The new EBU Technical Report 035 ‘An introduction to Time-Frequency Slicing (TFS)’ has just been published. This report provides further details and results of a number of theoretical studies and takes a closer look at the deployment of TFS in practical scenarios, based upon the existing networks in France, Sweden and UK.
Over the last few years, different research institutes and universities have been looking for new network planning methods to increase the efficiency of broadcast systems. Organizations like DVB and ATSC have also considered advanced methods when discussing new generation standards.
The EBU Project Group, Broadcast Network Planning (BNP) has analysed how some of these new methods might be deployed in practical networks and the implications for broadcasters and viewers.
Time Frequency Slicing (TFS) is a technique that enables multiple frequency channels to be aggregated into a single wider frequency channel. The content of individual programmes is sliced into ‘blocks’ of information which are transmitted in different frequency channels within the TFS aggregation.
The frequency diversity between channels (e.g. differences in antenna diagrams and receiving antenna gains) could extend the core coverage area of the multiplexes transmitted or, alternatively, increase the capacity of the multiplexes (by changing the system variant to take advantage of the improved robustness).
Simulations, supported by field measurements, indicate that combining four to six RF channels may achieve, for standard fixed rooftop reception, a capacity gain of some 20 – 25%. Such additional capacity could facilitate the introduction of additional high- and ultra-high definition (HD and UHD) programmes which would allow viewers to watch the programmes they want in high quality. In addition, research shows there would be statistical multiplexing gains in the order of 15%.
In terms of coverage gain, TFS has the effect of equalising the coverage of all multiplexes in a TFS-signal. This is particularly well-suited to applications where this is desirable, but might be a problem in cases where services have different target areas.
In terms of practical effects, consumers would need to buy new TFS-compatible receivers but would not need to change their receiving aerials. Broadcasters and network operators would need to upgrade modulators and multiplexing systems and introduce more SFN-like timing.
TFS has clear benefits for future DTT standards but to make the transition more attractive it would need to be introduced alongside other improvements such as HEVC or UHD Phase 2.
To access the publication, click here.