A new method for estimation of the amplitude distribution of signals

A hidden Markov model method for estimating an a posterior distribution of the amplitude of QAM communications signals is presented. As the signal to noise ratio decreases the hidden Markov model method is shown to perform significantly better than a conventional histogram method for characterising the amplitude distribution. The HMM estimation is performed within a expectation maximisation method in order to improve the estimates of the transition probabilities used in the HMM and the resulting estimated amplitude distribution.