The inner interleaver consists of a bit and symbol interleaving operation for the 2K and 8K transmission
modes and has been extended to the 4K mode. As mentioned above there is an optional indepth
symbol interleaver for both the 2K and 4K modes in order to obtain better protection against
burst of errors. Specifically, the in-depth interleaver doubles the protection for the 4K mode and
quadruples the protection for the 2K mode.
The DVB system uses Orthogonal Frequency Division Multiplexing (OFDM) technology. Each
subcarrier in the OFDM transmission is modulated by Quaternary Phase Shift Keying (QPSK), 16-
QAM or 64-QAM. The DVB standard provides the technical details about the bit to symbol mapping
for the various constellations supported.
The transmitted signal consists of OFDM frames. Each frame has a duration of 68 OFDM symbols.
Each symbol is supported by a number of subcarriers, as shown in Table 9.1, for the different
transmission modes.
3G AND BEYOND DISCUSSION 489
MPEG TS
Outer RS
FEC
Scramble
Outer
Interleaver
Inner CC
FEC
MPEG TS
Outer RS
FEC
Scramble
Outer
Interleaver
Inner CC
FEC
Inner Interleaving
Symbol
Interleaver
Bit
Interleave Modulation
Frame
Adaptation
OFDM
Guard
Interval
RF
Section
FIGURE 9.
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