  The detection problem in the Gaussian interference channel is addressed, when
transmitters employ non-Gaussian schemes designed for the single-user Gaussian
channel. A structure consisting of a separate symbol-by-symbol detector and a
hard decoder is considered. Given this structure, an optimal detector is
presented that is compared to an interferenceunaware conventional detector, an
interference-aware successive interference cancellation (SIC) detector, and a
minimum-distance detector. It is demonstrated analytically and by simulation
that the optimal detector outperforms both the conventional and the SIC
detector, and that it attains decreasing symbol error rates even in the
presence of strong interference. Moreover, the minimum-distance detector
performs almost as well as the optimal detector in most scenarios and is
significantly less complex.
