Digital Signal Processing Reference
In-Depth Information
where
bits_per_symbol
HP
= 2:
bits_per_symbol
LP
= 2 (16QAM) or 4 (64QAM);
code_rate
HP/LP
= 1/2, 2/3, 3/4, 5/6, 7/8;
guard_duration
= 1/4, 1/8, 1/16, 1/32;
channel
= 1 (8MHz), 7/8 (7MHz), 6/8 (6 MHz);
= 6.75 • 10
6
bits/s;
const1
Table 20.13.
Net data rates with non-hierarchical modulation in the 6 MHz
DVB-T Channel
Modulation
Code rate
Guard 1/4
Guard 1/8
Guard 1/16
Guard 1/32
Mbit/s
Mbit/s
Mbit/s
Mbit/s
QPSK
1/2
3.732353
4.147059
4.391003
4.524064
2/3
4.976471
5.529412
5.854671
6.032086
3/4
5.598529
6.220588
6.586505
6.786096
5/6
6.220588
6.911765
7.318339
7.540107
7/8
6.531618
7.257353
7.684256
7.917112
16QAM
1/2
7.464706
8.294118
8.782007
9.048128
2/3
9.952941
11.058824
11.709343
12.064171
3/4
11.197059
12.441177
13.173010
13.572193
5/6
12.441176
13.823529
14.636678
15.080214
7/8
13.063235
14.514706
15.368512
15.834225
64QAM
1/2
11.197059
12.441177
13.173010
13.572193
2/3
14.929412
16.588235
17.564014
18.096257
3/4
16.795588
18.661765
19.759516
20.358289
5/6
18.661765
20.735294
21.955017
22.620321
7/8
19.594853
21.772059
23.052768
23.751337
This brings us to the last details of the DVB-T standard related to actual
field experience: the constellation and the levels of the individual carriers.
Depending on the type of constellation (QPSK, 16QAM or 64QAM, hier-
archical with Α = 1, 2 or 4), a mean signal value of the payload carriers is
obtained which can be calculated simply by means of the quadratic mean
(RMS value) of all possible vector lengths in their correct distribution.
This mean is then defined as 100% or simply as One. In the case of the 2K
mode, there are 1512 or 6048 payload carriers, the mean power of which is
100% or One. The TPS carrier levels are set in the same way exactly in re-
lation to the individual payload carriers. The continual and scattered pilots
are differently arranged. Due to the need for easy detectability, these pilots
Search WWH ::
Custom Search