The Extension of DRM to Frequencies up to 108 MHz: DRM+

DRM+ is the name of the Consortium's project to extend the DRM standard to higher frequencies. The initiative began with a vote at the 2005 General Assembly to begin the design, verification and testing of the parameters needed to allow DRM to operate in the broadcasting bands between 30 and up to 108 MHz ; primarily Band I and Band II.

The design process began shortly afterwards and the key decisions were made to ensure that the extension completely shared the successful design philosophy of DRM - it is “DRM but at higher frequencies”.

Therefore, it has:

– the same multiplex and signalling scheme

– the same OFDM design (with new parameters)

– the same audio codecs

DRM+ is implemented in the standard as robustness mode E. Its spectrum usage parameters are determined from the internationally agreed norms in the FM band (88 to 108 MHz). Therefore it has an occupied bandwidth of 95 kHz and a frequency grid of 100 kHz.

DRM+ provides bit rates from 35 kbps to 185 kbps at SNRs from 2 dB to 14dB and, like DRM, permits up to four services. It is therefore a flexible solution allowing single or small numbers of audio services to be broadcast together, or even for video streams to handheld devices.

Status

The additional mode for DRM+ was agreed and finalised during 2007. However, before the ETSI standardised DRM system specification is updated, the Consortium's members will test and verify the design with both laboratory and field based tests.

These are currently underway in Germany - the authorities in Hanover/Lower Saxony and Kaiserslautern/Rhineland-Palatinate have provided test licences.