Digital Signal Processing Reference
In-Depth Information
protection. From the puncturing index, the code rate in the relevant section
can be easily calculated using the following formula:
code_rate = 8/(8+PI);
where PI = 1 … 24, the puncturing index.
The puncturing index, in turn, is obtained from the protection level,
which is in the range 1, 2, 3, 4 or 5, and the audio bit rate. Table 26.3. lists
the mean code rates as a function of protection level and the audio bit
rates. PL1 offers the highest error protection and PL5 offers the lowest er-
ror protection.
Table 26.3.
DAB protection levels and mean code rates
Audio
bitrate
[kbit/s]
Mean code
rate
protection
level 1
Mean code
rate
protection
level 2
Mean code
rate
protection
level 3
Mean code
rate
protection
level 4
Mean code
rate
protection
level 5
32
0.34
0.41
0.50
0.57
0.75
48
0.35
0.43
0.51
0.62
0.75
56
X
0.40
0.50
0.60
0.72
64
0.34
0.41
0.50
0.57
0.75
80
0.36
0.43
0.52
0.58
0.75
96
0.35
0.43
0.51
0.62
0.75
112
X
0.40
0.50
0.60
0.72
128
0.34
0.41
0.50
0.57
0.75
160
0.36
0.43
0.52
0.58
0.75
192
0.35
0.43
0.51
0.62
0.75
224
0.36
0.40
0.50
0.60
0.72
256
0.34
0.41
0.50
0.57
0.75
320
X
0.43
X
0.58
0.75
384
0.35
X
0.51
X
0.75
Table 26.4. shows the minimum signal/noise ratio S/N needed and the
number of programs which can be accommodated in a multiplexed DAB
data stream on the basis of a data rate of 196 kbit/s per program, in de-
pendence on the protection level. If, e.g. PL3 is used, 6 programs of 196
kbit/s each can be accommodated in a multiplexed DAB data stream and
the minimum signal/noise ratio then needed is 11 dB. The gross data rate
of the DAB signal (including error protection) is 2.4 Mbit/s and the net
data rate is between (0.8) 1.2 and 1.7 Mbit/s depending on the error protec-
tion selected.
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