Small noise is a good noise. In this work, we are interested in the
problems of estimation theory concerned with observations of the
diffusion-type process Xo = Xo, 0 t T, (0. 1) where W is a standard
Wiener process and St(') is some nonanticipative smooth t function. By
the observations X = {X, 0 t T} of this process, we will solve some t of
the problems of identification, both parametric and nonparametric. If
the trend S(-) is known up to the value of some finite-dimensional
parameter St(X) = St((}, X), where (} E e c Rd, then we have a
parametric case. The nonparametric problems arise if we know only the
degree of smoothness of the function St(X), 0 t T with respect to time
t. It is supposed that the diffusion coefficient c is always known. In
the parametric case, we describe the asymptotical properties of maximum
likelihood (MLE), Bayes (BE) and minimum distance (MDE) estimators as c
--+ 0 and in the nonparametric situation, we investigate some
kernel-type estimators of unknown functions (say, StO, O t T). The
asymptotic in such problems of estimation for this scheme of
observations was usually considered as T --+ 00, because this limit is a
direct analog to the traditional limit (n --+ 00) in the classical
mathematical statistics of i. i. d. observations. The limit c --+ 0 in
(0. 1) is interesting for the following reasons.