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A Discussion Paper on
Digital Radio Broadcasting in Australia

Technology

A number of technologies are being developed to deliver DRB services via terrestrial and satellite means.

At this stage, two types of DRB technology are potentially available for delivery of terrestrial services - Eureka 147 and in-band. Eureka 147 is the only system presently in operation and can deliver satellite services to receivers used for terrestrial services. In-band systems are still under development in the US.

It is the preliminary view of the Digital Radio Advisory Committee (DRAC) that Eureka 147 is the preferred system for Australia, but that developments of the in-band system should continue to be monitored.

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Eureka 147
Eureka 147 was developed in Europe by a consortium of broadcasters. The Eureka 147 system uses advanced digital techniques to convert the audio signal from an analog waveform to a digital signal, sampling the amplitude of the wave and creating a stream of ones and zeros which accurately represent the original sound. The sampled information is digitally compressed, and several audio channels are brought together and encoded into a single data stream by means of a multiplex. Data and other services are added. The whole digital stream is referred to as an ensemble. Receivers separate and decode the signals in the digital stream.

Each multiplex is able to provide: five CD quality programs; or around six FM quality services; or around 12 AM quality services; or around 30 voice channels; or some combination of these depending on how much of the available data capacity needs to be used for error protection to ensure continuous coverage. The signals can be dynamically reconfigured. In other words, a high quality service can be switched readily to a number of lesser quality services or vice versa.

Eureka 147 permits the establishment of single frequency networks. These allow for wide area coverage using several transmitters carrying the same signal on the same frequency, so that reception can be maintained when travelling from one area to another.

Signals using the Eureka 147 system can be retransmitted on the same frequency to provide 'in-fill' coverage in areas of poor reception. Additional transmitters can also be used to 'shape' coverage to match the intended service area. It may also be possible, with Eureka 147, to provide for insertion of limited local programming. This is currently being further examined in Europe.

Eureka 147 generally allows for more effective spectrum use than analog technology in terms of the number of services that can be carried in a given amount of spectrum and in providing adjacent local coverage areas.

The Australian trials utilise the Eureka 147 system. Canada and a number of European countries (including the UK) have commenced services using Eureka 147. Major radio manufacturers have obtained access to the proprietary Eureka 147 technology.

Depending upon the technical arrangements, the Eureka 147 system may offer:

• more reliable reception to fixed, portable and mobile receivers than current AM or FM radio;
• higher quality sound than AM or FM radio, providing an appropriate bit rate is used;
• program associated information and ancillary services;
• use of one receiver for both terrestrial and satellite reception;
• the capability to reconfigure services for different programming requirements;
• more effective use of spectrum than analog services;
• reduced radiated power requirements for coverage of a given area than analog services;
• greater flexibility in coverage than analog services;
• the ability to operate over a range of frequency bands; and
• generally lower or comparable capital and operating costs than AM or FM radio.

Comment is invited on the committee's preliminary view that Eureka 147 is the most appropriate delivery system for Australia.

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In-band
The two main in-band systems under development are In Band On Channel (IBOC) and In Band Adjacent Channel (IBAC). The IBOC system transmits a digital signal simultaneously within an existing analog AM or FM signal. The IBAC system transmits a digital signal within unused spectrum adjacent to that used by existing FM signals. In Band Reserve Channel (IBRC), which is based on using 'spare' spectrum not able to be used for other services, is also a possibility.

There is strong industry support in the US for the in-band approach, where a number of in-band systems (along with Eureka 147) are being assessed. The assessment involves laboratory tests, completed in 1995, and field tests. The in-band systems do not appear to have performed as satisfactorily as hoped for by their proponents. A recommendation is expected to be made to the US Federal Communications Commission in late 1996.

The characteristics of in-band systems are a subset of the characteristics of Eureka: CD and high quality stereo sound; and ancillary data, text and other services.

One fundamental difference between in-band systems and Eureka 147 is that, because they operate within or close to existing frequency allocations, some in-band systems (notably IBOC) should allow for a smooth transition from existing services. For example, it would not be necessary to allocate new spectrum for digital services.

Eureka 147, however, is the only proven digital transmission system in operation. It is capable of operating over a wide range of frequency bands, appears to be less prone to interference from other signals and offers compatible satellite and terrestrial delivery. Eureka 147 also offers the additional capability of single frequency network operation, as well as providing a platform for the development of a range of new services.

Comment is invited on the relevance of in-band systems for DRB delivery in Australia.

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Satellite
There are approximately 12 proprietary systems, including Eureka 147, for broadcasting digital radio via satellite. Each requires transmission and reception infrastructure unique to that system. Of the various satellite proposals, perhaps the system most likely to commence in the next few years is Worldspace. The intended coverage of the Worldspace satellites is primarily Africa, the Middle East, Asia, Latin America and the Caribbean - those areas where Worldspace sees a dearth of high quality radio coverage. It would, therefore, have no primary coverage over Australia, but could affect Australian services by 'spill' from the Asian beams.

Because the same receiver could be used for Eureka 147 terrestrial and satellite delivered services, a Eureka 147 satellite system could deliver services to underserved regional and remote areas - and in areas where terrestrial transmission is limited by topographical and other features - as well as providing almost continuous mobile reception across Australia. These services could be broadcast via satellite and terrestrially on the same frequencies so that listeners would be unaware of the means of transmission, or any changeover from satellite to terrestrial transmission.

A proposed Australian DRB satellite, known as DBSTAR, has been published in accordance with International Telecommunication Union (ITU) coordination procedures as an Advance Notice.

Comment is invited on the use of satellite systems for DRB delivery in Australia.

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Radiofrequency spectrum
There are a number of broadcasting spectrum allocations being considered by individual overseas countries for the introduction of DRB. The main spectrum options being considered include:

• the frequency band from 1452 to 1492 MHz allocated at the World Administrative Radio Conference (WARC-92) for terrestrial and satellite uses (commonly referred to as the L-band);
• existing terrestrial AM and FM terrestrial radio frequency bands; and
• existing terrestrial broadcast band frequencies (VHF Band III).

The L-band is allocated internationally (except for a small number of countries, most notably the US and the Russian Federation) for terrestrial and satellite DRB. It is also allocated to other services, including fixed and mobile services.

In Australia, approximately 60% of this band is occupied by fixed microwave links. These include point to point and point to multipoint links providing various facilities for a range of users. The band is also used by the Department of Defence for aeronautical telemetry.

One of the main uses of this band is the delivery of telecommunications to rural and remote areas of Australia. This involves 3 500 transmitters (involving 400 base stations) utilising 23.5 MHz of the 40 MHz in this band. There is a potential conflict between the possible future use of the band for DRB and the ongoing needs of this band for delivery of these services.

ITU studies indicate that there is potential for sharing between terrestrial DRB and fixed services if there is sufficient geographic separation. If the band is to be shared, suitable planning arrangements may need to be developed.

Some initial planning work has been undertaken by an industry-based group under the auspices of the Australian Broadcasting Authority (ABA). The planning assumed one DRB allocation - capable of providing a good quality sound program plus a small allowance for related data - for every existing AM and FM radio broadcasting service, with coverage areas varying from suburban to national. Up to five services with similar coverage areas were grouped together to share the same transmitter. Allowance was made in the planning for implementing a satellite component (a mixed satellite and terrestrial network). Using this model, it was determined that a minimum of 15 DRB channels, or around 26 MHz of spectrum, would be required to allow all existing AM and FM radio broadcasting operators to provide DRB services and that, by carefully assigning frequencies to DRB ensembles in particular areas of Australia, it should be possible for DRB to share the L-band with existing spectrum users.

The AM and FM radio bands are being considered for in-band digital radio in the US, but it is not yet clear whether a suitable technology will be able to be developed. Some consideration is being given to using Eureka 147 in the FM bands but this requires prior clearance of existing FM broadcasters.

VHF band III, around 220-230 MHz, is being used by some European countries for terrestrial digital radio services. In Australia, the television Channel 12 (223-230 MHz) was not used for television due to its original use by air navigation, but this was cleared at the end of 1995. The ABA has allocated Channel 12 in one area for television use.

Comment is invited on:

• existing uses of the L-band and the implications for implementation of DRB;
• the future relative spectrum needs of existing services and DRB (both frequency and geographic sharing requirements);
• sharing of spectrum between existing services and DRB terrestrial and satellite uses of the L-band; and
• spectrum planning arrangements.

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• Document ID: 9349 |
• Last modified: 6 February 2008, 2:24pm