The industry first heard about ZoneCasting at the 2012
NAB Show. Radio World has been covering the developing story since, and a lot
has happened over the past 11 months.
Fig. 1: WRMF’s
signal measurement is seen in yellow, with green showing what has been
predicted before signal correction.
(Click to Enlarge)
Most engineers are
familiar with on-channel FM boosters and repeaters using Harris SynchroCast and
other systems. ZoneCasting has evolved from that technology but is also able to
geo-target areas inside a station’s coverage area with replacement commercial
and other programming content.
recently unveiled cousin, “MaxxCasting,” does not broadcast different
content to the geo-targeted areas, but uses many of the same innovations and
invented ZoneCasting and has worked with Harris Broadcast to fine-tune optimal
implementation of this technology. The expertise of NPR Labs has also been
enlisted to assist in this effort.
We recently talked with the key players from GBS,
Harris Broadcast and NPR Labs who are working to bring this innovation to
market. Their plan includes more real-world testing and eventual FCC
GeoBroadcast Chief Executive Officer Peter Handy
and Chief Technology Officer Bill Hieatt answered our questions about their
latest developments. Also participating in our email interview were Aaron
Shainis of Shainis and Peltzman, legal counsel to GBS; John Kean, senior
technologist of NPR Labs; and Rich Redmond, vice president of strategy and
product management for transmission systems at Harris Broadcast.
Radio World Engineering Extra: The promise of
ZoneCasting will deliver targeted over-the-air ads or messages with different
content into segmented zones within the overall coverage area of a given radio
station. Explain the advantages of this technique and what it potentially means
for the overall radio industry.
Peter Handy, GBS: The advantages that the ZoneCasting
technology will deliver to FM radio stations are, but are not limited to, the
following: Commercial content will be more relevant to the listener. FM radio
stations will have more inventory to sell while delivering the same amount of
non-commercial content. Local retailers and advertisers will have the
opportunity to be more efficient with their ad spend. FM station owners will
have more potential advertisers by as much as two times their current customer
The potential for the overall radio industry is
exceptional. Stations that implement the ZoneCasting system could grow their
top line revenue by 20 percent or more per year. Listeners may be more inclined
to listen through a commercial if it is more local (relatable) in nature. FM stations may
reverse the oversupply curve by creating more demand due to the increased
number of customers and local advertisers may see an increase in the results
produced by their radio ad schedules.
Following the collection of field data, propagation parameters including
diffraction factor, clutter heights and clutter absorptions are collected. This
makes the measured vs. predicted correction a much more accurate model when
matching the field data, and provides a highly accurate model for use in booster
design and placement.
(Click to Enlarge)
RWEE: The industry
first heard about ZoneCasting at NAB 2012. Tell us in a nutshell how it works.
Rich Redmond, Harris: The successful use of synchronous on-channel boosters
requires a combination of advanced technology for transmission of a signal and
careful network design to ensure the desired area of coverage is achieved while
at the same time mitigating any undesired interference to the primary station
or others. The ZoneCasting family of solutions takes this technology to the
next level to allow for the delivery of different localized content to specific
geographic areas using a network of on channel boosters.
we were to compare this to a lighting example, you might think of how you would
light up a stadium for a night game — you ring the field with focused
high-intensity lights focused on the field. All the energy is direct to the
playing field; you are not trying to light up the parking lot. A traditional
broadcast approach to lighting would be to put a high power omnidirectional
light high above the field, as you end up lighting up the field plus everywhere
John Kean, NPR Labs: The system’s potential success depends most on a thorough
understanding of synchronized repeater operation and its capabilities: Its
operation relies on sound physical principles that are better optimized than
previous on-channel designs.
RWEE: Engineers who
have worked with boosters and repeaters know that terrain shielding is needed
to make single-frequency networks work well. While ZoneCasting does not depend
on terrain shielding, the areas where signal strengths of the on-channel
transmitters are about equal will create interference or “mush zones.”ZoneCasting has developed some new and unique methods to
reduce mush zone interference. One apparently involves reducing or muting the
booster transmitter’s power during common programming periods. Please tell us a
little about this.
Redmond: Boosters within the ZoneCasting network
operate in a combination of full-time and part-time modes. Boosters that are
full-time operation serve to both maximize coverage of the primary signal and
support the localization of content. These full-time boosters carry the same
content as the primary station most of the time, and then switch programming to
the local content during segments of localization.
Other boosters only
operate during the times of local content insertion to cover a certain area
with the local content, and then turn off once that content is completed. This
operation is interfaced with the station’s digital audio system and controlled
by the GBS ZoneCaster issuing commands over the Harris Intraplex SynchroCast
system, and is time-aligned along with the audio content typically over an IP
RWEE: What role do NPR Labs and John Kean play in this partnership?
Kean: NPR Labs has several
roles with GeoBroadcast Solutions. The first is to determine the optimal
parameters for ZoneCasting and MaxxCasting network design, including coverage
design parameters for the network nodes. NPR Labs has extensive experience with
signal propagation models, mapping and field verification, and is providing
technical information on its own geographic mapping tools for designing a
multimode network in all types of terrain.
An equally-important consideration is compatibility of
the network with the primary transmitter signal, which shares within the
station’s authorized service contour. The NPR Labs team has conducted
carefully-designed listener tests to determine the threshold time-of-arrival
and signal ratio parameters for the “mush zone” resulting from synchronous
transmitter operation. The testing covered mobile and fixed FM reception, and
included combinations of primary-to-node and node-to-node signal propagation.
Fig. 3: This is
a basic overview of the signal path for WRMF’s ZoneCasting configuration, with
all corresponding components. The same architecture applies to other potential
(Click to Enlarge)
role for NPR Labs is to integrate the performance and compatibility data into
computerized models to optimize system designs. We use the ESRI ArcMap system
for its versatility in building geo-mathematical models and its wide range of
GIS data for mapping and demographic analysis. For each minute grid-point on
the study map, our terrain-sensitive model considers the arrival of signals
from multiple nodes as well as the primary transmitter to compute the reception
quality. This system allows us to reliably predict where “mush zones” will
occur and adjust the design for the best integration with the primary station’s
signal, population served, etc.
NPR Labs has developed
a calibrated FM signal measurement system for mobile field verification of
signal coverage. Our fourth role will be to collect performance data and
received audio from working systems and analyze it for system improvements.
[See Figs. 1 and 2.] We may also conduct listener testing experiments to
provide scientific verification of operating systems.
adapts the cellular telephone model of using low-power repeater transmitters
that cover defined limited coverage areas. What power levels and antenna
heights will be suitable for a typical large market that may want to deploy
Kean: The techniques
developed for cellular telephone network site selection serve ZoneCasting and
MaxxCasting networks, as well. Using moderate antenna height and power, many
commercial rooftops and tower sites used in cellular industry are candidates
for the nodes. Because of the number of nodes required, and because site
selection requires interaction with the RF designer, “site acquisition” is
handled by GBS’ real estate specialists as part of a turnkey implementation.
This ensures that the optimal sites are selected efficiently and
ZoneCasting and MaxxCasting network design varies with
each station, depending on its environment and the station’s objectives for
service. While the power, antenna height and site density can vary widely there
are some general parameters for design. For example, network nodes should be easy
to site, using existing commercial buildings and towers. Radiated power should
be low enough to avoid restrictions for human exposure to RF, which, with
moderate elevations tends to limit ERPs from 500 to 5000 watts.
Using highly directive antennas, GBS is able to use
sites with only standard mains power and minimal equipment space. Antenna
heights are typically only 25 to 40 meters above ground, to control the
coverage of each node and avoid spilling signal across distant nodes or into
areas to be served by the primary transmitter. GBS is developing an antenna
with much higher front-to-back ratio than currently-available models as a tool
for efficient designs.
Fig. 4: This
graphic shows the FCC-defined service contour for WRMF. It is a graphical
representation of where the ZoneCasting tests will happen in southern Florida.
(Click to Enlarge)
may range from one to five kilometers, depending on terrain and building
density. Although the area of a network “zone” is almost unlimited, a typical
zone serving a community may require from five to 20 nodes.
RWEE: How will
ZoneCasting networked transmitters be linked together and fed with both common
and different programming?
Redmond: The Harris SynchroCast system used in the ZoneCasting
solution has the flexibility to work over a variety of networks. In North
America T1 circuits (similar to E1 circuits in the rest of the world) have been
the most popular for building single-frequency FM network connectivity.
Recently Harris has introduced SynchroCast3 to support the use of IP networks.
All of these network types can be used over wired or wireless networks to allow
for the maximum flexibility in system design.
RWEE: How will the
different program content intended for specific zones be inserted and conveyed
to their respective transmitters?
Redmond: The content for both full-time and part-time boosters will
originate at the studio and be distributed over the SynchroCast network.
Content targeted for full-time boosters in an area of localization will switch
from a simulcast of the main transmitter to locally targeted content. The
part-time boosters will only be sent content during the periods of local
content insertion. [See Fig. 3.]
Fig. 5: This map
shows a sample of a drive test to show data of the measured RF signal. This
represents the southern portion of the market where the initial tests will
(Click to Enlarge)
The control of timing
is a critical factor in any SFN network of boosters. Over time many have
attempted to use a variety of fixed delays to adjust the network for proper
time alignment, only to find that changes in the link, either wired over a
public network, or wireless over a microwave, vary in actual operation, turning
the once aligned network into a series of transmitters causing interference.
Only the Harris SynchroCast system supports real-time
adaptive delay to ensure the critical SFN calibration is not affected by
changes in performance of the network. Transmitters and the studio location are
all referenced to GPS. This reference both time-stamps the audio and control
signals carried on the SynchroCast system, as well as the frequency of the
transmitters, pilot and pilot phase of the integrated stereo generator. By
using the GPS reference, we can be certain that all the transmitters operate on
the exact same frequency along with the stereo generator located at each
transmitter site, a critical first step for a successful booster.
The second use of the GPS reference is to power the
real-time adaptive delay. The important part of delay control is to align the
time the audio arrives at a listener’s receiver in an area of overlap between
transmitters with the same content. The delay of each transmitter is different
based on location, terrain, building density and total time it takes the audio
to travel from the studio to the farthest transmitter site. Proprietary
software is used to calculate the exact delay required for each transmitter in
the network to optimize overage. Once installed, the system is adjusted based
on field measurements to dial in system performance.
RWEE: A ZoneCasting
announcement last spring indicated that system testing had been conducted in
Utah and that additional testing would be done during the summer in Sebring,
Fla.Tell us more about the results of
Bill Hieatt, GBS: The two tests
conducted represented two different ends of the variety of conditions that we
anticipate for ZoneCasting implementations.
Our initial tests in
the Salt Lake City region consisted of four zones, each covered by an
autonomous booster. This FM broadcast region had already been in place for a
reasonably long time and interference between the zones had been minimized
through the use of terrain shielding as well as Intraplex SynchroCast
synchronization. We found that it was not necessary to modify any RF broadcast
parameters, at any booster site, to implement and test the ZoneCasting concept.
Conversely, the system
in Sebring, Fla., was built from the ground up as no boosters or zones
initially existed. And because terrain shielding was not available, it was
obviously more difficult in terms of engineering and implementation. It became
invaluable with respect to developing our simulation models and understanding
what we needed going forward in such an environment.
In both tests, we initiated the engineering
design based on published standards for synchronized audio in SFNs such as
those from the ITU, but in Sebring, we found we needed to make our own
modifications. The design includes typical RF engineering parameters such as
radiated power, antenna array azimuths, downtilt and simulcast differential
time delays. By using considerable field data measurements we optimized the
mathematical modeling of our computer simulations. We were then able to
“predict and move” our transition areas (from the main coverage to the
ZoneCasting zone) to areas with little population or automobile traffic.
Once we were comfortable with our modeling of the
ZoneCasting System, we were subsequently able to experiment with different
techniques such as switching to monophonic transmission during a ZoneCasting
During the tests we
found it important to use an FCC-approved calibrated receiver with a calibrated
antenna and GPS receiver to log the audio samples. The transition area that
exists between the ZoneCasting region and the main broadcast transmission area
appears as multipath noise to the FM receiver. Most car audio manufacturers
will compensate for channel conditions such as multipath fading by reducing
stereo separation and/or changing the audio processing, and it was important
not to be biased by any particular FM car receiver. This subsequently prompted
us to fund truly pioneering additional research that has been conducted by NPR
The most difficult challenge that we faced in terms of
implementation was the distribution of the localized audio content to the
ZoneCasting boosters. Because we send linear uncompressed audio to each
booster, QOS issues such as delay and jitter are crucial, and very close
cooperation with the WiMAX service providers was required. Although versed in
Quality of Service requirements due to their other user’s applications, such as
VoIP and gaming, careful examination of the audio distribution should be done.
Depending on the area, a permanent installation may be better suited using
licensed RF or copper/fiber connectivity.
Fig. 6: This map
highlights the total coverage area of the ZoneCasting trials for WRMF, covering
the Miami, Fort Lauderdale and West Palm Beach areas.
(Click to Enlarge)
RWEE: Your recent press
release identifies WRMF(FM), Palm Beach Broadcasters in West Palm Beach as the
next station that will install ZoneCasting for more extensive testing early in
2013. Can you share the details of that effort and partnership?
Handy: The proposed
partnership with Palm Beach Broadcasters in West Palm Beach is currently in the
design phase for a network for WRMF(FM). The system we are designing is
somewhat complicated, as the zone we are looking to cover is relatively large.
WRMF may be one of the best stations in the state of Florida and it certainly
has one of the best signals. The design we are working on has been modified
several times, and we believe the latest schematic will accomplish the needs of
our client. If we are correct, we would hope to begin the build out of this
network within the next six weeks. [See Figs. 4, 5 and 6.]
many zones will be needed and at what power levels to achieve the WRMF coverage
Handy:Our first buildout for WRMF will be one
zone, which covers a portion of Broward County. Ultimately, WRMF will have
ZoneCasting coverage of all of Broward County. However, this in all likelihood
will be a two-step process. The first zone will have approximately 30
transmitter sites with each transmitter site broadcasting at power levels of
less than 1,000 watts. The multi-site low power design creates minimal
interference while at the same time delivering signal coverage that not only
covers the listening area, but does so with a cleaner signal than what the listener
currently gets from the main transmission site. In other words, the station
will now have the ability to run geo-targeted content, delivering more
relatable content and will be doing so with better audio quality.
deployment will require special FCC approval, rules modification and licensing.
What is the status of the petition with the FCC to allow booster stations to
transmit programming that is different from the main channel?
Aaron Shainis, GBS: Shainis & Peltzman, Chartered is the principle
regulator counsel to GeoBroadcast Solutions. At present time, ZoneCasting has
requested pursuant to a rulemaking filed with the FCC to make a minor
modification to the FCC’s rules to allow origination of programming on booster
stations. That rule making has been pending for about six months, which is not
It is anticipated that a Notice of Rule Making will be
issued sometime during the first half of 2013. That notice will seek comment
from the public on the proposal, but it is generally thought that the matters
contained in the petition are not controversial, so adverse comments are
unlikely. The preliminary comments files shortly after the request for
rulemaking was filed were supportive.
With respect to the
experimental authorizations for the WRMF tests, the engineering for the
applications for the boosters are currently being finalized. The applications
for permanent booster facilities will be filed and those are generally granted
within two months. Once they have been granted, built and licensed, the
commission will entertain the request for experimental authorization. Our
experience in obtaining other experimental authorizations relative to
ZoneCasting is they generally are granted within a matter of weeks after
filing. I believe that WRMF will be treated no differently.
interested in ZoneCasting are all wondering what the ball-park costs of adding
this enhancement to their markets might be, on a per installed booster site
Redmond: There are three major areas of costs associated with the
The first is the licensing and network design
costs. Part of the key to the success of ZoneCasting is the use of special
planning tools to create a targeted zone of transmitters to cover a certain
area while at the same time minimizing any impact to other zones or the main
signal. These costs are variable depending on the number of zones a station
wants to target, and the number of sites needed to cover the zone. These costs
are part of an upfront licensing fee that will vary by market size. In addition
there is a small revenue share associated with the use of the GBS patented
technology, which is similar to an agency commission for the incremental
revenue the systems generates.
The second portion of costs is related to the
distribution of audio to the various sites, and the actual transmitters and
antennas needed. While these too vary based on the power needed at each site, a
basic site of equipment is about $39–55K plus installation. There would also be
some equipment needed for the studio location, and is similar in cost to that
of the transmitter site.
The third area of cost
is the ongoing tower rental, data circuit charges and electricity needed to run
the sites. The costs here are related to the number of sites and the part of
the country you operate in, but as these are low tower sites they are typically
in the hundreds of dollars per month range.
Tom McGinley is a
longtime radio broadcast engineer and technical adviser to Radio World.
on this or any other story to firstname.lastname@example.org.