DMB-T and T-DMB - Digital Video and Audio Broadcasting Technology - page 506

PN sequency (Fig. 28.1.). This symbol-preamble is called frame header
and has a length of 56.6 µs, 78.7 µs or 125 µs at a channel bandwidth of 8
MHz. In 4K-mode, DMB-T runs with 3780 occupied carriers (Fig. 28.3.)
spaced apart at 3 kHz in an 8 MHz channel. The symbol period is,
therefore, 500 µs. 3744 of these 3780 carriers are modulated data carriers
and 36 are signalling carriers, i.e. TPS carriers. DMB-T supports channel
bandwidths of 8, 7 and 6 MHz (Fig. 28.3). The useful spectrum has a
width of 7.56 MHz in the 8 MHz-channel. The net-data rate is in the range
of between 4.813 Mbit/s and 32.486 Mbit/s. The spectrum is roll-off-
filtered with a roll-off-factor of r=0.05 (Fig. 28.4.). The transmission
method is designed for SDTV- and HDTV-transmissions and is intended
to function both in stationary and in mobile modes of operation. It is pos-
sible to implement both MFN and SFN networks.

TS
in

Data
out

Fig. 28.2. DMB-T: forward error correction (FEC)

4K mode:
3780 carriers
f=2 k Hz

f

f

Channel bandwidth

6, 7, 8 MHz

Fig. 28.3. DMB-T channel