B
 0 to
 190
 0 to
 69,041 a2 69,041

 Includes additional
 reference subcarrier 0

 Lower Secondary
 Main 10 A
 -1 to
 -190
 -363 to
 -69,041 a2 68,678 none
 Upper Secondary

 Extended 4 B
 191 to
 266
 69,404 to
 96,657 a4  a7 27,253 none
 Lower Secondary

 Extended 4 A
 -191 to
 -266
 -69,404 to
 -96,657 a4  a7 27,253 none

 Upper Secondary
 Protected N/ A N/ A
 267 to
 279
 97,021 to
 101,381 a4  a7 4,360

 Includes additional
 reference subcarrier 279

 Lower Secondary
 Protected N/ A N/ A
 -267 to
 -279
 -97,021 to
 -101,381 a4  a7 4,360

 Includes additional
 reference subcarrier 279

 Note: Refer to Appendix A for details regarding the amplitude scale factors.
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 Supplement A FM Transmission Specifications
 A. 1 Introduction
 This appendix presents the key transmission specifications for the FM IBOC system, as described in the body of this document.

 A. 2 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.

 A. 2.1 Analog Diversity Delay
 The absolute accuracy of the analog diversity delay in the transmission signal will be within 10 microseconds (sec) 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.

 A. 2.2 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.
 A. 2.3 GPS Phase Lock
 For Level I transmission facilities, all transmissions will maintain phase lock to absolute GPS time within  1 sec.

 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.
 A. 3 IBOC Noise and Emissions Limits
 The noise and emissions limits are as specified in Subsection A. 3.1 through Subsection A. 3.3.
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 A. 3.1 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- 1.

 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- 1 FCC RF Spectral Emissions Mask
 Offset from Carrier Frequency (kHz) Power Spectral Density Relative to Unmodulated Analog FM Carrier (dBc/ kHz)

 120 to 240 -25
 240 to 600 -35
 greater than 600 -80, or -43 - (10  log10 [power in watts]), whichever is less, where [power in watts] refers to the total unmodulated

 transmitter output carrier power

 A. 3.2 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.
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 -350 -400 -300 -250 -200 -150 -100 -50 0 50 100 150 200 300 350 250 400
 Frequency offset, KHz

 Hybrid HPA Noise Performance Measured without Analog Carrier Present

 dB
 in
 a
 1
 kHz

 bandwidth

 -90

 0
 -20
 -30
 -40

 -60

 -100

 -10
 -50
 -70
 -80

 -450 -500 -550 -600 -650 450 500 550 600 650

 Nominal Hybrid Carrier Power Spectral Density
 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 to Carrier Level, dB/ kHz
 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

 A. 3.3 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.
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 -350 -400 -300 -250 -200 -150 -100 -50 0 50 100 150 200 300 350 250 400
 Frequency offset, KHz

 All Digital HPA Noise Performance

 dB
 in
 a
 1
 kHz

 bandwidth

 -90

 0
 -20
 -30
 -40

 -60

 -100

 -10
 -50
 -70
 -80

 -450 -500 -550 -600 -650 450 500 550 600 650

 Nominal All Digital Power Spectral Density
 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 Relative to Carrier Level, dB/ kHz
 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

 A. 4 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
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 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
 Amplitud e Scale

 Factor Notation
 Amplitude Scale Factor 4
 (relative to total analog FM power)
 Scale Factor 5 (dB, relative to total

 analog FM power)
 Hybrid MP1 Primary a0 5.123 x 10 -3 -41.39
 Extended Hybrid MP2  MP7 Primary a0 5.123 x 10 -3 -41.39

 MP- 5  MP7 Primary a2 1.67x 10 -2 -31.39
 Secondary a4 5.123 x10 -3 -41.39
 Secondary a5 3.627 x 10 -3 -44.39
 Secondary a6 2.567 x 10 -3 -47.39

 All Digital
 MS1  MS4
 Secondary a7 1.181 x 10 -3 -50.39

 4 Amplitude Scale Factor per IBOC subcarrier
 5 Amplitude Scale factor in dB measured in 1 kHz bandwidth
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 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).
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 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 Ts, 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.
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 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.
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