  The problem of channel code design for the $M$-ary input AWGN channel with
additive $Q$-ary interference where the sequence of i.i.d. interference symbols
is known causally at the encoder is considered. The code design criterion at
high SNR is derived by defining a new distance measure between the input
symbols of the Shannon's \emph{associated} channel. For the case of
binary-input channel, i.e., M=2, it is shown that it is sufficient to use only
two (out of $2^Q$) input symbols of the \emph{associated} channel in the
encoding as far as the distance spectrum of code is concerned. This reduces the
problem of channel code design for the binary-input AWGN channel with known
interference at the encoder to design of binary codes for the binary symmetric
channel where the Hamming distance among codewords is the major factor in the
performance of the code.
