“…In this study, in order to come up with optimal techniques for the solution of the considered problem, a statistical characterization of the received signal is utilized, and hence, related literature focusing on likelihood-based techniques are summarized in the following. In the context of likelihood-based modulation classification techniques, three prominent approaches are adopted based on how the unknown channel parameters and the transmitted symbol sequence are handled in the statistical model: the average likelihood ratio test (ALRT) [1], [2], [5], [8], [10], [15], [18], the generalized likelihood ratio test (GLRT) [1], [2], [5], [13], [17], [20] and the hybrid likelihood ratio test (HLRT) [1], [2], [5], [9], [10], [13], [14], [18], [21]. In the case of ALRT, all unknowns are treated as random variables with known prior distributions so that the likelihood expressions can be marginalized over the space of channel parameters and modulation symbols.…”