AM broadcasting is, with more than 2 billion AM radio receivers in use worldwide, still one of the most
important distribution media, despite the Internet. Although a large proportion of the world population is still
listening daily to the AM band, the number of listeners is slowly declining (most likely due to limited audio
quality and annoying interference).
The first radio broadcast for entertainment and music was transmitted to a small public on the 24th of
December 1906 in a test broadcast from Brant Rock, Massachusetts in the USA. This pioneering broadcast
was achieved after years of development work by Reginald Aubrey Fessenden (1866-1932) who built a
system capable of wireless transmission and reception using amplitude modulation in the AM band. AM
transmission represents the simplest method for audio broadcasting and has been available since 1920, with
regular broadcasts of news and entertainment such as drama, comedy and music. AM broadcasts often
suffer from annoying interference and fading, and AM signal quality deteriorates gradually with distance and
signal strength, typical for analog modulation methods. Due to its efficient nationwide or intercontinental
coverage, many long-range broadcasters still use this technology, for example BBC World Service and
broadcasters in the Middle East.
FM broadcasting has been available in mono since the late 1930’s and in stereo since the early 1960’s. It
has since reclaimed many listeners from the AM band due to improved sound quality, and is a popular and
widespread modulation format that offers good audio sound quality and reasonable robustness to
interference in comparison to AM broadcasting. The FM band usually covers 87.5 - 108 MHz and is typically
divided into a 100 kHz channel grid. FM quality deteriorates gradually with distance and signal strength,
typical to analog modulation methods. The FM stereo mode is more fragile and thus less robust, being
more sensitive to multipath, noise and interference in comparison to FM mono.
Digital Audio Broadcasting (DAB) has been available since 1995 and is slowly gaining territory in some
countries due to its robustness to interference and the possibility to offer high audio quality without hiss and
interference. DAB is substantially more spectrum efficient than analog modulation techniques like FM or AM.
DAB exhibits the typical “brick-wall effect”, where the signal deteriorates and drops rapidly when signal
strength falls below a certain critical threshold. The modulation used for DAB is coded orthogonal frequency
division multiplexing (COFDM), a very efficient and robust modulation method which however sets stringent
demands on transmitter technology due to the high crest-factor of OFDM signals. The bandwidth of one
DAB multiplex is 1536 kHz.
DAB+, the recent upgrade (2007) of the DAB standard, includes a substantially more effective audio coder
(HE-AAC), and offers approximately twice the programme channels (around 15) in a single wideband
multiplex. DAB broadcasts in the VHF band III (174 to 240 MHz). DAB can transmit multimedia features
such as program-associated text and metadata, 5.1 surround sound, slideshows and videos etc to add
value to the listener.
DVB-T2-Lite. DVB-T2 has been in existence since 2008 and was introduced in Sweden in 2010 as the
second generation digital television standard. DVB-T2 is a more efficient and enhanced technology
compared to DVB-T and is intended for stationary reception, and is not suitable for mobile reception. A
more robust subset of the DVB-T2 standard was introduced in 2011. DVB-T2-Lite is optimized for mobile
reception such as mobile digital radio and TV. DVB-T2-Lite has reduced circuit complexity and relaxed
memory requirements and therefore consumes less power. DVB-T2-Lite for digital radio has a RF bandwidth
of 1700 kHz (slightly more than DAB 1585 kHz). DVB-T2 exhibits the typical "brick wall" effect, where the
signal abruptly deteriorates and disappears when the signal strength falls below a certain critical threshold.
The modulation used for DVB-T2 is "coded orthogonal frequency division multiplexing" (COFDM), a highly
effective and robust modulation method. This however, places high demands on the transmitter and
transmitting equipment because the of OFDM signals high crest-factor. DVB-T2-Lite is significantly more
spectrum-efficient than analog modulation such as FM or AM. Additionally, DVB-T2-Lite due to its modern
radio modem technology, offers significantly higher spectrum efficiency, in the order of 2-3 times as many
programme channels compared to DAB+ (under similar conditions). The DVB-T2 standard offers the
efficient HE-AAC audio codec, Dolby AC-3, Dolby Enhanced AC-3 , AMR-WB+ and AMR-WB speech codec
and H.264/AVC video codec (4:3/16:9). Maximum bit rate is 4.0 Mbit/s compared to DAB+ 1.056 Mbit/s.
Digital audio broadcasting using DVB-T2-Lite is "On-Air" in Copenhagen since June 2012.
Digital Radio Mondiale (DRM30) is a comparatively new digital radio standard that revitalizes the
traditional AM broadcasting band with good, almost FM like, sound quality and interference-free reception.
DRM30 has been available since 2003 for broadcasting in the band below 30 MHz (LW, MW, SW) and is
gaining in popularity in numerous countries due to its robustness against interference, the good FM-like audio
quality and the potential for substantial coverage areas. A single DRM30 transmitter can reach an entire
country or even a continent. DRM30 is currently being implemented in India and reaches (January 2014)
nearly 500 million people and will reach 70% of the population in 2016. It is believed that Pakistan and
Bangladesh will follow.
DRM is much more spectrum efficient than analog modulation techniques such as FM or AM, (and more
spectrum efficient than DAB). DRM exhibits the typical “brick-wall effect”, where the signal deteriorates
rapidly when the signal strength falls below a certain critical threshold. The modulation used for DRM is as
for DAB, coded orthogonal frequency division multiplexing (COFDM), a highly effective and robust
modulation method that however, sets stringent demands on the transmitter due to the high crest-factor of
OFDM signals. DRM uses the acclaimed and highly efficient HE-AAC codec that has recently been developed
and improved for low and extremely low bitrates, the xHE-AAC, and thus is very valuable especially for long-
range DRM30 broadcasting (the undersigned initiated the SBR, Spectral Band Replication and PS, Parametric
Stereo project and thus as inventor contributed to the success of the HE-AAC and xHE-AAC codecs).
DRM30 opens up the opportunity to cost-effectively cover extremely large areas and intercontinental
broadcasting on the AM band using only one transmitter, eliminating annoying interference and fading so
common to analog AM broadcasting. Such a single DRM30 transmitter of 1 megawatt could cover all of
Sweden from north to south.
DRM30 can deliver multimedia features like program-associated text and metadata, 5.1 surround sound,
slideshows, video, emergency warnings, data services etc that add value to the listener. The DRM mini-
multiplex is designed to carry up to four different program channels.
Digital Radio Mondiale (DRM+) is a new extension to the DRM30 standard and moves DRM into the
VHF bands I - III (TV, FM and DAB bands). This broadcasting standard has been available since 2009.
DRM+ can broadcast the same features as DRM30 such as program-associated text and metadata, 5.1
surround sound, slideshows, video, emergency warnings, data services etc that add value to the listener.
DRM is currently the only available broadcasting technology that covers the entire RF broadcasting
spectrum, from 153 kHz to 230 MHz (LW/MW/SW/VHF I+II+III). The RF bandwidth of one DRM mini-
multiplex spans from 4.5 kHz (DRM30) to 96 kHz (DRM+) depending on the mode used, and is very
spectrum efficient. Both DRM30 and DRM+ use the acclaimed and highly efficient HE-AAC codec. The HE-
AAC codec has recently been upgraded to a new standard, xHE-AAC, with improved performance mainly at
low and extremely low bit rates. DRM+ will be introduced in the FM band in India.
HD-Radio was introduced in the US in 2002 and is a trademark of iBiquity's (in-band-on-channel, IBOC)
digital broadcasting technology used in AM and FM bands in the US and elsewhere. IBOC in hybrid mode,
transmits audio using two digital sidebands, placed immediately above and immediately below a station's
analog or FM signal that is situated in the middle. Thus simulcast is imbedded in this technology being able
to simultaneously broadcast both analog and digital. This system also includes fully digital-only modes. HD-
Radio uses the HDC audio codec that is similar but not compatible with HE-AAC and includes SBR and PS.
However, HD-Radio will not be discussed further as this technology is not on the list of possible systems for
digital broadcasting in Sweden.
ISDB-Tsb (Integrated Services Digital Broadcasting - Terrestrial, sound broadcasting) was introduced in
Japan in 2003 for digital audio broadcasting in the VHF/UHF band. The transmissions used a limited
frequency range of 188-192 MHz (VHF band III) which was moved in 2011 to UHF band 470-770 MHz. RF
bandwidth is 432 kHz (somewhat in the range between DAB+ and DRM+) but can be expanded
incrementally. The AAC codec is used with the option for HE-AAC. ISDB-Tsb will not be discussed further,
since this technology is not on the list of possible systems for digital broadcasting in Sweden.
The general opinion is that systems like DAB+ or DVB-T2-Lite are better suited for large-scale nationwide
broadcasters and commercial broadcasters aiming at covering larger geographic areas nationwide. This is
due to DAB+ substantially wider multiplex - 1536 kHz bandwidth - consuming substantial RF space. In order
to effectively utilize this RF space, it is necessary to fill the DAB multiplex with a sufficient number of
programme channels (in the order of 15 per multiplex). Similar applies to DVB-T2-Lite, a recently developed
standard for the distribution of mobile digital radio and TV, also in the VHF band III. The DVB-T2-Lite multiplex
has a bandwidth of 1700 kHz. To effectively utilize this RF space, it is necessary to fill the DVB-T2-Lite
multiplex with a sufficient number of program channels (in the order of 30-50 per multiplex).
DRM+ on the other hand, uses only a RF bandwidth of 96 kHz for the DRM+ mini-multiplex, thus
consuming only about 50% the spectrum of an analog FM channel and about 6% of a DAB multiplex.
DRM+ supports up to four different radio programme channels in this narrow bandwidth.
DRM can be used for small-scale installations requiring no more infrastructure than what is normal for a
typical FM-transmitter site. Thus the DRM local radio broadcaster or community radio broadcaster typically
can fund his own transmitter and own his own station in the traditional way.
However, such a transmitter site can be infinitely expanded if needed, to cover a wider bandwidth with
multiple broadcasts and many programme channels, like a DAB+ multiplex, or even wider if asked for.
Thus channel expansion is possible according to demand using DRM.
The major advantage of both DAB+, DVB-T2-Lite and DRM+ broadcast systems in comparison to analog
FM, is the possibility to broadcast using SFN (Single Frequency Network). This means that contrary to
analog broadcasting, digital broadcasting can use the same synchronized broadcast frequency nationwide
for a particular program channel (say SR P1 for example). This means that when the Swedish Radio is
broadcasting its four program channels nationwide, P1, P2, P3 and P4, these would only occupy four
different frequencies in total. SFN would thus release RF frequency space, giving an added value to the
mobile and travelling listener (no need for frequency retuning), and would significantly simplify and improve
frequency planning (PTS).
Large-scale nationwide broadcasts, using SFN or not, require a comparatively complex infrastructure
typically run by government agencies or large corporations. This applies to the use of both DAB+, DVB-T2-
Lite and DRM+ in large-scale installations.
In a future broadcast scenario, DAB+ or DVB-T2-Lite and DRM+ should coexist, and the advantage of
each standard could be exploited to its best extent and according to the broadcasters’ needs and
decisions. DAB+ or DVB-T2-Lite could preferably be used for nationwide, large-scale broadcasts by
government and commercial broadcasters. DRM+ could advantageously be used for local broadcasters
and small community radio broadcasters. DRM30 could be used very cost-effectively to cover Sweden and
for intercontinental broadcasts, reaching the world over land and sea including international shipping.
If found feasible, DRM+ could replace DAB+ or DVB-T2-Lite. In addition, DRM+ together with DRM30 offer
an unprecedented digital broadcasting system that covers all broadcast bands from 156 kHz to 230 MHz,
thus covering the needs of intercontinental broadcasters, nationwide and local broadcasters down to small
community and campus radio broadcasters.
DVB-T2-Lite may replace DAB+ as DVB-T2 is a substantially more modern and more efficient system that is
fully developed, with full coverage in Sweden for digital television. Digital audio broadcasting using DVB-T2-
Lite is "On-Air" in Copenhagen since June 2012.
As both digital radio systems, DRM+ and DVB-T2-Lite, recently were standardized, radios are still absent on
the market. Radio receivers for DVB-T2-Lite and DRM+ are expected during 2014-2015.
Spectrum efficiency in general is a measure on how efficient the radio modem technology, the
modulation method, and the audio coding are. For example, the number of programming channels that will
fit a given sound quality level at a given RF bandwidth and coverage area.
Energy efficiency (transmitter side) is somewhat correlated with spectrum efficiency, i.e. energy
efficiency includes the energy used by the transmitter which is required to cover a given geographical area
of listeners, with a certain number of program channels and without generating unnecessary heat loss.
Energy efficiency (receiver side) is dependent on circuit complexity, memory size and circuit speed
(MIPS/MFLOPS) i.e. battery drain and/or power consumption of the receiver.
Bandwidth Flexibility means that the RF bandwidth can be scaled relative to the number of program
channels needed, from one or a few, to many programme channels. I.e. means to effectively utilize the
bandwidth based on demand. Even the support of several different and useful frequency bands is an
Multimedia Flexibility means that different coding technologies can be used e.g. audio coding, speech
coding and video coding as well as various means of transmission of text information and data, and
interactivity with the Internet and more.
Suitability for large scale operation involves infrastructure and nationwide operation with the use of
SFN (Single Frequency Networks) for example for SR and commercial radio operators.
Suitability for small scale operation represents support for local radio and community radio and how
suitable and effective the technology is for use in the FM band, and to a lesser extent for SFN.
Subscriber base represents available and presumptive listeners, who are predominantly found on the FM
band in Sweden, to a lesser extent on the DAB band and none yet on DRM+. The subscriber base of the
DVB-T2-Lite however is however available today as DVB-T2-Lite is a subset of the DVB-T2 standard, for
digital TV. Forthcoming TV receivers and set-top-boxes for DVB-T2 (HD TV) will be able to receive digital
TV and digital radio using DVB-T2-Lite.