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.
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
ConvolutionalCoding(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
UK
"The BBC covers 85% of the UK population" [1]
"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[2]
Moser AAC+ Bullshit. Does not mention MP2 at all[3] 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