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

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" 

 "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"