Method for focusing an electromagnetic or acoustic wave on a point near which one or more diffusers are placed, comprising a learning step in which the pulsed responses hij (t) between the focus point and each antenna (2) of the network are determined. Waves corresponding to signals Sji(t) = Si(t) ⊗ hij(-t), where Si(t) is a function of time and hij(-t) is a temporal inversion of the pulsed response hij(t), can then be transmitted from said antennas (2) of the network.