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Introduction

While listening to FM radio in your car or on your portable FM receiver, you have probably noticed that the FM station’s frequency is not the only information displayed on your monitor. In fact, nowadays, most FM stations transmit additional data that provide a variety of features that are of great use to radio listeners. Information such as the FM station’s name, call sign (i.e., CBFX-FM), song title, name of artist, and even the local traffic and weather information can now be transmitted and displayed on a compatible receiver.

The Radio Broadcast Data System (RBDS) is the technical standard that allows FM transmitters to broadcast additional types of information through encoded digital signals that can be displayed on RBDS-compatible FM radio receivers. Currently, the majority of car manufacturers offer RBDS-compatible FM receivers and/or navigation systems in their automobiles. Moreover, high-end audio entertainment systems and portable FM receivers, such as the iPod Nano, now have built-in RBDS functionality.

The purpose of this article is to briefly explain RBDS technology and the features currently in use at CBC/Radio-Canada. As you will see, RBDS technology can be used to enhance the FM radio listening experience by interacting with listeners while offering interesting third-party partnership opportunities, and, best of all, RBDS can be used to keep listeners tuned in!

RBDS Basics

RBDS data are modulated and carried inaudibly as a 57 kHz subcarrier on the FM baseband stereo signal. Figure 1 shows the baseband audio portion of an FM stereo signal, including the RBDS subcarrier.

Figure 1 – Baseband audio signal with RDBS sub-carrier

Low injection levels (3% to 5%) allow the RBDS data to be efficiently transmitted on FM airwaves without affecting the performance of the main audio signal. The RBDS data are continuously transmitted in a cyclical fashion, resulting in a very robust data stream optimised for mobile reception. RBDS data transmission is possible with the use of cost-effective software and encoders. Consequently, RBDS implementation costs are relatively low for FM broadcasters wanting to implement this technology.

RBDS Features

In its most basic form, RBDS technology allows FM stations to display the station’s name or call sign on the receiver. This is done using the Program Service Name feature (PS Name). PS Name is limited to eight characters and it is usually displayed on the RBDS receiver instead of the station’s frequency. At the CBC/Radio-Canada, PS Name convention for our four FM networks is usually:

• RadioOne for Radio One
• Premiere for Première Chaîne
• Espace M for Espace Musique
• RadioTwo for CBC Radio Two

Recent developments in RBDS technology allow FM stations to make use of a variety of additional features, such as the ability for a receiver to automatically switch from transmitter to transmitter, display scrolling text information, tag songs for future Internet download, and create partnerships with third-party applications, just to name a few. The following sections will explain some of these RBDS features currently in use at CBC/Radio-Canada.

Radiotext & Radiotext Plus

The Radiotext feature (RT) is used to display dynamic data information or scrolling text on the radio receiver. This feature is limited to 64 characters and can scroll through a variety of information such as the song name, artist name, or the name of a specific show. Additional information, such as the weather forecast, traffic info, local promotional events, and advertisements can also be transmitted and displayed with this feature. Radiotext Plus (RT+), on the other hand, is an additional data stream that allows receivers to control and sort information on separate areas of the receiver. This makes the FM radio listening experience much more appealing, since the information has an MP3 player or Satellite Radio receiver look and feel.

Figure 2(a) – iPod Nano with RT+ feature
on Espace Musique in Montreal

Figure 2(b) – iPod Nano,
list of tagged songs

The RT+ feature also allows listeners to tag songs while using compatible devices. Figure 2(a) shows an example of an iPod Nano media player that also includes an RBDS-compatible FM receiver. The song’s title and artist name are displayed and can be “tagged” by using the icon on the bottom left of the screen. The song title and artist name will be saved so that, the next time listeners connect their device to the Internet, the tagged songs will be accessible and available for purchase online. See figure 2(b) for an example of a list of tagged songs.

Figure 3 – Samsung Android (left) and Blackberry
Curve (right) with RT+ data, courtesy of the CRC.

Radio stations can also use the RT+ feature to connect with their audience like never before. For example, figure 3 shows two snapshots of Communications Research Centre Canada’s (CRC) FM TwoO application^[i] for the Samsung Android and Blackberry Curve smart phones. These smart phones also have RBDS-compatible FM receivers. Listeners would have the ability to connect to the stations' websites or use the speed dial function of their device to place calls and/or send emails. Additional applications such as photos, album covers and a variety of advertisements could also be displayed. User-selected information of this sort can provide additional opportunities for FM stations in terms of how they meet the requirements of their listeners.

Alternate Frequency (AF Feature)

If you listen to FM stations while travelling over long distances, you will need to retune your car radio from time to time when the signal begins to fade out. This is because FM signals cover a radius of up to 80 km from the transmitter site, depending on your station’s operating parameters and terrain. Therefore, a network of FM transmitters is required to provide coverage for a particular programming over great distances. While neighbouring transmitters need to use alternate FM frequencies to avoid interference, the Alternate Frequency (AF) feature will allow your receiver to switch automatically to a better signal of the same programming so you will not need to retune manually. The switch in frequency is seamless to the listener and it is a great feature to keep listeners tuned into CBC/Radio-Canada while driving long distances. Since the RBDS receiver will look for pre-programmed frequencies and the programmed identification code specified by the network that is currently tuned in, competitor stations could not switch a receiver to their frequency. It is also important to point out that some receivers need to have their AF feature activated, as this is an optional feature on many RBDS-compatible receivers. This has been the case with GM vehicles that we tested where “AF ON” needed to be enabled.

The following section will discuss specific examples using FM coverage maps where the AF feature is (or will be) very useful to expand coverage and keep listeners tuned in.

Figure 4 – Alternate Frequency coverage, CBC/Radio-Canada
Espace Musique: Montreal, Trois-Rivières, Quebec City, and Sherbrooke

Figure 4 shows a coverage map of four CBC/Radio-Canada FM transmitters broadcasting the same programming. In this case, the programming is Espace Musique and RBDS encoders are currently installed on each of these four transmitters. As a result, an RBDS-compatible FM receiver tuned to any of these four frequencies can be automatically switched to the stronger signal’s frequency while travelling from one service contour to the other. Our field-testing proved that, when the audio delays are configured properly between transmitters, the switch in frequency is seamless to the listener. We actually needed to observe the display on a separate FM receiver in order to see exactly where and when the switch in frequency occurred while driving east on Highway 10 from Montreal towards Sherbrooke and while driving east on Highway 40 from Montreal towards Trois-Rivières.

Figure 5 – Alternate Frequency coverage, CBC/Radio-Canada
Première Chaîne, FM Transmitter repeaters in Gaspésie, QC

Figure 5 shows a coverage map of southern Gaspésie, Québec, where we are currently building a repeater network of five FM transmitters. These five transmitters will all broadcast the Première Chaîne network programming and will be ready to begin operation in September 2012. All five of these transmitters will be equipped with an RBDS encoder and have the AF feature programmed. As a result, a vehicle with an RBDS-compatible receiver tuned to 104.3 MHz in New Richmond, and travelling east on Route 132, will be automatically tuned to the best available Première Chaîne FM signal all the way to Percé, QC. This represents a distance of over 250 km. Additional testing will be done this fall to determine the ideal injection levels and RBDS AF encoder setup in this very mountainous terrain. Additional RBDS encoders could also be installed to further expand coverage in the Gaspésie peninsula, where CBC/Radio-Canada has a series of FM repeater transmitters.

Figure 6 – Alternate Frequency coverage, CBC/Radio-Canada Radio
One from Windsor to Ottawa along Highway 401

Another example of where a network of FM transmitters could be linked together to form an expanded coverage zone is shown on figure 6. Here, the FM transmitters all broadcast Radio One programming and they cover Highway 401 from Windsor to Cornwall and the Ottawa region. This would be a more challenging RBDS encoder setup scheme, since Radio One programming is not the same for all Radio One transmitters during some periods of the day because of regional and local content. However, the RBDS standard allows the broadcaster to control the program identification codes and AF configuration of individual transmitters in a specific network during different program periods to prevent undesired automatic switching to occuring. At the time of this article, this feature and configuration have not yet been tested, at CBC/Radio-Canada.

Open Data Application (ODA Feature)

Soon, electricity usage and billing will be subject to “time-of-use” rates, where the price of electricity varies according to when it is used during the day. Electricity usage during peak hours will cost more to the consumer. Canadian electrical utilities are now deploying “smart meters” that will allow them to bill usage based on “time-of-use”. In response to this “time-of-use” rate, manufacturers such as GE^[ii] are coming up with “Smart Appliances” such as hot water heaters, washers, dryers, AC units, etc., that are designed to operate outside peak demand periods.

What does this have to do with RBDS and FM transmitters? RBDS encoders that use the ODA feature can be used to encode and transmit electrical utilities’ peak-demand data to smart appliances. You might well ask yourself what this has to do with CBC/Radio-Canada. The answer is that, in January 2010, CBC/Radio-Canada and e-Radio Inc. teamed up^[iii] to provide electrical utility data to smart appliances through the use of FM airwaves and the ODA Feature.

Other interesting RBDS features not currently in use at CBC/Radio-Canada are Traffic Program (TP), Traffic Announcement (TA), and Program Type Name (PTYN), just to name a few.

RBDS System Design & Implementation

At the time this article was written, CBC/Radio-Canada’s RBDS data were broadcast on all 39 Espace Musique FM transmitters, on 10 Radio Two FM transmitters, and on a handful of Radio One and Première Chaîne FM transmitters throughout the country. Design considerations and implementation were challenging due to the following facts:

• CBC/Radio-Canada’s regional radio content and audio program feeds are sent to Montreal for the French Networks and to Toronto for the English Networks.

• Then, all program feeds are uplinked and distributed over satellite out of Montreal and Toronto. These program feeds are made available with the use of a 4.5 m satellite antenna at the majority of our transmitter sites. Only a handful of FM transmitters are linked to a regional production centre via a Studio to Transmitter Link (STL).

• The design required a system that can be scalable for more than 600 FM transmitters (607 FM transmitters to be exact^[iv]) in the event RBDS would be deployed nation-wide on all Radio One, Première Chaîne, and Radio Two FM transmitters.

• The source RBDS dynamic data are an IP-based, whereas the majority of CBC/Radio-Canada’s transmitter sites do not have an IP or LAN connection, as most of our broadcast towers and FM transmitters are in remote locations and in difficult, mountainous terrain.

Figure 7 – CBC/Radio-Canada’s RBDS system design

Let’s start by looking at the RBDS source data provided by Media Presentation servers in Toronto and Montreal. The dynamic Radiotext information that eventually makes it to the RBDS encoders is centralised in Montreal for the French radio networks and in Toronto for the English radio networks. The song's information (artist and title) or the name of the on-air show is included in a playlist generated by a third-party software called Sonart. When a new song is played, Sonart will provide the song's information by modifying an XML file located on the RBDS server. As soon as the file is modified, the Center Stage Live^[v] software reacts to the modification and immediately captures the “now playing data”. The song's information will then be streamed in TCP/IP & multicast format, which makes it readily available for the rest of the distribution chain. A similar setup is used for the English radio networks in Toronto.

Since all of CBC/Radio-Canada audio feeds are centralised and uplinked out of Montreal and Toronto, the system was designed to consider the various time zones, networks, and playlist data associated with the on-air audio. E.g., our Espace Musique network of transmitters is composed of 39 transmitters fed by 14 distinct audio feeds. In order to be bandwidth-efficient with our satellite distribution channel, the source data are converted to multicast TCP/IP data. Therefore, 14 individual data streams are uplinked in lieu of one data stream per transmitter.

Consequently, we needed to have this TCP/IP multicast data in a format compatible with our existing Cisco ASI encoding and multiplex platform. This is achieved with an IP encapsulator that converts the TCP/IP multicast data into ASI format. At this point, the ASI data are multiplexed in our encoding platform and then modulated, upconverted, and uplinked with High Power Amplifiers (HPA) and high-gain satellite antennas.

The last portion of the design challenge was at the transmitter sites. First of all, the RBDS data are made available at the IP output of D9850 satellite receivers. However, IP data at a transmitter site posed a challenge in and of itself, as the majority of CBC/Radio-Canada’s transmitter sites do not have LAN connections, and we needed to design a new IT-approved TCP/IP infrastructure for all of our transmitter sites in order to properly decode the multicast data streams and allow TCP/IP compatibility with other broadcast equipment at our sites. Various documented standards and training sessions were required for our RF technologists and engineers in order to implement RBDS at our FM transmitter sites. As a result of that process, the RBDS encoder encodes and modulates the 57 kHz RBDS subcarrier, and sends it to the exciter input on the FM transmitter. Finally, proper RBDS injection levels and total RF modulation levels with the FM transmitters are carefully adjusted in order to not over-modulate the FM carrier.

Conclusion

RBDS technology and its features offer broadcasters a great opportunity to interact with listeners by providing important information about the content and programs that are offered. The Program Service Name feature is a cost-effective way to promote the station or network’s name, as it is displayed directly on the radio receiver, in front of the listener.

By using other RBDS features such as Radiotext Plus and Alternate Frequency to their fullest, broadcasters can attract new listeners, retain loyal listeners, and keep everyone tuned in! Most importantly, all of this can be achieved with a minimal investment in a proven technology that will be available for the foreseeable future.

Thanks to lower-priced chipsets and the fact that the majority of FM stations now offer RBDS data to their listeners, RBDS-compatible FM receivers are now standard in the majority of new automobiles sold in Canada. Furthermore, there are a growing number of RBDS-compatible functionalities available in popular portable audio devices such as the iPod Nano.

Finally, RBDS technology can be seen as a technology boost for traditional FM broadcasters such as CBC/Radio-Canada. As new FM stations are using the remaining available spectrum in most major Canadian cities, RBDS technology should be strategically implemented in order to remain competitive with other FM stations and with the wide array of other content and media services offered today.

Acknowledgements

Implementing RBDS at CBC/Radio-Canada was a team effort and many resources from the following components have contributed to its successful implementation: CBC Transmission Operations from coast to coast, Transmission Engineering, New Broadcast Technologies, Broadcast Engineering and Operations Montreal, Broadcast Engineering and Operations Toronto and CBC Telecommunications. Special thanks must go to Charles Rousseau, P.Eng, Senior Spectrum Engineer and lead project engineer, for his contribution to RBDS testing, implementation, and contributions to this article, as well as Isabelle Houle, Draftsperson – Transmission Engineering, for providing wonderful coverage maps and drawings.

References

• Understanding and Deploying Radiotext Plus (RT+), Alan W. Jurison, Clear Channel Media + Entertainment, Cincinnati, Ohio (2012 NAB proceedings)
• Radiotext Plus (RT+) Specification, version 2.0. RDS Forum (2005)
• The Broadcaster’s guide to RDS, Scott Wright (1997), Focal Press
• Radio World – RDS: What You Need to Know: http://www.rwonline.com/article/rds-what-you-need-to-know/2947
• Radio Broadcast Data Systems, (2010 - NAB Engineering Handbook). Scott A. Wright, Delphi Delco Electronics Systems, Kokomo In
• NRSC-4-B, United States RBDS Standard, Specification of the radio broadcast data system (2011)
• RBDS versus RDS – What are the differences and how can receivers cope with both systems? Scott Wright (Delco Electronics Corp., 1998)