Multipath reception
The signal propagates from the transmitter antenna to the receiver on multiple paths via reflections from buildings or natural obstacles. In the case of analogue systems such as VHF, this leads to reception interference, whereas with T-DAB und DVB-T it leads to quality improvement.
Mobile reception
Mobile reception is the name given in broadcasting to the reception of digital radio or television signals at travel speeds of between 10 and 150 km/h (for example TV reception in a travelling train). See also portable reception.
Mode
DAB can be transmitted in four different modes (not to be confused with the protection levels). These modes optimise the different transmission types and coverage. Essentially, they modulate the COFDM single frequency networks optimally. In each of the four modes (I, II, III, IV) a different set of parameters such as symbol duration, guard interval, null symbol duration, subcarrier number, subcarrier distance, etc. is selected.
- Mode I: Optimised for VHF transmission (band III - channel 12) and therefore used for national ensembles. Permits interference-free reception up to approx. 240 km/h. Uses 1536 subcarriers.
- Mode II: Optimised for broadcasting in the range up to 1.5 GHz. A smaller number of subcarriers, a greater carrier distance and a shorter guard interval are used. Suitable for use in small SFNs, e.g. for regional/local ensembles in the L band.
- Mode III: Optimised for broadcasting DAB via satellite over frequencies up to 3 GHz. It has a short symbol duration and a short guard interval.
- Mode IV: Is a compromise between mode I and mode II with some special features.
MOT, Multimedia Object Transfer
Transfer of multimedia data
MPEG
Acronym for Motion Pictures Expert Group. The acronym refers to the most common standard currently used for data compression in moving (video) pictures. This group laid down and is laying down the file formats and procedures for the high-quality, space-saving compression and storage of video and multimedia data (video, photo and audio data). The MPEG standard has since divided into MPEG-1, MPEG-2, MPEG-3 and MPEG-4, with the MPEG-3 standard having been integrated into MPEG-2. In order to be able to process and transfer the huge amount of data in movies (90 minutes of video, 25 frames per second, high resolution, rich colours = approx 120 GByte) with "normal" computers, only the changes from picture to picture are saved. With this method, the volume of data needed for a video film can be reduced by about 99%. The maximum compression is 200:1.
Multiplex
In digital broadcasting, programme packages rather than individual programmes are broadcast for frequency reasons. The multiplexer is a computer which combines several programmes into a single data stream - the multiplex - before broadcasting them. As the data are digital, it is possible to simultaneously transmit audio, video and other types of data. A radio data package (ensemble) comprises eight to ten programmes, a TV package (bouquet) four to six.
MUSICAM
Acronym for Masking Pattern Universal Sub-Band Integrated Coding and Multiplexing - a procedure for audio data reduction; sounds below the threshold of hearing at silence and threshold of audibility for listening (auditory masking threshold ) are filtered out without any degradation of audio quality.
NPAD, Non-Programme Associated Data
Data services not associated with radio programmes
