Published in Silicon Valley North in 1997

Today, we are on the verge of a revolution in radio broadcasting since Digital Radio Broadcasting (DRB) is just around the corner. This new DRB service will ultimately replace the current AM and FM radio services that have filled the airwaves since the 1920's for AM and the 60's for FM. CD quality audio programming and a wealth of new data services will soon be available to mobile listeners, as well as at home, through a fully digital broadcasting system. This is poised to take place by spring 1998 when the consumer receivers start to appear on the retailers shelves.

But this did not happen out of the blue. A lot of work had to take place in terms of technology development, frequency band allocation, etc. to implement the infrastructure to make it happen. It was Gérald Chouinard, from the DRB Division of CRC, who, in November 1989, succeeded in convincing the key European research labs to make their prototype DAB equipment available to the CRC and the Canadian broadcasters for tests and demonstrations in Canada. DAB stands for Digital Audio Broadcasting and this acronym has been copyrighted by the EC Eureka-147 project under which this technology was developed (see Insert "what is DAB" on this page). Three years later, this new system had been tested and demonstrated more extensively in Canada than even in Europe. This attracted great interest from the broadcasters and the public, leading to the commitment of the Canadian broadcasters to this new technology.

CRC has also been key in providing Canadian spokesmen, in Geneva, for the establishment of the ITU-R recommendations making this DAB system an international standard. During all these years, R&D continued in the DRB Division and this resulted in close monitoring of the system development and even a proposal by CRC for a major enhancement to this European DAB system standardized through ETSI.

It was also the DRB Division at CRC who developed the mixed terrestrial/satellite broadcasting concept which would allow the reception of terrestrial local radio as well as national and international satellite radio using the same consumer receiver at home and in the cars. This had a far reaching impact, allowing Canada to convince the rest of the world, at the ITU Conference of 1992, to allocate a new frequency band for radio broadcasting from both satellite and terrestrial transmit stations at 1.5 GHz. Some 40 MHz of precious RF spectrum was set aside for digital radio broadcasting.

The rest of the world?!... not quite, unfortunately. All the countries in the world agreed with it except the US who opposed it mainly due to the US broadcasters wanting to keep a status quo with their profitable business in the FM band, therefore trying to postpone technical progress as was done in the 1950's with the advent of FM broadcasting. The DRB Division at CRC has been working hard on that front as well, being deeply involved in the testing process that took place in the US to evaluate various technologies for providing the US public with digital audio broadcasting. The Eu-147 DAB system was one of the contenders. It provided the necessary scientific and technical bases to make sure that the process was scientifically and technically sound. Furthermore, the CRC, due to its recognised expertise in tightly controlled subjective assessment of audio quality was able to attract the subjective portion of the US audio testing at CRC.

As a result of government funding ($1M) for the development of DRB in 1992, the public and private broadcasters formed the Digital Radio Research Inc. (DRRI) which lead the effort in implementing DRB in Canada since then. Also, a special Task Force on Digital Radio reporting tto the minister of Industry Canada was formed to develop the implementation strategy. This Task Force is still active.

It is also, in part, due to the work and the visibility of CRC in the US DAR discussions and on the International standards meetings that the Eureka-147 project has contracted the CBC, through Digital Radio Research Inc., to implement and maintain the 1.5 GHz DAB transmission facility in San Francisco for the conduct of the DAR systems as part of the EIA/NRSC test program to result in a proposal for an emission standard in the US. The expertise and field experience of the CBC in installing DAB transmission facilities in Canada will be critical in securing the performance of the Eureka 147 DAB system in these field tests. CRC has provided support in the field of coverage prediction for the San Francisco site for optimum transmitter location and parameters using its CRC-COV coverage prediction program.

DRB is used in Canada for the generic digital radio service. DAB is the copyrighted acronym for the Eureka-147 Digital Audio Broadcasting technology.

CRC brought the DAB prototype technology in Canada in 1990.

The technology was tested and demonstrated to the Canadian broadcasters and to the public.

CRC conducted a number of laboratory and field measurements over the years always using the latest version of the hardware. With better understanding of the potential of the technology, CRC increased its expertise, conducted parametric studies using computer simulations and confirmed the performance of the system. CRC also initiated the development of a new coverage prediction software that would take fully advantage of the features of the system (see CRC-COV box). This effort in the development of the "CRC-COV" which is now used by many organizations in a number of countries around the world.

CRC developed the concept of 'mixed terrestrial/satellite DRB' which lead to the allocation of the 1.5 GHz band worldwide except in the US (reason was protection on the current radio broadcast business, new technology would upset this well established industry, Cdn broadcasters saw this as an opportunity to strengthen their market.). The trust for the 1.5 GHz band was lead by Canada and Australia. IC representatives used the technical background developed at CRC to win their point. 40 MHz

With the support of the broadcasters, the EU-147 DAB system became an official DRB emission standard in Canada. Meanwhile IC developed an allotment plan for all Cdn broadcasters. CRTC has developed the licensing process. Everything is now in place.

CRC continued its work, especially on a new transmission mode which would allow larger transmission spacing between on-channel repeaters. We succeeded to have the EU-147 project to add this new mode IV for optimum DAB operation in Canada.

CRC has been asked to chair a group under WorldDAB dealing with satellite broadcasting of EU-147 DAB.

Cdn Broadcasters have established 4 experimental sites in Canada of which Ottawa being developed by CRC (see other story).

CRC was also heavily involved in the US to try to keep the process initiated by the EIA scientifically and technically proper. The US broadcasters tried to derail this process at a number of time to restrict the process to a IBOC solution which we at CRC had assessed to be not meeting the future market requirements of digital radio.

With the potential of DRB with its 1125 kbit/s multiplex capacity and its full flexibility to potentially split it between CD audio quality programs and data broadcasting, (see explanation of the DAB features), DAB has tremendous capability in carrying data services to mobile users, extending the information highway to mobile reception and with PCS offering a fully interactive internet type service to mobile reception.

As a result, the Canadian broadcasters are prominent in the worldwide trust towards DAB with the executive vice-president of CAB being the chair of the module dealing with marketing of DAB and the executive vice-president of the CBC having become the president of WordDAB last November. The influence of Canada has become very important worldwide to set the new generation of Radio for the next millenium and CRC was instrumental in identifying this promising technology and bringing it outside of Europe for the benefit of all Canadians. This way, Radio Broadcasting will not be relagated to the past as a antequated means of reaching people in the era of expanding information highway but will this way be an integral part of it.

There is still work to be done to hopefully bring the US on-board and to interconnect DAB with the other networks of the future such as PCS.

CRC and the Ottawa DRB Experimental Station

While experimental Digital Radio Broadcasting (DRB) stations are transmitting in four Canadian cities, the Ottawa system is being implemented with a different approach. Instead of using the traditional wide-coverage broadcasting from the highest point of surrounding land, such as Mont-Royal in Montreal and Camp Fortune covering Ottawa, CRC is experimenting with "distributed emission" in which a network of low-power transmitters (100 Watts or less) are located on the tops of existing buildings. The philosophy here is much the same as in other recently developed radio communication systems, such as cellular telephone and PCS services, except that the same frequency is being re-used by all these transmitters. The benefits of cellular deployment in radio broadcasting include improved coverage due to "transmitter diversity", and the ability to shape the coverage and to re-use the spectrum at shorter distances.

As a member of Digital Radio Research Incorporated (DRRI), CRC was given full responsibility for implementing the Ottawa experimental DRB station. The system is being developed as a testbed for exploring the distributed emission concept, verifying the accuracy of coverage prediction tools, and a host of other experiments. The system currently consists of two 100 Watt transmitters operating at 1,466.768 MHz under an operational license from Industry Canada. The main transmitter is located at Place du Portage in Hull, with a secondary one at Carleton University.

The Carleton transmitter operates as a repeater, picking up the signal directly from the main transmitter, and re-broadcasting it on the same channel. The ability to extend coverage by means of on-channel repeating is one of the characteristics which distinguishes this new digital transmission technique from traditional AM and FM analog broadcasting systems. Repeaters also pose some interesting technical challenges, so it is not surprising that designing them is an active CRC research area. At least two more repeater sites are expected to be added in the coming months, extending the coverage east and west of the National Capital Region.

In order to facilitate the experimental work and provide controlled conditions for research, a remote control and monitoring system was developed at CRC and installed at each transmitter site. The monitor stations are PC-based, with dedicated telephone lines for remote access. They provide continuous centralized monitoring of transmitter parameters and received signal levels, and also allow functions such as remote control of the output power level of the transmitters.

Consumer DRB receivers will arrive on the market by mid-1998, but many receiver manufacturers already have working prototypes. In recent months, representatives from companies such as Delco, Kenwood, Clarion and Hitachi have tested their receivers using the Ottawa DRB experimental station. It has become a popular testing ground for their future product offerings.

The Ottawa DRB experimental station will also provide an excellent platform for testing and optimizing the performance of the DRB system in carrying data services such as traffic information which are needed by car drivers. These data services tend to have different requirements (error rates, latencies, user interface, etc.) than the digital audio services and these will be investigated in a practical field situation. This work will be done by CRC in partnership with other organizations, such as International Datacasting Corp. of Ottawa.

It is expected that, once research is complete, the Ottawa experimental DRB station will be turned over by DRRI to community radio operators and will be integrated with commercial DRB services anticipated in the coming years.

DAB -- A Technical Primer

Digital Audio Broadcasting, DAB, is a technology developed under the European Economic Council project Eureka-147 mainly by two laboratories in Europe, the Centre Commun d'études en télédiffusion et télécommunications (CCETT) in Rennes, France, for channel coding and modulation and the Institut für Rundfunktechnik in Munich, Germany, for audio source coding. This technology, standardized through the European Telecommunications Standard Institute (ETSI) process, has become the ETS 300 401 standard.

This system was specifically designed to provide CD quality audio to mobile, portable and fixed receivers equipped with a simple non-directional antenna. The audio coding is based on a low bit-rate sub-band coding system enhanced by a psycho-acoustic model which takes advantage of the masking proprieties of the human auditory system to remove the redundant and irrelevant information from the audio signal and achieve a sixfold to twelvefold bit rate compression. This coding system for high-quality audio signals, known as MUSICAM, is standardized by ISO/IEC 11172-3 (MPEG 1Audio Layer II) and ISO-IEC 13818-3 (MPEG 2 Audio Layer II).

The modulation is achieved with the use of a 'discrete multitone' modulation similar to what is now used in some Asymmetric Digital Subscriber Line (ADSL) technologies. The actual modulation used in the DAB system is called Coded-Orthogonal-Frequency-Division-Multiplex (COFDM). It splits the data to be transmitted over typically 384 DQPSK narrow-band carriers modulated by symbols of 312 msec duration. This symbol duration contains a guard interval of 62 msec which gets discarded by the receiver in order to remove any intersymbol interference created by multipath. This guard interval makes the modulation so robust to multipath that it allows implementation of on-channel repeaters to fill the coverage gaps and even extend the coverage. The receivers see these repeaters as active multipath and use the total received power constructively. This actually constitutes transmit space diversity which, added to the time and frequency diversity included in the system, makes the signal extremely robust to blockage and multipath present in a city environment. The use of such on-channel repeaters is being tested to its fullest by CRC with the Ottawa experimental DRB station.

The channel coding is based on convolutional punctured coding which allows a number of different levels of Forward Error Correction (FEC) to be selected. The demodulation is performed in the receiver by a real-time Fast-Fourier-Transform (FFT) whereas the decoding is done through a Viterbi decoder.

Through its development, the Eureka-147 DAB system has expanded to become a multi-service digital broadcasting system providing capability for multiple audio programs with a wide range of sound coding rates and hence quality through its flexible, general purpose digital multiplex which can also carry a number of extra services, including audio program associated data and independent data services such as multimedia broadcast.

The transmission bandwidth is 1.536 MHz, providing a useful bit-rate capacity of approximately 1.5 Mbit/s which can carry up to 64 sub-channels of various capacity in stream mode or packet mode. Each sub-channel can independently be scrambled and is independently error corrected with overheads ranging from 25% (rate: ¾) to 300% (rate: ¼) selectable by the service provider. These sub-channels and their capacity can be changed on-the-fly by the multiplex controller. The typical multiplex arrangement for DRB in Canada is expected to carry 5 stereo pairs (192 kbit/s) each augmented with 32 kbit/s audio program associated data plus an independent 32 kbit/s data sub-channel, for a total of 1,152 kbit/s coded at rate ½.

CRC's Role in the Digital Radio Broadcasting Revolution

A revolution in radio broadcasting is just around the corner with Digital Radio Broadcasting (DRB) service scheduled to be launched next spring in Toronto. The new DRB service is expected to replace the AM service that has existed since the 1920s and FM radio services that have filled our airwaves since the 1960s. This new era will bring mobile and home listeners CD quality audio programming and a wealth of new data services. Fifteen private broadcasters and CBC's English and French AM and FM networks will transmit digitally at L-band from the CN tower and will offer service reaching all areas of metropolitan Toronto. It is expected that service rollout will occur in Montreal, Vancouver and other Canadian markets shortly thereafter. European and Japanese receiver manufacturers will introduce consumer receivers in retail stores during the same period.

Such technological marvels do not happen without achieving many technical milestones along the way. For example, frequency band allocation was required to allow DRB to happen in Canada. CRC's contribution to the DRB revolution dates back to November 1989. While participating in an international standardization meeting, Gérald Chouinard, from CRC's Radio Broadcast Technologies Research Division and a small group of Canadian colleagues, convinced key European research laboratories to make their prototype DAB equipment, developed under the Eureka-147 project, available to CRC and Canadian broadcasters for trials.

Since 1990 Canadian industry, led by CRC, has tested and demonstrated a number of prototype versions of DAB equipment in Canada. By 1994, the Eureka-147 DAB technology had been more extensively tested in Canada than anywhere else in the world. This attracted great interest from broadcasters and the public, and led Canadian broadcasters to commit to this new technology.

While CRC was a key player in the field trials and demonstrations, it also continued to develop technical expertise through laboratory R&D to fully assess, confirm the performance, and understand the future potential and even extend the capabilities of this advanced digital transmission system to ensure Canadian needs were met. CRC's contact with key players in European labs where this technology was developed permitted a direct exchange of the most up-to-date information and eventually influenced the design of the system. The R&D conducted at CRC, along with field tests done in collaboration with the CBC, resulted in a proposal for a major enhancement to the European DAB system. This enhancement allows for larger spacing between on-channel repeaters which should result in a less costly transmission infrastructure. The proposal was well received and subsequently included in the standard developed under the European Telecommunications Standards Institute (ETSI).

Close monitoring of the Eureka-147 DAB system development allowed CRC to provide Industry Canada and Canadian broadcasters with the technical and strategic advice to create a national broadcasting infrastructure for DRB.

CRC also developed a mixed terrestrial/satellite broadcasting concept which permits the reception of terrestrial local radio stations as well as national and international satellite radio broadcasting using the same consumer receiver at home and in cars. This had a far reaching impact, allowing Canada to convince ll other countries , except the USA, at the ITU World Administrative Radio Conference of 1992, to allocate 40 MHz of scarce radio frequency spectrum for radio broadcasting from both satellite and terrestrial transmit stations at L-band (1.5 GHz).

Since then, CRC has participated in the Electronic Industries Association (EIA) Digital Audio Radio (DAR) testing and standardization process which had as a goal the evaluation of proposed technologies, including the Eureka-147 DAB system, to provide digital radio to the American public. CRC's role was to contribute its technical expertise to make sure that the testing process was scientifically sound. It was also aimed at encouraging the USA to join the rest of the world in using the Eureka-147 DAB system at L-band. Adopting the same system would result in a single worldwide DRB standard with the consequent reduction of consumer receiver costs due to higher volume production and the convenience of worldwide compatibility of portable receivers.

Recognizing CRC's unique expertise, the EIA contracted CRC to conduct the portion of the EIA-DAR testing that related to subjective assessment of sound quality. Due to the sensitive nature of these tests, triple-blind testing methodologies had to be developed where even CRC staff involved in these tests did not know which system was actually tested.

CRC also helped design the Eureka-147 DAB transmit facility in San Francisco as part of the EIA-DAR field trials. Overall, this EIA-DAR testing process confirmed the previous CRC findings that the Eureka-147 DAB technology is superior, especially for mobile reception in a harsh multipath environment. Despite this evidence, US broadcasters are still trying to develop AM and FM in-band digital solutions to protect their current market.

To assist implementing DRB in Canada, the federal government initially provided $1M in 1992 that was matched by industry. This spurred the formation of Digital Radio Research Inc. (DRRI) by public and private broadcasters. DRRI subsequently led the effort in implementing DRB in Canada by establishing four experimental sites in Toronto, Montreal, Vancouver and Ottawa. CRC became an active member of this not-for-profit organization and took custody of the Ottawa DRB site. As well, CRC participates in the special Task Force on Digital Radio reporting to the Minister of Industry Canada which was formed to develop a DRB implementation strategy.

Industry Canada has confirmed the Eureka-147 DAB system as the Canadian emission standard for digital radio and the department has developed an allotment plan accommodating all current AM and FM broadcasters in this new 40 MHz band at 1.5 GHz. The CRTC established a licensing process which will issue its first operational licence for the CN Tower DRB installation in Toronto.

As we enter the next millennium, Canada's vigorous promotion of digital radio, nationally as well as internationally, will permit new broadcasting services to become an integral part of the future information highway. By extending DRB to the general public and in particular to mobile users, radio broadcasting as a medium, is being reborn.

CRC's early identification of the promising technology and its initiative in developing the technical expertise in view of its implementation in Canada was important to the radio industry. CRC continues its efforts to bring the US on board, and is working to refine technical tools to facilitate DRB implementation. It also wants to assist Canadian manufacturers who have opted to develop DRB equipment. There is also a huge market for non-broadcast services stemming from DRB. With DRB's potential for delivering data services to mobile users and, with PCS providing a lower capacity upstream path, a fully interactive internet type service to mobile users can potentially be provided. For more information on CRC activities in this field, visit our web.