Blind modulation classification: a concept whose time has come

We address the problem of identifying the modulation format of an incoming signal. We review many existing techniques for digital modulation recognition in a systematic way, which helps the reader to see the main features of each technique. The goal is to provide useful guidelines for choosing appropriate classification algorithms for different modulations, from the large pool of available techniques. Furthermore, the performance of a benchmark classifier is presented, as well as its sensitivity to several model mismatches. Open problems and possible directions for further research are briefly discussed