Effect of Carrier offset on the Classification of Digital Modulation Signals Based on the Product of Two Consecutive Signal Values

In this paper we study the effect of carrier offset on a feature distinguishing different digital modulation signals. The feature is based on the multiplication of two consecutive signal values and the kurtosis of this multiplication. The feature distinguishes amplitude shift keying with two and four levels (ASK2 and ASK4), phase shift keying (PSK) and 16 signal constellation points quadrature amplitude modulation (QAM16). The paper compares the proposed feature to a cumulant based feature when both are used in a support vector machine classifier. Also the paper compares the proposed-feature based classification to the maximum likelihood classification.