DIGITAL RADIO BROADCASTING (DRB)
WHERE ARE WE UP TO?
by David Soothill
Director Communications & Planning, SBS
2 VARIOUS DRB SYSTEMS
2.1 Eureka 147
3 AUSTRALIAN RESEARCH RESULTS AND STUDIES
3.1 Eureka 147 Satellite Tests
3.2 Satellite Coverage Objectives
3.3 Canberra Coverage Tests
3.4 ABA DRB Task Force
4 THE DRAC REPORT RECOMMENDATIONS
5 WORLDWIDE DEVELOPMENT OF EUREKA 147
6 DRB PLANNING AND DIRECTIONS
6.1 Service Planning for Digital
6.2 DRB Directions for Australia
DRB (or DAB) is the future of radio broadcasting. Even now, the Eureka 147 DRB technology is reportedly providing broadcasts to over 100 million people worldwide, including pilot services. This paper provides a general update commencing with an outline of the various systems now under development. It then covers the practical research and investigative work done in Australia, the outcomes from the Government's Digital Radio Advisory Committee (DRAC), some of the service planning issues for DRB and finally some issues and directions.
Throughout this paper the main focus is on the system recommended for adoption in Australia - Eureka 147 operating in the L-Band spectrum, 1452-1492 MHz.
2. VARIOUS DRB SYSTEMS
Several DRB systems are under development, most of which are intended to meet specific market needs. The Eureka 147 system offers a universal solution while all other systems are directed towards particular market needs. The extent to which all or any of these systems will be commercially successful and adopted on a world wide basis remains uncertain. In outlining the features of each technology, the emphasis will be on Eureka 147 and WorldSpace as these two systems are the most technically mature and are in the process of being implemented. Several other systems will be touched on briefly, mainly for the sake of completeness.
2.1 Eureka 147
At this time Eureka 147 is the only viable technology for terrestrial delivery of DRB. It is also designed for satellite delivery and is fully compatible for both satellite and terrestrial reception on the one receiver. It is the most mature system, having been under intensive development for some 10 years now. Although having its design concepts based in the delivery of distortion-free, CD quality radio to fixed, portable and mobile receivers, it has now been developed to the point where it will support an extensive range of additional data services, and is being standardised to provide a strong platform for multimedia delivery.
The Eureka 147 system uses a totally different approach to radio broadcasting from AM and FM. AM and FM use a single transmission frequency to deliver a single mono or stereo program. Eureka 147 technology combines several radio programs (and any data) into a single multiplexed data stream known as an 'ensemble' and delivers this to an advanced digital receiver which can do much more than simply provide audio to the listener.
This single multiplexed ensemble delivers a useful bit-rate stream to the receiver of about 1.0 to 1.5 Mbps. This data stream can be dynamically configured in a wide variety of ways with the basic audio configuration often being seen as five CD quality stereo audio channels of 256 kbps each. However, many other combinations are possible with other examples including 10 services of 128 kbps, or perhaps a mixture of 14 services comprising:
2 x 192 kbps, 2 x 128 kbps, 10 x 64 kbps.
Eureka 147 has been standardised as a European Telecommunications Standard (ETS 300401). The audio coding is in accordance with MPEG1 Audio Layer II and MPEG2 Audio Layer II.
In multiplexing several services into a single ensemble, the Eureka 147 system uses an advanced digital transmission technology known as COFDM (Coded Orthogonal Frequency Division Multiplexing). This system spreads the transmitted signal over a spectrum of about 1.5 MHz to provide a high level of immunity from multipath degradation, interference and selective fading. These are the three most common effects that severely degrade AM and FM radio reception. Eureka 147 can operate in any frequency band above 30 MHz, but the commonest bands are likely to be a VHF band around 230 - 240 MHz and the DRB L-Band spectrum of 1452-1492 MHz. Australia plans to use the L-Band spectrum.
The Eureka system is a well designed, fully integrated technology which offers listeners interference-free reception of high quality sound, easy to use radios and a wide range of options for the delivery of audio and other services. In most cases transmission costs are expected to be significantly lower than for FM. It has been fully integrated with the FM RDS system and regular transmission of full-time or pilot services are available now in over 20 countries.
The International Funkausstellung (IFA) exhibition in Berlin last September was used as the official launch of Eureka 147 on a world wide basis. Some 14 receiver manufacturers had receivers on display, most of which were fully working pre-production prototypes. Most were DRB/FM/AM car radios, while some hi-fi units were also displayed. All worked very well and many already include highly integrated chip sets comprising one or two main chips, with virtually all components accommodated in a standard car radio DIN slot. Most radio manufacturers expect to have retail receivers available starting from mid 1998 at prices comparable to current top-end car radios.
Eureka 147 still has several hurdles to overcome before being a proven product. These include comprehensive and innovative DRB broadcast services by the broadcasters, ready availability of a range of receivers at affordable prices, appropriate arrangements for sharing multiplexes between possibly competing broadcasters and cost issues related to direct satellite delivery.
Further information about Eureka 147 is available on their Internet web site at www.worlddab.org.
WorldSpace is an innovative system for satellite delivery of digital radio. It is not designed for terrestrial delivery although it will work terrestrially. As with Eureka 147, it has also been under development for several years and has reached the point where the basic design has been completed, satellite construction has started and receiver design is well advanced. All WorldSpace services will operate in the DRB L-Band spectrum from 1452-1492 MHz.
WorldSpace is a private company, based in the USA, which is in the process of launching three DRB satellites, plus a spare. These three satellites are AfriStar, AsiaStar and AmeriStar. Each satellite is planned to have three downlink beams with the coverage of each satellite being broadly as follows:
|Africa, the Middle-East and parts of southern Europe
|From the Middle-East across to Japan including much of China and down to Indonesia.
|Most of South America, Central America and stretching up to include much of the USA and parts of Canada.
The design uses a separate single channel per carrier (SCPC) satellite uplink for each service with access from almost any point on the earth that can see the satellite. The intention is that most broadcasters using the satellites would uplink their own programs from their own premises, independently of any other users of the satellites. This is a strength of WorldSpace as the design does not require any terrestrial trans-border links.
Within each satellite, the uplinked services are received then multiplexed together using a proprietary technology. Although technical details of the design are not yet available, it is understood that the downlinking will also use a single carrier for each beam as this arrangements requires less satellite power than a multi carrier system.
WorldSpace is developing a range of receivers and has let significant contracts for chip designs and receiver manufacture. Receiver manufacturers include Hitachi, JVC, Panasonic (Matsushita) and Sanyo while the main chipset developers are SGS-Thompson and ITT Intermetall. WorldSpace has indicated that its initial receivers are expected to be priced around US$200.
The system design is based on the delivery of audio and/or data in multiples of 16 kbps. For audio they plan to use the MPEG Audio Layer III audio coding which offers generally better audio quality at lower bit rates. It will be possible to link together a number of 16 kbps channels into (say) a 64 kbps stereo channel. Although these data rates sound very low for good quality sound, the results at these low coding rates are generally acceptable and certainly much, much better than shortwave.
As with the Eureka 147 system, WorldSpace will also be carrying data services, both program associated and non-program associated. WorldSpace (as with Eureka 147) is essentially a data delivery technology which has been targeted primarily towards radio. But it also has major potential for the delivery of data services and is expected to be used for this as part of its range of applications. The WorldSpace system is seen as a viable and appropriate technology for the delivery of health, education and community services for many underdeveloped countries.
WorldSpace appears to have the funding and related commitments to construct and launch their satellites and to deliver a working system. However, they still face several challenges. At this time little information is available about which broadcasters and other service providers have signed to use WorldSpace and under what terms. Uncertainties persist over receiver prices, performance and power consumption. The satellite signal strength is unlikely to offer significant building penetration and some orientation of the receiver may be needed for satisfactory reception in places. The signal loss due to foliage will mar reception in timbered areas and the service is unlikely to work all that well in moving vehicles and for portable use. Despite these possible limitations many are confident that WorldSpace has a successful venture that will revolutionise the delivery of audio and data services to well over half the world's population.
Some publicity and technical information is available on their Internet web site at: www.worldspace.com.
2.3 Other Systems
USA In-Band Systems
The USA has been actively seeking a solution to digital radio that would preserve the existing market arrangements for terrestrial radio broadcasting in the USA. The focus to date has been on ‘in-band’ FM and AM systems. Broadcasters in the USA are currently reluctant to adopt systems such as Eureka 147 that use new spectrum as they are concerned that the transition to new spectrum could have a serious impact on existing market shares.
The in-band solutions seek to find ways of adding a digital signal within the spectrum envelope of existing FM and AM radio broadcasts. Most of the effort has concentrated upon FM services with two approaches prevailing. The first seeks to embed the digital signal at a low level underneath the analogue FM service. The alternative aims to locate the digital signals as two packages within each FM channel, one at the lower edge of the FM channel and the other at the upper edge. This arrangement has become known as the ‘saddlebags’ approach.
Several such developments have been put forward by various consortiums with formal evaluation of all systems undertaken about 18 months ago. The outcome was less than satisfactory for all proposed systems and several proponents have since decided not to pursue their designs. However, work on this design approach is continuing and may succeed as newer and more innovative approaches are discovered and the criteria varied to suit the American market.
DRM and NADIB
DRM is Digital Radio Mondiale, a world consortium for digital AM broadcasting. Their efforts focus on both shortwave and MF broadcasting. Further details are available at their Internet web site at www.drm.org.
NADIB is an acronym for ‘Narrowband Digital Broadcasting’. It is a European Eureka project (EU1559) from France and Germany. While both DRM and NADIB are separate organisations, there is potential for fragmentation of effort and outcomes unless these two find a high level of harmonisation. This is an important issue which is now being jointly studied by both organisations.
It is apparent that analogue shortwave and medium wave AM broadcasting are struggling to survive. The question is; can digital offer a new future? The aim of both DRM and NADIB is to provide digital services which compete by offering better quality, both for audio and for reception. Shortwave is clearly the prime interest but the outlook for MW is thought to be optimistic.
Three main technologies are being studied at this time, all of which are in various phases of development. These are:
|T2M (Telefunken - Multicast)
All these systems will support a moderate amount of digital audio together with a small amount of PAD and N-PAD data. ie. program associated data and non-program associated data.
USA Satellite Systems
(Notes from the July 97 issue of WorldDab Newsletter).
In April 1997, the US regulator the FCC, announced the successful bidders in the recent satellite DRB spectrum auction. Two new players, Satellite CD radio and American Mobile Radio Corporation were each awarded 12.5 MHz of spectrum in the S-Band between 2320 - 2345 MHz for a total price of US$172 million. These licences will allow them to provide multichannel satellite DRB services across continental USA only. These companies will now apply for licences to establish new national radio broadcasting services. Satellite CD Radio has said it plans to be in operation by the end of 1999, but there are uncertainties that raise questions about the viability of S-Band spectrum services.
Spectrum co-ordination must be undertaken with neighbouring countries that use this band for non-broadcast terrestrial services while manufacturers will need to design and build a unique range of special receivers. One of the more important concerns is that hard technical evidence gained from the DAB tests in San Francisco in 1996 was that the Voice of America/JPL satellite tests indicated some major satellite limitations in urban areas. These are mainly due to extensive signal blockage by terrain, buildings and foliage (and even street signs) at S-Band that would result in service outages that were almost impossible to restore to ‘CD quality’ without using numerous networks of gap filling supplemental transmitters.
This leads to concerns over the cost of implementing a national, satellite delivered, subscriber-supported, DRB service in this band using currently affordable satellite technology.
ISDB is Integrated Services Digital Broadcasting. It is a Japanese designed system for integrating a wide range of forms of data broadcasting into a single wide band delivery technology. It supports video, audio, still pictures, and a wide range of other types of data. Because its design is not primarily for DRB, no details are provided in this paper.
3. AUSTRALIAN RESEARCH RESULTS AND STUDIES
3.1 Eureka 147 Satellite Tests
The world's first Eureka 147 satellite tests were conducted by Australia in June 1995. Further tests were conducted in December 95/January 96 and a summary of some results are given in this paper.
In both cases the tests were conducted by the DOCA Communications Laboratory with the kind assistance of Optus Communications who made available the full capacity of the L-Band mobile transponder on their B3 satellite. The ABC and SBS also contributed resources to these tests.
The L-Band mobile package on the Optus B-Series satellites is well suited to a Eureka 147 signal as the satellite's transponder is designed to operate with a signal having a large number of independent carriers. This is similar to a Eureka 147 signal. The Optus B3 is a Hughes 601 satellite located at 156 degrees east longitude. The L-Band transponder is a 150 watt solid state power amplifier. The footprint for this service is a national beam which covers an area about the size of Europe. The tests were done at 1552.5 MHz and delivered a satellite signal strength of 46.3 dBW to Adelaide. This is a much lower signal than would be needed for a licensed service, but was certainly sufficient to verify predicted performance and provide extremely valuable results.
The Laboratory's test vehicle drove some 10,000 km including an east/west traverse of Australia from Adelaide to Perth. Tests included taking automated readings every 2.5 cm. The satellite elevation angle varied from 45 degrees at Adelaide to 33 degrees at Perth. On a subjective basis, the testing team commented that there was generally good reception in open areas with extended periods of uninterrupted reception. In suburban and rural areas reception was mostly good except for local obstructions to line of sight by trees with more dense foliage. The direction of travel was important as driving towards or away from the satellite almost invariably provided good reception.
As an example of how good reception can be, the team drove from Adelaide to Eucla, a distance of 1,300 km with no loss of signal except for one underpass just outside Adelaide. Further details of these tests are given in reports by the Communications Laboratory which were also the basis of a paper to the ITU-R.
3.2 Satellite Coverage Objectives
At this point I'd like to share some initial thoughts on possible satellite DRB service objectives for Australia.
Because of the vast size of Australia and its generally low population density, much of the geographic area has no satisfactory radio services. Even many areas that are more heavily populated have only a limited range of services. Satellite DRB is therefore an important public policy issue.
A DRB satellite designed to provide three or four zonal beams would be far more useful than a single national beam. Together they would require about the same overall satellite power but offer more geographically localised services. Four beams with one Eureka 147 ensemble per beam, using a mix of mostly 64 and 96 kilobit services, could offer about 12 to 20 services per zone - a total of 50 to 80 services across the country.
Most of Australia's terrain is reasonably flat and not excessively timbered or otherwise obstructed. The satellite look angle is generally above 40 degrees with a worst case of just over 30 degrees. Interference levels beyond the major population centres are generally low and the years that would elapse before the launch of a DRB satellite are likely to see a range of technical improvements which would make the satellite link budget more favourable and reduce system costs.
Building penetration loss would severely restrict direct satellite reception inside buildings but in-home gap fillers (similar to those proposed for DVB television) would offer a viable solution for households while hybrid repeaters would benefit many small communities. These forms of low-cost terrestrial boosters would offer an affordable means of improving satellite DRB reception in the vicinity of houses and especially for indoor radios. This would be a major boon for homes in rural and remote areas, although there would be nothing to stop people in heavily populated areas doing the same thing. In-home gap fillers in adjacent houses would reinforce the DRB signal rather than creating interference, that being one of the outstanding design features of the Eureka 147 system.
3.3 Canberra Coverage Tests
The good work by our Australian Communications Laboratory did not stop with the satellite tests. They have maintained a semi-permanent test set-up in Canberra for some years now and conducted many test on the Eureka 147 technology. Most recently they have just completed a comprehensive series of tests of a special feature of the Eureka 147 system known as Single Frequency Network (SFN). This is a feature of this technology which allows two or more transmitters to broadcast the same programming on exactly the same frequency with overlapping coverage, without the signals interfering with each other. In fact, the multiple signals will reinforce each other and improve coverage. (This effect is known as 'network gain')
A range of SFN tests were conducted by the Communications Laboratory in and around Canberra to see what could be achieved with two relatively low power DRB transmitters operating in the L-Band. The results were very encouraging and lived up to expectations.
Two transmitting sites were used. The main one on Black Mountain tower was effectively an omnidirectional transmission of about 2 kW ERP. (This compares with FM services there using 50 kW). This was complemented by a second transmitter on exactly the same frequency broadcasting from Tuggeranong Hill with a power or 550 watts. Tuggeranong Hill is about 20 km south of Black Mountain.
This arrangement provided generally excellent coverage for most of Canberra. The report concluded that the majority of the region's population areas would be adequately served by this two site configuration. A small 'gap filler' (very low power repeater) to improve coverage around Fraser, to the north of Canberra, would be advisable and some extension of coverage into outlying rural areas and along major highways would also be highly desirable for a fully operational service.
The results of this work have indicated that a Eureka 147 service using a single frequency network design could be economically provided in Canberra, providing a far better grade of service than the existing high power FM transmitters which now serve much of Canberra's population.
This technique is already being used to cover the whole of Paris, France using a three transmitter SFN operating in the L-Band at relatively low power.
3.4 ABA DRB Task Force
Some two years ago, the ABA established a DRB Task Force to investigate a range of policy and technical issues associated with the introduction of the Eureka 147 DRB system in Australia. The Task Force completed a great deal of investigative work which was reported in two volumes of papers, available from the ABA. The work of the policy group was most valuable as input to the Digital Radio Advisory Committee (DRAC) while the technical report remains a comprehensive and important initial DRB planning tool for Australia.
The technical report established that DRB could be introduced in Australia using the L-Band spectrum 1452-1492 MHz in such a way as to provide for all existing radio services as well as meeting the need for future services and accommodating a range of DRB satellite services. The technical report also covered the cost of establishing services and proposed a number of specific ways of providing adequate coverage of cities and regional areas.
In particular, the report included a preliminary financial analysis of the capital cost of establishing a DRB broadcasting service for a metropolitan city such as Sydney. The model was based upon transmitting four DRB ensembles each containing five CD quality radio services. The proposed infrastructure was based on five medium power DRB sites operating as a single frequency networks and included five low power gap fillers. The estimates included the encoders, multiplexing equipment, transmitters, combiners and antennas but no site costs. The total capital cost of establishing such a broadcasting service was estimated to be $2.99 million or $149,000 per broadcasting service. These costs were revised late in 1997 in the light of reduced equipment costs and availability to a figure of just over $100,000 per service. This is considerably cheaper than for an FM service.
All elements of the transmitting systems are now commercially available with several manufacturers competing for the business. The trend to lower cost transmitting facilities and improved planning tools and equipment for providing gap fillers is expected to see continuing reductions in the cost of transmitting and multiplexing equipment.
4. THE DRAC REPORT RECOMMENDATIONS
The final report of the Digital Radio Advisory Committee (DRAC) was presented to the Minister for Communications Information Technology and the Arts, Senator Alston in September last year. The report has also been publicly released. The DRAC Committee was established by the previous Government as a high level policy advisory committee, including strong industry representation.
The Report, which is the culmination of an investigation lasting more than 18 months, makes recommendations for the development of policy and technology for the introduction of digital radio broadcasting (DRB) in Australia. Australia's radio broadcasters now have an expectation that these services can begin a development phase by the year 2000.
Some of the key recommendations are:
In a speech to the Federation of Australian Radio Broadcasters (FARB) shortly after release of the report, the Minister said that broadcasting is on the verge of a new digital age that will transform the medium as we know it. The media landscape we have grown up with is about to be altered forever. Radio is about to metamorphose into a multi-faceted communications service. Digital radio broadcasting represents a radical and sophisticated new approach to broadcasting. It is probably the most significant event in radio technology since the development of FM - and its impact will be even more far-reaching.
"I therefore want to take this opportunity to announce my support for the introduction of DRB in Australia. At this time, it seems that the Eureka 147 system is probably the way to go, with initial planning of services to occur in the L-Band.’
"There’s a lot of further work to be done before we have a clear idea of what DRB services are going to look like, but at this stage I see incumbent broadcasters being offered the opportunity to move to digital, and opportunities for new entrants as well. I also envisage a continuation of the existing arrangements where there is Ministerial reservation of capacity for national and community broadcasters.’
"The first step is undoubtedly the development of a spectrum allocation plan, accompanied by the detailed licensing arrangements. This work will be undertaken by the Department of Communications Information Technology and the Arts and the planning agencies. This will clearly involve close consultation with the industry, which is essential when DRB presents such challenges to industry."
DRB represents an important opportunity for broadcasters to expand and diversify their radio services through new and different programming, the number of services they choose to broadcast and the development of associated data services.
5. WORLDWIDE DEVELOPMENT OF EUREKA 147
The Eureka 147 DRB system already has fully operational services in some countries while many countries have pilot services and are conducting local research. While the primary emphasis is in Europe, many other countries are becoming more actively involved, including a significant upsurge in interest in Asia over the last year or so.
The following table provides an update, based on information provided by WorldDab in August 1997. The countries with the most extensive operational networks at this time are the United Kingdom, Sweden and Canada.
Experimental facility in Canberra. Development services in 2000
14 transmitters covering 80% of population. One ensemble at present
!5 services in Toronto, 10 in Montreal, 5 in Vancouver. All in L-Band
Test in 3 cities in Guangdong Province. Plans for Beijing.
Cover 25% of population with national ensemble
National ensemble covering 20% of population
L-Band pilot in Paris with 3 ensembles covers 10% of population
More than 50 tests and pilots covering 50% of population
One pilot multiplex covering 3 million people
Test transmissions in Delhi
Pilot in Beseq covering 70% of population
Pilot service in Aosta Valley covering 10% of population. Turin and Milan soon
Terrestrial and satellite experiments at L-Band
Single national multiplex covers 45% of population
National ensemble with 5 services covers 35% of population
National ensemble covering 8% of population with one transmitter
Further trials underway with services in 1998
Pilot project started
Testing being carried out
Test transmissions in progress
National ensemble covering 45% of population. Plan to extend to 75% in 1998
Pilot projects in Berne-Oberland and Geneva covering about 2 million people
3 multiplexes (BBC and commercial) covering up to 60% of population
6. DRB PLANNING AND DIRECTIONS
6.1 Service Planning for Digital
Planning for digital radio and TV is very different from analogue.
One of the main reasons is that digital services have a very sharply defined limit of coverage. If you are inside the area served you will probably get absolutely perfect reception almost all the time. If you're just outside you may get no reception. The point where the digital service cuts out is mostly very well defined. This is very different from analogue.
Analogue service planning is based on the rule known as the 50/50 rule. This says that within the intended service area, 50% of the audience will have an adequate grade of service for 50% of the time. For digital we need to plan for something in excess of 90% of the audience for 90% of the time.
Transmitter siting and power levels are also very different for digital. For example, it's not good enough to have all the transmitters for an area located in the same general area. Ideally they should be co-sited on the one tower. This has major advantages for spectrum efficiency, both short term and longer term. It offers the most uniform coverage for all services and enables the use of low power, low cost, SFN gap fillers.
These are but a taste of some issues that will need to be addressed in planning digital terrestrial broadcasting services, both radio and TV. Digital is really very different from analogue and we will need to go through a learning process that may be difficult at times.
6.2 DRB Directions for Australia
For digital radio to succeed, the broadcasters must take the initiative and commence digital services soon. They will need to work together as an industry group, in conjunction with the ABA and the receiver manufacturers, to start delivering services. This can be done. This approach is now working for the Europeans in developing their DRB services and for the USA in developing their ATSC digital television system.
One of the most important messages coming out of recent developments in Europe is that DRB receivers should not be offered to the general public in an area until the DRB services can offer excellent coverage as well as attractive programming. Selling receivers when coverage is incomplete will simply give the technology a bad name.
In Australia we need to focus initially on the planning and testing needed to develop services providing close to 100% coverage of both Sydney and Melbourne, (and perhaps Canberra as well). This would provide a sufficiently developed set of initial services to 'test the market' with a meaningful range of services during the initial DRB development period. It would be an affordable first step for existing broadcasters which could then be built upon to extend services to more of Australia as the technology becomes proven and accepted by consumers.
The industry has the capability to undertake this task and achieve good outcomes. It can do it, and do it well.
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