
1
Introductory concepts
1.1 Stochastic and deterministic signals, concepts of stationarity
and ergodicity
A signal is a physical quantity that can carry information. Physical and biological
signals may be classified as deterministic or stochastic. The stochastic signal con-
trary to the deterministic one cannot be described by a mathematical function. An
example of a deterministic signal may be the time course of a discharging capac-
ity or the position of a pendulum. Typical random process may be the number of
particles emitted by the radioactive source or the output of a noise generator. Phys-
iological signals can be qualified as stochastic signals, ...