Pioneer GEX-P900DAB Service Manual page 56

GEX-P900DAB
3) Guard interval
The time 25% more than the sampling time required for processing DAB signals by FFT is called "guard interval." For
multipath within the time of guard interval, errors can be corrected in most cases, regardless of the D/U ratio.
Mode 1
S1
S1
S1
The time of guard interval depends on modes. Different time of guide interval is used for transmitting frequency,
receiving speed (vehicle speed), etc.
56
2048 points (1 ms):
512 points (250 µs):
Delayed multipath wave
S2
S2
Direct wave
(OFDM wave)
Interference between
different symbols
(effect of delay)
Guard interval (250 µs)
S2
Time required for FFT for every symbol
Number of samples required for FFT
Guard interval
Actual DAB signal
Time required for FFT
(1 ms)
Received DAB signal