Coded Orthogonal Frequency Division Multiplex (COFDM) - Digital Video and Audio Broadcasting Technology - page 313

speed, and in the case of DVB-T which is spreading in countries where it
is politically promoted and prescribed as an appropriate technology. If ap-
plied correctly, DAB and DVB-T make a good contribution to the conser-
vation of energy and frequencies whilst at the same time delivering better
performance.

Fig. 19.1. The terrestrial radio channel

19.1 Why MultiCarrier?

Multi-carrier methods belong to the most complicated transmission meth-
ods of all and are in no way inferior to the code division multiple access
(CDMA) methods. But why this complexity? The reason is simple: the
transmission medium is an extremely difficult medium (Fig. 19.1.) to deal
with.
The terrestrial transmission medium involves

• terrestrial transmission paths

• difficult line-associated transmission conditions

The terrestrial transmission paths, in particular, exhibit the following
characteristic features:

• Multipath reception via various echo paths caused by reflections

from buildings, mountains, trees, vehicles

• Additive white Gaussian noise (AWGN)