Introduction on DAB/DAB+

Revision as of 17:09, 28 December 2010

DAB, DAB+ and T-DMB European digital radio and mobile television standards share the same transmission system. It based on OFDM modulation and use 1.5MHz of spectrum in VHF television band 3 (or L-band in SHF). A transmitter is broadcasting a set of programs, called a multiplex. The system has been designed for mobile use and is robust up to 300km/h.

With the development of MMBTools set made by CRC, it is now possible to run a full transmission infrastructure on a laptop running linux and using a USRP as RF hardware (with gnuradio) or any other similar device.

The transmission chain can be divided in 4:

• The encoding: encoding the sound to MPEG-2 Layer II for DAB, MPEG-4 HE-AACv2 for DAB+ or video in MPEG-4 H.264 for T-DMB.
• The Multiplexer: gather different streams, produce necessary signalling and output a single 2Mbit/s stream in ETI format (Ensemble Transport Interface)
• The Modulator: take the ETI stream and produce the complex baseband OFDM signal ready for upconvert at the desired radio frequency.
• The RF transmission performed by the USRP using appropriate RF daughterboards (Basic TX or modified RFX400).