  The first purpose of this paper is to set up a general notion of skew power
series rings S over a coefficient ring R, which are then studied by filtered
ring techniques. The second subject consists of investigating the class of
S-modules which are finitely generated as R-module. In the case that S and R
are Auslander regular we show in particular that the codimension of M as
S-module is one higher than the codimension of M as R-module. Furthermore its
class in the Grothendieck group of S-modules of codimension at most one less
vanishes, which is in the spirit of the Gersten conjecture for commutative
regular local rings. Finally we apply these results to Iwasawa algebras of
p-adic Lie groups.
