DRM+
Technology Overview
DRM+ is an expansion of the existing DRM standards with regard to the useful frequency range. DRM+ therefore must likewise be able to digitize VHF sound broadcasting. Digital radio mondiale (DRM) was developed as a digital sound broadcasting standard for worldwide use in long wave (LW), medium wave (MW) and short wave (SW). DRM is used for sound broadcasting as well as to transmit additional digital data for frequencies up to 30 MHz.
The frequencies required are exposed to highly fluctuating propagation conditions. In this frequency range, the waves are influenced by the ionosphere, and they are reflected depending on the time of day, season, and relative number of sunspots. In this frequency range, primarily AM has previously been used for sound broadcasting. Thanks to the digital standard, the AAC+ audio coding and the COFDM technology, signal transmission now promises outstanding quality as compared to conventional AM broadcasting.
Deployment scenario
DRM can use the existing band plan and the frequency grid present in medium wave, long wave, and short wave. The technology therefore facilitates the transition from analog to digital transmission technology, which can cover large areas end-to-end at a favorable price. Due to the external influences on the transmission conditions, the transmission parameters can be adjusted to match the propagation conditions.
One advantage from using DRM+ is also the significantly lower power consumption of the transmitting systems.
Key Parameters
| DRM+ | |
|---|---|
| Frequency | 48 Hz
- 68
MHz
(band I) 65.8 MHz - 74 MHz (OIRT FM band) 76 MHz - 90 MHz (Japan FM band) 87.5 MHz - 107.9 MHz (band II) |
| Modulation | COFDM |
| Bandwidth | 4.5, 5, 9, 10, 18, 20 kHz |
| Data Rate | 35 kbit/s - 185 kbit/s |
| Audio Source Coding | MPEG 4 HE AAC v2 (AAC+) |
Standardization
DRM+ is driven by the same consortium as DRM. Therefore, it needs to be included in the ETSI ES 201 980 standard as a supplement.
