Digital Signal Processing Reference
In-Depth Information
•
Germany:
mostly 192 kbit/s, PL3
60 kbit/s or 192 kbit/s in some cases, PL4 (one additional per
gram)
•
UK:
256 kbit/s, classical music
128 kbit/s, popular music,
64 kbit/s, voice
Q
/4shiftDQPSK
I
Signal band
width =
1.536 MHz
f
f=1, 2, 4, 8kHz
Channel bandwidth
7/4 MHz = 1.75 MHz
Fig. 26.8.
DAB COFDM channel
26.3 The Physical Layer of DAB
In the section following, the implementation of COFDM in Digital Audio
Broadcasting DAB will be discussed in detail. The main item of concern
are the DAB details at the modulation end. COFDM is a multicarrier
transmission method in which, in the case of DAB, between 192 and 1536
carriers are combined to form one symbol. Due to DQPSK, each carrier
can carry 2 bits in DAB. A symbol is the superposition of all these indi-
vidual carriers. A guard interval with a length of about 1/4 of the symbol
length is added to the symbol which has a length of between 125 Μs and
1 ms. In the guard interval, the end of the following symbol is repeated
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