Monday 18 November 2013

Small-scale DAB Still Not for Local Radio

No FM switch-off in Sweden before an alternative is found
WorldDMB – the organization promoting DAB radio – had its 2013 General Assembly in Amsterdam November 6th. One of the conference sessions was "Small scale solution for local broadcasters". Ofcom presented a cost efficient "local DAB" solution as a demonstrable prototype, using SoftWare based encoding equipment with a low cost amplifier and transmitter.
However, this solution still has some standardisation hurdles and experimentations to overcome. It does not solve the prime problem of how to run a local mux efficiently with only one or two programs, the remainder of the mux being empty. 
An Ofcom spokesman was asked how they perceive the problem of (mostly) empty muxes to be solved and he answered: Well, the community radio stations simply have to recruit a sufficient number of co-users on the mux, for example by inviting internet start-up radio stations to join.

There are 2.200 community radio stations in Europe. Most are on FM and operating on non-profit basis one channel per location. Besides large metropolitan areas there will not be any resources to run more than one community radio channel per village or town.

A DAB/DAB+ channel is always 1.5 MHz wide and in less populated areas it might contain as little as one program – pure spectrum waste, whereas a DRM+ channel with a similar performance is only 100 kHz wide (half as wide as an FM channel).

As a DAB multiplex can carry up to 16 programs, where the full multiplex is not fully utilized it becomes very inefficient and means that using DRM+ instead would require about 10% of the DAB radiated power. It is widely accepted that, when replacing FM transmissions on a one-for-one basis, a DRM+ transmission needs much less spectrum and energy than FM in order to provide the same high audio quality. The spectrum needed for each programme stream is about one quarter of that needed for an FM sound broadcasting channel. These advantages have been confirmed by DRM+ test transmissions carried out in Edinburgh by the BBC and the DRM Consortium and also in a series of European countries (i.e. Italy, France, Norway, Germany).

In Sweden it is already politically established that DAB+ will not be feasible for small-scale broadcasting. The parliament will decide on DAB+ for public service in the end of 2014 or in 2015. However, there will be a government assignment for the media authorities to find a digital alternative for community radio 2016. A switch-off date for public service FM will not be set before this alternative for local radio is presented and accepted.