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NPR Labs
Deployment of Digital Audio
Broadcasting in the U.S. and Abroad
John Kean
NPR Labs, Washington DC
jkean@npr.org
Frequency Bands of Terrestrial DAB
Source: World Broadcasting Unions
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DAB (Eureka-147)
• Initiated as a European research project in
the 1980s for mobile, portable and fixed
• 3 main elements, all ETSI TS 102 563
• Digital transmission coding & multiplexing (5-7
services)
• COFDM modulation, 1.54 spectrum
• Mostly L-Band, but in U.K., 12.5 MHa of Band III
(217.5-230)
• MUSICAM (MPEG-2 layer III) perceptual coding
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International Rollout of DAB, DAB+
World DMB Forum
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Now in more than 20 countries, >1000 stations
Reaching >100 million in Europe, 500 million worldwide
UK DAB listeners estimated at 20 million
Shown to be ~ 3.2 times more spectrum-efficient than FM
Also DMB (Digital Multimedia Broadcasting)
• Usually considered a digital mobile video platform
• MPEG-2 transport stream packets with additional block coding
• In use in Korea, Germany, numerous test countries
• DAB+ standardized in 2006
• Added new HE-AAC v2 audio codec, surround sound
• New frequency bands
• Launches in Australia, Switzerland, Italy, Germany, etc.
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International Rollout of DAB Variants
source: World DMB Forum
Regular services
Australia, Belgium, China, Czech Republic, Denmark, Germany, Hong Kong,
Malta, Netherlands, Norway, South Korea, Sweden, Switzerland, United Kingdom,
Canada
Trials or regulation to permit
Austria, Brunei Darussalam, Chinese Taipei, Croatia, France, Ghana, Hungary,
Indonesia, Ireland, Israel, Italy, Kuwait, Malaysia, New Zealand, Poland, South
Africa, Spain, Vietnam
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L-Band Frequencies Assigned to DAB
Block
Center Frequency
(MHz)
LA
1452.960
LB
1454.672
LC
1456.384
LD
1458.096
LE
1459.808
LF
1461.520
LG
1463.232
LH
1464.944
LI
1466.656
LJ
1468.368
LK
1470.080
LL
1471.792
LM
1473.504
LN
1475.216
LO
1476.928
LP
1478.640
NPR Labs
• Used for T-DAB (terrestrial)
broadcasts
• WorldSpace satellite
broadcasts in the 1467–
1492 MHz L sub-band
• Canada uses slightly
different central
frequencies for L-band DAB
• In many European
countries DAB is limited to
part of Band III, due to
television and mobile two
way radio
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Digital Radio Mondiale
• “DRM” is an international non-profit consortium
• Radio France Internationale, TéléDiffusion de France,
BBC World Service, Deutsche Welle, Voice of America,
Telefunken (now Transradio) and Technicolor SA
• Open-standards design and implementation of platform
• Principle: bandwidth is limited element, and
computer processing power is cheap; modern CPUintensive RF & audio compression techniques
enable more efficient use of available spectrum
• Can deliver FM-comparable sound quality on
frequencies below 30 MHz (LW, MW, SW)
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DRM: One-Fifth the Power
Required for AM
BBC Report on Plymouth UK tests
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Digital Radio Mondiale
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64-QAM, 16-QAM and 4-QAM schemes
• 6.1 - 34.8 kbit/s for a 10 kHz channel
• 72 kbit/s using standard 20 kHz channel
• Allows very-long-distance signal propagation
(a few watts on 26 MHz to 100’s of kW on
LW)
• Decodable with PC software and sound card
• Endorsed by the ITU, approved as international standard
• Australian govt. placed embargo on 6 - 26 MHz potentially
suitable for use by DRM until spectrum planning can be
completed
• U.S. FCC rules part 73.758 (for HF-band broadcasting): "For
digitally modulated emissions, the Digital Radio Mondiale
(DRM) standard shall be employed."
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DRM+
New, for VHF Transmission
30-174 MHz VHF band
100 kHz channelization
COFDM, 64-, 16-, 4-QAM
Using HE-AAC audio codecs
SFNs supported
Up to 4 program services
1 station, 1 frequency
May coexist near linked FM
signal, also Band III
• ETSI, official in 2009
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DRM+
New, for VHF Transmission
• Internationally agreed norms for FM band
(88-108 MHz) protection
• High power field trial in UK, Sri Lanka etc.
• ITU standardization
• Limited choices in receivers
• Uncertain numbers of listeners
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HD Radio
• “In-Band On-Channel”digital transmission in FM
and AM bands
• Only system approved for digital AM & FM by FCC
• Outgrowth of DAB research in mid-late 1990s
• Led primarily by large U.S. broadcast interests
• Desire for one-to-a-channel assignment
• Private company (iBiquity Digital) established and
branded as “HD Radio”
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HD Radio
• Originally referred to a “IBAC” (In-band
Adjacent-channel) system – FM shown
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HD Radio
• Implementation benefits
• FM receivers not made obsolete
• Propagation of FM band superior to L-band
• Presumed ability to utilize existing transmitter
system, avoid development of new band
• National Radio Systems Committee support
• ITU Recommendation BS.1114-4, adopted
May 2003, classified as “Digital System C”
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HD Radio Development
• In U.S. ~2100 stations, >95% FM, <5% AM
• Adoption in Mexico, Phillipines, so far
• “Advanced interest” in several countries
Source: iBiquity
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HD Radio Development
• Initial estimates of coverage at 1% power of FM were
exaggerated
• Indoor and portable coverage were substantially smaller
than FM host
• NRSC and iBiquity promoted and won power increase
Hybrid FM Signal
With OFDM Subcarriers
Desired FM Channel
(200 kHz)
6 dB
-33 dBc
-43 dBc
OFDM Subcarriers
at -10 dBc
OFDM Subcarriers
of Adj. Channel
at -20 dBc
NPR Labs
OFDM Subcarriers
at -10 dBc
FM Carrier
of Adj. Channel
OFDM Subcarriers
of Adj. Channel
at -20 dBc
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HD Radio Development
• In 2010, FCC adopted a blanket increase
• 4X power increase, and up to 10X under signal
clearance conditions to first-adjacent stations
(determined in research by NPR Labs)
• “Interference remediation” required for proven digital-toanalog FM interference cases
• No U.S. standards to protect HD Radio from
interference
• IBOC DAB is subject to received interference
• FM rules consider only analog-to-analog allocations –
are ignorant of analog-to-digital issues
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Summary
• Technical evolution of DAB in all forms has
arguably been slow
• Interest by consumers to DAB in the U.S. is
still weak after a decade, despite the large
number of digital FM stations in operation
• Analog FM remains the majority radio
service
• Will the future of digital audio broadcasting
move faster? Will it collide with other forms
of wireless digital media?
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