Improved maximum likelihood classification for QAMs

This paper concerns modulation classification for quadrature amplitude modulation (QAM) formats. Based on a maximum likelihood classification scheme using amplitude information only, we propose a simplified algorithm that achieves computational efficiency at the cost of small performance degradation. A general performance analysis of the classification scheme (assuming perfect time synchronization) is presented next, which is able to deal with classification of any number of QAMs. Then we extend to consider asynchronous classification by incorporating blind time synchronization.