The DVB standard
identified the possible user data rates in the form of tables and will not be repeated here for sake
of conserving space.
In this OFDM system a guard time or interval is inserted into the transmit signal which consists
of a cyclic extension of the data. Each of the transmission modes has four guard interval time options.
For sake of discussion below we present the guard interval durations for the 5-MHz bandwidth (see
Table 9.2). The variety in the guard interval length allows for various deployment options.
Signaling information about the transmission scheme parameters such as channel coder, modulation,
frames number, etc., is sent by the Transmission Parameter Signaling (TPS) carriers. A TPS block
consists of 68 bits. Each OFDM symbol in the frame contains 1 TPS bit. The TPS block is protected
by a BCH code of (67, 53) with error correction capability t2 bits. Moreover, each TPC carrier uses
DBPSK modulation where due to the differential encoding it is initialized in each TPS block.
The coexistence of the DVB system with the cellular systems will become more and more desirable
from an end user perspective. In Fig. 9.13 we provide a simple example where the DVB-T and
DVB-H share a frequency BW allocation.
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