  For a state-dependent DMC with input alphabet $\mathcal{X}$ and state
alphabet $\mathcal{S}$ where the i.i.d. state sequence is known causally at the
transmitter, it is shown that by using at most
$|\mathcal{X}||\mathcal{S}|-|\mathcal{S}|+1$ out of
$|\mathcal{X}|^{|\mathcal{S}|}$ input symbols of the Shannon's
\emph{associated} channel, the capacity is achievable. As an example of
state-dependent channels with side information at the transmitter, $M$-ary
signal transmission over AWGN channel with additive $Q$-ary interference where
the sequence of i.i.d. interference symbols is known causally at the
transmitter is considered. For the special case where the Gaussian noise power
is zero, a sufficient condition, which is independent of interference, is given
for the capacity to be $\log_2 M$ bits per channel use. The problem of
maximization of the transmission rate under the constraint that the channel
input given any current interference symbol is uniformly distributed over the
channel input alphabet is investigated. For this setting, the general structure
of a communication system with optimal precoding is proposed.
