Digital Radio Mondiale (DRM): Features and Architecture

This page outlines the key features of Digital Radio Mondiale (DRM) and its architecture. DRM is an open standard developed by ETSI for digital audio broadcasting, designed as a replacement for analog FM broadcasting in narrowband applications. It primarily transmits audio in the shortwave and medium wave bands.

DRM Features

• Bandwidth Flexibility: DRM supports various bandwidths, including 4.5 kHz, 5 kHz, 9 kHz, 10 kHz, 18 kHz, and 20 kHz, across four different modes. This allows for varying bit rates.
• Bit Rates:
  • 9-10 kHz bandwidth: Supports bit rates from 8 to 20 Kbps.
  • 2-4 kHz bandwidth: Supports 2 to 4 kbps.
  • 18-20 kHz bandwidth: Supports 20 to 80 Kbps.
• Audio Quality: DRM offers near-FM sound quality.
• Data Transmission: Beyond audio, DRM can display data on the receiver.
• Audio Coding: DRM specifications support efficient audio coding techniques such as Meltzer Moser MPEG-4, HE AAC V2, HVXC (Harmonic Vector Excitation Coding), and CELP (Code Excited Linear Prediction).
• Data Support: Supports HTML pages and streaming data.

DRM Architecture

Figure 1: DRM Architecture

As illustrated in Figure 1, a DRM transmitter consists of various encoding and physical layer blocks. Audio, data, FAC, and SDC information traverse these stages before being transmitted.

• The DRM system incorporates three primary paths: MSC, SDC, and FAC.
  • MSC (Main Service Channel): Carries multiplexed audio and data. The MSC uses unequal error protection, where the multiplexed frame carries two different levels of protected data: lower and higher protection.
  • SDC (Service Description Channel): Contains information required to decode the MSC.
  • FAC (Fast Access Channel): Carries OFDM properties and SDC/MSC configurations, limited to approximately 72 bits per frame.