Terrestrial Transmission of Digital Television Signals (DVB-T) - Digital Video and Audio Broadcasting Technology - page 340

Table 20.1. Bit allocation of the TPS carriers

Symbol
number

Format Purpose/content

s 0 Initialization

s 1 - s 16 0011010111101110

or
1100101000010001

Synchronization word

s 17 - s 22 010 111 Length indicator

s 23 , s 24 Frame number

S 25 , s 26 Constellation

00=QPSK/01=16QAM/10=64QAM

S 27 , s 28 , s 29 Hierarchy information

000=Non hierarchical,
001=Α=1, 010=Α=2, 011=Α=4

S 30 , s 31 , s 32 Code rate, HP stream

000=1/2, 001=2/3, 010=3/4,
011=5/6, 100=7/8

s 33 , s 34 , s 35 Code rate, LP stream

000=1/2, 001=2/3, 010=3/4,
011=5/6, 100=7/8

s 36 , s 37 Guard interval

00=1/32, 01=1/16, 10=1/8, 11=1/4

s 38 , s 39 Transmission mode

00=2K, 01=8K

s 40 - s 53 all set to "0" Reserved for future use

s 54 - s 67 BCH code Error protection

In Fig. 20.3., the position of the pilots and TPS carriers can be seen
clearly in a 64QAM constellation diagram. The two outer points on the I
axis correspond to the positions of the continual pilots and the scattered pi-
lots. The two inner points on the I axis are the TPS carriers.
The position of the continual pilots and of the TPS carriers in the spec-
trum can be seen from the tables 20.2. and 20.3. In these tables, the carrier
numbers are listed at which the continual pilots and the TPS carriers can be
found. Counting begins at carrier number zero which is the first non-zero
carrier at the beginning of the channel.
The various types of carriers used in DVB-T are briefly summarized as
follows. Of the 2048 carriers in the 2K mode, only 1705 carriers are used
and all others are set to zero. Within these 1705 carriers there are 1512
payload carriers which can be QPSK, 16QAM or 64QAM modulated, 142
scattered pilots, 45 continual pilots and 17 TPS carriers.