User:Ryan Cooley/DAB
Rough Draft. Probably take a month to look like anything.
Digital Audio Broadcasting (DAB, or EUREKA-147) is a standard for transmitting lossy encoded digital audio.
History
In 1988 the E!147 project started.
"The BBC started a new service of Digital Audio Broadcasting on 27 September 1995 in London."
In 1995 the BBC was experimentally broadcasting in DAB.
"The EBU and the Eureka 147 DAB (Digital Audio Broadcasting) project set up a joint group in 1992, in order to evaluate the performance of the Eureka 147 DAB system."
DMB...
DAB+ was published in February 2007
RF
OFDM:
Multipath, Doppler Shift, Interference.
Inter-Symbol Interference (ISI)
Fast Fourier Transform (FFT)
differential QPSK - no channel equalization needed
Guard Interval
1/4th symbol length interval
copies end of symbol before start of symbol
Multipath
Single-Frequency Networks (FSN)
Synchronization
Null symbol
Phase Reference Symbol (PRS)
Frequency-Domain Multipath
(Punctured) Convolutional Coding (COFDM) Forward-error correction (FEC) Normally; half-rate. == 1.2Mb/s Viterbi Bit-stream re-ordering; Pre-determined patterns Temporal: Between Frames; depth 360ms Frequency: Interleaving.
4 transmission modes, 1,2,4,8KHz wide
Mode 1: Band III (4x1.54MHz DAB in 7MHz UKTV space) 70km max SFN antenna spacing Mode 2: L-Band (1452-1492MHz, world) est 17km max SFN antenna spacing Mode 3: up to 3GHz for satellite est 8km max SFN antenna spacing Mode 4: L-Band, sometimes appropriate est 35km max SFN antenna spacing
useful payload (0.6 - 1.7 Mbit/s) available. 6 x 192Mb/s MP2 = 1.2Mb/s Fast Information Channel (FIC) - Non-interleaved Multiplex configuration information
reference frequency and timing information
?Service Information (SI) Main Service Channel (MSC)
MP2 audio
Packet Demux for datacasts 24ms frames
Data Services
standardised by the European Telecommunications Standards Institute "ETSI specification, EN 300 401 (Second Edition) specifies the transmitted DAB signal."
'CD quality' using bit-rates of 192 kbit/s or above for stereo
Transmission mode I is intended for terrestrial Single Frequency Networks (SFN) and loca-area broadcasting in Bands I, II and III. Transmission mode II is intended to be used for terrestrial local-area broadcasting in Bands I, II, III, IV, V and in the 1,452-1,492 MHz frequency band (i.e. L-Band).
The DAB signal comprises a succession of transmission frames of 96 ms duration in mode I and of 24 ms duration in mode II. Within these transmission frames, the synchronization channel occupies approximately the first 2.544 ms in mode I, and approximately 0.636 ms in mode II.
(Mode I) ... permits the use of relatively widely-spaced transmitters, whereas in transmission mode II the However, mode II has fewer radiated carriers; also, for mobile reception in L-Band, the greater frequency seperation of the carriers is intended to reduce the effect of Doppler shifting for reception in moving vehicles, especially at the higher speeds. There are 1,536 radiated carriers in mode I, and 384 carriers in mode II, in a system bandwidth of about 1.54 MHz.[1]
UK
"The BBC covers 85% of the UK population" [2]
"In the United Kingdom, 12.5 MHz of Band III spectrum from 217.5 - 230 MHz has been allocated to DAB. This will accommodate seven multiplexes. The BBC has been allocated one of these channels for its national DAB multiplex"
"RDS travel bulletins to interrupt listening,"
World
"100 million people"
DAB+
MPEG-4 HE-AAC v2
DAB+ was published in February 2007 as ETSI TS 102563 "Digital Audio Broadcasting (DAB); Transport of Advanced Audio Coding (AAC) audio".
HE-AAC v2 provides the same perceived audio quality at about one third of the sub-channel bitrate needed by MPEG Audio Layer II.
DAB+ Bullshit[3]
Moser AAC+ Bullshit. Does not mention MP2 at all[4] Ridiculously low AAC bitrates are cited are based on MUSHRA (Multi stimulus hidden reference and anchor) testing, versus ITU-R BS.1116-1 testing for older, higher MP2 bitrates.
CTAAC+ http://www.ebu.ch/trev_291-dietz.pdf
DRM http://www.ebu.ch/trev_286-stott.pdf