Study of SISO Superposition Coding Performance From Improper Discrete Signaling Perspective

A study of interference management in a Single-Input-Single-Output (SISO) two-user broadcast scenario by adjusting the circularity coefficient of discrete constellations is presented. Previously researched techniques for the same problem, namely the combination of PAM and QAM constellations, are reviewed as instances of the improper approach. The presented investigation further extends to the exploration of other combinations. Remarkably, all results presented in this letter are based on figures of merit of discrete constellations (mutual information, error probability, and minimum distance between symbols) rather than on formulas extrapolated from Gaussian signaling. Findings indicate that certain conclusions drawn previously for Improper Gaussian Signaling (IGS) in a similar setting hold for finite input constellations, though some vary.