In this paper we present a review of some methods which intend to dimi
nish the complexity of the numerical treatment of integral equations a
rising in scattering phenomena. Indeed, it is a well-known point that
for integral equations discretized with classical finite elements the
complexity grows as the fourth power of the frequency. The methods rev
iewed here try to use a priori informations coming from asymptotic ana
lysis and to include them into the discretization.