Time Announcing Feature Recognition of Frequency Modulation Broadcast Signals Based on Hidden Markov Model

As whether it has the time signal in broadcasting or not is one of the important indicators to distinguish the legal radios from the illegal radios, this paper proposes a recognition method of the time announcing feature of the frequency modulation broadcast signals based on the Hidden Markov Model theory. With mute recognition algorithm, the time spectrum data of the frequency modulation broadcast is transformed as a 0-1 sequence, and the mute sequences are analyzed in 0-1 sequence, and hide states and observable states random sequences are final obtained. After the sub intervals are divided, initial hide states transformation matrix and observable states probability matrix are achieved. By learning hide states transformation and observable states probability matrixes based on Baum-Welch algorithm and training samples, Hidden Markov Model of the time telling and non-time telling of frequency modulation broadcast signals are established and the time announcing feature recognition algorithm is provided. The practical monitoring data of frequency modulation broadcast are utilized to perform the time announcing feature recognition experiment. The results indicate that the proposed method is capable of recognizing the FM broadcasting time announcing feature, and the average rate of recognition is equal to 87.5%. The proposed method has practical value in detecting the frequencies that are illegally occupied efficiently.