Communications Laboratory

New Television and digital Sound broadcasting technologies

The two main ongoing study programs being conducted at the laboratory involve new television and digital sound broadcasting technologies.

New television technology studies currently have a focus on Digital Terrestrial Television Broadcasting (DTTB) systems. The main contributions from the laboratory have been to identify user requirements and test methods for evaluating the proposed systems. Demonstration material is available to show the performance of many of the emerging systems.

A program of Laboratory tests of DTTB modulation technologies has just been completed with competing systems from Europe (DVB) and America (ATSC) tested. The Laboratory has also assisted with the Field evaluation and demonstration of both these systems in Sydney and Canberra during 1997.

Digital sound broadcasting represents a new form of sound broadcast technology. It promises to deliver compact disc quality sound - and a diverse range of data based services - to vehicle, home and portable receivers with fewer transmission impairments than current AM and FM broadcast systems.

The laboratory’s early work in digital sound broadcasting involved the subjective evaluation of audio compression systems, in collaboration with three overseas research centers. The results of this work led to an ITU Recommendation for low bit rate audio coding systems for use in digital sound broadcasting. The recommended audio compression scheme, commonly known as MUSICAM, now forms the basis of the Eureka 147 Digital Audio Broadcasting system.

Currently the laboratory is working on the study of signal coverage and planning prediction methods for L-Band (1452MHz to 1492MHz) operation, as a precursor to possible planning of digital sound broadcast services in Australia. The laboratory has assembled an L-Band Digital Sound Broadcast (DSB) transmission system, to facilitate demonstrations of the Eureka 147 system and to provide a ‘test-bed’ for ongoing technical studies into the technology.

The laboratory is also providing technical assistance to the National Transmission Agency (NTA) in a a program aimed at establishing experimental digital sound broadcast facilities in three Australian capital cities. At present there is a fully operational DSB Single Frequency Network with live programming covering the Canberra area. Transmitters for this service are located on Black Mountain tower and Tuggernong Hill and are being maintained by the Laboratory and the NTA. A normal Holden station wagon has been equipped with a DSB receiver, GPS and computer logging equipment to allow field evaluation of the systems performance.

The delivery of digital sound services by satellite is also of interest to Australia. The laboratory, in conjunction with OPTUS Communications, has taken a leading role in this area by implementing the first L-Band satellite trials, world-wide, of the Eureka system. Based on the success of these initial trials additional investigations are planned in collaboration with OPTUS, the Australian Broadcasting Corporation (ABC) and the Special Broadcasting Service (SBS).

Radiocommunications services standards

Work is continuing with the Australian Communications Authority (ACA) and Standards Australia to develop standards for radiocommunications services. The laboratory has completed a long term measurement program of background electrical noise for the ACA. Studies related to personal communications services and infrastructure-sharing issues for cellular telephone services have been completed in recent years. Work is continuing on RF exposure levels.

The laboratory also provides technical assistance to the study and correction of radio interference problems and difficulties with reception of broadcasting services encompassing both terrestrial and satellite service problems. There is a substantial ongoing program of technical cooperation with the NTA, FACTS, FARB and the broadcasting industry in general.

International projects

Laboratory staff have also been involved with elements of the Australian and New Zealand television industry in developing a joint Australian/New Zealand standard for a ghost-cancelling reference signal for PAL television which has been based on work in the ITU-R Working Party 11A (WP 11A).

WP 11A has also been studying the requirement for coincidence of timing between the video and audio components of a television signal. The laboratory undertook the English speaking part of the study, while similar laboratories in Japan and Germany completed the studies in their own language.

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