With the EuroDab Forum now renamed the WorldDAB Forum, the Author reports on the progress of DAB implementation to date, and offers a pointer to the future prospects for Eureka-147 DAB.

In this article, the Authors provide a progress report on the world-wide studies of digital terrestrial television broadcasting, carried out by ITU-R Task Group 11/3.

The final meeting of Task Group 11/3, held in Sydney during November 1996, was highly productive and extremely successful. International agreements - defining a complete digital terrestrial broadcasting system - were finalized. The Reports and Recommendations (standards) have now been forwarded to the parent bodies of Task Group 11/3 for formal approval, which is expected later this year (1997).

The specification for digital terrestrial television, DVB-T, offers a wide range of potential applications: single transmitter and single-frequency networks, prohibited channel operation, portable reception, hierarchical transmission, etc. The network operator can select technical parameters such as the number of OFDM carriers, the length of guard interval, the degree of error protection and the modulation method. The last two parameters in particular allow the operator to reach a compromise between the number or programmes carried and their transmission reliability. This raises the question of which results, with regard to coverage, need to be achieved in each case.

The main applications have been studied at the IRT using Monte Carlo simulations of regular network situations. The results are documented here in the form of predictions for the coverage probabilities. The reasons for the choice of parameters for the terrestrial specification are dealt with specifically. Ways to restrict the basically very wide choice of system state (modes) can also be derived from these simulations.

The forthcoming introduction of interactive video services such as video on-demand, which is facilitated by recent advances in source and channel coding as well as modulation, calls for a network platform via which the subscriber can access the appropriate source of information.

Two such approaches - the use of existing broadband CATV and the use of telephone networks - are detailed in this article. In the case of CATV networks, special emphasis needs to be placed on return channels.

In this article, the Author proffers his assessment of how far multimedia services have progressed during 1996, and gives a personal insight into how the market may develop in the next year or two.