DRM – Digital Radio Mondiale - Digital Video and Audio Broadcasting Technology - page 520

In this context, cells are understood to be carriers allocated to various
uses. Control cells are used for transmitting the FAC and the SDC. Data
cells are used for transporting the MSC.
The pilot cells are simply the pilots already mentioned. Table 30.4.
shows how many CODFM symbols make up a transmission frame.

Table 30.4. Number of symbols N s per frame

Robustness mode Number of symbols N s per transmission

frame

A 15

B 15

C 20

D 24

At the beginning of a transmission super frame, the so-called SDC-
block is transmitted in symbol no. 0 and 1 in Mode A and B and in symbol
no. 0, 1 and 2 in Mode C and D. After that, only MSC and FAC cells are
transported until the beginning of the next super frame (Fig. 30.4.).
Pilot carriers or pilot cells are distributed over the entire range of
COFDM carriers. Depending on the mode, they are spaced apart by 20, 6,
4 or 3 carriers from one another and skip forward by 4, 2 or 1 carrier from
symbol to symbol.

Table 30.5. Pilot Carriers

Mode Pilot carrier spacing

in the symbol

Carrier skip distance
from symbol to symbol

A 20 4

B 6 2

C 4 2

D 3 1

30.5 Interference on the transmission link

DRM is operated in a frequency band in which atmospheric disturbances
and diurnal fluctuations of the transmission characteristics (ground and sky
wave) are particularly pronounced. In the frequency band below 30 MHz
there is mainly also the presence of man-made noise to be considered.
According to the standard, DRM has a bit error ratio of 1 • 10 6 in the
MSC after the channel decoder with a signal/noise ratio (S/N) of 14.9 dB
with 64QAM and a code rate of 0.6. In practice, the "fall off-the cliff“